A recent study by Chinese researchers claims that men exposed to benzene at levels close to the permissible exposure limit in the United States are more likely to have an abnormal number of chromosomes in their sperm. Xing C, et al., “Benzene Exposure Near the US Permissible Limit Is Associated With Sperm Aneuploidy,” Environmental Health Perspectives, 10-1289, 2010. The researchers studied 66 male factory workers in Tianjin, China. Thirtythree of the men worked in factories that used benzene-containing adhesives to produce shoes, paper bags and sandpaper. Thirty-three worked in a meat-packing plant and an ice cream factory and were not exposed to benzene. To confirm benzene exposure, the men wore personal air monitors to measure benzene levels. Levels of benzene and benzene metabolites were also measured in the men’s urine.

The researchers found that as the men’s benzene exposure became higher, the number of sperm they produce with an extra chromosome also increased. Compared to men with no benzene exposure, those with low exposure were twice as likely to have sperm with two X chromosomes and men with high exposure to benzene were almost three times as likely. According to the researchers, the study raises questions as to whether the U.S. permissible limit for occupational benzene exposure is sufficient to provide protection from reproductive harm