11 training OSHA silica presentation 3 31 10 larry joswial MPH

Silica
Larry Joswiak, MPH
March 31, 2010


Silica
1926.55 – Mineral Dusts
• It’s not just dust…It’s
silica
• Silica NEP (National
Emphasis Program)
January 24, 2008
• Silica LEP (Local
Emphasis Program)
October 1, 2009
Targets specific
General Industry SIC
Codes


What is silica?
• Mineral – crystalline or amorphous forms
– Crystalline most hazardous

• Crystalline- 3 forms
– Quartz, cristobalite, tridymite

• Quartz – most common
Major component of soils and readily found in rock
Granite ~30% quartz
Shale ~ 20% quartz

Beach sand – nearly pure quartz


Silica Exposure Activities
• Sand/abrasive
blasting
• Tuckpointing
• Jack hammering
concrete
• Brick/block cutting
• Concrete cutting &
drilling
• Demolition

•
•
•
•
•

Stone cutting
Foundry work
Tunneling
Rock drilling
Quarrying


What is silicosis?
• A disabling and often fatal lung disease
caused by breathing very small

“respirable” particles of crystalline silica
• >14,000 deaths since 1968
• >200 deaths each year in the U. S.



Silicosis
• Chronic/Classic
– Occurs after 15 – 20 years of moderate to low
exposure

• Accelerated
– Occurs after 5 – 10 years of high exposures

• Acute
– Occurs after a few months or as long as 2 years to
extremely high concentrations


Other Health Effects of Silica
Exposure
• Lung cancer
– IARC Group 1: Carcinogenic to Humans

• Tuberculosis
• Chronic Obstructive Pulmonary Disorder
– Bronchitis, Emphysema

• Immunologic Disorders & Autoimmune
Disease

• Renal Disease


•
•

Diseased and healthy lung
Compare these sections cut from a diseased lung with large cavities (left) and a
pink, healthy lung (right). The diseased lung shows a case of miner’s phthisis (also
known as silicosis) which has led to tuberculosis. Quartz dust is inhaled by miners,
and trapped in the lungs causes silicosis making the victim more susceptible to
diseases such as tuberculosis and pneumonia.


Current Respirable Silica
Quartz Exposure Limits
OSHA (PEL)
Construction

OSHA (PEL)
General Industry

250 mppcf
% silica + 5

10 mg/m3
% silica + 2

ACGIH (TLV)
Quartz:

0.025 mg/m3
Cristobalite: 0.025 mg/m3


AIR SAMPLING EQUIPMENT
Personal
Air Pump
with
Cyclone


PERSONAL SAMPLING


OSHA Construction
Industry

OSHA General
Industry

ACGIH
Construction & General
Industry

Employee
Name

% Silica

Time

Sampled
(minutes)

8 HR
TWAa
(mppcf)e

PELb
(mppcf)e

8 HR
TWAa
(mg/m3)d

PELb
(mg/m3)d

8 HR
TWAa
(mg/m3)d

ACGIH
TLVf
(mg/m3)d

Grinder 1

5.5

464

19.6

23.8

1.96

1.4

1.96

0.025

Grinder 2

4.5

474

20.2

26.3

2.02

1.54

2.02

0.025

Laborer1

3.6

463

3.5

29.1

0.35

1.79

0.35

0.025

Laborer 2
Air hose

3.8

478

5.7

28.4

0.57

1.72

0.57

0.025

a

d

mg/m3 – milligrams per cubic meter of air

b

8-hour Time Weighted Average
OSHA Permissible Exposure Limit
c
Employee exposure for time sampled

e

mppcf – million particles per cubic foot of air

f

TLV – American Conference of Governmental Industrial Hygienist’ Threshold
Limit Values

Concrete Cutting (Dry) Example
•
•
•
•
•

6 % silica
2.27 mg/M3 PEL
16.3 mg/M3 (68 min)
2.31 mg/M3 8 hr TWA
8 hour severity
102% of PEL
• EXCEEDED PEL

• Gas saw dry cuts hole
in concrete manhole
• 718 % of PEL for 68
minute sample time


30% Crystalline Silica Quartz




10% Crystalline Silica Quartz

8 % Crystalline Silica Quartz

10% Crystalline Silica Quartz



Silica Conclusions
• Dry operations: High
likelihood of silica dust
overexposure
• Wet operations: Low
potential for silica dust
overexposure
• Exposures may be
multiplied by factors such
as interior workplace and
corner location.