Benzene exposure near the U.S. permissible limit is associated with sperm aneuploidy.
Environ Health Perspect. 2010 Jan 6. Epub 2010 Jan 6. PMID: 20418200
Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
Background: Benzene is a common industrial chemical that is known to induce leukemia and other blood disorders, as well as aneuploidy in both human blood cells and sperm at exposures above 10 ppm. Recent reports have identified health effects at exposure levels below 1 ppm, the Permissible Exposure Limit (PEL; 8 hour) set by US OSHA. Objective: To investigate whether occupational exposures to benzene near 1 ppm induce aneuploidy in sperm. Methods: We used multi-color 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 personal air monitoring, urinary benzene and urinary trans,trans-muconic acid (E,E-MA). Air benzene concentrations were not detectable in unexposed men and ranged from below the detection limit to 24 ppm in exposed men (median = 2.9 ppm) with 27% of exposed men (n=9) at or below 1 ppm. Exposed men were categorized into low and high groups based on urinary E,E-MA (median concentrations of 1.9 and 14.4 mg/L, respectively; median air benzene of 1 and 7.7 ppm, respectively) and aneuploidy frequencies were compared to unexposed men. Results: Sperm aneuploidy increased across low- and high-exposed groups for disomy X (IRR [95% CI]=2.0 [1.1, 3.4]&2.8 [1.5, 4.9]), and overall hyperhaploidy for the three chromosomes investigated (IRR [95% CI]=1.6 [1.0, 2.4]&2.3 [1.5, 3.6]). We also found elevated disomy X and hyperhaploidy in the 9 men exposed at or below 1ppm compared to unexposed men (IRR [95%CI]=1.8 [1.1, 3.0]&2.0 [1.1, 3.9], respectively). Conclusions: 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 US PEL.