Is there evidence that atrazine exposure can affect breast cancer risk in women exposed to this herbicide? There are few studies of women that have attempted to answer this question. Unfortunately, there are no well-controlled human studies that have evaluated breast cancer risk in women exposed to atrazine compared to women not exposed to this herbicide.

Two “ecological” studies have been conducted in Kentucky. Ecological studies approximate exposures of a population within a certain geographic area rather than evaluating exposures of individuals.

In the first study researchers found higher breast cancer rates in women living in counties with:
   - A higher use of corn herbicides and
   - Higher levels of triazine herbicides in water supplies.

This study did not estimate actual exposures to atrazine, but used surrogate measures, like number of acres of corn grown, to estimate atrazine exposure.

This may have introduced inaccuracies, since many herbicides besides atrazine are used as corn herbicides.