Using the ATSDR Guidance Manual for the Assessment of Joint Toxic Action of Chemical Mixtures.

The Guidance Manual for the Assessment of Joint Toxic Action of Chemical Mixtures (Mixtures Guidance Manual) is intended to assist environmental health scientists and toxicologists in determining whether exposure to chemical mixtures at hazardous waste sites may affect public health. The Agency for Toxic Substances and Disease Registry (ATSDR) approach is a semi-quantitative screening process. Step-by-step procedures for assessing noncarcinogenic and carcinogenic effects are outlined in flow charts. Exposure data and toxicological information on the mixture of concern are the preferred basis for an assessment. If suitable whole mixture studies are not available, a components-based approach is undertaken. The hazard index (HI) method is used to screen for noncancer health hazards from potential additivity of the components. Cancer risks for the components are summed to screen for health hazards from potential additivity of carcinogenic effects. A weight-of-evidence (WOE) method is used to evaluate the potential impact of interactions on noncancer and cancer health effects.