Air pollution in Nairobi slums : sources, levels and lay perceptions

Abstract: BackgroundAir quality in Africa has remained a relatively under-researched field. Most of the African population is dependent on biomass for cooking and heating, with most of the combustion happening in low efficiency stoves in unvented kitchens. The resulting high emissions are compounded by ingress from poor outdoor air in a context of poor emissions controls. The situation is dire in slum households where homes are crowded and space is limited, pushing households to cook in the same room that is used for sleeping. This study assessed the levels of particulate matter with aerodynamic diameter £ 2.5 microns (PM2.5) in slum households and people's perceptions of and attitudes towards air pollution and health risks of exposure in two slum areas, Viwandani and Korogocho, in the Nairobi city.Methods The study employed both qualitative and quantitative methods. For the quantitative study, we used structured questionnaires to collect data about the source of air pollution among adults aged 18 years and above and pregnant women residing in the two study communities. We used the DustTrak™ air samplers to monitor the indoor PM2.5 levels in selected households. We also collected data on community perceptions on air pollution, annoyance and associated health risks. We presented hotspot maps to portray the spatial distribution of perceptions on air pollution in the study areas. For the qualitative study, we conducted focus group discussions with adult community members. Groups were disaggregated by age to account for different languages used to communicate with the younger and older people. We analysed the qualitative data using thematic analysis.Results Household levels of PM2.5 varied widely across households and ranged from 1 to 12,369μg/m3 (SD=287.11). The household levels of PM2.5 levels were likely to exceed the WHO guidelines given the high levels observed in less than 24 hours of monitoring periods (on average 10.4 hours in Viwandani and 11.8 hours in Korogocho). Most of the respondents did not use ventilation use in the evening which coincided with the use of cookstove and lamp, mostly burning kerosene. The levels of PM2.5 varied by the type of fuels, with the highest emissions in households using kerosene for cooking and lighting. The PM2.5 levels spiked in the evenings and during periods of cooking using charcoal/wood. Despite these high levels, residents perceived indoor air to be less polluted compared with the outdoor air, possibly due to the presence of large sources of emissions near the communities such as dumpsites and industries. The community had mixed perceptions on the health impacts of air pollution, with respiratory illnesses perceived as the main consequence while vector or sanitation related diseases such as diarrhoea was also perceived to be related to air pollution.ConclusionsWith poor housing and reliance on dirty fuels, households in slums face potentially high levels of exposure to PM2.5 with dire implications on health. To address the poor perception on air pollution and knowledge gaps on the health effects of air pollution, education programs need to be developed and tailored. These programs should aim to provide residents with information on air quality and its impact on the health; what they can do as communities as well as empower them to reach out to government/stakeholders for action on outdoor sources of pollution such as emissions from dumpsites or industries. The government has a larger role in addressing some of the key pollution sources through policy formulation and strong implementation/enforcement.