In humans, testicles normally operate at temperature 2 to 4°C below that of the body. Numerous epidemiological studies have indicated a possible effect of occupational or social exposure to heat on male fertility. Professional drivers, ceramic workers, bakers, and welders have been shown to have either decreased motility or abnormal sperm morphology. The concept of infertility due to genital "overheating" in these occupations is consistent with the finding of increased semen quality in men who discontinue chronic exposure to hot tubs and warm baths.
Several different forms of radiation have been implicated in male infertility. Patients working with radiation and electromagnetic waves may have decreased rates of fertility. This has also raised the possibility that cell phones and laptops could lead to changes in semen parameters.[23,24,25] Current studies are conflicting regarding cell phone usage, although some studies have shown a decrease in testicular size and abnormal morphology, particularly in groups that used their cell phone more than 4 hours daily.[23,25] A recent study by Avendaño et al exposed human sperm to a laptop connected to Wi-Fi. A control group examined sperm placed more distance away from a computer. After 4 hours, 25% of the sperm exposed to Wi-Fi stopped moving forward, and 9% showed DNA damage. In contrast, only 14% of the sperm placed some distance from the Wi-Fi-equipped computer stopped moving forward and 3% showed DNA damage. This was attributed to both radio-frequency electromagnetic waves and heat from the laptop. However, given that Wi-Fi frequencies exhibit 10-fold less energy than cell phones, further studies are needed to confirm a possible effect of Wi-Fi on sperm.
Several studies have looked at semen quality of workers exposed to pesticides.[26,27,28,29] Sperm concentrations have been shown to be lower in studies performed in Denmark and China. A meta-analysis by Jurewicz et al suggests that there is a significant decrease in total sperm count among subjects with the highest exposure to organopesticides. In another study, farmers exposed to pesticides in Argentina were noted to have lower LH concentrations and higher estrogen levels. Pesticide exposures are considered a classic reproductive toxin and are thought to affect male fertility by acting in an estrogenic manner.
Semin Reprod Med. 2013;31(4):286-292. © 2013 Thieme Medical Publishers