Occupational Exposure to Benzene and Chromosomal Structural Aberrations in the Sperm of Chinese Men

Abstract

Background: Benzene is an industrial chemical that causes blood disorders, including acute myeloid leukemia. We previously reported that occupational exposures near the U.S. Occupational Safety and Health Administration permissible exposure limit (8 hr) of 1 ppm was associated with sperm aneuploidy.Objective: We investigated whether occupational exposures near 1 ppm increase the incidence of sperm carrying structural chromosomal aberrations.Methods: We applied a sperm fluorescence in situ hybridization assay to measure frequencies of sperm carrying partial chromosomal duplications or deletions of 1cen or 1p36.3 or breaks within 1cen-1q12 among 30 benzene-exposed and 11 unexposed workers in Tianjin, China, as part of the China Benzene and Sperm Study (C-BASS). Exposed workers were categorized into low-, moderate-, and high-exposure groups based on urinary benzene (medians: 2.9, 11.0, and 110.6 µg/L, respectively). Median air benzene concentrations in the three exposure groups were 1.2, 3.7, and 8.4 ppm, respectively.Results: Adjusted incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for all structural aberrations combined were 1.42 (95% CI: 1.10, 1.83), 1.44 (95% CI: 1.12, 1.85), and 1.75 (95% CI: 1.36, 2.24) and for deletion of 1p36.3 alone were 4.31 (95% CI: 1.18, 15.78), 6.02 (95% CI: 1.69, 21.39), and 7.88 (95% CI: 2.21, 28.05) for men with low, moderate, and high exposure, respectively, compared with unexposed men. Chromosome breaks were significantly increased in the high-exposure group [IRR 1.49 (95% CI: 1.10, 2.02)].Conclusions: Occupational exposures to benzene were associated with increased incidence of chromosomally defective sperm, raising concerns for worker infertility and spontaneous abortions as well as mental retardation and inherited defects in their children. Our sperm findings point to benzene as a possible risk factor for de novo 1p36 deletion syndrome. Because chromosomal aberrations in sperm can arise from defective stem cells/spermatogonia, our findings raise concerns that occupational exposure to benzene may have persistent reproductive effects in formerly exposed workers.

Current understandings and perspectives on non-cancer health effects of benzene: A global concern

“…Benzene exposure may also cause increase in aneuploidy of sperm sex chromosomes and producing chromosomally defective sperms (Liu et al, 2000, Marchetti et al, 2012.…”

“…Chromosomal aberration is a deleterious event whose induction in sperm cells can lead to infertility (Marchetti et al, 2012) and to some extent, carcinogenic effect of benzene has been thought to be mediated by its metabolite quinone; a potent inducer of sister chromatid exchange (Eastmond, 1993, Zhang et al, 2002. However, carcinogenicity of benzene involves a complex of mechanisms including DNA mutation, chromosomal damage, oncogene activation, inhibition of gap-junction intercellular communication and down-regulation of host tumor control mechanism by benzene metabolites and free radicals (Atkinson, 2009, Rivedal and Witz, 2005, Uzma et al, 2010.…”

Association between occupational exposure to benzene and chromosomal alterations in lymphocytes of Brazilian petrochemical workers removed from exposure

“…These data are supported by other studies that have shown that individuals exposed to benzene for long periods presented with persistent hematological and genetic damage. In addition, studies of individuals exposed to benzene reported gaps and chromosomal breaks as the chromosomal abnormalities most often detected (Santiago et al 2014;Marchetti et al 2012). However, because of the small sample size and possible confounding factors, studies are still needed to clarify the genotoxic effects of benzene even after cessation of occupational exposure.…”

Benzene exposure from the BP refinery flaring incident alters hematological and hepatic functions among smoking subjects

“…Benzene exposure may affect the bone marrow leading to anemia and the development of cancer. Exposure to benzene may cause leukemia, lymphoma, multiple myeloma, aplastic anemia, and other solid cancers [2][3][4][5][6]. In addition, benzene exposure is associated with a wide range of non-cancerous but adverse effects including alterations in pulmonary, central nervous system, hematological, hepatic, and renal functions [7][8][9][10][11].…”