12 December 2002
Farm Chemical Use Linked To Sperm Quality
by George Atkinson

For the first time, researchers have found convincing evidence that semen quality differs significantly between regions of the United States. Study results suggest that fertile men in more rural areas have lower sperm counts and less vigorous sperm than men in urban areas. Researchers at the University of Missouri-Columbia and their collaborators believe that environmental factors, such as extensive use of agricultural chemicals, might contribute to these differences.

Dr. Shanna H. Swan, an epidemiologist and research professor of Family and Community Medicine, led a group of researchers who studied 512 couples receiving prenatal care at clinics in Columbia, Mo., Minneapolis, Los Angeles, and New York as part of the ongoing Study for Future Families funded by the National Institutes of Health (NIH). Swan found that semen quality was equally high in Minneapolis and New York, and slightly lower in Los Angeles. However, men in mid-Missouri had counts and quality that were significantly lower than men from any of the urban centers.

"We believe that agricultural chemicals could be contributing to this decrease in semen quality," Swan said. "The county in which our Missouri participants lived is quite rural. In 1997, 57 percent of the land was used for farming, compared to 0 to 19 percent for the other three counties we studied. We are continuing this research and examining the exposure of men to specific chemicals used in farming." Prior studies of semen quality were often conducted in large metropolitan areas. The only other published study on a comparable semi-rural population analyzed semen quality among men in Iowa City, and also found reduced sperm concentration. Swan and her colleagues are now studying semen quality in Iowa City.

Since the 1930s, there has been considerable interest in semen quality as a key predictor of male reproductive dysfunction. However, semen analyses are very sensitive to laboratory methods, the equipment employed, and the nature of the population, all of which may vary from one study to another. The detailed and rigorously applied protocol used by this research team supported the differences between geographic areas after adjusting for other factors known to alter sperm quality such as age, smoking and recent fever.

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