Study population and data collection
Epidemiological Study on the Risk of Asthma in Cleaning Workers 2 (EPIASLI2) was a
two-stage epidemiological study conducted to assess associations between cleaning work,
including specific worksites and exposures to cleaning products, and dermatological and
respiratory health symptoms (9). The study methods have been described previously (9).
Summarized briefly, between February and December 2008, 4 993 self-administered, paperand-
pencil-style questionnaires were distributed to employees of 37 cleaning companies
operating in the province of Barcelona, Spain. Nine hundred and fifty questionnaires were
returned by mail; of those, 132 (14%) were excluded because they were incomplete or
lacked responses to key questionnaire items and the remaining 818 respondents constituted our final study population for analyses of the cross-sectional survey data. Following the
cross-sectional survey, 95 participants were recruited into a nested case-control study
designed to further assess associations between cleaning work and respiratory disease (10).
Data for the sub-study were collected when participants completed a clinical examination
and an interviewer-administered questionnaire. For 70 of the 95 participants (74%), the
clinical examination included an in-person skin health evaluation, therefore our final study
population includes additional data collection for a subset of 70. The study was approved by
the ethics committee of the Instituto Municipal de Asistencia Sanitaria (IMAS) and the
analytical plan for this analysis was also approved by the Institutional Review Board of the
Wake Forest School of Medicine.