Environmental concerns are increasingly being incorporated into regional trade agreements (RTAs) to promote environmental quality and ultimately ensure compatibility between trade and environmental policies. This occurs in a context where air pollution and its effects on human health are of major concern. This paper investigates whether the proliferation and depth of environmental provisions (EPs) in RTAs are associated with lower concentration levels of particulate matter. We present an index of EPs in RTAs that measures the breadth and depth of the provisions and use it to estimate the effect of ratifying RTAs with different levels of EPs on changes in PM2.5 concentration levels in a panel of OECD countries over the 1999–2011 period. Using an instrumental variables strategy, we find that countries that have ratified RTAs with EPs show lower levels of PM2.5 concentrations when we control for scale, composition and technique effects and for national environmental regulations. Moreover, the PM2.5 concentration levels in the pairs of countries that belong to an RTA with EPs tend to converge for the country sample. The results also hold for a longer period of time (1990–2011) and a broader sample of 173 countries as well as for other pollutants, namely CO2 and NO2.