The purpose of the study presented here was to simultaneously measure air quality and respiratory function and symptoms in populations living in the neighborhood of waste incinerators and to estimate the contribution of incinerator emissions to the particulate air mass in these neighborhoods. We studied the residents of three communities having, respectively, a biomedical and a municipal incinerator, and a liquid hazardous waste-burning industrial furnace. We compared results with three matched-comparison communities. We did not detect differences in concentrations of particulate matter among any of the three pairs of study communities. Average fine particulate (PM2.5) concentrations measured for 35 days varied across study communities from 16 to 32 micrograms/m3. Within the same community, daily concentrations of fine particulates varied by as much as eightfold, from 10 to 80 micrograms/m3, and were nearly identical within each pair of communities. Direct measurements of air quality and estimates based on a chemical mass balance receptor model showed that incinerator emissions did not have a major or even a modest impact on routinely monitored air pollutants. A onetime baseline descriptive survey (n = 6963) did not reveal consistent community differences in the prevalence of chronic or acute respiratory symptoms between incinerator and comparison communities, nor did we see a difference in baseline lung function tests or in the average peak expiratory flow rate measured over a period of 35 days. Based on this analysis of the first year of our study, we conclude that we have no evidence to reject the null hypothesis of no acute or chronic respiratory effects associated with residence in any of the three incinerator communities.