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A new study adds to the growing literature suggesting that chemical exposure may affect male fertility.
Men exposed to higher levels of combustion by-products had an increased risk of infertility, according to results from a study conducted in China.
A decline in male fertility has been observed in recent years, and some scientists have proposed that exposure to endocrine disrupting chemicals, such as PAHs, may be to blame. PAHs are a class of chemicals that are released in the atmosphere, soil and water as a result of the incomplete burning of a range of substances including coal, oil, gas, wood, refuse and other organic substances. These chemicals are classified as probable carcinogens by the International Agency for Research on Cancer.
Researchers found that infertile males with abnormal semen quality (based on sperm concentration, number of sperm per sample, sperm motility and semen volume) had a 14 percent increase in median exposure to total PAHs relative to fertile men and slightly higher median PAH concentrations than infertile men with otherwise normal semen quality. Men with higher PAH exposure had a 53 percent increased risk of infertility than men with lower exposure.
The influence of the pollutants on infertility varied. Some PAHs had more of a risk of affecting the men's semen quality than others. Two in particular – called I-OHP (I-hydroxypyrene) and 2-OHF (2-hydroxyfluorene) – showed the strongest associations. I-OHP is one of highest measured PAHs in the US population and has been found in prior human and laboratory studies to affect semen quality at everyday exposure levels.
These results were obtained after researchers compared PAH residues in the urine of 513 infertile men with 273 fertile men.
It is however limited by the fact that exposure could not be directly determined. Instead, PAH residues in urine were measured, representing only a few days of exposure.
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