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Legislative Issues: Measuring Permissible Exposure for Silica

December 1, 2001
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How should exposure to silica in the workplace be measured? Until earlier this year, no court had addressed the issue of determining the correct method for calculating actual workplace exposure to silica under regulations issued by the U.S. Occupational Safety and Health Administration (OSHA), which is part of the Department of Labor. It has been found that overexposure to silica, including overexposure in the work environment, can cause silicosis, which may lead to permanent lung damage and disability.

In 1971, OSHA issued what has become known as Table Z-3, which is found in Part 29 of the Code of Federal Regulations and relates to the amount of allowable exposure of workers to certain mineral dusts, including silica. Controversy has existed as to how the permissible silica level should be calculated. One aspect of this controversy is whether the measurement of the air in a workplace should pertain only to silica itself or also to various industrial dust particles that may have silica mixed in them. The OSHA regulations are unclear, and some have interpreted them to mean that dust particles should not be counted.

Exposure Guidelines

OSHA’s Table Z-3 contains a standard for crystalline quartz silica providing that an employee’s exposure in an 8-hour work shift of a 40-hour work week is not to exceed an 8-hour weighed average limit as given in Table Z-3. In turn, Table Z-3 contains a mathematical formula for calculating what is known as the PEL—permissible exposure limit—for various mineral dusts, including those for different categories of silica.

In effect, the PEL represents the maximum amount of a contaminant, such as silica, in the air to which workers may be exposed over a given time period. The PEL formula, as established in OSHA’s regulations, is a sliding scale depending on the percentage of the total respirable fraction of the dust in the air being sampled that is silica.

Accordingly, the PEL for any substance may be lower as the percentage of silica in the dust becomes higher. The lower the PEL, the more difficult it becomes to comply with the applicable OSHA workplace air standard.

Calculating Exposure

One controversy over the Table Z-3 standard for silica is that the regulations contain no method of calculating actual silica exposure. This issue was debated in court when an Ohio-based company was cited by OSHA for failing to properly protect its workers from silica exposure. An OSHA compliance officer claimed that the company had overexposed its workers, but the company denied that claim. The dispute resulted from the use of varying methods to calculate the actual level of silica.

The company appealed OSHA’s imposition of an $8,000 fine to an administrative review panel, which held in favor of OSHA. The company then appealed to a U.S. appellate court, setting up the first judicial review of the calculation method for the silica standard.

The company contended that under the OSHA regulations, OSHA should measure for silica only and is precluded from considering non-silica dust. While the court acknowledged that this approach had some basis in the actual language of the regulations, it found that the practice would, if adopted, fail to recognize the reality of actual workplace exposure. The court accepted OSHA’s contention that silica can be present along with other substances in a dust sample taken for testing. According to the court, the total respirable dust sample is a logical sample for OSHA to use.

Consequently, a silica measurement under Table Z-3 may include non-silica inert dust. The court recognized that the PEL formula is a function for the total respirable dust present in the air, not only the actual silica dust. In formulating its opinion, the appellate court stated that, like most courts, it is reluctant to set aside agency action unless the action is arbitrary, capricious, an abuse of agency discretion or not provided for in a Congressionally enacted statute. In making such a determination, the courts give substantial deference to an agency’s interpretation of its own regulations. The court recognized that there could be more than one reasonable interpretation of OSHA’s silica standard, but if OSHA’s own interpretation was reasonable it would be upheld.

This holding of the court means that all entities using silica in the workplace should make sure that the air in the workplace is regularly monitored under the methods recognized by OSHA. If the silica present in the air exceeds the OSHA standard, steps must be taken to protect employees.

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