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HEALTH SAFETY PROGRAMME FOR WORKERS EXPOSED TO HG°

ENVIRONMENTAL POLLUTION IN THE IDRIJA REGION AND OVER A BROAD AREA

Tatjana Dizdarevic, B.S.M.E.

Idrija Mercury Mine

Idrija, march 2003

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Idrija

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Introduction

Mercury was discovered in y. 1490

500 years of mining and smelting

In y. 1994 the ore excavation and Hg production stoped

The Mine will be shut down in 2006

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Important data Hg content in ore: 0,1 – 10% monomineral ore deposit: 70%

HgS and 30%Hg

12 mill. tons of ore was excavated 153.309 tons of Hg was extracted 107.692 tons of commercial Hg losses: 44.616 tons of Hg

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Closing-down Programme

The Long-term closing down Programme for the gradual, complete and permanent shut down of the Idrija Mine was prepared in 1986, addopted in 1987 and approved in 1989

The results of investigations and closing down works through last few years indicate that the concept of the mine’s shutdown, was wll chosen

thus ensuring the safety of the town above the pit

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Closing-down works in the mine

gradually from the lowest level upwards towards the surface

backfilling (20.512 m of galleries, 120.785 m3 concrete)

injecting (37 locations 43.856 m of boreholes, 70.177 m3 of grout)

flooding of the pit (up to the 4th level)

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WORKING LOADS AND MERCURY CONCENTRATIONS IN THE PIT AND IN THE SMELTING PLANT

Physical loads 5 - 9 Kcal.min-1

(dynamic and static) Pulmonal ventilation 24 - 33 L air.min-1

Air temperature 15 - 30 oC Relative humidity 70 - 92 % Effective temperature 15 - 27.8 Dust concentration 30 - 70 mg.m-3

(respirable part) % free SiO2 in dust 10 - 30 % Ionising radiation Gama dose-rate Carboniferous shale 0.15 -0.20 Gy.h-1

Bituminous shale up to 1 Gy.h-1

Radon concentrations 700 - 1500 Bq.m-3

Radon daughters 1.5 J.m-3 (0.07 WL)

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WORKING LOADS AND MERCURY CONCENTRATIONS IN THE PIT AND IN THE SMELTING PLANT

Mercury concentrations in the pit and in the smelting plant

The pit

cinnabar ore (HgS) excavations 0.10 mgHg0.m-3

native mercury ore excavations 0.10 - 1.002.00 mgHg0.m-3

The smelting plant

“less hazardous jobs” 0.00-0.10 mgHg0.m-3

“more hazardous jobs” 0.10 -2.50

3.00 mgHg0.m-3

Type of workers’ exposure

intermittent workers’ exposure to high Hgo concentr.

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MAJOR PROBLEMS RELATED TO THE TECHNICAL AND HEALTH PROTECTION OF MINERS AGAINST MERCURY HAZARDS IN THE PERIOD BEFORE 1964

In this period Hg concentrations (mg.m-3) were not regularly monitored at all workplaces in mine areas with native Hg by means of measurements;

workers were assigned to workplaces with increased Hg concentrations without consideration for their previous exposure to Hg;

deficient technical protective measures;

workers did not use personal safety equipment;

the Technical Service assigned workers to workplaces with increased Hg concentrations without consulting the Health Service;

the Health Service did not monitor the state of health of workers during regular exposure;

health supervision did not include biological monitoring.

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HEALTH AND SAFETY PROGRAMME FOR WORKERS EXPOSED TO ELEMENTAL MERCURY AT THE IDRIJA MERCURY MINE

(Kobal, Dizdarevič, 1997)

Regular monitoring of mercury concentrations at workplaces in the pit and smelting plant;

Improvement of technical measures for the reduction of mercury concentrations at workplaces in areas with native mercury;

Continuous use of personal safety equipment by workers exposed to mercury;

Regular and controlled rotation of workers from hazardous to nonhazardous workplaces and reduction of their exposure to mercury from 8 to 6 and even 4 hours daily;

Regular monitoring of external exposure of individual workers and estimation of cumulative monthly external exposure;

Medical surveilance and estimation of workers’ specific ability for work at workplaces with increased concentrations of Hg vapours.

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CONTROL OF WORKING ENVIRONMENT

Air Measurements and Mercury Emission Controls

Instant reading methods (quantification of mercury vapours):

Mercury vapour Meter - Beckmann K-23

range 0.005-0.1 mg.m-1, and 0.003-3.0 mg.m-3

repeatability + 10%

Mercury vapour Indicator - MVI Shawcity

range 0.00 - 2.00 mg.m-3, sensitivity 1g.m-3

repeatability + 5 %

Methods with separate sampling (quantification of total mercury):

acido-oxidising media (KMnO4), hopcalite, activated charcoal, gold traps.

Samples are analised with cold vapour atomic absorbtion spectrometrie (CVAAS) and with neutronic activation analizes (NAA).

