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Information on the Regulatory Treatment of Styrene


United States

U.S. Environmental Protection Agency (EPA)

The EPA's Integrated Risk Information System (IRIS) Database currently provides styrene oral and inhalation concentration levels considered to be safe, and states that EPA's classification of styrene for carcinogenic potential is still under review. The IRIS is a widely used reference in developing environmental regulations, reflecting EPA's official position with regard to the carcinogenicity or toxicity of a substance. On January 2, 1998 the EPA announced the start of an IRIS review of styrene health effects data. When completed, most likely in 2002, the results of the review will be added to the IRIS database. This will include a formal review by EPA of all health-related studies and a determination whether or not styrene should be classified to any degree as a carcinogen.

NOTE: Within the U.S. EPA's web site there currently is a variety of interpretations of the health effects of styrene, including lists by certain program offices identifying styrene as a classified carcinogen. The styrene industry has worked to address and correct these errors; particularly as the EPA looks to IRIS as the agency's valid listing of health effects information. The use of IRIS as a definitive reference on the health effects of styrene is recommended.

The US Occupational Safety and Health Administration (OSHA)

OSHA regulates styrene on the basis of avoidance of narcosis in the work place. OSHA chose not to classify styrene as a carcinogen in the 1989 Air Contaminant Rulemaking, concluding that "current evidence on styrene's carcinogenicity does not support its classification as a carcinogen." In that rulemaking, OSHA mandated a permissible exposure limit (PEL) for styrene of 50 parts per million (ppm) over an eight-hour time-weighted average (TWA), with a short-term exposure limit (STEL) of 100 ppm for any 15-minute period. A later court action unrelated to styrene voided the 50 ppm PEL, which reverted back to the pre-1989 standards of 100 ppm TWA and 200 ppm STEL. However, in February 1996, four styrene industry trade associations entered into a precedent-setting arrangement with OSHA to voluntarily adhere to the 50 ppm level set by the 1989 PEL.


The US Food and Drug Administration (FDA)

The FDA closely monitors the use of food additives or substances that may migrate into foods from packaging, preparation, or serving materials, and sets Acceptable Daily Intake (ADI) levels for these substances. The agency has approved styrene for use as a food additive to enhance taste (in chewing gum, for example). FDA also approves the use of products in which there is a potential for the migration of styrene monomer. Polystyrene food service and packaging materials, for example, must meet strict guidelines that determine a maximum safe allowable migration level for a substance that ensures the consumer's safety and health.

Individual State Regulations

The proposed or promulgated health-based air regulations for styrene vary dramatically from state to state. Many of the more stringent state air standards for styrene are based on the US EPA's erroneous listing of styrene as a probable carcinogen in its 1989 Health Effects Assessment Summary Table (HEAST). Even though that listing was later corrected, SIRC continues to address the inappropriate use of this reference by numerous state agencies as a justification for treating styrene as a carcinogen.

California's Safe Drinking Water and Toxic Enforcement Act of 1986 -- better known as Proposition 65 -- requires that the state publish a list of those chemicals "known to the state" to cause cancer or reproductive toxicity. Currently styrene has not been listed under Proposition 65 as a carcinogen or reproductive toxicant.



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