Follow-up study of workers in a nylon carpet yarn plant after remedial actions taken against a contaminated humidification system

Objective: To investigate the effectiveness of remedial actions taken against a contaminated humidification system, after an outbreak of humidifier disease in a nylon carpet yam plant. Methods: Two and 6 years after modification, a follow-up investigation of a strati tied (age, smoking habits) sample of exposed (n = 75) and non-exposed (n = 56) workers was carried out. Outcome-parameters were. respiratory symptoms, spirometry, skin tests and serology with various humidifier fungi. In addition, the yearly incidence of work-disability because of chronic respiratory disease during the years before, and 11 years after the modification was compared. Results: At follow-up, exposed workers, who remained at the same workplace no longer had significantly more frequent chronic respiratory symptoms. The prevalence of positive serology was still higher (P