Prevalence of chronic obstructive pulmonary disease among US working adults aged 40 to 70 years. National Health Interview Survey data 2004 to 2011.

OBJECTIVE: To estimate the prevalence and prevalence odds ratios of chronic obstructive pulmonary disease (COPD) among US workers by major occupational groups. METHODS: The 2004 to 2011 National Health Interview Survey data for working adults 40 to 70 years old was analyzed to estimate the prevalence of COPD by major occupational groups. Logistic regression models were used to evaluate the associations between COPD (chronic bronchitis or emphysema) and occupations. RESULTS: The estimated overall COPD prevalence was 4.2% (95% CI, 4.0 to 4.3). The odds of COPD were highest among workers in health care support occupations (prevalence odds ratio, 1.64; 95% CI, 1.25 to 2.14) followed by food preparation and serving-related occupations (prevalence odds ratio, 1.57; 95% CI, 1.20 to 2.06). CONCLUSIONS: Prevalence varied by occupations, suggesting workplace exposures may contribute to COPD. Preventive measures such as interventions to reduce smoking may reduce the prevalence of COPD.

Occupational risk factors for COPD phenotypes in the Multi-Ethnic Study of Atherosclerosis (MESA) Lung Study.

INTRODUCTION: The contribution of occupational exposure to the risk of chronic obstructive pulmonary disease COPD in population-based studies is of interest. We compared the performance of self-reported exposure to a newly developed JEM in exposure-response evaluation. METHODS: We used cross-sectional data from Multi-Ethnic Study of Atherosclerosis (MESA), a population-based sample of 45-84 year olds free of clinical cardiovascular disease at baseline. MESA ascertained the most recent job and employment, and the MESA Lung Study measured spirometry, and occupational exposures for 3686 participants. Associations between health outcomes (spirometry defined airflow limitation and Medical Research Council-defined chronic bronchitis) and occupational exposure [self-reported occupational exposure to vapor-gas, dust, or fumes (VGDF), severity of exposure, and a job-exposure matrix (JEM)-derived score] were evaluated using logistic regression models adjusted for non-occupational risk factors. RESULTS: The prevalence of airflow limitation was associated with self-reported exposure to vapor-gas (OR 2.6, 95%CI 1.1-2.3), severity of VGDF exposure (P-trend < 0.01), and JEM dust exposure (OR 2.4, 95%CI 1.1-5.0), and with organic dust exposure in females; these associations were generally of greater magnitude among never smokers. The prevalence of chronic bronchitis and wheeze was associated with exposure to VGDF. The association between airflow limitation and the combined effect of smoking and VGDF exposure showed an increasing trend. Self-reported vapor-gas, dust, fumes, years and severity of exposure were associated with increased prevalence of chronic bronchitis and wheeze (P < 0.001). CONCLUSIONS: Airflow limitation was associated with self-reported VGDF exposure, its severity, and JEM-ascertained dust exposure in smokers and never-smokers in this multiethnic study.

Pesticide use and fatal injury among farmers in the Agricultural Health Study.

PURPOSE: To assess whether pesticide use practices were associated with injury mortality among 51,035 male farmers from NC and IA enrolled in the Agricultural Health Study. METHODS: We used Cox proportional hazards models adjusted for age and state to estimate fatal injury risk associated with self-reported use of 49 specific pesticides, personal protective equipment, specific types of farm machinery, and other farm factors collected 1-15 years preceding death. Cause-specific mortality was obtained through linkage to mortality registries. RESULTS: We observed 338 injury fatalities over 727,543 person-years of follow-up (1993-2008). Fatal injuries increased with days/year of pesticide application, with the highest risk among those with 60+ days of pesticide application annually [hazard ratio (HR) = 1.87; 95% confidence interval (CI) = 1.10, 3.18]. Chemical-resistant glove use was associated with decreased risk (HR = 0.73; 95% CI = 0.58, 0.93), but adjusting for glove use did not substantially change estimates for individual pesticides or pesticide use overall. Herbicides were associated with fatal injury, even after adjusting for operating farm equipment, which was independently associated with fatal injury. Ever use of five of 18 herbicides (2,4,5-T, paraquat, alachlor, metribuzin, and butylate) were associated with elevated risk. In addition, 2,4-D and cyanazine were associated with fatal injury in exposure-response analyses. There was no evidence of confounding of these results by other herbicides. CONCLUSION: The association between application of pesticides, particularly certain herbicides, and fatal injuries among farmers should be interpreted cautiously but deserves further evaluation, with particular focus on understanding timing of pesticide use and fatal injury.

