[Two cases of airway dysfunction related to diacetyl exposure].

Occupational exposure to diacetyl can lead to bronchiolitis obliterans. In this paper, two patients with severe obstructive ventilation disorder who were exposed to diacetyl at a fragrance and flavours factory were analyzed. The clinical manifestations were cough and shortness of breath. One of them showed Mosaic shadows and uneven perfusion in both lungs on CT, while the other was normal. Field investigation found that 4 of the 8 workers in the factory were found to have obstructive ventilation disorder, and 2 had small airway dysfunction. This paper summarizes the diagnostic process of patients in order to improve the understanding of airway dysfunction caused by occupational exposure to diacetyl and promote the development of relevant standards.

A Strategy for Field Evaluations of Exposures and Respiratory Health of Workers at Small- to Medium-Sized Coffee Facilities.

Coffee production is a global industry with roasteries throughout the world. Workers in this industry are exposed to complex mixtures of gases, dusts, and vapors including carbon monoxide, carbon dioxide, coffee dust, allergens, alpha-diketones, and other volatile organic compounds (VOCs). Adverse respiratory health outcomes such as respiratory symptoms, reduced pulmonary function, asthma, and obliterative bronchiolitis can occur among exposed workers. In response to health hazard evaluations requests received from 17 small- to medium-sized coffee facilities across the United States, the National Institute for Occupational Safety and Health conducted investigations during 2016-2017 to understand the burden of respiratory abnormalities, exposure characteristics, relationships between exposures and respiratory effects, and opportunities for exposure mitigation. Full-shift, task-based, and instantaneous personal and area air samples for diacetyl, 2,3-pentanedione and other VOCs were collected, and engineering controls were evaluated. Medical evaluations included questionnaire, spirometry, impulse oscillometry, and fractional exhaled nitric oxide. Exposure and health assessments were conducted using standardized tools and approaches, which enabled pooling data for aggregate analysis. The pooled data provided a larger population to better address the requestors' concern of the effect of exposure to alpha-diketones on the respiratory heath of coffee workers. This paper describes the rationale for the exposure and health assessment strategy, the approach used to achieve the study objectives, and its advantages and limitations.

Diacetyl exposure disrupts iron homeostasis in animals and cells.

OBJECTIVE: Several mechanisms have been proposed for the biological effect of diacetyl. We tested the postulate that animal and cell exposures to diacetyl are associated with a disruption in iron homeostasis. MATERIALS AND METHODS: Male, Sprague-Dawley rats were intratracheally-instilled with either distilled water or diacetyl. Seven days after treatment, animals were euthanized and the lungs removed, fixed, and embedded. Sections were cut and stained for iron, collagen, and ferritin. Human epithelial (BEAS-2B) and monocytic (THP-1) cells were exposed in vitro to ferric ammonium citrate (FAC), diacetyl, and both FAC and diacetyl. Cell non-heme iron concentrations and ferritin levels were quantified using inductively coupled plasma optical emission spectroscopy and an immunoassay respectively. RESULTS: After exposure of animals to diacetyl, there were airway polypoid lesions which stained positively for both iron and the intracellular storage protein ferritin. Trichrome stain showed a deposition of collagen immediately adjacent to accumulated metal following diacetyl exposure. In in vitro cell exposures, FAC increased non-heme iron concentration but co-incubations of FAC and diacetyl elevated levels to significantly greater values. Levels of ferritin were increased with exposures of BEAS-2B and THP-1 cells to FAC but were similarly greater after co-exposure with FAC and diacetyl. CONCLUSIONS: Results of animal and cell studies support a disruption of iron homeostasis by diacetyl. It is proposed that, following internalization, diacetyl complexes intracellular sources of iron. The cell recognizes a loss of its requisite iron to diacetyl and imports greater concentrations of the metal.

Case Report: Flavoring-Related Lung Disease in a Coffee Roasting and Packaging Facility Worker With Unique Lung Histopathology Compared With Previously Described Cases of Obliterative Bronchiolitis.

