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What are we flushing down the drain?


Although the issue was first raised about 10 years ago, Canada has not yet developed a plan to deal with the pharmaceuticals and personal-care products that get flushed down the drain, pass right through municipal wastewater treatment plants, and end up in our rivers and lakes. If that isn’t worrying enough, there is now an added potential hazard of nanomaterials entering the water system, says Chris Metcalfe, director of Trent University’s Institute for Watershed Science and a leading expert on water-borne contaminants.

The list of drugs and personal-care products making their way into the watershed – and sometimes ending up back in our drinking water – includes the birth control pill, antidepressants and cholesterol-lowering agents, as well as sunscreens, insect repellents and antibacterial agents. Some of these chemicals can affect aquatic wildlife, even at very low concentrations, while their cumulative affect on humans is still largely unknown.

Personal-care products enter the environment mainly when users bathe or swim, while drugs enter the environment when they’re excreted from the body or, to a lesser extent, when unused portions are thrown directly down the toilet.

Environment Canada and Health Canada have been “kind of struggling” with how to regulate this group of chemicals and how to assess their impact, says Dr. Metcalfe. Canada “could be doing a lot better” in terms of upgrading its wastewater treatment plants to deal with these contaminants, he says, but such upgrades would cost billions of dollars. “It’s rather like urban infrastructure in general. We’re going to have to deal with it over the next few decades.”

The concern with nanomaterials, meanwhile, “is they’re so damn small,” explains Dr. Metcalfe. These materials, used increasingly in a variety of high-tech products, contain tiny particles measured in nanometres – or one-billionth of a metre. The technology exists to filter out most compounds from wastewater, but not nano-sized particles, he says.

Research has shown that nanomaterials have the ability to pass through cell membranes, through the blood-brain barrier, and likely through the placental barrier. “We don’t know whether this is an issue, but there are enough warning lights flashing that we should at least be determining whether there is potential for ecological or human health effects,” says Dr. Metcalfe.

He and colleagues were turned down when they first applied for a strategic grant from the Natural Sciences and Engineering Research Council to look into this area three years ago, but they were successful in the latest round of funding. The OECD also established a working group in July 2007 to look at nanomaterial safety.

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