Monitoring the levels of toxic air pollutants in the ambient air of Freetown, Sierra Leone

摘要

The ambient air quality in Freetown, Sierra Leone was investigated for the first time for toxic air pollutants. We investigated the levels of polycyclic aromatic hydrocarbons (PAHs), suspended particulate matter (SPM) and carbon monoxide (CO) and considered the implication of air quality and health risks. Particulate samples for PM2.5and PM2.5 to10fractions were collected from four sites, and analyzed by HPLC/FLD. SPM and CO were monitored by realtime monitors. The annual average concentrations of total PAHs for PM2.5and PM2.5 to10fractions for the various sites were found to be 37.18 and 6.24 ng/m3. The average concentration of SPM was 216.3 count per min (cpm) and the 8-h average concentration of CO was 10 ppm. Higher concentrations of PM2.5and PM2.5 to 10PAHs were found in dry season compared with wet season. The annual carcinogenic potential of PAHs was high in PM2.5fraction while the levels of SPM and CO were high enough to raise concern of health risks. The ambient air quality in Freetown was judged to be poor and in view of human exposure, large portion of urban residents are exposed to high levels of toxic air pollutants which is recognized to be a public health risk.