Lead silicate toxicity: a comparison among different compounds.

The aim of this report is to point out the relative toxicity of different commercial products containing lead silicates by studying their in vitro solubility and rate of absorption via the respiratory and digestive systems, compared with those of red lead (lead tetroxide). In vitro solubility was tested, by a modified Brimsdown method, with bidistilled water, saline, blood serum, pleural fluid, and dilute hydrochloric and acetic acids as solvents. Experimental animals were administered 25 mg equivalent mean doses using an intragastric tube or endotracheal intubation. Results showed that in vitro solubility gradually increases from distilled water, through saline and biological fluids, to acidic media. Lead absorption via the respiratory system is rapid and persistent, with small differences among the tested compounds. Less information can be gained from intragastric experiments. No correlation was found between in vitro solubility and in vivo absorption. On the other hand, in vitro studies must be strictly standardized. The relative absorption of the different materials, compared with red lead showed that all of them have to be regarded as equally toxic.