Evaluation of the health impact of lowering the formaldehyde occupational exposure limit for Quebec workers

This study aimed at assessing the impact on irritating effects of lowering the current occupational exposure limit (OEL) for formaldehyde in occupational settings in the Province of Quebec, Canada, from a 2 ppm ceiling value to 1, 0.75 or 0.3 ppm. This was achieved through (i) a re-assessment of the exposure–response relationship based on a pooled analysis of published controlled human studies on the incidence of the most sensitive effects related to acute formaldehyde exposure (irritation of the eyes, nose and throat) and (ii) application of this relationship to the data on current exposure to formaldehyde in industrial sectors of Quebec. Results show that the exposure-irritating effect relationship compiled by concentration ranges and by degree of severity was best described by quadratic regression. Considering the current distribution of formaldehyde exposure among the 143,491 Quebec workers concerned, eye irritation, the most sensitive effect, could affect 526 workers (0.367%) at a moderate degree and 50 workers (0.035%) at a severe degree. By reducing the OEL to 1, 0.75 and 0.3 ppm, the proportion of these effects estimated to be avoided would be 442/526 (84%), 526/526 (100%) and 526/526 (100%), respectively. Results for nose and throat irritation follow the same trend. The greatest gain would thus be obtained by respecting the current OEL; the additional gain was estimated to be negligible below 0.75 ppm. The level of 0.75 ppm can be considered as a safe level that allows protecting virtually all workers.