rr878 - levels of respirable dust and respirable crystalline silica at

Health and Safety Executive

Levels of respirable dust and respirable crystalline silica at construction sites

Prepared by the Health and Safety Laboratory for the Health and Safety Executive 2011

RR878 Research Report



Peter Stacey, Andrew Thorpe & Paul Roberts Harpur Hill Buxton Derbyshire SK17 9JN

The purpose of this pilot study was to assess the potential for inadvertent exposure of the public to respirable crystalline silica (RCS) from construction activities.

The study assessed the respirable dust (RD) from, demolition, block cutting, road building, general construction activities and city centre air from 13 visits to 7 sites. In total, 48 samples from the construction activities and 11 city centre air samples, for comparison, were collected.

The results obtained for RD and RCS were generally very low. Only 10 % of results (from two sites) for RCS were above 0.01 mg.m-3, which is 10 % of the current Workplace Exposure Limit (WEL) for RCS. The majority of visits showed evidence of some transport of RCS across the site and potentially into public areas. The main crystalline components of the city centre air sample were generally the same as the components of the samples taken at the construction sites.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.

HSE Books

© Crown copyright 2011

First published 2011

You may reuse this information (not including logos) free of charge in any format or medium, under the terms of the Open Government Licence. To view the licence visit www.nationalarchives.gov.uk/doc/open-government-licence/, write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email [email protected].

Some images and illustrations may not be owned by the Crown so cannot be reproduced without permission of the copyright owner. Enquiries should be sent to [email protected].

ACKNOWLEDGEMENTS:

Special thanks are given to Mr David Bradley (HSE), Ms Jan Foers (HSE) Ms Carol Southerd (HSE) the Sheffield Area Office who helped identify several of the sites for this report. Dr Colin Davy (HSE) is thanked for his support for this project and Dr Dave Mark for his helpful suggestions. Mr Andrew Thorpe (HSL) is thanked for this work in calibrating the samplers and ensuring the pumps worked for a full 8 hours. Mr Paul Roberts (HSL) is thanked for his support and work on the site visits. Thanks are also given to the many local authorities helped with this work and the companies for their cooperation by providing safe access to the sites and facilities.

Company names are not mentioned in the report to preserve their confidentiality.

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CONTENTS

1 INTRODUCTION......................................................................................... 1 1.1 Respirable dust........................................................................................ 2 1.2 Previous evidence ................................................................................... 2

2 AIR SAMPLING STRATEGY...................................................................... 3 2.1 The equipment......................................................................................... 3 2.2 Calibration of sampler for the respirable fraction ..................................... 3 2.3 Variability of the five samplers ................................................................. 5 2.4 Monitoring strategy .................................................................................. 5

3 ANALYSIS STRATEGY.............................................................................. 7 3.1 Gravimetric analysis for respirable dust................................................... 7 3.2 RCS analysis method for ambient samples ............................................. 7

4 DESCRIPTION OF CONSTRUCTION SITES AND RESULTS ................ 10 4.1 Site 1: General Construction Activities................................................... 10 4.2 Site 2: Demolition .................................................................................. 13 4.3 Site 3: City Centre ring road Construction ............................................. 18 4.4 Site 4: Street block cutting ..................................................................... 23 4.5 Site 5: Street block cutting ..................................................................... 25 4.6 Site 6: Rubble Clearance from Demolition............................................. 27 4.7 Site 7: Demolition of College ................................................................. 30

5 COMPARISON WITH TEOM MEASUREMENTS..................................... 34

6 CRYSTALLINE COMPONENTS OF URBAN AIR ................................... 35

7 DISCUSSION............................................................................................ 38 7.1 Summary of results................................................................................ 38 7.2 Respirable Dust ..................................................................................... 39 7.3 Weight of dust recovered from ashing ................................................... 40 7.4 Respirable Crystalline Silica .................................................................. 40 7.5 Transport of dust across the sites.......................................................... 41

8 CONCLUSIONS........................................................................................ 44

9 REFERENCES.......................................................................................... 46

10 APPENDICES 1: XRD CALIBRATIONS............................................... 48

11 APPENDIX 2 ......................................................................................... 49 11.1 Site 1 Construction ................................................................................ 49 11.2 Site 2 Demolition ................................................................................... 51 11.3 Site 3: Ring road construction................................................................ 55 11.4 site 4: Block cutting................................................................................ 60 11.5 Site 5: Block Cutting .............................................................................. 63 11.6 Site 6: Rubble Clearance....................................................................... 64

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11.7 Site 7: Demolition .................................................................................. 66

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EXECUTIVE SUMMARY

Objectives

This work was a study to estimate inadvertent exposure of people to resiprable dust and respirable crystalline silica (RCS) from construction activities in the urban environment.

Main Findings HSE holds much information about construction sites, however the detail of the information was not sufficient to allow it to be used to identify sites for this type of project, where such a specific activity is evaluated.

All operators at the sites were employing what they perceived as 'best' health and safety practice. It was noted that some controls, such as a hand pressurised water containers, do not work continuously because there is no indicator to signify when pressure is low. The intermittent effectiveness of these controls may increase worker exposure, but this was not confirmed by this study.

The air concentrations for respirable dust obtained using the HSL sampler conforming to the occupational hygiene sampling convention were comparable with the results obtained by the local authority or UK air-monitoring network Tapered Element Oscillating Microbalance (TEOM) site measuring the environmental health related fraction PM10 (uncorrected by the factor 1.3). The regression coefficient (r2) excluding extreme values was 0.92.

The main crystalline components of urban air samples are quartz (SiO2), calcite (CaCO3), halite (NaCl), anhydrite (CaSO4) and/or calcium sulphate hydrate (CaSO40.5H2O). Some urban air samples also showed peaks that indicated the presence of clays (illite and kaolinite) and probably hematite (Fe2O3). Many of the samples after ashing in a plasma-asher were orange in colour, which may confirm the presence of the hematite or another iron oxide.

Generally, the crystalline components on site mirrored the components in the urban air. This may indicate that construction activities, the natural geology, or dust from buildings in the area contribute to the mineral composition of an urban air sample. Samples from larger demolition sites also indicated the presence of some calcium silicates common to concretes and portlandite (Ca(OH)2).

On average, the majority of the sample (by mass) from the urban air, general construction activities and road building operations was combustible or volatile (57 – 73 %). indicating it was probably mostly pollen or diesel fume. The samples from block cutting and demolition activities were mostly non-combustible/non-volatile material (53 – 58%). Indicating a higher mineral content and therefore associated with the activity being monitored.

Overall, about 20 % of results (for an 8 – hour sample) exceeded the ambient UK air quality value for PM10 of 50 µg.m-3.

Despite dust controls, large-scale demolition projects, with excavators, have the potential to produce air concentrations of respirable dust in excess of 50 µg.m-3 (Maximum 226 µg.m-3). This is probably because the contractors find it difficult to introduce effective and consistent dust controls because of the scale of the task.

The results for RCS and respirable dust were generally low for all the activities. Several samples from monitoring block cutting and demolition also obtained results for RCS in excess of 10 µg.m-3, which was probably due to inconsistent suppression of dust by the control. Despite the controls and practices employed by workers cutting blocks and bricks with cut-off saws, a

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couple of results from samplers (about 5 m from the activity) obtained results in excess of 10 µg.m-3. This may indicate that the controls used with cut-off saws are not meeting the requirements for effective suppression of dust specified in A Thorpe et al (1999).

Most sites (9 in 11 sites with reasonable data) showed evidence of the transport of RCS across the site to boundary and potentially into public areas.

RCS was identified in some of the urban air samples, although in most samples only one of the three peaks used for quantification was present. The estimated range of values for RCS from the urban air samplers was 0.1 – 0.44 µg.m-3 and the maximum proportion of RCS in the respirable dust is estimated as 2 %.

Summary

The air concentration values for RCS at the boundary of construction sites are low and rarely exceed 1/10 th of the current workplace exposure limit of 0.1 mg.m-3 (100 µg.m-3). This level of exposure to RCS would only make a significant contribution to a worker’s exposure if the WEL were lowered to 50 µg.m-3. It is likely that an individual, living in very close proximity (< 50 m) to a very large scale demolition, may obtain a measurable but very low exposure to RCS, however, demolition activities of short duration should not have a significant impact on their health since this is dependent on a long term exposure (approximately 15 – 20 years).

Recommendations

This was a small study to ascertain if levels of respirable dust and RCS at site boundaries are potentially significant, so the recommendations are limited, because they are based on small numbers of data.

The results from this study indicate that dust control may still be poor with very large-scale demolition activities and that this area may warrant further investigation. It is proposed to discus these results with other researchers in the Building Research Establishment (BRE).

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1 INTRODUCTION

Inhalation of respirable crystalline silica (RCS) is known to cause a disease called silicosis and cancer and it is thought to contribute to a condition known as chronic obstructive pulmonary disease (COPD). Workers exposed to RCS are one of the largest groups of workers at risk from exposure to a hazardous substance. In 1992 there were estimated to be about 100,000 workers potentially exposed to RCS. In 2006, the workplace exposure limit (WEL) for RCS was reduced to 100 µg.m-3 and there is pressure to lower it further to 50 µg.m-3 as epidemiological data suggest there is no known level of exposure at which silicosis does not occur. On agreeing the reduced WEL in 2006, the HSC tasked its Advisory Committee on Toxic Substances (ACTS) to review the measurement issues that precluded any further reduction of the WEL at that time, with a view to reducing the WEL further once they had been resolved. As exposure limits are lowered it becomes increasing important to understand if the background levels of RCS in air contribute to an individual’s personal exposure and very little information existed on background levels at the time of the publication of this report.

