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short-term tests on mice, rats, cattle and monkeys were positive in three cases (dominant lethal test and chromosomal damage to bone marrow cells) but negative in five others. Cytogenetic studies in humans exposed to lead, usually with blood lead levels above 40 µg/dL, are also conflicting, with seven negative reports and nine positive reports of chromatid and chromosomal aberrations, breaks and gaps.Footnote 114,Footnote 115 Gonadal dysfunction in men has been associated with blood lead levels of 40 to 50 µg/dL,Footnote 121,Footnote 122 and there may also be reproductive dysfunction in females occupationally exposed to lead.Footnote 20,Footnote 115 Increased spontaneous abortion and rates of stillbirths have been associated with lead intoxication of workers in the lead industry.Footnote 115 A link has also been suggested for lower, environmentally encountered levels. Miscarriage and stillbirth rates were elevated in the Australian lead smelter town of Port Pirie in comparison with a rural area matched for other variables. Blood lead levels averaged 10.6 µg/dL for Port Pirie women and 7.6 µg/dL for the controls.Footnote 123 Exposure of pregnant women to lead also increases the risk of pre-term delivery. In the study of 774 pregnant women in Port Pirie who were followed to the completion of their pregnancy, multivariate analysis revealed that the relative risk of pre-term delivery rose more than fourfold when blood lead levels rose from 8 to >14 µg/dL. If cases of late foetal death were excluded from the analysis, the association became even stronger, with the relative risk due to lead exposure increasing to 8.9 when blood lead levels exceeded 14 µg/dL.Footnote 123 Animal studies in rats lend support to the findings in humans, with effects at blood lead levels above 30 µg/dL on sperm counts and testicular atrophy in males and on oestrous cycles in females.Footnote 124,Footnote 125 In a survey of more than 4000 consecutive births, elevated cord blood lead levels were associated with minor malformations, such as angiomas, syndactylism and hydrocele in about 10% of all babies. The covariate-adjusted relative risk of malformation doubled at blood lead levels of about 7 to 10 µg/dL, and the incidence of any defect increased with increasing cord lead levels across the range in the population, from 0.7 to 35.1 µg/dL.Footnote 126
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