Cotton dust and endotoxin levels in three Shanghai textile factories: a comparison of samplers

Byssinosis and lung health among cotton textile workers: baseline findings of the MultiTex trial in Karachi, Pakistan

OBJECTIVES

To assess the association of exposure in cotton mills in Karachi with different definitions of byssinosis and lung health.

METHODS

This cross-sectional survey took place between June 2019 and October 2020 among 2031 workers across 38 spinning and weaving mills in Karachi. Data collection involved questionnaire-based interviews, spirometry and measurements of personal exposure to inhalable dust. Byssinosis was defined using both WHO symptoms-based (work-related chest tightness), and Schilling's criteria (symptoms with decreased forced expiratory volume in 1 s (FEV₁). Values of FEV₁/forced vital capacity ratio below the lower limit of normality on postbronchodilator test were considered as 'chronic airflow obstruction' (CAO).

RESULTS

56% of participants had at least one respiratory symptom, while 43% had shortness of breath (grade 1). Prevalence of byssinosis according to WHO criteria was 3%, it was 4% according to Schilling's criteria, and likewise for CAO. We found low inhalable dust exposures (geometric mean: 610 µg/m³). Cigarette smoking (≥3.5 pack-years), increasing duration of employment in the textile industry and work in the spinning section were important factors found to be associated with several respiratory outcomes.

CONCLUSION

We found a high prevalence of respiratory symptoms but a low prevalence of byssinosis. Most respiratory outcomes were associated with duration of employment in textile industry. We have discussed the challenges faced in using current, standard guidelines for identifying byssinosis.

Reduced Cross-Shift Lung Function and Respiratory Symptoms among Integrated Textile Factory Workers in Ethiopia

Chronic respiratory symptoms and reduction in lung function has been described as a common health problem among textile workers in low- and middle-income countries. The objective of this study was to measure lung function and respiratory symptoms among workers from an integrated textile factory. A comparative cross-sectional study design with a cross-shift lung function measurement was performed in 306 cotton dust exposed workers from an integrated textile factory and 156 control workers from a water bottling factory. An integrated textile factory typically has four main production departments (spinning, weaving, finishing, and garment) that process raw cotton and manufacture clothes or fabrics. Respiratory symptoms were assessed by adopting the standard American Thoracic Society questionnaire. Descriptive statistics and logistic and linear regression analysis were used. The prevalence of respiratory symptoms was significantly higher among textile workers (54%) than in controls (28%). Chronic cough, chest tightness, and breathlessness were significantly higher among textile workers (23%, 33%, and 37%, respectively) than in the control group (5%, 17% and 6%, respectively). Breathlessness was the most prevalent chronic respiratory symptom with highest adjusted odds ratio 9.4 (95% CI 4.4–20.3). A significantly higher cross-shift lung function reduction was observed among textile workers (123 mL for FEV₁ and 129 mL for FVC) compared with the control group (14 mL for FEV₁ and 12 mL for FVC). Thus, workers’ respiratory health protection programs should be strengthened in textile factories.

Risk of Pancreatic Cancer in Female Textile Workers in Shanghai, China, Exposed to Metals, Solvents, Chemicals, and Endotoxin: Follow-Up to a Nested Case-Cohort Study

OBJECTIVE

We studied associations between pancreatic cancer and occupational exposures to metals, solvents, chemicals, and endotoxin in a cohort of female textile workers in Shanghai, China. To assess the longer-term influences of these agents on pancreatic cancer we extended follow-up of this previously studied cohort.

METHODS

We utilized a job exposure matrix to assess occupational exposures for 481 pancreatic cancer cases and a randomly selected sub-cohort of 3191 non-cases. We calculated hazard ratios and 95% confidence intervals using Cox proportional hazards modeling adapted for the case-cohort design.

RESULTS

We observed a statistically significant trend of increasing hazard ratios associated with solvent exposure, but no associations with any of the remaining occupational exposures, including endotoxin and metals.

CONCLUSIONS

Our findings of increasing risk of pancreatic cancer with solvent exposures are consistent with published literature.

Occupational exposures and risk of stomach and esophageal cancers: update of a cohort of female textile workers in Shanghai, China

BACKGROUND

Associations between stomach and esophageal cancer and exposures to dusts, metals, chemicals, and endotoxin in the workplace are not very well understood, particularly in women.

