Lessons From the Household Humidifier Disinfectant Tragedy (HHDT) With Focus on the Chemical Poisoning Surveillance System: Review and Recommendation.

BACKGROUND: Lessons learned from the Household Humidifier Disinfectant Tragedy (HHDT) in Korea, which poisoned thousands of citizens over a period of years, necessitated an examination of national poison prevention and surveillance systems. The objectives of this study are to identify essential changes needed in chemical poisoning prevention regulations and surveillance systems for effective poison control by comparing recent trends in international poison control center (PCC) operations, and to delineate the critical elements for establishing a state-of-the-art poison control surveillance system in Korea based on recent advances in PCCs with toxicovigilance. METHODS: A comprehensive review of Korea's regulatory and surveillance systems for chemical health hazards, with a focus on household products under the HHDT, was conducted. A review of toxicovigilance systems in major countries shows that creating an effective national PCC requires key elements: a centralized database of toxic substances and poisoning cases, mandatory or voluntary reporting of poisoning cases, real-time alerts, collaboration among health organizations, and targeted follow-up of poisoned individuals. RESULTS: Significant deficiencies in Korea's legislation, toxicological data management, and poisoning surveillance systems, explained the inadequate response of the Korean government to the HHDT for nearly 17 years until the end of 2011. Based on a review of PCC toxicovigilance systems in major countries, a national framework with five core components is recommended for establishing a modern comprehensive Korea PCC system with toxicovigilance capacity. The core components include establishment of a centralized database of toxic substances information and clinical poisoning cases, implementation of mandatory or permissive reporting of poisoning cases, real-time alert mechanisms, collaborative systems among health-related organizations, and clinical follow-up of poisoned sub-groups. CONCLUSION: A rationale and framework for a state-of-the-art national Korean PCC with toxicovigilance is justified and offered. This proposed system could assist neighboring countries in establishing their own sophisticated, globally integrated PCC networks.

Humidification during Invasive and Non-Invasive Ventilation: A Starting Tool Kit for Correct Setting.

The humidification process of medical gases plays a crucial role in both invasive and non-invasive ventilation, aiming to mitigate the complications arising from bronchial dryness. While passive humidification systems (HME) and active humidification systems are prevalent in routine clinical practice, there is a pressing need for further evaluation of their significance. Additionally, there is often an incomplete understanding of the operational mechanisms of these devices. The current review explores the historical evolution of gas conditioning in clinical practice, from early prototypes to contemporary active and passive humidification systems. It also discusses the physiological principles underlying humidity regulation and provides practical guidance for optimizing humidification parameters in both invasive and non-invasive ventilation modalities. The aim of this review is to elucidate the intricate interplay between temperature, humidity, and patient comfort, emphasizing the importance of individualized approaches to gas conditioning.

Synergistic interaction of co-exposure to humidifier disinfectant chemicals CMIT/MIT and PHMG in lung injury.

A number of biocidal disinfectant chemicals are used as household products to prevent spread of pathogens. People are commonly exposed to multiple chemicals through those disinfectants. However, effects of interactions (e.g., synergism) between disinfectants on human health outcomes have been rarely studied. In this study, we aimed to investigate associations of a mixture of chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) and polyhexamethylene guanidine (PHMG), which had been used as humidifier disinfectants (HDs) in South Korea, with HD-associated lung injury (HDLI) in a Korean population (n = 4058) with HD exposure through use of HD products. Exposure to HD was retrospectively assessed by an interview-based standardized survey, and HDLI was determined by clinical assessment. After adjusting for covariates, PHMG-specific exposure indices (e.g., amount of use, indoor air concentration, and weekly exposure level) were dose-dependently associated with HDLI (their odds ratios for the comparison of third tertile versus first tertile were 1.95, 1.77, and 2.16, respectively). CMIT/MIT exposure was not observed to have a significant association with HDLI in a single chemical exposure model; however, associations between PHMG exposure and HDLI were strengthened by co-exposure to CMIT/MIT in combined chemical exposure models, where synergistic interactions between CMIT/MIT use and PHMG indices (amount of use and weekly exposure level) were observed (p-interaction in additive scale: 0.02 and 0.03, respectively). Our findings imply that adverse effects of PHMG exposure on lung injury among HD users might be worsened by co-exposure to CMIT/MIT. Given that plenty of household products contain disinfectants on global markets, epidemiological and toxicological investigations are warranted on interaction effects of co-exposure to disinfectants.

