Exposure profiles of kitchen occupants showed that fuel, kitchen volume, cooking type and ventilation were the most prominent factors affecting in-kitchen exposure. The study found that different cuisines resulted in varying cooking durations and therefore, disproportional exposures. Occupants in Dhaka, Nanjing, Dar-es-Salaam and Nairobi spent > 40% of their cooking time frying, which is the highest particle emitting cooking activity, compared with ∼ 68% of time spent boiling or stewing in Cairo, Sulaymaniyah and Akure.
The highest average PM2.5 (PM10) concentrations were in Dhaka 185 ± 48 (220 ± 58) μg m−3 owing to small kitchens, extensive frying and prolonged cooking compared with the lowest in Medellín 10 ± 3 (14 ± 2) μg m−3. Having dual ventilation, both mechanical and natural in Chennai, Cairo and Sulaymaniyah reduced average in-kitchen PM2.5 and PM10 by 2.3- and 1.8-times compared with natural ventilation in the form of open doors in Addis Ababa, Dar-es-Salam and Nairobi. Using charcoal during cooking in Addis Ababa, Blantyre and Nairobi increased PM2.5 levels by 1.3- and 3.1-times compared with using natural gas in Nanjing, Medellín and Cairo, and LPG in Chennai, São Paulo and Sulaymaniyah, respectively. Smaller kitchens (<15 m3; Dhaka and Nanjing) increased cooking exposure compared with their larger counterparts (Medellin, Cairo and Sulaymaniyah).
Potential exposure doses were highest for Asian, followed by African, Middle-eastern and South American homes. The study recommends increased cooking exhaust extraction, cleaner fuels, awareness on improved cooking practices and minimising passive occupancy in kitchens to mitigate harmful cooking emissions.