Clean Water, Clear Conscience

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High on the Hog
Another threat to water supplies comes from high-density poultry and hog farms known as concentrated animal feeding operations, or CAFOs. In the last 30 years, more animals have been concentrated on fewer farms and as a result more waste has been dumped in nearby "lagoons" that may overflow during heavy rains. These wastes are thick with nitrogen and phosphorous, two nutrients that in high quantities can contribute to nitrate pollution as well as bacterial and algal blooms in nearby waterways used for recreation or drinking.

Mixing infant formula with water high in nitrates can cause methemoglobinemia (blue-baby syndrome). The wastes are also rich in fecal coliform bacteria and may spread disease.

Some wastes contain hormones and antibiotics fed to animals to promote growth. A study in the 2006 journal Chemosphere found detectable levels of two antibiotics, sulfamethazine and sulfadimethoxine, at six private drinking water wells near a CAFO in Idaho. Use of antibiotics in animals may speed the development of disease-causing bacteria that are resistant to antibiotics.

Arsenic, Perchlorate and MTBE
Not all drinking water contaminants come from human activity. Arsenic occurs naturally in some groundwater throughout North America. A study published last spring shows that exposure in utero and in early childhood increases the risk of lung disease and lung cancer in adulthood. "This is the first study to report increased young adult mortality following early life exposure to arsenic in water," said Allan H. Smith, M.D., Ph.D., an epidemiologist at the University of California, Berkeley's School of Public Health.

Another contaminant that occurs naturally is perchlorate, but most of the contamination in drinking water comes from spills or dumping of this chemical, used in the manufacture of fireworks, explosives and as a rocket propellant. It is now found in the water supplies of over 20 million Americans as well as in milk, lettuce and a handful of other crops. But the EPA has yet to set a drinking water standard for perchlorate nor mandate that its presence in drinking water be reported to consumers. Early this year, senators Barbara Boxer (D-CA), Dianne Feinstein (D-CA) and Frank Lautenberg (D-NJ) introduced two bills to address these issues and California's Department of Health Services is in the process of setting its own standard. Perchlorate blocks the uptake of iodide into the thyroid, and low maternal iodide levels are linked to impaired fetal brain development.

Meanwhile, the EPA has yet to issue a drinking water standard for methyl tertiary-butyl ether (MTBE), a common gasoline additive that has the potential to cause cancer and is estimated to affect the water supplies of about 15 million Americans in 28 states, according to an assessment by the Environmental Working Group.