Occupational exposure to diacetyl, a butter flavor chemical, can result in obliterative bronchiolitis. Obliterative bronchiolitis is characterized by exertional dyspnea, fixed airflow obstruction, and histopathologic constrictive bronchiolitis, with bronchiolar wall fibrosis leading to luminal narrowing and obliteration. We describe a case of advanced lung disease with histopathology distinct from obliterative bronchiolitis in a 37-year-old male coffee worker following prolonged exposure to high levels of diacetyl and the related compound 2,3-pentanedione, who had no other medical, avocational, or occupational history that could account for his illness. He began working at a coffee facility in the flavoring room and grinding area in 2009. Four years later he moved to the packaging area but continued to flavor and grind coffee at least 1 full day per week. He reported chest tightness and mucous membrane irritation when working in the flavoring room and grinding area in 2010. Beginning in 2014, he developed dyspnea, intermittent cough, and a reduced sense of smell without a work-related pattern. In 2016, spirometry revealed a moderate mixed pattern that did not improve with bronchodilator. Thoracoscopic lung biopsy results demonstrated focal mild cellular bronchiolitis and pleuritis, and focal peribronchiolar giant cells/granulomas, but no evidence of constrictive bronchiolitis. Full-shift personal air-samples collected in the flavoring and grinding areas during 2016 measured diacetyl concentrations up to 84-fold higher than the recommended exposure limit. Medical evaluations indicate this worker developed work-related, airway-centric lung disease, most likely attributable to inhalational exposure to flavorings, with biopsy findings not usual for obliterative bronchiolitis. Clinicians should be aware that lung pathology could vary considerably in workers with suspected flavoring-related lung disease.

Risk assessment of inhaled diacetyl from electronic cigarette use among teens and adults.

Diacetyl (C4H6O2) is a toxicant commonly found in electronic cigarettes (e-Cigs) as a flavoring component and an enhancer of e-juices. Lung injury in current and former workers in popcorn manufacturing suggests a possible association with diacetyl inhalation exposure. Although the number of e-Cig users continues to rise steadily among the teens and adults, the potential risk of pulmonary disease has not been characterized. A systematic review of the open literature identified bronchiolitis obliterans-a pathological inflammation resulting in fibrosis of the bronchioles leading to an irreversible limitation to airflow in lungs-as the primary outcome of diacetyl exposures. Following the deterministic United States National Research Council/Environmental Protection Agency's risk assessment framework, that consists of four key steps: hazard identification, dose-response assessment, exposure assessment and risk characterization, we estimated noncarcinogenic (systemic) risks using a Hazard Quotient (HQ) approach upon exposure to diacetyl among teens and adults who use e-Cigs. Based on the NIOSH Benchmark Dose (BMD; 0.0175 mg/kg-day) and modelled Average Daily Doses (ADDs; range 0.11-5.2 mg/kg-day), we estimated 12 different HQ values-a measure of non-carcinogenic risk for diacetyl inhalation exposures-all of which were greater than 1 (range 6.2875-297.1429), suggesting a significantly higher non-carcinogenic risk from diacetyl exposures among the teens and adults who use e-Cigs. These results underscore the need to regulate e-Cigs to protect teens and adults from diacetyl exposures and risk of developing lung injuries, including bronchiolitis obliterans.

Diacetyl odor shortens longevity conferred by food deprivation in C. elegans via downregulation of DAF-16/FOXO.

Dietary restriction extends lifespan in various organisms by reducing the levels of both nutrients and non-nutritional food-derived cues. However, the identity of specific food-derived chemical cues that alter lifespan remains unclear. Here, we identified several volatile attractants that decreased the longevity on food deprivation, a dietary restriction regimen in Caenorhabditis elegans. In particular, we found that the odor of diacetyl decreased the activity of DAF-16/FOXO, a life-extending transcription factor acting downstream of insulin/IGF-1 signaling. We then demonstrated that the odor of lactic acid bacteria, which produce diacetyl, reduced the nuclear accumulation of DAF-16/FOXO. Unexpectedly, we showed that the odor of diacetyl decreased longevity independently of two established diacetyl receptors, ODR-10 and SRI-14, in sensory neurons. Thus, diacetyl, a food-derived odorant, may shorten food deprivation-induced longevity via decreasing the activity of DAF-16/FOXO through binding to unidentified receptors.

