Endotoxin and gender modify lung function recovery after occupational organic dust exposure: a 30-year study.

OBJECTIVES: The purpose of this study is to determine the trajectory of lung function change after exposure cessation to occupational organic dust exposure, and to identify factors that modify improvement. METHODS: The Shanghai Textile Worker Study is a longitudinal study of 447 cotton workers exposed to endotoxin-containing dust and 472 silk workers exposed to non-endotoxin-containing dust. Spirometry was performed at 5-year intervals. Air sampling was performed to estimate individual cumulative exposures. The effect of work cessation on forced expiratory volume in 1 s (FEV1) was modelled using generalised additive mixed effects models to identify the trajectory of FEV1 recovery. Linear mixed effects models incorporating interaction terms were used to identify modifiers of FEV1 recovery. Loss to follow-up was accounted for with inverse probability of censoring weights. RESULTS: 74.2% of the original cohort still alive participated in 2011. Generalised additive mixed models identified a non-linear improvement in FEV1 for all workers after exposure cessation, with no plateau noted 25 years after retirement. Linear mixed effects models incorporating interaction terms identified prior endotoxin exposure (p=0.01) and male gender (p=0.002) as risk factors for impaired FEV1 improvement after exposure cessation. After adjusting for gender, smoking delayed the onset of FEV1 gain but did not affect the overall magnitude of change. CONCLUSIONS: Lung function improvement after cessation of exposure to organic dust is sustained. Endotoxin exposure and male gender are risk factors for less FEV1 improvement.

Gender differences in the effect of occupational endotoxin exposure on impaired lung function and death: the Shanghai Textile Worker Study.

OBJECTIVE: Airborne endotoxin exposure has adverse and protective health effects. Studies show men have augmented acute inflammatory responses to endotoxin. In this longitudinal cohort study we investigated the effect of long-term exposure to endotoxin in cotton dust on health, and determined whether these effects differ by gender. METHODS: In the Shanghai Textile Worker Study, 447 cotton and 472 control silk textile workers were followed from 1981 to 2011 with repeated measures of occupational endotoxin exposure, spirometry and health questionnaires. Impaired lung function was defined as a decline in forced expiratory volume in one second to less than the 5th centile of population predicted. Death was ascertained by death registries. We used Cox proportional hazards models to assess the effect of endotoxin exposure on the time to development of impaired lung function and death. RESULTS: 128 deaths and 164 diagnoses of impaired lung function were ascertained between 1981 and 2011. HRs for the composite end point of impaired lung function or death was 1.47 (95% CI 1.09 to 1.97) for cotton vs silk workers and 1.04 (95% CI 1.01 to 1.07) per 10 000 endotoxin units (EU)/m(3)-years increase in exposure. HRs for all-cause mortality was 1.36 (95% CI 0.93 to 1.99) for cotton vs silk workers and 1.04 (95% CI 0.99 to 1.08) per 10 000 EU/m(3)-years. The risk associated with occupational endotoxin exposure was elevated only in men. CONCLUSIONS: Occupational endotoxin exposure is associated with an increase in the risk of impaired lung function and all-cause mortality in men.

Household solid fuel use and pulmonary function in an urban population in Shanghai, China.

OBJECTIVES: We examined the association between household solid fuel exposure and lung function in a densely populated district in urban Shanghai, China. METHODS: Spirometry was performed in 12 506 subjects, aged 18 and over, residing in the Putuo District in Shanghai, China, in a cross-sectional survey. Exposure to solid fuel use at home was assessed by an administered questionnaire, estimating duration and total amount of solid fuel use at home during the lifetime. RESULTS: After adjusting for confounders, the subjects with exposure to household solid fuel had a 1.3% (95% CI 0.57 to 2.02) decrease in forced expiratory volume in 1 s (FEV(1)) percent predicted and 3.5% (95% CI 2.74 to 4.18) decrease in forced vital capacity (FVC) percent predicted, respectively. Trends towards decreased pulmonary function measures were seen for longer duration and greater amount of household fuel use at home, in the highest compared with lowest tertile (p values for trend <0.001). We observed decrease in FEV(1) and FVC percent predicted across increase in tertile of body mass index in association with in-home solid fuel exposure. CONCLUSIONS: This study suggests that in-home solid fuel exposure is associated with reduced lung function in an urban population.

Imaging Phenotype of Occupational Endotoxin-Related Lung Function Decline.

BACKGROUND: Although occupational exposures contribute to a significant proportion of obstructive lung disease, the phenotype of obstructive lung disease associated with work-related organic dust exposure independent of smoking remains poorly defined. OBJECTIVE: We identified the relative contributions of smoking and occupational endotoxin exposure to parenchymal and airway remodeling as defined by quantitative computed tomography (CT). METHODS: The Shanghai Textile Worker Study is a longitudinal study of endotoxin-exposed cotton workers and endotoxin-unexposed silk workers that was initiated in 1981. Spirometry, occupational endotoxin exposure, and smoking habits were assessed at 5-year intervals. High-resolution computed tomography (CT) was performed in 464 retired workers in 2011, along with quantitative lung densitometric and airway analysis. RESULTS: Significant differences in all CT measures were noted across exposure groups. Occupational endotoxin exposure was associated with a decrease (-1.3%) in percent emphysema (LAAI-950), a 3.3-Hounsfield unit increase in 15th percentile density, an 18.1-g increase in lung mass, and a 2.3% increase in wall area percent. Current but not former smoking was associated with a similar CT phenotype. Changes in LAAI-950 were highly correlated with 15th percentile density (correlation -1.0). Lung mass was the only measure associated with forced expiratory volume in 1 sec (FEV1) decline, with each 10-g increase in lung mass associated with an additional loss (-6.1 mL) of FEV1 (p = 0.001) between 1981 and 2011. CONCLUSIONS: There are many similarities between the effects of occupational endotoxin exposure and those of tobacco smoke exposure on lung parenchyma and airway remodeling. The effects of occupational endotoxin exposure appear to persist even after the cessation of exposure. LAAI-950 may not be a reliable indicator of emphysema in subjects without spirometric impairment. Lung mass is a CT-based biomarker of accelerated lung function decline. CITATION: Lai PS, Hang J, Zhang F, Sun J, Zheng BY, Su L, Washko GR, Christiani DC. 2016. Imaging phenotype of occupational endotoxin-related lung function decline. Environ Health Perspect 124:1436-1442; http://dx.doi.org/10.1289/EHP195.