The article entitled “Atmospheric pollutants and mortalities in English local authority areas” by Knox analysed a large body of epidemiological data linking various forms of air pollution to the death rates from several diseases, including pneumonia, chronic obstructive pulmonary disease and lung cancer.1

I want to suggest that in some cases the author unknowingly misclassified the exposure, and that the associations with carbon monoxide (CO) and nitrogen dioxide (NO_{2 …}