Endotoxin exposure and lung cancer risk: a systematic review and meta-analysis of the published literature on agriculture and cotton textile workers

[Results of Lung Cancer Screening with Low-dose Computed Tomography and Exploration of Risk Factors in Guangzhou]

BACKGROUND

Both of lung cancer incidence and mortality rank first among all cancers in China. Previous lung cancer screening trials were mostly selective screening for high-risk groups such as smokers. Non-smoking women accounted for a considerable proportion of lung cancer cases in Asia. This study aimed to evaluate the outcome of community-based mass screening in Guangzhou and identify the high-risk factors for lung cancer.

METHODS

Residents aged 40-74 years in Guangzhou were screened with low-dose computed tomography (LDCT) for lung cancer and the pulmonary nodules were classified and managed according to China National Lung Cancer Screening Guideline with Low-dose Computed Tomography (2018 version). The detection rate of positive nodules was calculated. Before the LDCT examination, residents were required to complete a "lung cancer risk factors questionnaire". The risk factors of the questionnaire were analyzed by least absolute shrinkage and selection operator (LASSO) penalized Logistic regression analysis.

RESULTS

A total of 6256 residents were included in this study. 1228 positive nodules (19.63%) and 117 lung cancers were confirmed, including 6 cases of Tis, 103 cases of stage I (accounting for 88.03% of lung cancer). The results of LASSO penalized Logistic regression analysis indicated that age ≥50 yr (OR=1.07, 95%CI: 1.06-1.07), history of cancer (OR=3.29, 95%CI: 3.22-3.37), textile industry (OR=1.10, 95%CI: 1.08-1.13), use coal for cooking in childhood (OR=1.14, 95%CI: 1.13-1.16) and food allergy (OR=1.10, 95%CI: 1.07-1.13) were risk factors of lung cancer for female in this district.

CONCLUSIONS

This study highlighted that numerous early stages of lung cancer cases were detected by LDCT, which could be applied to screening of lung cancer in women. Besides, age ≥50 yr, personal history of cancer, textile industry and use coal for cooking in childhood are risk factors for women in this district, which suggested that it's high time to raise the awareness of early lung cancer screening in this group.

Occupational exposure to endotoxins and small cell lung cancer: a systematic review with meta-analysis

The relationship of occupational exposure to endotoxins with different histologic subtypes of lung cancer has not been established. Our objective was to conduct a systematic review with meta-analysis to assess the effect of exposure to endotoxins on the development of small cell lung cancer (SCLC). A bibliographic search was conducted using MEDLINE, Embase, CENTRAL, and Web of Science databases until December 2022, including all cohort and/or case-control studies that examined occupational exposure to endotoxins and SCLC. Risk of bias was assessed using the U.S. Office of Health Assessment and Translation tool. A random effects model was applied, publication bias were assessed, and a sensitivity analysis was conducted. Four papers were selected for meta-analysis purposes. A total of 144 incident cases of SCLC and 897 population or hospital controls were included. Occupational exposure to endotoxins was considered for textile/leather industry and agricultural sector workers exposed to endotoxins originating from wool, cotton, or leather dust. Except for one study, all investigations were classified as having a low probability of risk of biases. The results of the meta-analysis were not statistically significant (pooled OR: 0.86; 95% CI:0.69-1.08). In addition, neither between-study heterogeneity (I2=0%;p=0.92) nor publication bias was observed (p=0.49). The results of the sensitivity analysis, after including five studies that assessed the risk of SCLC among textile industry and crop/livestock farm workers (not specifically exposed to endotoxins), showed a negative statistically non-significant association and low between-study heterogeneity (pooled OR: 0.90; 95% CI:0.79-1.02; I2=22%;p=0.23). Subjects exposed to occupational exposure to endotoxins seem to exhibit a negative association with the development of SCLC, although the results are not conclusive.

Prevalent occupational exposures and risk of lung cancer among women: Results from the application of the Canadian Job-Exposure Matrix (CANJEM) to a combined set of ten case-control studies

BACKGROUND

Worldwide, lung cancer is the second leading cause of cancer death in women. The present study explored associations between occupational exposures that are prevalent among women, and lung cancer.

METHODS

Data from 10 case-control studies of lung cancer from Europe, Canada, and New Zealand conducted between 1988 and 2008 were combined. Lifetime occupational history and information on nonoccupational factors including smoking were available for 3040 incident lung cancer cases and 4187 controls. We linked each reported job to the Canadian Job-Exposure Matrix (CANJEM), which provided estimates of probability, intensity, and frequency of exposure to each selected agent in each job. For this analysis, we selected 15 agents (cleaning agents, biocides, cotton dust, synthetic fibers, formaldehyde, cooking fumes, organic solvents, cellulose, polycyclic aromatic hydrocarbons from petroleum, ammonia, metallic dust, alkanes C18+, iron compounds, isopropanol, and calcium carbonate) that had lifetime exposure prevalence of at least 5% in the combined study population. For each agent, we estimated lung cancer risk in each study center for ever-exposure, by duration of exposure, and by cumulative exposure, using separate logistic regression models adjusted for smoking and other covariates. We then estimated the meta-odds ratios using random-effects meta-analysis.

RESULTS AND CONCLUSIONS

None of the agents assessed showed consistent and compelling associations with lung cancer among women. The following agents showed elevated odds ratio in some analyses: metallic dust, iron compounds, isopropanol, and organic solvents. Future research into occupational lung cancer risk factors among women should prioritize these agents.

An Updated Evaluation of Atrazine-Cancer Incidence Associations among Pesticide Applicators in the Agricultural Health Study Cohort

BACKGROUND

Atrazine is a common agricultural herbicide in the United States. Few epidemiologic studies have evaluated cancer risks. Previous analyses within the Agricultural Health Study (AHS) have found some evidence of associations with cancer at some sites.

OBJECTIVE

We updated exposure information, incident cases, and follow-up time to assess the associations between atrazine use and cancer at specific sites in the AHS.

METHODS

Information about lifetime pesticide use was reported at enrollment (1993-1997) and follow-up (1999-2005). Among 53,562 pesticide applicators in North Carolina and Iowa, we identified 8,915 incident cases through cancer registry linkages through 2014 (North Carolina)/2017 (Iowa). We used Poisson regression to evaluate the association between ever/never and intensity-weighted lifetime days of atrazine use and incident cancer risk controlling for several confounders. We also evaluated lagged exposures and age-stratified risk.

RESULTS

Approximately 71.2% of applicators reported ever using atrazine, which was associated with lung cancer [rate ratios  ( RR ) = 1.24 ; 95% confidence interval (CI): 1.04, 1.46]. Aggressive prostate cancer risk was increased in the highest quartile (RR Q 4 = 1.20 ; 95% CI: 0.95, 1.52; p -trend = 0.19 ), particularly among those < 60 years old (RR Q 4 = 3.04 ; 95% CI: 1.61, 5.75; p -trend < 0.001 ; p -interaction = 0.04 ). Among applicators < 50 years of age, ever-atrazine use was associated with non-Hodgkin lymphoma (NHL) (RR = 2.43 ; 95% CI: 1.10, 5.38; p -interaction = 0.60 ). For soft tissue sarcoma, there was an elevated risk in the highest tertile of exposure (RR T 3 : 2.54; 95% CI: 0.97, 6.62; p -trend = 0.31 ). In analyses with exposure lagged by 25 years, there was an elevated risk of pharyngeal (RR T 3 = 3.04 ; 95% CI: 1.45, 6.36; p -trend = 0.07 ) and kidney (RR Q 4 = 1.62 ; 95% CI: 1.15, 2.29; p -trend < 0.005 ) cancers.

DISCUSSION

We observed suggestive associations with some malignancies in overall, age-specific, and lagged analyses. Associations with aggressive prostate cancer and NHL were apparent among those diagnosed at younger ages and with cancers of the pharynx and kidney, and soft tissue sarcomas were observed in lagged analyses. Further work is needed to confirm these observed associations and elucidate potential underlying mechanisms. https://doi.org/10.1289/EHP13684.

Expansion of distinct peripheral blood myeloid cell subpopulations in patients with rheumatoid arthritis-associated interstitial lung disease

OBJECTIVES

Interstitial lung disease (ILD) is associated with significant mortality in rheumatoid arthritis (RA) patients with key cellular players remaining largely unknown. This study aimed to characterize inflammatory and myeloid derived suppressor cell (MDSC) subpopulations in RA-ILD as compared to RA, idiopathic pulmonary fibrosis (IPF) without autoimmunity, and controls.

