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Reduced fertility among shoe manufacturing workers
  1. M Sallmén1,
  2. M Neto2,
  3. O N Mayan3
  1. 1
    Centre of Expertise for Health and Work Ability, Finnish Institute of Occupational Health, Helsinki, Finland
  2. 2
    Regional Centre of Public Health, Porto, Portugal
  3. 3
    Centre of Environmental and Occupational Health, National Institute of Health, Porto, Portugal
  1. Dr M Sallmén, Centre of Expertise for Health and Work Ability, Finnish Institute of Occupational Health, Topeliuksenkatu 41 aA, FI-00250 Helsinki, Finland; Markku.Sallmen{at}


Objectives: To investigate whether fertility is reduced among female shoe manufacturing workers exposed to organic solvents.

Methods: A retrospective study was conducted 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. Data on TTP and related factors were collected 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 in the workplaces. TTP data were analysed with discrete proportional hazards regression.

Results: Female exposure to solvents was associated with reduced fertility (adjusted fecundability density ratio (FDR) 0.55, CI 0.40 to 0.74 for low exposure, and FDR 0.70, CI 0.52 to 0.94 for high exposure). The findings were robust in different sensitivity analyses. A slightly stronger association was found among women with regular menstrual cycles. Exposure for less than 6 years was more strongly associated with reduced fertility (FDR 0.50, CI 0.30 to 0.83 and FDR 0.50, CI 0.28 to 0.90 for low and high exposure, respectively) than at least 6 years of exposure (FDR 0.60, CI 0.39 to 0.92 and FDR 0.86, CI 0.57 to 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: The 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.

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  • Competing interests: None.