Chronic exposure to a widely used pesticide may delay sexual maturity in boys, according to a new study in India.
Endosulfan is an organochlorine used around the world to protect squash, melons, strawberries, and other produce. A 2001 report by the U.S. Environmental Protection Agency estimated that 1.4 million pounds of the pesticide are used annually on U.S. crops. It's also the third most commonly used pesticide in India, where concerns about endosulfan have surfaced.
For example, for irrigation water and fish, the southern Indian town of Padre relies on streams that run through a cashew plantation where the trees had been sprayed with endosulfan a few times a year for 2 decades until December 2000. Residents then demanded that the spraying stop because they suspected it was increasing the local rates of several cancers and neurological diseases.
"Because of the particular topography, people were exposed to high concentrations of endosulfan," says Habibullah Saiyed of the National Institute of Occupational Health in Ahmedabad, India. Even though endosulfan doesn't last long in the body, it can linger in the food chain by contaminating soil and accumulating in fish.
Saiyed and his colleagues collected blood from Padre residents and village-water samples 10 months after the last spray. "They were still showing endosulfan," Saiyed says.
Since previous experiments in laboratory rats had linked high endosulfan exposure during development to defects in sperm quality, the researchers investigated possible effects of the compound on human male-reproductive development. The team examined 117 Padre schoolboys between 10 and 19 years old and a comparable group of boys from a town 20 kilometers away, where there had been no endosulfan spraying.
Blood tests indicated the pesticide's presence in more than three-quarters of the boys in the Padre group, whereas less than a third of the control group's blood samples showed endosulfan. The results demonstrate the overall environmental prevalence of this pesticide, Saiyed says.
Reproductive development of each boy was evaluated using a sexual-maturity rating based on the size of the penis and testes and the development of pubic hair. After taking age into account, the researchers found that boys in Padre scored significantly lower on all three measurements than boys from the other village did. The scientists report their findings in the December Environmental Health Perspectives.
They also found that the blood concentration of testosterone was lower in the Padre boys, even though they had higher concentrations of luteinizing hormone than the other boys did. Luteinizing hormone normally pumps up production of testosterone, so the results imply that something is impeding testosterone synthesis and therefore the progression of puberty, the researchers say.
"The findings really suggest that we should use [endosulfan] cautiously or not use it at all," says Saiyed, adding that this is one of the first studies to link an environmental pollutant to delayed puberty in boys.
Richard Sharpe of the Medical Research Council's Centre for Reproductive Biology in Edinburgh says the study ought to raise concerns, but because it looked at only a small number of children, the results may simply represent natural variations in the onset of puberty.
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