Occupational lung disease risk and exposure to butter-flavoring chemicals after implementation of controls at a microwave popcorn plant.

OBJECTIVES: After an outbreak of severe lung disease among workers exposed to butter-flavoring chemicals at a microwave popcorn plant, we determined whether or not lung disease risk declined after implementation of exposure controls. METHODS: National Institute for Occupational Safety and Health staff performed eight serial cross-sectional medical and industrial hygiene surveys at the plant from November 2000 through August 2003. Medical surveys included standardized questionnaires and spirometry testing. Industrial hygiene surveys measured levels of production-related air contaminants, including butter-flavoring chemicals such as diacetyl. All diacetyl concentrations above detectable limits were corrected for the effects of absolute humidity and days to sample extraction. RESULTS: Ventilation and isolation of the production process resulted in one to three orders of magnitude reductions in diacetyl air concentrations in different areas of the plant. Workers with past high exposures had stable chest symptoms over time; nasal, eye, and skin irritation symptoms declined. New workers had lower symptom prevalences and higher lung function than workers with past high exposures, and they did not worsen over time. In workers who had at least three spirometry tests, those with past high exposures were more likely to experience rapid declines in lung function than new workers. CONCLUSIONS: Implemented controls lowered exposures to butter-flavoring chemicals and decreased lung disease risk for much of the plant workforce. Some workers with continuing potential for intermittent, short-term peak and measurable time-weighted exposures remain at risk and should use respiratory protection and have regularly scheduled spirometry to detect rapid lung function declines that may be work-related. Close follow-up of such workers is likely to yield additional information on risks due to peak and time-weighted exposure levels.

Correcting diacetyl concentrations from air samples collected with NIOSH method 2557.

Diacetyl (2,3-butanedione), a diketone chemical used to impart a buttery taste in many flavoring mixtures, has been associated with bronchiolitis obliterans in several industrial settings. For workplace evaluations in 2000-2006, National Institute for Occupational Safety and Health (NIOSH) investigators used NIOSH Method 2557, a sampling and analytical method for airborne diacetyl utilizing carbon molecular sieve sorbent tubes. The method was subsequently suspected to progressively underestimate diacetyl concentrations with increasing sampling site humidity. Since underestimation of worker exposure may lead to overestimation of respiratory health risk in quantitative exposure-effect analyses, correction of the diacetyl concentrations previously reported with Method 2557 is essential. We studied the effects of humidity and sample storage duration on recovery of diacetyl from experimental air samples taken from a dynamically generated controlled test atmosphere that allowed control of diacetyl concentration, temperature, relative humidity, sampling duration, and sampling flow rate. Samples were analyzed with Method 2557, and results were compared with theoretical test atmosphere diacetyl concentration. After fitting nonlinear models to the experimental data, we found that absolute humidity, diacetyl concentration, and days of sample storage prior to extraction affected diacetyl recovery as did sampling flow rate to a much smaller extent. We derived a mathematical correction procedure to more accurately estimate historical workplace diacetyl concentration based on laboratory-reported concentrations of diacetyl using Method 2557, and sample site temperature and relative humidity (to calculate absolute humidity), as well as days of sample storage prior to extraction in the laboratory. With this correction procedure, quantitative risk assessment for diacetyl can proceed using corrected exposure levels for air samples previously collected and analyzed using NIOSH Method 2557 for airborne diacetyl.

Identification and measurement of diacetyl substitutes in dry bakery mix production.

