Animal production and wheeze in the Agricultural Health Study: interactions with atopy, asthma, and smoking

Respiratory Findings in Herd Dairy Farmworkers from the Nile Delta Region

BACKGROUND

Dairy farmworkers are exposed to a variety of respiratory hazards, including organic and inorganic dust, allergens, disinfectants, and gases emitted by cows and their wastes resulting in a range of adverse health effects. In Egypt, large herd dairy farms (>1000 cattle) are growing in both size and number and thereby more workers are employed. However, there is a lack of studies on the respiratory health status of these workers. Accordingly, the present study aimed to determine the prevalence of respiratory problems, assess ventilatory functions, and highlight the predictors of abnormal spirometry patterns among Egyptian dairy farmworkers.

METHODS

A cross-sectional study was carried out on 282 male workers, of whom 141 were dairy farmworkers and the other 141, not involved in livestock handling, were enrolled as controls. Full history, clinical examination, and ventilatory function measurements were done for both groups.

RESULTS

Dairy farmworkers had a significantly higher prevalence of respiratory symptoms (throat irritation and/or sore throat, cough, sputum production, and difficulty breathing) than controls as well as bronchitis, wheezes on chest auscultation, and obstructive ventilatory patterns. Older age (>37 years), longer smoking duration (>10 years), and longer working duration (>4 years) were independent predictors of abnormal spirometry patterns, particularly obstructive patterns, in dairy farmworkers.

CONCLUSIONS

Large herd dairy farms, despite being open and naturally ventilated, are hazardous to workers' respiratory health. Hence, the provision of personal protective equipment, periodic spirometry examinations as well as mandatory breaks and days off, are highly urged.

Personal protective equipment use during industrial hog operation work activities and acute lung function changes in a prospective worker cohort, North Carolina 2014-2015

INTRODUCTION

Occupational activities related to industrial hog operation (IHO) worker lung function are not well defined. Therefore, we aimed to identify IHO work activities associated with diminished respiratory function and the effectiveness, if any, of personal protective equipment (PPE) use on IHOs.

METHODS

From 2014 to 2015, 103 IHO workers were enrolled and followed for 16 weeks. At each biweekly visit, work activities and PPE use were self-reported via questionnaire and lung function measurements were collected via spirometry. Generalized linear and linear fixed-effects models were fitted to cross-sectional and longitudinal data.

RESULTS

Increasing years worked on an IHO were associated with diminished lung function, but baseline and longitudinal work activities were largely inconsistent in direction and magnitude. Unexpectedly, a -0.3 L (95% confidence interval: -0.6, -0.04) difference in forced expiratory volume in the first second (FEV₁ ) was estimated when workers wore PPE consistently (≥80% of the time at work) versus those weeks they did not. In post-hoc analyses, we found that coveralls and facemasks were worn less consistently when workers experienced worse barn conditions and had more contact with pigs, but coveralls were worn more consistently as cleaning activities increased.

CONCLUSIONS

Similar to past studies, baseline estimates were likely obscured by healthy worker effect bias, but showed decrements in worker lung function as years of work increased. A challenge to disentangling the effect of work activities on lung function was the discovery that IHO workers used PPE differently according to the work task. These data suggest that interventions may be targeted toward improving barn conditions so that workers can consistently utilize IHO-provided PPE.

Atrazine Inhalation Causes Neuroinflammation, Apoptosis and Accelerating Brain Aging

BACKGROUND

exposure to environmental contaminants has been linked to an increased risk of neurological diseases and poor outcomes. Chemical name of Atrazine (ATR) is 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine, and it is the most commonly used broad-spectrum herbicide in agricultural crops. Several studies have demonstrated that ATR has the potential to be harmful to the brain's neuronal circuits. Until today nobody has explored the effect of ATR inhalation on young and aged mice.

METHODS

young and aged mice were subject to 25 mg of ATR in a vehicle made with saline and 10% of Dimethyl sulfoxide (DMSO) every day for 28 days. At the end of experiment different behavioral test were made and brain was collected.

RESULTS

exposure to ATR induced the same response in terms of behavioral alterations and motor and memory impairment in mice but in aged group was more marked. Additionally, in both young and aged mice ATR inhalations induced oxidative stress with impairment in physiological antioxidant response, lipid peroxidation, nuclear factor kappa-light-chain-enhancer of activated B cells (nf-κb) pathways activation with consequences of pro-inflammatory cytokines release and apoptosis. However, the older group was shown to be more sensitive to ATR inhalation.

CONCLUSIONS

our results showed that aged mice were more susceptible compared to young mice to air pollutants exposure, put in place a minor physiologically response was seen when exposed to it.

The use of personal protective equipment during common industrial hog operation work activities and acute lung function changes in a prospective worker cohort, North Carolina, USA

Introduction

As occupational activities related to acute industrial hog operation (IHO) worker lung function are not well defined, we aimed to identify IHO work activities associated with diminished respiratory function and the effectiveness, if any, of personal protective equipment (PPE) on IHOs.

Methods

From 2014-2015, 103 IHO workers were enrolled and followed for 16 weeks. At each bi-weekly visit, lung function measurements were collected via spirometry and work activities and PPE use were self-reported via questionnaire. Generalized linear and linear fixed-effects models were fitted to cross-sectional and longitudinal data.

Results

At baseline, increasing years worked on an IHO were associated with diminished lung function, but other activities were less consistent in direction and magnitude. In longitudinal models, only reports of working in feeding/finisher barns, showed a consistent association. However, a -0.3 L (95% confidence interval: -0.6, -0.04) difference in FEV ₁ was estimated when workers wore PPE consistently versus those weeks they did not. In post-hoc analyses, we found that coveralls and facemasks were worn less consistently when workers experienced worse barn conditions and had more contact with pigs, but coveralls were worn more consistently as cleaning activities increased.

Conclusions

Similar to past studies, baseline estimates were likely obscured by healthy worker bias. Also making it challenging to disentangle the effect of work activities on lung function was the discovery that IHO workers used PPE differently according to work task. These data suggest that interventions may be targeted toward improving barn conditions so that workers can consistently utilize IHO-provided PPE.