Effect of Interrupting Heated Humidification on Nebulized Drug Delivery Efficiency, Temperature, and Absolute Humidity During Mechanical Ventilation: A Multi-Lab In Vitro Study.

Introduction: During mechanical ventilation (MV), inspired gases require heat and humidification. However, such conditions may be associated with reduced aerosol delivery efficiency. The practice of turning off heated humidification before nebulization and the impact of nebulization on humidity in a dry ventilator circuit remain topics of debate. This study aimed to assess the effect of turning off heated humidification on inhaled dose and humidity with nebulizer use during adult MV. Methods: A bronchodilator (albuterol) and two antibiotics (Colistimethate sodium and Amikacin sulfate) were nebulized with a vibrating mesh nebulizer placed at the humidifier inlet and in the inspiratory limb at the Y-piece. Additionally, albuterol was nebulized using a jet nebulizer in both placements. Aerosol particle size distribution was determined through a cascade impactor. Absolute humidity (AH) and temperature of inspired gases were determined with anemometer/hygrometers before, during, and after nebulization, before, during, and up to 60 minutes after interrupting active humidification. Aerosol collected on a filter distal to the endotracheal tube and on impactor stages were eluted and assayed by spectrophotometry. Results: The inhaled dose was greater when both nebulizers were placed at the humidifier inlet than the inspiratory limb at the Y-piece. Irrespective of the nebulizer types and placements, the inhaled dose either decreased or showed no significant change after the humidifier was turned off. The aerosol particle size ranged from 1.1 to 2.7 µm. With interruption of active humidification, humidity of inspired gas quickly dropped below recommended levels, and nebulization in dry ventilator circuit produced an AH between 10 and 20 mgH2O/L, lower than the recommended minimum of 30 mgH2O/L. Conclusion: Interrupting active humidification during MV before nebulization did not improve aerosol delivery efficiency for bronchodilator or antibiotics, but did reduce humidity below recommended levels.

Concordance of esophageal and tracheal temperatures in patients using breathing circuit with heated wire humidifier: A prospective observational study.

RESULTS: After excluding 4 patients with an anesthesia duration of < 2 hours, data from 34 patients (1163 sets of tracheal and esophageal temperatures) were analyzed. Concordance correlation coefficient was 0.78. The overall mean bias (95% limits of agreement) between the tracheal and esophageal temperatures was -0.16°C (-0.65°C to 0.34°C). The percentage of temperature differences within ±â€…0.25°C was 73.5% ± 32.3, with a median of 89.4% [0,100]. The linear mixed-effects model revealed that the estimated intercept was 0.17°C with a 95% confidence interval (CI) of 0.13°C to 0.22°C. The duration of anesthesia and the number of temperature measurements were associated with higher concordance between the tracheal and esophageal temperatures in univariate analysis.

Evaluation of the Humidification Performances of New Generation of Heated Wire Humidifiers.

BACKGROUND: At high ambient temperatures in ICU rooms, the humidification performances of heated-wire humidifiers are significantly reduced, with delivered gas humidity well below 30 mg H2O/L, which leads to an increased risk of endotracheal occlusions, subocclusions, or mucociliary dysfunction. The objective of the study was to evaluate the humidity delivered at the Y-piece with new-generation heated-wire humidifiers with advanced algorithm (FP950 [Fisher & Paykel Healthcare, Auckland, New Zealand] and VHB20 [Vincent Medical, Inspired, Hong Kong]) while varying ambient temperatures. METHODS: We measured, on the bench, the hygrometry of inspiratory gases delivered by a new generation of heated-wire humidifiers (i) FP950, (ii) VHB20 and a previous generation of heated-wire humidifiers, (iii) MR850 (Fisher & Paykel) with the usual settings (37°C at the chamber/40°C at the Y-piece), (iv) MR850 with no temperature gradient (40°C/40°C), and (v) MR850 with the automatic compensation algorithm activated. Hygrometry was measured with the psychrometric method after 1 h of stability while varying the room temperature from 20 to 30°C. RESULTS: Two hundred ninety-four hygrometric bench measurements were performed at steady state for the different tested conditions. With the new heated-wire humidifiers (FP950 and VHB20), gas humidity delivered remained > 30 mg H2O/L in all tested conditions, even at high ambient temperatures (>25°C). With previous generations of heated-wire humidifiers (MR850), at high ambient temperature, humidity delivered was adequate in only 26% (11/42) of the measurements when the usual settings were used (37°C/40°C) and 30% (11/37) with automatic compensation. When no temperature gradient was set (40°C/40°C), humidity delivered was > 30 mg H2O/L in 91% (30/33) of the measurements at a high ambient temperature. With an ambient temperature < 25°C, almost all devices and settings provided adequate humidity. CONCLUSIONS: The new FP950 and VHB20 heated-wire humidifiers by using advanced algorithms demonstrated stable performance while varying the ambient temperature by 20-30°C, better than the previous generation of heated humidifiers when ambient temperatures were high.

