Short-lived climate pollutants

Measurements of BC, PM2.5, and PM10 revealed that the average hourly BC levels from households in the six counties ranged between <1 μg/m³ and >100 μg/m³ (± 0.49 μg/m³ to >150 μg/m³ SD), while mean BC levels from vehicular emissions in Nairobi ranged between 34 μg/m³ and 55 μg/m³. Notably, on several occasions, these levels exceeded the national tolerance limits (industrial) of 35 μg/m³ (annual average) and 75 μg/m³ (24-hour average).

Furthermore, PM2.5 concentrations were significantly higher during peak periods in the morning and evening, ranging from 5 μg/m³ to >20 μg/m³, whereas PM10 levels ranged from 10 μg/m³ to >100 μg/m³. According to World Health Organization (WHO) air quality guidelines, most recorded average PM2.5 concentrations in developing cities are approximately 35 μg/m³; however, these should be reduced to the recommended WHO guideline levels of 25 μg/m³ (24-hour limit) and 10 μg/m³ (annual average).

Moreover, it is estimated that reducing elevated PM2.5 levels can minimize pollution-related health issues by up to 15%. In addition, regression model results for estimated pollution levels indicated statistical significance during certain periods of the day and year for BC, PM2.5, and PM10. Consequently, this has a considerable impact on populations at risk of exposure to pollution, particularly women, children, and other vulnerable groups.