A year-round air monitoring program for sulfur dioxide, sulfates, nitrogen dioxide, nitrates, ozone, and total suspended particulates was conducted in three towns with population densities ranging from 29/km2 to 1178/km2. The results showed significant differences in concentrations of several pollutants between the urban town and the two rural towns. However, site-to-site variation over distances of 1 mile or less within the urban area was considerable. To express pollutant loads in each town in a single number, we calculated a combined pollutant index on premises similar to those used for combined occupational exposures, but with U.S. primary air quality standards rather than threshold limit values as indices of minimal health effects. The combined index exceeded unity in all three towns, suggesting either that total pollutant loads may be excessive even in the sparsely populated town of Lebanon, Connecticut, or, more likely, that the U.S. primary air quality standards have been set at low levels without due regard for additive effects.