On March 25, 2016, the Occupational Safety and Health Administration (OSHA) published the long awaited respirable crystalline silica standard which they say will affect 2 million construction workers who drill, cut, crush, or grind silica-containing materials such as concrete and stone, and 300,000 workers in general industry operations such as brick manufacturing, foundries, and hydraulic fracturing. This standard will be effective on June 23, 2016, with some of the provisions taking effect at a later date.  It should be noted that it is being legally challenged through the courts and it is possible the standard may be quite different after these legal processes.

OSHA published two standards for respirable crystalline silica; one for the general and maritime industries and the other applicable to the construction industry.  In this 3-part series we will address the current provisions of the new standard applicable to the general and maritime industries. These posts are not meant to be the complete regulatory text of the standard, but rather a superficial summary.  Employers should review the standard from the OSHA website.

Silica is a mineral that can be found in the amorphous and crystalline state, the main difference is the crystalline state has atoms arranged in a repeating pattern.  Crystalline silica is mainly found in the forms of quartz, cristobalite, and tridymite and is known to cause health effects such as silicosis, lung cancer, chronic obstructive pulmonary disease (COPD), and kidney disease[i].

Currently, OSHA’s permissible exposure limit (PEL) for respirable crystalline silica is not a value but rather a formula (contained in 29 CFR 1910.1000 Table Z-2) used to estimate the employee’s exposure based on the silica percentage found in an air monitoring sample.  This exposure limit was adopted from the 1968 Threshold Limit Values recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). 

For example, if dust collected in the working atmosphere is 100% quartz, OSHA’s permissible exposure limit would be 100 µg/m³ (100 micrograms per cubic meter of air).  The value will be lower if crystalline silica in the cristobalite and/or tridymite form are also present.  If 0% is found in the sample, the exposure limit is 5 mg/m³, which is the same as the PEL for particulates not otherwise classified in the respirable range[ii]. These values are based on an 8 hour time weighted average.  In 1974, the National Institute for Occupational Safety and Health recommended that employees should not be exposed to respirable crystalline silica levels above 50 µg/m³ without any kind of protection[iii].  Under the new standard, the PEL will not be based on a formula but rather a specific number.

New Permissible Exposure Limit

The new PEL is 50 µg/m³ with an action level of 25 µg/m³.  These values will take in consideration all forms of crystalline silica (the sum of all types of crystalline silica present in the work atmosphere collected in the air sample). Does that mean employers need to do air monitoring, even if prior testing were done?  The short answer is… it depends. 

Using a hypothetical example, let’s say that one of the tasks at ABC Company involves the use of silica sand that is 100% quartz (documentation is available showing that only the quartz form is present). The safety manager of the company hired an industrial hygienist three years ago to do a series of assessments to determine the employee’s personal exposures to crystalline silica.  The production process, controls, and production volume are the same as during the assessments.  If the safety manager has the knowledge, she/he could review the report and re-interpret the laboratory results (if they were included in the report) or ask the industrial hygienist to review the assessment and compare the results to the new limits.  If the company has never done any kind of assessment in the past, the new standard requires employers to perform an initial assessment or a performance based option (this will be covered in our next blog).  How about if ABC Company only has industrial hygiene data related to quartz but not the other forms of crystalline silica; and the company does not have any objective data indicating otherwise?  In this case, re-assessment of the work areas would be recommended.

Our next post on this topic will address what requirements apply if exposures are above the action level or the PEL.

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[i] NIOSH Hazard Review: Health Effects of Occupational Exposure to Respirable Crystalline Silica.

http://www.cdc.gov/niosh/docs/2002-129/pdfs/2002-129.pdf

[ii] 29 CFR 1910.1000 Table Z-1

[iii] NIOSH Criteria for a Recommended Standard: Occupational Exposure to Crystalline Silica.

https://www.cdc.gov/niosh/docs/75-120/