METHODS

Peripheral blood was collected from patients with RA, RA-ILD, IPF, and controls (N = 60, 15/cohort). Myeloid cell subpopulations were identified phenotypically by flow cytometry using the following markers:CD45,CD3,CD19,CD56,CD11b,HLA-DR,CD14,CD16,CD15,CD125,CD33. Functionality of subsets were identified with intracellular arginase-1 (Arg-1) and inducible nitric oxide synthase (iNOS) expression.

RESULTS

There was increased intermediate (CD14++CD16+) and nonclassical (CD14+/-CD16++) and decreased classical (CD14++CD16-) monocytes in RA, RA-ILD, and IPF vs. control. Intermediate monocytes were higher and classical monocytes were lower in RA-ILD vs. RA but not IPF. Monocytic (m)MDSCs were higher in RA-ILD vs. control and RA but not IPF. Granulocytic (g)MDSCs did not significantly differ. In contrast, neutrophils were increased in IPF and RA-ILD patients with elevated expression of Arg-1 sharing similar dimensional clustering pattern. Eosinophils were increased in RA-ILD vs. controls, RA and IPF. Across cohorts, iNOS was decreased in intermediate/nonclassical monocytes but increased in mMDSCs vs. classical monocytes. In RA-ILD, iNOS positive mMDSCs were increased versus classic monocytes.

CONCLUSIONS

Myeloid cell subpopulations are significantly modulated in RA-ILD patients with expansion of CD16+ monocytes, mMDSCs, and neutrophils, a phenotypic profile more aligned with IPF than other RA patients. Eosinophil expansion was unique to RA-ILD, potentially facilitating disease pathogenesis and providing a future therapeutic target.

Systematic review and meta-analysis of the potential threats to respiratory health from microbial Bioaerosol exposures

Infectious diseases are a part of everyday life, and acute respiratory diseases are the most common. Many agents carrying out respiratory infections are transmitted as bioaerosols through the air, usually, particulate matter containing living organisms. The purpose of the study is to conduct a systematic review and meta-analysis to assess the likelihood that people exposed to bioaerosols may experience severe respiratory diseases. Nine digital databases and bibliographies were assessed for papers conducted between January 1960 and April 2021. A total of 35 health and exposure studies were included from 825 studies for the systematic review, while only 17 contented the meta-inclusion analysis's criteria. This systematic review found higher bacterial bioaerosol concentrations in poultry farms, waste dumpsites, composting plants, and paper industries. The meta-analysis's Standard Mean Difference (SMD) measurement indicates a substantially positive association between bioaerosol exposure and respiratory disease outcomes in targeted populations. The value is 0.955 [95% CI, range 0.673-1.238; p < 0.001]. As per the Risk of Bias (ROB) findings, most of findings (30 out of 35 [85.71%]) were judged to have low ROB. From the random effect probit model, the total relative risk is 1.477 (95% CI, range 0.987-2.211), indicating a higher risk of respiratory diseases from bioaerosol exposure than the control groups. The total risk difference is 0.121 (95% CI, -0.0229 to 0.264), which means intervention groups may have a higher risk of respiratory diseases from continuous bioaerosol exposure than the control groups. The dose-response relationship revealed a strong positive linear coefficient correlation between bacterial & fungal bioaerosol exposure to respiratory health. Based on self-reported outcomes in those studies, The systematic review and meta-analysis stated that bioaerosol exposure had an effect on pulmonary health.

RKHS-based covariate balancing for survival causal effect estimation

Survival causal effect estimation based on right-censored data is of key interest in both survival analysis and causal inference. Propensity score weighting is one of the most popular methods in the literature. However, since it involves the inverse of propensity score estimates, its practical performance may be very unstable, especially when the covariate overlap is limited between treatment and control groups. To address this problem, a covariate balancing method is developed in this paper to estimate the counterfactual survival function. The proposed method is nonparametric and balances covariates in a reproducing kernel Hilbert space (RKHS) via weights that are counterparts of inverse propensity scores. The uniform rate of convergence for the proposed estimator is shown to be the same as that for the classical Kaplan-Meier estimator. The appealing practical performance of the proposed method is demonstrated by a simulation study as well as two real data applications to study the causal effect of smoking on survival time of stroke patients and that of endotoxin on survival time for female patients with lung cancer respectively.

Endotoxin Tolerance Creates Favourable Conditions for Cancer Development

Endotoxin tolerance (ET) is an adaptive phenomenon of the immune system that protects the host from clinical complications due to repeated exposure of the body to endotoxins such as lipopolysaccharide (LPS). Since ET is an immunosuppressive mechanism in which a significant reprogramming of macrophages is observed, we hypothesized that it could influence cancer development by modifying the tumour environment. This study aimed to explore whether ET influences cancer progression by altering the tumour microenvironment. Endotoxin-tolerant macrophages (MoET) were examined for their impact on breast and colon cancer cells via direct interaction and conditioned media exposure. We characterized cancer cell behaviour by viability, clonogenic potential, motility, scratch assays, and 3D spheroidal assays. MoET-derived factors increased cancer cell viability, motility, and clonogenicity, suggesting a conducive environment for cancer development. Remarkably, despite reduced TNFα and IL-6 levels, MoET exhibited M1 polarization. These findings uncover an ET-associated macrophage reprogramming that fosters a favourable context for cancer progression across diverse tumours. Targeting ET could emerge as a promising avenue for cancer therapy and prevention.

Association of immunotoxicological indices with lung cancer biomarkers in poultry, grape, and rose farming workers

Exposure to occupational hazards like dust, pesticides, diesel emission particles, or physical hazards in the agricultural sector is known to cause adverse health effects on farm workers. Our study aimed at addressing the association of immunomodulatory status with plasma levels of lung cancer biomarkers in farming population, attempting to recognition of vulnerable farming group. Blood samples from apparently healthy 51 chicken husbandry, 19 grape orchard, and 21 rose greenhouse workers were subjected to evaluate plasma levels of two representative lung cancer biomarkers, pro-gastrin releasing peptide (Pro-GRP) and cytokeratin fragment 19 (CYFRA 21-1). Peripheral blood mononuclear cells obtained from farmers were used for natural killer (NK) cell phenotyping and cytokines (interferon-gamma, IFN-γ and interleukin-13, IL-13) profiling in the culture supernatant. Compared to the rose greenhouse farmers, the grape orchard and chicken husbandry workers revealed a significantly upregulated plasma Pro-GRP and CYFRA 21-1 level. A low proportion of NK cells was observed among the female grape orchard workers and a lowered IFN- γ:IL-13 ratio was seen in the grape and chicken husbandry workers than the rose workers. Our findings imply that grape orchard and chicken husbandry workers have more disturbed immune homeostasis implicated with augmentation in the levels of lung cancer biomarkers than the rose greenhouse workers.

Cancer risks in a population-based study of agricultural workers: results from the Taiwan's Farmers and Health Cohort study

OBJECTIVE

The purpose of this study was to assess cancer risk among agricultural workers compared to the general population.

METHODS

The study utilized data from Farmers' Health Insurance (FHI) in Taiwan, which enrolled agricultural workers (N=1 175 149). The enrolled workers were matched to a general population (N=1 175 149) of the same age, gender, township, and enrollment year. The study population was linked to the National Cancer Registry to identify new cancer cases between 2000 and 2018. The Cox proportional hazards model was used to estimate the hazard ratio and 95% confidence interval for outcomes.

RESULTS

During the study period, 136 913 new cancers among agricultural workers were identified. The study found that male farmers had an increased cancer risk, including lymphocytic leukemia, chronic myelogenous leukemia, non-Hodgkin's lymphoma (NHL), oral cancer, lip cancer, esophagus cancer, rectum and rectosigmoid junction cancer, liver and intrahepatic bile duct cancer, lung cancer, trachea and bronchi cancer, and other non-melanoma skin cancer, even when considering the latency period. Female farmers had an elevated risk of multiple myeloma and other non-melanoma skin cancer. Moreover, only lymphoma, NHL, other lymphoid, and multiple myeloma, were both found to occur at different insurance periods.