In 2008, a company using multiple buttermilk flavorings in the production of dry bakery mixes replaced one liquid flavoring containing 15-20% diacetyl with a proprietary substitute meant to lower occupational risk for diacetyl-related bronchiolitis obliterans. Subsequently, the National Institute for Occupational Safety and Health (NIOSH) evaluated buttermilk flavoring-related exposures at this company's facility, with a focus on measuring ketones by several methods. Volatile organic compounds (VOCs) were evaluated in the headspaces of six bulk flavorings samples, including the substitute buttermilk flavoring. Ketones were evaluated in workplace air via area and personal samples collected during batch preparation of the substitute buttermilk flavoring and production of a bakery mix containing the same flavoring. Air samples were evaluated using five different methods: NIOSH 2549, Modified OSHA PV2118, OSHA 1013, NIOSH Draft Procedure SMP2, and evacuated canisters. Of five buttermilk flavorings from five different flavorings manufacturers, diacetyl was present in four, including the substitute flavoring; acetoin in two; 2,3-pentanedione in four; 2,3-hexanedione in one; and 2,3-heptanedione in three. Among material safety data sheets (MSDS) for four flavorings, only one listed a hazardous ingredient, which was acetoin. The predominant flavoring ingredient identified in the headspace of the substitute flavoring was 2,3-pentanedione; all other chemicals noted above were also present. Diacetyl and 2,3-pentanedione were measured in workplace air via evacuated canisters. In one area and one personal air sample, 2,3-pentanedione was measured by OSHA Method 1013 at concentrations of 78 and 91 ppb, respectively. Without their or the employer's knowledge, workers who used buttermilk flavorings were exposed to substitute ketones from many flavorings manufacturers. Because 2,3-pentanedione, 2,3-hexanedione, and 2,3-heptanedione all share the same functional α-diketone group as diacetyl, these compounds also may share diacetyl's mechanism of toxicity. Until more is known about 2,3-pentanedione and other α-diketone compounds, they should not be assumed to be safe. Companies using artificial buttermilk flavorings should use a precautionary approach that assumes these flavorings pose a health risk and limit exposures through engineering and administrative controls and use of personal protective equipment.

Mortality in the agricultural health study, 1993-2007.

Comparing agricultural cohorts with the general population is challenging because the general healthiness of farmers may mask potential adverse health effects of farming. Using data from the Agricultural Health Study, a cohort of 89,656 pesticide applicators and their spouses (N = 89, 656) in North Carolina and Iowa, the authors computed standardized mortality ratios (SMRs) comparing deaths from time of the enrollment (1993-1997) through 2007 to state-specific rates. To compensate for the cohort's overall healthiness, relative SMRs were estimated by calculating the SMR for each cause relative to the SMR for all other causes. In 1,198,129 person-years of follow-up, 6,419 deaths were observed. The all-cause mortality rate was less than expected (SMR(applicators) = 0.54, 95% confidence interval (CI): 0.52, 0.55; SMR(spouses) = 0.52, 95% CI: 0.50, 0.55). SMRs for all cancers, heart disease, and diabetes were significantly below 1.0. In contrast, applicators experienced elevated numbers of machine-related deaths (SMR = 4.15, 95% CI: 3.18, 5.31), motor vehicle nontraffic accidents (SMR = 2.80, 95% CI: 1.81, 4.14), and collisions with objects (SMR = 2.12, 95% CI: 1.25, 3.34). In the relative SMR analysis for applicators, the relative mortality ratio was elevated for lymphohematopoietic cancers, melanoma, and digestive system, prostate, kidney, and brain cancers. Among spouses, relative SMRs exceeded 1.0 for lymphohematopoietic cancers and malignancies of the digestive system, brain, breast, and ovary. Unintentional fatal injuries remain an important risk for farmers; mortality ratios from several cancers were elevated relative to other causes.

Protecting poultry workers from exposure to avian influenza viruses.

Emerging zoonotic diseases are of increasing regional and global importance. Preventing occupational exposure to zoonotic diseases protects workers as well as their families, communities, and the public health. Workers can be protected from zoonotic diseases most effectively by preventing and controlling diseases in animals, reducing workplace exposures, and educating workers. Certain avian influenza viruses are potential zoonotic disease agents that may be transmitted from infected birds to humans. Poultry workers are at risk of becoming infected with these viruses if they are exposed to infected birds or virus-contaminated materials or environments. Critical components of worker protection include educating employers and training poultry workers about occupational exposure to avian influenza viruses. Other recommendations for protecting poultry workers include the use of good hygiene and work practices, personal protective clothing and equipment, vaccination for seasonal influenza viruses, antiviral medication, and medical surveillance. Current recommendations for protecting poultry workers from exposure to avian influenza viruses are summarized in this article.

