Chemical mixtures and health effects at Superfund sites.

Between 1991 and 1993, EPA's Office of Research and Development conducted a small health effects research program dedicated to the problem of chemical mixtures at Superfund sites. This paper summarizes key findings from the program. The studies covered a wide range of endpoints, several chemical classes, and mixture complexities ranging from two to five chemicals. Additivity and antagonism were far more common than synergy. Departures from additivity seemed to be on the order of a factor of two or less, an observation that may provide some bounds for concern.