Infant Health
Herbicides Linked to Infant Health Problems

The herbicides atrazine, cyanazine and metolachlor may be linked to a range of adverse health effects, including respiratory distress, cerebral palsy and impaired development.  According to a recent study of drinking water contamination in Iowa, these three herbicides were each associated with higher community levels of intrauterine growth retardation (slow fetal growth resulting in low birth weight) among newborns.  The researchers said that slow fetal growth is a predictor of increased infant mortality and is the second leading known cause of fetal death.

The researchers pointed out that this study is based on data at the community level rather than on data collected from individuals, and stressed that their findings should be considered preliminary until more detailed epidemiological studies on individual exposure levels are carried out.

However, they stated that previous studies have indicated herbicides can cause adverse effects on growth and development in laboratory animals and that atrazine has been linked to endocrine disruption.  These studies suggest that the reported link in Iowa between herbicide consumption and slow fetal growth is biologically plausible.

The study examined 13 communities in southern Iowa served by the Rathbun Regional Water Association, a water system that supplies drinking water exclusively from the Rathbun reservoir.  It compared levels of contaminants in the Rathbun communities' water with drinking water from other communities in southern Iowa.  The communities were similar in population size, education level, income and other demographic variables.

Between 1984-1990, drinking water in the Rathbun system had more positive detection's of alachlor, atrazine, cyanazine, metolachlor and 2,4-D than drinking water in other communities surveyed.  The mean level of atrazine in Rathbun was 2.2 micrograms/liter during this period compared to 0.8 micrograms/liter for other surface water supplies examined.

For cyanazine, the difference was 1.4 micrograms/liter in Rathbun compared to 0.7 micrograms/liter in other surface waters.

The study also compared birth records of babies born to mothers living in communities served by the Rathbun reservoir with babies whose mothers lived in the other southern Iowa communities.  Researchers found that communities in southern Iowa served by the Rathbun reservoir had a higher rate of slow fetal growth than the other communities included in the study.  During 1984 to 1990, the percentage of live births with slow fetal growth was 11.2% in the Rathbun communities compared to a range of 6.4%-6.9% in the other communities.

Statistical analyses revealed that atrazine, matolachlor and cyanazine were each significant predictors of community rates of slow fetal growth.  The researchers stated that a strong causal relationship cannot be inferred, however, owing to limitations in the study design.

Atrazine, cyanazine and metolachlor are widely used herbicides in the U.S. According to a recent review of pesticide use in the North American Great Lakes Basin, metolachlor, atrazine and cyanazine are, respectively, the first, second and seventh most used pesticides by weight in the region.  Due to concerns that atrazine and cyanazine pose serious health and environmental risks, the U.S. Environmental Protection Agency (EPA) put them in Special Review to examine their hazards and benefits in 1994.

Cyanazine was subsequently removed from Special Review because it is being phased out -- DuPont, its manufacturer, is withdrawing all uses in the U.S. by the end of 2002.  EPA expects to complete atrazine's Special Review by 1999.  EPA considers atrazine, cyanazine and metolachlor to be "possible human carcinogens."

Sources: Intrauterine Growth Retardation in Iowa Communitieswith Herbicide-Contaminated Drinking Water Supplies, Environmental Health Perspectives, Vol. 105, No. 3, March 1997;
Reducing Reliance on Pesticides in Great Lakes Basin Agriculture, 1997, World Wildlife Fund; Jeff Morris, special review manager, EPA, personal communication, July 7, 1997;
U.S. EPA Office of Pesticide Programs List of Chemicals Evaluated for Carcinogenic Potential, February 19, 1997.


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