The research team focused on over 1200 manual workers attending fertility clinics in Canada between 1972 and 1991. Over 600 of the men were patients at one clinic in Montreal; the remainder came from 10 clinics across the country who attended for treatment between 1984 to 1987. Each job was graded according to level of solvent exposure. Semen samples were analysed for volume and activity.
After taking into account other factors likely to influence the results, the results showed that men exposed to moderate occupational levels were over twice as likely to have low sperm counts, with low numbers of active sperm. Men exposed to high levels-50 per cent above the threshold-were around three times as likely to have low sperm counts. Painters and decorators, builders, and printers had the highest risk.
The authors admit that some of the infertile men might have been exposed to lead, but the only common factor for all of them was repeated exposure to organic solvents. The authors are not able to pinpoint which of the solvents is most hazardous for male fertility, but suggest that prime candidates could be glycol ethers, known to affect the reproductive systems of animals.
[Occupational exposure to solvents and male infertility 2001; 58: 635-40]