CRYSTALLINE SILICA

CRYSTALLINE SILICA

• Silica (Silicon dioxide) is one of the most common chemical compounds found in nature.

• Amorphous silica is common sand.

• The most common crystalline silica is quartz. Tridymite and cristobalite are other crystalline forms used in industry. There are alpha and beta structure forms. Alpha quartz is the most common structure.

CRYSTALLINE SILICA

CRYSTALLINE SILICA

• OSHA has submitted the proposed rule

regulating crystalline silica in general

industry, construction and maritime to the

Office of Management and Budget (OMB)

for review.

• It is expected to be published in the

Federal Register in Summer 2011.

CRYSTALLINE SILICA

• The new standard will update the existing Permissible Exposure Limit, establish controls for additional worker protection and require medical surveillance.

• OSHA recognizes that the PEL for silica is outdated and need to be revised to reflect current sampling and analytical technologies.

CRYSTALLINE SILICA

• Some of the primary exposure concerns in utilities include (but not limited to):

- Abrasive blasting

- Concrete and rock drilling and cutting

- Coal ash and dust

- Refractory removal

- Soil work

CRYSTALLINE SILICA

• The primary health concern from crystalline silica is Silicosis. Can be chronic, accelerated or acute depending upon levels of exposure.

• Listed as IARC-1 carcinogen, ACGIH A2 suspected carcinogen for lung cancer.

• Smoking adds to the lung damage caused by crystalline silica.

• Particle size can run from as large as 250 micrometers to as small as 300-400 nanometers.

CRYSTALLINE SILICA

• Hawk’s Nest Tunnel in WV was one of worst industrial disasters in US history.

• Estimated 700 – 1000 workers out of workforce of 3000 died of silica-related diseases.

• Some deaths were within 1 year of starting job.

CRYSTALLINE SILICA

• The ACGIH TLV for crystalline silica is 0.025 mg/M3 TWA8 as a respirable fraction.

• The NIOSH REL is 0.05 mg/M3 TWA10 as respirable dust.

• A proposed OSHA PEL is 0.1 mg/M3 TWA8 as respirable dust (not confirmed).

CRYSTALLINE SILICA

• The current PEL is based on the silica concentration (quartz) of the dust.

10 mg/M3

-------------

% silica + 2

For Cristobalite and Tridymite, it is ½ the value for quartz.

Construction standard still lists the PEL in mppcf.

CRYSTALLINE SILICA

• NIOSH published a Criteria for a Recommended

Standard for crystalline silica in 1974.

• NIOSH was founded in late 1970. Crystalline

silica was one of the first recommended

standards from NIOSH.

• Exposure limits were based on silica

concentrations of the respirable dust.

CRYSTALLINE SILICA

• ACGIH and NIOSH use the ISO/CEN protocol

for measurement of respirable particles.

• This uses a cut point of 4um.

• OSHA uses a cut point of 3.5um.

• Hopefully, this will be addressed with the new

standard.

CRYSTALLINE SILICA

• Acceptable analytical methods include:

- NIOSH 7500 (XRD)

- NIOSH 7601 (VIS)

- NIOSH 7602 (IR)

- OSHA ID-142 (XRD)

CRYSTALLINE SILICA

• The AEP Silica study examined 501 samples. The results are as follows:

1) Samples exceeding 0.025 mg/M3 – 3.6%

2) Samples exceeding 0.05 mg/M3 – 2.4%

3) Samples exceeding 0.1 mg/M3 – 1.2%

4) Samples exceeding calculated PEL – 1.0%

CRYSTALLINE SILICA

5) Samples where silica is above detectable levels – 5.8%

6) Samples where respirable dust is above detectable levels – 59.1%

7) Samples where respirable dust is above PEL of 5.0 mg/M3 - 0.8%

All samples were analyzed by NIOSH 7500

CRYSTALLINE SILICA

• Of the samples that exceeded the 0.1 mg/M3 level:

1) Coal yard work (0.89 mg/M3), respirable dust was 96 mg/M3, exact work not specified.

2) Operations work (0.25 mg/m3), respirable dust was 27 mg/m3, exact work not specified.

3) Glass bead blasting (1.0 mg/M3), beads may have added to overall silica levels.

CRYSTALLINE SILICA

4) Soil processing at a landfill during a

construction project (0.11 mg/M3), silica

concentration was 10.3%.

5) 2 samples where a chipping gun was

used to remove refractory (0.18 and 0.12

mg/M3).

CRYSTALLINE SILICA

• From the coal-related exceedances, both had

high respirable dust concentrations.

• Blasting and chipping would be expected to

have high exposure potential, precautions

should have been taken prior to start of job.

• Additional controls were added to the soil

processing after the exceedance was noted.

CRYSTALLINE SILICA

• OSHA has cited several companies since a National Emphasis Program in 2008. The citations include:

- overexposure to respirable silica

- lack of respiratory protection program

- lack of training on hazards of silica

- lack of written HAZCOM program for employees exposed to silica

CRYSTALLINE SILICA

• Engineering controls include:

1) Substitution to a less hazardous product

2) Use of wet saws

3) Dust collection systems

4) Local exhaust ventilation

5) Use of water as dust control

CRYSTALLINE SILICA

• Administrative controls include:

1) Understanding of the work practices that can lead to silica exposure

2) Training programs

3) Employee rotation (if permitted)

4) Good hygiene when working around silica

5) Good hygiene after working around silica

CRYSTALLINE SILICA

• Personal Protective Equipment (PPE) – good option as a temporary control, last choice for permanent control.

• PPE includes:

1) Disposal or washable coveralls (laundry notification?)

2) Respiratory protection varies depending on work performed.

CRYSTALLINE SILICA

3) The P-100 filter is the proper filtration.

4) The OSHA Ventilation Standard -(1910.94 & 1926.57) contains specific respiratory protection requirements for abrasive blasting operations.

The proper respirator for abrasive blasting is the Type CE Respirator.

CRYSTALLINE SILICA

• Type CE abrasive-blast supplied-air respirators are the only respirators suitable for use in abrasive-blasting operations. The approved types are:

- continuous-flow respirator with a loose-fitting hood (APF – 25, 1000 if manufacturer rated)

- continuous-flow respirator with a tight-fitting facepiece (APF – 50 for half-face, 1000 for full-face)

- positive-pressure respirator with a tight-fitting half-mask facepiece (APF – 50)

- pressure-demand or positive-pressure respirator containing a tight-fitting full facepiece (APF – 1000)

CRYSTALLINE SILICA

CRYSTALLINE SILICA

CRYSTALLINE SILICA

• Trona – used in FGD systems to mitigate

SO3 is less than 2% silica as listed on

MSDS.

• Personal air monitoring has not indicated

excessive levels of silica exposure.

CRYSTALLINE SILICA

• While it is not certain as to the degree the new silica standard will affect the electric industry, the overall impact should not be dramatic.

• Coal dust and ash should not be of concern at the normal levels to which a worker is subjected to on a daily basis.

• Levels where the respirable dust PEL could be exceeded may have silica exceedances, also.

CRYSTALLINE SILICA

• While the health effects of silica can be

severe, it is entirely preventable with

proper engineering controls, administrative

controls and PPE.

• OSHA has a wealth of information

available on crystalline silica on their

website – osha.gov

CRYSTALLINE SILICA

ANY QUESTIONS????