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.

Pesticide use and chronic bronchitis among farmers in the Agricultural Health Study.

BACKGROUND: Farmers have increased risk for chronic bronchitis. Few investigators have considered pesticides. METHODS: We evaluated pesticides as risk factors for chronic bronchitis using the Agricultural Health Study enrollment data on lifetime pesticide use and history of doctor-diagnosed chronic bronchitis from 20,908 private pesticide applicators, primarily farmers. RESULTS: A total of 654 farmers (3%) reported chronic bronchitis diagnosed after age 19. After adjustment for correlated pesticides as well as confounders, 11 pesticides were significantly associated with chronic bronchitis. Heptachlor use had the highest odds ratio (OR=1.50, 95% Confidence Interval (CI)=1.19, 1.89). Increased prevalence for chronic bronchitis was also seen for individuals who had a history of a high pesticide exposure event (OR=1.85, 95% CI=1.51, 2.25) and for those who also applied pesticides in off-farm jobs (OR=1.40, 95% CI=1.04, 1.88). Co-morbid asthma and current farm activities did not explain these results. CONCLUSIONS: These results provide preliminary evidence that pesticide use may increase chronic bronchitis prevalence.

Chronic bronchitis among nonsmoking farm women in the agricultural health study.

OBJECTIVE: The purpose of this study was to examine agricultural risk factors for chronic bronchitis among nonsmoking farm women. METHODS: We used self-reported enrollment data from the 21,541 nonsmoking women in the Agricultural Health Study to evaluate occupational risk factors for prevalent chronic bronchitis among farm women. Odds ratios (ORs) for chronic bronchitis for occupational exposures were adjusted for age, state, and related agricultural exposures. RESULTS: Applying manure and driving combines were independently associated with chronic bronchitis. Off-farm job exposures associated with chronic bronchitis were organic dusts, asbestos, gasoline, and solvents. Five pesticides were associated with chronic bronchitis after multivariate adjustment and sensitivity analyses: dichlorvos (OR=1.63, 95% CI=1.01, 2.61), DDT (OR=1.67, 95% CI=1.13, 2.47), cyanazine (OR=1.88, 95% CI=1.00, 3.54), paraquat (OR=1.91, 95% CI=1.02, 3.55), and methyl bromide (OR=1.82, 95% CI=1.02, 3.24). CONCLUSION: Pesticides as well as grain and dust exposures were associated with chronic bronchitis among nonsmoking farm women.

Respiratory disease in agricultural workers: mortality and morbidity statistics.

To quantify the respiratory disease burden among agricultural workers, we examined the 1988-1998 National Center for Health Statistics (NCHS) "Multiple Cause of Death Data" and the 1988-1994 Third National Health and Nutrition Examination Survey data (NHANES III). Proportionate mortality ratios (PMRs) were determined for 11 respiratory conditions among 6 agricultural groups: crop farm workers, livestock farm workers, farm managers, landscape and horticultural workers, forestry workers, and fishery workers. Prevalence ratios (PRs) were determined for 12 respiratory conditions among 3 agricultural groups: farm workers, farm managers, and other agricultural workers. Disease categories groups were based on the 9th International Classification of Diseases and the agricultural groups on the NCHS or NHANES III industry and occupation codes, respectively. Crop farm workers and livestock farm workers had significantly elevated mortality for several respiratory conditions, with mortality for hypersensitivity pneumonitis being 10 and 50 times higher than expected. Landscape and horticultural workers had significantly elevated mortality for abscess of the lung and mediastinum and chronic airways obstruction. Forestry workers had significantly elevated mortality for pulmonary tuberculosis, chronic airways obstruction, and pneumonia. Prevalence of wheeze was elevated for female farm workers, shortness of breath was elevated for farm workers who had ever smoked, and hay fever was elevated for black, non-Hispanic farm workers. Prevalence of asthma was elevated for other agricultural workers who had ever smoked. Farm workers had a PR of 173 for obstructive respiratory abnormality. Continued improvement in occupational health surveillance systems for agriculture is essential to help guide prevention efforts for respiratory disease.

