A recent study in Environmental Research Letters (ERL) reports how indoor air pollution from cooking on open fires varies by season in Pakistan. Although indoor air quality appears to improve during the summer thanks to the stoves being moved out of doors, this improvement is accompanied by an increase in the background level of PM10 particulate matter in the village.

Mankind has burnt biological and fossil fuels to produce heat for a long time. The walls of caves lived in millennia ago are covered with layers of soot, and many of the lungs of mummified bodies from Palaeolithic times have a black tone. Unfortunately, however, the problem is still on-going because such indoor air pollution exists even today in many developing countries around the world.

Indoor air pollution ranks among the three biggest killers worldwide, after tuberculosis and HIV/AIDS. The recent WHO global burden of disease report estimates the number of deaths from indoor air pollution from cooking to be around four million globally, which is twice previous estimates. The problem disproportionately affects women and young children. Indeed, children under five account for more than half of the deaths caused by indoor solid-fuel use.

Approximately three billion people rely on biomass energy – wood, charcoal, crop residues and dung – for cooking and heating their homes. These fuels tend to be burnt on open fires or low-efficiency stoves that are inadequately ventilated. This creates partial fuel combustion and the production of a raft of toxic pollutants. As a result, 3.5 million deaths are associated directly with indoor pollution each year; in Asia and sub-Saharan Africa, another 500,000 deaths are caused by outdoor air pollution from cooking.

In rural areas that depend on biomass, cooking stoves are moved out of doors in summer. This appears to improve indoor air quality but is accompanied by an increase in the background levels of PM10. Even in locations where natural gas is used, particulate levels decrease during the summer thanks to better ventilation.

During the current investigation, we looked at how PM levels vary from kitchen to kitchen and, in particular, how indoor PM levels significantly decrease during the summer in both rural and urban areas. The results show that, the type of stove employed and how well ventilated a kitchen is, are important for indoor air-pollution levels.

During our study, we also observed how households themselves attempt to reduce their exposure to smoke from cooking – for example, by using different stove layouts or including windows and doors in their kitchens. We conclude that education and socio-economic factors are therefore non-negligible when it comes to community-based interventions. Such interventions would be more widely accepted in a local community because they would take into account how rich or educated a household was, as well as any religious or cultural constraints.

Unlike many other developing nations, relatively few interventions have occurred in Pakistan. Worldwide, the Global Alliance for Clean Cookstoves is promoting the adoption of clean cooking stoves and fuels by 100 million households by 2020.

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