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Commonly Used Herbicides Linked to Birth Defects
(Beyond Pesticides, July 16, 2003) A U.S. Environmental Protection Agency (EPA) study by researcher Dina Schreinemachers, PhD, which is published in the July 2003 issue of Environmental Health Perspectives, suggests an association between rates of birth malformations and indirect measures of human exposure to chlorophenoxy herbicides, such as 2,4-D and MCPA, common weed killers sold commercially and used in agriculture. The study, Birth Malformations and Other Adverse Perinatal Outcomes in Four U.S. Wheat-Producing States (volume111, pages 1259-1264), compares 43,500 birth outcomes between 1995 and 1997 that were compiled by the National Center for Health Statistics in selected counties of Minnesota, North Dakota, South Dakota and Montana with high-wheat and low-wheat acreage in those states.

Dr. Schreinemachers found that in high-wheat counties, combined circulatory and respiratory malformations increased by more than two-fold, and musculoskeletal malformations increased by 50% relative to low-wheat counties. Death rates from birth malformations among male infants in high-wheat counties were more than twice the rates in low-wheat counties. In addition, the study found, compared with births conceived during other months of the year, an increased chance of circulatory and respiratory (excluding heart) malformations for infants conceived from April to June, a time that more than 85% of the acreage treated with chlorophenoxy herbicides is applied on durum wheat in the states studied.

Chlorophenoxy herbicides are widely used in the U.S. for the control of broad-leaf weeds not only in wheat farming, but also for maintenance of parks, home lawns, roadsides, and utilities rights of way. According to EPA's Pesticide Industry Sales and Usage: 1999 and 1998 Market Estimates, 2,4-D is the most common pesticide used in the non-agriculture sector, with 7-9 million pounds used annually in the U.S., and is the seventh most common pesticide used agriculture, with 28-33 million pounds used annually in the U.S.

The results of Dr. Schreinemachers' study are fairly consistent with those obtained in a 1996 Minnesota birth malformation study by Dr. Vincent Garry of the University of Minnesota, for which Dr. Schreinemachers was a co-author. However, the earlier study also implicated fungicides as a possible cause of the association and a number of other confounders that could not be ruled out as possible explanations.

For more information contact D.M. Schreinemachers, Epidemiology and Biomarkers Branch, Human Studies Division, NHEERL, U.S. EPA, MD 58A, Research Triangle Park, NC 27711, 919-966-5875 or schreinemachers.dina@epa.gov.

For additional studies linking health effects with pesticides, see Beyond Pesticides Daily News Archives. Also, see Beyond Pesticides factsheets on 2,4-D and other pesticides.