Comparison of maternal and neonatal survival exposed to humidifier disinfectants during perinatal periods: a case-series study.

A humidifier disinfectant (HD) has been prohibited by the government due to its serious effects on the human body. Several studies on the relationship between HD and lung diseases have been performed independently on children and adults. However, there have been no reports on the effects of HD exposure on pregnant women and their foetuses. Therefore, the present study was conducted to investigate the effects of HD exposure on the foetuses of women who encountered HD during pregnancy. A total of 56 cases were recruited from 2017 to 2019 through the Korea Environmental Industry & Technology Institute, and data obtained from the medical records included maternal date of birth, maternal date of death, maternal start and end date of HD exposure, maternal date of symptom onset, neonatal birthday, neonatal birthweight, gestational age, and neonatal survival status within 28 days. All data were retrospectively investigated through medical records. Of the 47 mothers, 20 (42.6%) mothers survived, and 27 (57.4%) mothers died. In the group of survivors, there was a shorter period of total HD use, period of HD use before pregnancy and period of HD use to onset of symptoms. Shorter durations of HD use resulted in higher survival rate of mothers. HD use caused an increase in gestational age surviving foetuses, and foetal mortality increased when clinical symptoms developed before birth.

Exposures to humidifier disinfectant and various health conditions in Korean based on personal exposure assessment data of claimants for compensation.

BACKGROUND: Humidifier disinfectants (HDs) were commonly used household chemicals to prevent microbial growth in a humidifier water tank in South Korea. A growing body of evidence has indicated that its airborne exposure can induce severe lung injury. However, there has been low awareness of other health outcomes in HD users. This study aimed to evaluate health conditions appealed by claimants for compensation in relation with an increased exposure to HD. METHODS: From survey data of personal HD exposure assessment of claimants for compensation in Korea, we included a total of 4,179 subjects [cases in each dataset were defined by nine reported health conditions, i.e., pneumonia, asthma, cardiovascular disease, respiratory disease, otorhinolaryngologic disease, brain disease (including cerebrovascular disease), dermatological disease, lung cancer, and all cancers]. HD exposures was considered as the following exposure criteria: exposure duration, exposure proximity, exposure direction, chemical type, cumulative exposure time, indoor air concentration, and cumulative exposure level. Logistic regression models were used to evaluate the associations between HD exposure and health conditions. RESULTS: After adjusting for sociodemographic and health behavioral factors and other chemical exposures (households, environmental, and occupational exposures), an increase in cumulative HD exposure time was significantly associated with risks of all nine diseases (all p-trends < 0.05). An increase in HD exposure duration was associated with asthma, respiratory disease, otorhinolaryngologic disease, dermatological disease, all cancers, and lung cancer (p-trends < 0.05). Indoor HD concentration was associated with only pneumonia (p-trend = 0.015). CONCLUSIONS: Our findings suggest that cumulative exposures to airborne HD might potentially increase the risk of various reported health outcomes.

Effects of psychological symptoms on life adjustment among survivors of humidifier disinfectants.

