Peer review panel evaluates draft NTP technical reports
By Ernie Hood
Draft NTP technical reports evaluating the carcinogenicity and toxicity of two dietary supplements, a water disinfection byproduct, and a metalworking fluid were peer reviewed May 22 by an expert scientific panel.
NTP, an interagency program, conducts rodent toxicity and cancer studies on agents of public health concern to identify potential human health hazards. The technical reports describe the methods, results, and NTP conclusions regarding levels of evidence for carcinogenic activity under the specific conditions of each study.
Green tea extract
Green tea extract (GTE) is a commonly used dietary supplement in the U.S., marketed for its potential health benefits, such as increasing metabolism, fighting cancer, boosting the immune system, and promoting cardiovascular health. A component of GTE, epigallocatechin gallate, was originally nominated by the National Cancer Institute (NCI) for testing due to the lack of available chronic toxicity and carcinogenicity data. Ultimately, NTP chose to study GTE because there is more human exposure to the extract than to the nominated component. After analyzing several lots of commercially available GTE, NTP selected one GTE preparation for testing.
The panel accepted the draft NTP conclusions of no evidence of carcinogenic activity of GTE in male and female rats and in male mice. They also recommended a conclusion of no evidence of carcinogenic activity in female mice, instead of the draft NTP conclusion of equivocal evidence.
Indole-3-carbinole is a dietary supplement sold alone or in combination with other herbals or vitamins. It is marketed as a cancer prevention agent, as well as for its health benefits, such as detoxifying the liver and boosting the immune system. NCI nominated indole-3-carbinole for study based on its occurrence in natural products such as cruciferous vegetables, including broccoli, Brussels sprouts, cauliflower, and kale, and its potential use as a breast cancer chemoprotective agent, to protect healthy tissue from the toxic effects of anticancer drugs.
The panel accepted the draft NTP conclusions of no evidence of carcinogenic activity in male rats and female mice, some evidence in female rats, and clear evidence in male mice.
Cimstar 3800 is a semi-synthetic metalworking fluid used in machining automotive parts and other materials. The National Institute for Occupational Safety and Health nominated it for study based on a high potential for occupational exposures and the absence of toxicity or carcinogenicity studies.
The panel accepted the draft NTP conclusions of equivocal evidence in male and female rats, no evidence in male mice, and some evidence in female mice.
Bromodichloroacetic acid (BDCA) is a member of the haloacetic acid family of drinking water disinfection by-products, formed when disinfectants such as chlorine or ozone are used in water treatment plants. It was nominated for study by the U.S. Environmental Protection Agency and the American Water Works Association Research Foundation, based on widespread human exposure in drinking water and lack of toxicity and carcinogenicity studies.
The panel accepted the overall draft NTP conclusions of clear evidence of carcinogenic activity based upon a variety of neoplasms occurring in male and female rats and male and female mice.
(Ernie Hood is a contract writer with the NIEHS Office of Communications and Public Liaison.)