Assessment of particulate matter exposure on ambient air and its impact on workers at two granite quarry mines at Njuli, Southern Malawi.

Abstract

Quarrying activities are among the significant sources of pollution caused by particulate matter (PM) in ambient air. Besides affecting the environment, PM exposure is one of the leading causes of respiratory illnesses worldwide. The current study, unique to Malawi, aimed to understand the impact of particulate matter on ambient air and the possible effects on workers' health at Njuli in Blantyre and Chiradzulu districts. The study measured concentrations of particulate matter in ambient air, conducted a chemical analysis of fallen dust, and surveyed respiratory symptoms. Results showed higher exposures to particulate matter at a Terrastone mine (126µg/m3 highest exposure) than a Mota Engil mine (83µg/m3 highest exposure), attributed to poor management practices at Terrastone mine. Higher PM readings (0-85.98µg/m3) were observed for sites located downwind of the mines than sites located upwind (0-59µg/m3), demonstrating the impact of quarrying operations at the mines; differences were, however, not statistically significant (P 0.165, Terrastone, P 0.678 Mota Engil). The observed amount of PM in ambient air was consistent with the scale of quarrying and processing operations at both mines, 0-56.2µg/m3 in pre-operational phases, 0-126.1µg/m3 during operations, and 0-56µg/m3 after closure of operations; differences were statistically significant only at Terrastone mine P 0.003. The impact of season variation was observed following lower PM readings recorded during the rainy season than those obtained during the dry season at both mines. Analysis of health symptoms revealed that a higher proportion of workers at the Terrastone mine experienced respiratory symptoms compared to the Mota Engil mine.