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Scientists have known for decades that low concentrations of drugs are often present in drinking water, but there has not been much published on drugs in the Canadian water supply. A recent study conducted by Servos et al. for Environment Canada’s National Water Research Institute (NWRI) provided some useful Ontario data.

Background – How do drugs get into the water supply? To name a few:
• The meds that we take pass through our bodies and are either excreted as metabolites (altered) or unchanged, primarily via urine or feces
• Our animals, including livestock, are given (and excrete) many drugs (e.g., antibiotics, hormones)
• Households, stores and healthcare facilities discard unused medications into landfill (where they leach into groundwater), or down the sink or toilet
• Hospital wastes (treated/untreated) enter domestic sewage systems
• Drug residue in human bodies leaches into groundwater from cemeteries
• Biosolids that are used on agricultural land may contain drugs

The study – Servos et al. looked for 8 acidic drugs and an antibacterial agent in effluent from 20 water treatment plants somewhere in Ontario (they did not tell us where, although they do say the facilities were “within close proximity” to NWRI facilities in Burlington, and they do provide information about the population serviced by each treatment plant). Water was sourced from wells, lakes and rivers. Sampling was done in the fall, when high river flows are anticipated.

These drugs were selected because they are commonly used, have already been reported in the literature, and can be assayed. These included several non-steroidal analgesics (diclofenac, fenoprofen, ibuprofen, indomethacin, ketoprofen, naproxen) and the cholesterol-lowering agents clofibric acid gemfibrozil. Triclosan is an antibacterial agent found in many personal care products, such as soaps, toothpastes, and mouthwashes.

The results? The chemicals were detectable in water from 15 of the treatment plants. None of the drugs were found in the water that sourced from wells, while water from lakes had low but detectable levels. Highest concentrations were found in water sourced from rivers. Of note, two sites that had the highest concentration of drugs were located immediately downstream of sewage outfalls; the authors postulate that the drugs would be present at much higher concentrations in the (dry) summer, where sewage flow can greatly exceed 10% of total flow of the river.

The bottom line – There is no reason to stop drinking tapwater. Drug concentrations found in water supplies have been very low, and many experts suggest that the amount of drug we are exposed to in our drinking water is so small as to be insignificant. However, there are a lot of unknowns, such as:
• the effects of chronic exposure to very low levels of a “chemical soup” made up of hundreds of drugs and their metabolites on human or animal health and our ecosystem. Some combinations could exert a (negative) synergistic effect. (Homeopathy is based on the effects of very dilute solutions.)
• other drugs that have been detected in our water, like endocrine-disrupting substances (e.g., estrogens), may have adverse effects. One chilling example is that of a Fisheries & Oceans Canada study in the Experimental Lakes Area in northwestern Ontario, where ethinyl estradiol (EE) (commonly used in oral contraceptives) was added to a lake to achieve a concentration of 5–6 ng/L; this impaired male and female reproductive capacities in fatheaded minnows, resulting in reproductive failure (a lethal effect). See Kidd KA et al. Collapse of a fish population after exposure to a synthetic estrogen. PNAS 2007 May 22;104(21):8897-8901
• only a comparatively few drugs can be assayed for – do the thousands of drugs we cannot detect in our water pose a threat?

The good news is that companies are developing the technology to remove drugs from the water. Whether our governments will be able to afford it is another matter. More good news – you can do your part by taking your unused medications back to your drugstore, for proper disposal.

For more information about drugs in our water supply
• see Siskinds’ article, Drugs on Tap
• a good backgrounder is available from the NWRI: Pharmaceuticals and Personal Care Products in the Canadian Environment: Research and Policy Directions (2007)
• read anything by Christian Daughton, a senior scientist at the US EPA.

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