MIGRATION OF LEAD FROM POLYMERS IN RAT GASTRO-INTESTINAL TRACT

The migration of lead from four polymer formulations during their passage through the rat gastro-intestinal tract has been investigated. Diets containing 1% of the formulations have been administered to groups of rats for 4-5 months and measurements have been made of the lead content in blood, bile and urine, and in liver, kidneys and bone. As a reference, similar analyses have been made on groups of rats receiving diets containing 2, 6 or 20 ppm lead as lead nitrate. Lead is poorly absorbed from rat intestine; with the diet containing 20 ppm lead it is not possible to detect a significant increase of lead in blood, urine or liver. A significant rise has been observed in kidney and bone, however, and bile is probably the best index of lead absorption. The greatest migration of lead into the gut from the polymer formulations was observed with PVC containing 2.3% lead sulphate, where the amount was equivalent to about 3 mg lead/g polymer. A more realistic assessment of the ingestion risk is obtained from the amount of lead migrating per unit surface area of polymer under these conditions; with the PVC formulation this was in the region of 25 μg/cm2. The surface area of this formulation ingested daily would have to exceed 40 cm2 before the daily addition of lead to the diet would exceed 1 mg, and this area would be much larger in the case of the other polymers. It is concluded that the risk of lead poisoning from ingestion of any of the four polymers is negligible. © 1968.