Most of us are lucky enough not to have to worry about our sewage. We flush the toilet, it goes away somewhere, and we don’t have to worry about cholera or other diseases that spread when waste contaminates the water supply.

While most of sewage systems do a great job of making the water look clean and getting rid of bacteria and viruses, they often aren’t designed to remove synthetic chemicals. With so many of us dependent on daily doses of pharmaceuticals, we’re excreting lots of drugs (or their metabolites), and they’re sticking around in treated wastewater. Researchers are now starting to discover what that means for  the environment.

The LA Times’ Kenneth R. Weiss summarizes some of the findings:

Sewage-treatment plants in Southern California are failing to remove hormones and hormone-altering chemicals from water that gets flushed into coastal ocean waters, according to the results of a study released Saturday.

The preliminary findings were part of the most ambitious study to date on the effect of emerging chemical contaminants in coastal oceans. It confirms the findings of smaller pilot studies from 2005 that discovered male fish in the ocean were developing female characteristics, and broadened the scope of the earlier studies by looking at an array of man-made contaminants in widespread tests of seawater, seafloor sediment and hundreds of fish caught off Los Angeles, Orange and San Diego counties.

The results, outlined by a Southern California toxicologist at a conference in Boston, reveal that a veritable drugstore of pharmaceuticals and beauty products, flame retardants and plastic additives are ending up in the ocean and appear to be working their way up the marine food chain.

Flame retardants used in upholstery and plastic additives are showing up in fish tissues at levels as high or higher than lingering residue of the banned pesticide DDT and another stubborn industrial pollutant, polychlorinated biphenyls, or PCBs.

The study also showed that male flatfish contain unusually high levels of the female hormone estrogen, possibly in reaction to one or more of these hormone-altering chemicals.

As many as 90% of these male fish were found to have produced egg yolk proteins, and one had actually produced eggs, indicating that the feminizing of fish seen in freshwater streams and lakes can happen in the open ocean as well. This evidence, scientists said, suggests that diluting pollution with a vast amount of seawater may not be an effective way to dispose of these new and little-understood contaminants.

“Dilution is not the solution for some of these newer compounds,” said Steven Bay, a toxicologist with the Southern California Coastal Water Research Project in Costa Mesa. He expects the study to raise policy debates over upgrading sewage-treatment plants.

Some plants do a better job than others at removing the chemicals:

“Sewage-treatment plants only remove 50% to 70% of these chemicals,” Bay said.

Bay sketched out the preliminary results in a special session at the annual meeting of the American Assn. for the Advancement of Science.

Much of Saturday’s discussion focused on sex-changing chemicals in municipal wastewater. “It doesn’t take much of the pill to stop fish from reproducing,” said Karen Kidd, a biology professor at the University of New Brunswick in Canada.

Kidd said sewage plants could remove virtually all estrogen with more advanced forms of treatment.

Primary treatment, the type used in San Diego, doesn’t take out as much estrogen as secondary treatment, used by Los Angeles’ Hyperion plant in El Segundo. Those plants, if upgraded to tertiary treatment, could remove nearly all of the estrogen, Kidd said.

A Chemical & Engineering News article focuses on a study in which researchers spiked an experimental lake with synthetic steroidal estrogen, and found that the fathead minnow population plummeted as male minnows started producing eggs — and then the population of lake trout, which feed on minnows, started dropping, too. Once researchers stopped adding the estrogen, the minnow population started to recover. Synthetic estrogen is common in municipal wastewater, because it’s excreted by women taking hormonal birth control pills.

The solid sludge left over from waste treatment contains chemicals, too.  Here, it’s not the fish that are affected — but one study suggests that earthworms might be, when fields are fertilized with biosolids from waste treatment plants. The study found that the worms bioaccumulate pharmaceuticals and personal care products, but didn’t investigate what the effects of such accumulation might be.

Olga at Enviroblog points out that pharmaceuticals aren’t the only things we’re putting down our pipes; substances from our personal care products wash off of us and go down our sink and shower drains, too.

It will probably take more research and years of policy wrangling before municipal wastewater treatment facilities do anything to address pharmaceuticals and other synethetic chemicals in sewage. In the meantime, though C&EN’s Bethany Halford reminds us that we can keep a lot of pharmaceuticals out of wastewater by simply ignoring the old advice to flush unused pills:

Getting people to stop flushing away their unwanted medication is one easy way to cut down on pharmaceutical pollution. So last year, the Office of National Drug Control Policy (ONDCP) issued new federal guidelines for the proper disposal of prescription drugs. According to the guidelines, unused, unneeded, or expired prescription drugs should be removed from their original containers and thrown in the trash.

To prevent accidental poisonings or potential drug abuse, ONDCP recommends mixing meds with an undesirable substance, such as coffee grounds or kitty litter. The mix should be placed into impermeable, nondescript containers, such as empty cans or sealable plastic bags, before being tossed in the trash.

In some cases, the risk of poisoning or abuse outweighs the potential environmental impact. The Food & Drug Administration recommends that certain controlled substances, such as the painkillers OxyContin and Percocet, are best disposed of down the drain. A full list is available at ONDCP’s website (whitehousedrugpolicy.gov/drugfact/factsht/proper_disposal.html).

Pharmaceuticals sent to landfills, however, can end up at wastewater treatment plants as part of the muck that leaches out of the landfill. To ensure that drugs are disposed of in the most environmentally friendly manner, individual communities are developing pharmaceutical take-back programs that collect unwanted medications and then incinerate them.

“There are pilot programs going on all around the country,” says Susan Boehme, a coastal sediment specialist with Illinois-Indiana Sea Grant (IISG), an organization that is educating communities in the Great Lakes region about the environmental effects of unwanted medicines. Although there’s currently no national registry of pharmaceutical take-back programs, Boehme says that IISG is working with the website earth911.org to set up such a database. In the meantime, Boehme suggests that people interested in pharmaceutical take-backs contact their local household and hazardous waste office to find out if there’s a program nearby.

So, think of the fish, and don’t flush your drugs.