Do you know what’s in your water? If you’re not sure, send off a sample to get tested. The top contaminants of concern for cancer in drinking water are arsenic, hexavalent chromium, and radioactive elements such as uranium and radium, according to a study published in the journal Environmental Health that analyzed drinking water in California. Researchers estimated that drinking from the United States’ water system over the course of a lifetime could contribute to 15,500 cancer cases; the combination of chemicals often found together may contribute to a greater risk. Remember that even if your water follows regulations, it may still contain certain contaminants,  In other words, filtering still makes sense.