Certain jobs may impair semen, according to a Canadian study.
Researchers at the University of Calgary, Alberta, studied the semen of 845 men who ranged in age from 20 to 69. Thirteen aspects of semen quality were examined, including semen volume, sperm concentration, total sperm count and the percentage of defective sperm. The researchers analyzed the data by a variety of statistical methods.
Farmers' sperm concentration averaged 77.5 million sperm per milliliter, and the average for nonfarm workers was 87.7 million. These averages are several times higher than 20 million per milliliter, the level at which fertility is generally thought to be affected. However, the finding "supports the hypothesis that agricultural chemicals may affect male reproductive function in this employment population," the researchers wrote.
Eleven welders were in the study, and their semen showed a significantly lower percentage of "progressive" sperm--that is, sperm swimming in the right direction.
In addition, "increased stress was associated with a lower quality of semen quality" across the board, said the study's lead author, Philip L. Bigelow, an epidemiologist at Colorado State University in Fort Collins.
These findings don't prove that certain jobs are injurious, he said, but they suggest that further study would be worthwhile.
The study was reported recently in Fertility and Sterility, a journal of the American Society for Reproductive Medicine.