CONCLUSIONS

This study provides farmer cancer patterns and risk, adding to the evidence that farmers are at increased risk of certain types of cancer, especially for hematological cancers. As exposure varies by farm operation type, individual farmer exposure may vary widely. Further understanding of the complex relationship between occupational exposure, environmental factors, and lifestyle factors is needed.

An algorithm for quantitatively estimating occupational endotoxin exposure in the biomarkers of exposure and effect in agriculture study: II. Application to the study population

BACKGROUND

We developed an algorithm to quantitatively estimate endotoxin exposure for farmers in the Biomarkers of Exposure and Effect in Agriculture (BEEA) Study.

METHODS

The algorithm combined task intensity estimates derived from published data with questionnaire responses on activity duration to estimate task-specific cumulative endotoxin exposures for 13 tasks during four time windows, ranging from "past 12 months" to "yesterday/today." We applied the algorithm to 1681 participants in Iowa and North Carolina. We examined correlations in endotoxin metrics within- and between-task. We also compared these metrics to prior day full-shift inhalable endotoxin concentrations from 32 farmers.

RESULTS

The highest median task-specific cumulative exposures were observed for swine confinement, poultry confinement, and grind feed. Inter-quartile ranges showed substantial between-subject variability for most tasks. Time window-specific metrics of the same task were moderately-highly correlated. Between-task correlation was variable, with moderately-high correlations observed for similar tasks (e.g., between animal-related tasks). Prior day endotoxin concentration increased with the total metric and with task metrics for swine confinement, clean other animal facilities, and clean grain bins.

SIGNIFICANCE

This study provides insight into the variability and sources of endotoxin exposure among farmers in the BEEA study and summarizes exposure estimates for future investigations in this population.

Exposição ocupacional e câncer: uma revisão guarda-chuva

Resumo Objetivo: fornecer uma visão geral das associações entre exposição ocupacional e risco da ocorrência ou morte por câncer. Métodos: esta revisão guarda-chuva da literatura utilizou as bases Medline e Web of Science. A partir de protocolo de busca, foram incluídas metanálises para diversas circunstâncias ocupacionais e cânceres selecionados que possuíssem algum nível de evidência para associação com ocupação. Resultados: foram incluídas 37 metanálises, abrangendo 18 localizações de câncer. Considerando a avaliação da heterogeneidade dos estudos, da qualidade da evidência e da força de associação, obteve-se evidências altamente sugestivas de associações entre exposição a solvente e mieloma múltiplo; amianto e câncer de pulmão; hidrocarbonetos e câncer de trato aerodigestivo superior; e estresse ocupacional e câncer colorretal. Conclusão: há evidências robustas para associar exposições ocupacionais e tipos de câncer não previstos, inicialmente, nas orientações de vigilância do câncer relacionado ao trabalho no Brasil. Permanecem lacunas sobre exposições de grande relevância, que carecem de metanálises mais consistentes, por exemplo, exposição a poeiras inorgânicas e câncer de pulmão e mesotelioma; exposição a solventes e tumores hematológicos. Evidências de câncer em outras regiões anatômicas foram menos robustas, apresentando indícios de incerteza ou viés.

Occupational exposure and cancer: an umbrella review

Abstract Objective: to provide an overview of the associations between occupational exposure and risk of occurrence or death from cancer. Methods: this umbrella review used the Medline and Web of Science databases. Based on the search protocol, meta-analysis was included for several occupational circumstances and selected cancers that had some level of evidence associated with the occupation. Results: 37 meta-analysis were included, covering 18 cancer locations. By assessing the heterogeneity of studies, quality of evidence, and strength of association, results highly indicated associations between solvent exposure and multiple myeloma, asbestos and lung cancer, hydrocarbons and upper aerodigestive tract cancer, occupational stress and colorectal cancer. Conclusion: robust evidence shows an association between occupational exposures and types of cancer not initially foreseen in the guidelines for work-related cancer surveillance in Brazil. Gaps in relevant exposures require further research and more consistent meta-analysis, including: exposure to inorganic dust and lung cancer and mesothelioma; solvents and hematological tumors. Evidence of cancer in other anatomical regions was less robust, showing signs of uncertainty or bias.

Cancer incidence in agricultural workers: Findings from an international consortium of agricultural cohort studies (AGRICOH)

BACKGROUND

Agricultural work can expose workers to potentially hazardous agents including known and suspected carcinogens. This study aimed to evaluate cancer incidence in male and female agricultural workers in an international consortium, AGRICOH, relative to their respective general populations.

METHODS

The analysis included eight cohorts that were linked to their respective cancer registries: France (AGRICAN: n = 128,101), the US (AHS: n = 51,165, MESA: n = 2,177), Norway (CNAP: n = 43,834), Australia (2 cohorts combined, Australian Pesticide Exposed Workers: n = 12,215 and Victorian Grain Farmers: n = 919), Republic of Korea (KMCC: n = 8,432), and Denmark (SUS: n = 1,899). For various cancer sites and all cancers combined, standardized incidence ratios (SIR) and 95% confidence intervals (CIs) were calculated for each cohort using national or regional rates as reference rates and were combined by random-effects meta-analysis.

RESULTS

During nearly 2,800,000 person-years, a total of 23,188 cancers were observed. Elevated risks were observed for melanoma of the skin (number of cohorts = 3, meta-SIR = 1.18, CI: 1.01-1.38) and multiple myeloma (n = 4, meta-SIR = 1.27, CI: 1.04-1.54) in women and prostate cancer (n = 6, meta-SIR = 1.06, CI: 1.01-1.12), compared to the general population. In contrast, a deficit was observed for the incidence of several cancers, including cancers of the bladder, breast (female), colorectum, esophagus, larynx, lung, and pancreas and all cancers combined (n = 7, meta-SIR for all cancers combined = 0.83, 95% CI: 0.77-0.90). The direction of risk was largely consistent across cohorts although we observed large between-cohort variations in SIR for cancers of the liver and lung in men and women, and stomach, colorectum, and skin in men.

CONCLUSION

The results suggest that agricultural workers have a lower risk of various cancers and an elevated risk of prostate cancer, multiple myeloma (female), and melanoma of skin (female) compared to the general population. Those differences and the between-cohort variations may be due to underlying differences in risk factors and warrant further investigation of agricultural exposures.

Circulating miRNAs as molecular markers of occupational grain dust exposure

Dust from grain and feed production may cause adverse health effects in exposed workers. In this study we explored circulating miRNAs as potential biomarkers of occupational grain dust exposure. Twenty-two serum miRNAs were analyzed in 44 grain dust exposed workers and 22 controls. Exposed workers had significantly upregulated miR-18a-5p, miR-124-3p and miR-574-3p, and downregulated miR-19b-3p and miR-146a-5p, compared to controls. Putative target genes for the differentially expressed miRNAs were involved in a range of Kyoto Encyclopedia of Genes and Genomes signaling pathways, and ‘Pathways in cancer’ and ‘Wnt signaling pathway’ were common for all the five miRNAs. MiRNA-diseases association analysis showed a link between the five identified miRNAs and several lung diseases terms. A positive correlation between miR-124-3p, miR-18a-5p, and miR-574-3p and IL-6 protein level was shown, while miR-19b-3p was inversely correlated with CC-16 and sCD40L protein levels. Receiver-operating characteristic analysis of the five miRNA showed that three miRNAs (miR-574-3p, miR-124-3p and miR-18a-5p) could distinguish the grain dust exposed group from the control group, with miR-574-3p as the strongest predictor of grain dust exposure. In conclusion, this study identified five signature miRNAs as potential novel biomarkers of grain dust exposure that may have potential as early disease markers.

Characterization of inhalable endotoxin, glucan, and dust exposures in Iowa farmers

BACKGROUND

The observed deficit of lung cancer in farmers has been partly attributed to exposure to organic dusts and endotoxins based largely on surrogate metrics. To move beyond these surrogates for etiological studies, we characterized task-based and time-weighted average (TWA) exposure to inhalable endotoxin, (1 → 3)-β-D-glucan, and dust in Iowa farmers.

METHODS

We collected 320 personal inhalable dust samples from 32 farmers during 69 sample days in 2015 and 2016. Samples were collected using Button aerosol samplers and analyzed for endotoxin using a kinetic chromogenic amebocyte lysate assay, and for (1 → 3)-β-D-glucan using a Limulus endpoint assay. We assessed relationships between bioaerosol concentrations and selected tasks and farm characteristics using linear mixed-effects models.

