Reduced fertility among shoe manufacturing workers

¹ Finnish Institute of Occupational Health, Finland
² Regional Centre of Public Health, Porto, Portugal
³ National Institute of Health, Porto, Portugal

^* To whom correspondence should be addressed. E-mail: markku.sallmen{at}ttl.fi.

Accepted 2 November 2007

	Abstract

Objectives: To investigate whether fertility is reduced among female shoe manufacturing workers exposed organic solvents. Methods: We conducted a retrospective study on time to pregnancy (TTP) among 250 Portuguese shoe manufacturing workers exposed to solvents and 250 unexposed women working in stores of food units and storehouses. We collected data on TTP and related factors by face-to-face interviews. The participation rate was 92%, and 81% of the workers (197 exposed women and 209 unexposed women) provided data for the analyses. Exposure assessment was based on hygienic measurements at the work places. Time-to-pregnancy data were analyzed with the discrete proportional hazards regression. Results: Female exposure to solvents was associated with reduced fertility (adjusted fecundability density ratio (FDR) 0.55, CI 0.40–0.74 for low exposure, and FDR 0.70, CI 0.52–0.94 for high exposure). The findings were robust in different sensitivity analyses. A slightly stronger association was found among women with regular menstrual cycle. Exposure for less than six years was more strongly associated with reduced fertility (FDRs 0.50, CI 0.30–0.83 and FDR 0.50, CI 0.28–0.90 for low and high exposure, respectively) than at least six years of exposure (FDR 0.60, CI 0.39–0.92 and FDR 0.86, CI 0.57–1.29 for low and high exposure, respectively). There was an interaction between solvent exposure and female smoking or use of coffee, the exposed women who smoke or use coffee being highly fecund. Conclusions: Our findings provide further evidence that exposure to organic solvents is hazardous for female reproduction. The observed association may be related to any of the following solvents commonly used in shoe manufacturing: n-hexane and hexane isomers, toluene, methyl ethyl ketone, acetone, ethyl acetate and dichloromethane.

Keywords: fecundability, female effects, fertility, shoe manufacturing, solvent exposure

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