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Description of key information

Inorganic lead compounds do not exhibit toxicity in acute toxicity tests with experimental animals.

Key value for chemical safety assessment

Additional information

For LEAD: All available studies indicate a very low acute oral toxicity of seven inorganic lead compounds similar in physical and chemical properties to basic lead sulphate. There was also no evidence of any local or systemic toxicity associated with the oral administration of any of these compounds. Whether or not the compound contained the anion of an inorganic acid or an organic acid had no effect upon toxicity, and literature searches found no indications that anions present in high production volume compounds not tested would impart properties of toxicity different from those that have been tested. Based upon these overall observations, read across from these lead compounds permits the conclusion to be drawn that basic lead sulphate will not be acutely toxic via oral exposure routes.

Acute toxicity was not observed in animals after inhalation or dermal exposures up to the limit values of acute toxicity testing for a smaller number of compounds. Inhalation studies were restricted to lead oxide, a material found to have a particle size distribution that would approximate that of basic lead sulphate. Pulmonary deposition modelling further indicated that lead oxide provided a good surrogate for other lead compounds in that similar pulmonary deposition patterns, and corresponding local and systemic exposures, would be similar to those of other compounds. Read across from lead oxide inhalation data to other compounds was thus scientifically justified and in the interests of animal welfare. Similarly, a group of three compounds (lead oxide, lead phthalate and dibasic lead phosphite) were tested for dermal toxicity and irritation endpoints. The three compounds selected spanned the range of chemistries (organic and inorganic anions) and solubilities found for a number of other lead compounds. Data demonstrating lack of toxicity and irritant properties were generated to provide a basis for read across to basic lead sulphate that is similarly scientifically justified and in the interests of animal welfare. The uniformly negative acute toxicity profile is mirrored by observations in humans where toxicity in humans after true acute exposures is very limited. When human toxicity is observed it is generally under conditions that yield sub-chronic or chronic exposures. This finding is not unexpected given the pharmacokinetics of lead uptake into the body. Lead uptake is generally quite low and heavily reliant upon easily saturable active transport mechanisms. Once saturation of these uptake mechanisms has occurred, uptake proceeds by inefficient passive diffusion. The uptake of lead is thus highly non-linear as a function of dose with uptake efficiency declining with the amount of lead administered to a test animal or an exposed human. Although toxic under chronic exposure situations, the acute toxicity of inorganic lead metal compounds appears to be quite low via all exposure routes.

Justification for classification or non-classification

The current classification of lead compounds not otherwise described in Annex I is:

Xn; R20/22 (harmful by inhalation and if swallowed)

and under CLP:

Acute Tox. 4 *                       (H332)

Acute Tox. 4 *                       (H302)

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