Green Guide, Catherine Zandonella, M.P.H
Published March 1, 2007
Clean and abundant water is something we take for granted in America, even as we persist in polluting waterways with yard-care pesticides, agricultural wastes and other contaminants. But new studies showing that young children, whose bodies are still developing, face the greatest risk from these pollutants ought to make us reconsider how we treat our most essential natural resource. As spring approaches, keep in mind that the chemicals that seem to make life easier can present problems to your family's health and that of the environment.
Lawn Care Without Borders Pesticides and herbicides must be handled cautiously, yet homeowners often fail to read directions, neglect to wear protective clothing, track chemicals into the home and allow kids and pets to play on freshly treated grass. "People assume that because they see a product in the store, it is perfectly safe," says Jane Nogaki, pesticide program coordinator for the New Jersey Environmental Federation, "and that simply is not the case."
Over 100 million pounds of herbicides and pesticides are applied around
American residences each year. A study in the December 2006 Pediatrics found that young children exposed prenatally to high levels of the insecticide chlorpyrifos were more likely to have developmental delays and attention problems at three years of age than children exposed to lower levels. Chlorpyrifos is now banned for use in residences, but other suspect pesticides remain on the market (see below).
Prenatal exposure to harmful chemicals poses an array of other dangers as well, a study in the May 2004 Environmental Health Perspectives found. The investigators tested several common lawn and garden chemicals‹including groundwater contaminants 2,4-dichlorophenoxyacetic acid (2,4-D), atrazine and dicamba‹for their ability to harm mouse embryos during a period corresponding to the first five to seven days after human conception. These three chemicals, along with nine other common compounds, caused increased cell death among the embryos.
Atrazine, chlorpyrifos and turbufos reduced the odds that an embryo would progress to the next stage of development, the blastocyst. The experiments were conducted using concentrations that an average person might be exposed to during chemical application or from ingesting contaminated groundwater.
Atrazine, in particular, may have affected as many as 3,600 drinking water systems throughout the U.S., mainly in the Midwest. "Pesticide-induced injury can occur at a very early period of embryo development and at pesticide concentrations assumed to be without adverse health consequences for humans," wrote the investigators. For products to avoid see "What You Can Do," below.
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.