Pesticides and other agricultural factors associated with self-reported farmer's lung among farm residents in the Agricultural Health Study.

BACKGROUND: Farmer's lung, or hypersensitivity pneumonitis, is an important contributor to respiratory morbidity among farmers. METHODS: Using the 1993-7 enrolment data from the Agricultural Health Study, we conducted a cross-sectional study of occupational risk factors for farmer's lung among 50,000 farmers and farm spouses in Iowa and North Carolina using hierarchical logistic regression controlling for age, state, and smoking status. Participants provided information on agricultural exposures, demographic characteristics, and medical history via self-administered questionnaires. Approximately 2% of farmers (n = 481) and 0.2% of spouses (n = 51) reported doctor-diagnosed farmer's lung during their lifetime. We assessed farmers and spouses separately due to different information on occupational exposure history. Only pesticide exposures represented lifetime exposure history, all other farm exposures represented current activities at enrolment. RESULTS: Among farmers, handling silage (OR = 1.41, 95% CI 1.10 to 1.82), high pesticide exposure events (OR = 1.75, 95% CI 1.39 to 2.21), and ever use of organochlorine (OR = 1.34, 95% CI 1.04 to 1.74) and carbamate pesticides (OR = 1.32, 95% CI 1.03 to 1.68) were associated with farmer's lung in mutually-adjusted models. The insecticides DDT, lindane, and aldicarb were positively associated with farmer's lung among farmers. Current animal exposures, while not statistically significant, were positively associated with farmer's lung, particularly for poultry houses (OR = 1.55, 95% CI 0.93 to 2.58) and dairy cattle (OR = 1.28, 95% CI 0.86 to 1.89). The occupational data were more limited for spouses; however, we saw similar associations for dairy cattle (OR = 1.50, 95% CI 0.72 to 3.14) and organochlorine pesticides (OR = 1.29, 95% CI 0.64 to 2.59). CONCLUSION: While historic farm exposures may contribute to the observed associations with pesticides, these results suggest that organochlorine and carbamate pesticides should be further evaluated as potential risk factors for farmer's lung

Diacetyl emissions and airborne dust from butter flavorings used in microwave popcorn production.

In microwave popcorn workers, exposure to butter flavorings has been associated with fixed obstructive lung disease resembling bronchiolitis obliterans. Inhalation toxicology studies have shown severe respiratory effects in rats exposed to vapors from a paste butter flavoring, and to diacetyl, a diketone found in most butter flavorings. To gain a better understanding of worker exposures, we assessed diacetyl emissions and airborne dust levels from butter flavorings used by several microwave popcorn manufacturing companies. We heated bulk samples of 40 different butter flavorings (liquids, pastes, and powders) to approximately 50 degrees C and used gas chromatography, with a mass selective detector, to measure the relative abundance of volatile organic compounds emitted. Air sampling was conducted for diacetyl and for total and respirable dust during the mixing of powder, liquid, or paste flavorings with heated soybean oil at a microwave popcorn plant. To further examine the potential for respiratory exposures to powders, we measured dust generated during different simulated methods of manual handling of several powder butter flavorings. Powder flavorings were found to give off much lower diacetyl emissions than pastes or liquids. The mean diacetyl emissions from liquids and pastes were 64 and 26 times larger, respectively, than the mean of diacetyl emissions from powders. The median diacetyl emissions from liquids and pastes were 364 and 72 times larger, respectively, than the median of diacetyl emissions from powders. Fourteen of 16 powders had diacetyl emissions that were lower than the diacetyl emissions from any liquid flavoring and from most paste flavorings. However, simulated handling of powder flavorings showed that a substantial amount of the airborne dust generated was of respirable size and could thus pose its own respiratory hazard. Companies that use butter flavorings should consider substituting flavorings with lower diacetyl emissions and the use of ventilation and enclosure engineering controls to minimize exposures. Until controls are fully implemented, companies should institute mandatory respiratory protection for all exposed workers.

Evaluation of flavorings-related lung disease risk at six microwave popcorn plants.

