Water, water, everywhere...but should we drink it?
Scientists have known for decades that
very low concentrations of drugs are present in our drinking
water. There has not been much published concerning 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 data that are specific to Ontario.
The entire study can be viewed here:
at this web page
Background - How do drugs get into
the water supply? To name a few ways:
- 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) synergystic
effect. (Think of the positive effects of very dilute
solutions by those who adhere to the principles of
homeopathy
- 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,
at
this web page.
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:
- a good backgrounder is available from the NWRI:
Pharmaceuticals and Personal Care Products in the
Canadian Environment: Research and Policy Directions
(2007) at
this web page
read anything by Christian Daughton, a senior
scientist at the US EPA. He is highly Googl-able.
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