METHODS

We followed 267,400 female textile workers in Shanghai, China for cancer incidence from 1989 to 2006. Stomach (n = 1374) and esophageal (n = 190) cancer cases were identified and a comparison subcohort (n = 3187) was randomly selected. Cox proportional hazard modeling was used, adjusting for age and smoking.

RESULTS

Increasing stomach cancer risk was observed with increasing duration of synthetic fiber dust exposure (p = 0.03), although the magnitude of effect was small (20 + years: HR = 1.2, 95% CI 1.1-1.4). Trends with endotoxin exposure were modestly inversed for esophageal cancer and increased for stomach cancer, but with little deviation from a null association.

CONCLUSIONS

Our findings demonstrate that long durations of synthetic fiber dust exposure can increase stomach cancer risk in women, but provide limited support for associations with other textile industry exposures.

Night shift work and lung cancer risk among female textile workers in Shanghai, China

In 2007, the International Agency for Research on Cancer classified shift work that involves circadian disruption as a probable human carcinogen. Suppression of the anti-neoplastic hormone, melatonin, is a presumed mechanism of action. We conducted a case-cohort study nested within a cohort of 267,400 female textile workers in Shanghai, China. Newly diagnosed lung cancer cases (n = 1451) identified during the study period (1989-2006) were compared with an age-stratified subcohort (n = 3040). Adjusting for age, smoking, parity, and endotoxin exposure, relative risks [hazard ratios (HRs)] were estimated by Cox regression modeling to assess associations with cumulative years and nights of rotating shift work. Results did not consistently reveal any increased risk of lung cancer among rotating shift work or statistically significant trends for both cumulative years (HR 0.82, 95% CI 0.66 to 1.02; P(trend) = 0.294) and nights (HR 0.81, 95% CI 0.65 to 1.00; P(trend) = 0.415). Further analyses imposing 10- and 20-year lag times for disease latency also revealed similar results. Contrary to the initial hypothesis, rotating nighttime shift work appears to be associated with a relatively reduced lung cancer risk although the magnitude of the effect was modest and not statistically significant.

Possible pro-carcinogenic association of endotoxin on lung cancer among Shanghai women textile workers

Background:

Endotoxin (lipopolysaccharide) is a widespread contaminant in many environmental settings. Since the 1970s, there has been generally consistent evidence indicating reduced risks for lung cancer associated with occupational endotoxin exposure.

Methods:

We updated a case–cohort study nested within a cohort of 267 400 female textile workers in Shanghai, China. We compared exposure histories of 1456 incident lung cancers cases diagnosed during 1989–2006 with those of a reference subcohort of 3022 workers who were free of lung cancer at the end of follow-up. We applied Cox proportional hazards modelling to estimate exposure–response trends, adjusted for age and smoking, for cumulative exposures lagged by 0, 10, and 20 years, and separately for time windows of ⩽15 and >15 years since first exposure.

Results:

We observed no associations between cumulative exposure and lung cancer, irrespective of lag interval. In contrast, analyses by exposure time windows revealed modestly elevated, but not statistically significant relative risks (∼1.27) at the highest three exposure quintiles for exposures that occurred >15 years since first exposure.

Conclusions:

The findings do not support a protective effect of endotoxin, but are suggestive of possible lung cancer promotion with increasing time since first exposure.

Occupational exposures and mortality from cardiovascular disease among women textile workers in Shanghai, China

BACKGROUND

Exposure to textile fiber dusts, like particulate air pollution, may be associated with cardiovascular disease (CVD) mortality. Bacterial endotoxin, a potent inflammagen found in cotton dust, may be a specific risk factor.

METHODS

Female textile workers (N = 267,400) in Shanghai, China were followed for CVD mortality (1989-2000). Factory exposures were approximated by sector classifications based on materials and processes. Quantitative endotoxin and cotton dust measures were available for a subcohort (n = 3,188). Cox proportional hazards modeling was used to estimate hazard ratios (HR) and 95% confidence interval (CI).

RESULTS

Slightly elevated mortality risk for the cotton sector was seen for ischemic stroke (HR = 1.12, 95% CI: 0.97-1.31) and hemorrhagic stroke (HR = 1.12, 95% CI: 1.02-1.23). Similar hemorrhagic stroke mortality risk was observed in high dust sectors (HR = 1.12, 95% CI: 1.02-1.24). No association was observed for ischemic heart disease.