Exposures and Emissions in Coffee Roasting Facilities and Cafés: Diacetyl, 2,3-Pentanedione, and Other Volatile Organic Compounds.

Roasted coffee and many coffee flavorings emit volatile organic compounds (VOCs) including diacetyl and 2,3-pentanedione. Exposures to VOCs during roasting, packaging, grinding, and flavoring coffee can negatively impact the respiratory health of workers. Inhalational exposures to diacetyl and 2,3-pentanedione can cause obliterative bronchiolitis. This study summarizes exposures to and emissions of VOCs in 17 coffee roasting and packaging facilities that included 10 cafés. We collected 415 personal and 760 area full-shift, and 606 personal task-based air samples for diacetyl, 2,3-pentanedione, 2,3-hexanedione, and acetoin using silica gel tubes. We also collected 296 instantaneous activity and 312 instantaneous source air measurements for 18 VOCs using evacuated canisters. The highest personal full-shift exposure in part per billion (ppb) to diacetyl [geometric mean (GM) 21 ppb; 95th percentile (P95) 79 ppb] and 2,3-pentanedione (GM 15 ppb; P95 52 ppb) were measured for production workers in flavored coffee production areas. These workers also had the highest percentage of measurements above the NIOSH Recommended Exposure Limit (REL) for diacetyl (95%) and 2,3-pentanedione (77%). Personal exposures to diacetyl (GM 0.9 ppb; P95 6.0 ppb) and 2,3-pentanedione (GM 0.7 ppb; P95 4.4 ppb) were the lowest for non-production workers of facilities that did not flavor coffee. Job groups with the highest personal full-shift exposures to diacetyl and 2,3-pentanedione were flavoring workers (GM 34 and 38 ppb), packaging workers (GM 27 and 19 ppb) and grinder operator (GM 26 and 22 ppb), respectively, in flavored coffee facilities, and packaging workers (GM 8.0 and 4.4 ppb) and production workers (GM 6.3 and 4.6 ppb) in non-flavored coffee facilities. Baristas in cafés had mean full-shift exposures below the RELs (GM 4.1 ppb diacetyl; GM 4.6 ppb 2,3-pentanedione). The tasks, activities, and sources associated with flavoring in flavored coffee facilities and grinding in non-flavored coffee facilities, had some of the highest GM and P95 estimates for both diacetyl and 2,3-pentanedione. Controlling emissions at grinding machines and flavoring areas and isolating higher exposure areas (e.g., flavoring, grinding, and packaging areas) from the main production space and from administrative or non-production spaces is essential for maintaining exposure control.

Accumulation of Ubiquitin and Sequestosome-1 Implicate Protein Damage in Diacetyl-Induced Cytotoxicity.

Inhaled diacetyl vapors are associated with flavorings-related lung disease, a potentially fatal airway disease. The reactive α-dicarbonyl group in diacetyl causes protein damage in vitro. Dicarbonyl/l-xylulose reductase (DCXR) metabolizes diacetyl into acetoin, which lacks this α-dicarbonyl group. To investigate the hypothesis that flavorings-related lung disease is caused by in vivo protein damage, we correlated diacetyl-induced airway damage in mice with immunofluorescence for markers of protein turnover and autophagy. Western immunoblots identified shifts in ubiquitin pools. Diacetyl inhalation caused dose-dependent increases in bronchial epithelial cells with puncta of both total ubiquitin and K63-ubiquitin, central mediators of protein turnover. This response was greater in Dcxr-knockout mice than in wild-type controls inhaling 200 ppm diacetyl, further implicating the α-dicarbonyl group in protein damage. Western immunoblots demonstrated decreased free ubiquitin in airway-enriched fractions. Transmission electron microscopy and colocalization of ubiquitin-positive puncta with lysosomal-associated membrane proteins 1 and 2 and with the multifunctional scaffolding protein sequestosome-1 (SQSTM1/p62) confirmed autophagy. Surprisingly, immunoreactive SQSTM1 also accumulated in the olfactory bulb of the brain. Olfactory bulb SQSTM1 often congregated in activated microglial cells that also contained olfactory marker protein, indicating neuronophagia within the olfactory bulb. This suggests the possibility that SQSTM1 or damaged proteins may be transported from the nose to the brain. Together, these findings strongly implicate widespread protein damage in the etiology of flavorings-related lung disease.

