Transcript New Perposed Silica Standard

 Permissible
Exposure Limits (PELs)
 Time Weighted Average (TWA)
 American Conference of
Governmental Industrial Hygienist
(ACGIH)
 National Institute for Occupational
Safety and Health (NIOSH)
Silicon + Oxygen = SiO2
 One of the most abundant compounds
 Two Forms

› Crystalline
› Non-Crystalline

Found in nature as quartz
Non-Crystalline (amorphous)
 Crystalline

› Quartz
› Crystobalite
› Tridymite
Glass
 Filler for:

› Paints
› Plastics
› Rubber

Fiber Optics
Glass Workers
 Construction Work
 Utility Work
 Sandblasting
 Quartz Mining
 Masonry Work
 Demolition


~ 2.2 Million workers in the U.S.
› 1,850,000 in Construction
› 320,000 in General Industry/Maritime

Essentially non toxic
› LD50 of 5,000 mg/kg

Silica Dust can lead to:
› Silicosis
› Bronchitis
› Cancer
Disabling and sometime fatal lung
disease with no current cure
 Due to inhalation of silica dust
 Characterized by:

› Shortness of breath
› Cough
› Fever
› Cyanosis (bluish skin)
› Scaring in the lungs
https://www.youtube.com/watch?v=6FezczBUnI0
Typical Healthy
Lungs
Silica Exposure
Typical Healthy
Lungs
Silica Exposure
Acute vs Accelerated vs Chronic
 Concentration
 Duration
 Particle Size

Develops after 1 to 3 years of exposure
at a very high concentration
 Symptoms may show as early as 7
months
 Cough, weight loss, and extreme fatigue
 Liquid in the alveoli
 Fatal with in 2 years

Shorter exposure than Chronic, 5-15
years
 Higher concentration
 Progresses after employee is removed
from the exposure source

Long term exposure, 20-45 years, to
develop
 Dust with 10% or greater silica
 Little to no symptoms for the first 20 years
 Shortness of Breath, cough, fever
 Bluish lips/ear lobes
 Chest Pain

OSHA current standards adopted in 1971
 OSHA had to promulgate PELs

› 425 were created

Silica’s PEL was derived from
› Walsh-Healy Public Contacts Act
› Contract Work Hours & Safety Standard’s Act
› ACGIH

In 1974 NIOSH recommended that the
occupational exposure be controlled so
that no worked is exposed to:
› TWA greater than 50 µg/m3
 10 hour workday
 40 hour work week

OSHA’s National Emphasis Program
› NEP Launched 1/24/2008
› Included:
 Compliance Enforcement
 Consolation
 Training and Outreach through the OSHA Website
 Standard Development

General Industry
› 1910.94
(Ventilation)
› 1910.1000 Table
Z-3 (The Z Table)

Shipyard Industry
› 1915.34
(Mechanical
paint removal)
› 1915.1000 (The Z
Table)
Construction
Industry1926.55
(Appendix A
Dusts)
 1926.57
(Ventilation)


Current exposure limits
› Adopted for decades ago
 U.S. National Toxicology Program, International
Agency for Research on Cancer, and NIOSH
have identified respireable crystalline silica as
a human carcinogen
› PELs are difficult to understand
› Based on older sampling methods
› Shipyard workers PEL is 2x general industry

Two proposed standards:
› One for General Industry/Maritime
› One for Construction

OSHA estimates current lung cancer
deaths from exposure to silica over a 45
year working life averages:
› Between 13 – 60 General Industry deaths per
1,000 workers
 average exposure is estimated to be ~
100µg/m³
› Between 37 – 635 Construction & Shipyard
deaths per 1,000 workers
 Average exposure is estimated to be ~
between 250 – 500 µg/m³
Supreme Court: “significant risks are
present and can be eliminated or
lessened by a change in practices”
before promulgating any health or
safety standard.
 After standard implemented:

› Estimate between 6 – 26 deaths per 1,000
workers.

Current Permissible Exposures Limits (PELs)
are formulas that many find hard to
understand:
› PEL (respirable fraction) = 10 ÷ [% quartz + (%
cristobalite × 2) + (% tridymite × 2) + 2]
› PEL (total dust) = 30 ÷ [% quartz + (%
cristobalite × 2) + (% tridymite × 2) + 2]
Constriction/shipyard PELs are obsolete
particle count limits
 Construction/Shipyard formulas are
about 250 µg/m3
 General Industry formula is equal to
about 100 µg/m3


Canada
› Alberta – 25 µg/m3
› Nova Scotia – 25 µg/m3
› Saskatchewan – 50 µg/m3
Italy 25 - µg/m3
 Ireland – 50 µg/m3
 Netherlands – 75 µg/m3

Establishes new PEL of 50 μg/m3 = 0.05
mg/m³
 Includes provisions for:








Measuring worker exposures to silica;
Limiting access to areas where workers
could be exposed above the PEL;
Use of dust controls;
Use of respirators when necessary;
Medical exams for highly exposed
workers;
Worker training;
Recordkeeping.

Conduct an initial exposure assessment
› This will determine if:
 EE’s are exposed to Silica levels at or above
the action level
 Whether or not engineering/administrative
practices are required to reach the PEL

Determine if periodic or additional
monitoring will be needed
NIOSH Method 7500
 http://www.cdc.gov/niosh/docs/2003
-154/pdfs/7500.pdf

Use engineering controls and work
practices to maintain exposure levels
at/or below the PEL
 If the employer can show that
engineering controls are not feasible:

› Attempt to reduce the exposure to the
lowest achievable level
› Supplement with PPE
If blasting, use alternative media
 Ventilation
 Wet Method
 PPE


What are we doing?
› Monitoring the “situation”
› Gathering information
 Historical Sampling Data
 Field Interviews
› Preparing for NEAs

OSHA
› https://www.osha.gov/dsg/topics/silicacryst
alline/additional_info_silica.html

NIOSH
› http://www.cdc.gov/niosh/npg/npgd0552.ht
ml

Thank you for your attention and time.
Jon Nixon
 CenterPoint Energy
 713.967.7073
