Subjective symptoms after long term lead exposure in secondary lead smelting workers.

The prevalence of lead induced subjective symptoms was evaluated by a standardised questionnaire in a group of 96 workers employed between nine and 45 years in a secondary lead smelting works. A control group of 96 non-lead exposed subjects, matched for age and sex, were chosen from the Glostrup population study. Blood lead concentrations were in excess of 60 micrograms/100 ml in about 30% of the lead workers. Zinc protoporphyrin levels were found to be higher than 500 mumol/Hb in nearly 18% of the lead workers. The prevalence of fatigue, headache, sleep disturbance, and digestive symptoms (constipation and colic) were not higher in the lead exposed group. The body weight showed no significant difference in the two groups. Nervousness was four times more frequent in the control group. The results indicate that subjective symptoms are useless as indicators of incipient lead poisoning.