There is concern over the issue of exposure of people, to respirable dust (RD) and RCS, when they are close to but not involved in work activities, e.g. people living close by or workers involved in other activities that do not generate RCS. Work activities; such as those to maintain services, roadways and buildings, generate respirable crystalline silica (RCS). In addition, many major construction activities take place in cities and most construction activities involve working with materials containing crystalline silica. It is possible, if the WEL is reduced to 50 µg.m-3 or below, that some peak emissions from sources other than the immediate work activity may significantly contribute to an individual's exposure. Recent papers E Bontempi et al (2008) and V Esteve et al. (1997) have shown that RCS is a potentially significant proportion of the crystalline content of an environmental air sample. Whilst we are able to estimate the exposure to RCS of an individual at work from past data, little is known about the inadvertent exposure of people who are close to but not involved in the work activity. Local authorities do not measure respirable dust (RD) to the same specification that is used for occupational hygiene measurements or RCS and little information exists in literature.

This pilot study conducted 13 visits to 7 sites, which sampled the activities listed in Table 1 to assess the potential exposure of people to respirable dusts and RCS emitted from construction activities.

Table 1: Work tasks sampled Work Tasks Number of visits General construction 2 Demolition 7 Block cutting 2 Road building 2

The types of work are slightly biased towards demolition sites. This is partially due to the limited availability of information about the work activities and poor reliability of the starting dates for tasks potentially generating silica dust within a particular project. The more specialist demolition companies provided an effective liaison for this specific activity. The majority of the work in this report took place in 2009, during which an economic crisis prevented many projects from progressing. Heavy rain during the year also hampered the available sampling opportunities, since the equipment could not be used. The rainfall in the United Kingdom over the summer months of June, July and August was 140% more than the long-term average for the years 1971 – 2000 (Met Office 2009)

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1.1

1.2

RESPIRABLE DUST

The particle size fractions sampled in environmental science are different from those sampled for occupational hygiene work. The target specification for instruments sampling the respirable fraction for occupational hygiene purposes is specified in EN481 (1993) and is based on sampling a distribution of particles (approximately < 10 µm) with a median diameter of 4.3 µm, whilst the environmental fractions have are based on particle distributions with median diameters of 10 µm (PM10) and 2.5µm (PM2.5). The relationship between the three different dust fractions is shown in Figure 1.

Figure 1 Definitions of particle size dust fractions

PREVIOUS EVIDENCE

The limited information about the ambient levels of respirable dust and RCS, was reviewed by Mark et al (2009). Mentioned in the review is the work of Moore (1999) who estimated that about 10 % of a background ambient dust concentration of 40 µg.m-3 could be crystalline silica (CS), although it is likely that the particle size distribution of the dust referred to in the paper by Moore is total suspended particulate (TSP) and that the respirable dust levels could be lower. More recently a report examining the mineral dust in urban air of Beijing (Whitaker 2003) also estimated the concentration of quartz in air as 10 % on one of its samples, although this city is known for its experience of dust storms. Shiraki and Holmen (2002) examined the crystalline silica content in PM 10 samples close to crushing and screening plants of a sand and gravel facility in California. This work obtained CS levels of about 60 µg.m-3 near the work activity and levels of 5 µg.m-3 1000 m upwind of the site and ~ 9 µg.m-3 down wind of the site. In addition to the documents mentioned by Mark et al (2009) the World health Organisation has published a review (Rice 2000) concerning the health effects of the respirable quartz which refers to work by Davis et al (1984) where the results for the quantification of CS from a single PM 10 sample range from 0 to 15.8 µg.m-3. In the most recent work by Mark et al (2009) examining the ambient RCS levels in levels in five quarries only 5 out of 120 (4%) of measurements were above 10 µg.m-3, the highest was approximately 21 µg.m-3. This study examines the ambient levels of RD and RCS around a number of construction sites where potentially dusty activities were taking place.

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2.1

2 AIR SAMPLING STRATEGY

THE EQUIPMENT

This project used the samplers developed for the HSE survey of quarries and is described in detail in Mark et al (2009) (Figure 2). These samplers had a flow rate of 52 litres/minute and would sample for a working period of approximately 7 – 8 hours at each site. Air is sampled through louvered plates and size selective inlet onto a 60 mm diameter mixed cellulose ester (MCE) filter with a 2 µm pore size. Selection of the respirable fraction on the filter was achieved using a 10 mm thick layer of 45 ppi (pores per inch) foam and a single 10 mm layer of 60 ppi foam. The 60 ppi foam placed on top of the 45 ppi foam in the sampling was separated from the foams by a course metal grid. Rotheroe and Mitchell L60 rotary vane sampling pumps provide the flow rate. They were originally supplied to the HSL Occupational Hygiene Unit and were surplus to requirements. Batteries were used because it is difficult to obtain mains supply. Initially, two 12v high capacity lead acid leisure batteries were used to power the pump through a 12v dc to 240v power converter. However, in the initial phase of this project the batteries failed to run for the full time in laboratory conditions. The run time of the apparatus was improved through the purchase of new batteries and by adapting the boxes to fit three in parallel. The sampling flow was monitored with an in line rotameter on the outside of the enclosure that was marked indicating the specified flow rate. Restricting the diameter of the exhaust tubing with a clip controlled the flow rate through the filter. The rotameter was calibrated by checking the air flowing through the sampler entry with a calibrated gas meter.

.

Figure 2 A high volume sampler for ambient respirable dust

2.2 CALIBRATION OF SAMPLER FOR THE RESPIRABLE FRACTION

2.2.1 Sampling efficiency

It was necessary to recheck the performance of the foams used for size selection because a year had passed since the system was last used and new foams were purchased. This was carried out using the calm air dust chamber, which is the standard apparatus used in HSL for determining

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the size selective performance of sampling apparatus (Kenny and Liden 1991). Two identical inlets, one with the size selective foam and the other empty, sample aerosols of glass spheres with a known particle size distribution. The glass sphere particles penetrating the inlets are themselves sampled by an Aerodynamic Particle Sizer (APS), which gives a number based aerodynamic size distribution. By comparing the size distributions in the inlet with and without the foams, the size selective performance of the foam as a respirable size selector can be determined. The results are given in Figure 3.

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 2 4 6 8 10 12 14

Aerodynamic diameter (µm)

Frac

tiona

l pen

etra

tion

Foam Penetration CEN 481 (respirable)

Figure 3 Penetration curve 45ppi 20mm thick & 60ppi 10mm thick porous foam

It can be seen that the performance of the size selective foam is close to the target respirable convention (EN 481, 1993). However, Figure 3 also suggests that this sampler may slightly under sample the larger particle sizes (> 6µm) within the respirable size range, which is important for XRD analysis since smaller particles are less crystalline and contribute less signal/mass to the measurement. The mass median aerodynamic diameter (D50) from this work is 4.35 µm compared with 4.44 µm in the previous work reported by Mark et al (2009). The difference between the sampling of the foam for respirable dust and the ideal respirable dust sampler conforming to EN 481 is described in Table 2.

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Table 2: Difference of foam selector from the ideal respirable dust sampler Mass Median Aerodynamic

Diameter (MMAD) µm Geometric Size Standard Deviation (GSTDEV) µm

Difference (%)

5 2 6.21 5 3 4.54

10 2 -0.95 10 3 4.36 20 2 -9.61 20 3 3.59 30 2 -17.30 30 3 2.66 40 2 -23.84 40 3 1.70

Note: The MMAD and GSTDEV are the mass median aerodynamic diameter and geometric standard deviation of different aerosols that the sampler is expected to encounter.

Most differences are less than 10 %, except from some aerosols with a MMAD greater than 30 µm.

2.3 VARIABILITY OF THE FIVE SAMPLERS

The five samplers were placed together in a laboratory space and run for 27 hours. Gravimetric analysis of the filters showed a precision of ± 5 % from an average mass of 400 µg. The air concentration of respirable dust collected was about 5 µg.m-3.

2.4 MONITORING STRATEGY

Five samplers were available for each site. Where space allowed, three samplers were placed down wind of the site and one up wind. The fifth sampler was located in HSL’s mobile laboratory and was placed in a convenient position near the centre of the closest major urban conurbation close to sites unaffected by construction activities. The fifth sampler provided the samples identified as ‘urban air’ and would be used to determine a range of levels of respirable dust in the ‘urban air’ unaffected by the construction sites and to compare the respirable dust results obtained with HSL sampler with the PM10 values obtained by the local authority to assess any differences. When possible the sampler was located next to the local authority’s or the national UK air-monitoring site for PM10, in order to gain a comparative result and to determine the level of RD and RCS in area on the day of sampling. The skylight in the mobile laboratory was adapted to fit a spike for the sampling head (Figure 4). A 2 m air tube then linked the sampling head with the pump below. Information about the temperature, pressure, humidity and prevailing wind direction at the site was obtained with a Davis Vantage pro 2 weather station. At most sites, measurements of the weather conditions were taken every hour.

