Is potroom asthma due more to sulphur dioxide than fluoride? An inception cohort study in the Australian aluminium industry.
OBJECTIVE
Although an asthma-like syndrome has been recognised in aluminium smelter workers for over 70 years, the causal agent has been difficult to identify.


METHODS
An inception cohort study was conducted at two Australian aluminium smelters where 446 employees participated over a period of 9 years. Cumulative exposures between interviews were estimated from job histories using a task exposure matrix based on measurements in the smelters. Participants completed an MRC respiratory questionnaire, spirometry and methacholine challenge test. Data were analysed with generalised estimating equations to allow for repeated measurements of each participant.


RESULTS
Wheeze and chest tightness, the two symptoms most closely related to asthma, showed associations with occupational exposures. SO(2) exposure was significantly associated with these symptoms, bronchial hyper-responsiveness (BHR) to methacholine (a feature of asthma), airflow limitation (reduced forced expiratory volume in 1 second/forced vital capacity ratio) and longitudinal decline in lung function. Fluoride exposure was associated with the same outcomes, but less strongly. Inhalable dust and the benzene soluble fraction (BSF) were associated with symptoms of asthma and BHR. Although many of the exposures were highly correlated, further modelling suggested that of the known respiratory irritants, SO(2) was more likely than fluoride to be primarily responsible for the symptoms observed. Fluoride, inhalable dust and SO(2) were the most important airborne contaminants associated with effects on lung function.


CONCLUSIONS
The observed effects were detected at contaminant levels within occupational exposure standards, so further reductions are required, particularly in SO(2) exposures.
Abramson
Michael John
MJ
Department of Epidemiology & Preventive Medicine, Monash University, School of Public Health & Preventive Medicine, The Alfred, Melbourne, Victoria 3004, Australia. michael.abramson@monash.edu
Benke
Geza Paul
GP
Cui
Jisheng
J
de Klerk
Nicholas Hubert
NH
Del Monaco
Anthony
A
Dennekamp
Martine
M
Fritschi
Lin
L
Musk
Arthur William
AW
Sim
Malcolm Ross
MR
D000328:Adult; D017677:Age Distribution; D000535:Aluminum; D001249:Asthma / Q000139:chemically induced* / Q000453:epidemiology / Q000503:physiopathology; D001315:Australia / Q000453:epidemiology; D004812:Epidemiologic Methods; D005260:Female; D005459:Fluorides / Q000633:toxicity*; D005541:Forced Expiratory Volume / Q000187:drug effects; D006801:Humans; D008297:Male; D008669:Metallurgy; D008875:Middle Aged; D009784:Occupational Diseases / Q000139:chemically induced* / Q000453:epidemiology / Q000503:physiopathology; D016273:Occupational Exposure / Q000009:adverse effects / Q000032:analysis; D017678:Sex Distribution; D013458:Sulfur Dioxide / Q000633:toxicity*; D014797:Vital Capacity / Q000187:drug effects; D055815:Young Adult
D013458:Sulfur Dioxide; D000535:Aluminum; D005459:Fluorides