Diet and lead toxicity.

Introduction There is no known biological function for lead and any lead absorbed by man or by animal may be classified as potentially toxic. These toxic effects are many, ranging from morphological damage to tissues at higher concentrations, to lesser biochemical effects at lower concentrations. In biochemical systems lead will generally inhibit enzyme activity and result in clinical effects such as the development of anaemia, which is mediated in part through inhibition of haem biosynthesis. Pb has been associated with mental retardation in children and with hypertension and renal effects in adults (Moore, 1977). The potentially most hazardous effects to man are upon the central and peripheral nervous systems where the malign effects of Pb are seldom reversible. The sources of Pb are many, but the principal absorptive routes are from the diet, from water that is drwk and used in cooking and from the air that we breathe. There may also be secondary and limited absorption by the percutaneous route (Fig. I). Following absorption, Pb is bound principally in bone (greater than 90%). This Pb is fortunately not readily bio-available. The principal source of Pb exposure is through the diet and therefore any component of the diet that will alter the absorption of Pb, or following absorption, alter the distriiution of Pb within the body, (such as by redistribution from the bone) or which influences the normal rate of excretion of Pb, is potentially hazardous.