KEY MESSAGES

What is already known about this subject?: Working on industrial hog operations may be deleterious to long- and short-term respiratory health due to airborne bacteria, endotoxin, hazardous gases, dust, and dander in barns. In efficacy studies PPE has been shown to be protective, but studies have shown that PPE utilization among hog workers has historically been sub-optimal.What are the new findings?: As barn conditions worsened and contact with pigs increased, workers in this cohort reported wearing coveralls and face masks less often; however, they reported increased PPE use as they conducted more cleaning activities at work. During weeks when workers wore PPE their lung function declined, a possible cause being the improper use of the equipment leading to a false sense of protection or re-exposure to hazardous contaminants.How might this impact on policy or clinical practice in the foreseeable future?: Given COVID-19, the H1N1 "swine flu" pandemic, our knowledge of antimicrobial resistant pathogens, and increasing awareness about how food systems are linked to the spread of emerging infectious diseases, occupational health intervention research and workplace policies may focus on creating barn environments that are more conducive to PPE use which could help protect workers and consequently the community.

Respiratory diseases and allergy in farmers working with livestock: a EAACI position paper

Farmers constitute a large professional group worldwide. In developed countries farms tend to become larger, with a concentration of farm operations. Animal farming has been associated with negative respiratory effects such as work-related asthma and rhinitis. However, being born and raised or working on a farm reduces the risk of atopic asthma and rhinitis later in life. A risk of chronic bronchitis and bronchial obstruction/COPD has been reported in confinement buildings and livestock farmers. This position paper reviews the literature linking exposure information to intensive animal farming and the risk of work-related respiratory diseases and focuses on prevention. Animal farming is associated with exposure to organic dust containing allergens and microbial matter including alive microorganisms and viruses, endotoxins and other factors like irritant gases such as ammonia and disinfectants. These exposures have been identified as specific agents/risk factors of asthma, rhinitis, chronic bronchitis, COPD and reduced FEV₁. Published studies on dust and endotoxin exposure in livestock farmers do not show a downward trend in exposure over the last 30 years, suggesting that the workforce in these industries is still overexposed and at risk of developing respiratory disease. In cases of occupational asthma and rhinitis, avoidance of further exposure to causal agents is recommended, but it may not be obtainable in agriculture, mainly due to socio-economic considerations. Hence, there is an urgent need for focus on farming exposure in order to protect farmers and others at work in these and related industries from developing respiratory diseases and allergy.

Respiratory health disorders associated with occupational exposure to bioaerosols among workers in poultry breeding farms

Working in poultry farms revealed the exposure to chemical and biological emissions (bioaerosols) that might be related to respiratory diseases in the workers and an increased loss in lung function. The current study aimed to determine the respiratory health status among poultry farm workers and to monitor the biological and the environmental conditions at ten poultry farms in Egypt. It reported that the total dust, ammonia (NH₃), and carbon dioxide (CO₂) concentrations in the studied poultry farms did not exceed the permissible exposure limits except farm V where NH₃ was slightly exceeded the recommended levels. 35.7% of the poultry farm workers had positive nose and throat culture (bacterial and fungal). The poultry farm workers had higher prevalence of cough, wheeze, and shortness of breath with lower mean values of spirometric measurements than the controls (P < 0.05). Also, the positive culture poultry farm workers had significantly higher respiratory manifestations and lower spirometry values than negative culture ones (P < 0.05). Therefore, intervention programs for reducing the exposure are amendatory point for the health and safety of poultry farm workers.

Chronic respiratory symptoms and pulmonary function status in Ethiopian agricultural workers: a comparative study

BACKGROUND

Work-related respiratory disorders are major contributors to the global burden of respiratory diseases. Agricultural workers are exposed to a number of dusts, which may contribute to the development of respiratory disorders. However, the knowledge about the prevalence of respiratory symptoms and pulmonary function status in African farmers was limited. This study was conducted to assess the prevalence of chronic respiratory symptoms and pulmonary function status of Ethiopian farmers exposed to farming activities.

METHODS

A community based comparative cross sectional study was conducted among 288 agricultural workers (farmers) aged 18 to 65 years and 288 control subjects (non-agricultural workers). Data were collected by interviewer administered structured questionnaires adopted from British Medical Research Council respiratory questionnaire and American Thoracic Society Division of Lung Diseases questionnaire. Moreover, all study participants underwent spirometry.

RESULTS

The prevalence of chronic respiratory symptoms was higher in farmers than in controls, with significant difference for cough (20.5% vs. 9.0%, p = 0.001) and phlegm (19.1% vs. 9.0%, p = 0.001). Chronic respiratory symptoms among farmers were significantly associated with duration of agricultural exposure (p = 0.014). The mean values of all spirometric parameters were lower in farmers than in controls with significant difference for FVC, FEV1, FEF25%, FEF50%, FEF25-75% and PEFR. Moreover, the mean values of all spirometric parameters of farmers have found to be decreased with increased duration of workplace exposure. Lung function test results also showed a higher prevalence of obstructive (15.6% vs. 10.8%, p = 0.085) and restrictive type (12.8% vs. 3.1%, p <  0.001) of pulmonary function impairment in farmers than in controls. However, the difference was not significant for obstructive type of impairment.

CONCLUSION

This study indicated that farmers are at high risk for the development of chronic respiratory symptoms and reduced pulmonary function indices. Hence, a comprehensive occupational safety practices are important to maintain the respiratory health of farmers.

Animal farming and the risk of lymphohaematopoietic cancers: a meta-analysis of three cohort studies within the AGRICOH consortium

OBJECTIVE

Animal farming entails a variety of potential exposures, including infectious agents, endotoxins and pesticides, which may play a role in the aetiology of lymphohaematopoietic cancers (LHCs). The aim of this study was to assess whether farming specific animal species is associated with the risk of overall LHC or its subtypes.

METHODS

Data from three prospective cohort studies in the USA, France and Norway which are part of the Agricultural Cohort consortium and which collected information about animal farming and cancer were used. Analyses included 316 270 farmers and farm workers. Adjusted Cox models were used to investigate the associations of 13 histological subtypes of LHC (n=3282) with self-reported livestock (cattle, pigs and sheep/goats) and poultry (ever/never and numbers raised) farming. Cohort-specific HRs were combined using random-effects meta-analysis.

RESULTS

Ever animal farming in general or farming specific animal species was not meta-associated with overall LHC. The risk of myeloid malignancies decreased with increasing number of livestock (p trend=0.01). Increased risk of myeloproliferative neoplasms was seen with increasing number of sheep/goats (p trend <0.01), while a decreased risk was seen with increasing number of livestock (p trend=0.02). Between cohorts, we observed heterogeneity in the association of type of animal farmed and various LHC subtypes.