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HSL’s Sampling inet

PM 10 sampler inlet

Figure 4 The mobile laboratory with sampler in position next to a local authority PM10 site

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3 ANALYSIS STRATEGY

3.1 GRAVIMETRIC ANALYSIS FOR RESPIRABLE DUST

The 60 mm mixed cellulose ester (MCE) filters were weighted in a balance room, controlled to maintain its humidity at 50 ± 5% and its temperature to 20 ± 4°C. The filters were conditioned in the balance room overnight and weighed on a Mettler balance with a readability of 10 µg.

The non-combustible/volatile fraction of the dust was weighed, after removing the filter by burning or plasma ashing, on polycarbonate or silver filters, using a Sartorius balance with a readability of 1 µg.

3.2 RCS ANALYSIS METHOD FOR AMBIENT SAMPLES

Previous work (Mark 2009) describes the development of a method employed for the analysis of RCS. This analytical method involves the removal of the dust collected on the 60 mm diameter MCE filter and depositing it onto filters of 25 mm diameter for analysis by X-ray diffraction (XRD). In this work the calibration and sample preparation procedures described by the National Institute of Safety and Health in their method 7500 (NIOSH 2003) were adopted. An EMITECH KIO50X plasma asher was used to remove the air sample filter and the inorganic dust remaining was filtered onto 0.45 µm pore size polycarbonate filters, to allow the opportunity of preparing these samples for analysis by scanning electron microscopy (SEM).

3.2.1 XRD instrument specification

The samples were analysed by XRD using the following specifications optimised for intensity rather than resolution.

• A Panalytical X-pert pro MPD X-ray diffractometer operating with Bragg-Brento semi-focusing geometry

• A broad focus tube with copper target operating at 55Kv and 49 mA to give a power output of 2.7 watts

• Automatic divergence and antiscatter slits set at 18mm

• Spinner set at 1 revolution per second

• Automatic sample changer

• Array detector set on continuous scan mode with a window area of 2.12 degrees.

The 100 reflection at 20.9 degrees 2θ (secondary peak with 25 % intensity), the 101 reflection at 26.6 degrees 2θ (primary peak with 100% intensity) and the tertiary 112 reflection at 50.1 degrees 2θ were calibrated for measurement using Xpert Industry programme and the scan parameters detailed in Table 3.

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Table 3: Scan parameters

Angle (2θ) Scan range Step size Counts per step (seconds)

20.9 19.9 – 21.9 0.05 600

26.6 25.65 – 27.65 0.05 420

50.1 49.1 – 51.1 0.05 600

3.2.2 Calibration procedure

Calibration samples were prepared over the analytical range 10 – 500 µg following the procedure in NIOSH method 7500 (NIOSH 2004). Aliquots from two suspensions, one with 10 mg and one with 50 mg of the HSE quartz standard A9950 in one litre of 2-isopropanol were filtered onto filters using a Millipore filtration apparatus and a filter funnel with an inner diameter of 15 mm. This diameter of filter funnel would ensure that all the silica would be completely within the analysis beam of the instrument. The calibration is shown in Appendix 1.

3.2.3 Sample preparation and recovery tests

The filters were carefully placed into glass bottles which were then put in a plasma asher. The filters were ashed under air for 12 hours in a plasma generator using a radio frequency (RF) power setting 49 of and then for 4 hours under oxygen with an RF power setting of 95. A small amount of 2-isopropanol was then added to the bottle, the bottle was then sealed and ultrasound for about 5 minutes. The contents of the bottle were then washed onto a onto a 25 mm diameter, 0.4 µm pore size, polycarbonate filter, using the same apparatus involved in the preparation of the calibration samples. The recovery from the plasma ashing process was determined by loading 5 filters with 65 µg of the quartz calibration material A9950, using a aliquot of 5 mL from a suspension of 13 mg of A9950 in 1 litre of 2-isopropanol. The mass of 65 µg was selected because it was a good challenge as it is a relatively small mass at the lower end of the range of expected values and the changes in weigh are more significant. The samples were analysed gravimetrically and by XRD. The manufactures of the plasma ashing apparatus quote a residue of 0.1 %. The average weight of a filter before ashing was 7.76 mg so the expected increase in weighs due to residue from the filters is about 7.8 µg. The results of the recovery tests are shown in Table 4.

Table 4: Recovery Tests Technique Gravimetric Analysis X-ray Diffraction Analysis Filter Mass (µg) Recovered

(µg) Quartz Result (µg) Pre ashing

Quartz Result (µg) Post ashing

1 95.17 98.00 71.40 67.24 2 76.00 90.50 75.16 65.10 3 74.83 89.50 69.39 66.18 4 85.67 97.00 66.90 5 83.17 91.00 71.00

Average 82.97 93.20 71.98 67.28 Standard Deviation 8.23 3.98 2.93 2.24

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We were not able to measure two of the samples by XRD before ashing because the filters had lost their shape (flatness) and obtained slight damage. The average gravimetric results show an increase in mass, which is only 2µg more than the expected residue from the filters alone indicating a complete recovery of the sample. The average XRD results show a slight decrease of 4.7 µg (6.5 %), which slightly statistically significant from the limited data included in the study (two sided t test probability assuming equal variances p = 0.041), although within the expected precision of the XRD technique of approximately ± 10 % (1σ) (Stacey et al 2003). These XRD data indicate an almost complete recovery, which in the worst case is between 89 – 96 % (2σ).

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4 DESCRIPTION OF CONSTRUCTION SITES AND RESULTS

4.1 SITE 1: GENERAL CONSTRUCTION ACTIVITIES

4.1.1 Location

The first site involved the construction of offices and class rooms for a college of education a couple of miles from the centre of a major city in the Yorkshire area. Effectively the college was being rebuilt whilst the old buildings were still in use, so the distance between work and public areas was small (<2 m).

4.1.2 Work activities

Work activities observed on the site whilst sampling were, kerb cutting on a couple of occasions on both days, movement of sand near sampler 1 on the first day for about hour, excavation in the morning of day 2 and the making of concrete at various times throughout the exercise. The position of the activities in relation to the samplers is described in the table in 4.1.6. The major source of potential dust was from the single access road that ran along the back of the site, which occurred sporadically during the day. The control of traffic movement along this road was a potential hazard because the route was narrow and allowed little room for traffic to manoeuvre. Some brick laying was undertaken in the concrete tower block but this was some distance from the samplers. Pictures of the work activities observed are shown in Appendix 2.

4.1.3 Dust controls

No specific dust controls were observed at the site although few activities generating significant dust were noticed. The visit to this site occurred before the operational circular SIM 02/2009/01 (HSE, 2008) for controls kerb, pavement and block cutting was released.

4.1.4 Weather

Day 1

Showers started when putting the equipment in place but the ground appeared to dry during the day. The humidity ranged from 58 – 82 % and the temperature from 7.7 – 15.7 °C. The median wind direction was from the west (266.50). Unfortunately, wind speed data was not collected at this site.

Day 2

The day was generally damp with bright spells. There were rain showers in the middle of the day. The humidity ranged from 53-76 % and the temperature from 8.6 – 12 °C. The median wind direction was from the west (2680). Unfortunately, wind speed data was not collected at this site.

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4.1.5 Location of samplers

Wind Direction For Site 1 Day 1

360 20

40 60

80

100 120

140 160

180 200

220 240

260

280 300

320 340

Wind Direction For Site 1 Day 2

360 20

40 60

80

100

120 140

160 180

200 220

240

260

280

300 320

340

The shaded areas in the charts for wind direction indicate the direction the wind arrives on site. In these charts the samplers labelled 1,2 and 3 are measuring the dust leaving the site.

Boundary of work areas are indicated as

The plan is orientated so that north is towards the top.

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4.1.6 Results Table 5: Results for site 1

Day 1

Position on the map

Tasks Respirable Dust

(µg/m3)

Non combustable fraction (µg/m3)

Respirable Crystalline Silica (RCS) (µg/m3)

Percent RCS in respirable fraction

1 Adjacent access road and nearest sand movement

28.4 10.2 0.22 0.8 %

2 Opposite tower block brick laying and cement mixer

24.9 11.4 0.39 1.6 %

3 Outside gate traffic movements

19.0 4.7 0.17 1%

4 In flow from city 17.9 6.5 0.20 1%

Urban Air

Car park within 5 –6 m of a busy road

17.4 7.1 0.17 1%

*The PM10 concentration from the TEOM Site in the city centre was 17.2 µg.m-3.

Day 2

Position on the map

Tasks Respirable Dust

(µg/m3)




1 Adjacent access road for traffic movement

28.9 9.02 0.23 0.8 %

2 Opposite tower block and cement mixer

29.5 11.6 0.25 0.8 %

3 Outside gate near excavation

23.3 7.58 0.13 0.6 %

4b North of kerb cutting

22.7 6.07 0.08 < 0.1 %

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4.2

Urban Air

Car park within 5 –6 m of a busy road

27.7 4.69 0.08 < 0.1 %

*The PM10 concentration from a TEOM Site in the city centre was 22.3 µg.m-3

*Result from UK air monitoring network TEOM PM10 site managed by the local authority (result is not corrected by the compensating factor 1.3). The results from PM10 TEOM samplers are often multiplied by a factor of 1.3 to make the values comparable with gravimetric analyses. It is though that some TEOM samplers may under sample PM10.

