The long-term consequences of exposure to lead.

More than 90% of body lead is stored in bone. The technique of K-X-Ray fluorescence developed in the 1990s has enabled the quantitative measurement of decades of cumulative lead in bone, whereas blood lead levels reflect only recent exposure to lead. Bone lead is mobilized into the blood like bone calcium, as in osteoporosis, and exposes the patient to increased lead load. Many studies have assessed the toxic effect of chronic exposure from childhood to old age in present or former workers in industrial lead, as well as in non-occupational citizens in whom social and environmental circumstances might have induced higher exposure levels. This review points to the effects of elevated levels of bone lead and the associated cognitive decline among the elderly, with lead toxicity being one of the possible causes of degenerative dementia. There is evidence of an association between increased bone lead levels and renal disease, degenerative diseases like cataract, and suggestive but not causal association with blood pressure and hypertension. Community surveys show increased mortality associated with exposure to lead. Removal of sources of lead exposure, for example the use of non-leaded petrol, has reduced lead levels in the population, and there are currently strong recommendations to further lower the present allowed blood lead level to minimize chronic cumulative lead toxicity.