Particulate Matter Air Pollution in Mali - A litterature review and basic health risk assessment

Particulate matter (PM) is a mixture of solid and liquid particles in the air (aerosols). The chemical composition varies depending on the origin of the particles. Particle size is crucial for respiratory tract deposition, and thus indirectly to the toxicological response. Up to 90% of the smallest combustion particles are absorbed in the respiratory tract. Most of them can pass thru the alveoli, which can result in systemic effects. As of today, there is no indication of a safe exposure level or a threshold below which no adverse health effects occur. Currently, at population level, there is insufficient evidence to identify specific health effects of particles in relation to chemical composition. However, combustion-related PM (from both mobile and stationary sources) is more consistently linked to health effects than PM from other sources. The main causes of mortality due to PM exposure in Africa are natural sources, such as desert dust and biomass combustion, although assessments of chronic health effects and mortality associated with exposure to dust is more uncertain than the corresponding assessments from typical air pollution in industrialized countries, However, several studies suggest that dust, similar to combustion-related particles, can have a physical impact on the respiratory tract mucous membranes, trigger oxidative stress, damage DNA, and cause lung function impairment. Internationally, Mali scores low with respect to air quality, due to high levels of fine particles (PM2.5) and substandard indoor air. In rural areas, ambient air is mostly influenced by naturally high levels of particles (e.g. sand storms, grass fires) and emissions from traditional fuels such as fuel wood and charcoal. The air quality in the capital Bamako is primarily impacted by fuel emissions from two-stroke vehicles, and by household and industrial waste combustions as well as the population's domestic energy supply. Seasonally airborne sand is also present in the air. The purpose of this report is to provide a brief background to the occurrence and health risks associated with particulate matter and to compile existing studies in Mali, focusing on PM levels, composition, toxicity, and epidemiology. Furthermore, the purpose is also to perform a simple health risk assessment with suggestions for health monitoring of Swedish Armed Forces personnel deployed in Mali. Studies on air quality in Mali show large variations due to spatial (location, altitude, weather conditions), and temporal (day by day, month) factors, but also due to the methods the studies are based on. Existing data are not sufficient to determine how PM varies on a daily and annual basis at Camp Nobel and Camp Midgård. One conclusion is however that the lowest baseline levels, for Bamako in particular, appear to be high in relation to known levels of acute effects (as well as chronic). The possibility to monitor daily and annual variations of PM10 and PM2.5 at Camp Nobel and Camp Midgård would provide information about the average exposure for deployed personnel, and thus facilitate risk mitigation measures for the Swedish Armed force's personnel.