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From July 25, 2006                                                                                                        

Study Finds Agricultural Pesticides Common In Rural House Dust
(Beyond Pesticides, July 25, 2006)
A new study finds that trace quantities of agricultural chemicals find their way into rural homes—not only on the fruits and vegetables that consumers buy, but also through dust that enters houses. The study, “Proximity to Crops and Residential Exposure to Agricultural Herbicides in Iowa,” which was published in the June 2006 issue of the journal Environmental Health Perspectives, shows that home exposure to agricultural herbicides increases as the amount of nearby cropland increases.

The findings are disturbing considering the documented links between pesticides and health effects, including non-Hodgkin's lymphoma. This study was done as an offshoot of a larger non-Hodgkin's lymphoma study financed by the National Cancer Institute, reports Science News Online.

In the new study, Mary H. Ward, PhD, of the National Cancer Institute, and her colleagues collected dust vacuumed from the homes of 112 Iowa lymphoma patients and healthy, randomly selected volunteers of the same age. Using satellite-generated maps of agricultural fields in the state, the team calculated the acreage of croplands near the home of each participant. Both farm and in-town homes were included in the study. Because most of Iowa’s cropland had been historically planted with corn and soybeans, Dr. Ward's team probed homes for specific chemicals known to be used on the local fields.

Analyses show that at least one of six primarily agricultural herbicides is present in house dust from 28 percent of sampled homes. These chemicals include acetochlor, alachlor, atrazine, bentazon, fluazifop-p-butyl, and metolachlor. Atrazine and metolachlor are the agents most commonly used to treat corn and soybeans. The next most-popular herbicides used on the crops are trifluralin and dicamba. At least one of these four herbicides show up in 43 percent of homes.

Although atrazine had been applied to nearly 70 percent of corn acreage, it showed up in the house dust of only 8 percent of homes. Where detected, however, its concentration in dust ranged from 60 to 4,700 parts per billion (ppb). Metolachlor was found in about 20 percent of homes; its concentration ranged from 27 to almost 3,200 ppb.

Most shocking is the amount of dust containing 2,4-D, which was found to be present in 95 percent of homes, typically in concentrations exceeding 1,000 ppb. In one house, 2,4-D's values reached an astounding 125,000 ppb. Used on crops, along roadsides, in forests, and on lawns, 2,4-D is the third most widely used herbicide in the United States and Canada. According to Illinois EPA, 2,4-D is a probable endocrine disruptor and a number of studies link 2,4-D to non-Hodgkin’s lymphoma.

The study also finds that farm workers' homes are generally the most contaminated with weed killers. Some herbicide concentrations in their dwellings more than tripled those present in the homes of people who have never worked in agriculture.

Nearly 60 percent of the study's participants live within 550 yards of cropland. The chance of finding agricultural weed killers in house dust increases by six percent for every 10 acres of cropland found within a roughly 800-yard perimeter of the house. The result was that herbicide-laced dust showed up in three-quarters of homes having at least 300 acres of cropland within that 800-yard perimeter.

Of nearly 120 studies that have investigated the risk of non-Hodgkin's lymphoma associated with pesticide contact, most show an increased risk for the disease—especially for herbicides—according to the Lymphoma Foundation of America. Printed information from the foundation states that the pesticides "more frequently associated with increased lymphoma incidence and/or deaths" are the herbicides 2,4-D and the triazines, which includes atrazine.

Cancer, however, is far from the only health or environmental risk associated with agricultural pesticides. For instance, some herbicides used on corn have been shown to disrupt normal reproductive development in frogs, in studies so far (see Daily News). Some biologists now suspect that such changes may explain declining amphibian populations.

Agricultural pesticides may also affect human fertility. Four years ago, epidemiologist Shanna H. Swan, PhD, of the University of Missouri and her colleagues studied sperm in men from big cities and small towns. In the study, sperm concentrations and quality in men from semi-rural Missouri communities are below those of men from Minneapolis, Los Angeles, and New York City (See Daily News). This suggests, Dr. Swan told Science News Online that "environmental exposure to current-use pesticides is associated with poorer semen quality."

In an extension of that study, the Centers for Disease Control and Prevention in Atlanta will soon measure agricultural pesticides in the urine of men who had participated in the original study, notes Dr. Swan, now at the University of Rochester.