These studies were initiated by the results of two Danish investigations of
infertility clients, which indicated the reduced fecundity of male
metal welders. The objective was to refute or corroborate the effects of welding on male reproductive capability and--if there was any effect--to identify the causal exposures. The initial hypothesis postulated reduced spermatogenesis,
spontaneous abortion, congenital malformation and childhood
malignancy following exposure to
hexavalent chromium among
stainless steel welders. Subsequently, a hypothesis concerned with the significance of exposure to radiant heat on reduced semen quality was put forward. These studies comprised a case-referent study of
infertility, cross-sectional and longitudinal studies of semen quality and historical cohort studies of fertility, pregnancy outcome and
cancer in offspring. Exposure to welding was reported with a higher frequency during periods of
infertility than prior to conception in the case-referent study (OR 2.0, 95% CI 1.0-4.0). This finding is consistent with the main cross-sectional study showing reduced semen quality in welders [average reduction ranging from 8% (sperm penetration rate in eggwhite) to 28% (total sperm count)] and with the cohort study revealing reduced fertility in relation to welding (OR 0.89, 95% CI 0.83-0.97). However, reduced semen quality and fertility were not attributable to the welding of
stainless steel but to the welding of mild steel; and no relationship was found between
biological measures of exposure to
chromium and parameters of semen quality. If the unexpected association between mild steel welding and reduced fecundity is causal, the
biological mechanisms involved are obscure. A separate longitudinal study leaves little doubt that moderate radiant heat exposure may cause reversible deterioration of semen quality, but it is not justified to generalize this observation to the entire population of welders. Male-mediated effects on occurrence of congenital malformation and
cancer in offspring from
stainless steel welding are not indicated by the studies. Weak indications of an increased risk of
spontaneous abortion among partners to
stainless steel welders (OR 1.9, 95% CI 1.1-3.2) need to be refuted or corroborated in future studies. Suggested effects of mild steel welding on male fecundity should be corroborated by longitudinal controlled studies of semen quality examined before and during exposure and by prospective studies of fecundability in couples trying to conceive a child. On account of the present knowledge it is not possible to recommend rational preventative measures with the exception of elimination of radiant heat exposure in cases of
infertility.(ABSTRACT TRUNCATED AT 400 WORDS)