Diacetyl and 2,3-pentanedione exposure of human cultured airway epithelial cells: Ion transport effects and metabolism of butter flavoring agents.

Inhalation of butter flavoring by workers in the microwave popcorn industry may result in "popcorn workers' lung." In previous in vivo studies rats exposed for 6 h to vapor from the flavoring agents, diacetyl and 2,3-pentanedione, acquired flavoring concentration-dependent damage of the upper airway epithelium and airway hyporeactivity to inhaled methacholine. Because ion transport is essential for lung fluid balance,we hypothesized that alterations in ion transport may be an early manifestation of butter flavoring-induced toxicity.We developed a system to expose cultured human bronchial/tracheal epithelial cells (NHBEs) to flavoring vapors. NHBEs were exposed for 6 h to diacetyl or 2,3-pentanedione vapors (25 or ≥ 60 ppm) and the effects on short circuit current and transepithelial resistance (Rt) were measured. Immediately after exposure to 25 ppm both flavorings reduced Na+ transport,without affecting Cl- transport or Na+,K+-pump activity. Rt was unaffected. Na+ transport recovered 18 h after exposure. Concentrations (100-360 ppm) of diacetyl and 2,3-pentanedione reported earlier to give rise in vivo to epithelial damage, and 60 ppm, caused death of NHBEs 0 h post-exposure. Analysis of the basolateral medium indicated that NHBEs metabolize diacetyl and 2,3-pentanedione to acetoin and 2-hydroxy-3-pentanone, respectively. The results indicate that ion transport is inhibited transiently in airway epithelial cells by lower concentrations of the flavorings than those that result in morphological changes of the cells in vivo or in vitro.

Respiratory symptoms and lung function abnormalities related to work at a flavouring manufacturing facility.

OBJECTIVES: To better understand respiratory symptoms and lung function in flavouring manufacturing workers. METHODS: We offered a questionnaire and lung function testing to the current workforce of a flavouring manufacturing facility that had transitioned away from diacetyl and towards substitutes in recent years. We examined symptoms, spirometric parameters and diffusing capacity measurements by exposure variables, including facility tenure and time spent daily in production areas. We used linear and logistic regression to develop final models adjusted for age and smoking status. RESULTS: A total of 367 (93%) current workers participated. Shortness of breath was twice as common in those with tenure ≥ 7 years (OR 2.0, 95% CI 1.1 to 3.6). Other chest symptoms were associated with time spent daily in production. Participants who spent ≥ 1 h daily in production areas had twice the odds of any spirometric abnormality (OR 2.3; 95% CI 1.1 to 5.3) and three times the odds of low diffusing capacity (OR 2.8; 95% CI 0.9 to 9.4) than other participants. Mean spirometric parameters were significantly lower in those with tenure ≥ 7 years and those who spent ≥ 1 h daily in production. Mean diffusing capacity parameters were significantly lower in those with tenure ≥ 7 years. Differences in symptoms and lung function could not be explained by age, smoking status or employment at another flavouring plant. CONCLUSIONS: Symptoms and lung function findings were consistent with undiagnosed or subclinical obliterative bronchiolitis and associated with workplace exposures. Further efforts to lower exposures to flavouring chemicals, including diacetyl substitutes, are warranted.

