Reduction in male births among workers exposed to metal fumes.

Sir—A number of reports suggest that some occupational exposures of males may alter the gender ratio of their offspring. Reduction in male offspring has been observed after exposures to hyperbaric chambers 1 and among professional drivers, 2 applicators of dibromochloropropane, 3 carbon setters 4 and aluminum smelter workers. 5 Weijin and Olsen 6 have suggested that offspring gender ratio, because of its correlation with reduced fertility, may be a possible epidemiological indicator of reproductive hazards. We have conducted a study to evaluate the possible role of exposure to metal fumes (particularly nickel and chromium) on the reproductive health of male workers in an Italian mint. The study was designed to evaluate specifically fertility problems, and the observed reduction in fertility is reported separately. We also noted, however, an interesting alteration of the gender ratio with reduced male births which we feel is worth reporting. The workers were divided into administrative staff (non-exposed to metal fumes), technical and maintenance staff (with minimal exposure), coin stampers (exposed to metal fumes) and founders (highly exposed to metal fumes). Air sampling and biological monitoring of workers yielded concentrations of metals within the TLV-ACGIH. However, the blood nickel levels were very near the biological reference value of 0.5 µg/dl, especially among founders. The proportion of male children among all offspring born to these men while working in the four job categories is shown in Table 1. Founders had a significantly reduced proportion of male children when compared to both the administrative staff and to the general population, where the proportion of males is 51%. We focused more specifically on the most recent birth of these workers, because information on exposure was more detailed for the last pregnancy of the couple. Again we note a reduction in the births of males among founders, which is statistically significant. The limited number of cases included in our study do not allow a conclusion, but these data add to the evidence that occupational exposure might affect the gender ratio in favour of female births. The mechanism of this effect is under debate. James 7 hypothesized that gender ratio is affected by hormone concentration. High levels of gonadotropin and low levels of testosterone, favour the production of daughters. However, among welders Bonde 8 has observed hormonal alterations, poor semen quality and reduced fertility but no alteration in the gender ratio. The other possible mechanism may be related to a greater …