New Proposed Silica Standard

Jon NixonSafety Specialist

CenterPoint Energy

Acronyms

Permissible Exposure Limits (PELs) Time Weighted Average (TWA) American Conference of

Governmental Industrial Hygienist (ACGIH)

National Institute for Occupational Safety and Health (NIOSH)

Silica

Silicon + Oxygen = SiO2

One of the most abundant compounds Two Forms

› Crystalline› Non-Crystalline

Found in nature as quartz

Silica

Non-Crystalline (amorphous) Crystalline

› Quartz› Crystobalite› Tridymite

Uses

Glass Filler for:

› Paints› Plastics› Rubber

Fiber Optics

Operations

Glass Workers Construction Work Utility Work Sandblasting Quartz Mining Masonry Work Demolition

Portland Cement

How many will be affected?

~ 2.2 Million workers in the U.S.› 1,850,000 in Construction› 320,000 in General Industry/Maritime

Health Effects

Essentially non toxic› LD50 of 5,000 mg/kg

Silica Dust can lead to:› Silicosis› Bronchitis› Cancer

Silicosis 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

LungsSilica Exposure

Typical Healthy

LungsSilica Exposure

Silica Exposure

Acute vs Accelerated vs Chronic Concentration Duration Particle Size

Acute Silicosis

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

Accelerated Silicosis

Shorter exposure than Chronic, 5-15 years

Higher concentration Progresses after employee is removed

from the exposure source

Chronic Silicosis

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

History 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

History

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

History

OSHA’s National Emphasis Program› NEP Launched 1/24/2008› Included:

Compliance Enforcement Consolation Training and Outreach through the OSHA Web-

site Standard Development

Regulations

General Industry› 1910.94

(Ventilation)› 1910.1000 Table

Z-3 (The Z Table)

Regulations

Shipyard Industry› 1915.34

(Mechanical paint removal)

› 1915.1000 (The Z Table)

Regulations

Construction Industry1926.55 (Appendix A Dusts)

1926.57 (Ventilation)

Regulations

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

OSHA’S Proposed Rule

Two proposed standards:› One for General Industry/Maritime› One for Construction

Why are they considering a change?

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

Why are they considering a change?

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.

Why are they considering a change?

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] 

Why are they considering a change?

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

What are other countries doing?

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

OSHA’s Proposed Rule 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.

Exposure Assessment

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 Sampling Method

NIOSH Method 7500 http://www.cdc.gov/niosh/docs/2003-

154/pdfs/7500.pdf

NIOSH Sampling Method

NIOSH Sampling Method

Methods of Controls

Methods of Control

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

Methods of Control

If blasting, use alternative media Ventilation Wet Method PPE

What is CNP doing?

What are we doing?› Monitoring the “situation”› Gathering information

Historical Sampling Data Field Interviews

› Preparing for NEAs

Where can I get more info?

OSHA› https://

www.osha.gov/dsg/topics/silicacrystalline/additional_info_silica.html

NIOSH› http://

www.cdc.gov/niosh/npg/npgd0552.html

Questions?

Thank you for your attention and time.

Jon Nixon CenterPoint Energy 713.967.7073