Exposure to substances at the workplace and new onset-asthma in a population-based study in northern Europe

Introduction
In a large longitudinal study among adults in northern Europe (RHINE) the relation between new-onset asthma and exposure to occupational agents has been studied.

Methods
The study group was 13 212 subjects born between 1945 and 1973, who had answered a baseline questionnaire in 1990-1991 and a follow-up questionnaire in 1999-2001. Hazard ratios (HR) were calculated for new-onset asthma during exposure-years in specific jobs or exposure groups using a job exposure matrix (JEM) adjusting for age, atopy and smoking using Cox regression models. The analyses were further stratified for atopy and age respectively. The reference group was subjects working in administrative or clerical jobs, teachers and others unlikely to be exposed.

Results
There were 455 subjects with new-onset asthma during the follow-up period from 1980 to 2000. A significant increase in the incidence of asthma was seen for male and female “cleaners and building caretakers” adjusting for age, atopy and smoking. Other low molecular weight (LMW) irritant asthmagens significantly increasing new-onset of asthma were “inorganic dust and welding fume” and “accidental peak exposure to irritants” in male workers. LMW sensitising asthmagens significantly increasing the asthma incidence were exposure to “reactive chemicals” in female workers and isocyanates in male workers. Significant increases in new-onset asthma were seen in male workers exposed to high molecular weight (HMW) “flour and other plant associated antigens”. Occupations with a significant excess risk of asthma were male building workers, plumbers and spray painters and among females in hairdressers and drivers. When stratifying for atopy higher asthma risks were in general seen among non-atopics compared to atopics.

Discussion
Subgroups of HMW and LMW agents contribute to the new-onset asthma. Cleaners and building caretakers have a high risk of getting asthma. Other high risk occupations were male plumbers and building workers and female hairdressers and drivers.