Little did I know that filtering my family's tap water might put our teeth at risk.

Two years ago, when I was pregnant and reporting on how the federal government was unwilling to regulate the rocket-fuel component perchlorate in drinking water, my husband and I decided to install a reverse osmosis filter in our kitchen tap. Since D.C. tap water has come under fire for its high levels of everything from lead to hexavalent chromium, it seemed like a sensible move.