Methods: This study is a longitudinal retrospective study with a nested case-control to identify risk factors of OA. The assessment of incidence evolution is made by exploring a series of promotions (or retrospective cohorts) with increasing duration since at work. The study population is composed of subjects who graduated between 2001 and 2006 in sectors where they experience exposure to organic or inorganic allergenic or irritant compounds (with an objective of 150 subjects by year) and 250 young workers with no specific occupational exposure.