Monitoring of airborne particulate matter (APM), background radiation, analysis of trace metals and other parameters in some parts of Kenya

Abstract

This project undertook various studies monitoring workplace environments and assessing some occupational health status. The studies included monitoring levels of airborne particulate matter (APM), natural background radiation, emissions inventory, analysis of trace elements and other parameters in samples collected from various parts of Kenya. The research team published various articles in both local and international refereed journals and participated in various scientific conferences. Monitoring of outdoor APM levels in Kibera, a residential urban area in Nairobi with a population density of 40,881 people per km2, had levels varying from 77.6–159.1 μg/m3 for samples collected at a height of two (2) metres and 60.9–138 μg/m3 for samples collected at four (4) metres above the ground. For the samples collected at the two (2) metres height, 66% exceeded the WHO 24 hour guideline of 70 μg/m3 while at four (4) metres height, only 50% of the samples exceeded this limit. These values are higher than our previous data (30–80 μg/m3) reported for a sub-urban site in Nairobi. In addition, the regression analysis of the mean monthly incidences of acute respiratory infections (ARI) of children in Kibera and the coarse APM (PM10) and fine (PM2) levels showed no significant correlation. This is despite the high rate of ARI incidences observed in this area. Simulation of the emissions inventory for 1992 found that cement production constituted 96% of the total non-energy source of industrial CO2 and that lime was mainly used for cement production in Kenya. The pulp and paper industry contributed 89% of total SO2 emissions while sugar production contributed 55% of all the total no-metallic volatile organic compounds (NMVOC). Assessment of ozone, nitrogen oxides and trace elements levels present in ambient Nairobi air was also done. The findings of our study showed that levels for Pb, Mn, Fe, Br, Zn, Cu and Ca are within the WHO guidelines. Pb ranged from 0.051 to 1.106 μg/m3; Fe, 0.149 to 3.154 μg/m3; Mn, 0.002 to 0.526 μg/m3; Cu, lower limit of detection (LLD) to 0.15 μg/m3; Br, LLD to 0.43 μg/m3; Zn, LLD to 0.14 μg/m3 and Ca, 2.18 to 5.389 μg/m3. Concentrations of NO2, NO and O3 were also within the 8-hour WHO limits with levels ranging from 0.011–0.976 ppm for NO, 0.001–0.2628 ppm for NO2 and LLD-0.1258 ppm for ozone. The O3 levels were slightly higher in the afternoons when solar intensity was high especially during the days when cloud cover was less than 3 Oktas. PM10 levels were, however, above the WHO guidelines for most of the days. The mean PM10 level was (239±126) μg/m3 while the range was 66.7–444.5 μg/m3.