Background: Occupational exposures are thought to be responsible for 10-15% of new-onset asthma cases in adults, with disparities across sectors. Because most of the data are derived from registries and cross-sectional studies, little is known about incidence of occupational asthma (OA) during the first years after inception of exposure. This study focuses on this early asthma onset period among young workers in the bakery, pastry making and hairdressing sectors in order to assess early incidence of OA in these "at risk" occupations according to exposure duration, and to identify risk factors of OA.

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.

This study is a descriptive, monocentric, longitudinal and retrospective study with cross-sectional measurements.

Inclusion Criteria:

• for the exposed group: to be graduated between 2001 and 2006 from nine vocational schools in Lorraine, North-Eastern France
• for the "non-exposed" group: to be graduated in 2001 in the sale or the food sectors (butcher, pork butcher, caterer, cook job,…) from the same vocational schools

Exclusion Criteria:

• asthma diagnosed before apprenticeship
• for the "non-exposed" group: to have worked previously or later in a sector at risk with OA

All bakers, pastry-makers and hairdressers who graduated between 2001 and 2006 from nine vocational schools in Lorraine, North-Eastern France, and all subjects who graduated in 2001 in the sale or the food sectors (butcher, pork butcher, caterer, cook job,…) from the same vocational schools.