Periodic Reporting for period 1 - SO-TOX (SOURCE AND TOXICOLOGICAL PROFILE OF AIRBORNE PARTICLES IN AFRICAN MEGACITY)
Reporting period: 2024-02-14 to 2026-02-13
African countries are home to some of the world’s most polluted cities, where bad air quality is the most potent risk factor for mortality. However, they are nearly unrepresented in the research on air pollution levels and health impacts. Without adequate knowledge of air quality and mitigating the sources of pollution, the problem will only get worse given Africa’s expected population boom. Particulate matter (PM) is classified as the most dangerous form of air pollution. The SO-TOX project aims to contribute to a better understanding of PM levels in the megacity of Luanda, their sources and effects, and to help authorities implement measures. The project has a strong connection with a recent World Health Assembly resolution, which has set actions to address air pollution and its health risks in Africa as a priority.
Based on a monitoring campaign funded by another project (APAM), which took place in Luanda from June to November 2023, samples of inhalable particulate matter with diameter lower than 10 micrometres (PM10) were subjected to gravimetric quantification and determination of its carbonaceous content by a thermo-optical technique. Daily PM10 concentrations ranged from 20.6 to 108 µg/m3, averaging 59.2 µg/m3. The guideline of 45 µg/m3 recommended by the WHO was exceeded on 70% of days. On average, carbonaceous constituents (organic and elemental carbon, OC and EC, respectively) accounted for 21.6% of the PM10 mass. An OC/EC ratio of 1.13±0.58 was obtained, indicating that traffic is the main emission source.
The high levels of PM10 observed indicate that the population of Luanda is at risk and that the adoption of air quality improvement plans must be adopted by the authorities. The Angolan Ministry of the Environment must create air quality legislation in line with WHO guidelines and invest in long-term monitoring. The mass fractions of OC and EC obtained suggest that a substantial part of PM10 is inorganic and may originate from mineral dust resulting from soil resuspension, non-exhaust emissions, such as tyre and brake wear, among other sources. The OC/EC ratio close to 1 indicates that traffic is the main source of carbonaceous material. However, to quantify the contribution of the various sources it is necessary to use other analytical techniques to the PM10 samples to obtain the detailed chemical composition and apply a source apportionment model, such as positive matrix factorisation. The application of cytotoxicity tests and the determination of the oxidative potential of samples in the near future will help to obtain scientific evidence on the harmful health effects of PM10 to convince authorities of the need to take action.