By Ben Harder
Reproductive hormones, both natural and the synthetic ones in contraceptive drugs, sometimes survive sewage treatment and turn up in the environment where they can affect wildlife. Modern sewage-treatment facilities, about half of those used in Europe, break down these sex hormones more effectively than older plants do.
A new study shows why: Only the modern, multiple-chamber treatment plants subject the sewage to the gamut of chemical and biological conditions required to break down different hormones.