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TECHNICAL PRECAUTIONS

Ventilation

This technical measure includes:

efficient front area ventilation and

indirectly a reduction of the temperature of air in the pit.

Q 300 - 400 m3 air ..... air quantitiy

F 10 m2 .... the cross-section of mine’s gallery

T ... (oC) as low as possible (the temperature of the input air)

l = 4F .... (m) the distance between the front area and the ventilation pipe

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TECHNICAL PRECAUTIONS

Ore processing technology

Developement of a new underhand mining method with cemented backfill for extracting mercury ore from carboniferous shale containing native mercury.

With the introduction of a new method of excavation, the mercury concentrations in the pit air decreased for about 30%.

The reduction of the active vaporization surface reduces the emission of vaporized mercury, which essentialy contributes to the reduction of mercury concentrations in pit air.

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TECHNICAL PRECAUTIONS

Calcium polysulphide solution

(CaSn)

Hg + CaSn HgS + CaSn-1

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TECHNICAL PRECAUTIONS

Personal protection equipment

introduction of mask with mercury vapour filter for hazardous works in the smelting plant after 1952;

use of isolating apparatures in particularly hazardous works;

after 1965 the introduction of Drger half-masks with M 105 St. filters at all workplaces in the pit where Hg concentrations in air exceeded 0.1 mg.m-3;

in 1984 AH6-Airstream Racal safety helmets with AS60502 filters comprised of two layers of active charcoal began to be used at all workplaces with increased concentrations of Hg vapours.

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TECHNICAL PRECAUTIONS

Personal safety equipment

Air-purifing helmet AH6-Airstream, RACAL, with mercury absorbing filter

Calculation of useful life of filter AS60502 (estimation of load):

The cumulative load is: Bmax = cn tn

cn ....... daily concentrations of Hg vapours

tn ...... duration of filter’s(miner’s) exposure to a certain Hg concentration

When 1200 points are attained, the filter is to be replaced.

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EXTERNAL MONTHLY EXPOSURE INTENSITY(AMI)The Allowable Monthly exposure Intensity (AMI) is determined on the basis of

the assumption that a worker can work in an area with concentrations of Hg vapours up to 0.1 mg.m-3 air without safety equipment for a period of 8 hours daily for an average period of 26 days (the basis of calculating AMI was the maximum allowable daily exposure to Hg):

AMI = 0.1 mg.m-3 8 hours 26 days/month = = 20.8 points

The allowable monthly exposure intensity is thus assessed at 20.8 points, which a worker is not allowed to exceed while working in hazardous areas. In practise, the mine’s Technical Service calculated the monthly allowable exposure time (MI) in the following way:

MI = cn tn

cn ....... daily concentrations of Hg vapours

tn ....... duration of miner’s exposure to a certain Hg concentration

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MEDICAL SURVEILLANCE OF WORKERS EXPOSED TO ELEMENTAL MERCURY

Target medical examination(screening test)

Evaluation of typical nonspecific symptoms and signs (related to “micromercurialism”);

Evaluation of current health contraindications to Hg exposure;

Timing of evaluation: before, during (once per week) and after exposure.

External exposure evaluation

Annual exposure data• (time, concentration, Alowable Monthly exposure Intensity -

AMI);

Current exposure data• (time, concentration, Monthly exposure Intensity- MI);

Timing of evaluation: before, during and after exposure.

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MEDICAL SURVEILLANCE OF WORKERS EXPOSED TO ELEMENTAL MERCURY

Biological monitoring

Cumulative internal dose evaluation

Urine mercury: morning urine, 18 or 24-hour urine samples;

timing of evaluation: before exposure.

Current internal dose evaluation

Urine mercury: post-shift urine spot samples;

timing of evaluation: during exposure 1 - 2 times per week;

Blood mercury (workplaces with high mercury concentrations);

timing of evaluation: during exposure - at the end of the week.

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MEDICAL SURVEILLANCE OF WORKERS EXPOSED TO ELEMENTAL MERCURY

Biological monitoring

Our recommended temporary Health based Biological Limit Value (BLV)

BLV for workers intermittently exposed to Hg - 4 hours per day at average pulmonal ventilation 27 L.min-1 (Kobal 1991).

Blood mercury: 35 g/L

Urine mercury*: 60 g/L at 68% confidence limit100 g/L** (upper limit) at 95% confidence limit135 g/L** (upper limit)

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* Correction of urine mercury concentration for specific gravity 1024 (Barber, Wallis 1986).

** U-Hg prediction based on B-Hg value 35 g/L,

yU-Hg= 1.35 x + 14.3, r = 0.68, P = 0.000,

standard error of predictions sy= + 37.7 g/L.

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Environmental pollution

The realities of mercury pollution

The ecolgical flap over mercury poisoning has already cut deeply into the metal’s traditional markets ….

Lesson of Minamata Disease

Mercury Contamination in Iraq

Mercury Contamination in the Amazon (Another Minamata?)

