Ayres and colleagues base their main criticisms on the inexact relationships between atmospheric emissions and personal exposures. They imply that the one was used improperly here as a poor surrogate for the other.1 2 This is a serious misrepresentation. There was no such usage. The utilised data were group-properties (SMRs, social attributes, and area-wide emissions) relating to Local Authorities (LAs), not to individuals. The objectives and the analyses were concerned only with relationships between these values and not at all with such intermediate factors as stack-heights, day-to-day temperature swings, certification anomalies, multiple diagnoses …