CONCLUSIONS

Exposures in textile factories may have contributed to CVD mortality among this cohort. The specific components of these exposures that may be harmful are not clear and should be further investigated.

Measurement of endotoxins in bioaerosols at workplace: a critical review of literature and a standardization issue

Endotoxins are lipopolysaccharides found in the outer membrane of most Gram-negative bacteria and cyanobacteria. Worker exposure to endotoxins has been shown in a number of work situations and is associated with both respiratory and systemic pathologies. The lack of an occupational exposure limit is mainly due to the absence of a standard protocol at the international level for sampling and analyzing airborne endotoxins. The bibliographic review in this article takes an exhaustive look at the current knowledge on measuring airborne endotoxins. It shows that, despite several reference documents at the international level, the methods used to measure endotoxin exposure differ considerably from one laboratory to another. Standardization is necessary to reduce interlaboratory variability and, ultimately, to improve the use of interstudy data. The bibliographic review presents the current status of standardization for airborne endotoxin measurement methods in the workplace and summarizes areas for further research. This article is both a reference document for all operators wishing to use such methods and a working document to build international consensus around the measurement of airborne endotoxins.

Association of endotoxins and colon polyp: a case-control study

Endotoxins are known to be associated with the occurrence of various chronic diseases. This study was conducted to investigate the role of endotoxins in the pathogenesis of colon polyps through a case-control study. A total of 145 subjects (74 subjects in the polyp group and 71 subjects in the control group) had undergone a colonoscopy. Age, body mass index (BMI) and endotoxin levels were found to be significantly higher in the polyp group than in the control group. The endotoxin level was still significantly higher in the polyp group than in the control group, even after age and BMI had been adjusted (polyp group 0.108 ± 0.007 EU/mL, control group 0.049 ± 0.008 EU/mL, P < 0.001). In subgroup analysis, the endotoxin level significantly increased in accordance with the number of colon polyps (one-polyp group, 0.088 ± 0.059 EU/mL; two-polyp group, 0.097 ± 0.071 EU/mL; three-or-more-polyp group, 0.149 ± 0.223 EU/mL). The endotoxin levels also significantly increased in groups with tubular adenoma with high-grade dysplasia (hyperplastic polyp group, 0.109 ± 0.121 EU/mL; tubular adenoma with low grade dysplasia group, 0.103 ± 0.059 EU/mL; tubular adenoma with high grade dysplasia group, 2.915 ± 0.072 EU/mL). In conclusion, the serum level of endotoxins is quantitatively correlated with colon polyps.

Lung cancer mortality in a cohort of UK cotton workers: an extended follow-up

Background:

A recent systematic review and meta-analysis suggested that occupational exposure to endotoxins protects against lung cancer. To explore this hypothesis further, the follow-up of mortality of a cohort of 3551 workers, who were employed in the British cotton industry during 1966–1971, was extended by 23 years.

Methods:

Subjects had originally been recruited to a survey of respiratory disease, which collected information about occupation and smoking habits. Cumulative exposures to endotoxins were estimated from data on endotoxin levels by work areas in cotton mills. Risks of lung cancer were estimated using survival modelling.

Results:

During follow-up, 2018 deaths were recorded before the age of 90 years, including 128 deaths from lung cancer. After adjustment for smoking, hazard ratios (95% confidence intervals) for cumulative endotoxin exposures of ⩽30 000, >30 000 and ⩽200 000, >200 000 and ⩽400 000, >400 000 and ⩽600 000 and >600 000 endotoxin units (EU) m⁻³ years were 1, 0.8 (0.5–1.6), 0.7 (0.4–1.3), 0.6 (0.3–1.0) and 0.5 (0.3–0.9), respectively (P for trend=0.005).

Conclusion:

Our findings strengthen the evidence that occupational exposure to endotoxins protects against lung cancer, and suggest that the effect depends on cumulative dose and persists after exposure ceases.

Risk of lung cancer in relation to contiguous windows of endotoxin exposure among female textile workers in Shanghai

OBJECTIVE

Exposure to endotoxin has been consistently associated with a reduced risk of lung cancer. However, there is a paucity of information regarding temporal aspects of this relationship. The objective of this study was to investigate the associations between contiguous windows of endotoxin exposure and risk of lung cancer.

