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Report on Carcinogens Moves Toward Completion

By Thaddeus Schug
July 2010

NIEHS/NTP Director Linda Birnbaum
NIEHS/NTP Director Linda Birnbaum smiled at her audience during a lighter moment following her briefing to the BSC on the Institute's extensive and growing response to the Gulf oil spill and commitment to global environmental health. Birnbaum has assembled a team of scientists, led by NIEHS Senior Medical Advisor Aubrey Miller, M.D., to coordinate response efforts with other federal agencies. (Photo courtesy of Steve McCaw)

NTP Associate Director John Bucher, Ph.D., left, and BSC Chair Raymond Novak, Ph.D.
NTP Associate Director John Bucher, Ph.D., left, and BSC Chair Raymond Novak, Ph.D., looked on during Howdeshell's concept proposal for evaluating cancer chemotherapy during pregnancy. (Photo courtesy of Steve McCaw)

BSC member Elaine Faustman, Ph.D.
BSC member Elaine Faustman, Ph.D., engaged in the debate over classification of glass wool fibers. The BSC spent a significant amount of time questioning NTP scientists and public stakeholders on the differences between longer, less soluble "special wool fibers" used in filtering systems, and glass wool fibers used in insulation products. (Photo courtesy of Steve McCaw)

Lunn, right, and Bucher, left, listened to BSC comments on  formaldehyde, which was one of three chemicals reviewed at this meeting.
Lunn, right, and Bucher, left, listened to BSC comments on formaldehyde, which was one of three chemicals reviewed at this meeting. (Photo courtesy of Steve McCaw)

NTP BSC member David Eastmond, Ph.D.
NTP BSC member David Eastmond, Ph.D. reads his review of the NTP draft substance profile for formaldehyde. Many of Eastmond's comments dealt with the scientific evidence linking formaldehyde exposure to leukemia. (Photo courtesy of Steve McCaw)

The 12th Report on Carcinogens (RoC) came closer to completion during an NTP Board of Scientific Counselors (BSC) meeting on June 21-22 in Rodbell Auditorium. NTP scientists presented draft substance reports for the final three compounds being considered for possible listing in the report for BSC consideration and public comment, including glass wool fibers used in insulation and filtering systems, cobalt-tungsten carbide — powders and hard metals found in cutting tools — and formaldehyde, a widely used chemical found in resins and plastics and used for medical preservation.

Along with other business (see text box), the BSC heard a Center for the Evaluation and Risk to Human Reproduction (CERHR) proposal for a literature review of the potential health effects of exposure to cancer chemotherapy in utero.

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12th Report on Carcinogens

Mary Wolfe, Ph.D., director of the NTP Office of Liaison, Policy and Review, opened the presentations with an overview of the multi-step scientific review process used for the RoC. Wolfe explained, "Each phase of the review process offers opportunities for public input and scientific deliberation" (see 2009 story( She added that "the board is charged with determining whether the scientific information cited in each draft substance profile is technically correct, clearly stated, and supports the NTP's preliminary decision regarding its listing in the RoC." The NTP will review BSC and public comments before recommending final classifications for the substances for the 12th RoC.

The NTP recommended retaining glass wool fibers listing as "reasonably anticipated to be a human carcinogen" as reported in the 11th RoC, despite objection by the North American Insulation Manufactures Association (NAIMA) and several other public stakeholders, and the findings of its 2009 expert panel (see story( NAIMA representatives argued that NTP should follow the recommendations of its independent expert panel and separate glass wool into different categories according to specific criteria related to their size and durability.

In response, NTP's Gloria Jahnke, D.V.M, noted, "Although not all glass fibers are carcinogenic, there is sufficient evidence from studies in experimental animals and mechanistic data to group them as one class." NTP scientists also pointed to the lack of any clear scientifically established way to distinguish between those fibers that cause cancer and those that do not without testing each individual product.

Discourse was also animated over NTP's recommendation to reclassify formaldehyde from a "reasonably anticipated carcinogen" to a "known human carcinogen" (see 2009 expert panel story( NTP RoC Center Director Ruth Lunn, Dr.P.H., said, "The decision to change the listing status of formaldehyde is based on sufficient evidence in human epidemiology studies with supporting mechanistic information." Much discussion centered over recent studies linking formaldehyde exposure to forms of leukemia, in addition to less common cancers of the nasopharynx and sinonasal cavity.

Lunn also presented evidence in support of listing cobalt-tungsten carbide: powders and hard metals as "reasonably anticipated to be human carcinogens."

CERHR proposes evaluation concept

Also during the day and a half meeting, Kembra Howdeshell, Ph.D., presented a CERHR concept to evaluate literature concerning the pregnancy outcomes of women treated with cancer chemotherapy during pregnancy and follow-up on their offspring exposed in utero. According to Howdeshell, a growing number of women are being diagnosed with cancer during pregnancy. Estimates range from 1 in 1,000 to 1 in 6,000. Treatment most often involves some form of chemotherapy. However, nearly all chemotherapy agents are U.S. Food and Drug Administration Pregnancy Category D, which investigational or post-marketing data show risk to the fetus. The evidence of risk of the chemotherapeutic agents usually comes from studies in laboratory animals. 

Howdeshell's proposal is for the NTP to develop a monograph, which "will provide a thorough survey and critical scientific evaluation of the human literature, to determine whether cancer chemotherapy administered during pregnancy affects pregnancy outcomes." Howdeshell added, "It should provide physicians and their patients with an informed perspective on what is known about the developmental effects following exposure to chemotherapeutic agents in utero."

 (Thaddeus Schug, Ph.D., is a postdoctoral research fellow in the NIEHS Laboratory of Signal Transduction and a regular contributor to the Environmental Factor.)

Additional NTP Board of Scientific Councilors Meeting Highlights

  • NIEHS/NTP Director Linda Birnbaum, Ph.D., briefed BSC on NIEHS response to gulf oil spill.
  • NTP CEBS Scientific Administrator Jennifer Fostel, Ph.D., demonstrated the Chemical Effects in Biological Systems (CEBS) data management system to the BSC.
  • NTP Associate Director John Bucher, Ph.D., provided updates on finance, staffing, and scientific events at NTP.
  • NTP Toxicologist Barry McIntyre, Ph.D., presented a research concept for Hydroxyurea.

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