[Pharmwaste] Drinking water contamination mapped
Laurie.Tenace at dep.state.fl.us
Thu Dec 18 09:59:39 EST 2008
Drinking water contamination mapped
Wide-ranging survey reveals low levels of some drugs and pesticides in US tap
The researchers found small traces of pesticides and drugs in US drinking
water. The most comprehensive survey so far has found a slew of drugs,
personal care products, pesticides and other contaminants in drinking water
being delivered to millions of people across the United States. None of the
compounds appeared at levels thought to be immediately harmful to human
health. But the researchers were surprised to find widespread traces of a
pesticide, used largely in corn (maize) growing, that has, at higher levels,
been linked to cancer and other problems.
The researchers from the Southern Nevada Water Authority (SNWA) in Las Vegas
tracked 51 compounds in a survey of 19 water utilities supplying more than 28
million people. Of the 20 drugs or drug metabolites on their list, most of
those that the chemists detected were at concentrations of below a microgram
per litre, in source water, treated water and tap water. Their findings are
published in Environmental Science & Technology1.
The study unexpectedly revealed relatively high levels of the pesticide
atrazine, a suspected endocrine disruptor used throughout the US corn belt
(the American midwest) but banned by the European Union. The authors detected
atrazine in water far from farm land and even in the source water of a plant
located in the most arid part of the United States, where the pesticide is
not used at all.
Atrazine could be getting into water through food and drink, the researchers
suggest, with, for example, many soft drinks containing corn syrup helping
the pesticide to spread through the water-treatment system. However, like the
other contaminants found by the team, the levels were below the US
Environmental Protection Agency's safe maximum. For atrazine, this is 3.0
micrograms per litre; the highest value recorded by the researchers was 930
nanograms (0.93 micrograms) per litre.
The atrazine findings underscore that "there's more contribution [to
contaminant loads] from industrial chemicals than pharmaceuticals," says Jörg
Drewes, an environmental engineer at the Colorado School of Mines in Golden.
He points to the study's results on other endocrine disruptors: bisphenol A,
nonylphenol and chlorinated flame retardants. "These could be leaching out of
[household] plastics, even plastic pipes [used in] the treatment process,"
The tiniest of traces
Scientists and regulators have tracked these compounds for years. But this
team was able to detect contaminants at some of the lowest levels yet, using
analytical methods generally beyond the means of most labs and utilities,
says Stuart Krasner of the Metropolitan Water District of Southern
"As analytical chemists improve the sensitivity [of their techniques], they
are ... going to see things we couldn't see before," Krasner says. Now, he
adds, researchers must establish what risks are posed to human health from
long-term, low-level exposure to such contaminants, as well as to mixtures of
The survey is part of a larger project by the Awwa Research Foundation in
Denver, Colorado, that is set to be made public next year. Its aim is to help
water utilities to find substances that they can monitor to check that their
treatment processes are working. Water companies in the United States
generally use oxidants - chlorine, ozone or both - to treat water.
"There are virtually no data" on what happens in water-distribution systems,
adds Alexa Obolensky of the city of Philadelphia's Water Department. This
study "provides that data and toxicological relevance," she says.
The SNWA survey, says co-author Shane Snyder, found that for drugs
"prescription volume did not translate into occurrence". For instance, the
team detected the anticholesterol drug atorvastatin (Lipitor), the most
prescribed drug in the United States in 2006 and 2007, only in source water
and then only for three utilities.
But the epilepsy medicine carbamazepine, not even in the top 200 prescribed
drugs in the United States, was one of the most frequently detected in source
waters, and appeared at the tap on several occasions too. The drug is hard to
break down and so may be more persistent than some other compounds.
The team also found steroid hormones in source water, but never at the tap.
"You have to look at what people are exposed to, not what's in the
reservoir," when assessing human exposure risks, says Snyder.
Chlorination breaks down these endogenous steroid hormones in seconds, Snyder
adds. And at least one report of hormones in tap water, for San Francisco,
has since been found to be a false result.
The survey illustrates that cleaner source waters produce cleaner drinking
water at the tap. "We should be going toward protecting water resources,"
says Obolensky. She believes preventing pollutants getting into the water
supply in the first place is the most efficient way of tackling contamination
- rather than putting money into advanced treatment at drinking water plants.
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