METHODS

Data were reanalyzed from a case-cohort study (602 cases, 3,038 subcohort) of female textile workers in Shanghai, China. Cumulative endotoxin exposure was partitioned into two windows: ≥20 and <20 years before risk. Exposure-response relations were examined using categorical and non-linear (semi-parametric) models, accounting for confounding by previous exposure windows.

RESULTS

There was an inverse trend of decreasing risk of lung cancer associated with increasing levels of endotoxin exposure ≥20 years before risk (p trend = 0.02). Women in the highest two categories of cumulative exposures had hazard ratios of 0.78 (95% CI 0.60-1.03) and 0.77 (95% CI 0.58-1.02) for lung cancer, respectively, in comparison with unexposed textile workers. There was, however, a weaker association and not statistically significant between lung cancer and endotoxin exposure accumulated in the more recent window (<20 years before risk).

CONCLUSION

Results provide further evidence that endotoxin exposure that occurred 20 years or more before risk confers the strongest protection against lung cancer, indicating a possible early anti-carcinogenic effect. Further studies are needed to better understand the underlying biological mechanisms for this effect.

Lung cancer and occupational exposures other than cotton dust and endotoxin among women textile workers in Shanghai, China

OBJECTIVES

Numerous epidemiological studies of lung cancer among textile workers worldwide consistently indicate reduced risks related to cotton dust exposure, presumably due to endotoxin contamination. Our objective was to investigate associations with other exposures potentially related to lung cancer, including wool and synthetic fibre dusts, formaldehyde, silica, dyes and metals, that have only been studied to a limited extent in the textile industry.

METHODS

We conducted a case-cohort study nested within a cohort of 267,400 women textile workers in Shanghai, China. We compared work assignments and exposure histories of 628 incident lung cancer cases, diagnosed during 1989-1998, with those of a reference subcohort of 3188 workers. We reconstructed exposures with a job-exposure matrix developed specifically for textile factories. Cox proportional hazards modelling was applied to estimate age/smoking-adjusted relative risks (hazard ratios) and risk gradients associated with job assignments and specific agents other than cotton dust and endotoxin.

RESULTS

No associations were observed for lung cancer with wool, silk or synthetic fibre dusts, or with most other agents. However, increased risks, although statistically imprecise, were noted for ≥ 10 years' exposures to silica (adjusted HR 3.5, 95% CI 1.0 to 13) and ≥ 10 years' exposures to formaldehyde (adjusted HR 2.1, 95% CI 0.4 to 11).

CONCLUSIONS

Exposures to silica and formaldehyde, although not widespread among the cohort, may have increased lung cancer risk. Silica is an established human lung carcinogen, whereas there is only weak prior evidence supporting an association with formaldehyde. Both exposures warrant consideration as potential lung carcinogens in textile manufacturing.

Wood dust exposure and risk of lung cancer

OBJECTIVES

Despite the compelling association between wood dust and sinonasal cancer, there has been little systematic and rigorous study of the relationship between wood dust and lung cancer. We investigated whether a history of wood dust exposure through occupational and hobby-related activities was associated with increased lung cancer risk.

METHODS

We conducted a population-based case-control study, with 440 cases and 845 age-matched controls. Using detailed work and personal histories, quantitative estimates of cumulative exposure to wood dust (thought to be primarily from softwood) were calculated for each participant. Using unconditional logistic regression adjusted for age and smoking status, risk of lung cancer was examined in relation to employment in wood-related occupations, working with wood as a hobby, as well as cumulative wood dust exposure that took into account both occupational and hobby-related sources.

RESULTS

While we observed an increased risk of lung cancer associated with working in a sawmill (OR=1.5; 95% CI: 1.1, 2.1), we found no evidence of increased risks with other occupations, working with wood as a hobby or with estimated cumulative exposure to wood dust. Contrary to our hypothesis, we observed modest decreased risks with exposure to wood dust, although no dose-response relationship was apparent.

CONCLUSIONS

This study provided somewhat reassuring evidence that softwood dust does not increase the risk of lung cancer, but future studies should evaluate exposure to hardwood dusts. Suggestive evidence for an inverse association may be attributable to the presence of endotoxin in the wood dust, but the lack of a dose-response relationship suggests a non-causal relationship.

