Letter to the editor

Scand J Work Environ Health 1997;23(4):308-310    pdf

https://doi.org/10.5271/sjweh.225 | Issue date: Aug 1997

Sex-ratio variation in the Bille settlement

by Fertmann R, Schümann M, Karmaus W, Schmid-Höpfner S, Küppers-Chinnow M

Integrating recent data on the sex ratio of births (measured as the proportion of boys among all newborns) James (1) related fathers' exposure to dioxin to significantly more daughters among their offspring. Mocarelli et al (2) described the sex ratio observed in Seveso for 74 total births during a period of 7 years with an excess of females (26 boys; 48 girls; sex ratio=0.351). Dimich-Ward (3) reported on significantly more daughters for workers in the sawmill industry and presumably exposed to chlorophenate wood preservatives (19 675 infants born from 1952--1985; sex ratio 0.486). Both ratios differ significantly from the expected sex ratio of 0.514. The Bille settlement east of Hamburg, Germany, was built in the 1950s on a contaminated sludge layer with high concentrations of arsenic (maximum 211 mg arsenic/kg soil), heavy metals (eg, cadmium maximum 18.6 mg/kg soil), and dioxins and furans (PCDD/F maximum 3855 ng/kg international toxicity equivalents according to NATO/ccms). From 1991 to 1996 an environmental health program was conducted to investigate the body load and possible health effects of the 700 inhabitants (4, 5). In 1991, when most of the families abandoned the settlement, 84 children up to 16 years of age were registered; their sex and age group are listed in table 1. There is a significant excess of male children in the younger subgroup. For the Bille settlement these registration data were validated by the results of the environmental health program. Questionnaires concerning the gynecological biography of women from the Bille settlement and the statistical analysis controlling for different windows of exposure disclosed similar results. Mothers exposed at the time of conception in the Bille settlement gave birth to 104 boys and 69 girls (sex ratio 0.60). In addition, it was observed that Bille couples displayed a prolonged time to pregnancy (6). The association between more male births and reduced fertility in the Bille sample contrasts with the recently published observation of Weijin & Olsen (7), who reported on an unselected Danish sample of mothers and found that more female births were related to reduced fertility. For the Bille inhabitants information about the body load of the contaminants before or during the time of conception is not available. Human monitoring in 1991 could not disclose significantly higher concentrations for the study group as a whole. Yet persons who had consumed home grown animal products had higher concentrations of dioxins and furans in their blood (range 21--214 I-TEQ ppt PCDD/F blood concentration, N=16) compared with persons with normal food consumption (range 12--84 I-TEQ ppt blood concentration, N=16) (7). Exposure estimates for the whole study group indicated surplus exposure, especially for those who had grown up in the Bille settlement and stayed there parenting the next generation (8). Our observation is contrary to the recently published data of Mocarelli et al (2) and Dimich-Ward et al (3). Any comparison of course has to consider weighty differences in exposure, exposure assessment, sample size, and structure. For example, Seveso as a well-known case of an accident deliberation, especially the congener TCCD in high concentrations contaminated men and women alike. On the other hand, Canadian study relates to wood preservatives encompassing a range of toxic substances contaminating male sawmill workers. At least the Bille settlement represents a sustained exposure to arsenic, heavy metals and PCDD/F for several generations of residents in contact with the soil and by consumption of home-grown food stuff, affecting males and females, children and adults, as well as the status of preconception and the pregnant status. On the basis of these different observations, we want to direct attention to 3 aspects. First, because of the lack of reliable exposure data, we have yet no evidence about the possible means of interference of xenobiotics during reproductive maturation or during fertilization, implantation, and early development. Could possibly xenobiotics disturb male rather than female fertility? Could further analyses reveal time-dependent effects of noxious agents like PCDD/F during especially susceptible periods of development? Should we rather investigate a distorted ratio of viable x/y sperm or male-female zygotes during early impregnation in the determination of sex ratio deviations at birth? How should we control for fetal loss, assuming a different sex ratio in fetuses? Second, corresponding to the data of Mocarelli et al, the Bille data pose the problem of small numbers. Empirical data present the variability of the sex ratio dependent on the denominator's size. For comparison our ongoing analysis includes a model of the distribution of sex ratio values with simulated data especially considering small birth cohorts (in preparation). Third, a follow-up study is planned to examine reproductive impairment of the Bille inhabitants after exposure has been dissolved.

This article refers to the following text of the Journal: 1997;23(1):69
The following article refers to this text: 1998;24(1):74-73