A single blank sample recorded a residue, after combustion, of 36 µg, which translates to an potential air concentration of between 1.4 to 1.8 µ/m3 for the mid range of air volumes sampled (between 20 – 26 m3).

SITE 2: DEMOLITION

4.2.1 Location

This site involved the demolition of a water tower and boiler house in the grounds of a hospital with a single JCB excavator. Sampling was focused on this activity.

4.2.2 Work activities

The site was visited over a four-day period. The work activities and their approximate duration are shown in table 6.

Table 6: Work Activities at Site 2

Day Activities Approximate Duration

(hours)

1 No activity – work postponed

2 Excavator removing debris to skip (work stopped due to the discovery of asbestos lagging)

2

General activities (not potentially dust generating)

Some demolition work inside the building

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3 Demolition of water tower with excavator with extended arm 8

4 Working to change hydraulic arm on excavator 4

Rubble/pipe movement/ demolition work 3

Photographs of the activities are in Appendix 2. The demolition started in position D and worked along the building. The water tower was north of position 4.

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4.2.3 Dust controls

A worker doused falling rubble with water from a hosepipe. Hoses attached to the end of a long grappling arm of the excavator, supplied from the reservoir of an old fire engine, sprayed top of the tower with a fine mist of water.

4.2.4 Weather

The following conditions were observed from observations taken every hour of sampling during the working period.

Day 2:

The day was generally dry and sunny. The average temperature recorded on that day was 18.6 °C and the humidity was 68 %. The wind direction was generally from the southwest, although the wind speed ranged from 0 to 4 m/s with a median value of 0.4 m/s.

Day 3

The day was cloudy and it rained in the afternoon. The median temperature was 13 °C and the median humidity was 82 %. The wind was generally from the east with a speed ranging from 0 to 1.3 m/s. The most frequently recorded value for wind speed was zero.

Day 4.

The day was cloudy with some rain in the afternoon. The average temperature was 11 °C and the median humidity was 69 %. The wind was from the west and its speed ranged from 0 – 5 m/s with a median value of 0.65 m/s.

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D

Boundary of work areas are indicated as

The plan is orientated so that north is towards the top

The samplers identified by the circles were used on day 2 and those identified by the squares on days 3 and 4.

15

4.2.6 Wind Direction

Wind Direction Day 2 360

20 40

60

80

100

120

140 160

180 200

220

240

260

280

300

320 340

Wind Direction Day 3

360 20

40

60

80

100

120

140

160 180

200

220

240

260

280

300

320

340


360 20

40

60

80

100

120

140 160

180 200

220

240

260

280

300

320 340

The shaded areas on the wind roses indicate the direction the wind is from.

On day 2 the sampler in position 1 was upwind and the samplers in position 2,3, and 4 were downwind.

On day 3 the sampler in position 3 is upwind and sampler 5 is down wind. Sampler 6 is close to the work activity but slightly upwind.

On day 4 the sampler in position 5 is upwind and 3 and 6 are down wind

16

4.2.7 Results

Table 7: Results for site 2

Day 2

Position on the map

Task Respirable Dust

(µg/m3)




1 Up wind sampler 39.0 4.7 0.51 1.3 %

2 South of demolition at the fence

46.0 6.51 0.63 1.4 %

3 Down wind behind JCB demolition area at the fence

57.0 6.38 0.32 0.6 %

4 Near the tower – upwind of demolition

39.3 8.12 0.18 0.5 %

Urban Air Car park within 5 –6 m of a busy road

34.4 5.43 0.23 0.7 %


Day 3

Position on the map

Task Respirable Dust

(µg/m3)




6 Slightly north of JCB activity

30.0 9.74 0.5 1.6 %

5 Down wind behind gates west < 10m from tower

73.6 33.6 2.25 3 %

3 Upwind sampler 24.1 6.4 0.4 1.6 %

Urban Air Road Background site 33.0 6.11 < 0.32 < 1 %


17

4.3

Day 4

Position on the map

Details Respirable Dust

(µg/m3)




3 Down wind sampler 16.2 6.11 0.38 2.3 %

5 Upwind sampler 15.4 1.72 < 0.3 < 2 %

6 Near fence north of demolition area

15.4 3.29 < 0.3 < 2 %

Urban Air Road Background site 11.6 4.0 < 0.3 < 2.6 %


+ Very windy day at the TEOM site but sheltered by trees at the demolition site

*Results from TEOM PM10 site managed by the local authority (result is not corrected by the compensating factor 1.3). The results from PM10 TEOM samplers are often multiplied by a factor of 1.3 to make the values comparable with gravimetric analyses. It is though that some TEOM samplers may under sample PM10.

SITE 3: CITY CENTRE RING ROAD CONSTRUCTION

4.3.1 Location

The construction of a road bypass (dual carriage way) in the centre of a major city in the Midlands.

4.3.2 Activities

Sampling took place on two separate days about a month apart. The activities sampled involved, hand demolition and recovery of Victorian bricks, excavation, laying of hard core containing recycled concrete, compressing of hard core with rollers, drilling of concrete, and movement of lorries along hard core road. These activities took place continuously, except of the drilling of concrete, which took place for a very short period on the second day. Some kerb cutting took place on site but not on the days when the visits took place. We were informed that the kerbs were laid in a way to minimise their cutting and that this activity was sporadic. Cutting activities were more likely to take place on corners where the blocks required shortening.

Photographs of the activities are in Appendix 2.

4.3.3 Dust controls

There was little evidence of the suppression of dust on site, although it had rained the night before and the presence of wet areas along the hard-core roadway suggested some water damping had occurred. The tires of vehicles were not wetted before entering or leaving the site. Public roads in the vicinity of the site were periodically cleaned with a road sweeper.

18

4.3.3.1 Personal protective equipment (PPE)

The workers wore safety shoes, hard hats, high visibility jackets, and were provided with safety glasses. Drilling of concrete or brick took place for a short period on day 2. The employee operating the power drill did not wear a dust mask.

4.3.4 Weather

Day 1:

The weather was generally fine with occasional rain in the afternoon. The median temperature was 13.4 °C and the median humidity was 75 %. The wind was from the southeast and its speed ranged from 0 to 2.2 m/s with a median of 1.3 m/s.

Day 2:

The weather station failed during this trip so no specific information is available. There was some light rain during the day.


Approximate site boundary is marked as

The plan is orientated so the top is towards north.

The positions identified by the circles were used on day 1 and the positions identified by the squares were used on day 2.

19

4.3.6 Wind Direction

The following wind direction was observed at the site on day 1.


360 20

40 60

80

100

120 140

160 180

200 220

240

260

280

300 320

340

The shaded area indicate the direction the wind is from

The wind direction was along the road on day 1. Trucks carrying hard core entered the site close to position 1 and spread their loads between sampler positions 2 and 5. Sampler 5 was upwind of the activity. Sampler 3 was relatively close to a hand demolition activity no upwind sampler was available for this activity.

20

4.3.7 Results

Table 8: Results from site 3

Day 1

Position on the map

(Dots)


(µg/m3)




1 Entrance where lorries enter site

25.0 12.7 0.64 2.6

2 Down wind of lorries unloading along hard core road

35.3 16.5 0.72 2.0

3 Down wind of hand demolition and brick cleaning

38.5 18.7 0.11 0.2

5 Down wind of brick sorting and cleaning (< 3m)

28.8 12.5 0.69 2.3

Urban Air Background 27.0 6.6 0.44 1.6


Day 2

Position on the map

(Squares)


(µg/m3)




1 Down wind of tarmac and lorry unloading

29.0 11.1 0.54 1.9

2 Close to fence near road

24.0 3.8 0.13 0.5

3 Nr Mosque downwind of momentary drilling activity and movement of lorries

41.0 21.3 0.94 2.3

21

4 End of site opposite occasional lorry movements

32.0 16.9 1.04 3.2

Urban Air Sampler failed


*The results are from a TEOM PM10 site managed by the local authority and are not corrected by the compensating factor 1.3. The results from PM10 TEOM samplers are often multiplied by a factor of 1.3 to make the values comparable with gravimetric analyses. It is thought hat some TEOM samplers may under sample PM10.

22

4.4 SITE 4: STREET BLOCK CUTTING

4.4.1 Location

The front garden of a house in a residential area.

4.4.2 Activities

Sampling took place on a single day. The work involved laying of blocks on the front garden of a house in order to provide an area for a vehicle to park involving the excavation of the garden, laying of sand (a couple of hours in the morning) and other material to level the work area, cutting of the blocks with cut-off saws (several hours) and laying them.

Photographs of the activities are shown in Appendix 2.

4.4.3 Dust Controls

A container with water, pressurised by periodically pumping a handle, was connected to the disc saw, wetted the cutting blade. There was no indication on the water container to inform the worker that the pressure had dropped. It is suspected that the flow rate is inconsistent because of the occasional reduction of water pressure and the requirement for a worker to pump the container. This control was unlikely to meet the flow rates specified in A Thorpe et al (1999) for effective suppression of dust. A bench saw was also used and had a reservoir of water under the bench work surface to wet the blade.

4.4.4 Personal Protective Equipment

The workers wore, safety helmets, safety boots, high visibility jackets, goggles when cutting the blocks and gloves when handling the bench saw. None of the workers wore dust masks.

