About the Chemical Mixtures Program
The Agency for Toxic Substances and Disease Registry (ATSDR) has been mandated to determine the health impact of exposure to combinations of chemicals. Exposure to two or more chemicals occurs at numerous hazardous waste sites (HWS), sometimes by way of more than one exposure route. Meanwhile, the majority of current toxicological research focuses on the health effects of exposure to a single substance.
In order to fulfill its mandate, ATSDR is engaged in a multi-faceted course of investigation into the human health effects of chemical mixtures, including: (1) identification of the mixtures of highest concern to public health, (2) estimation of the joint toxic action of these chemicals through assessment and laboratory methods, and (3) development of new methodologies for evaluating the health effects of mixtures.
- Develop Interactions Profiles. Similar to the Agency toxicological profiles, these documents summarize the health effects caused by exposure to chemicals in a mixture.
- Develop a Guidance Manual for the Assessment of Joint Toxic Action of Chemical Mixtures. A manual to assist health assessors in determining the impact of chemical mixture exposure on public health.
- Develop Minimal Risk Level (MRLs) for chemical mixtures. Use existing methods to derive health guidance values for mixtures such as chlorinated dibenzodioxins (CDDs) and polybrominated biphenyls (PBBs).
- Perform weight of evidence analyses for combinations of chemicals. These analyses are used to predict the influence of one chemical on the health effects of another chemical.
- Conduct laboratory studies in collaboration with the National Institute of Environmental Health Sciences and TNO Nutrition and Food Research Institute (The Netherlands) to validate weight of evidence analyses.
- Develop methods to evaluate toxicologic interactions of chemical mixtures. Trichloroethylene, the most frequently found drinking water contaminant, is being studied in combination with chemicals such as vinyl chloride, arsenic and 1,2-dichloroethane that are found together in water.
- Test effects of metal mixtures using laboratory techniques. Simple mixtures of environmentally important chemicals such as arsenic, cadmium, chromium and mercury are being studied.
- Improve precision and reliability in toxicity assessment methods for mixtures. Dose-response relationships are being studied using mixtures of liver toxicants such as chloroform and trichloroethylene.
- Assess the absorption of toxic chemical mixtures through skin. Mixtures of chemicals such as polychlorinated biphenyls (PCBs) and pentachlorophenol are being studied in the presence of chemicals that are found together and can influence skin absorption rates.
- Develop new methods and protocols to estimate the toxicity of complex mixtures. Mixtures containing polycyclic aromatic hydrocarbons (PAHs) that are found in sediments of certain hazardous waste sites are being studied. Such methods, when fully developed and validated, may be useful to assess the toxicity associated with lifestyle and occupational exposures.
Recent Actions of the Mixtures Program
The Tom's River New Jersey Site - An example of the important use of information on chemical mixtures.
In 1996 the Agency prepared two consultations:
- “An evaluation of the relationship of cancer and exposure to contaminants identified at the Ciba-Geigy site and Reich Farm site, Ocean County, New Jersey” (1996).
- “Toxicological issues related to chemicals identified by the New Jersey Department of Health and Senior Services” (1996).
In 1997, the Agency conducted:
- A full weight-of-evidence evaluation for nine chemicals (aldol, aniline, anisidine, anthraquinone, azo-dyes, 1,4-dioxane, epichlorohydrin, phenol, polypropylene glycol) found at the Tom’s River sites (1997).
In 1997, the Agency prepared a consultation:
- “Interactions review of chemicals identified in the first chemical specific consultations related to Tom’s River investigation” (1997). Chemicals included were: acetone, aluminum, anthracene, benzene, cadmium, chlordane, chlorobenzene, chloroform, chromium, di(2-ethylhexyl)phthalate, 1,4-dioxane, endosulfan, heptachlor epoxide, lead, mercury, N-nitrosodiphenylamine, tetrachloroethylene, toluene, trichloroethylene, and vinyl chloride.
In September 2002 there was an International Conference on Chemical Mixtures (ICCM) held in Atlanta, Georgia. ATSDR was a co-sponsor.
Where can I get more information?
Agency for Toxic Substances and Disease Registry
Division of Toxicology and Environmental Medicine
1600 Clifton Road NE, Mailstop F-62
Atlanta, GA 30333
Phone: 1-800-CDC-INFO • 888-232-6348 (TTY)
FAX: 770-488-4178
Email: cdcinfo@cdc.gov