Response to Criticism of “Fine Particulate Matter and Total Mortality in Cancer Prevention Study Cohort Reanalysis”

Drs C. Arden Pope III (Pope), Daniel Krewski (Krewski), Susan M. Gapstur (Gapstur), Michelle C. Turner (Turner), Michael Jerrett (Jerrett), and Richard T. Burnett (Burnett), as well as Gapstur and Otis W. Brawley (Brawley) strongly criticized my Dose-Response article, Enstrom, but they did not identify a single error, particularly regarding my findings of no relationship between fine particulate matter (PM2.5) and total (all-cause) mortality. Thus, my peer-reviewed findings showing no PM2.5-related deaths during 1982 to 1988 in the 1982 American Cancer Society (ACS) Cancer Prevention Study (CPS II) cohort stand unchallenged. In particular, my null findings indicate that the positive findings in 3 seminal publications by these investigators: Pope and Health Effects Institute, HEI (2000) and HEI (2009), are not robust and not supportive of the claim that PM2.5 causes premature deaths. Instead of assessing the validity of my findings, these investigators focused on other aspects of their many analyses of CPS II data. Their “Expanded Analyses of the ACS CPS-II Cohort” section inaccurately questions the validity of my findings: “The assertion regarding selective use of the CPS-II and PM2.5 data is false.” I published prima facie evidence that their 1982 to 1989 PM2.5 mortality findings were indeed sensitive to selective use of PM2.5 and CPS II data. My evidence can be easily checked with minor modifications to the SAS programs that they used to calculate the findings in Table 34 of HEI (2009). Instead of confirming or refuting my evidence, these investigators reiterated their various published analyses of PM2.5 deaths in CPS II, as summarized in their Table 1 and their Figure 1. All of their analyses could be just as sensitive to selective use of PM2.5 and CPS II data as the results in Pope, HEI (2000), and HEI (2009). Their “Deficiencies in Enstrom’s Reanalysis” section does not identify a single error in my findings and suggests that they did not examine the data and findings in my article. For instance, they state, “In contrast, Enstrom asserts that he estimates smaller PM2.5-mortality associations because he uses the ‘best’ PM2.5 data. He provides no evidence in support of this assertion nor does he provide any measures of the relative quality of models using alternative PM2.5 data.” Strong evidence supporting my assertion is clearly presented in Tables 2 and 3 of my article and is described in the “Results” section on page 4. Then, they state, “It is not clear how or why his ‘IPN’ PM2.5 data differ from the ‘HEI’ PM2.5 data—especially given that these data come from the same monitoring network.” The differences between the Inhalable Particulate Network (IPN) PM2.5 and HEI PM2.5 data are clearly shown in my Appendix Table A1 and discussed in the “Conclusion” section on page 6. To make sure that these differences are fully recognized and understood, an expanded version of Appendix Table A1 is shown in Table 1. Their “Broader Evidence” section is not relevant to the validity of my findings and diverts attention away from my challenge to the PM2.5 death findings in Pope, HEI (2000), and HEI (2009). Their last paragraph contains the following inaccurate statement: “But the study by Enstrom does not contribute to the larger body of evidence on the health effects of PM2.5 . . . ” In conclusion, the authors have not assessed the validity of my peer-reviewed evidence of no relationship between PM2.5 and total mortality in the CPS II cohort and have not been willing to engage with me in addressing the substantive points of my findings.