4.4.5 Weather

Weather station was not available so specific data was not obtained. The day was dry and sunny.

23


The plan is orientated so the top is towards north

The prevailing wind is usually from the west. The majority of the activity was between samplers 1 and 2. The cutting activity was about 3 - 4 meters west and other activity took place in the garden of a house 5 – 6 meters east of samplers 1 and 2.

24

4.5

4.4.7 Results


Position Details Respirable Dust

(µg/m3)




1 Nr Driveway and gate opposite cutting bench

73.4 58.9 11.1 15

2 Opposite side of gate near near cutting saw area

76.9 53.65 11.9 15

3 About 10 m from sampler 2

27.8 12.8 2.9 10

Urban Air 13.0 3.61


*The results are from a TEOM PM10 site managed by the local authority and are not corrected by the compensating factor 1.3. The results from PM10 TEOM samplers are often multiplied by a factor of 1.3 to make the values comparable with gravimetric analyses. It is thought hat some TEOM samplers may under sample PM10

SITE 5: STREET BLOCK CUTTING

4.5.1 Location

Area of road allocated for on street parking by residents in a suburb of a city in Yorkshire.

4.5.2 Activities

Sampling took place on a single day. This work involved the packing of sand and levelling the area designed to contain the block cutting. Placing blocks in the allocated pattern, cutting blocks with a disc cutter to fill in the remaining spaces and packing sand.

4.5.3 Dust controls

A pressurised water container was attached to the disc cutter. I was informed that the pattern of blocks was purposefully designed to reduce the amount of cutting. The maximum cutting time was about 40 minutes in a working day of about 6 hours.

4.5.3.1 Personal protected equipment (PPE)

The workers wore, safety helmets (although not all the time), safety boots, high and visibility jackets. None of the workers wore dust masks.

25

4.5.4 Weather

The weather was warm and dry with little wind. The median temperature was 19 °C and the median humidity was 59 %. The wind was from the north, directly down the street, and had a speed between 0.1 to 0.2 m/s (median wind speed was 0.1 m/s).


Wind Direction During Cutting 360

20

40

60

80

100

120

140

160 180

200

220

240

260

280

300

320

340


The shaded area on the wind rose indicates the direction the wind is from.

Sampler 1 was moved to position 1b after a couple of hours as it was clear that no activity was taking place near its location.

26

4.6

4.5.6 Results


Position Details Respirable Dust

(µg/m3)




1/1b Middle of site near sand and cutting area

35.1 10.1 1.20 3.4

2 Upwind of cutting area

25.5 9.6 1.06 4.1

3 Down wind of cutting area

35.5 6.2 0.5 1.4

Urban Air 17.5 2.8 0.16 1.0



SITE 6: RUBBLE CLEARANCE FROM DEMOLITION

4.6.1 Location

The site of a demolition of a 3 level block of flats in a residential area, with 3 miles of a city centre.

4.6.2 Activities

Sampling took place on a single day. The workers used a JCB to move brick and concrete rubble into piles and to load into trucks. The work progressed


4.6.3 Dust Controls

A worker with a hosepipe dosed the rubble and contents of lorries with water.


The workers wore, safety helmets, safety boots, high and visibility jackets. None of the workers wore dust masks.

27

4.6.4 Weather

The day was warm but cloudy and the ground was initially damp from rain the previous night. The median temperature was 21 °C and the median humidity was 73 %. The recorded wind direction was from the northeast with a speed between 0.1 to 1.3 m/s (median wind speed was 0.7 m/s).

4.6.5 Sampler Locations

Wind Direction

360 20

40 60

80

100

120 140

160 180

200 220

240

260

280

300 320

340

Approximate boundary is shown as


The shaded area on the wind rose indicates the direction the wind is from.

28

4.6.6 Results


Position Details Respirable Non Respirable Percent RCS on map Dust

(µg/m3)

combustable fraction (µg/m3)

Crystalline Silica (RCS) (µg/m3)

in respirable fraction

1 Nearest road opposite rubble movement with JCB

25.8 5.2 Not Detected

2 Parameter opposite cabin

18.1 5.6 0.41 2.2

3 Top of site near JCB rubble movement during the afternoon

35.3 25.2 1.31 3.7

4 Adjacent to skip and placed in direction of drifting dust from loading lorries

42.0 29.3 1.17 4.0

Urban Air

11.9 3.6 0.25 2.0



The direction of the wind recorded by the weather station would indicate that samplers 1 and 2 were down wind and samplers in positions 3 and 4 were upwind. However, these recordings are contrary to observations on the day of sampling, which suggested that the wind was actually in the opposite direction. It is highly possible that a problem occurred with the weather station’s wind vane that wasn’t detected on the day, since the predominant wind direction recorded by several airports in the same region was from the west and the site was exposed towards the west whereas the north and east had some tree cover. The sampling positions that obtained the highest values were on the northeast parameter behind which were grass fields, so the potential source for the dust levels supposedly entering the site is not obvious.

29

4.7 SITE 7: DEMOLITION OF COLLEGE

4.7.1 Location

The site was situated near the centre of the city near, high street shopping areas, offices and a court.

4.7.2 Activities

The sampling was performed on two days about a week apart. The work activities observed were; the breaking up of concrete with powered hammers attached to excavators (all day on the first day); removal of walls and material with an extended arm on an excavator and movement of vehicles sorting of concrete and brick rubble (both days).


4.7.3 Dust Controls

A pump linked to a mobile container (trailer size) would project a jet of water towards the area under demolition (four floors high).


The workers wore, safety helmets, safety boots, high and visibility jackets. None of the workers wore dust masks.

4.7.4 Weather

Day 1:

The weather was cloudy but dry. The median temperature was 15 °C and the median humidity was 66 %. The wind was mainly from the west with a wind speed between 0.4 to 1.8 m/s (median wind speed was 0.4 m/s).

Day 2

The weather was cloudy with some rain in the afternoon. The median temperature was 17.7 °C and the median humidity was 70 %. The wind was from the northwest with a wind speed between 1.8 to 2.7 m/s (the median wind speed was 2.2 m/s).

30

4.7.5 Location of Samplers

Weather Day 2

360 20

40 60

80 100

120 140

160 180

200 220

240 260 280

300 320

340

Weather Day 1

360 20

40 60

80

100

120 140

160 180

200 220

240

260

280

300 320

340

Approximate site boundary is indicated as

The purple square marked with the arrow in the building represents the approximate site of work with the JCB extended arm

The chequered boxes represent previously demolished buildings. Movement of rubble and drilling of concrete with JCBs took place in the chequered box above the area marked by the arrow.

The shaded areas in the wind roses represent the direction the wind is from.

The positions identified by the circles were used on day 1 and the positions identified by the squares were used in day 2.

The sampler in position 1 (circle) was upwind on day 1 and samplers 2,3 and 4 (circles) were down wind. On day 2, none of the samplers (boxes) were in an ideal position to be classified as the upwind sampler. However, the sampler in position 4 (box) is the most upwind sampler and sampler positions 1,2 and 3 (boxes) are downwind.

31

4.7.6 Results


Day 1

Position on map

(Spots)


(µg/m3)




1 Upwind sampler 25.3 10.5 0.7 2.7

2 Down wind of JCB hammer drills

51.4 37.7 8.36 16

3 Down wind of demolition with extended arm

85.0 44.1 11.5 14

4 Near rest areas and in dust from demolition

184 145.3 7.65 4.1

Urban Air

18.8 12.6 0.29 1.5


Day 2

Position on map

(Squares)


(µg/m3)




1 Down wind of JCB demolition with extended arm

229.3 185.9 11.2 5

2 Further down wind from 1 near College Road Entrance

143.9 110.5 9.9 7

3 Down wind of demolition near the rest area

90.5 58.5 8.1 9

4 Opposite Portacabin and rubble movement

43.5 28.3 7.4 17

Urban Air

16.0 4.2 0.25 1.5

32



33

5 COMPARISON WITH TEOM MEASUREMENTS

Background measurements, from the centre of the town or city were compared with data provided by the local authority, from air quality monitoring sites for PM 10 measurements taken over the same sampling period in approximately the same area. The HSL sampler was often located next to the local air quality-monitoring site to provide a direct comparison, however colocation of samplers was not always possible, or the Tapered Element Oscillating Microbalance (TEOM) instrument operated by the local authority failed, obtained negative values or had a scheduled service. Figure 5 compares the gravimetric result obtained from the HSL sampler working to the occupational hygiene convention for respirable dust with the result obtained with the TEOM analyzer, working to the PM10 convention used in environmental science, operated by the local authority or UK national air quality monitoring site. When compared with the European Union reference samplers TEOM results are multiplied by a factor of 1.3 to compensate for some under sampling. However, the results shown in Figure 5 are not corrected using this factor because the uncorrected results provided the best visual correlation with the line drawn on the chart for the ideal 1:1 relationship.

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40

TEOM PM10concentration µg/m3

HSL

Res

pira

ble

dust

con

cent

ratio

n µg

/m3

Linear (1:1 Relationship)

Figure 5 Comparison with TEOM results (uncorrected)

The majority of results are close to the ideal 1:1 relationship. The following observations were made for the four samples where the result from the HSL sampler was higher than the TEOM result.

