Dust exposure assessed by a job exposure matrix is associated with increased annual decline in FEV1: a 5-year prospective study of employees in Norwegian smelters.
BACKGROUND
The relationship between dust exposure and annual decline in lung function among employees in the smelting industry is unknown.


OBJECTIVE
The aim of the study was to investigate the relationship between annual change in lung function and occupational dust exposure among workers in 15 Norwegian smelters.


METHODS
All employees (n = 2,620) were examined annually for 5 years (11,335 health examinations). At each examination spirometry was performed and a respiratory questionnaire was completed. The smelters were grouped as follows: (1) ferrosilicon alloys (FeSi) and silicon metal (Si-metal); and (2) silicon manganese (SiMn), ferromanganese (FeMn), and ferrochromium (FeCr). A job exposure matrix was available on the basis of 2,619 personal dust exposure measurements. The association between lung function expressed as FEV(1) and FVC per squared height (height(2)) and dust exposure was investigated using multivariate linear mixed model analyses.


RESULTS
The annual change in FEV(1)/height(2) (deltaFEV(1)) related to dust exposure in the FeSi/Si-metal and SiMn/FeMn/FeCr smelters was -0.42 (95% confidence interval, -0.95 to 0.11) and -1.1 (-2.1 to -0.12) (ml/m(2)) x (mg/m(3))(-1) x year(-1), respectively. The annual decline in FEV(1)/height(2) was 1.6 ml/m(2) (0.15 to 3.1) steeper in smokers than in nonsmokers. The median geometric mean of the time-weighted dust exposure concentration levels of the employees was 2.3 mg/m(3) in the FeSi/Si-metal smelters and 1.6 mg/m(3) in the SiMn/FeMn/FeCr smelters. Among nonsmokers, deltaFEV(1) was -0.86 (-1.6 to -0.10) and -1.1 (-2.5 to 0.25) (ml/m(2)) x (mg/m(3))(-1) x year(-1) in the FeSi/Si-metal and SiMn/FeMn/FeCr smelters, respectively. Thus, for a 1.80 m tall employee the annual decline in FEV(1) associated with average dust exposure was 5.7 ml/year in the SiMn/FeMn/FeCr smelters, and 6.4 ml/year for a nonsmoker in the FeSi/Si-metal smelters.


CONCLUSIONS
In all smelters combined, the annual change in FEV(1) was negatively associated with increasing dust exposure. This association was also significant among workers in SiMn/FeMn/FeCr smelters and among nonsmokers in the FeSi/Si-metal smelters.
Johnsen
Helle Laier
HL
Department of Medicine, Akershus University Hospital, Postbox 75, N-1478 Lørenskog, Norway. helle.laier@dadlnet.dk
Hetland
Siri M
SM
Benth
Jurate Saltyte
JS
Kongerud
Johny
J
Søyseth
Vidar
V
D000328:Adult; D001827:Body Height; D004391:Dust; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008669:Metallurgy; D015999:Multivariate Analysis; D009664:Norway / Q000453:epidemiology; D016273:Occupational Exposure / Q000009:adverse effects*; D011446:Prospective Studies; D012907:Smoking / Q000453:epidemiology; D013147:Spirometry; D014797:Vital Capacity
D004391:Dust