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International Agency for Research on Cancer (IARC) - Summaries & Evaluations

LEAD AND LEAD COMPOUNDS

VOL.: 23 (1980) (p. 325)

5. Summary of Data Reported and Evaluation

5.1 Animal carcinogenicity data

Lead acetate, lead subacetate and lead phosphate are carcinogenic to rats and lead subacetate to mice: these compounds induced benign and malignant tumours of the kidney following oral or parenteral administration. Gliomas occurred in rats given lead acetate or lead subacetate by the oral route.

When tetraethyllead was administered by subcutaneous injection to neonatal mice, an increased incidence of lymphomas occurred in female animals only; additional studies are required before an evaluation of the carcinogenicity of this compound can be made.

No evaluation could be made of the carcinogenicity of lead arsenate, lead carbonate, lead oxide, metallic lead powder, lead naphthenate or lead nitrate.

Lead chloride gave positive results in DNA misincorporation tests. Lead acetate induced morphological transformations in Syrian hamster cells. There is no evidence that lead acetate or lead chloride induces mutations or allied effects in bacteria; some chromosomal aberration tests in mammalian systems (either in vitro or in vivo) have given positive results. There was insufficient evidence to evaluate the mutagenicity of organometallic lead compounds.

Lead salts have been reported to cross the placenta and to induce embryo- and fetomortality. They also have a teratogenic effect in some animal species. No teratogenic effects have been reported with exposure to organometallic lead compounds.

5.2 Human carcinogenicity data

Three epidemiological studies have been made of workers who were exposed to either lead and inorganic lead compounds or to tetraethyllead. One of the two studies on metallic lead workers showed no excess of cancer deaths. The other showed a slight (although not significant) excess of deaths due to cancers of the digestive system and respiratory system among smelter workers but not among workers in a lead-acid battery factory. As 60% of the members of the smelter workers cohort were hired after 1950, further follow-up of this cohort is warranted, in order to determine more reliably if there is an excess risk. In the third study, a slight but not significant increase of skin cancer was observed among workers exposed to tetraethyllead.

Several case-control studies have investigated the possibility that there is a causal link between paternal occupation and childhood cancer. The one study that specifically links lead-related occupations with the occurrence of Wilms' tumour cannot be considered to exhibit a causal link in view of the disputable appropriateness of the occupation subcategories used.

In nine studies, chromosomal aberrations were found in peripheral lymphocytes of lead-exposed populations whose blood lead levels ranged from 100-1000 mg/l. Negative results were obtained in six studies in which blood lead levels ranged from 40-500 mg/l.

In numerous reports, lead has been shown readily to cross the placenta. Good correlations have been reported between maternal and fetal blood levels. Adverse effects of lead on human reproduction, embryonic and fetal development and postnatal (e.g., mental) development have been reported.

5.3 Evaluation

Experimental and epidemiological data on metallic lead and organic lead compounds were either unavailable or inadequate, and no evaluation of their carcinogenicity was possible.

There is sufficient evidence that lead subacetate is carcinogenic to mice and rats and that lead acetate and lead phosphate are carcinogenic to rats. In the absence of adequate human data, it is reasonable, for practical purposes, to regard these compounds as if they presented a carcinogenic risk to humans.

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluations: Vol. 1 (1972); Vol 2 (1973) (Tetraethyl- and tetramethyllead) (Arsenic and arsenic compounds); Vol. 12 (1976)

Subsequent evaluation: Suppl. 7 (1987)


Last updated: 7 April 1998






















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