Endotoxin and cancer

Exposure to endotoxin, a component of gram-negative bacterial cell walls, is widespread in many industrial settings and in the ambient environment. Heavy-exposure environments include livestock farms, cotton textile facilities, and saw mills. In this article, we review epidemiologic, clinical trial, and experimental studies pertinent to the hypothesis that endotoxin prevents cancer. Since the 1970s, epidemiologic studies of cotton textile and other endotoxin-exposed occupational groups have consistently demonstrated reduced lung cancer risks. Experimental animal toxicology research and some limited therapeutic trials in cancer patients offer additional support for an anticarcinogenic potential. The underlying biological mechanisms of anticarcinogenesis are not entirely understood but are thought to involve the recruitment and activation of immune cells and proinflammatory mediators (e.g., tumor necrosis factor α and interleukin-1 and -6). In view of the current state of knowledge, it would be premature to recommend endotoxin as a cancer-chemopreventive agent. However, further epidemiologic and experimental investigations that can clarify further dose-effect and exposure-timing relations could have substantial public health and basic biomedical benefits.

Endotoxin and cancer

OBJECTIVE

Exposure to endotoxin, a component of gram-negative bacterial cell walls, is widespread in many industrial settings and in the ambient environment. Heavy-exposure environments include livestock farms, cotton textile facilities, and saw mills. Concentrations are highly variable in non-occupational indoor and outdoor environments. Endotoxin is a potent inflammagen with recognized health effects, including fever, shaking chills, septic shock, toxic pneumonitis, and respiratory symptoms. Somewhat paradoxically, given the putative role of inflammation in carcinogenesis, various lines of evidence suggest that endotoxin may prevent cancer initiation or limit tumor growth. The hypothesis that components of bacteria may retard cancer progression dates back to William B. Coley's therapeutic experiments ("bacterial vaccine") in the 1890s.

DATA SOURCES

In this article, we review epidemiologic, clinical trial, and experimental studies pertinent to the hypothesis that endotoxin prevents cancer. Since the 1970s, epidemiologic studies of cotton textile and other endotoxin-exposed occupational groups have consistently demonstrated reduced lung cancer risks. Experimental animal toxicology research and some limited therapeutic trials in cancer patients offer additional support for an anticarcinogenic potential. The underlying biological mechanisms of anticarcinogenesis are not entirely understood but are thought to involve the recruitment and activation of immune cells and proinflammatory mediators (e.g., tumor necrosis factor alpha and interleukin-1 and -6).

CONCLUSIONS

In view of the current state of knowledge, it would be premature to recommend endotoxin as a cancer-chemopreventive agent. Nonetheless, further epidemiologic and experimental investigations that can clarify further dose-effect and exposure-timing relations could have substantial public health and basic biomedical benefits.

Dust and chemical exposures, and miscarriage risk among women textile workers in Shanghai, China

INTRODUCTION

To investigate possible associations between miscarriage and occupational exposures in the Shanghai textile industry.

METHODS

A retrospective cohort study of miscarriages among 1752 women in the Shanghai textile industry was conducted. Reproductive history was self-reported by women and occupational work histories were collected from factory personnel records. Occupational exposures were assigned by linking work history information to an industry-specific job-exposure matrix informed by factory-specific textile process information and industrial hygiene assessments. Estimates of cotton dust and endotoxin exposure were also assigned. Odds ratios (OR) and 95% CI were estimated by multivariate logistic regression, with adjustment for age at pregnancy, educational level, smoking status of the woman and her spouse, use of alcohol, and woman's year of birth.

RESULTS

An elevation in risk of a spontaneously aborted first pregnancy was associated with exposure to synthetic fibres (OR 1.89, 95% CI 1.20 to 3.00) and mixed synthetic and natural fibres (OR 3.31, 95% CI 1.30 to 8.42). No increased risks were observed for women working with solvents, nor were significant associations observed with quantitative cotton dust or endotoxin exposures. Associations were robust and similar when all pregnancies in a woman's reproductive history were considered.

CONCLUSIONS

Occupational exposure to synthetic fibres may cause miscarriages, and this possibility should be the subject of further investigation.

Occupational risk factors for endometrial cancer among textile workers in Shanghai, China

OBJECTIVE

A case-cohort study was conducted to investigate associations between occupational exposures and endometrial cancer nested within a large cohort of textile workers in Shanghai, China.