CONCLUSIONS

This large-scale study of three prospective agricultural cohorts showed no association between animal farming and LHC risk, but few associations between specific animal species and LHC subtypes were observed. The observed differences in associations by countries warrant further investigations.

The prevalence of exposure to high molecular weight asthmagens derived from plants among workers in Australia

BACKGROUND

Limited information is available on exposure to high molecular weight (HMW) asthmagens derived from plants and on the main occupations and tasks that result in such exposure among workers.

METHODS

Data were collected as part of the Australian Work Exposures Study-Asthma. We estimated adjusted prevalence ratios (aPR) using modified Poisson regression models to determine which factors were associated with exposure.

RESULTS

A 12.8% of 4878 workers were exposed to HMW asthmagens derived from plants. The highest prevalence of exposure was found among farmers/animal workers, education workers, and food processing workers. The main circumstances of exposure were through handling flour, freesias, or through raising livestock. Exposure was more common among female workers (aPR = 1.26, 1.10-1.43) than males, while it was lower among workers born overseas (aPR = 0.70, 0.57-0.86) than those born in Australia.

CONCLUSION

Prevention of exposure to HMW asthmagens derived from plants requires a broad strategy targeting different tasks and occupations.

Exposure to Inhalable Dust, Endotoxin, and Total Volatile Organic Carbons on Dairy Farms Using Manual and Automated Feeding Systems

Introduction

Agricultural workers tend to have high exposures to organic dusts which may induce or exacerbate respiratory disorders. Studies investigating the effect of work tasks and farm characteristics on organic dust exposures among farm workers suggest that handling of animal feed is an important exposure determinant; however, the effect of the animal feeding system has not been explored in any detail.

Objectives

To measure the exposure of Irish dairy farmers to inhalable dust, endotoxin, and total volatile organic compounds (TVOCs) during parlour work and to explore whether levels of exposure to these agents depend on the applied feeding system in the farms.

Methods

Thirty-eight personal exposure measurements were collected from farmers across seven dairy farms. The farms used manual, loft, or semi-automated feeding systems. Information on worker tasks and farm characteristics was collected during the surveys. Associations between exposure concentrations and feeding systems, worker tasks, and other farm characteristics were explored in linear mixed-effect regression models with farmer identity treated as a random effect.

Results

Exposure concentrations were variable and had a geometric mean (GM; geometric standard deviation) of 1.5 mg m-3 (1.8) for inhalable dust and 128 EU m-3 (2.5) for endotoxin. More than 50% of the exposure measurements for endotoxin, and organic dust exceeded recommended health-based occupational exposure limits. Endotoxin levels were somewhat lower in farms using semi-automatic feeding systems when compared to those using manual feeding systems but in multivariate regression analysis associations were not statistically significant (β = -0.54, P = 0.4). Performance of activities related to handling and spreading of hay or straw was the strongest determinant for both inhalable dust and endotoxin exposure (β = 0.78, P ≤ 0.001; β = 0.72, P = 0.02, respectively). The level of dust exposure increased also as a consequence of a lower outdoor temperature, and higher ratio of distributed feed per cow (P = 0.01). Stationary measurements of TVOC and CO2 concentrations inside the dairy parlours had a GM of 180 ppb (1.9) and 589 ppb (1.3), respectively. The use of cow teat disinfectants and building ventilation were both strong predictors of TVOC concentrations within parlours.

Conclusions

Dairy farm workers can be exposed to high and variable levels of inhalable dust and endotoxin and may be at risk of respiratory disease. Results from this study suggest that exposure control strategies for organic dusts and TVOCs exposures should consider building ventilation and work tasks such as spreading of bedding material, using spray disinfectants and animal feeding. Until effective permanent engineering controls are established farm workers should be encouraged to wear respiratory protective equipment during these tasks.

Rural Residence and Chronic Obstructive Pulmonary Disease Exacerbations. Analysis of the SPIROMICS Cohort

Rationale: Rural residence is associated with poor outcomes in several chronic diseases. The association between rural residence and chronic obstructive pulmonary disease (COPD) exacerbations remains unclear.Objectives: In this work, we sought to determine the independent association between rural residence and COPD-related outcomes, including COPD exacerbations, airflow obstruction, and symptom burden.Methods: A total of 1,684 SPIROMICS (Subpopulations and Intermediate Outcome Measures in COPD Study) participants with forced expiratory volume in 1 second/forced vital capacity < 0.70 had geocoding-defined rural-urban residence status determined (N = 204 rural and N = 1,480 urban). Univariate and multivariate logistic and negative binomial regressions were performed to assess the independent association between rurality and COPD outcomes, including exacerbations, lung function, and symptom burden. The primary exposure of interest was rural residence, determined by geocoding of the home address to the block level at the time of study enrollment. Additional covariates of interest included demographic and clinical characteristics, occupation, and occupational exposures. The primary outcome measures were exacerbations determined over a 1-year course after enrollment by quarterly telephone calls and at an annual research clinic visit. The odds ratio (OR) and incidence rate ratio (IRR) of exacerbations that required treatment with medications, including steroids or antibiotics (total exacerbations), and exacerbations leading to hospitalization (severe exacerbations) were determined after adjusting for relevant covariates.Results: Rural residence was independently associated with a 70% increase in the odds of total exacerbations (OR, 1.70 [95% confidence interval (CI), 1.13-2.56]; P = 0.012) and a 46% higher incidence rate of total exacerbations (IRR 1.46 [95% CI, 1.02-2.10]; P = 0.039). There was no association between rural residence and severe exacerbations. Agricultural occupation was independently associated with increased odds and incidence of total and severe exacerbations. Inclusion of agricultural occupation in the analysis attenuated the association between rural residence and the odds and incidence rate of total exacerbations (OR, 1.52 [95% CI, 1.00-2.32]; P = 0.05 and IRR 1.39 [95% CI, 0.97-1.99]; P = 0.07). There was no difference in symptoms or airflow obstruction between rural and urban participants.Conclusions: Rural residence is independently associated with increased odds and incidence of total, but not severe, COPD exacerbations. These associations are not fully explained by agriculture-related exposures, highlighting the need for future research into potential mechanisms of the increased risk of COPD exacerbations in the rural population.

Risk factors associated with allergic sensitization and asthma phenotypes among poultry farm workers

BACKGROUND

This study investigated the risk factors for occupational allergic sensitization and various asthma phenotypes in poultry-workers.

METHODS

A cross-sectional study of 230 workers used a modified ECRHS questionnaire, spirometry, FeNO, Phadiatop, and sIgE to poultry farming related allergens.

RESULTS

Worker's mean age was 37 ± 9 years, 68% male, 43% current-smokers, 34% atopic, and 5% casual-workers. The prevalence of non-atopic asthma (NAA = 7%) was higher than atopic-asthma (AA = 5%) and probable allergic occupational-asthma (OA = 3%). Sensitization to at least one poultry farming related allergen was 24%. Workers sensitized to chicken-specific-allergens were more likely to be atopic (OR_unadj  = 20.9, 95%CI: 4.7-93.2) or employed as casual-workers (OR_unadj  = 6.0, 95%CI: 1.1-35.9). Work-related chest symptoms were associated the rearing-department (OR_adj  = 3.2, 95%CI: 1.2-8.4) and exposure to high gas/dust/fumes (OR_adj  = 4.8, 95%CI: 2.4-9.5). Airflow reversibility (OR_adj  = 10.9, 95%CI: 2.0-60.3) was significantly associated with casual-work status.

CONCLUSION

Allergic and non-allergic mechanisms play a role in asthma development among poultry-workers with casual workers demonstrating increased risk.

Environmental exposure to pesticides and respiratory health

Respiratory effects of environmental exposure to pesticides are debated. Here we aimed to review epidemiological studies published up until 2013, using the PubMed database. 20 studies dealing with respiratory health and non-occupational pesticide exposure were identified, 14 carried out on children and six on adults. In four out of nine studies in children with biological measurements, mothers' dichlorodiphenyldichloroethylene (DDE) blood levels during pregnancy were associated with asthma and wheezing in young children. An association was also found between permethrin in indoor air during pregnancy and wheezing in children. A significant association between asthma and DDE measured in children's blood (aged 7-10 years) was observed in one study. However, in three studies, no association was found between asthma or respiratory infections in children and pesticide levels in breast milk and/or infant blood. Lastly, in three out of four studies where post-natal pesticide exposure of children was assessed by parental questionnaire an association with respiratory symptoms was found. Results of the fewer studies on pesticide environmental exposure and respiratory health of adults were much less conclusive: indeed, the associations observed were weak and often not significant. In conclusion, further studies are needed to confirm whether there is a respiratory risk associated with environmental exposure to pesticides.

Occupational exposure to pesticides and respiratory health

This article aims to review the available literature regarding the link between occupational exposure to pesticides and respiratory symptoms or diseases. Identification of epidemiological studies was performed using PubMed. 41 articles were included, 36 regarding agricultural workers and five regarding industry workers. Among the 15 cross-sectional studies focusing on respiratory symptoms and agricultural pesticide exposure, 12 found significant associations with chronic cough, wheeze, dyspnoea, breathlessness or chest tightness. All four studies on asthma found a relationship with occupational exposure, as did all three studies on chronic bronchitis. The four studies that performed spirometry reported impaired respiratory function linked to pesticide exposure, suggestive of either obstructive or restrictive syndrome according to the chemical class of pesticide. 12 papers reported results from cohort studies. Three out of nine found a significant relationship with increased risk of wheeze, five out of nine with asthma and three out of three with chronic bronchitis. In workers employed in pesticide production, elevated risks of chronic obstructive pulmonary disease (two studies out of three) and impaired respiratory function suggestive of an obstructive syndrome (two studies out of two) were reported. In conclusion, this article suggests that occupational exposure to pesticides is associated with an increased risk of respiratory symptoms, asthma and chronic bronchitis, but the causal relationship is still under debate.

Chronic Respiratory Symptoms and Lung Function in Agricultural Workers - Influence of Exposure Duration and Smoking

INTRODUCTION

Job exposure in agricultural workers often leads to respiratory impairment.

AIM

To assess the influence of exposure duration and smoking on chronic respiratory symptoms and ventilatory capacity in agricultural workers.

METHODS

A cross-sectional study covered 75 agricultural workers, compared with an equal number of office workers matched by age, exposure duration and smoking status. Standardized questionnaire was used to obtain data on chronic respiratory symptoms, job and smoking history. Lung functional testing was performed by spirometry.

RESULTS

The prevalence of respiratory symptoms was higher in agricultural workers, with significant difference for cough (P = 0.034), and dyspnea (P = 0.028). Chronic respiratory symptoms among agricultural workers were significantly associated with duration of exposure (P < 0.05) and daily smoking (P < 0.01), as well as with daily smoking in controls (P < 0.01). The average values of spirometric parameters in exposed workers were significantly different for MEF50 (P = 0.002), MEF75 (P = 0.000), and MEF25-75 (P = 0.049). Obstructive changes in small airways in exposed workers were strongly related to exposure duration (P < 0.05) and smoking (P < 0.01). Agricultural workers with job exposure more than 15 years had more expressed adverse respiratory symptoms and lung function decline.

CONCLUSION

The results confirmed the influence of agricultural exposure and daily smoking on chronic respiratory symptoms and airflow limitation, primarily targeting the small airways.

Bronchial Hyperresponsiveness in Farmers: Severity and Work-Relatedness

OBJECTIVE: To evaluate the prevalence of respiratory symptoms, lung function and bronchial hyperresponsiveness in farmers, with emphasize to their severity and work-relatedness due occupational risk factors and farming characteristics.METHODS: A cross-sectional survey was performed including 60 cow breeders aged 21 to 65 years, compared to an equal number of agricultural farmers matched by age, job exposure duration, and smoking status. We have used a questionnaire to record the chronic respiratory symptoms, detailed work history, specific farming activities and tasks performed, and smoking history. Evaluation of examined subjects also included lung function spirometry tests, and bronchial hyperresponsiveness testing.RESULTS: We found higher prevalence of work related respiratory symptoms in the last 12 months in cow breeders with significant difference for phlegm (P = 0.039), and wheezing (P = 0.026). Mean values of all spirometric parameters were lower in cow breeders, reaching significance for MEF50 (P = 0.001) and MEF75 (P = 0.000). Significant difference was found for mild bronchial hyperresponsiveness among cow breeders with job exposure of more than 15 years. The risk of developing work-related respiratory symptoms increased significantly with full-time farming, exposure to gases and vapors, and keeping more than 10 cows.CONCLUSION: Our data suggest that workplace exposure in farmers may cause respiratory impairment which is closely related to its duration, characteristics, and intensity. The results suggest that cow breeders in general have higher rates of work-related respiratory symptoms and bronchial hyperresponsiveness than agricultural farmers, whereas their severity increases with an increase in frequency and duration of animal contact.

Systematic review of respiratory health among dairy workers

The dairy industry is changing on a global scale with larger, more efficient operations. The impact of this change on worker health and safety, specifically, associations between occupational lung disease and inhalation exposures, has yet to be reported in a comprehensive review of the scientific literature. Therefore, a three-tier process was used to identify information using a keyword search of online databases of scientific literature. Of the 147 citations reviewed, 52 met initial screening criteria, and 30 were included in this review. Dairy workers experience lung conditions such as asthma, chronic obstructive pulmonary disease, hypersensitivity pneumonitis, chronic bronchitis, and cancer. Recent pulmonary function studies have identified obstructive lung changes among dairy farm workers. The increased scale of dairy production with significant changes in technology and work practices has altered inhalation exposure patterns among dairy workers. The inhalation exposure in the dairy work environment may elicit differing inflammatory responses in relation to timing of initial exposure as well as to repeated exposures. Few studies have measured inhalation exposure while simultaneously assessing the impact of the exposure on lung function of dairy farm workers. Even fewer studies have been implemented to assess the impact of aerosol control technology to reduce inhalation exposure. Future research should evaluate worker exposure to aerosols through a task-based approach while utilizing novel methods to assess inhalation exposure and associated inflammatory responses. Finally, potential solutions should be developed and tested to reduce inhalation exposure to inflammatory agents and respiratory diseases in the dairy farm work environment.

Agricultural exposure and asthma risk in the AGRICAN French cohort

Epidemiological studies have reported an increased risk of respiratory diseases in agricultural population, but a protective "farm-effect" has also been reported for asthma. In the AGRICAN cohort, self-reported doctor-diagnosed asthma was analyzed according to allergy, in relation with history of life-time exposure to 13 crops and 5 livestock, pesticide exposure and early life on a farm, taking into account sex, age, education and body mass index. Among the 1246 asthmatics (8.0%), 505 were allergic (3.3%) and 719 non-allergic (4.6%). In multivariate analysis, a significant excess was observed, only for allergic asthma, in vine-growing (OR=1.43, p=0.002), fruit-growing (OR=1.58, p=0.001), greenhouses (OR=1.66, p=0.02), grasslands (OR=1.35, p=0.009), beets (OR=1.52, p=0.003) and horses (OR=1.35, p=0.04). Pesticide use and history of pesticide poisoning were significantly associated with allergic asthma in grassland, vineyards and fruit-growing and with non-allergic asthma in beets. Living on a farm in the first year of life tended to be protective for childhood allergic asthma in farms with livestock (OR=0.72, p=0.07) but deleterious in farms with vineyards, fruit or vegetables (OR=1.44, p=0.07). In AGRICAN, an increased risk of allergic asthma was observed with crop exposure, pesticide use and early life on a farm, especially in vine-growing, grassland, beets, fruit and vegetable-growing.

Pulmonary function reductions among potentially susceptible subgroups of agricultural workers in Colorado and Nebraska

OBJECTIVE

Organic dust inhalation has been associated with adverse respiratory responses among agricultural workers. We evaluated factors that may confer increased susceptibility to these health effects.

METHODS

We quantified personal work shift exposures to inhalable dust, endotoxin, and its 3-hydroxy fatty acid constituents, and evaluated changes in pulmonary function among 137 grain elevator, cattle feedlot, dairy, and corn farm workers.

RESULTS

Increased dust exposure was associated with work shift reductions in lung function. Although interpretation is limited because of small samples, a suggestion of stronger exposure-response relationships was observed among smokers, as well as workers reporting pesticide/herbicide application, asthma, or allergies, and those with genetic polymorphisms (TLR4) (Pinteraction ≤ 0.05).

CONCLUSIONS

A better understanding of factors leading to increased susceptibility of adverse respiratory outcomes is needed to optimize exposure reduction strategies and develop more comprehensive wellness programs.

Bronchial asthma and COPD due to irritants in the workplace - an evidence-based approach

BACKGROUND

Respiratory irritants represent a major cause of occupational obstructive airway diseases. We provide an overview of the evidence related to irritative agents causing occupational asthma or occupational COPD.

METHODS

We searched MEDLINE via PubMed. Reference lists of relevant reviews were also screened. The SIGN grading system was used to rate the quality of each study. The modified RCGP three-star system was used to grade the body of evidence for each irritant agent regarding its causative role in either occupational asthma or occupational COPD.

RESULTS

A total of 474 relevant papers were identified, covering 188 individual agents, professions or work-sites. The focus of most of the studies and the predominant diagnosis was occupational asthma, whereas occupational COPD arose only incidentally.The highest level assigned using the SIGN grading was 2+ (well-conducted systematic review, cohort or case-control study with a low risk of confounding or bias). According to the modified RCGP three-star grading, the strongest evidence of association with an individual agent, profession or work-site ("**") was found for 17 agents or work-sites, including benzene-1,2,4-tricarboxylicacid-1,2-anhydride, chlorine, platinum salt, isocyanates, cement dust, grain dust, animal farming, environmental tobacco smoke, welding fumes or construction work. Phthalic anhydride, glutaraldehyde, sulphur dioxide, cotton dust, cleaning agents, potrooms, farming (various), foundries were found to be moderately associated with occupational asthma or occupational COPD ("*[+]").

CONCLUSION

This study let us assume that irritant-induced occupational asthma and especially occupational COPD are considerably underreported. Defining the evidence of the many additional occupational irritants for causing airway disorders will be the subject of continued studies with implications for diagnostics and preventive measures.

Atopy is associated with asthma in adults living in rural and urban southwestern Nigeria

RATIONALE

Factors affecting the course of asthma are not clearly understood in rural and urban communities within low-resource countries. Furthermore, the interactions between atopy, environmental exposure, and helminthic infections in modulating asthma have not been well investigated.

OBJECTIVES

To conduct a feasibility study to examine the relationship between atopy and asthma in adults at two rural Health Centers and urban university college hospital in southwestern Nigeria.

METHODS

A convenient sample of 55 consecutive patients with stable physician-diagnosed asthma and 55 age-matched nonasthmatic controls seen at the outpatient clinics in two rural Health Centers and an urban university hospital were enrolled. All subjects underwent blood test, allergy skin test, and stool examination for ova and parasites. Wilcoxon sign-rank tests were used to compare serum eosinophilia and allergy skin test between the two groups.

RESULTS

Asthmatics in both urban and rural settings had significantly more positive skin reactions to house dust mite, cockroach, mold, and mouse epithelium than nonasthmatic controls (p < .05). Mean total serum IgE was also significantly higher in asthmatics than in nonasthmatic controls (360 vs. 90 IU/L, p <.001). Stool parasitemia was infrequent in both groups and not statistically significant.

CONCLUSION

Atopy is associated with adult asthma in southwest Nigeria. Larger studies to confirm the nature of this association and to examine the role of helminthic infection and other environmental factors on the expression of asthma are needed.

Ethnic, racial, and gender variations in health among farm operators in the United States

PURPOSE

The purpose of this study was to collect baseline prevalence data on the health problems faced by minority, white, and female farm operators.

METHODS

An occupational health survey of farm operators was conducted by the U.S. Department of Agriculture, National Agricultural Statistics Service between February and August 2000. A stratified random sample of farm operators from 50 U.S. states based on the 1997 Census of Agriculture was selected for telephone interview. Interviews were primarily conducted using a computer assisted telephone instrument system.

RESULTS

Population prevalences were calculated for 7137 farm operators. Prevalences were greatest for musculoskeletal discomfort, followed by respiratory problems, hearing loss, and hypertension. Generally, Latino and Asian American operators had lower prevalences for health problems than white non-Latino and white operators, respectively. African-American operators had greater prevalences for hypertension, and osteoarthritis, but lower prevalences for hearing loss, skin problems, heart problems, and cancer than white operators. American Indian or Alaska Native operators had higher prevalences for musculoskeletal problems, skin problems, and hypertension.

CONCLUSIONS

Prevalences for the different ethnicity and race groups are not the same. Studies that combine racial and ethnic groups, or study only white and non-Latino farm operators may overestimate or underestimate the prevalence of health conditions in the entire farm operator population.

Decreased lung function after inhalation of ultrafine and fine particulate matter during exercise is related to decreased total nitrate in exhaled breath condensate

This study was designed to investigate PM(1) inhalation during exercise on lung function, exhaled nitric oxide (eNO), and total nitrate (NO3), S-nitrosoglutathione (GSNO), and malondialdehyde (MDA) in exhaled breath condensate (EBC). Inhalation of combustion-derived PM is associated with adverse respiratory health. A mechanistic action of PM on lung function is not defined; however, nitrosative/oxidative stress is likely. Prior to and after two 30-min exercise bouts 4-5 days apart, inhaling low (7382 +/- 1727 particles cm(- 3)) or high (252,290 +/- 77,529 particles cm(- 3)) PM(1), 12 nonasthmatic males performed spirometry and eNO and EBC collection. Normal resting lung function did not change after low PM(1) exercise. After high PM(1) exercise, FEV(1) and FEF(25-75) fell significantly (p = .0005, p = .002) and was related to [PM(1)] (r = -.55, p = .005 and r =-.61, p = .002; respectively); 11- and 52-ml decreases were calculated for each 20,000 particles cm(- 3) increase for FEV and FEF(25-75). NO3 did not change after low PM(1) exercise (30.5% increase), but significantly decreased by 43.8% after high PM(1) exercise, and correlated with lung function changes (r = .63, and r = .54 for FEV(1) and FEF(25-75), respectively; p = .001 and p = .007). No change in GSNO was observed. Alveolar NO decreased after high PM(1) conditions (p = .02); eNO pre-to-post difference was related to changes in FEV(1) (r = .60, p = .002). MDA increased 40% after low PM exercise (NS) and increased 208% after high PM exercise (p = .06). Thus, high PM(1) inhalation during exercise caused a reduced alveolar contribution to eNO; NO3 and eNO variables were decreased and were related to impaired lung function. Decreased NO(3) and eNO may be due to superoxide/NO formation of peroxynitrite, resulting in lipid peroxidation.

Pesticides and atopic and nonatopic asthma among farm women in the Agricultural Health Study

RATIONALE

Risk factors for asthma among farm women are understudied.

OBJECTIVES

We evaluated pesticide and other occupational exposures as risk factors for adult-onset asthma.

METHODS

Studying 25,814 farm women in the Agricultural Health Study, we used self-reported history of doctor-diagnosed asthma with or without eczema and/or hay fever to create two case groups: patients with atopic asthma and those with nonatopic asthma. We assessed disease-exposure associations with polytomous logistic regression.

MEASUREMENTS AND MAIN RESULTS

At enrollment (1993-1997), 702 women (2.7%) reported a doctor's diagnosis of asthma after age 19 years (282 atopic, 420 nonatopic). Growing up on a farm (61% of all farm women) was protective for atopic asthma (odds ratio [OR], 0.55; 95% confidence interval [CI], 0.43-0.70) and, to a lesser extent, for nonatopic asthma (OR, 0.83; 95%CI, 0.68-1.02; P value for difference = 0.008). Pesticide use was almost exclusively associated with atopic asthma. Any use of pesticides on the farm was associated only with atopic asthma (OR, 1.46; 95% CI, 1.14-1.87). This association with pesticides was strongest among women who had grown up on a farm. Women who grew up on farms and did not apply pesticides had the lowest overall risk of atopic asthma (OR, 0.41; 95% CI, 0.27-0.62) compared with women who neither grew up on farms nor applied pesticides. A total of 7 of 16 insecticides, 2 of 11 herbicides, and 1 of 4 fungicides were significantly associated with atopic asthma; only permethrin use on crops was associated with nonatopic asthma.

CONCLUSIONS

These findings suggest that pesticides may contribute to atopic asthma, but not nonatopic asthma, among farm women.

[Farm work, dust exposure and respiratory symptoms among farmers]

OBJECTIVE

Environmental working conditions in rural areas, notably exposure to organic and mineral dusts, have been associated with increases in respiratory diseases. The objective of this study was to evaluate the prevalence of respiratory symptoms among farmers and the associations of these with occupational risk factors.

METHODS

This cross-sectional study was undertaken in 1996 with 1,379 farmers from Southern Brazil. Sociodemographic and farming-production parameters were collected, as were levels of exposure to organic and mineral dusts. Respiratory symptoms were assessed by a modified version of American Thoracic Society-Division of Lung Disease questionnaire. Multiple logistic regression analysis was used in analyses, controlling for confounding factors.

RESULTS

The majority (52%) of interviewees worked in activities with intense exposure to dust. Workers on farms with better economic indicators had a lower prevalence of respiratory symptoms. Poultry workers showed more symptoms of chronic respiratory disease (OR=1.60; 95% CI: 1.05-2.42). Farmers exposed to high concentrations of dust had more than 70% higher risk of asthma symptoms (OR=1.71; 95% CI: 1.10-2.67) and chronic respiratory disease symptoms (OR=1.77; 95% CI: 1.25-2.50).

CONCLUSIONS

The rural workers studied herein were exposed to high levels of organic and mineral dusts. Those exposed to higher dust concentrations, such as poultry workers, showed an increased risk of work-related respiratory symptoms. The implementation of respiratory protection programs is recommended, emphasizing workers involved with poultry production.

Reduced risk of atopic sensitization among farmers: the Humboldt study

BACKGROUND

It needs to be clarified whether farming is associated with a reduced risk of atopy or allergic condition. There is a lack of consistent evidence for prevalences of atopy, respiratory allergy and asthma in adult farmers.

METHODS

A cross-sectional study of adults (n = 2,081) was conducted in the town of Humboldt, Sask. Allergy skin prick tests were conducted to determine atopic sensitization. Respiratory allergy and physician-diagnosed asthma were based on self-reporting. Logistic regression was used to assess the associations of atopy, respiratory allergy and asthma with farming practices, adjusting for other important variables.

RESULTS

Of 2,081 participants, 27.8% were farmers. Reduced risks of atopic sensitization, respiratory allergy and asthma were observed among farmers compared to non-farmers. After adjustment for sex and age, which are major confounders, the odds ratio for atopic sensitization was 0.79 (95% confidence interval: 0.65, 0.97) for farmers versus non-farmers. Asthma showed a similar trend; however, there was no statistically significant difference in either respiratory allergy or asthma rates observed between farmers and non-farmers.

CONCLUSIONS

The prevalence of atopy was lower in adult farmers than in non-farmers.

Prevalence of work-related respiratory symptoms in Iranian farmers

BACKGROUND

Animal exposure may be an important trigger for work-related symptoms among farmers.

OBJECTIVE

To estimate the prevalence of work-related respiratory symptoms (WRS) in sheep breeders and agricultural farmers and to determine work-related risk factors.

METHODS

A family doctor used a questionnaire to interview a cohort of 173 farmers comprised of 127 sheep breeders and 46 agricultural farmers in the rural area of Rokh (northeast Iran). The questionnaire pertained to recurrent wheezing, cough, breathlessness or chronic phlegm while at work (these symptoms define WRS), flu-like illness and physician-diagnosed asthma.

RESULTS

There were 71 subjects (41%) with WRS: 10 of 46 agricultural farmers (21.7%) and 61 of 127 sheep breeders (48.0%). The proportions of sheep breeders with wheezing (16.5%), asthma (14%), cough (29%), breathlessness (31.5%) and flu-like illness (38%) were higher than in agricultural farmers. A significant dose-response relationship among the daily hours worked with animals, the number of animals and the prevalence of symptoms was established for sheep farmers. Sheep shearing and the use of pesticide were associated with an increased risk of wheezing and phlegm.

CONCLUSIONS

The results suggest that sheep farmers in general have higher rates of work-related symptoms than agricultural farmers. The severity of work-related symptoms will increase with an increase in frequency of animal contact; therefore, these results may underestimate the impact of this exposure.

Pesticides associated with wheeze among commercial pesticide applicators in the Agricultural Health Study

Pesticides are potential risk factors for respiratory disease among farmers, but farmers are also exposed to other respiratory toxicants. To explore the association of pesticides with wheeze in a population without other farming exposures, the authors analyzed data from 2,255 Iowa commercial pesticide applicators enrolled in the Agricultural Health Study. Controlling for age, smoking status, asthma and atopy history, and body mass index, the authors calculated odds ratios for the relationship between wheeze and 36 individual pesticides participants had used during the year before enrollment (1993-1997). Eight of 16 herbicides were associated with wheeze in single-agent models; however, the risk was almost exclusively associated with the herbicide chlorimuron-ethyl (odds ratio (OR) = 1.62, 95% confidence interval (CI): 1.25, 2.10). Inclusion of chlorimuron-ethyl in models for the other herbicides virtually eliminated the associations. The odds ratios for four organophosphate insecticides (terbufos, fonofos, chlorpyrifos, and phorate) were elevated when these chemicals were modeled individually and remained elevated, though attenuated somewhat, when chlorimuron-ethyl was included. The association for dichlorvos, another organophosphate insecticide, was not attenuated by chlorimuron-ethyl (OR = 2.48, 95% CI: 1.08, 5.66). Dose-response trends were observed for chlorimuron-ethyl, chlorpyrifos, and phorate; the strongest odds ratio was for applying chlorpyrifos on more than 40 days per year (OR = 2.40, 95% CI: 1.24, 4.65). These results add to the emerging literature linking organophosphate insecticides and respiratory health and suggest a role for chlorimuron-ethyl.

A brief targeted review of susceptibility factors, environmental exposures, asthma incidence, and recommendations for future asthma incidence research

Relative to research on effects of environmental exposures on exacerbation of existing asthma, little research on incident asthma and environmental exposures has been conducted. However, this research is needed to better devise strategies for the prevention of asthma. The U.S. Environmental Protection Agency (EPA) and National Institute of Environmental Health Sciences held a conference in October 2004 to collaboratively discuss a future research agenda in this area. The first three articles in this mini-monograph summarize the discussion on potential putative environmental exposure; they include an overview of asthma and conclusions of the workshop participants with respect to public health actions that could currently be applied to the problem and research needs to better understand and control the induction and incidence of asthma, the potential role of indoor/outdoor air pollutants in the induction of asthma), and biologics in the induction of asthma. Susceptibility is a key concept in the U.S. EPA "Asthma Research Strategy" document and is associated with the U.S. EPA framework of protecting vulnerable populations from potentially harmful environmental exposures. Genetics, age, and lifestyle (obesity, diet) are major susceptibility factors in the induction of asthma and can interact with environmental exposures either synergistically or antagonistically. Therefore, in this fourth and last article we consider a number of "susceptibility factors" that potentially influence the asthmatic response to environmental exposures and propose a framework for developing research hypotheses regarding the effects of environmental exposures on asthma incidence and induction.

Asthma among rural Minnesota adolescents

This study examined the prevalence of and risk factors for wheezing and asthma in rural Minnesota adolescents. A survey querying about wheezing, asthma, farm residence, and other respiratory-related factors was administered to all 9th to 11th grade students (N = 13,490) in a stratified, random sample of high schools in rural Minnesota. Nearly one in 8 (12.6%) students reported ever-diagnosed asthma, and 9.2% reported current asthma. Students living on farms reported less wheezing and asthma than rural non-farm students. Obesity and smoking were associated with wheezing and asthma in all rural adolescents. Asthma rates increased with age among girls and may be largely accounted for by simultaneous increases in smoking rates. Despite the apparent protective effect of farm residence, asthma remains a significant public health issue among rural Minnesota adolescents.

Another explanation for the low allergy rate in the rural Alpine foothills

A low allergy rate in coal and wood heated homes has been described in the small villages in the Alpine foothills and subsequently found to be associated with the farming environment. This was interpreted within the framework of the hygiene hypothesis but there are also alternative explanations. Lower air pollution could be one reason, which is, however, unlikely since the differences between the Bavarian countryside and the Munich municipal area were only weak. There could be genetic differences between the urban and rural population by previous isolation or by self-selection. The potential drop-out of allergy genes, however, will also not explain the absent increase of allergies in two generations. More likely, other lifestyle factors are important. Dietary habits are different in farmers and a less frequent vitamin D supplementation of newborns (otherwise expected to be allergy promoting) has been shown recently. The underlying cause for the "non-allergic farm child" remains speculative until the transfer of any farm-associated factor is leading to a similar risk reduction in the general population.

Comparison of Farmers in the Agricultural Health Study to the 1992 and 1997 Censuses of Agriculture

CONTEXT

The Agricultural Health Study (AHS) is a large, prospective cohort study in the states of Iowa and North Carolina that has been developed to better understand how pesticides and other agricultural exposures relate to the occurrence of cancer and other diseases.

PURPOSE

This report compares the characteristics of AHS farmers to the Census of Agriculture to evaluate the generalizability of AHS findings.

METHODS

We restricted the AHS to private pesticide applicators who enrolled in Iowa (n = 31,065) and in North Carolina (n = 17,239) between 1993 and 1997, and who identified themselves as living or working on a farm. We compared their self-reported data with data from the 1992 and 1997 Censuses of Agriculture.

FINDINGS

AHS farmers in Iowa are younger; live or work on larger farms; more frequently apply herbicides, insecticides, and fungicides; and are more likely to raise beef cattle and swine, and grow corn, soybeans, hay, and oats. AHS farmers in North Carolina are also younger, live or work on larger farms, more frequently reported growing crops commonly seen in the state, and are more frequent pesticide users. However, animals raised are similar to those in the North Carolina Census of Agriculture.

CONCLUSIONS

AHS farmers likely represent the higher end of pesticide usage in both states in part because AHS farmers have larger farms. Since the health effects of pesticides are best ascertained among pesticide users with the greatest exposure, the AHS cohort should prove to be a valuable resource for health effects research.

Disease and injury among participants in the Agricultural Health Study

The Agricultural Health Study (www.aghealth.org) is a cohort of 89,658 pesticide applicators and their spouses from Iowa and North Carolina assembled between 1993 and 1997 to evaluate riskfactorsfor disease in ruralfarm populations. This prospective study is just now reaching sufficient maturity for analysis of many disease endpoints. Nonetheless, several analyses have already provided interesting and important leads regarding disease patterns in agricultural populations and etiologic clues for the general population. Compared to the mortality experience of the general population in the two states (adjusted for race, gender, age and calendar time), the cohort experienced a very low mortality rate overall and for many specific causes and a low rate of overall cancer incidence. A few cancers, however, appear elevated, including multiple myeloma and cancers of the lip, gallbladder, ovary, prostate, and thyroid, but numbers are small for many cancers. A study of prostate cancer found associations with exposure to several pesticides, particularly among individuals with a family history of prostate cancer. Links to pesticides and other agricultural factors have been found for injuries, retinal degeneration, and respiratory wheeze. Methodological studies have determined that information collected by interview is unbiased and reliable. A third round of interviews scheduled to begin in 2005 will collect additional information on agricultural exposures and health outcomes. The study can provide data to address many health issues in the agricultural community. The study investigators welcome collaboration with interested scientists.

Chronic disease risk in central New York dairy farmers: results from a large health survey 1989-1999

BACKGROUND

The agricultural workplace presents a variety of health and safety hazards; it is unknown whether farm work may be a risk factor for certain chronic diseases.

METHODS

The health survey data from a large rural population in central New York were used from two studies (1989, 1999) to assess both 1999 prevalence and 10-year incidence of self-reported diabetes, heart disease, hypercholesterolemia, and hypertension among farm (predominantly dairy) and non-farm residents. The 1999 asthma prevalence was also assessed.

RESULTS

Multiple logistic regression models for 1999 prevalence found statistically significant protective effects of farming for hypertension (OR=0.83, P=0.0105) and hypercholesterolemia (OR=0.853, P=0.0522). Non-significant results were seen for heart disease (OR=0.67, P=0.128) and diabetes (OR=0.856, P=0.1358). The model for 1999 asthma prevalence showed a significantly elevated risk for farming (OR=1.542, P=0.0004). Logistic models created for the 10-year incidence of hypertension, hypercholesterolemia, diabetes, and heart disease did not show a significant effect for farming.

CONCLUSIONS

The protective effect of farming observed for the 1999 prevalence of hypertension and hypercholesterolemia was not seen for the 10-year incidence of these diseases.

Asthma and atopy in rural children: is farming protective?

The prevalence of asthma and other atopic diseases has recently increased, especially in urban and modernized regions of the world. The majority of published prevalence surveys report that asthma and atopy are less common among children living in rural areas. While many exposures differ in rural and urban areas of the world, several recent studies have suggested that agricultural exposures in early childhood may decrease the risk of developing atopic disease. Livestock exposure, in particular, seems to be important, but additional research is needed to pinpoint the underlying mechanisms behind this apparent protective effect of rural and farm living. Additionally, prospective studies are needed to more closely examine the timing of farm exposures in relation to the onset of asthma and atopy, and to determine if the apparent protective effects of farming persist into adulthood.