Stay Away From Benzene

July 25, 2010

Yet another chemical exposure hazard has been revealed as a danger to male fertility. This time it's benzene, which according to a study written up in Environmental Health Perspectives may cause fluctuations in sperm chromosomal counts. The researchers involved in the study found that male exposure to benzene levels within the upper limits approved by the U.S. will cause too many or too few chromosomes to be present in male sperm.

This type of abnormal chromosomal count in sperm is called aneuploidy and is known to hinder male fertility and pose obstacles to fetal development. Aneuploidy is held to be the commonest cause of miscarriage.

The study on benzene focused on 66 Tianjin, China factory workers. One half of the study participants worked in factories using benzene-containing adhesives in the manufacturing process for making paper bags, shoes, and sandpaper. The factories use monitors within the workplace to measure the air levels of benzene. In addition to making use of these monitors to confirm the participants' exposure to high levels of benzene, the researchers also performed urine tests on the workers to assess for urine levels of benzene and benzene metabolites.

A common industrial chemical, benzene is used in rubber products, solvents, gasoline, marking pens, and paint. Benzene is also a byproduct of cigarette smoke and vehicular exhaust.

The researchers found an equal number of participants to serve as a control group. These 33 male participants worked in two industries in which the use of benzene is not employed: a meatpacking plant and an ice cream factory.

Upper Limits

Three groups were formed for comparing sperm aneuploidy, based on urine levels of benzene metabolites. A full half of the participants showed no exposure, 17 presented with low-level exposure, and 16 showed signs of high level exposure to benzene. Low benzene exposure was defined as exposure to benzene levels that near the upper U.S. government safety standards' limits for on-the-job benzene exposure.

The researchers than analyzed the chromosome count in 10,000 sperm per participant to see how many sperm presented with aneuploidy. It was discovered that men with the highest workplace exposure to benzene presented with a two to threefold risk for aneuploidy in comparison with men who had no such exposure to this chemical. Men in the low-exposure group had twice the risk for some sperm containing two X chromosomes.

Klinefelter Syndrome

The significance of these results lies in the fact that the low exposure group had been exposed to levels of benzene considered safe by U.S. government standards. If a child should be conceived by sperm affected with aneuploidy, the result may be miscarriage or a child with a chromosomal disorder such as Klinefelter Syndrome (X-X-Y).

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