Lead Content of Lichens in Metropolitan Harare, Zimbabwe. Air Quality and Health Risk Implications

Abstract

Many studies have shown that inhaled lead is one of the major contributors of lead poisoning. Lead poisoning affects all systems within the body. Lead amount in metropolitan Harare atmosphere was estimated by measuring the amount of lead in lichens found in the area. Lead pollution of the atmosphere is of major concern because continuous exposure of low levels of lead may cause serious effects. Furthermore there are no agreed safety limits for children. The concentration of Pb in different species was determined by atomic absorption spectrometry. Lead concentration varied from not detectable quantities to 3.31 0.04 ppm. Harare central hospital recorded the highest lead content 3.31 0.04 ppm in Parmelia species while the lowest was observed at centers far from the CBD, Botanic gardens, Christonbank and Mwenje dam. Generally the relationship between distance, lead content and species diversity was significant for most lichens except that for Lecanora caesiopallens (r = 0.72) and Lecanora atraaeformis (r = 0.71) student t-test p > 0,05 showing presence of increased pollution in the CBD. It is suggested that all possible sources of lead poisoning and their contributions to atmospheric lead content should be ascertained to determine the actual daily exposure rate. Such data would help in formulating policies to reduce lead poisoning in the general public.