• The HSL sampler was parked much closer to the road (< 10 m) compared with the local authority site (approximately 20 – 30m)

• It was windy and at TEOM site, which actually recorded some negative values, suggesting a leak, a high concentration of volatile particles or other problems.

• The TEOM was serviced that day and the measurement supplied by the local authority might not be representative of the area in which the HSL sample was taken.

The good correlation is probably because the particle sizes of the most likely major components of urban air dust (diesel fume, pollen and organic volatiles) are very small, so the different size selection parameters do not significantly influence the mass collected on the filter.

34

6 CRYSTALLINE COMPONENTS OF URBAN AIR

The air sample filters were scanned by XRD using a 25 mm diameter filter holder and a low background silicon substrate as a backing material. The use of X-ray diffraction allows the identification of the crystalline components of the dust and the following substances were found (Table 13). Some filters were scanned in sampler holders designed at HSL to suspend the filter by its edges. The samples locations identified as ‘urban air’ were taken by a sampler sited some distance from the work area to provide an indication of the background levels and type of dust at a location way from the construction activity.

Table 13;Proposed crystalline components in the analysis samples

Site Location Proposed Crystalline Components

City 1 Site 1 Day 1

(October)

Urban Air

Quartz (SiO2), Calcite (CaCO3), Anhydrite (CaSO4)

Probable Halite (NaCl) or Chlorargyrite (AgCl)

Possible Diiron di-calcium oxide Fe2O3(CaO)2, and Iron Nitride (Fe4N)

On Site Quartz (SiO2), Calcite (CaCO3),

City 1 Site 1 Day 2

(October)

Urban Air

Quartz (SiO2), Calcite (CaCO3), Halite (NaCl), Kaolinite (clay) possibly Iron (Fe)

On site Quartz (SiO2), Calcite (CaCO3), possibly Maganosite MnO, Anatase (TiO2) and Maghemite (Fe2O3), or Tin Sulphide (SnS), or Na4 (SO4)1.5(CO3)0.5, or PbSnS2

City 2 Site 2 Day 2

(April)

Urban Air

Quartz (SiO2), Calcite (CaCO3), Halite (NaCl),

Ferrite (Fe) or Aluminium (Al) contamination from sample preparation process

On site Quartz (SiO2), Calcite (CaCO3), Halite (NaCl), possibly a Mica (Muscovite)

City 2 Site 2 Day 3

(May)

Urban Air

Quartz (SiO2), Calcite (CaCO3), Halite (NaCl), Ferrite (Fe) or Aluminium (Al) contamination from sample preparation process, Illite (clay) K(H2O) Al2Si3AlO10(OH)2, Tobermorite 9 A Ca5(Si6O16)(OH)2 or Kaolinite (clay), Dolomite CaMg(CO3)2

On site Quartz (SiO2), Calcite (CaCO3), Maghemite (Fe2O3), Tricalcium silicate and probably a clay or mica

City 2 Site 2 Day 4

(May)

Urban Air

Quartz (SiO2), Calcite (CaCO3), Calcium Sulphate Hydrate (CaSO4)0.15 H2O

On site Quartz (SiO2) and possibly Halite NaCl

35

City 3 Site 3 Day 1

(May)

Urban Air

Halite (NaCl), Quartz (SiO2), Calcite (CaCO3),

Ferrite (Fe) or Aluminium (Al) contamination from sample preparation process

On site Quartz (SiO2), Calcite (CaCO3) or (MgCaCO3), Maghemite (Fe2O3), Halite (NaCl), Kaolinite (Al2(Si2O5)(OH)4)

City 3 Site 3 Day 2

Urban Air


(July) On site Quartz (SiO2), Calcite (CaCO3) or (MgCaCO3), Maghemite (Fe2O3), Halite (NaCl), Kaolinite (Al2(Si2O5)(OH)4), possibly Illite (clay) and Tricalcium silicate (concrete or cement product).

City 4 Site 4, Day 1

Urban Air

Quartz (SiO2), Calcite (CaCO3), Ferric Oxide (Fe2O3), possibly Iron Fe

(July) On site Quartz (SiO2), Calcite (CaCO3) or (MgCaCO3), Halite (NaCl), Kaolinite (Al2(Si2O5)(OH)4), possibly Illite (clay).

City 2, Site 5, Day 1

Urban Air

Halite (NaCl), Quartz (SiO2), Calcite (CaCO3), Maghemite (Fe2O3),

(September) On site Quartz (SiO2), Calcite (CaCO3) or (MgCaCO3), Halite (NaCl), Kaolinite (Al2(Si2O5)(OH)4), Anhydrite (CaSO4)

City 2 Site 6, Day 1

Urban Air

Halite (NaCl), Quartz (SiO2), Calcite (CaCO3), Maghemite (Fe2O3), Kaolinite (clay)

(September) On site Quartz (SiO2), Calcite (CaCO3), Anhydrite (CaSO4), Calcium Silicate Hydrate (CaSO4)0.5 H2O, possibly Dicalciumsilicate Ca2(SiO4)

City 2, Site 6 Day 2

Urban Air


(September) On site Quartz (SiO2), Calcite (CaCO3), Halite (NaCl), Calcium Silicate Hydrate (CaSO4)0.5 H2O, Portlandite (Ca(OH)2) probably Hatrurite (Ca(SiO4)O)

City 1Site 7

Day 1

(August)

Urban Air

Halite (NaCl), Quartz (SiO2), Calcite (CaCO3), Iron Sulphite FeS or Maghemite (Fe2O3), possibly Ferrite Fe or Al

On site Quartz (SiO2), Calcite (CaCO3), Halite (NaCl), Anhydrite (CaSO4) Calcium Silicate Hydrate (CaSO4)0.5 H2O, Dolomite (CaMg(CO3)2) possibly (Fe4N)

XRD reflections highly indicative of the presence of halite (NaCl), were found in most of the urban samples, except for those in July and for the first set of results, when silver filters were used in the preparation of the analysis filters. The scans of the dust on the silver filters indicate the presence of chlorargyrite (AgCl), rather than NaCl, which is possibly due to a reaction between NaCl, the silver filter and the isopropanol used to recover the dust from the air sample

36

filter. June was a particularly dry month in 2009 and the sampling took place in the early in July. It is postulated that the absence of salt in the urban air is dependent on dry periods of weather because the highly soluble salt is probably incorporated in the moisture or water vapour. XRD reflections indicative of anhydrite (CaSO4) and calcium sulphate demihydrate (CaSO40.5H2O) rather than gypsum (CaSO42H2O), were found on many of the samples. This is possibly due to a reaction between gypsum and heat, even though the majority of samples were ashed in a low temperature plasma asher rather than a furnace. Many of the urban air samples showed only the presence of the primary calcite or quartz reflection. In these cases, it was assumed that quartz and calcite were present because of the confirmatory evidence of secondary reflections in other scans form other urban air samples. Calcium silicates associated with concrete or cement, calcium hydroxides, and iron oxides are indicative of industrial activity. Calcium sulphates are likely to be indicative of domestic and industrial activity since there were no natural deposits in the vicinity of the cities where the sampling activity took place. Calcite and quartz are minerals that are both naturally present in the geology of the location of several of the cities visited and also components of building work. Many of the samples of dust recovered from the ashing process were pink or orange, which may confirm the presence of hematite or iron converted to hematite. Figure 5 shows the colours of some of the samples. Sample 08830/08 shown in the picture is a field blank sample.

Figure 6 Colour of samples after recovery

The presence of quartz, gypsum, clays, halite and calcite in environmental type samples are confirmed in other work from Spain (Bernabé et al, 2005)

37

7.1

7 DISCUSSION

SUMMARY OF RESULTS

Presented in the table 14 is a summary of the results obtained from the sampling of construction sites

Table 14: Summary of dust results

Respirable Dust (ISO/CEN Convention)

Value Urban Air

General Activities

Road Building

Block Cutting

Demolition

Median µg.m-3 17.5 24 29 35.1 40.6

Minimum µg.m-3 11.6 17.4 24 17.5 15.4

Maximun µg.m-3 34.4 29.5 41 76.9 229

Number of Samples

11 9 10 7 22

Non conbustable and non volatile respirable dust

Value Urban Air

General Activities

Road Building

Block Cutting

Demolition

Median µg.m-3 4.7 7.3 12.7 10.1 10.1

Minimum µg.m-3 2.8 4.7 3.8 2.8 1.7

Maximun µg.m-3 12.6 11.6 21.3 58.9 186

Number of Samples

11 9 10 7 22

Respirable Crystalline Silica

Value Urban Air

General Activities

Road Building

Block Cutting

(TWA)*

Demolition

(TWA)*

Median µg.m-3 0.24 0.19 0.64 1.2 (1.8) 0.94 (2.1)

Minimum µg.m-3 0.08 0.08 0.11 0.16 (0.33) 0 (0.31)

Maximun µg.m-3 0.44 0.39 1.04 11.9 (12.8) 11.5 (13.5)

Number of Samples

8 9 10 7 22

38

7.2

(TWA)* is the 8-hour time weighted average without breaks

The majority of values reported in table 14 are close to the results for 8-hour time weighted averages (TWAs) because the sampling took place continuously over the working full shift.

RESPIRABLE DUST

The median values for respirable dust were found to increase in the following order,

Demolition Activities

Block cutting Increasing median respirable dust value Road Building

General Construction Activities

Urban Air

The order of these activities may also be dependent on the environmental conditions at the location and not just the type of activity.