RESULTS

Bedding work, hog handling, and working in barn/confinement buildings, grain bins, and grain elevators were associated with higher endotoxin exposure. We found a monotonic trend between higher endotoxin concentrations and increasing number of animals. Bedding work, cleaning, and feed/grain storage work were associated with higher (1 → 3)-β-D-glucan concentrations. The median concentrations by task spanned one order of magnitude for inhalable dust and two orders of magnitude for endotoxin and (1 → 3)-β-D-glucan. Pearson correlations between endotoxin and glucan concentrations were 0.22 for TWA exposure and 0.56 for task samples.

CONCLUSIONS

This characterization of exposure factors that influence bioaerosol concentrations can support the development of refined bioaerosol exposure metrics for future etiologic analyses of cancer and other health outcomes in farmers.

Cotton dust exposure and risk of lung cancer: A meta-analysis of observational studies

Findings on the association between cotton dust exposure and lung cancer risk in epidemiologic studies have been inconsistent. Therefore, we conducted a meta-analysis of data from observational studies to quantify this association.PubMed, EMBASE, and the Cochrane library databases were searched for observational studies with data on cotton dust exposure and lung cancer risk. Studies that reported adjusted relative risks (RRs) with 95% confidence intervals (CIs) of lung cancer associated with cotton dust exposure were included. Subgroup analyses were conducted according to key characteristics.Fifteen studies involving a total of 73,812 individuals were included in the meta-analysis. Combining estimates from all the 15 observational studies, cotton dust exposure was associated with a decreased risk of lung cancer (combined RR, 0.78; 95% CI, 0.66-0.91; P = .002). Pooled estimates of multivariate RRs by gender were 0.71 (95% CI, 0.58-0.88; P = .001) among males, based on 7 studies, and 0.77 (95% CI, 0.67-0.89; P < .001) among females, based on 9 studies. Further analyses examining the influence of a single study on the results by omitting a study at each turn yielded a range of RR from 0.74 to 0.82.Our meta-analysis indicates that cotton dust exposure is associated with a decreased risk of lung cancer.

A Review of Potential Public Health Impacts Associated With the Global Dairy Sector

Strong demand for dairy products has led to a global increase in dairy production. In many parts of the world, dairy systems are undergoing rapid intensification. While increased production may contribute to food security, higher dairy stocking rates in some regions have resulted in increased pressure on natural resources with the potential to affect public health and wellbeing. The aim of this review was to identify and describe the potential health harms and benefits associated with dairy production and consumption. Electronic databases Medline, Embase, Scopus, Web of Science, PubMed, and Google Scholar were searched for published literature that investigated human health impacts of dairy production and consumption. Occupational hazards, environmental health impacts, ecosystem health impacts, foodborne hazards, and diet-related chronic diseases were identified as potential public health hazards. Some impacts, notably climate change, extend beyond directly exposed populations. Dairy production and consumption are also associated with important health benefits through the provision of nutrients and economic opportunities. As the global dairy sector increases production, exposure to a range of hazards must be weighed with these benefits. The review of impacts presented here can provide an input into decision making about optimal levels of dairy production and consumption, local land use, and identification and management of specific hazards from this sector. Future research should consider multiple exposure routes, socioeconomic implications, and environmental factors, particularly in regions heavily dependent on dairy farming.

Potential Roles of Innate Immune Chemokine and Cytokine Network on Lipopolysaccharide-Based Therapeutic Approach in Ovarian Cancer

Ovarian cancer (OC), the deadliest gynecological cancer, results in poor overall survival, urgently requiring a novel therapeutic approach. As cumulative exposures to endotoxins decreased OC risk epidemiologically, we evaluated if LPS, a Toll-like receptor 4 agonist known as active component of endotoxins, could increase survival in the murine peritoneal dissemination model of SKOV-3 OC cells. LPS significantly increased the mean survival time of more than 116 days compared with 63 days in the control. Furthermore, no tumor burden was present in three mice among eight LPS-treated mice. SKOV-3 cells were not responsive to LPS and showed unaltered chemokine signature. Rather than direct effects to OC cells, LPS was found to increase proinflammatory chemokines and cytokines, such as CXCL1, CXCL8, TNF, and IL-1B, in innate immune system. Taken together, LPS is likely to potentiate the cytotoxic-related innate immunogenicity via proinflammatory chemokines and cytokines, which attenuates the peritoneal dissemination of OC.

Cancer incidence in the Agricultural Health Study after 20 years of follow-up

PURPOSE

To evaluate cancer incidence in the Agricultural Health Study (AHS), a cohort of private pesticide applicators, their spouses, and commercial applicators, based on 12,420 cancers, adding 5,989 cancers, and 9 years of follow-up since last evaluation.

METHODS

We calculated age, year, sex, and race-adjusted standardized incidence ratios (SIR) and 95% confidence intervals (CI) for cancer sites in the AHS relative to the general population.

RESULTS

Overall AHS cancer incidence was lower than the general population (SIR_private = 0.91, CI 0.89-0.93; SIR_spouse = 0.89, CI 0.86-0.92; SIR_commercial = 0.83, CI 0.76-0.92), with notable deficits across applicators and spouses for oral cavity, pancreas, and lung cancers. Cancer excesses included prostate cancer, lip cancer, certain B-cell lymphomas (e.g., multiple myeloma), acute myeloid leukemia (AML), thyroid cancer, testicular cancer, and peritoneal cancer. The lung cancer deficit was strongest among applicators reporting potential exposure to endotoxin at study enrollment (tasks such as raising animals and handling stored grain).

CONCLUSIONS

Although an overall deficit in cancer was observed, there were notable exceptions, including newly observed excesses for AML, thyroid, testicular, and peritoneal cancers. Furthermore, endotoxin exposure may, in part, account for observed lung cancer incidence deficits. Cancer incidence patterns in the AHS suggest farm exposures' relevance to cancer etiology.

Lung cancer mortality and exposure to synthetic metalworking fluid and biocides: controlling for the healthy worker survivor effect

OBJECTIVES

Synthetic metalworking fluids (MWFs), widely used to cool and lubricate industrial machining and grinding operations, have been linked with increased risk of several cancers. Estimates of their relation with lung cancer, however, are inconsistent. Controlling for the healthy worker survivor effect, we examined the relations between lung cancer mortality and exposure to synthetic MWF, as well as to biocides added to water-based fluids to control microbial growth, in a cohort of autoworkers. Biocides served as a marker for endotoxin, which has reported antitumour effects, and were hypothesised to be the reason prior studies found reduced lung cancer risk associated with exposure to synthetic fluids.

METHODS

Using the parametric g-formula, we estimated risk ratios (RRs) comparing cumulative lung cancer mortality under no intervention with what would have occurred under hypothetical interventions reducing exposure to zero (ie, a ban) separately for two exposures: synthetic fluids and biocides. We also specified an intervention on synthetic MWF and biocides simultaneously to estimate joint effects.

RESULTS

Under a synthetic MWF ban, we observed decreased lung cancer mortality risk at age 86, RR=0.96 (0.91-1.01), but when we also intervened to ban biocides, the RR increased to 1.03 (0.95-1.11). A biocide-only ban increased lung cancer mortality (RR=1.07 (1.00-1.16)), with slightly larger RR in younger ages.

CONCLUSIONS

Findings suggest a modest positive association for synthetic MWF with lung cancer mortality, contrary to the negative associations reported in earlier studies. Biocide exposure, however, was inversely associated with risk of lung cancer mortality.

