Air pollution is a global public health concern. In the developing world, air pollution presents a particular threat to the health of millions of people in megacities that are growing in a fast, poorly planned, and unregulated manner. Air pollution research in the developing world will be illustrated with two studies: A pioneer air pollution assessment in Uganda and an indoor air intervention study in China. The pioneer air pollution assessment in Kampala/Uganda (east Africa) was conducted from 2014 to 2015. Concentrations and spatial variation of major criteria air pollutants (PM2.5, NO2, SO2, O3) were measured. The results indicate unhealthy ambient air in Kampala, and exposure to this air may increase the burden of environmentally induced diseases. The infrastructure for air quality management in Uganda needs to be established, and locally and culturally customized solutions for air quality management and exposure and risk reduction are needed. In China, ambient air quality has demonstrated significant deterioration in the past 20 years. The effectiveness of applying portable air cleaners to improve indoor air quality was tested as an effective way to reduce personal exposures to air pollutants in Chongqing, China. A portable air cleaner was applied in twenty homes, and simultaneous indoor and outdoor measurements was conducted for multiple air pollutants, including PM2.5, black carbon, NO2, O3, formaldehyde, OC and EC, temperature and humidity, and CO2. Indoor pollutants of outdoor origin were significantly (P-value < 0.05) reduced by the portable air cleaner. Given that people spend 80%-90% of their time indoors, one promising approach to reduce indoor air pollution exposure in high pollution areas is to use portable air cleaners. The obstacles and needs to successfully implement an air pollution study overseas will also be discussed.