nt contaminants present after initial treatment, eliminated 16 and 12 of the chemical compounds, respectively.

“Conventional wastewater treatment processes don”t eliminate pharmaceuticals and hormones as effectively, resulting in the release of low levels of these compounds into the environment,” says Pedersen. “The more advanced processes, on the other hand, do a pretty good job at removing compounds.”

Yet, exactly what these differences in contaminant removal may mean for the environment — and even human health — remains uncertain, says Pedersen.

“This is a case where the analytical chemistry is ahead of the toxicology,” he says. “Right now, the ecological effects of chronic low-level exposure to many of these pharmaceuticals are unknown.”