Silica. It’s Not Just DustRick Gleason, CIH, CSPOctober 8, 2009

Rick Gleason, CIH, CSPrgleason@u.washington.edu

(206) 856-6660

1. History of Silica2. L & I Regulations3. UW Airborne Silica Sampling4. Questions

Hawk’s Nest TunnelWest Virginia, 1932

Where is it found?

In Nature

• Beach sand• Granite• Sandstone• Clays• Diatomaceous

earth

In Industry

• Mining• Quarrying• Stone cutting• Sand blasting• Concrete & mortar work• Cutting, grinding, drilling,

sanding

Silica Exposure

• Size of particles - can it be inhaled deep into the lung?

• % silica in the dust

• Concentration

• How much time exposed each day?

• How often exposed?

What is Sililcosis• A Fibrotic disease of the lungs – it scars the lung tissue

• Lung is less flexible and has less area for the exchange of oxygen

• Makes it difficult to do hard work and breath

• May be from short-term high exposure (acute) or long-term lower exposure (chronic)

Silicosis

•Incurable and irreversible

•May progress even after exposure has stopped

•This is completely preventable!

Risk of Developing Silicosis*

Dust Conc. Years in the Pottery Industry

0-9 10-19 20-29 30-39 > 40

low 0% 0.4% 1.5% 0% 0%

mod. low 0.3 3 24 51 85

mod. high 0 7 20 59 71

high 4 19 48 71 80

* Flinn et al, 1939

Other Health Problems Related to Silica Exposure

• Lung Cancer

• More susceptible to tuberculosis

• Maybe immune system disease

• Kidney disease

Silica Exposures Labor and Industries Rules

Standard 10 (d) Sanitation and Cleanliness

Labor and Industries Industrial Hygiene Codes

What year???

October 1, 1938

Video: Stop Silicosis1938

Available from the L & I DOSH Video Lending Library

UW Research –ExposureWhat did we find?

• 1,375 personal quartz samples

• Geometric mean quartz concentration:– 0.13 mg/m3 – compare to Washington PEL of 0.1 mg/m3

00.05

0.1

0.15

0.2

0.25

0.3

0.35

Co

nc

. (m

g/m

3 )

up to 2 hr 2-6 hr over 6 hr

Sampling Time

Quartz Concentration by Data Source

Private

Research

Regulatory

9%

36%

55%

Exposure by Tool Used

Tool: abrasive blaster

No.= 57 0.28 mg/m3

Range 0.01 – 832.71 mg/m3

Tool: hand-held saw

No.= 65 0.13 mg/m3

Range <0.01 – 14.15 mg/m3

Tool: table saw

No.= 51 0.07 mg/m3

Range 0.01 – 2.75 mg/m3

Tool: walk-behind saw

No.= 33 0.09 mg/m3

Range 0.02 – 1.64 mg/m3

Tool: rock drill

No.= 93 0.21 mg/m3

Range <0.01 – 16.00 mg/m3

Tool: jackhammer/chipping gun

No.= 178 0.15 mg/m3

Range <0.01 – 3.86 mg/m3

Tool: broom/shovel

No.= 49 0.03 mg/m3

Range <0.01 – 1.19 mg/m3

Tool: surface grinder

No.= 123 0.28 mg/m3

Range 0.01 – 18.20 mg/m3

Tool: tuckpoint grinder

No.= 102 0.61 mg/m3

Range 0.01 – 76.10 mg/m3

Tool: concrete mixer

No.= 32 0.04 mg/m3

Range 0.01 – 0.55 mg/m3

Tool: backhoe/excavator/bulldozer/bobcat

No.= 28 0.01 mg/m3

Range <0.01 – 0.12 mg/m3

Tool: road mill

No.= 48 0.11 mg/m3

Range 0.01 – 16.10 mg/m3

Environment

Open

Enclosed

Confined

No.Conc.

274 0.08

235 0.15

15 0.33

Project Type

Highway

N= 294 0.13 mg/m3 17%

Industrial/Commercial

N = 465 0.09 mg/m3 12%

Huge Variability in Exposure

• Half of samples were below PEL (0.1 mg/m3)

• 13% of samples were over 10 times the PEL!

• These extremely high exposures represented 9 of 12 tools

Prioritzing for Control

1. Abrasive blasting and grinding

2. Drilling, jackhammering, and chipping

3. Road demolition

4. Concrete cutting

5. Clean up and cement mixing

6. Heavy equipment demolition

Exposure Summary

• Control should focus on task and tool

• Degree of enclosure and type of project are also important

• There is a problem – we need to move on to controlling it!

Vacuum on Tools

• 90% exposure reduction is possible

• LEV may reduce exposures below PEL

Vac

Flex Grinderand ShroudMetabo Grinder

Sawtec Shroud

Water Control• Typically very effective

• High exposures can potentially result if:

- Water application rate is low and/or

- Work is enclosed

• Common for cutting - some other applications

• Problematic in some settings

•Keep spray close to the source•Keep spray continuous during dusty operations

•Keep water reservoir filled

•Maintenance needed to avoid clogging

Water Control

Respirator Selection by Protection Factor

020

4060

80100

% N

ot

Pro

tec

ted

none

5 x TLV

10 x TLV

100 x TLV

**Based on monitoring data > 6 hours

*

Summary

• There is a problem – we need to move on to controls!

• Respirators currently used aren’t always protective enough

• We need to implement other controls or controls in combination with respirators

More information:http://depts.washington.edu/silica/