A set of neurobehavioural tests selected on the basis of information processing theory was used to study the effect of low level occupational lead exposure on 59 lead workers compared with a matched control group of the same number. Only one of the lead exposed group had a blood lead concentration above the current threshold limit value of 3 81 umol/l at the time of testing (mean 2-36jmol/l, range 1 19-3-92pmol/1) and none had been detected above that level in the previous three years. Nevertheless

Mercury is a known neurotoxin. Evidence from animal studies show behavioural impairment which can be long-lasting, after low-level exposure to mercury. Human research, however, has not been conclusive. Chronic, high-level mercury exposure such as occurred in Japan, and the Middle East, Causes long-lasting and profound neurological damage. However the effects of low-level exposure, such as occurs in occupational exposure, are far from clear. This study used a comprehensive test battery based on an information processing framework to compare a group of twelve chronically mercury-exposed workers with a matched control group. The mercury-exposed group showed poorer psychomotor co-ordination and premature fatigue, although simple motor responses were not affected. General arousal levels also remained unaffected but mercury-exposed workers were superior in sustaining attention. In spite of this, the mercury-exposed group showed clear deficits in short-term memory.