Abstract In this article we examine historical changes in anti-sapstain fungicide application in the western Canadian lumber industry. Modifications have included (1) changes in fungicide formulations, (2) substitution with new fungicides, and (3) changes in application technology. The data were collected during three related studies: a retrospective cohort study of chlorophenate-exposed sawmill workers; a study of the acute effects of substitute fungicides; and a cross-sectional survey of fungicide application techniques in sawmills and shipping terminals. We discovered that chlorophenate formulations and application technology were changed without systematic collection of data to evaluate their impact on worker exposure. Cross-sectional surveys examining a wide range of technologies, or studies of exposure before and after changes are made, would allow more methodical evaluation of engineering changes in the future. We also found that substitution of new fungicide active ingredients occurred before a fu...