- Filed Under
April through July may not be the best time for a woman to get pregnant.
That's the conclusion of researchers at Indiana University School of Medicine studying the possible effects of agricultural pollutants on fetal development. The study, headed by Dr. Paul Winchester, a clinical professor there and director of Neonatology at St. Francis Hospital in Indianapolis, has gained recent national attention in the media. Published in the medical journal, Acta Paediatricia, it correlates births conceived between the months April and July and an increased risk of birth defects.
The concentration of nitrates, atrazine and other pesticides in surface and ground water are highest during these months when these chemicals are applied to crops. It is thought that concentrations of nitrates and pesticides in these sources of drinking water are an indication of the level of human exposure. The effect is not limited to the immediate rural agricultural area but extend "downstream" to urban and suburban areas.
A number of previous investigations have shown that between 89 and 100 percent of fetuses and that 95 percent of the American population have measurable pesticide metabolites in body fluids.
Birth defects are the leading cause of infant mortality in the U.S. accounting for more than 20 percent of all infant deaths. There is a growing body of epidemiologic evidence that exposure to agricultural contaminates near the time of conception may increase the risk of conceiving a child with a birth defect.
Nitrate is the most common chemical contaminant in the world's groundwater. A California study linked well water nitrates to anencephaly; a Texas study found high levels of nitrates in drinking water to be associated with spina bifida. And a previous Indiana study, also by Dr. Winchester, found the same effect from surface water nitrates.
Pesticide exposure has also been connected with congenital anomalies. A Minnesota study found increased birth defects in infants of pesticide-application workers, and an investigation in Iowa demonstrated increased congenital anomalies in municipalities with pesticide-contaminated water. Still another study found infants conceived between April and June had higher rates of birth defects in five wheat-growing states. Other research investigations have shown a strong increased risk correlation for pregnant women living in proximity to pesticide application and for women working in agricultural occupations.
But Winchester's research is the first large-scale investigation of these possible effects conducted in the United States. The research was performed by calculating monthly U.S. birth-defect rates from 1996-2002 using Centers for Disease Control and Prevention data involving more than 30 million births. Average concentrations of these contaminants in surface water were calculated during the same period using U.S. Geographical Survey data. Birth-defect rates were then compared to the pesticide and nitrate levels.
The result: A small but statistically-significant association was found between elevated levels of these toxins and total birth defects in 11 of 22 categories with the highest rate found for the infants conceived between the months of April and July. These birth defects include spina bifida, tracheo-esophogeal defects, gastrointestinal and urogenital defects, cleft lip, clubfoot and Down syndrome. Because of a variety of methodological reasons, the authors believe that the demonstrated increased relative average risk of congenital defects in this investigation was probably blunted. The harmful effects of pollutants are likely even greater in actuality.
It is important to note that this type of study does not prove a cause and effect relationship between agricultural pollutants and birth defects. It demonstrates only an association. Large-scale longitudinal studies would be necessary to prove causation. Hopefully, these studies can be accomplished.
Meanwhile, this investigation should cause us to pause and consider once again the deplorable implications of earthly pollution on humankind.