Is diacetyl a respiratory sensitizer? A reconsideration using QSAR, QMM, and competition experiments.

Concerns have been raised that diacetyl (DA) might be a respiratory sensitizer based on its LUMO energy similar to that of the respiratory allergen toluene-2,4-diisocyanate (TDI) and results of a local lymph node assay (LLNA) that reported an EC3 of 1.9%. To better understand the concerns, we performed a systematic literature review and experimental competition reactions between DA and TDI. The experimental evidence demonstrates that DA is at least 400-fold less reactive than TDI. The literature review finds evidence that the EC3 for DA is actually >11%. We conclude that DA is unlikely to have significant respiratory sensitization potential.

Determination of toxic α-dicarbonyl compounds, glyoxal, methylglyoxal, and diacetyl, released to the headspace of lipid commodities upon heat treatment.

Toxic α-dicarbonyl compounds, glyoxal, 2-methylglyoxal, and diacetyl, released from the headspace from butter, margarine, safflower oil, beef fat, and cheese heated at 100 and 200 °C were analyzed by gas chromatography as quinoxaline derivatives. Total amounts of α-dicarbonyl compounds ranged from 40.5 ng/g (butter) to 331.2 ng/g (beef fat) at 100 °C and from 302.4 ng/g (safflower oil) to 4521.5 ng/g (margarine) at 200 °C. The total amount of α-dicarbonyl compounds increased approximately 55- and 15-fold in the headspace of heated butter and margarine, respectively, when the temperature was increased from 100 to 200 °C. However, only slight differences associated with temperature variation were observed in the cases of safflower oil and beef fat (1.3- and 1.1-fold, respectively). Diacetyl was found in the highest amounts among all samples, ranging from 13.9 ± 0.3 ng/g (butter) to 2835.7 ng/g (cheese) at 100 °C and from 112.5 ± 102 ng/g (safflower oil) to 2274.5 ± 442.6 ng/g (margarine) at 200 °C, followed by methylglyoxal, ranging from 13.0 ± 0.5 to 112.7 ± 10.1 ng/g (cheese) at 100 °C and from 34.7 ± 5.0 ng/g (safflower oil) to 1790 ± 372.3 ng/g (margarine) at 200 °C. Much less glyoxal formed, in amounts ranging from 13.6 ± 0.7 ng/g (butter) to 53.4 ± 11.2 ng/g (beef fat) at both temperatures. The amounts of α-dicarbonyl compounds released into the vapor phase from lipid commodities during heating were satisfactorily analyzed.

Reactive skin decontamination lotion (RSDL) for the decontamination of chemical warfare agent (CWA) dermal exposure.

Rapid decontamination of the skin is the single most important action to prevent dermal absorption of chemical contaminants in persons exposed to chemical warfare agents (CWA) and toxic industrial chemicals (TICs) as a result of accidental or intentional release. Chemicals on the skin may be removed by mechanical means through the use of dry sorbents or water. Recent interest in decontamination systems which both partition contaminants away from the skin and actively neutralize the chemical has led to the development of several reactive decontamination solutions. This article will review the recently FDA-approved Reactive Skin Decontamination Lotion (RSDL) and will summarize the toxicity and efficacy studies conducted to date. Evidence of RSDL's superior performance against vesicant and organophosphorus chemical warfare agents compared to water, bleach, and dry sorbents, suggests that RSDL may have a role in mass human exposure chemical decontamination in both the military and civilian arenas.

Longitudinal lung function declines among California flavoring manufacturing workers.

