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Vol. 13 Issue 4, Fall 2008
By Suzanne Snedeker, Ph.D., Associate Director of Translational Research, BCERF
I was named to serve on the National Toxicology Program’s (NTP) Report on Carcinogens expert panel for styrene earlier this year and participated in a series of meetings this summer as part of the review on styrene. Below is background information on the Report on Carcinogens and my experiences serving as a panel member.
First, what is the Report on Carcinogens? The Report on Carcinogens is prepared in response to legislation under the Public Health Service Act. The report contains a list of substances that “are either known to be human carcinogens or may reasonably be anticipated to be human carcinogens, and to which a significant number of persons in the United States is exposed” (Ref. RoC, 11th edition, 2004). The 12th edition of the Report on Carcinogens is under preparation.
The expert panel for styrene was composed of international experts from diverse fields, including epidemiology, toxicology, environmental fate, chemistry, and genotoxicity. The multi-step process used in determining whether a chemical is listed in the Report on Carcinogens includes the nomination of the chemical, followed by a process in which the evidence of its carcinogenicity and exposure is peer reviewed by several groups of scientists. One of the first steps is the preparation of a background document that contains a summary of the available data on 1) human exposure, 2) human cancer studies, 3) studies in experimental animals, 4) absorption, distribution, metabolism, and excretion, 5) genetic damage, and 6) mechanistic data. The background document is available to the public, and the expert panel reviews the document for its adequacy, accuracy, and completeness. The panel also reads comments on the background document submitted by the public, which includes manufacturers and industry groups.
The task is daunting. The background document for styrene was over 400 pages long and comments from the public filled several binders. Panel members were also give a CD with a PDF of every reference cited (over 450) in the background document. The panel members were assigned to one or more subgroups. Each panel member submitted an individual report on his or her review of the background document. They also submitted additional citations that should be included in the background document. Panel subgroups prepared written reports that were presented in a public forum. Every expert panel member reviewed each subgroup’s comments.
Expert panel members then voted on whether styrene should be listed in the Report on Carcinogens; the majority voted yes. The expert panel’s overall recommendation was that styrene should be listed in the Report on Carcinogens as “reasonably anticipated to be a human carcinogen based on limited evidence of carcinogenicity in humans and sufficient evidence in animals.” (Ref: http://ntp.niehs.nih.gov/files/Styrene_expert_panel_report_B_final_508.pdf)
There are many more layers of scientific review before the NTP makes its final recommendation on whether styrene will be listed in the Report on Carcinogens. If you would like to find out more about the process, see the NTP’s Report on Carcinogens website at: http://ntp.niehs.nih.gov/index.cfm?objectid=DFAFC5A1-F1F6-975E-766CD2956416305E This page includes links to all documents reviewed by the expert panel for styrene, as well as the panel’s peer review comments on the background document, its recommendation for listing in the Report on Carcinogens, and its scientific justification for the listing recommendation.
It was a privilege to serve on the styrene panel. The dedication of the panel members during the review process, as well as that of the NTP’s staff and others involved in the preparation of the background document, was remarkable.
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