Researchers from the Baylor College of Medicine compared rates of a rare birth defect called choanal atresia—which happens when the cavity between a baby's nose and mouth becomes fully or partially closed and causes breathing problems that can be fatal—to application rates of the herbicide atrazine in Texas farm fields. Buy a filter.
If you're surrounded by lots of farm fields, find a water filter that removes atrazine. Most faucet-mount or pitcher-style charcoal filters will remove it, but double-check the packaging to make the filter is "NSF Certified" to remove atrazine.