JNCI | Correspondence 1841jnci.oxfordjournals.org Re: The Diesel Exhaust in Miners Study: A Nested Case–Control Study of Lung Cancer and Diesel Exhaust and a Cohort Mortality Study With Emphasis on Lung Cancer When the Diesel Exhaust in Miners

Study (DEMS) was initiated in the early 1990s, one key goal was to develop quan-titative estimates of historical exposure to diesel exhaust (DE). It was recog-nized that the epidemiological results would only be as robust as the exposure assessment upon which they are based. Respirable elemental carbon (REC), a surrogate of diesel exhaust particulates, was selected as the primary exposure variable, yet in very recent years inves-tigators turned to an alternative expo-sure assessment methodology that relied instead on carbon monoxide (CO) meas-urements. Assumptions were also mad