Too much or too little environmental exposure to the mineral manganese can reduce sperm quality and quantity, perhaps leading to male infertility. Manganese is found naturally in the environment and is also released into the air from mining and manufacturing operations and from combustion of gasoline additives. Human exposure to ambient levels of manganese is universal and mainly occurs via air and dust exposure. Trace amounts of manganese are needed for normal sperm function, but high levels have been shown to harm male fertility. Researchers from Michigan State University, USA, measured blood levels of manganese in 200 men visiting infertility clinics between 2003 and 2005. It was found that men with high manganese levels had a greater than 5-fold higher likelihood of low sperm motility, meaning that less than 50 percent of their sperm were moving. Men with high manganese levels were also 2.5 fold more likely to have low sperm counts. Low blood manganese levels were also associated with low sperm motility and concentration, although not as strongly. Low manganese might adversely affect sperm quality, given that this mineral plays a critical role in many metabolic processes, including reproduction. The findings are important because the high manganese level was at or above the normal range for manganese in blood, while the low level was within the normal range, suggesting that low ambient levels of manganese are a potential risk factor for poor semen quality.
Epidemiology,
April 2007