The distribution of results for respirable dust are shown in Figure 7

0

5

10

15

20

25

10 20 30 40 50 60 70 80 90 100

110

120

130

140

150

160

170

180

190

200

210

Respirable Dust Levels (µg/m-3)

Freq

uenc

y

Demolition Block Cutting Road Building General Activities Urban air

Figure 7 Respirable Dust Levels

Figure 7 shows that most results in this pilot study are unlikely to be significantly different from the range of values obtained for urban air. The Shapiro-Wilk normality test indicated that only the distribution of results from the demolition activity were not normally different at the 95 % confidence level (p = < 0.001). In the United Kingdom it is a requirement in the Air Quality Standards regulations (Crown 2002, 2007) that a daily exposure for PM10 over 24 hours should

39

7.3

not exceed 50 µg.m-3 more than 35 times (7 times in Scotland) a year. The annual mean is required to be below 40 µg.m-3. No results from the general construction activities and the urban air sites were above 40 µg.m-3. Only the block cutting and demolition activities gave results above 50 µg.m-3. Two results from samplers sited very close to the block cutting work and 8 out of 22 results from the demolition activities were above the UK air quality value for PM10. Most of these results came from the very largest demolition activity where control of dust was difficult because of the size of the building. Some of the samplers at the demolition site were well inside the parameter but at a distance from the site of the major work activity (~50 m). It was fortuitous that the majority of the site was down wind of the demolition activity and the samplers could be accommodated within the perimeter. On the eastern side, < 20 m from the demolition, was the local crown court.

WEIGHT OF DUST RECOVERED FROM ASHING

A low temperature plasma asher was selected to remove the air sample filter in the analytical recovery process, rather than a furnace, because the plasma asher is able to effectively remove the carbon particulate and is less likely to cause chemical changes in the mineral components present. However, results from the XRD diffraction scans suggest that gypsum was altered to the demi hydrate or anhydrate form. This may slightly affect the weights obtained from the recoveries. Table 15 shows the average combustible and volatile content in the sample from each sector studied (not blank corrected).

Table 15: Average combustible and volatile matter (percent)

Activity Average Value (%)

Demolition 42

Block Cutting 47

Road Building 57

General Activities 67

Urban Air 73

Decreasing combustible/ volatile content in the samples

These results suggest that the majority of the mass collected by the samplers by three of the activities (urban air background measurement, general construction activities and road building) originated from carbon-based substances. Harrison (2000) predicts that the composition of the origin of urban air samples would be 47 % from combustion sources and 32 % from secondary sources. In the urban air samples 73 % of the dust by mass on average is probably from vehicle emissions or pollen and about 27 % is probably dust from the local geology, industrial and road safety activities (salting). The value of 73 % in this report is close to the combined primary combustion and secondary particles estimate.

RESPIRABLE CRYSTALLINE SILICA

The results for RCS in the dust were low for all the activities (< 13 µg.m-3). The presence of the secondary quartz peaks in the XRD scans for the urban air samples was only observed on a couple of the scans, so the quantification is based on the primary XRD reflection at 26.67 degrees 2θ, and assuming no other interference is present at this angle. At one point all the results had to be reanalysed because a peak at 26.67 was found to originate from an aluminium

40

7.4

7.5

backing plate in the filter holders supplied by the manufacturer. Thirty six percent of samples (16 from 44 filters) from the sites reported values greater than or equal to 1 µg.m-3 (a 1/100th of the present WEL of 100 µg/m3). There were four peak exposures that were greater than 10 µg.m-3 (1/10 of the current WEL), two from the block cutting and two from the demolition. The two samplers from the block cutting with results greater than 10 µg.m-3 were sited close to the cutting activity (approximately < 5 m) because work activity area was small (a front garden and pavement) and data from the demolition activities are skewed because site 7 obtained the majority of results (7 out of 8) close to or above to 10 µg/m3 (7.5 – 13.5 mg.m-3).

TRANSPORT OF DUST ACROSS THE SITES

Table 16 compares the differences between the upwind and down wind air concentration values for respirable dust. The results obtained for the sampler sited to determine a general level of dust not influenced by the site, termed the ‘urban s air’, also shown for comparison is ascertain if the results for the upwind samples were influenced by the work activity. The average of the upwind measurements is not significantly different from the average value from the urban air background samples (p=0.2). All the activities show a positive increase for respirable dust when compared with the value obtained for the upwind air concentration, except one. The exception was from a demolition site where the main activity was to change the grappling arm on a machine. This work was not likely to produce measurable levels of dust, although, some activities such as, the movement and sorting of rubble and demolition, took place for about three hours in the afternoon. The highest levels are from block cutting (maximum ratio of upwind air concentration to average down wind air concentration = 2.7) and demolition (maximum ratio of upwind will be higher because for block cutting and the demolition at site 7 the proximity of the upwind sampler to the work activity is likely to have influenced results.

41

Table 16: Transport of respirable dust across the sites

Site Activity Upwind result

(UP) µg.m-3

Urban air result

(UA) µg.m-3

Down Wind Average

(DW) µg.m-3

Ratio

(DW/UP)

1 General 17.9 17.4 24.1 1.3

1 General 22.7 27.7 27.3 1.2

2 Demolition 24.1 33.0 50 2.1

2 Demolition 15.4 11.6 15.8 1.0

3 Road Construction

28.8 27.0 36.9 1.3

3* Road Construction

24 Failed 34 1.4

4 Block cutting

27.8x 13.0 75.2 2.7

5 Block Cutting

25.5 17.5 35.3 1.4

6 Rubble Moving/Sort ing

23.0# 11.9 38.7 1.7

7 Demolition 23.3 18.8 107 4.6

7 Demolition 43.5X 16.0 154 3.6

* Assuming the lowest value is down wind

XUpwind sampler is possibly sited too close to the activity

#Average of two values

Table 17 compares the differences between upwind and downwind air concentrations of RCS. These results indicate that, generally, RCS does migrate across the site boundaries and potentially into public areas, although the air concentrations are low. Nine of eleven values are positive and two others are negative suggesting that RCS was moving onto site or not significantly different from the air concentration generated by the activity. Surprisingly, one of these ratios is from a block cutting activity which may indicate the sampler was either too close to the activity or that was influenced by other dust from activities further up the street. A ratio less than 1 was also obtained from the road construction activity. A relatively high value for the upwind sampler at site 7 (7.4 µg/m3) and at site 4 (2.9 µg/m3) indicate the samplers were probably sited too close to work activity. The air concentration values obtained from ‘urban air’ samples ranged from not detected to 0.44 µg/m3. Five of the values from the upwind sites were

42

over 0.44 µg/m3, which may indicate the samplers were too close but the higher levels could also be due to the environmental conditions at the site.

Table: 17; Transport of RCS across construction sites

Site Activity Upwind result

(UP) µg.m-3

Down Wind Average (DW) µg.m-3

Ratio

(DW/UP)

1 General 0.2 0.26 1.3

1 General 0.08 0.2 2.5

2 Demolition 0.4 1.4 3.4

2 Demolition <0.3 0.38 (max) 1.3 (maximum value)

3 Road Construction

0.69 0.49 0.7

3* Road Construction

0.13 0.84 6.4

4 Block cutting 2.9X 11.5 4.0

5 Block Cutting 1.1X 0.85 0.8

6 Rubble Moving/Sorting

<0.3 0.96 >3.2

7 Demolition 0.7X 9.17 13

7 Demolition 7.4X 9.7 1.3

* Assuming the lowest value is down wind

XUpwind sampler is possibly sited too close to the activity

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8 CONCLUSIONS

The following conclusions were observed from these data.

The HSL sampler provides a good indication of both occupational and environmental air concentrations because the air concentrations for respirable dust obtained by sampler developed at HSL correspond closely to the PM10 results obtained by the local authority TEOM samplers (uncorrected by 1.3). The regression coefficient (r2) excluding extreme values was 0.92.

All sites visited were trying to apply what they perceived as reasonable controls for health and safety. Although, even in dusty areas, most workers did not wear masks.

The results obtained for respirable dust are generally low. Nine out of forty four results (20%) at construction sites were above the United Kingdom’s air quality standard value for PM10 of 50 µg.m-3. Two of the results > 50 µg.m-3 were from samplers sited within close proximity (< 5 m) to block cutting and the rest of the results > 50 µg.m-3 were attributable to demolition activities.

On average the residue remaining from the plasma ashing of the air samples from different construction activities constituted between 58 - 27 % of the sample. The urban air samples lost 73 % of their weight (on average) after ashing. Samples from block cutting or demolition contained a larger residue (53 – 58%) compared with road building, general activities and urban air samples (27 – 43 %), suggesting a higher mineral component and therefore associated with the activities being monitored.

The estimated range of values for RCS from the urban air comparative samplers was approximately 0.1 – 0.44 µg.m-3. Sixteen samples (36%) from construction sites reported air concentrations in excess of 1 µg.m-3 and five (11%) were 10 µg.m-3 or above. This proportion is greater than the study from quarries by Mark et al (2009) who found 4 % of samples with RCS > 10 µg.m-3, however the current study is not as statistically robust because fewer samplers were taken.

The ratios of air concentrations of RCS between the upwind and down wind samplers indicate the migration of silica across sites and potentially beyond the site boundaries.

