Reply to the recent article by Boffetta et al. [28(5):913 915] on attribution of cancer to the environment.

In reference to the recent global estimate of attributable fraction of 19% of cancers to the environment, Boffetta et al. (2) argue that a systematic combination of errors in epidemiological study design may have ‘led to estimates of cancers attributable to pollution one order of magnitude larger than the range of reasonably accepted estimates’.