Association of Parkinson's disease with industry sectors: a French nationwide incidence study

In order to identify working environments at risk for Parkinson's disease (PD), we investigated the relation between the importance of industry sectors, used as a surrogate for occupational exposures, and PD incidence in French cantons. The number of incident PD cases (2010-2014) in 3689 cantons of metropolitan France was determined using drug claims from French National Health Insurance databases. The proportions of workers in 38 industry sectors in 2006 were calculated for each canton. Associations between the proportions of workers in industry sectors and PD age/sex-standardized incidence ratios were examined using incidence rate ratios (IRR) and 95% confidence intervals (CI) estimated with multilevel negative binomial regressions with a random intercept at the canton-level and adjusted for smoking, deprivation index, and density of neurologists. We then used two-step semi-Bayes hierarchical regression (HR) to include prior information about exposure to pesticides, metals, and solvents in each industry sector. We identified 112,625 incident cases. PD incidence was higher in areas characterized by high proportions of workers in "Agriculture, forestry and fishing" (IRR_HR = 1.042; CI 95% = 1.014-1.070; p-Trend_HR = 0.004), "Manufacture of textiles, wearing apparel, leather and related products" (IRR_HR = 1.024; CI 95% = 1.005-1.044; p-Trend_HR = 0.010), and "Manufacture of basic metals and fabricated metal products, except machinery and equipment" (IRR_HR = 1.024; CI 95% = 1.003-1.046; p-Trend_HR = 0.071). This nationwide study, based on a comprehensive analysis of industry sectors, shows significant associations between high proportions of workers in specific industry sectors (agriculture, metallurgy, textile) and PD incidence that may be targeted in further epidemiological studies to replicate and better understand these associations.

Occupational exposure to textile dust and lung cancer risk: Results from the ICARE Study

BACKGROUND

To investigate the association of lung cancer with occupational exposure to textile dust and specifically to cotton dust in the population-based case-control study ICARE.

METHODS

Lifelong occupational history of 2926 cases and 3555 controls was collected using standardized questionnaires, with specific questions for textile dust exposure. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated using unconditional logistic regression models controlling for confounding factors including smoking and asbestos exposure.

RESULTS

An inverse association between textile dust exposure and lung cancer was found among workers exposed ≥5% of their work time (OR = 0.80, 95%CI = 0.58-1.09), more pronounced for distant exposures (40+ years; up to a 56% reduced risk, statistically significant). The OR of lung cancer was significantly decreased among workers exposed to cotton fibers (OR = 0.70, 95%CI = 0.48-0.97).

CONCLUSIONS

Our results provide some evidence of a decreased risk of lung cancer associated with exposure to textile dust, particularly cotton.

Industrial hog farming is associated with altered circulating immunological markers

OBJECTIVES

The previously observed inverse association between hog farming and risk of lung cancer in the Agricultural Health Study (AHS) has been attributed to endotoxin exposure, the levels of which are particularly high in industrial hog confinement facilities. We conducted an investigation to explore the potential biological mechanisms underlying this association, as well as other immunological changes associated with hog farming.

METHODS

Serum immune marker levels were measured using a multiplexed bead-based assay in 61 active hog farmers and 61 controls matched on age, phlebotomy date and raising cattle. Both groups comprised non-smoking male AHS participants from Iowa. We compared natural log-transformed marker levels between hog farmers and controls using multivariate linear regression models.

RESULTS

Circulating levels of macrophage-derived chemokine (CCL22), a chemokine previously implicated in lung carcinogenesis, were reduced among hog farmers (17% decrease; 95% CI -28% to -4%), in particular for those with the largest operations (>6000 hogs: 26% decrease; 95% CI -39% to -10%; p_trend=0.002). We also found that hog farmers had elevated levels of other immune markers, including macrophage inflammatory protein-3 alpha (MIP-3A/CCL20; 111% increase, 95% CI 19% to 273%), basic fibroblast growth factor (FGF-2; 93% increase, 95% CI 10% to 240%) and soluble interleukin-4 receptor (12% increase, 95% CI 1% to 25%), with particularly strong associations for MIP-3A/CCL20 and FGF-2 in winter.

CONCLUSIONS

These results provide insights into potential immunomodulatory mechanisms through which endotoxin or other exposures associated with hog farming may influence lung cancer risk, and warrant further investigation with more detailed bioaerosol exposure assessment.

Cancer risks in a population-based study of 70,570 agricultural workers: results from the Canadian census health and Environment cohort (CanCHEC)

BACKGROUND

Agricultural workers may be exposed to potential carcinogens including pesticides, sensitizing agents and solar radiation. Previous studies indicate increased risks of hematopoietic cancers and decreased risks at other sites, possibly due to differences in lifestyle or risk behaviours. We present findings from CanCHEC (Canadian Census Health and Environment Cohort), the largest national population-based cohort of agricultural workers.

METHODS

Statistics Canada created the cohort using deterministic and probabilistic linkage of the 1991 Canadian Long Form Census to National Cancer Registry records for 1992-2010. Self-reported occupations were coded using the Standard Occupational Classification (1991) system. Analyses were restricted to employed persons aged 25-74 years at baseline (N = 2,051,315), with follow-up until December 31, 2010. Hazard ratios (HR) and 95% confidence intervals (CI) were modeled using Cox proportional hazards for all workers in agricultural occupations (n = 70,570; 70.8% male), stratified by sex, and adjusted for age at cohort entry, province of residence, and highest level of education.

RESULTS

A total of 9515 incident cancer cases (7295 in males) occurred in agricultural workers. Among men, increased risks were observed for non-Hodgkin lymphoma (HR = 1.10, 95% CI = 1.00-1.21), prostate (HR = 1.11, 95% CI = 1.06-1.16), melanoma (HR = 1.15, 95% CI = 1.02-1.31), and lip cancer (HR = 2.14, 95% CI = 1.70-2.70). Decreased risks in males were observed for lung, larynx, and liver cancers. Among female agricultural workers there was an increased risk of pancreatic cancer (HR = 1.36, 95% CI = 1.07-1.72). Increased risks of melanoma (HR = 1.79, 95% CI = 1.17-2.73), leukemia (HR = 2.01, 95% CI = 1.24-3.25) and multiple myeloma (HR = 2.25, 95% CI = 1.16-4.37) were observed in a subset of female crop farmers.

CONCLUSIONS

Exposure to pesticides may have contributed to increased risks of hematopoietic cancers, while increased risks of lip cancer and melanoma may be attributed to sun exposure. The array of decreased risks suggests reduced smoking and alcohol consumption in this occupational group compared to the general population.

Occupational exposure to endotoxins and lung cancer risk: results of the ICARE Study

Objectives

To investigate the role of occupational exposure to endotoxins in lung cancer in a French population-based case–control study (ICARE (Investigation of occupational and environmental causes of respiratory cancers)).

Methods

Detailed information was collected on the occupational history and smoking habits from 2926 patients with histologically confirmed lung cancer and 3555 matched controls. We evaluated each subject’s endotoxin exposure after cross referencing International Standard Classification of Occupations (ISCO) codes (for job tasks) and Nomenclature d'Activités Françaises (NAF) codes (for activity sectors). Endotoxin exposure levels were attributed to each work environment based on literature reports. ORs and 95% CIs were estimated using unconditional logistic regression models and controlled for main confounding factors.

Results

An inverse association between exposure to endotoxins and lung cancer was found (OR=0.80, 95% CI 0.66 to 0.95). Negative trends were shown with duration and cumulative exposure, and the risk was decreased decades after exposure cessation (all statistically significant). Lung cancer risk was particularly reduced among workers highly exposed (eg, in dairy, cattle, poultry, pig farms), but also in those weakly exposed (eg, in waste treatment). Statistically significant interactions were shown with smoking, and never/light smokers were more sensitive to an endotoxin effect than heavy smokers (eg, OR=0.14, 95% CI 0.06 to 0.32 and OR=0.80, 95% CI 0.45 to 1.40, respectively, for the quartiles with the highest cumulative exposure, compared with those never exposed). Pronounced inverse associations were shown with adenocarcinoma histological subtype (OR=0.37, 95% CI 0.25 to 0.55 in the highly exposed).

Conclusions

Our findings suggest that exposure to endotoxins, even at a low level, reduces the risk of lung cancer.

Revisiting cancer 15 years later: Exploring mortality among agricultural and non-agricultural workers in the Serrana Region of Rio de Janeiro

Background Agricultural production has expanded dramatically throughout Brazil. Previous research in the Serrana Region found that from 1979 to 1998, agricultural workers experienced high mortality rates from certain cancers compared to non-agricultural workers [Meyer et al. (2003): Environ Res 93:264-271].

METHODS

New data were obtained for 1999-2013 and Mortality Odds Ratios (MORs) were utilized to compare cancer and other mortality between male agricultural workers in the Serrana Region and non-agricultural workers in the Serrana Region, Rio de Janeiro, and Porto Alegre, and to compare mortality odds to previous decades.