METHODS

The study included 176 incident endometrial cancer cases diagnosed from 1989 to 1998 and a randomly-selected age-stratified reference subcohort (n = 3,061). Study subjects' complete work histories were linked to a job-exposure matrix developed specifically for the textile industry to assess occupational exposures. Hazard ratios (HR) and 95% confidence intervals were calculated using Cox proportional hazards modeling adapted for the case-cohort design, adjusting for age at menarche and a composite variable of gravidity and parity.

RESULTS

An increased risk of endometrial cancer was detected among women who had worked for > or =10 years in silk production (HR = 3.8, 95% CI 1.2-11.8) and had exposure to silk dust (HR = 1.7, 95% CI 0.9-3.4). Albeit with few exposed women (two cases and eight subcohort women), there was a 7.4-fold increased risk associated with > or =10 years of silica dust exposure (95% CI 1.4-39.7).

CONCLUSIONS

The findings suggest that some textile industry exposures might play a role in endometrial carcinoma and should be further replicated in other occupational settings.

Occupational exposures and ovarian cancer in textile workers

BACKGROUND

Occupational risk factors for ovarian cancer have been investigated only to a limited extent. We conducted a case-cohort study to examine associations between occupational exposures and ovarian cancer in the textile industry.

METHODS

We compared 261 incident ovarian cancer cases diagnosed between 1989 and 1998 with an age-stratified reference subcohort (n = 3199) from a cohort of 267,400 textile workers in Shanghai, China. Occupational exposures were assessed by job-exposure matrices designed for the textile industry, and estimates of quantitative cotton dust and endotoxin. We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) with Cox proportional hazards modeling adapted for the case-cohort design.

RESULTS

A decreased risk of ovarian cancer was associated with ever having worked in cotton manufacturing production (HR = 0.7; 95% CI = 0.4-1.0). An increased risk was associated with ever having worked in textile finishing (2.1; 0.9-5.0). We found an increasing risk of ovarian cancer associated with cumulative exposure to silica dust (for <10 years exposure, HR = 6.8 [CI = 0.6-76]; for > or =10 years, 5.6 [1.3-23.6]), although these results are based on only 8 exposed subcohort women (0.3%) and 4 cases (1.3%). We also detected inverse risk gradients for cumulative exposures to endotoxin when exposures were lagged by 20 years (in highest quartile, HR = 0.6 [CI = 0.4-1.1]).

CONCLUSION

Silica dust may increase the risk of ovarian cancer, and cotton dust and endotoxin may reduce risk.

Lung cancer risk among female textile workers exposed to endotoxin

BACKGROUND

Reduced risk of lung cancer among workers in the cotton textile industry has been observed since the 1970s. Bacterial endotoxin, a contaminant of raw cotton fiber and cotton dust, has been proposed as a protective agent that may act through the innate and acquired immune systems. We examine the association between endotoxin exposure and lung cancer risk in a cohort of female textile workers.

METHODS

We conducted a case-cohort study nested within a cohort of 267,400 female textile workers in Shanghai, China. We compared the cumulative exposure histories of 628 case patients diagnosed with incident lung cancer from January 1, 1989, through December 31, 1998, with those of a lung cancer-free reference subcohort of 3184 workers who were frequency matched by 5-year age-groups to all cancer patients in the cohort. Cumulative endotoxin exposure for all participants was based on historic measurements and on additional measurements for this study. Relative risks and 95% confidence intervals (CIs) were estimated by hazard ratios (HRs) from Cox proportional hazards models. We conducted exposure-response trend analyses by use of cumulative exposures with lag times of 0, 5, 10, 15, or 20 years to account for disease latency. All analyses controlled for age and smoking status. All statistical tests were two-sided.

RESULTS

Cumulative exposure to endotoxin was strongly, statistically significantly, and inversely associated with lung cancer risk. The inverse trend was greatest with a 20-year lag time, for which highest endotoxin exposure was associated with a statistically significantly 40% less risk of lung cancer (HR = 0.60, 95% CI = 0.43 to 0.83; P(trend) across quintiles = .002) than non-exposure. From a reported population rate of lung cancer among women in Shanghai of 19.1 per 100,000 for the year 2000 and the estimated reduction in risk of lung cancer observed for 20 years of endotoxin exposure in this population of workers, the incidence of lung cancer in this cohort was reduced by approximately 7.6 per 100,000 (range = 3.2-10.9 per 100,000).

CONCLUSIONS

Long-term and high-level exposure to endotoxin, compared with no exposure, appears to be associated with a reduced risk of lung cancer in this cohort.