In the health economics literature, many studies have assessed the association between environmental degradation and health outcomes. This paper extends this literature by investigating how the presence of air pollution might explain health inequalities both between and within developing countries. We argue that differential exposure to air pollution between asset classes, differential ability to prevent the negative health effects of environment degradation, differential capacity to respond to disease caused by pollutants, and particular susceptibility of some groups to the effects of air pollution are all sufficient reasons for explaining a positive link between air pollution and asset-related health inequality. Using data from developing countries, our econometric results show that sulphur dioxide emissions (SO2) and particulate matter (PM10) partly explain the large disparities in infant and child mortalities between and within developing countries. In addition, we found that the institutions that are based on democratic principles, and which have low levels of corruption and high quality bureaucracy, are the most effective. That is, they are more responsive to the needs of the poor, they promote access to justice and public administration, and they deliver basic services to those most in need. As a result, they are able to more effectively mitigate the mortality effect of pollution for the poorest asset classes compared with that of the richest ones and thus reduce the health inequality it provokes.