OBJECTIVES: The humidifier disinfectant catastrophe in South Korea was a social disaster caused by toxic chemical substances. The present study aimed to examine the relationships between psychological symptoms and adaptive life functioning in survivors of humidifier disinfectants. This study examined the differential effects of psychological symptoms on life adjustment between survivors of humidifier disinfectant and the general population. MATERIAL AND METHODS: A total of 452 individuals (228 general and 224 survivor groups) participated in this research. This study utilized the Adult Self-Report, one of the most widely used comprehensive mental health scales for measuring both psychological symptoms (e.g., anxiety/depression) and life adjustment functioning (e.g., interpersonal relationship). For the data analysis, multi-group structural equation modeling analysis was conducted using AMOS 21.0 program. RESULTS: The results of this study indicated that attention problems out of 8 psychological symptoms was the only significant factor related to life adjustment in both general and survivor groups. In addition, there was a significant 2-way interaction effect of group status and somatic complaints on life adjustment. CONCLUSIONS: When the somatic complaint symptom was higher, participants in the survivor group were less likely to adjust in life than the general group. Taken together, the somatic complaints of the survivors more strongly influence the life adjustment than the general population. Finally, the authors discuss practical implications for survivors of humidifier disinfectants for designing suitable intervention strategies.Int J Occup Med Environ Health. 2023;36(5):596-605.

Evidence integration on health damage for humidifier disinfectant exposure and legal presumption of causation.

OBJECTIVES: Inhalation exposure to humidifier disinfectants has resulted to various types of health damages in Korea. To determine the epidemiological correlation necessary for presuming the legal causation, we aimed to develop a method to synthesize the entire evidence. METHODS: Epidemiological and toxicological studies are systematically reviewed. Target health problems are selected by criteria such as frequent complaints of claimants. Relevant epidemiologic studies are reviewed and the risk of bias and confidence level of the total evidence are evaluated. Toxicological literature reviews are conducted on three lines of evidence including hazard information, animal studies, and mechanistic studies, considering the source-to-exposure-to-outcome continuum. The confidence level of the body of evidence is then translated into the toxicological evidence levels for the causality between humidifier disinfectant exposure and health effects. Finally, the levels of epidemiological and toxicological evidence are synthesized. RESULTS: Under the Special Act revised in 2020, if the history of exposure and the disease occurred/worsened after exposure were approved, and the epidemiological correlation between the exposure and disease was verified, the legal causation is presumed unless the company proves the evidence against it. The epidemiological correlation can be verified through epidemiological investigations, health monitoring, cohort investigations and/or toxicological studies. It is not simply as statistical association as understood in judicial precedents, but a general causation established by the evidence as a whole, i.e., through weight-of-the-evidence approach. CONCLUSIONS: The weight-of-the-evidence approach differs from the conclusive single study approach and this systematic evidence integration can be used in presumption of causation.

Recurrent episodes of febrile dyspnoea: hypersensitivity pneumonitis caused by a household ultrasonic humidifier.

Hypersensitivity pneumonitis is an immune-mediated interstitial lung disease that presents with respiratory symptoms, with or without systemic symptoms, following exposure to an identified or unidentified external factor. It can be caused by extrinsic factors including household items such as ultrasonic humidifiers.We present an intriguing case of a previously healthy 50-year-old man who displayed recurrent episodes of progressive dyspnoea and fever after repeated exposure to his household ultrasonic humidifier. He was treated with corticosteroids, followed by the removal of the humidifier, resulting in total recovery and absence of recurrence of further episodes.The clinical presentation of hypersensitivity pneumonitis can be dramatic, and the differential diagnosis is broad. The correct diagnosis is achieved by combining clinical, radiological and histopathological patterns. The key to finding the aetiology lies in a thorough history, with an important role for household investigations to identify the external factor.

ATS/JRS/ALAT Hypersensitivity Pneumonitis Guidelines for Diagnosis of humidifier lung and summer-type hypersensitivity pneumonitis.

