contamination in US tap water: drugs and pesticides

[Guest guest]

Note how writer Naomi Lubick stresses low levels of each single

pollutant and mentions neither differences in individual susceptibility

nor mixture-effects (additive, synergistic) nor hormesis (ultra-low-dose

effects). In other words, she's reporting polluted tap-water findings

while using rhetoric which belittles those findings. The rationale

which guides her choice of words and concepts is widely used in

" regulatory " processes and in most news articles about pollutants as a

way to allow fictionally " safe " levels of pollutants.

- - - -

*Drinking water contamination mapped*

*Wide-ranging survey reveals low levels of some drugs and pesticides in

US tap water*

Naomi Lubick

http://www.nature.com/news/2008/081217/full/news.2008.1310.html

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, " says Drewes.

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 California.

" 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 these chemicals.

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 a Obolensky of the city of Philadelphia's Water

Department. This study " provides that data and toxicological relevance, "

she says.

Odd abundances

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.

*

References

1. Benotti, M. et al. Environ. Sci. Technol.

doi:10.1021/es801845a (2008).

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