RESULTS

Respectively, compared to aforementioned reference-groups, agricultural workers experienced highest MORs for stomach (1.55 [95%CI: 1.13-2.12], 2.30 [95%CI: 1.72-3.08], 2.28 [95%CI: 1.69-3.08]) and esophageal cancers (95%CI: 1.93 [1.38-2.7], 1.93 [95%CI: 1.38-2.71], 3.12 [95%CI: 2.30-4.24]), greater than reported in previous decades. Agricultural workers experienced higher mortality for external-causes, respiratory, and cardiovascular problems compared to urban reference-groups.

CONCLUSION

Agricultural workers may be at increasing risk for cancer and other mortality. Efforts are needed to investigate distinct risk-factors among this group. Am. J. Ind. Med. 60:77-86, 2017. © 2016 Wiley Periodicals, Inc.

Textile industry and occupational cancer

BACKGROUND AND SUMMARY

Thousands of workers are engaged in textile industry worldwide. Textile industry involves the use of different kinds of dyes which are known to possess carcinogenic properties. Solvents used in these industries are also associated with different health related hazards including cancer. In previous studies on textile and iron industries, the authors have reported genotoxicity among them and observed occurrence of cancer deaths among textile industry workers. Thus, an attempt has been made to compile the studies on the prevalence of different types of cancers among textile industry workers.

LITERATURE SEARCH

A wide literature search has been done for compiling the present paper. Papers on cancer occurrence among textile industry workers have been taken from 1976 to 2015. A variety of textile dyes and solvents, many of them being carcinogenic, are being used worldwide in the textile industry. The textile industry workers are therefore, in continuous exposure to these dyes, solvents, fibre dusts and various other toxic chemicals. The present study evaluates the potential of different chemicals and physical factors to be carcinogenic agents among occupationally exposed workers by going through various available reports and researches. Papers were collected using different databases and a number of studies report the association of textile industry and different types of cancer including lung, bladder, colorectal and breast cancer. After going through the available reports, it can be concluded that workers under varied job categories in textile industries are at a higher risk of developing cancer as various chemicals used in the textile industry are toxic and can act as potential health risk in inducing cancer among them. Assessing the cancer risk at different job levels in textile industries may be found useful in assessing the overall risk to the workers and formulating the future cancer preventive strategies.

Differential innate immune cell signatures and effects regulated by toll-like receptor 4 during murine lung tumor promotion

Tumor promotion is an early and critical stage during lung adenocarcinoma (ADC). We previously demonstrated that Tlr4 mutant mice were more susceptible to butylated hydroxytoluene (BHT)-induced pulmonary inflammation and tumor promotion in comparison to Tlr4-sufficient mice. Our study objective was to elucidate the underlying differences in Tlr4 mutant mice in innate immune cell populations, their functional responses, and the influence of these cellular differences on ADC progenitor (type II) cells following BHT-treatment. BALB (Tlr4-sufficient) and C.C3-Tlr4(Lps-d)/J (BALB(Lpsd); Tlr4 mutant) mice were treated with BHT (promoter) followed by bronchoalveolar lavage (BAL) and flow cytometry processing on the lungs. ELISAs, Club cell enrichment, macrophage function, and RNA isolation were also performed. Bone marrow-derived macrophages (BMDM) co-cultured with a type II cell line were used for wound healing assays. Innate immune cells significantly increased in whole lung in BHT-treated BALB(Lpsd) mice compared to BALB mice. BHT-treated BALB(Lpsd) mice demonstrated enhanced macrophage functionality, increased epithelial wound closure via BMDMs, and increased Club cell number in BALB(Lpsd) mice, all compared to BALB BHT-treated mice. Cytokine/chemokine (Kc, Mcp1) and growth factor (Igf1) levels also significantly differed among the strains and within macrophages, gene expression, and cell surface markers collectively demonstrated a more plastic phenotype in BALB(Lpsd) mice. Therefore, these correlative studies suggest that distinct innate immune cell populations are associated with the differences observed in the Tlr4-mutant model. Future studies will investigate the macrophage origins and the utility of the pathways identified herein as indicators of immune system deficiencies and lung tumorigenesis.

The natural immunity to evolutionary atavistic endotoxin for human cancer

We propose a new theory of the immunological control of cancer corresponding to the hypothesis that the specific natural immunity to evolutionary atavistic endotoxin has a potential role in human cancer prevention. The results of our studies have shown that IgMNAE, i.e. endogenous or spontaneous IgM class antibodies to enterobacterial lipopolysaccharide molecules (lipid A), control the immune mechanisms responsible for the internal medium stability not only against the damaging impact of the carcinogenic factors, but also against the malignant transformation of its own degenerated cells. Among people who in 1979 and 1982 had IgMNAE in their blood serum, after 15-30years fell ill with cancer 10%, versus 15% among people who had no IgMNAE (p<0.05). Therefore, it is possible to maintain that the stimulation of IgMNAE synthesis would help in the destruction and elimination of damaged somatic cells or prevent their mechanisms from the formation of invasiveness, metastatic and other properties of their parasitism. In the mechanism of the natural immunity to endotoxin it is possible to see the formation of the respective evolutionary protective reactions which protect the damaged cells from acquiring resistance to damaging factors and thus from becoming an independent new parasitic population. Thereby the presented theory of the immunological control of cancer has a causal connection with our evolutionary resistance theory of the origin of cancer. Collectively, these data suggest that activation of natural immunity to endotoxin and production of vaccines against evolutionary atavistic endotoxin or gram-negative bacterial endotoxin can be helpful when applied in cancer prophylaxis for persons with a low level of natural immunity to endotoxin and perhaps in creating immunotherapeutic methods for stopping the endogenous parasitism of tumour cells by binding IgMNAE to atavistic endotoxin in cancer patients.

Indicators of microbial-rich environments and the development of papillary thyroid cancer in the California Teachers Study

BACKGROUND

Little epidemiologic research has focused on the role of immune function in papillary thyroid cancer risk despite scattered observations suggesting it may be important (e.g., hygiene hypothesis). Here we investigate papillary thyroid cancer risk associated with self-reported living environments across the lifespan reflecting immunologically relevant exposures to microbial-rich environments.

METHODS

Among 61,803 eligible participants in the California Teachers Study cohort, 100 were diagnosed with invasive papillary thyroid cancer between 2005 and 2012. Multivariate Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Living in a rural area during early childhood was associated with significantly reduced risk of developing papillary thyroid cancer as an adult (HR=0.51, 95% CI: 0.28-0.94). Specifically, reduced risks were observed for living within a half mile of hoofed animals (HR=0.47, 95% CI: 0.26-0.84), as was having an indoor dog or cat (HR=0.51, 95% CI: 0.32-0.80). Neither sharing a bedroom or living in a rented home as a child nor attending daycare or kindergarten was associated with reduced risk.

CONCLUSIONS

Early childhood exposures to hoofed animals or indoor furry pets were associated with reduced risk of subsequently developing papillary thyroid cancer.

IMPACT

Our findings point to immunologically relevant, early-life exposures to microbial-rich environments as potentially important in reducing thyroid cancer risk, consistent with the hygiene hypothesis and suggesting that certain, possibly animal-derived, microbial exposures may be important to immune calibration or priming.

Lack of a protective effect of cotton dust on risk of lung cancer: evidence from two population-based case-control studies

BACKGROUND

Lung cancer is the leading cause of cancer death in North America. Exposure to cotton dust has previously been reported to decrease the risk of lung cancer.

METHODS

We used data from two large case-control studies conducted in Montreal from 1979-1986 (Study 1) and 1996-2002 (Study 2) respectively, to examine the association between occupational exposure to cotton dust and risk of lung cancer. Cases were diagnosed with incident histologically-confirmed lung cancer (857 in Study 1, 1203 in Study 2). Population controls were randomly selected from electoral lists and frequency-matched to cases by age and sex (533 in Study 1, 1513 in Study 2). Interviews for the two studies used a virtually identical questionnaire to obtain lifetime occupational and smoking history, and several lifestyle covariates. Each participant's lifetime occupational history was reviewed by experts to assess exposure to a number of occupational agents, including cotton dust. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by unconditional logistic regression, adjusting for potential confounders.