BACKGROUND: The ATS/JRS/ALAT Guidelines for the Diagnosis of Hypersensitivity Pneumonitis (GL for HP) were published in 2020. Humidifier lung and summer-type HP are forms of HP, but it is unclear whether they can be diagnosed using GL for HP. This study examined the level of confidence where humidifier lung and summer-type HP can be diagnosed with GL for HP. METHODS: Data from 23 patients with humidifier lung and 20 patients with summer-type HP (mean age, 67.3 and 57.4 years, respectively) diagnosed between October 2012 and January 2022 were retrospectively reviewed. We evaluated high resolution computed tomography (HRCT) patterns, bronchoalveolar lavage fluid (BALF) findings, exposures, and histopathological findings to determine the level of confidence where a diagnosis of HP could be made using the GL for HP. RESULTS: HRCT pattern was classified as typical HP in 5 (22%) and compatible with HP in 18 (78%) patients with humidifier lung and considered as typical HP in 17 (85%) and compatible with HP in 3 (15%) patients with summer-type. The confidence level for diagnosis of HP was definite in 2 (8.7%), moderate in 14 (60.9%), and low in 7 (30.4%) patients with humidifier lung. It was definite in 12 (60%), high in 3 (15%), and moderate in 5 (25%) patients with summer-type HP. CONCLUSIONS: GL for HP showed utility in diagnosing humidifier lung in many patients with a moderate to low confidence. However, there was a definite to high confidence for patients with summer-type HP.

[HUMIDIFIER LUNG WITH ORGANIZING PNEUMONIA DETECTED BY BRONCHOSCOPY: A CASE REPORT].

A 58-year-old man presented with dyspnea on exertion and diffuse ground-glass opacities with mosaicism on chest computed tomography in April 201X. A transbronchial lung biopsy revealed organizing pneumonia and lymphocytic infiltration, and steroids were administered. During steroid tapering, the shortness of breath and ground-glass opacities recurred, and a transbronchial lung re-biopsy revealed organizing pneumonia without a granuloma again. Based on the clinical history, imaging features, and amount of humidifier usage, hypersensitivity pneumonitis caused by a humidifier was suspected. The inhalation challenge test was considered positive, and the diagnosis was confirmed. There have been some reports of unidentified granuloma in patients with humidifier lungs. Therefore, this case suggests that humidifier lung should be considered as a possibility even if pathological examination does not reveal granulomas and inflammatory changes such as organizing pneumonia are the only findings.

Inhalation toxicity of polyhexamethylene guanidine-phosphate in rats: A 4-week inhalation exposure and 24-week recovery period study.

Humidifier disinfectant (HD) is a causative agent of atypical lung injury reported in 2011 in South Korea, and various diseases caused by HD after exposure cessation have been reported to date. However, there is limited research on most of the reported diseases in terms of their association with HD exposure, and information on the progression of diseases caused by HD exposure is also limited. Therefore, we investigated the effects of HD inhalation on the body in rats. Rats were exposed to 0.15, 0.50, and 1.60 mg/m3 polyhexamethylene guanidine-phosphate (PHMG-p), which is the major component of HDs and most closely related to HD-associated lung injury. We conducted necropsy four times during the recovery period (0, 4, 12, and 24 weeks) and evaluated general systemic toxicities. There were significant changes in the mortality rate, body weight, and food consumption in the PHMG-p-exposed groups. Hematology revealed changes in hemoglobin level, hematocrit, red blood cell, reticulocyte, and white blood cell counts until 12 weeks of the recovery period. PHMG-p induced a delay in prothrombin time until 12 weeks of the recovery period. The aspartate aminotransferase, alanine aminotransferase, total bilirubin, and triglyceride levels were higher in the PHMG-p-exposed groups than in the control group at week 4 of the recovery period, and these parameters normalized after 12 weeks of the recovery period. Histopathological examination in PHMG-p exposed groups revealed several changes in the lungs, including the presence of alveolar macrophages, chronic inflammation, squamous metaplasia, alveolar emphysema, and pulmonary fibrosis. The severity of these symptoms was maintained or exacerbated till 24 weeks. Overall, PHMG-p inhalation can induce irreversible histological changes in the lungs and cause various types of damage throughout the body, even after exposure ends.

Environmental risks from consumer products: Acceptable drinking water quality can produce unacceptable indoor air quality with ultrasonic humidifier use.

