Lead-poisoning in two distant states of Nigeria: an indication of the real size of the problem

Abstract

Lead is a toxic trace metal but useful in a number of industries and occupations. In view of its wide usage appropriate attention to precautionary measures against excessive exposure is desirable. The study was carried out in two phases; one based in Southwest Nigeria involving 137 subjects comprising 86 occupationally exposed subjects and 51 controls. Phase 2 of the study involved 880 occupationally unexposed subjects as follows: 115 subjects from Iseyin, 280 subjects from Shaki, 284 subject from Ogbomoso and 201 subjects from Sokoto, NorthWest Nigeria. Alcohol, salt and tobacco consumption were carefully monitored in this second phase of the study as well as sources of potable water. Lead (pb) was determined by atomic absorption spectrophotometry (AAS). In phase one in occupationally exposed individuals PbB was significantly higher than in controls (P<0.00.1); 95.3% of the test subjects had PbB greater than 40µg dl. The universal upper limit of acceptable PbB in Pb workers. About 70% had PbB greater than 55µg/dl, a level now considered indicative of excessive exposure. Additionally, about 40% of the Pb workers had PbB of 60 µg/dl and above, a level indicative of the need to remove affected individuals from further exposure. Only about 5% of the Pb workers had PbB below 40 µg/dl. Interestingly, in the control subjects only about 18% had blood Pb levels falling within commonly acceptable PbB levels, about 7% of controls (Occupationally unexposed) had PbB level within the range considered indicative of moderate toxicity, over 8% had PbB above levels acceptable in occupational exposure, while about 4% fell within the range indicative of severe toxicity. PbB for unexposed population therefore, also give cause for toxicity. Phase 2 study revealed that excessive use of alcohol and tobacco, undue exposure to exhaust from vehicles using leaded gasoline, exclusive use of wells as sources of drinking water and increased consumption of the Nigerian table salt may all be pathways for increased Pb burden in this environment. These data suggest Pb poisoning of a high magnitude arising from occupational and environmental factors probably largely due to high gasoline Pb. Precautionary measures appear desirable by all who are occupationally or environmentally exposed to Pb.