NTP-CERHR monograph on the potential human reproductive and developmental effects of styrene

The National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR) conducted an evaluation of the potential for styrene to cause adverse effects on reproduction and development in humans. Styrene was selected for evaluation because of (1) public concern about styrene exposure and (2) recently available exposure studies. Styrene (ethenylbenzene; CAS RN: 100-42-5) is a high production volume chemical (a million pounds or more produced each year) and is used in the production of polystyrene resins and as a co-polymer with acrylonitrile and 1,3-butadiene. Styrene is found in items such as foam cups, dental fillings, matrices for ion exchange filters, construction materials, and boats. It is also used in protective coatings, reinforced glass fiber, agricultural products, and as a food additive. The Food and Drug Administration regulates styrene for use as a synthetic flavoring substance and as a component of polymers in contact with dry food, and also regulates the amount of residual styrene monomer allowed in polystyrene intended for use in contact with food. The public can be exposed to styrene by ingesting food or drink that has been in contact with styrene polymers or through inhalation of polluted air and cigarette smoke. The results of this evaluation on styrene are published in a NTP-CERHR monograph that includes: (1) the NTP Brief, (2) the Expert Panel Report on the Reproductive and Developmental Toxicity of Styrene, and (3) public comments received on the expert panel report. The NTP reached its conclusion of negligible concern for adverse developmental and reproductive effects resulting from styrene exposures in humans based on information presented in the NTP-CERHR Expert Panel Report on the Reproductive and Developmental Toxicity of Styrene and the public comments on that report. This conclusion is based on estimated exposures in both the general population and in people whose occupation involves styrene exposure. The expert panel estimated styrene exposure in the general U.S. population to be less than 0.3 microg/kg body weight/day in nonsmokers and 3.51 and 2.86 microg/kg body weight/day in smokers ages 12-19 years and 20-70 years, respectively. Average occupational exposures are estimated to range from 1,400-52,000 microg/kg body weight/day. Studies in humans show no evidence that occupational exposures or exposure of the general population to styrene adversely affect reproduction or development. Further, data from experimental animal studies show no adverse reproductive or developmental effects at styrene doses far above human exposure levels. The NTP will transmit the NTP-CERHR monograph on styrene to federal and state agencies, interested parties, and the public and it will be available in electronic PDF format on the CERHR web site http://cerhr.niehs.nih.gov and in printed text or CD-ROM from the CERHR: M.D. Shelby, Ph.D., Director, CERHR, NIEHS, P.O. Box 12233, MD EC-32, Research Triangle Park, NC 27709, 919-541-3455 [phone], 919-316-4511 [fax], shelby@niehs.nih.gov [email].