RESULTS

The lifetime prevalence of exposure to cotton dust was approximately 10%-15% in both studies combined, with some variation by study and by sex. Overall there was no decreased risk of lung cancer among subjects exposed to cotton dust. Rather, among all subjects there was a suggestion of slightly increased risk associated with any lifetime exposure to cotton dust (OR = 1.2, 95% CI: 1.0-1.5). This risk appeared to be concentrated among cases of adenocarcinoma (OR = 1.6, 95% CI: 1.2-2.2), and among moderate and heavy smokers (OR = 1.3, 95% CI: 1.0-1.7). There was no association when restricting to cases of either squamous cell or small cell cancer, or among never smokers and light smokers. An analogous examination of subjects exposed to wool dust revealed neither increased nor decreased risks of lung cancer.

CONCLUSIONS

There was no evidence that cotton dust exposure decreased risks of lung cancer.

A comprehensive review of levels and determinants of personal exposure to dust and endotoxin in livestock farming

The respiratory health effects of livestock farming have been on debate for more than three decades. Endotoxin-contaminated organic dusts are considered as the most important respiratory hazards within livestock environments. A comprehensive review of the knowledge from studies assessing the exposure status of livestock farmers is still to be published. The present study reviews research published within the last 30 years on personal exposure of livestock farmers to organic dust and endotoxin, focusing on studies on pig, poultry and cattle farmers. Applied measurement methods and reported levels of personal exposure for the total, inhalable and respirable fractions are summarized and discussed, with emphasis on the intensity of exposure and the size and distribution of the reported exposure variability. In addition, available evidence on potential determinants of personal exposure to dust and endotoxin among these farmers are documented and discussed, taking results from exposure determinant studies using stationary sampling approaches into consideration. Research needs are addressed from an epidemiological and industrial hygiene perspective. Published studies have been heterogeneous in design, and applied methodologies and results were frequently inadequately reported. Despite these limitations and the presence of an enormous variability in personal exposure to dust and endotoxin, no clear downward trends in exposure with time were observed, suggesting that working environments within stables remains largely uncontrolled. Exposure control and prevention strategies for livestock farmers are urgently required. These should focus on the development of novel and improved methods of controlling dust and endotoxin exposure within stables based on the currently available knowledge on determinants of exposure.

The Biomarkers of Exposure and Effect in Agriculture (BEEA) Study: Rationale, Design, Methods, and Participant Characteristics

Agricultural exposures including pesticides, endotoxin, and allergens have been associated with risk of various cancers and other chronic diseases, although the biological mechanisms underlying these associations are generally unclear. To facilitate future molecular epidemiologic investigations, in 2010 the study of Biomarkers of Exposure and Effect in Agriculture (BEEA) was initiated within the Agricultural Health Study, a large prospective cohort in Iowa and North Carolina. Here the design and methodology of BEEA are described and preliminary frequencies for participant characteristics and current agricultural exposures are reported. At least 1,600 male farmers over 50 years of age will be enrolled in the BEEA study. During a home visit, participants are asked to complete a detailed interview about recent agricultural exposures and provide samples of blood, urine, and (since 2013) house dust. As of mid-September 2014, in total, 1,233 participants have enrolled. Most of these participants (83%) were still farming at the time of interview. Among those still farming, the most commonly reported crops were corn (81%) and soybeans (74%), and the most frequently noted animals were beef cattle (35%) and hogs (13%). There were 861 (70%) participants who reported occupational pesticide use in the 12 months prior to interview; among these participants, the most frequently noted herbicides were glyphosate (83%) and 2,4-D (72%), and most commonly reported insecticides were malathion (21%), cyfluthrin (13%), and permethrin (12%). Molecular epidemiologic investigations within BEEA have the potential to yield important new insights into the biological mechanisms through which these or other agricultural exposures influence disease risk.

The biography of the immune system and the control of cancer: from St Peregrine to contemporary vaccination strategies

BACKGROUND

The historical basis and contemporary evidence for the use of immune strategies for prevention of malignancies are reviewed. Emphasis is focussed on the Febrile Infections and Melanoma (FEBIM) study on melanoma and on malignancies that seem to be related to an overexpression of human endogenous retrovirus K (HERV-K).

DISCUSSION

It is claimed that, as a result of recent observational studies, measures for prevention of some malignancies such as melanoma and certain forms of leukaemia are already at hand: vaccination with Bacille Calmette-Guérin (BCG) of new-borns and vaccination with the yellow fever 17D (YFV) vaccine of adults. While the evidence of their benefit for prevention of malignancies requires substantiation, the observations that vaccinations with BCG and/or vaccinia early in life improved the outcome of patients after surgical therapy of melanoma are of practical relevance as the survival advantage conferred by prior vaccination is greater than any contemporary adjuvant therapy.

SUMMARY

The reviewed findings open a debate as to whether controlled vaccination studies should be conducted in patients and/or regions for whom/where they are needed most urgently. A study proposal is made and discussed. If protection is confirmed, the development of novel recombinant vaccines with wider ranges of protection based, most likely, on BCG, YFV or vaccinia, could be attempted.

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.

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.

Urinary concentrations of metabolites of pyrethroid insecticides in textile workers, Eastern China

Pyrethroid insecticides have been applied in the production of cotton, wool and textile. In order to examine whether textile workers are exposed to pyrethroid insecticides, we recruited 50 textile workers in two textile plants in Eastern China. Their urine samples were collected for the measurement of pyrethroid metabolites: cis- and trans-isomers of 2,2-dichlorovinyl-2,2-dimethylcyclopropane-1-carboxylic acid (cis-Cl2CA and trans-Cl2CA) and 3-phenoxybenzoic acid (3-PBA). Our results showed that textile workers were exposed to high levels of pyrethroid insecticides. cis-Cl2CA and 3-PBA were dominant metabolites with concentrations of 0.17-261μg/L, while concentrations of trans-Cl2CA were in the range of 0.26-11μg/L. Levels of three metabolites were in a descending order: cis-Cl2CA, 3-PBA, and trans-Cl2CA. Levels of the metabolites were associated with ages and job responsibilities of textile workers. Sewing workers, cutting workers, machine operators, reorganizers, and older workers were more likely in contact with pyrethroid insecticides in the textile production. trans- to cis-Cl2CA ratios might indicate that exposure of textile workers was via dermal absorption and inhalation.

Cotton dust, endotoxin and cancer mortality among the Shanghai textile workers cohort: a 30-year analysis

BACKGROUND

Although occupational exposure to cotton dust and endotoxin is associated with adverse respiratory health, associations with cancer are unclear. We investigated cancer mortality in relation to cotton dust and endotoxin exposure in the Shanghai textile workers cohort.

METHODS

We followed 444 cotton textile and a reference group of 467 unexposed silk workers for 30 years (26 777 person-years). HRs for all cancers combined (with and without lung cancer) and gastrointestinal cancer were estimated in Cox regression models as functions of cotton textile work and categories of cumulative exposure (low, medium, high), after adjustment for covariates including pack-years smoked. Different lag years accounted for disease latency.

RESULTS

Risks of mortality from gastrointestinal cancers and all cancers combined, with the exclusion of lung cancer, were increased in cotton workers relative to silk workers. When stratified by category of cumulative cotton exposure, in general, risks were greatest for 20-year lagged medium exposure (all cancers HR=2.7 (95% CI 1.4 to 5.2); cancer excluding lung cancer HR=3.4 (1.7-7.0); gastrointestinal cancer HR=4.1 (1.8-9.7)). With the exclusion of lung cancer, risks of cancer were more pronounced. When stratified by category of cumulative endotoxin exposure, consistent associations were not observed for all cancers combined. However, excluding lung cancer, medium endotoxin exposure was associated with all cancers and gastrointestinal cancer in almost all lag models.

CONCLUSIONS

Cotton dust may be associated with cancer mortality, especially gastrointestinal cancer, and endotoxin may play a causative role. Findings also indirectly support a protective effect of endotoxin on lung cancer.

Occupational exposure and thoracic malignancies, is there a relationship?

OBJECTIVES

The aim of this study was to evaluate the effect of occupational exposure in the occurrence of lung cancer.

METHOD

Three-hundred lung cancer cases diagnosed between September 1, 1999, and September 31, 2007, and 300 healthy controls were enrolled in this case-control study. Life-long occupational history, gender, age, exposure to asbestos, comorbidities, and smoking status were collected.

