The U.S. Occupational Safety and Health Administration (OSHA) regulates styrene on the basis of avoidance of narcosis in the work place. The current OSHA permissible exposure limit (PEL) for styrene is 100 parts per million (ppm), meaning that a worker should not be exposed to more than an average of 100 ppm styrene in air during a regular workday, without respiratory protection. However, under an agreement with OSHA and for added worker protection, SIRC members voluntarily adhere to a styrene PEL of 50 ppm.
In its final Air Contaminants rule of 1989, OSHA mandated a permissible exposure limit (PEL) for styrene of 50 parts per million (ppm). At that time, OSHA also mandated a short-term exposure limit (STEL) of 100 ppm for any 15-minute period. OSHA based the regulation on concern for potential narcotic effects, typical of many solvents at higher exposure levels.
In July 1992, a U.S. Appeals Court voided that 1989 OSHA rule. The Labor Department did not appeal the decision, and therefore its styrene occupational standards reverted back to the pre-1989 standards of 100 ppm TWA and 200 ppm STEL. However, SIRC encouraged its members to continue to comply with the 50-ppm standard as an appropriate exposure level for styrene, regardless of its regulatory status.
In February 1996, SIRC and three* other styrene industry trade associations (American Composites Manufacturers Association, National Marine Manufacturers Association and the International Cast Polymer Association) entered into a precedent-setting arrangement with OSHA to voluntarily adhere to the 50-ppm level set by the 1989 PEL.
Barring any significant new health effects data, or evidence of industry's failure to adhere to the voluntary agreement, it is hoped that OSHA will not need to initiate a new PEL rulemaking for styrene in the immediate future, thus avoiding the need for both government and industry to expend unnecessary time and expense.
* NOTE: At the time the industry proposal was submitted, the American Composites Manufacturers Association (ACMA) was known as the Composites Manufacturers Association, and the International Cast Polymer Association has since merged with the ACMA. A fifth organization, the Composites Institute, was also signed the original proposal, but has since disbanded.
OSHA's Hazard Communication Standard (HCS)
OSHA's Hazard Communication Standard (HCS) requires that companies list all relevant health data on their material safety data sheets (MSDSs). Despite the fact that OSHA does not regulate styrene as a carcinogen, the HCS does require notation of the International Agency for Research on Cancer's (IARC's) "possible carcinogen" classification of styrene (see International Regulation of Styrene) on the MSDS if styrene is present at a concentration of one percent or higher. However, the HCS does not require any specific labeling for products made from or containing styrene or other IARC Group 2B compounds.
The HCS also requires that MSDSs note the American Conference of Governmental Industrial Hygienists (ACGIH) recommended threshold limit value (TLV®) / time-weighted-averages (TWAs). In May 1997, ACGIH established a 20-ppm TLV® / TWA for styrene in place of its existing 50-ppm TLV® guidance. ACGIH indicated it reduced the TLV® after observing mild, subclinical effects on color vision at the 50-ppm level of exposure and below. ACGIH noted that no scientific consensus exists that the subclinical effects on color vision are pathological precursors to color vision or other health impairments. And further, ACGIH determined that styrene was not classifiable as a human carcinogen.
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