The effect of lead on male fertility: A time to pregnancy (TTP) study

Background Growing attention has been paid in recent decades to the effects on male reproduction of occupational exposures to toxic agents. There is s trong evidence that high level exposure to lend, i.e. blood lend level (PbB ) > 70 mu g/dl, is associated with male infertility and some reports sugges t an effect even at lower PbB (i.e. < 50 mu g/dl). The aim of this study is to shed more light on the postulated association between occupational expo sure to relatively low levels of inorganic lead and reduced fertility ill m en estimated by the length of time taken to conceive: time to pregnancy (TT P), Population and Methods A survival analysis of Trp of the last pregnancy was performed adopting the Kaplan Meier methodology. The target population inc luded 782 lead-exposed workers and 165 controls. 251 lead workers and 119 c ontrols were finally eligible and interviewed. Lead-exposed subjects were d istributed into four exposure levels according to their blood lead concentr ation (i.e. <20; 20-29; 30-39, and greater than or equal to 40 mu g/dl). Th e Cox model was adopted to estimate the Relative Risk of unsuccessful waiti ng time to pregnancy associated to the exposure to lend. Results A statistically significant difference in fecundability (shorter TT P) in favor of exposed subjects was detected. Nevertheless, longer TTP was associated within the exposed group to higher levels of PbB, even though th e gradient is not statistically significant. The exposed workers revealed a n average number of children larger than those not exposed, and a clear gra dient of the same variable was evident from the lowest to the highest PbB l evel. Focusing on subjects with one child only, the Cox model confirmed no significant difference in fecundability between exposed and not exposed whe reas a statistically significant longer ITP was associated to the exposure level greater than or equal to 40 mu g/dl. Conclusions It is not easy to assert or to deny the effect of inorganic lea d on male fecundity, quantitatively estimated by TTP, with the data availab le for this study. In fact, while the general data seem to exclude effects of Pb on male fecundability a more detailed analysis suggests an unfavorabl e effect at relatively high levels of Exposure but some confounding attribu table to personal and social conditions of the workers cannot be ruled out. Further investigations with a better control of confounding are needed. Am . J. Ind. Med. 38:310-315, 2000. (C) 2000 Wiley-Liss, Inc.