Change in semen quality and sperm chromatin structure following occupational styrene exposure

Objectives: Organic solvents have been suspected to exert detrimental effec ts on human spermiogenesis. Styrene, which is both mutagenic and neurotoxic , was selected as a suitable organic solvent for further assessment csf a p ossible effect on semen quality and sperm DNA damage. Subjects and methods: Semen samples were collected from 23 reinforced plastics workers at the ti me of employment and after 6 months of styrene exposure and from 21 nonexpo sed farmers. Intra-individual changes in conventional semen parameters and sperm-DNA denaturation patterns were related to the internal dose of styren e exposure as measured by postshift urinary mandelic acid. Results: A stati stically significant decline in sperm density was seen during styrene expos ure from 63.5 to 46.0 million sperm/ml, whereas no decline was seen in the nonexposed subjects. The total sperm count was almost halved from an initia l value of 175 million sperm/ejaculate. However, no relationship was appare nt when the sperm parameters were related to internal levels of exposure. H owever, an exposure-response relationship was shown for DNA-denaturation pa tterns, but the numbers were small. Conclusion: A declining sperm count fol lowing styrene exposure is suggested. However; the findings of the internal and external comparisons are inconsistent, and this may be due to the high intraindividual variability of semen parameters and the limited study size but may also be attributable to a weak internal exposure gradient. Spermat ogenesis may be vulnerable to styrene exposure. However, due to the small n umbers these findings are only preliminary.