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Environmental pollution in Idrija Region (monitored since 1970)

Hg in air Hg in water Hg in sediments Hg in soil Hg in plants Hg in animals Hg in humans Hg in old dust

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Environmental pollution in Idrija Region

500 years of mining activity

3.000.000 m3 of ore and gangue

total production of 150.000 tons of Hg 110.000 tons (commercial Hg ) 40.000 tons (disipated into the

environment, i.e. 20 kg Hg/day)

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Hg production in Idrija Mercury Mine 1490 - 1995 (Mlakar 1974, Cigale 1997)

PeriodOre (t) Hg in ore (%) Recovery

(%)Hgcomm (t)

1490-1580 36 000 1.00 50 1801509-1785 217 867 17.00 65 24 0741786-1945 5 892 113 1.48 75 59 3501946-1960 1 871 054 0.42 85 6 6931961-1977 3 957 911 0.23 91 9 2301983-1995 231 279 0.24 92 5471490-1995 12 206 224 100 074

Total Hg production in Idrija Mercury Mine 1490 - 1995 (Cigale 1997)

Ore (t) Hg in ore (t) Hgcomm (t)Hg production 12 206 224 134 313 100 074Hg (cinn. & other prod.) 551 508 10 516 7 618TOTAL 12 575 732 144 829 107 692

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Average mercury concentrationsin the air in Idrija

Year ngHg/m3 air

1971 20001972 45351974 4351986 2901990 571991 2501992 1011994 21581999 202000 1420012002

1012

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Distribution of Mercury in the Athmosphere over Idrija (M. Gosar et al., 1997)

Idrija

H g( n g / m )3

FR O M :G osar, M ., P irc, S ., Š a jn , R ., B idovec, M ., M ashyanov, N .R . & S holupov S .E . 1997: D istribution o f m ercury in the a tm osphere over Idrija , S loven ia , E nvironm enta l geochem istry and hea lth , 19, 101-110.

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Average mercury concentrations in soil in Idrija (mgHg/kg)

Earth crust 0.02

Slovenia 0.16

IDRIJA

1970 (Byrne & Kosta) 52 - 315

1991 (Hess) 0.2 - 148

1999 (Mercury Mine) 4 - 222

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Hg in soil (Gosar M., PHD thesis, 1997)

IDR IJ A

SP . IDR IJ A

Hg in soil

data from H ess, 1992geochem ical m ap from G osar., 1997 (U npubl. PhD . thesis)

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Pollution of Pit and Surface Waters

Pit waterPeriod ngHg/ L mgFetot/ L mgSO4/ L1994 2 - 547 0.02 - 15 16 - 64001999 1102 1.97 16472000 428 1.11 8882001 468 1.44 8942002 428 1.73 588MAC 10.000 2.0 1000

Location Year ngHg/L mgFe/L mgSO4/L1999 14 0.06 4Idrijca River –

200 m before pit water outlet 2002 34 0.04 81999 1102 1.97 1647

Pit water2002 428 1.73 5881999 103 0.08 34Idrijca River –

500 m after pit water outlet 2002 62 0.07 18unpolluted underground waters (Roseet.al.,1979)

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Mercury (dissolved) in the Surface Water of Gulf of Trieste(M. Horvat et al. Sept. 1995, surface water,)

13.25 13.30 13.35 13.40 13.45 13.50

45.30

45.35

45.40

45.45

45.50

Piran

Koper

TRIESTE

SLOVENIA

ITALY

N

Isonzoriver

Dragonja 0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

0 10 km

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Smelting plant1860 - 1970

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Smelting plant1980 - 1995

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Mercury in Air - smeltery

Year ngHg/m3 air Author

1971 20 000 Byrne& Costa 1970

Inst.Jožef Stefan 1969-71

Kavčič 19741972 8 500

1986 ~290 Mercury Mine

1990-92 ~150 Miklavčič

1994 4 078 Mašjanov & Šolupov

1998 400 – 3 000 Mercury Mine

1999 114 Mercury Mine

1991 1 000 WHO*

*the limit value of Hg in air for residential areas

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Smelting plant today

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Remediation

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Pront area – outcrop of ore deposit

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Pront area (1999)

Location mgHg/kg soil

ngHg/m3

air

non contaminated area

4.03 4.4

Pront area 721.7 10.2

Near smeltery smokestack

212.9 114.5

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Mercury in plants

Plant ngHg/g fresh weightCarrot 800 – 89Onion 68,7 – 3,9Potatoe 37,4 – 3,6Bean 16,9 – 1,3Beetroot 13,9 – 1,9Tomatoe 17,1 – 3,3Cabbage 10,8 – 9,3

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Mercury in animals tissues

Animal Hgtot (ppm) MeHg (ppm) MACFish 1.45 0.92 0.50

Roe deer tissues and hairs: 100-times highervalues of Hgtot and MeHg in comparison withcontrol group.

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Conclusions

Results Environment rehabilitation

measures Reduction of loads on the

population

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