Many of the mineral components in the samples from the urban air are also found in samples from construction sites which suggests the origin of the dust is either from the buildings in the urban environment, the mineralogy of the area or from the construction sites themselves. The sampling volumes were not sufficient to positively confirm a link.

The results in this pilot study indicate that dust control may still be a problem with very large-scale demolition activities and with cut-off saws and that these areas may warrant further investigation.

44

9 REFERENCES

British Standards Institution (1993) Workplace atmospheres - Size fraction definitions for measurement of airborne particles BS EN 481 1993 ISBN 0 580 22140 7

Bernabé J, M Carretero, Galán E,(2005) Mineralology and origin of atmospheric particles in the industrial area of Huelva (SW Spain), Atmospheric Environment, 39 p 6777 – 6789, 2005.

Bontempi E et al (2008), Analysis of crystalline phases in airborne particulate matter by two-dimensional x-ray diffraction, J. Environ. Monit 10, 82-88

Crown (2002) Office of Public Sector Information Statutory Instrument No. 297 Environmental Protection The Air Quality (Scotland) Amendment Regulations 2002 http://www.opsi.gov.uk/legislation/scotland/ssi2002/20020297.htm last viewed 29th March 2010

Crown (2007), Office of Public Sector Information, Statutory Instrument No 64, The Air Quality Standards Regulations 2007, http://www.opsi.gov.uk/si/si2007/uksi_20070064_en_1 last viewed 24th June 2010.

Esteve V et al. (1997), Quantitative x-ray diffraction phase analysis of airborne particulate by a cascade impactor sampler using Riedweld full pattern method. Powder Diffraction , September 1997 Vol12, No3, pp. 151-154

Harrison R (2000), Session 2E – Source apportionment of PMx (Special Session), Studies of the source apportionment of airborne particulate matter in the United Kingdom, J Aerosol Sci, Vol 31, Suppl 1 pp S106 – S107, 2000

HSE (2009) Health and Safety Executive Operational Circular SIM 02/2009/01 The control of silica risks associated with kerb, paving an block cutting. http://www.opsi.gov.uk/si/si2007/uksi_20070064_en_1 last viewed April 2010.

Kenny LC and Lidén G (1991) A technique for assessing size-selective dust samplers using the APS and polydisperse test aerosols, J. Aerosol Sci., 22, 91-100.

Mark D, Thorpe A,Saunders J, Stacey P and Cottrell S (2009), Assessment of ambient levels of respirable crystalline silica in quarries, HSL report ECM/2008/12, Health and Safety Laboratory, Harpur Hill, Buxton, SK17 9JN.

Met Office (2009) Summer 2009 Roundup, Crown Copyright http://www.metoffice.gov.uk/corporate/pressoffice/2009/pr20090907.html Last viewed in April 2010.

Moore M (1999) Crystalline silica: occurrence and use, Indoor and Built Environment, 8, 82-88.

NIOSH (2003)) 7500 Silica, Crystalline by XRD (filter redeposition) NIOSH Manual of Analytical Methods NMAM Fourth Edition, Cincinnati Ohio USA

Rice F (2000), Consise International Chemical Assessment Document No 24, Crystalline Silica, Inter-organizational programme for the sound management of chemicals, International programme on chemical safety, World Health Organization Geneva, 2000, http://www.inchem.org/documents/cicads/cicads/cicad24.htm#PartNumber:5

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http://www.inchem.org/documents/cicads/cicads/cicad24.htm#PartNumber:5

http://www.opsi.gov.uk/si/si2007/uksi_20070064_en_1

http://www.opsi.gov.uk/si/si2007/uksi_20070064_en_1

http://www.opsi.gov.uk/legislation/scotland/ssi2002/20020297.htm

Shiraki R and Holmen BA (2002) Airborne respirable silica near a sand and gravel facility in central California: XRD and elemental analysis to distinguish source and background quartz.Environ. Sci. Technol, 36, 4956-4961

Stacey P, Tylee B, Bard D, and Atkinson R, (2003) The performance of laboratories analysing α-quartz in the Workplace Analysis Scheme for Proficiency (WASP), Ann occup Hyg, Vol 47, No4, pp 269 – 277, 2003

Thorpe A, Ritchie A, Gibson M and Brown R (1999), Measurements of the effectiveness of Dust Control on Cut-off Saws Used in the Construction Industry, Ann occup Hyg, Vol 43, No7 pp 443-456, 1999

Weather Underground (2010) http://www.wunderground.com/global/UK.html, last viewed April 2010

Whittaker, A.G. (2003). Jones, T.P, Shao, L-Y., Shi, Z., BéruBé, K.A. and Richards, R.J. Mineral Dust in Urban Air: Beijing, China. Min. Mag, 67(2), 173-182.

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http://www.wunderground.com/global/UK.html

10 APPENDICES 1: XRD CALIBRATIONS

Re-deposition of A9950 on Silver Filters (corrected for crystallinity)

Qtz 26 = 2.2616x R2 = 0.9965

Qtz 21 = 14.418x R2 = 0.9902

Qtz 50 = 19.102x R2 = 0.9909

0

100

200

300

400

500

600

0 50 100 150 200 250

Intensity (cps)

Mas

s (µ

g) QTz21

Qtz26

Qtz50

48

11 APPENDIX 2

11.1 SITE 1 CONSTRUCTION

Figure 8 Location of sampler in position 3

Figure 9 Location of sampler in position 4

49

Figure 10 Location of sampler for city centre background measurement

Figure 11 On site cement plant opposite sampler 2

50

Figure 12 Excavation activities near sampler positions 2 and 3 on day 2. Sampler 3 is about 10 m to the right of the excavation.

11.2 SITE 2 DEMOLITION

51

Figure 13 General site and position of sampler 1 on day 2

Figure 14 The demolition site

TEOM PM10 Sampler Site

HSL sample position

Figure 15 City centre site with the local authority TEOM PM 10 monitoring site in the background

52

Figure 16 Activity Day 2

Figure 17 Activity stopped on day 2 due to the discovery of Amosite asbestos pipe lagging

53

Figure 18 Demolition Activity Day 3

Figure 19 Controls during demolition on day 3

54

11.3 SITE 3: RING ROAD CONSTRUCTION

11.3.1 Day 1

Figure 20 Sampler in position 1 near site entrance

Figure 21 Sampler in position 5 (circles) next to site fence near hand demolition

55

Figure 22 Sampler in position 2 (circles) – excavation and laying of hard core

Figure 23 Sampler in position 3 (circles) near hand demolition of shop

56

Figure 24 Site of urban air sample: The local authority TEOM site is behind the modern building on the right

57

11.3.2 Day 2

Figure 25 Sampler at position 2 (squares) and proximity to the fence

Figure 26 Laying of road at position 1 (squares)

58

Figure 27 Sampler at position 3 (square) near the mosque and nightclub

(Short duration pneumatic drilling took place where workers are standing)

59

11.4 SITE 4: BLOCK CUTTING

Figure 28 Sampler 2 with sampler 1 indicated with arrow in the background

Figure 29 Sampler 3 looking towards sampler 2

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Figure 30 Moving sand for base of paving. The head of sampler 2 is seen in the picture.

Figure 31 Cutting bricks with the cut-off saw. The hand pump is on the left-hand side of the picture. Samplers 1 and 2 are slightly off shot behind the worker and the person taking the picture. The edge of sampler 1 can just be seen behind the worker on the

left.

61

Figure 32 Table saw with reservoir tray in operation. The relative positions of this activity to the samplers are shown in Figure 28

Figure 33 The finished product – brick paving

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11.5 SITE 5: BLOCK CUTTING

Figure 34 Sampler in position 1b. Area of paving is enclosed with barriers.

Figure 35 Sampler in position 2 at the top of the area of the work

63

Figure 36 Laying of blocks in the pattern on sand. Sampler position 3 is behind the person taking the picture.

11.6 SITE 6: RUBBLE CLEARANCE

Figure 37 JCB moving rubble and water suppression in background near sampler position 2

64

Figure 38 Position of sampler 1

Figure 39 Position of sampler 4

65

11.7 SITE 7: DEMOLITION

Figure 40 Position of sampler 2 (circles)

Figure 41 Demolition activity

66

Figure 42 Movement of rubble near sampler 3

Figure 43 Location of urban air sampler position showing comparative height of PM10 and HSL respirable sampler inlets.

67

Figure 44 Water suppression from sampler 1 (squares)

Figure 45 Sampler at position 3 (squares)

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Figure 46 Other activity down wind of the samplers

69

Published by the Health and Safety Executive 07/11



The purpose of this pilot study was to assess the potential for inadvertent exposure of the public to respirable crystalline silica (RCS) from construction activities.

The study assessed the respirable dust (RD) from, demolition, block cutting, road building, general construction activities and city centre air from 13 visits to 7 sites. In total, 48 samples from the construction activities and 11 city centre air samples, for comparison, were collected.

The results obtained for RD and RCS were generally very low. Only 10 % of results (from two sites) for RCS were above 0.01 mg.m-3, which is 10 % of the current Workplace Exposure Limit (WEL) for RCS. The majority of visits showed evidence of some transport of RCS across the site and potentially into public areas. The main crystalline components of the city centre air sample were generally the same as the components of the samples taken at the construction sites.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.

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