The workers collected the first morning urine (first urine after midnight) on the day after sampling of air and blood. We gave the participants 250 ml low-density polyethylene flasks (VWR International, Sweden); we also provided the women with a polypropylene funnel (VWR International, Sweden). Upon arrival at work, the urine was transferred to 25 ml low-density polypropylene test tubes and placed in the portable refrigerator.