OBJECTIVE: After investigating fixed airways obstruction in butter flavoring-exposed workers at a microwave popcorn plant, we sought to further characterize lung disease risk from airborne butter-flavoring chemicals. METHODS: We analyzed data from medical and environmental surveys at six microwave popcorn plants (including the index plant). RESULTS: Respiratory symptom and airways obstruction prevalences were higher in oil and flavorings mixers with longer work histories and in packaging-area workers near nonisolated tanks of oil and flavorings. Workers were affected at five plants, one with mixing-area exposure to diacetyl (a butter-flavoring chemical with known respiratory toxicity potential) as low as 0.02 ppm. CONCLUSIONS: Microwave popcorn workers at many plants are at risk for flavoring-related lung disease. Peak exposures may be hazardous even when ventilation maintains low average exposures. Respiratory protection and engineering controls are necessary to protect workers.

Characterization of respiratory exposures at a microwave popcorn plant with cases of bronchiolitis obliterans.

Eight former workers from a microwave popcorn packaging plant were reported to have severe obstructive lung disease consistent with bronchiolitis obliterans. Investigations into respiratory exposures at this plant were done during August through November of 2000. Samples were collected to assess airborne particulate concentrations, particle size distributions, endotoxins, oxides of nitrogen, organic gases and vapors, and other analytes. Bulk corn and flavoring components were also analyzed for endotoxins and culturable bacteria and fungi. Workers in the microwave production areas of the plant were exposed to particulates and a range of organic vapors from flavorings. The particles were comprised largely of salt and oil/grease particles. Respirable dust concentrations (area plus personal) in the microwave mixer job category, the highest job exposure category in the plant, ranged from 0.13 milligrams per cubic meter of air (mg/m3) to a high of 0.77 mg/m3. Endotoxin concentrations were below 60 endotoxin units per cubic meter of air (EU/m3). Qualitative sampling for volatile organic compounds (VOCs) in the air detected over 100 different VOCs in the microwave area. The predominant compounds identified in the microwave mixing room included the ketones diacetyl, methyl ethyl ketone, acetoin, and 2-nonanone, and acetic acid. Diacetyl, the predominant ketone in the plant, was present in concentrations ranging from below detectable limits to 98 parts per million parts air by volume (ppm), with a mean of 8.1 ppm (standard deviation 18.5 ppm). The average ketone concentrations were highest in the microwave mixing room where the 10 area samples had a mean diacetyl concentration of 37.8 ppm (SD 27.6 ppm) and a mean acetoin concentration of 3.9 ppm (SD 4.3 ppm). These data show that workers involved in microwave popcorn packaging can be exposed to a complex mixture of VOCs from flavoring ingredients; animal studies show that diacetyl can cause airway epithelial injury, although the contributions of other specific compound(s) associated with obstructive respiratory disease in these workers is still unresolved.

Clinical bronchiolitis obliterans in workers at a microwave-popcorn plant.

BACKGROUND: In May 2000, eight persons who had formerly worked at a microwave-popcorn production plant were reported to have severe bronchiolitis obliterans. No recognized cause was identified in the plant. Therefore, we medically evaluated current employees and assessed their occupational exposures. METHODS: Questionnaire responses and spirometric findings in participating workers were compared with data from the third National Health and Nutrition Examination Survey, after adjustment for age and smoking status. We evaluated the relation between exposures and health-related outcomes by analyzing the rates of symptoms and abnormalities according to current and cumulative exposure to diacetyl, the predominant ketone in artificial butter flavoring and in the air at the plant. RESULTS: Of the 135 current workers at the plant, 117 (87 percent) completed the questionnaire. These 117 workers had 2.6 times the expected rates of chronic cough and shortness of breath, according to comparisons with the national data, and twice the expected rates of physician-diagnosed asthma and chronic bronchitis. Overall, the workers had 3.3 times the expected rate of airway obstruction; those who had never smoked had 10.8 times the expected rate. Workers directly involved in the production of microwave popcorn had higher rates of shortness of breath on exertion and skin problems that had developed since they started work than workers in other parts of the plant. There was a strong relation between the quartile of estimated cumulative exposure to diacetyl and the frequency and extent of airway obstruction. CONCLUSIONS: The excess rates of lung disease and lung-function abnormalities and the relation between exposure and outcomes in this working population indicate that they probably had occupational bronchiolitis obliterans caused by the inhalation of volatile butter-flavoring ingredients.