GENE ENVIRONMENT INTERACTIONS AND THE RISK FOR CARDIAC DEFECTS

One of the research emphasis areas of the Birth Defects Research Center
has been to define the genetic susceptibility to birth defects from
organic solvent exposure, including both volatile organic solvents such as
toluene and methanol, and halogenated hydrocarbons such as
trichloroethylene.

Why focus on these two classes of chemicals? First, these compounds are
among the top-ten chemicals released into the environment within the State
of Wisconsin, particularly within the Southeast Region of the state.

Second, both toluene and trichloroethylene exposure have been associated
with birth defects. Thus, functional neurological defects are observed in
the offspring of toluene abusing women.

In fact, a Fetal Toluene Syndrome has been defined that exhibits
similarities to Fetal Alcohol Syndrome. In the case of trichloroethylene,
at least two epidemiological studies in other regions of the country have
linked cardiac defects with trichloroethylene exposure from contaminated
well water.

Several studies in multiple animal models corroborated these
epidemiological studies. Finally, both toluene and trichloroethylene are
known to be metabolized by enzymes encoded by genes exhibiting variation
in the human population. Thus, the risk for birth defects will likely be
determined both by exposure to these compounds and genetic makeup.