A new study by researchers at the Lawrence Berkeley National Laboratory found numerical abnormalities in the sperm of men exposed to benzene near the permissible exposure limit.

The investigators used multicolor fluorescence in situ hybridization to measure the incidence of sperm with numerical abnormalities of chromosomes X, Y, and 21 among 33 benzene-exposed men and 33 unexposed men from Chinese factories. Individual exposures were assessed using both air monitoring and biological monitoring.  Exposed men were categorized into low and high groups and aneuploidy frequencies were compared with those of unexposed men.  They found a significant doubling of disomy X and a 60% increase for overall hyperhaploidy for the three chromosomes investigated.  Notably, they found significantly elevated disomy X and hyperhaploidy in the nine men exposed to </= 1 ppm benzene compared with unexposed men.  The researchers concluded that benzene appeared to increase the frequencies of aneuploid sperm for chromosomes associated with chromosomal abnormality syndromes in human offspring, even in men whose air benzene exposure was at or below the U.S. permissible exposure limit.  The study raises serious concerns that men exposed to benzene at the current exposure limit have chromosomal abnormalities in their sperm which may impair their reproductive health and present a risk of congenital abnormalities and cancer in their children.  The study adds to the mounting evidence that even at the current exposure limit of just 1 ppm, benzene is harmful not only to the health of workers but also to their unborn their children.  The citation for the study is:

Xing, C., et al., “Benzene exposure near the u.s. Permissible limit is associated with sperm aneuploidy,” Environ Health Perspect. 118(6):833-839 (June 2010).