The commonly used consumer product of an ultrasonic humidifier (e.g., cool mist humidifier) emits fine particles containing metals from tap water used to fill the humidifier. The objectives are: 1) predict emitted indoor air inhalable metal concentrations produced by an ultrasonic humidifier filled with tap-water containing As, Cd, Cr, Cu, Mn, and Pb in 33 m3 or 72 m3 rooms with varying air exchange rates; 2) calculate daily ingestion and 8-h inhalation average daily dose (ADD) and hazard quotient (HQ) for adults and children (aged 0.25-6 yr); and 3) quantify deposition in respiratory tract via multi-path particle dosimetry (MPPD) model. Mass concentrations of indoor air metals increase proportionally with aqueous metal concentrations in fill water, and are inversely related to ventilation. Inhalation-ADDs are 2 magnitudes lower than ingestion-ADDs, using identical water quality for ingestion and fill-water. However, in the 33 m3, low 0.2/h ventilated room, inhalation-HQs are >1 for children and adults, except for Pb. HQ inhalation risks exceed ingestion risks at drinking water regulated levels for As, Cd, Cr, and Mn. MPPD shows greater dose deposits in lungs of children than adults, and 3 times greater deposited doses in a 33 m3 vs 72 m3 room. Rethinking health effects of drinking water and consumer products to broaden consideration of multiple exposure routes is needed.

Positive Airway Pressure Device Care and Cleaning Practices in the Pediatric Home.

BACKGROUND: Regular care and cleaning of positive airway pressure (PAP) devices are important for maintaining equipment in the home. Illness and hospitalization have occurred from inadequate cleaning and use of tap water in the humidifier. In recent years, ozone and ultraviolent-light disinfection devices have been advertised for cleaning home PAP equipment. Our clinic provides instructions; however, cleaning practices performed in the home are unknown. METHODS: A survey of home cleaning practices for PAP equipment was conducted in a pediatric sleep clinic during 2019-2020. Survey domains were method, cleaning and replacement frequency for each component, type of water used, instruction preferences, and demographics. The primary aim was to identify home PAP cleaning practices and compare with provided instructions. The secondary aim was to determine if respiratory-related symptoms (eg, congestion, runny nose, sneezing, coughing) occurred or increased with PAP use or inadequate cleaning. RESULTS: The survey was completed by 96 respondents. Most reported weekly cleaning of mask (36, 38%), tubing (41, 43%), and humidifier (31, 33%) with soap and water as the primary method for each. The majority used distilled water in the humidifier (74, 77%) and reported respiratory symptoms did not occur with PAP use (64, 67%). Very few indicated a device was used to clean equipment. No associations were found between length of time for PAP use and cleaning practices. There was a moderately low correlation between age and cleaning. Increased age was associated with decreased cleaning frequency (r = 0.20, P = .048). CONCLUSIONS: Care and cleaning practices of home PAP equipment varied from instructions provided in clinic. Most reported at least weekly cleaning of items for which daily cleaning is recommended. Few reported using a device for cleaning or having respiratory symptoms from PAP treatment.

Reduced Diffusing Capacity in Humidifier Disinfectant-Associated Asthma Versus Typical Asthma: A Retrospective Case Control Study.

BACKGROUND: Humidifier disinfectant-related lung injury (HDLI) is a severe form of toxic inhalational pulmonary parenchymal damage found in residents of South Korea previously exposed to specific guanidine-based compounds present in humidifier disinfectants (HD). HD-associated asthma (HDA), which is similar to irritant-induced asthma, has been recognized in victims with asthma-like symptoms and is probably caused by airway injury. In this study, diffusing capacity of the lung for carbon monoxide (DLCO) in individuals with HDA was compared to that in individuals with pre-existing asthma without HD exposure. METHODS: We retrospectively compared data, including DLCO values, of 70 patients with HDA with that of 79 patients having pre-existing asthma without any known exposure to HD (controls). Multiple linear regression analysis and logistic regression analysis were performed to confirm the association between HD exposure and DLCO after controlling for confounding factors. The correlation between DLCO and several indicators related to HD exposure was evaluated in patients with HDA. RESULT: The mean DLCO was significantly lower in the HDA group than in the control group (81.9% vs. 88.6%; P = 0.021). The mean DLCO of asthma patients with definite HD exposure was significantly lower than that of asthma patients with lesser exposure (P for trend = 0.002). In multivariable regression models, DLCO in the HDA group decreased by 5.8%, and patients with HDA were 2.1-fold more likely to have a lower DLCO than the controls. Pathway analysis showed that exposure to HD directly affected DLCO values and indirectly affected its measurement through a decrease in the forced vital capacity (FVC). Correlation analysis indicated a significant inverse correlation between DLCO% and cumulative HD exposure time. CONCLUSION: DLCO was lower in patients with HDA than in asthma patients without HD exposure, and decreased FVC partially mediated this effect. Therefore, monitoring the DLCO may be useful for early diagnosis of HDA in patients with asthma symptoms and history of HD exposure.

