The article by Boffetta et al.  is a worthy contribution to the quantification of risk among responders exposed to intense pollution resulting from the collapse of the World Trade Center (WTC) in New York City in 2001. It provides a useful methodological comparison among three occupationally exposed cohorts of responders, demonstrating cohort design differences that nonetheless lead to consistency in cancer outcomes among each of them. In addition to the fine points made and results presented, I propose to the authors as leaders of each of the three different cohort studies what could perhaps be useful for further consideration in future follow-up and analyses: 1. Regarding the firefighter cohort, Boffetta et al. state “It is worth noting that an increased risk of prostate cancer, melanoma, and non-Hodgkin lymphoma has been observed in other studies of firefighters ...” Why then not do a comparison, adjusting for known excess cancers among firefighters absent the 9/11 exposure experience? This comparison would provide a further estimate of excess risk, if any, associated with exposures among responders in the WTC collapse.