The Agency for Toxic Substances and Disease Registry (ATSDR), a public health agency of the U.S. Department of Health and Human Services, announces the results of a computer-modeling research study conducted under the ATSDR voluntary research program.

Methylene Chloride Study
The recent methylene chloride computer-modeling study predicts that no adverse health effects are expected to occur to the human immune system from drinking water containing large amounts of methylene chloride over a short time period. Possible immune effects at the point of contact (for example, the lungs) were not assessed in this study or in an earlier study involving rats completed in 2000.

The study was conducted through support by member companies of the Halogenated Solvents Industry Alliance Inc. (HSIA), specifically the Vulcan Materials Co., Dow Chemical Co., PPG Industries Inc. and INEOS Chlor Americas Inc.

The results of the study were obtained using physiologically based pharmacokinetic (PBPK) modeling, a state-of-the-art computerized technique.

PBPK modeling uses data on contaminant levels causing adverse health effects in animals to project contaminant levels that would be expected to cause similar effects in humans. The technique also can be used to predict contaminant levels that cause adverse health effects from one type of exposure route (such as inhalation exposure) to another exposure route (such as oral exposure).

The PBPK modeling involved the use of data from a 2000 HSIA study of rats breathing methylene chloride for 28 days to estimate oral intakes of methylene chloride that would not produce immune system toxicity in humans. (The 2000 study also was conducted under ATSDR's voluntary research program.)

The need for research data for oral exposure is a priority because ATSDR has identified ingestion of contaminated environmental media (water) as an important exposure route for methylene chloride at hazardous waste sites. The chemical is found in at least 884 hazardous wastes sites in the United States. Methylene chloride is currently ranked No. 78 on the ATSDR Priority List of Hazardous Substances found at NPL sites.

Additionally, the scientific literature contains increasing evidence that the immune system might be susceptible to many environmental contaminants. More specifically, suggestive evidence, from limited data in animals exposed to methylene chloride via inhalation, indicates that immune-system toxicity might be a health effect of concern.

However, no previous studies were located on immune-system effects in humans, and no information is available on the immune system effects of methylene chloride in animals after oral exposure -- a primary exposure route at waste sites. Thus, ATSDR determined it was a priority to conduct additional studies to further assess the potential effect of methylene chloride on the immune system. HSIA volunteered to conduct a PBPK computer-modeling study to project the effects of oral exposure to methylene chloride from the alliance's research data on inhalation exposure in rats.

This recent research study adds to the scientific knowledge on the health effects of exposure to methylene chloride. ATSDR and HSIA recently signed an agreement to collaborate to fill ATSDR's remaining priority data needs for tetrachloroethylene and trichloroethylene.

ATSDR Voluntary Research Program
The ATSDR voluntary research program, a component of the Superfund-mandated Substance-Specific Applied Research Program, is a collaborative effort of ATSDR and private-sector industry groups that represent manufacturers and processors of the hazardous substances found at waste sites in the U.S.

Under this program, research to fill ATSDR's priority data needs is voluntarily sponsored by industry groups representing manufacturers and processors of the substances studied. Costs of the program are borne by the manufacturers and processors of the substances studied.

ATSDR accepts these studies and their conclusions on the basis of recommendations of external peer reviewers, who evaluate the study protocols and final reports, and the industry group's satisfactory response to reviewer comments.

ATSDR considers the voluntary research program to be an important mechanism for filling the agency's priority data needs for hazardous substances for which little or no research has been conducted. The agency has identified priority data needs for 60 substances. Research data is needed to assess the possible health effects of exposure to these substances. (See Federal Register Notice (66FR42659), Jan. 31, 2002.)

Many of ATSDR's priority data needs remain to be filled. The agency strongly encourages private-sector organizations to volunteer at any time to conduct needed research.

Dr. Christopher De Rosa, director of the ATSDR Division of Toxicology, said, "The ATSDR voluntary research program provides an excellent example of how the federal government and the private sector can work together effectively to address environmental public health issues." Collectively, ongoing or completed voluntary research has saved ATSDR more than $10 million in research costs.

Contact ATSDR for more information on how private industry groups can participate in this cooperative research program. Call the ATSDR toll-free number, 1-888-42-8737 and ask for Yee-Wan Stevens or William Cibulas in the Research Implementation Branch of ATSDR's Division of Toxicology. To contact them directly, call (404) 498-0140, or e-mail: YStevens@cdc.gov or WCibulas@cdc.gov.

Members of the news media may request an interview with ATSDR staff by calling John Florence or Elaine McEachern in the ATSDR Office of Policy and External Affairs at (404) 498-0070.