Exposure at the indoor water-air interface: Fill water constituents and the consequent air emissions from ultrasonic humidifiers: A systematic review.

This systematic review investigates the emissions from ultrasonic humidifiers (e.g., cool mist humidifiers) within indoor air environments, namely soluble and insoluble metals and minerals as well as microorganisms and one organic chemical biocide. Relationships between ultrasonic humidifier fill water quality and the emissions in indoor air are studied, and associated potential adverse health outcomes are discussed. Literature from January 1, 1980, to February 1, 2022, was searched from online databases of PubMed, Web of Science, and Scopus to produce 27 articles. The results revealed clear positive proportional relationships of the concentration of microorganisms and soluble metals/minerals between fill water qualities and emitted airborne particles, for both microbial (n = 9) and inorganic (n = 15) constituents. When evaluating emissions and the consequent health outcomes, ventilation rates of specific exposure scenarios affect the concentrations of emitted particles. Thus, well-ventilated rooms may alleviate inhalation risks when the fill water in ultrasonic humidifiers contains microorganisms and soluble metals/minerals. Case reports (n = 3) possibly due to the inhalation of particles from ultrasonic humidifier include hypersensitivity pneumonitis in adults and a 6-month infant; the young infant exhibited nonreversible mild obstructive ventilator defect. In summary, related literature indicated correlation between fill water quality of ultrasonic humidifier and emitted particles in air quality, and inhalation of the emitted particles may cause undesirable health outcomes of impaired respiratory functions in adults and children.

Characterizing Subjects Exposed to Humidifier Disinfectants Using Computed-Tomography-Based Latent Traits: A Deep Learning Approach.

Around nine million people have been exposed to toxic humidifier disinfectants (HDs) in Korea. HD exposure may lead to HD-associated lung injuries (HDLI). However, many people who have claimed that they experienced HD exposure were not diagnosed with HDLI but still felt discomfort, possibly due to the unknown effects of HD. Therefore, this study examined HD-exposed subjects with normal-appearing lungs, as well as unexposed subjects, in clusters (subgroups) with distinct characteristics, classified by deep-learning-derived computed-tomography (CT)-based tissue pattern latent traits. Among the major clusters, cluster 0 (C0) and cluster 5 (C5) were dominated by HD-exposed and unexposed subjects, respectively. C0 was characterized by features attributable to lung inflammation or fibrosis in contrast with C5. The computational fluid and particle dynamics (CFPD) analysis suggested that the smaller airway sizes observed in the C0 subjects led to greater airway resistance and particle deposition in the airways. Accordingly, women appeared more vulnerable to HD-associated lung abnormalities than men.

Indoor dryness and humidification-induced arsenic inhalation exposure above 4200 m in Ngari, China.

Ngari Prefecture, Tibet, China, features its ultrahigh altitude above 4200 m, very little annual precipitation and extremely low relative humidity. Residents who have migrated to Tibet from the plains use indoor humidification to reduce the respiratory discomfort caused by prolonged exposure to dry indoor air. In this study, field investigations and analysis of residential indoor environments and humidification methods in Ngari Prefecture revealed that ninety-eight percent of humidifier consumers in the prefecture used low-cost ultrasonic humidifiers filled with indoor tap water. The results revealed that the arsenic (As) concentration of the tap water was 41.6 µg/L, over four times China's standards for drinking water quality (10 µg/L). The source As concentration in the air humidified by the tap water-filled ultrasonic humidifier is (619.8 ± 59.1) (ng/m3 ·air), while no As was detected in the air humidified by the evaporative humidifier. For ultrasonic humidifier with tap water-filled, the inhalation dose of a healthy adult was 45.4 ng/d. The minute ventilation volume of migrated residents who had been in Ngari for less than two years (12.5 ± 4.3 L/min) was greater than those of the long-term residents (10.0 ± 4.5 L/min), which may exacerbate the short-term inhalation exposure risk for migrated residents. To reduce the health risks associated with As exposure, evaporative humidifiers are recommended for households using domestic water. If ultrasonic humidifiers are used, the tap water must be purified with terminal filters.