Exposure to substances in the workplace and new-onset asthma: an international prospective population-based study (ECRHS-II).
BACKGROUND
The role of exposure to substances in the workplace in new-onset asthma is not well characterised in population-based studies. We therefore aimed to estimate the relative and attributable risks of new-onset asthma in relation to occupations, work-related exposures, and inhalation accidents.


METHODS
We studied prospectively 6837 participants from 13 countries who previously took part in the European Community Respiratory Health Survey (1990-95) and did not report respiratory symptoms or a history of asthma at the time of the first study. Asthma was assessed by methacholine challenge test and by questionnaire data on asthma symptoms. Exposures were defined by high-risk occupations, an asthma-specific job exposure matrix with additional expert judgment, and through self-report of acute inhalation events. Relative risks for new onset asthma were calculated with log-binomial models adjusted for age, sex, smoking, and study centre.


RESULTS
A significant excess asthma risk was seen after exposure to substances known to cause occupational asthma (Relative risk=1.6, 95% CI 1.1-2.3, p=0.017). Risks were highest for asthma defined by bronchial hyper-reactivity in addition to symptoms (2.4, 1.3-4.6, p=0.008). Of common occupations, a significant excess risk of asthma was seen for nursing (2.2, 1.3-4.0, p=0.007). Asthma risk was also increased in participants who reported an acute symptomatic inhalation event such as fire, mixing cleaning products, or chemical spills (RR=3.3, 95% CI 1.0-11.1, p=0.051). The population-attributable risk for adult asthma due to occupational exposures ranged from 10% to 25%, equivalent to an incidence of new-onset occupational asthma of 250-300 cases per million people per year.


CONCLUSIONS
Occupational exposures account for a substantial proportion of adult asthma incidence. The increased risk of asthma after inhalation accidents suggests that workers who have such accidents should be monitored closely.
Kogevinas
Manolis
M
Centre for Research in Environmental Epidemiology, Municipal Institute of Medical Research, Barcelona, Spain. kogevinas@imim.es
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Lillienberg
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D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000209:etiology*; D016085:Bronchoconstrictor Agents; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D016273:Occupational Exposure / Q000009:adverse effects*; D009790:Occupations; D011159:Population Surveillance / Q000379:methods*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride