***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Farmers have an increased risk of respiratory morbidity and mortality .  The causal agents have not been fully established . METHODS In a cross-sectional study of 4,735 Norwegian farmers , we assessed  respiratory symptoms and lung function .  Atopy was assessed in a sub sample ( n = 1,213 ) .  Personal exposures to dust , fungal spores , actinomycete spores , endotoxins , bacteria , storage mites , (1 - ->3)-ss-D-glucans , fungal antigens , organic dust , inorganic dust , silica , ammonia , and hydrogen sulfide were measured for 127 r and omly selected farms . RESULTS Compared to crop farmers , livestock farmers were more likely to have chronic bronchitis ( odds ratio [ OR ] , 1.9 ; 95 % confidence interval [ CI ] , 1.4 to 2.6 ) and COPD ( OR , 1.4 ; 95 % CI , 1.1 to 1.7 ) . FEV(1 ) ( -41 mL ; 95 % CI , -75 to -7 ) was significantly reduced , but FVC ( -15 mL ; 95 % CI , -54 to 24 ) was not . Exposure to most agents were predictors of respiratory morbidity , except FVC . Ammonia , hydrogen sulfide , and inorganic dust were most strongly associated in multiple regression models adjusted for coexposures , but the effects of specific biological agents could not be assessed in multiple regression models because they were too highly correlated . Farmers with atopy had a significantly lower FEV(1 ) ( OR , -87 mL ; 95 % CI , -170 to -7 ) , but atopy was not directly associated with chronic bronchitis , COPD , and FVC . However , the effects of farming and specific exposures on COPD were substantially greater in farmers with atopy . CONCLUSIONS Livestock farmers have an increased risk of chronic bronchitis , COPD , and reduced FEV(1 ) . Ammonia , hydrogen sulfide , inorganic dust , and organic dust may be causally involved , but a role for specific biological agents can not be excluded . Farmers with atopy appear more susceptible to develop farming-related COPD In the GRADE approach , r and omized trials start as high- quality evidence and observational studies as low- quality evidence , but both can be rated down if most of the relevant evidence comes from studies that suffer from a high risk of bias . Well-established limitations of r and omized trials include failure to conceal allocation , failure to blind , loss to follow-up , and failure to appropriately consider the intention-to-treat principle . More recently recognized limitations include stopping early for apparent benefit and selective reporting of outcomes according to the results . Key limitations of observational studies include use of inappropriate controls and failure to adequately adjust for prognostic imbalance . Risk of bias may vary across outcomes ( e.g. , loss to follow-up may be far less for all-cause mortality than for quality of life ) , a consideration that many systematic review s ignore . In deciding whether to rate down for risk of bias -- whether for r and omized trials or observational studies -- authors should not take an approach that averages across studies . Rather , for any individual outcome , when there are some studies with a high risk , and some with a low risk of bias , they should consider including only the studies with a lower risk of bias OBJECTIVES . Little is known about the health effects of living in close proximity to industrial swine operations . We assessed the relationship between estimated exposure to airborne effluent from confined swine feeding operations and  asthma symptoms among adolescents who were aged 12 to 14 years . METHODS . During the 1999–2000 school year , 58169 adolescents in North Carolina answered questions about their respiratory symptoms , allergies , medications , socioeconomic status , and household environments . To estimate the extent to which these students may have been exposed during the school day to air pollution from confined swine feeding operations , we used publicly available data about schools ( n = 265 ) and swine operations ( n = 2343 ) to generate estimates of exposure for each public school . Prevalence ratios and 95 % confidence intervals for wheezing within the past year were estimated using r and om-intercepts binary regression models , adjusting for potential confounders , including age , race , socioeconomic status , smoking , school exposures , and household exposures . RESULTS . The prevalence of wheezing during the past year was slightly higher at schools that were estimated to be exposed to airborne effluent from confined swine feeding operations . For students who reported allergies , the prevalence of wheezing within the past year was 5 % higher at schools that were located within 3 miles of an operation relative to those beyond 3 miles and 24 % higher at schools in which livestock odor was noticeable indoors twice per month or more relative to those with no odor . CONCLUSIONS . Estimated exposure to airborne pollution from confined swine feeding operations is associated with adolescents ’ wheezing symptoms OBJECTIVES To describe the relation between spirometric findings and farming characteristics and variables of exposure to organic dust measured during work in animal buildings . Farmers have traditionally been described as having one of the most dangerous occupations , so a large scale study on European farmers was carried out . This is the report of the second part of that study . METHODS 40 pig farmers in Denmark and 36 poultry farmers in Switzerl and were chosen r and omly and were assessed over 1 working day . RESULTS Mean ( SD ) baseline spirometric results in pig farmers were higher than in poultry farmers ( forced expiratory volume in 1 second ( FEV1 ) ( % of reference value ) 108.3 ( 16.7 ) v 100.2 ( 14.2 ) ; p=0.04 ) . Baseline lung function results were significantly associated with ventilation of the animal houses . Furthermore , temperature was related to spirometric findings in pig farmers . CONCLUSIONS Ventilation of the animal house and temperature might influence respiratory morbidity in farmers BACKGROUND Up to now potential health effects of environmental exposure to intensive livestock production facilities have not been thoroughly studied . The aim of the Lower Saxony Lung Study ( NiLS ) was to assess the prevalence of respiratory symptoms and disease in an area with intensive animal production facilities taking into account environmental exposure to emissions from these large-scale farms . METHODS All 10 864 inhabitants ( age 18 to 44 years ) of four towns with a large number of intensive animal production facilities in the area were invited to answer a mail-in question naire . Of these , 6416 subjects were r and omly selected for the clinical part of the study ( specific IgE , lung function measurements , bronchial provocation with methacholine ) . Overall , 6937 subjects answered the question naire ( 68 % ) , 60 % took part in the clinical tests . RESULTS The prevalence of allergic disease in the study population was lower than in urban citizens . Subjects with more than 12 animal houses within 500 m of their home had an increased odds ratio for wheezing without a cold ( odds ratio 2.7 ; 95 % confidence interval 1.4 - 5.4 ) . They also showed a significantly decreased FEV ( 1 ) ( mean 0.26 l ; 0.04 l - 0.48 l ) as well as a trend for a lower Tiffeneau-Index . CONCLUSIONS In result , a large number of intensive animal production facilities might be associated with decreased lung function results in the immediate neighbours . Further studies are necessary to confirm our findings Background : Despite public concern about potential adverse health effects of concentrated animal feeding operations , objective ly assessed data on environmental exposure to concentrated animal feeding operations and respiratory health are sparse . We aim ed to assess respiratory health in neighbors of confined animal feeding operations . Methods : A survey was done in 2002–2004 among all adults ( 18–45 years old ) living in 4 rural German towns with a high density of confined animal feeding operations . Question naire data were available for 6937 ( 68 % ) eligible subjects . In a r and om sample we measured the following outcomes : specific IgE to common and farm-specific allergens , lung function , and bronchial hyperresponsiveness to methacholine . Exposure was measured by collecting data on odor annoyance and geo-coded data on the number of animal houses within 500 m of the home . Locally optimal estimating and smoothing scatter plots were used to model the association between exposure and outcome . Analyses were restricted to subjects without private or professional contact with farming environments . Results : The prevalence of self-reported asthma symptoms and nasal allergies increased with self-reported odor annoyance . The number of animal houses was a predictor of self-reported wheeze and decreased forced expiratory volume in 1 second , but not allergic rhinitis or specific sensitization . Self-reported exposure and results of clinical measurements were poorly correlated . Conclusions : Confined animal feeding operations may contribute to the burden of respiratory disease among their neighbors . Our findings underline the importance of objective assessment of exposure and outcome in environmental epidemiology Numerous articles have been published regarding the adverse respiratory health consequences of working in intensive livestock and poultry housing . Threshold limit exposure guidelines are not currently applied to this environment , but they are essential to implement and monitor effective environmental controls . Previous dose-response research work with swine workers has result ed in exposure limit recommendations of 2.5 mg/m3 total dust , 0.23 mg/m3 respirable dust , 100 EU/m3 endotoxin , and 7 ppm ammonia . No similar recommendations have been reported previously for poultry workers . Therefore , an industry-wide study was conducted to examine dose-response relationships of bioaerosol exposures and worker respiratory health .  A total of 257 poultry workers were studied for respiratory symptoms , pulmonary function , and exposure to dust ( total and respirable ) , endotoxin ( respirable and total ) , and ammonia .  Details of the sampling plan and environmental assessment are described elsewhere . Relationships between exposures and response were studied by correlation and multiple regressions . Significant dose-response relationships were observed between exposures and pulmonary function decrements over a work shift . Exposure concentrations associated with significant pulmonary function decrements were as follows : 2.4 mg/m3 total dust , 0.16 mg/m3 respirable dust , 614 EU/m3 endotoxin , and 12 ppm ammonia BACKGROUND Exposure to swine dust leads to an intense airway inflammation and increased bronchial responsiveness . The purpose of the present study was to evaluate the effect of a respiratory protection device during exposure in a swine house . METHODS Twenty-two subjects , 11 with a respirator , were exposed . Symptoms , body temperature , nasal lavage , and a bronchial metacholine challenge were performed before and 7 hr after exposure . For exposure assessment a nasal sample r was evaluated . RESULTS The subjects with a respirator showed an attenuated inflammatory nasal response . An increase in bronchial responsiveness was observed in both groups , significantly greater in the unprotected group . The use of respirators reduced endotoxin exposure by more than 90 % ( assessed by nasal sample rs ) . CONCLUSION The use of a respirator attenuated the inflammatory response compared with an unprotected group . The minor effect on bronchial responsiveness suggests that gases and /or ultrafine particles may also be important factors Testing of lung function and bronchial reactivity , bronchoalveolar lavage ( BAL ) , and a skin prick test with a st and ard panel and six " swine " extracts obtained from swine and swine environment were performed in 20 r and omly selected nonsmoking swine confinement workers . In addition , blood sample s for detection of antibodies by the diffusion in gel-enzyme-linked immunosorbent assay ( DIG-ELISA ) technique and precipitating antibodies were drawn . Air sample s for measurement of dust and endotoxin levels were collected . All the farmers regarded themselves as healthy . The results were compared with reference groups consisting of urban nonsmoking subjects who had not been exposed to pig farming environment . The pig farmers had normal lung function and the bronchial reactivity was not different from the reference group . In the BAL fluid of the farmers , the concentration of total cells and granulocytes was increased while the concentrations of lymphocytes and macrophages were normal . The BAL fluid concentrations of albumin , fibronectin , and hyaluronan were elevated in the farmers . Skin prick tests with swine extracts  were negative in all farmers . Antibodies ( assessed by DIG-ELISA ) against swine d and er , swine dust , and pig feed were increased and precipitating antibodies against swine d and er were found in 14 , against pig food in five , and against swine confinement dust in three of the 20 pig farmers . The concentration of airborne total dust was 7.4 mg/cu mm and the endotoxin concentration was 37 ( 22 to 60 ) ng/cu mm during tending the pigs and increased , during feeding , to 13.8 mg/cu mm and 315 ( 194 to 716 ) ng/cu mm , respectively . There was no correlation between exposure and lung function or lavage findings . In conclusion , r and omly selected pig farmers had signs of airway inflammatory reaction and activation of the immune system without alteration in lung function and bronchial reactivity A crossover trial was conducted to evaluate the acute human health effects of a dust control technology in a swine confinement facility . Twenty lifetime nonsmoking male subjects , with no evidence of allergy or asth 
    Output:
    
The majority of occupational studies found a negative impact on respiratory health outcomes and increases in inflammatory biomarkers among farm workers exposed to bioaerosols .
Studies investigating the health of communities living near intensive farms had mixed findings .
The review indicated a potential impact of intensive farming on childhood respiratory health  , based on a small number of studies using self-reported outcomes , but supported by findings from occupational studies .