Soil Concentration of Selected Heavy Metals in Chuka, Nakuru and Thika Municipal Dumpsites

Abstract

Dumpsite waste pickers face numerous health and safety risk factors one of which is elevated concentration of heavy metals in the soil that could be a source of exposure through dusts. The purpose of this study was to determine the concentration of selected heavy metals (lead, cadmium, chromium and copper) in the top 15 cm of soil in the largest dumpsites in Tharaka Nithi, Nakuru and Kiambu counties namely; Chuka, Nakuru and Thika towns, respectively. The study was non-experimental cross-sectional ecological survey, the sampling design a herringbone pattern with 96 soil samples collected with a stainless-steel auger. Laboratory analysis was done by USEPA Method 3050B and the concentration determined by Atomic Absorption Spectrophotometer at the Department of Mines and Geology Laboratory in Nairobi. F-test was done for differences between dumpsites at α=.05 and comparison made to WHO guidance values. Significant differences between the dumpsites were detected for lead (F=44.555, p=<.001), copper (F=5.897, p=<.01), cadmium (F=4.739, p=.016) and chromium (F=6.223, p=<.01). The largest percentage of samples with concentrations above the WHO guidelines were Kiambu (97%) for lead and Nakuru with 26.7% for chromium, 66.7% for cadmium and 56.7% for copper.  Chuka dumpsite had the highest proportion of samples with the lowest concentration of lead and chromium and with the lowest proportion of samples where cadmium was detected. In conclusion, Nakuru and Kiambu dumpsite were highly polluted and were a huge risk factor to the waste pickers. In the short-term, it was recommended that waste pickers should wear adequate health and safety protective equipment while on site and possibly reduce the time at the dumpsite to minimise exposure. In the long-term, waste separation should be done to ensure that heavy metal containing waste do not get to the dumpsites, waste recovery facilities adopted to minimise waste picking at dumpsites and improve recycling, and the dumpsites upgraded to sanitary landfill status.