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Int J Epidemiol. 1997 Dec;26(6):1281-8.

Fertility of Danish battery workers exposed to lead.

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Department of Occupational Medicine, University Hospital of Aarhus, Denmark.



Inorganic lead may impair male fecundity through its action on the germinal epithelium, the endocrine system or both, but information on possible impact on fertility in exposed populations is limited.


Fertility was examined in 1349 male battery plant employees and in 9596 reference company employees over a follow-up of 25,949 and 183,414 person years respectively. The cohorts were identified by records in a national pension fund and information on births was obtained from the Danish Population Register. In a subset of the battery worker cohort, the average level of lead in blood was 35.9 micrograms/dl (4639 blood samples on 1654 person years in 400 workers; SD 13.0; range 3-125). The birth rate was analysed by logistic regression on occupational exposure and several extraneous determinants (age, parity, calendar year, and previous children).


The birth-rate was not reduced in years at risk from exposure to lead in comparison with years not-at-risk; either in comparison with not-at-risk years within the battery plant cohort (odds ratio [OR] = 0.997, 95% confidence interval [CI]: 0.88-1.13), or in comparison with the external reference population (OR = 0.983, 95% CI: 0.87-1.11).


Inorganic lead seems not to impair fertility among Danish battery workers. This finding does not rule out that the time taken to achieve a pregnancy is increased among battery workers because most pregnancies in Denmark are planned.


This study examined the effects of exposure to lead among battery workers on fertility in Denmark. The research methods were based on an earlier study among metal workers. The sample population included a cohort of 1349 men born in 1940 or after who worked at 3 Danish battery plants between April 1, 1964 and December 31, 1992. The plants were located in different parts of the country. The control population included 9596 workers from 86 Danish manufacturing steel, wooden boat, and plastics products companies. All workers were considered to be exposed to lead during their period of employment. Biological monitoring of blood lead levels (BLLs) was conducted during 1983-88 among 400 workers, or 4639 blood samples. The average BLL was 39.2 mcg/dl. Average BLLs declined slightly during follow-up. More samples were taken from workers with high BLLs. Findings indicate that employment at a Danish battery plant was not associated with any change in fertility, as measured by the birthrate, during either the years of employment or subsequent years. There was no indication that long-term exposure was related to reduced fertility. Reduced fecundity, which is correlated with exposure to lead, may not necessarily result in reduced fertility. Reduced fecundity may be counteracted by an increased number of menstrual cycles exposed to sperm. The most important factors that mediate between reduced fecundity and reduced fertility are the extent of reproductive impairment, the number of desired children, and the timing of initiation of sexual activity during the reproductive period. Several European countries are involved in studies to determine the impact on time-to-pregnancy and semen quality in lead-exposed populations.

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