RESULTS

The mean age of the 300 lung cancer cases was 60.3 ± 9.9 year (91.7% male and 8.3% female), and the mean age of healthy control group was 60.4 ± 10.5 year (95.0% male and 5.0% female). The most frequent histological types were squamous (172, 57.3%), adeno (69, 23.1%), and small cell (37, 12.3%). There was an increased risk of lung cancer occurrence among agriculture workers (OR=1.89, 95% Cl=1.17-2.98) (p=0.009). Inorganic dust exposure (OR=1.81, 95% Cl=1.0-3.25) (p=0.049) and organic dust exposure (OR=1.89, 95% Cl=1.0-3.59) (p=0.05) were found to be related with high frequency of having lung cancer.

CONCLUSION

Workers who had occupational exposure to organic and inorganic dust, especially in the agricultural field, had higher risk of lung cancer occurrence when compared with office workers.

Exposure to inhalable dust and endotoxin among Danish pig farmers affected by work tasks and stable characteristics

OBJECTIVE

To identify working tasks and stable characteristics that determine intensity and variability of personal exposure to dust and endotoxin among pig farmers.

METHODS

Three hundred fifty-four personal full-shift measurements were performed in 231 farmers employed in 53 Danish pig farms. Filters were gravimetrically analysed for inhalable dust and for endotoxin by the Limulus amebocyte lysate assay. Information on working tasks and stable characteristics were collected using self-reported activity diaries and walk-through surveys performed in conjunction with the measurements. Associations between log-transformed dust and endotoxin exposure and working tasks and stable characteristics were examined using linear mixed-effects analysis. In these models, worker and farm identity were treated as random effects and working tasks and stable characteristics as fixed effects. Both separate and combined models for tasks and stable characteristics were elaborated.

RESULTS

Inhalable dust concentrations ranged between 0.1 and 48 mg m(-3) and endotoxin concentrations varied between 9.2 and 370,000 EU m(-3). Field work activities played a dominant role on the exposure variability. Indoor working tasks with intense animal activity or handling of feed materials increased exposure concentrations, whereas engagement in field work was associated with lower exposure concentrations. High-pressure water cleaning increased endotoxin exposure but did not affect exposure to inhalable dust. Stable characteristics related to feeding practices and type of ventilation were determinants of exposure to inhalable dust. For endotoxin, the most important determinants were use of dry feed and slatted floor coverage. Feeding practices solely explained all between-farms variability in exposure to inhalable dust and endotoxin.

CONCLUSIONS

These findings suggest feeding systems, flooring and ventilation to be potential areas where improved methods can reduce exposure to dust and endotoxin among pig farmers. Further, they highlight particular tasks involving feeding and intense animal handling as sources of very high levels of exposure. The pig farming industry is encouraged to focus on exposure reduction. Use of respirators during performance of working tasks where levels of exposure are particularly high ought to be considered until adequate hygienic solutions have been established.

Evidence of a paradoxical relationship between endotoxin and lung cancer after accounting for left truncation in a study of Chinese female textile workers

INTRODUCTION

Occupational exposure to endotoxin, found in Gram-negative bacteria in organic material, has been associated predominantly with a reduced risk of lung cancer among workers. An inverse exposure-response gradient among women textile workers in Shanghai, China, has been reported previously. In this case-cohort study, we investigated the influence of left truncation, which can itself induce a downward trend, on the observed association.

METHODS

Subjects were enrolled between 1989 and 1991 and followed until 1998. The data were left-truncated as all subjects were hired before baseline. An analysis was performed with 3038 subcohort members and 602 cases of incident lung cancer. To evaluate left truncation, we compared lung cancer rates in those hired longer ago with those hired more recently among unexposed subjects. Cox proportional hazards modelling was used to estimate incident rate ratios (IRRs) and 95% CIs.

RESULTS

Among those who were never exposed to workplace endotoxin, we compared lung cancer rates in those hired >35 years before enrolment with workers hired ≤35 years before enrolment and observed a reduced risk in the former group, IRR=0.74, 95% CI (0.51 to 1.07). After accounting for this downward bias from left truncation, the reduced risk associated with endotoxin remained among those hired ≤50 years before enrolment. In contrast, there was suggestion of an increased risk of lung cancer among those hired >50 years ago.

CONCLUSIONS

After examination of left truncation bias, an inverse dose-response between endotoxin and lung cancer remained for all subjects except those hired longest ago.

Immunological and inflammatory responses to organic dust in agriculture

PURPOSE OF REVIEW

Agriculture represents a major industry worldwide, and despite protection against the development of IgE-mediated diseases, chronic exposure to agriculture-related organic dusts is associated with an increased risk of developing respiratory disease. This article will review the literature regarding new knowledge of important etiologic agents in the dusts and focus on the immunologic responses following acute and repetitive organic dust exposures.

RECENT FINDINGS

Although endotoxin remains important, there is an emerging role of nonendotoxin components such as peptidoglycans from Gram-positive bacteria. Pattern recognition receptors including Toll-like receptor 4 (TLR4), TLR2 and intracellular nucleotide oligomerization domain-like receptors are partially responsible for mediating the inflammatory consequences. Repeated organic dust exposures modulate innate and adaptive immune function with a resultant adaptation-like response. However, repetitive exposures cause lung parenchymal inflammation, chronic disease, and lung function decline over time.

SUMMARY

The immunological consequences of organic dust exposure in the farming industry are likely explained by the diversity of microbial motifs in dust that can elicit differing innate immune receptor signaling pathways. Whereas initial activation results in a robust inflammatory response, repetitive dust exposures modulate immunity. This can result in low-grade, chronic inflammation, and/or protection against allergic disease.

Occupational exposure to organic dust increases lung cancer risk in the general population

BACKGROUND

Organic dust is a complex mixture of particulate matter from microbial, plant or animal origin. Occupations with exposure to animal products have been associated with an increased lung cancer risk, while exposure to microbial components (eg, endotoxin) has been associated with a decreased risk. To date there has not been a comprehensive evaluation of the possible association between occupational organic dust exposure (and its specific constituents) and lung cancer risk in the general population.

METHODS

The SYNERGY project has pooled information on lifetime working and smoking from 13 300 lung cancer cases and 16 273 controls from 11 case-control studies conducted in Europe and Canada. A newly developed general population job-exposure matrix (assigning no, low or high exposure to organic dust, endotoxin, and contact with animals or fresh animal products) was applied to determine level of exposure. ORs for lung cancer were estimated by logistic regression, adjusted for age, sex, study, cigarette pack-years, time since quitting smoking, and ever employment in occupations with established lung cancer risk.

RESULTS

Occupational organic dust exposure was associated with increased lung cancer risk. The second to the fourth quartile of cumulative exposure showed significant risk estimates ranging from 1.12 to 1.24 in a dose-dependent manner (p<0.001). This association remained in the highest quartile after restricting analyses to subjects without chronic obstructive pulmonary disease or asthma. No association was observed between lung cancer and exposure to endotoxin or contact with animals or animal products.

CONCLUSION

Occupational exposure to organic dust was associated with increased lung cancer risk in this large pooled case-control study.

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.

Effects of occupation on risks of avoidable cancers in the Nordic countries

Knowledge of cancer risk according to occupational affiliation is an essential part of formatting preventive actions aimed at the adult population. Herein, data on 10 major cancer sites amenable by life style exposures from the Nordic Occupational Cancer Study (NOCCA) are presented. All subjects aged 30-64 years participating in one or more national censuses in Denmark, Finland, Iceland, Norway, or Sweden between 1960 and 1990 were included in the cohort and followed up for cancer from inclusion until 2003/2005 via a linkage with the national cancer registries, and standardised incidence ratios (SIRs) were computed. Variation in risk across occupations was generally larger in men than in women. In men, the most consistent cluster with high risk of numerous cancer types included waiters, cooks and stewards, beverage workers, seamen, and chimney sweeps. Two clusters of occupations with generally low cancer risks were seen in both men and women. The first one comprised farmers, gardeners, and forestry workers, the second one included groups with high education, specifically those in health and pedagogical work. Although cancer risk varies by occupation, only a smaller part of the variation can be attributed to occupational exposures in the strict sense. Preventive measures at the work place are important to avoid established and new occupational health hazards. This study also indicates that the work place in addition should be seen as a useful arena for reaching groups of adults with more or less similar habits and attitudes for general health promotion.