Abstract
The zinc protoporphyrin/haemoglobin (ZPP/Hb) ratio was measured in the field with a haematofluorometer. A significant increase in ZPP/Hb ratio with advancing age was found in 1295 men who denied any excess exposure to lead. Ninety-seven per cent of the results were below 110 mumol ZPP/mol Hb(Fe) (4.4 microgram ZPP/g Hb). The ZPP/Hb ratio was determined in a lead-exposed population of 2275 men, and in 305 a blood lead analysis was also performed. A blood lead limit of 2.9 mumol/l (60 microgram/100 ml) corresponds to about 500 mumol ZPP/mol Hb(Fe) (20 microgram/g). This limit was exceeded in workers engaged in secondary lead smelting, storage battery manufacture, car radiator repair, crystal glass manufacture, storage battery repair, ship breaking, metal foundries, the ceramic industry, scrap metal handling, and PVC plastic manufacture. Other occupations caused lower lead exposures with ZPP/Hb ratios between 110 and 500 mumol ZPP/mol Hb(Fe): such ratios were found in men from shooting ranges, in leaded pane manufacturers, gunsmiths, car paint sprayers, type setters, steel rolling mill workers, shipbuilders and welders, car mechanics, lead pigment handlers, and solderers. Increased ZPP/Hb ratios and blood lead levels in 210 workers were associated with a decrease in haemoglobin concentration in the blood. Thus, the haematofluorometer has proved to be very useful for screening purposes. A blood lead determination should be performed if the ZPP/Hb ratio exceeds 300 microgram ZPP/mol Hb(Fe) (12 microgram/g).