The incidence of respiratory symptoms and diseases among pulp mill workers with peak exposures to ozone and other irritant gases.
OBJECTIVE
Pulp mills in Sweden started to use ozone as a bleaching agent in the early 1990s. The goal of this study was to investigate whether the incidence of selected respiratory outcomes was associated with peak exposures to ozone or other irritant gases (ie, chlorine dioxide [ClO2] or sulfur dioxide [SO2]) used in these mills.


METHODS
Bleachery workers (n = 245) from three pulp mills where ozone was used participated in surveys in the mid- to late-1990s. Comparison workers (n = 80) were from two adjacent paper mills. The person-time at risk was calculated for each participant, covering the period of employment when ozone was used. Data were collected by questionnaire, and a peak exposure was defined as a self-reported exposure to an irritant gas resulting in acute respiratory symptoms. The outcomes analyzed were self-reports of physician-diagnosed asthma, attacks of wheeze, and chronic bronchitis (ie, chronic cough with phlegm). Participants also reported when the peak exposures and outcomes occurred.


RESULTS
Based on proportional hazards regression (controlling for gender, age, cigarette smoking, atopy, and peak irritant exposures that occurred before follow-up), workers who reported both ozone and ClO2/SO2 peak exposures had elevated hazard ratios (HRs) for all three outcomes. Those who reported only ozone peak exposures had elevated HRs of 6.5 (95% confidence interval [CI], 1.2 to 36.3) for asthma and 3.3 (95% CI, 1.1 to 10.2) for attacks of wheeze but no increase in risk for chronic bronchitis. Workers with only ClO2/SO2 peak exposures had elevated HRs for attacks of wheeze (HR, 7.5; 95% CI, 1.9 to 29.3) and chronic bronchitis (HR, 22.9; 95% CI, 4.5 to 118.2) but not for asthma.


CONCLUSIONS
These findings suggest the need for additional efforts to prevent peak exposures in pulp-bleaching operations.
Henneberger
Paul K
PK
National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, MS-H2800, 1095 Willowdale Rd, Morgantown, WV 26505, USA. pkh0@cdc.gov
Olin
Anna-Carin
AC
Andersson
Eva
E
Hagberg
Stig
S
Torén
Kjell
K
D001249:Asthma / Q000139:chemically induced / Q000453:epidemiology / Q000517:prevention & control; D001991:Bronchitis / Q000209:etiology / Q000517:prevention & control; D017606:Chlorine Compounds / Q000633:toxicity; D005740:Gases; D006306:Health Surveys; D006801:Humans; D007509:Irritants / Q000633:toxicity*; D009784:Occupational Diseases / Q000139:chemically induced* / Q000453:epidemiology / Q000517:prevention & control; D016273:Occupational Exposure / Q000517:prevention & control; D010087:Oxides / Q000633:toxicity; D010126:Ozone / Q000633:toxicity*; D012135:Respiratory Sounds / Q000209:etiology; D012140:Respiratory Tract Diseases / Q000139:chemically induced* / Q000453:epidemiology / Q000517:prevention & control; D013458:Sulfur Dioxide / Q000633:toxicity; D013548:Sweden / Q000453:epidemiology
D017606:Chlorine Compounds; D005740:Gases; D007509:Irritants; D010087:Oxides; D013458:Sulfur Dioxide; D010126:Ozone; C025109:chlorine dioxide