Researchers in China have documented a link between high levels of exposure to magnetic fields and abnormal sperm quality. Their research, published in Reproductive Toxicology showed that men with levels of exposure in the top 10% of subjects were twice as likely to have poor sperm quality, meaning that their sperm was badly shaped or didn’t swim properly. This study may explain why there has been a worldwide decrease in sperm quality and why the decline is higher in urban areas than in rural ones. The difference between urban and rural males indicates that pesticides are not a likely culprit as pesticide exposure is higher in rural areas while exposure to magnetic fields is higher in urban areas.
In this case-control study, participants were healthy males recruited from a sperm bank, a procedure that eliminated men with obvious sexual difficulties. Sperm quality was assessed using criteria outlined by the World Health Organization (WHO). Poor sperm quality was defined as low motility, improper shape, or low sperm concentration. Men with poor sperm quality were assiged to the case group while men with normal sperm were assigned to the control group. The men were unaware of which group they had been asssigned to. Magnetic field exposure was measured directly with meters the men wore during the day and placed by their beds at night.
Since sperm production takes about ninety days, men who had experienced significant lifestyle changes in the previous three months—vacations or changes in workplace or residence—were excluded. Those with medical conditions that could compromise their fertility were eliminated from the study as were subjects exposed to high heat, solvents, pesticides, or industrial chemicals. Regression analysis controlled for exposure to cigarettes and alcohol.
The results showed a clear correlation between magnetic field exposure and reduced sperm quality. These results were not linked to the usual social and economic characteristics like income and educational level. Importantly, the data showed a dose-response relationship, meaning that greater exposure resulted in an increased level of abnormality. Men exposed to less than one hour a day of strong magnetic fields, defined as being greater than 1.6 milligauss, had lower levels of sperm abnormality than men exposed for up to three hours a day. Men exposed to high magnetic fields for more than six hours per day had the highest levels of impaired sperm. The presence of a dose-effect response is further confirmation that the effect is really due to magnetic fields and not some other factor that might often be associated with them such as, for example, a modern highly processed diet or exposure to a toxin. When men were asked to assess whether the measurement day a typical day for the last three months, the association became even stronger.
The study avoids several of the pitfalls often found in human research. Because the subjects were recruited from a sperm bank, the researchers avoided the self-selection bias often found in clinical studies. Previous studies on electrical and magnetic fields have often used indirect measurements but in this study, meters were used to measure the direct, personal exposure of the subjects. Furthermore, regression analysis found that the two groups were highly similar and did not differ significantly from each other on common socio-economic measures like education and income. A possible drawback of the study is that there can be no true control group in such a study because everyone in the modern world is exposed to man-made magnetic fields. The lack of a true control group in this case would probably underestimate the effects of magnetic fields.
This research has ramifications far beyond the issue of fertility. Because sperm quality is easier to assess than the functions of many internal organs, it is possible that the decline in sperm quality may be only the “tip of the iceberg” of a larger public health issue.
De-Kun Li, Bei Yanb, Zheng Li, Ersheng Gaoc, Maohua Miaob, Dongming Gongd, XiaoPing Wenga, Jeanette R. Ferbera, Wei Yuanc, Exposure to Magnetic Fields and Poor Sperm Quality. Reproductive Toxicology 29 (2010) 86-92