BACKGROUND: The California Department of Public Health received serial spirometry data for flavoring manufacturing workers at 20 companies at risk of bronchiolitis obliterans. METHODS: We graded spirometry quality; identified individual workers with excessive decline in forced expiratory volume in 1 s (FEV(1)) using relative longitudinal limits of decline based on 4% average within-person variability; and analyzed declines by occupational risk factors. RESULTS: The quality of 1,696 spirometry tests from 724 workers varied by 17 providers, with poorer quality from commercial providers. Of 416 workers with at least two tests, 40 (9.6%) had abnormal FEV(1) decline. Of 289 workers with high quality spirometry, 21 (7.3%) had abnormal decline. Only one of the 21 had airways obstruction. Abnormal FEV(1) decline rates (per person-month) were greater among workers at companies using ≥800 lbs/year diacetyl than at companies using lesser amounts. Abnormal FEV(1) decline rates were greater at companies previously having four-person clusters of spirometric obstruction than at companies with no or only one worker with obstruction. CONCLUSIONS: Spirometric surveillance of flavoring workers can identify individual workers with an abnormal FEV(1) decline for preventive intervention, even when the FEV(1) itself remains within the normal range. Good quality spirometry and classification of abnormal with relative longitudinal limit of decline minimize misclassification of possible work-related health effects.

A proposal for a safe exposure level for diacetyl.

Diacetyl is a naturally occurring compound that has been used in concentrated form as a food additive, particularly in butter flavorings. Inhalation of diacetyl and butter flavoring fumes has caused a variety of respiratory diseases in workers and consumers including bronchiolitis obliterans (BO), a relatively rare, severe, and irreversible lung disease. A safe level of exposure to diacetyl has not been established. We review the literature on diacetyl and flavoring toxicity and critique a recent proposal for an occupational exposure limit (OEL) of 0.2 ppm for diacetyl. We present unpublished data and novel analyses in support of our proposal for a safe level of exposure. Our findings indicate that a safe level of exposure exists around or below a time-weighted average of 1 ppb for an eight-hour workday. The levels of exposure we found to be unsafe include ranges that popcorn consumers may potentially be exposed to, indicating a risk of severe lung disease (including BO) for some consumers.

Reaction of the butter flavorant diacetyl (2,3-butanedione) with N-α-acetylarginine: a model for epitope formation with pulmonary proteins in the etiology of obliterative bronchiolitis.

The butter flavorant diacetyl (2,3-butanedione) is implicated in causing obliterative bronchiolitis in microwave popcorn plant workers. Because diacetyl modifies arginine residues, an immunological basis for its toxicity is under investigation. Reaction products of diacetyl with N-α-acetylarginine (AcArg) were determined as a model for hapten formation, with characterization by mass spectrometry, NMR, and HPLC with UV detection and radiodetection. Four products were identified by LC-MS, each with a positive ion of m/z 303 (diacetyl + AcArg); one pair displayed an additional ion at m/z 217 (AcArg), the other pair at m/z 285 (- H(2)O). Their (1)H-(13)C NMR correlation spectra were consistent with the addition of one or two of the guanidine nitrogens to form aminols. Open-chain pairs interconverted at pH 2, as did the cyclized, but all four interconverted at neutral pH. This is the first structural characterization of the covalent adducts between diacetyl and an arginine moiety.

Evaluation of methods to determine excessive decline of forced expiratory volume in one second in workers exposed to diacetyl-containing flavorings.

OBJECTIVE: To evaluate methods for determining excessive short-term decline in forced expiratory volume in one second (FEV1) in diacetyl-exposed workers. METHODS: We evaluated five methods of determining excessive longitudinal FEV1 decline in diacetyl-exposed workers and workers from a comparative cohort: American Thoracic Society (ATS), ACOEM an 8% limit, and a relative and absolute longitudinal limit on the basis of spirometry data variability. Relative risk and incidence of excess decline were evaluated. RESULTS: Incidence of excessive FEV1 decline was 1% in the comparative cohort using ATS and ACOEM criteria, 4.1% using relative limit of longitudinal decline, 4.4% with absolute longitudinal limit of decline, and 5.6% by using the 8% limit. Relative risk of abnormal FEV1 decline in diacetyl-exposed workers was elevated in all evaluated methods. CONCLUSION: Alternative methods for respiratory surveillance in diacetyl-exposed workers may be preferable to ATS or ACOEM.