| Subjects n | 60 |
| Sex | |
| Male | 45 (75) |
| Female | 15 (25) |
| Age yrs | 42.9±11.0 |
| Atopy# | 42 (70) |
| Smoking habit | |
| Nonsmoker | 10 (16) |
| Ex-smoker | 25 (42) |
| Smoker | 25 (42) |
| Duration of exposure to causal agent yrs | 10.5 (3.1–22.8) |
| Years of exposure with symptoms before removal from exposure | 1.4 (0.1–7.5) |
| Married | 32 (53) |
| Having children to support | 40 (67) |
| Nature of causal agent | |
| High molecular weight | 26 (43) |
| Low molecular weight | 33 (55) |
| Salary (<30,000 CAD) | 24 (40) |
| Low income¶ | 9 (15) |
| Only primary and secondary level education | 33 (55) |
| Working for a company with <20 employees at diagnosis | 20 (33) |
| Working ≥5 yrs for same employer | 34 (57) |
| Member of a labour union | 28 (47) |
| Professional group | |
| Shopkeepers, craftsmen | 23 (38) |
| Professionals, managers, intermediate white collars, office and sales employees | 11 (18) |
| Skilled and unskilled workers | 26 (43) |
Data are presented as n (%), mean±sd or median (interquartile range), unless otherwise stated. #: atopy was defined by at least one immediate skin reaction to 15 ubiquitous aeroallergens; ¶: low income was defined as having an income at diagnosis that was <110% of the cut-off value for low income according to the definition adopted by Statistics Canada (Ottawa, ON, Canada).