Department of Biology, University of Rome 'La Sapienza', 00185 Rome, Italy
SirA 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 chambers1 and among professional drivers,2 applicators of dibromochloropropane,3 carbon setters4 and aluminum smelter workers.5 Weijin and Olsen6 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.
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However, among welders Bonde8 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 susceptibility of the fetuses, to early undetected pregnancy loss. This hypothesis is compatible with alterations of the sex ratio observed in Danish female physiotherapists.9
The question is certainly intriguing, and since gender ratio is an easily accessible epidemiological indicator, its study in particular occupationally exposed populations, may prove cost-effective.
References
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2 Sas M, Szollosi J. Impaired spermiogenesis as a common finding among professional drivers. Arch Andr 1979;3:5760.[ISI]
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4 Milham S. Unusual sex ratio of births to carbon setter fathers. Am J Ind Med 1993;23:82931.[ISI][Medline]
5 Irgens A. Personal communication. 1996.
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7 James WH. Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels at the time of conception. J Theor Biol 1996;180:27186.[ISI][Medline]
8 Bonde JPE, Olsen JH, Hansen KS. Adverse pregnancy outcome and childhood malignancy with reference to paternal welding exposure. Scand J Work Environ Health 1992;18:16977.[ISI][Medline]
9 Gubéran E, Campana A, Faval P et al. Gender ratio of offspring and exposure to shortwave radiation among female physiotherapists. Scand J Work Environ Health 1994;20:34548.[ISI][Medline]