Nov. 12, 2002 -- The quality of sperm differs dramatically around the country -- likely because of herbicides and fertilizers used in farming.
Strong evidence -- the first of its kind -- shows that men living in rural areas have significantly lower-quality sperm than men living in urban areas.
The study appears in the new online edition of Environmental Health Perspectives, a publication of the National Institute of Environmental Health Sciences.
In their report, researchers evaluated semen specimens from partners of 512 pregnant women recruited through prenatal clinics in four U.S. cities. Fertile men from mid-Missouri's Boone County had a mean sperm count of about 59 million per milliliter, compared to 103 million for men in New York, 99 million in Minnesota, and 81 million in Los Angeles. Normal sperm counts range from 40 to 150 million.
"Sperm concentration was significantly lower in Columbia, Mo. than in New York, Minneapolis, and Los Angeles," writes lead researcher Shanna H. Swan, PhD, with Family and Community medicine at the University of Missouri-Columbia School of Medicine.
The data suggest that sperm quality -- which they measure by count, shape, and movement of sperm -- may be affected by farming chemicals used in semi-rural and agricultural areas, she writes.
Over the past decade, other studies have made the same claim, Swan says. One study of sperm concentrations in nine countries ranged from 52 million in Bangkok to 103 million in Melbourne. Also, eight cities in France showed a wide range of sperm concentration. Other studies of cities in the U.S. have indicated wide variations.
In fact, several carefully controlled multi-center U.S. and international studies have been under way since 1997 -- all showing significant differences in sperm count and other qualities between fertile men recruited in Copenhagen, Paris, Edinburgh, and Turku (Finland).
In her study, Swan says she and her colleagues looked at population density, proportion of land in farms, and use of agricultural chemicals for the four cities as well as Iowa City, Iowa.
A recent U.S. Geologic Survey report on water quality noted extensive use of agricultural chemicals -- fertilizers, pesticides, or herbicides -- has resulted in widespread occurrence of herbicides in agricultural streams and shallow ground water in those areas, she reports.
Swan says she hopes to obtain funding for a study that will link pesticide exposure directly to sperm quality.
SOURCE: Environmental Health Perspectives, Nov. 11, 2002.