The serious effects of ambient air pollution on human health have been consistently documented by many studies on epidemiology worldwide, and it has been calculated that globally at least seven million deaths are attributable annually to the effects of air pollution. The major air pollutants emitted into the atmosphere by a number of natural processes and human activities include nitrogen oxides, volatile organic compounds, and particulate matter. Along with the poor ambient air quality, there is increase in evidence that indoor air pollution also poses a serious threat to human health, especially in low-income countries that still use biomass fuels as an energy resource. This review summarizes the current knowledge on ambient air pollution in financially deprived populations.