LETTER Comparing JEMs in

population-based studies: what if expert assessment and measurements are not available? Authors ’ response We appreciate the opportunity to respond to the letter of Behrens and Taeger1 regarding our article ‘Comparison of expert and job-exposure matrix-based retrospective exposure assessment of occupational carcinogens in the Netherlands Cohort Study’.2 Behrens and Taeger raise concerns about ‘validating’ existing job-exposure matrices ( JEMs). Instead, they propose a recently devel-oped web-based tool into which existin