The immune system as target for subclinical lead related toxicity.

During the past two decades, scientific interest and public health concern have shifted their focus from issues connected with overt clinical lead disease to the detection of subtle clinical and biochemical abberations.' This has brought about a change in the thinking on the health risks that are associated with lead toxicity.23 Although major emphasis has been set on lead hazards among pediatric populations, there has also been a gradual lowering of the occupational biological standards in many countries. The several investigations that have shown an association between low level, community related exposure to lead and impairment in child development have provided a strong scientific basis for the decision of the Centers for Disease Control in the United States to define lead toxicity at a blood lead concentration of 10 mcg/dl.' By analogy, reports that neurotoxic effects and abnormalities in the male reproductive system of workers exposed to lead can be detected at blood lead concentrations below that at which removal from exposure is usually mandated, begin to question the safety of blood lead standards that are widely accepted as safe.7' A deja vu from the 1970s, but this time it concerns even lower blood lead concentrations!P' As the scientific spectrum ofeffects induced by lead has been widened, toxic effects of lead have also been detected in organ systems that historically were not part of the clinical features of lead poisoning. Mechanisms of action of characteristic effects are being studied in greater detail as well." Although many biochemical and molecular perturbations caused by lead have been studied in experimental