a local context are called upon by government and civil society alike, for example, when air pollution is suddenly visible in the atmosphere or smelt in the air. A case of the latter occurred recently when the putrid smell of hydrogen sulphide permeated the air in parts of Gauteng and Mpumalanga, South Africa (eNCA 2021). These occurrences highlight the importance of hard evidence and data to understand, explain and call for action, and interventions to prevent air pollution and its harmful health impacts.Until recently, air pollution data were primarily available from two sources: ground-based monitoring stations and satellites. Both have their strengths and limitations. Groundbased stations (183 officially listed stations in South Africa) are generally sparse and situated in ambient/ outdoor settings and do not capture HAP exposure. They typically monitor a variety of criteria / regulated pollutants (i.e., PM 10 , PM 2.5 , SO 2 , NO 2 , O 3 , CO) in air pollution hot spots. Satellite air quality data cover a broader geographic area but do not necessarily measure the air people breathe on the ground. The integration of satellite data with atmospheric and/or statistical models along with surface monitored data is necessary to gain a more holistic understanding of air pollution exposure (van Donkelaar et al., 2016).

Poor air quality inside vehicles and its impact on human health is an issue requiring attention, with drivers and passengers facing levels of air pollution potentially greater than streetside outdoor air. This paper assesses the potential effectiveness of a car cabin filtration system to remove fine particulate matter PM 2.5 and improve air quality for car passengers. The study was conducted as a practical evaluation coupled to a model implementation. First, the effectiveness of PM 2.5 filter material was investigated in a chamber experiment under a range of environmental and loading conditions using a realistic automotive auxiliary scrubber. Second, implementation of such a system was evaluated in a full air flow 3D computational fluid dynamical model configured for a realistic cabin and ventilation system, and related to the chamber results through a simple decay model. Additionally, performance of low-cost dust sensors was evaluated as potential cabin monitoring devices. The experiment and modeling support the feasibility of a robust system which could be integrated into automotive designs in a straightforward manner. Results suggest that an auxiliary scrubber in the rear of the cabin alone would provide suboptimal performance, but that by incorporating a PM 2.5 filter into the main air handling system, cabin PM 2.5 concentrations could be reduced from 100 mg m À3 to less than 25 mg m À3 in 100 s and to 5 mg m À3 in 250 s. A health impact assessment for hypothetical occupational driver populations using such technology long term showed considerable reductions in indicative PM 2.5 attributable mortality.

Background: Household air pollution (HAP) is associated with adverse human health impacts. During COVID-19 Lockdown Levels 5 and 4 (the most stringent levels), South Africans remained at home, potentially increasing their exposure to HAP. Objectives:To investigate changes in fuel use behaviours/patterns of use affecting HAP exposure and associated HAP-related respiratory health outcomes during COVID-19 Lockdown Levels 5 and 4.Methods: This was a cross-sectional online and telephonic survey of participants from an existing database. Logistic regression and McNemar's test were used to analyse household-level data.Results: Among 2 505 participants, while electricity was the main energy source for cooking and heating the month before and during Lockdown Levels 5 and 4, some households used less electricity during Lockdown Levels 5 and 4 or switched to "dirty fuels." One third of participants reported presence of environmental tobacco smoke in the home, a source of HAP associated with respiratory illnesses. Prevalence of HAP-related respiratory health outcomes were <10% (except dry cough). Majority of households reported cooking more, cleaning more and spending more time indoors during Lockdown Levels 5 and 4 -potentially exposed to HAP. Conclusion:Should South Africa return to Lockdown Levels 5 or 4, awareness raising about the risks associated with HAP as well as messaging information for prevention of exposure to HAP, including environmental tobacco smoke, and associated adverse health impacts will be necessary.

Sub-Saharan Africa is seeing rapid urbanization, with the population of cities such as Lagos and Nairobi growing at a rate of 3–4% a year. The region is extremely under-sampled for all air pollutants, particularly VOCs, which are useful markers for source apportionment as well as toxic in their own right. There are many contributors to air pollution in the region, and studies examining fine particulate pollution implicate traffic as the primary source in urban areas. In this pilot study, VOCs were analysed at a selection of roadside and urban background locations in Nairobi and Lagos, and 74 VOCs were quantified. GC×GC–MS/FID analysis revealed all locations were dominated by hydrocarbons typical of vehicle emissions, with the aromatic hydrocarbons benzene and toluene among the most abundant VOCs. Typical personal exposure scenarios for citizens of the cities were calculated to far exceed those of a resident in a city in Europe/US. Finally, the calculated ozone forming potential of the VOCs measured was found to be similarly high to other large cities studied with similar air pollution problems. Further study is therefore essential to determine the full extent of VOC pollution in the region and its impact on tropospheric chemistry.

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