Open waste burning leads to significantly high black carbon exposure amongst burners

Globally, about 14% of households have no option but to burn their waste.  Open waste burning is a significant source of black carbon (BC) emissions, yet the exposure of those engaged in this practice has not been interrogated. This study provides the first quantification of personal exposure to BC emissions from open waste burning, revealing critical insights into the potential health risks faced by individuals engaged in this practice. Between November–December 2023, we conducted a comprehensive field study in Blantyre, Malawi, monitoring BC exposure among 46 volunteers from 23 households over approximately 20 hours on the day waste was burned at their household. Within each household, one individual responsible for burning waste and one non-burner wore MicroAeth MA200 monitors to capture personal exposure data. To summarize exposure, the average BC concentration was calculated for each a) monitoring period, b) for burning times, and c) for non-burning times. The median of these averages was then used to characterize exposure levels. Results showed that waste burners experienced significantly higher BC exposure than non-burners during both burning periods and the overall monitoring period (Wilcoxon signed rank test, p = 0.04). During burning, the median BC exposure for burners was 12.8 μg/m³, over four times higher than the median exposure of non-burners at 2.9 μg/m³. The median BC exposure for burners during the 20-hour monitoring period was 5.1 μg/m³, compared to 3.0 μg/m³ for non-burners. Notably, BC exposure levels during non-burning periods were statistically indistinguishable between burners and non-burners (Wilcoxon signed rank test, p = 0.44), with median exposures of 3.6 μg/m³ and 2.6 μg/m³, respectively. This study highlights the extreme BC exposure faced by individuals actively burning waste, and underscores the health risks associated with this practice and the need for interventions to mitigate exposure.