The Six Cities Study by Dockery et al.1 has captured renewed attention (Jan. 8 issue).2,3 Claiming to identify an increased mortality rate in Steubenville, Ohio, as compared with the rate in Portage, Wisconsin, the authors posited that air pollution in Steubenville, an Ohio River Valley mining and steel-making city, was responsible for its increased death rate. That interpretation is not permissible, inasmuch as the socioeconomic and ethnic makeups of the populations of Portage and Steubenville are markedly different. Compounding that invidious comparison, the calculated difference in mortality rates is seen to be only a hair’s breadth within the bounds of statistical significance. Indeed, as shown in Table 2 of the report,1 there was no difference in mortality between women in Portage and women in Steubenville, who breathed the same air as men in that city. Steinbrook3 quotes David M. Michaels, formerlyformerly of the Clinton administration, who suggests that critics of clean-air studies are “hired guns working for dirty companies.” Joel Schwartz, later associated with the clean-air group at Harvard, reportedly dismissed critics of clean-air studies as “industry thugs.”4 Is this the language of collegial scientific discourse?