Humidifier Disinfectant Consumption and Humidifier Disinfectant-Associated Lung Injury in South Korea: A Nationwide Population-Based Study

Biocidal products: Opportunities in risk assessment, management, and communication

In the coronavirus disease 2019 era, biocidal products are increasingly used for controlling harmful organisms, including microorganisms. However, assuring safety against adverse health effects is a critical issue from a public health standpoint. This study aimed to provide an overview of key aspects of risk assessment, management, and communication that ensure the safety of biocidal active ingredients and products. The inherent characteristics of biocidal products make them effective against pests and pathogens; however, they also possess potential toxicities. Therefore, public awareness regarding both the beneficial and potential adverse effects of biocidal products needs to be increased. Biocidal active ingredients and products are regulated under specific laws: the Federal Insecticide, Fungicide, and Rodenticide Act for the United States; the European Union (EU) Biocidal Products Regulation for the EU; and the Consumer Chemical Products and Biocide Safety Management Act for the Republic of Korea. Risk management also needs to consider the evidence of enhanced sensitivity to toxicities in individuals with chronic diseases, given the increased prevalence of these conditions in the population. This is particularly important for post-marketing safety assessments of biocidal products. Risk communication conveys information, including potential risks and risk-reduction measures, aimed at managing or controlling health or environmental risks. Taken together, the collaborative effort of stakeholders in risk assessment, management, and communication strategies is critical to ensuring the safety of biocidal products sold in the market as these strategies are constantly evolving.

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.

Dramatic reduction of toxicity of Poly(hexamethylene guanidine) disinfectant by charge neutralization

The current study aimed to investigate the toxicity of positively charged polyhexamethylene guanidine (PHMG) polymer and its complexation with different anionic natural polymers such as k-carrageenan (kCG), chondroitin sulfate (CS), sodium alginate (Alg.Na), polystyrene sulfonate sodium (PSS.Na) and hydrolyzed pectin (HP). The physicochemical properties of the synthesized PHMG and its combination with anionic polyelectrolyte complexes (PECs) namely PHMG:PECs were characterized using zeta potential, XPS, FTIR, and TG analysis. Furthermore, cytotoxic behavior of the PHMG and PHMG:PECs, respectively, were evaluated using human liver cancer cell line (HepG2). The study results revealed that the PHMG alone had slightly higher cytotoxicity to the HepG2 cells than the prepared polyelectrolyte complexes such as PHMG:PECs. The PHMG:PECs showed a significant reduction of cytotoxicity to the HepG2 cells than the pristine PHMG alone. A reduction of PHMG toxicity was observed may be due to the facile formation of complexation between the positively charged PHMG and negatively charged anionic natural polymers such as kCG, CS, Alg. Na, PSS.Na and HP, respectively, via charge balance or neutralization. The experimental results indicate that the suggested method might significantly lower PHMG toxicity while improving biocompatibility.

Effects of Psychotherapy on the Problem Behaviors of Humidifier Disinfectant Survivors: The Role of Individual Characteristics and Adaptive Functioning

This study aimed to examine group differences in the survivors of humidifier damage and the effect of individual psychotherapy on the psychological symptoms of the survivor groups, using the single group pre-post study design. A series of Wilcoxon-Mann-Whitney tests were conducted to investigate the level of psychological problems before and after psychotherapy, as well as the main and interaction effects of demographic characteristics and adaptive functioning on the treatment effects in 69 humidifier disinfectant survivors. The results demonstrated significant differences in problems with socioeconomic status (SES), life functioning, friendships, family relationships, and job adjustment in the survivor groups. Groups with high SES, low life functioning, and poor friend relationships had more problem behaviors than other groups. Problem behaviors related to friendship levels were different before and after psychotherapy. After psychotherapy, individuals with limited social connections exhibited a greater decrease in problem behaviors compared to those with strong friendships. This paper extends the international literature on the long-term consequences of environmental health hazards and the importance of tailored mental health interventions.

Hematotoxic Effect of Respiratory Exposure to PHMG-p and Its Integrated Genetic Analysis

Polyhexamethylene guanidine phosphate (PHMG-p), the main ingredient of humidifier disinfectants, circulates systemically through the lungs; however, its toxicological assessment has been primarily limited to pulmonary disease. Herein, we investigated the possible abnormalities in hematopoietic function 20 weeks after intratracheal instillation of PHMG-p in a rat model. Notable abnormalities were found out in the peripheral blood cell count and bone marrow (BM) biopsy, while RNA sequencing of BM tissue revealed markedly altered gene expression. Furthermore, signaling involved in hematopoietic dysfunction was predicted by analyzing candidate genes through Ingenuity Pathway Analysis (IPA) program. Respiratory PHMG-p exposure significantly decreased monocyte and platelet (PLT) counts and total protein, while significantly increasing hemoglobin and hematocrit levels in peripheral blood. Histopathological analysis of the BM revealed a reduced number of megakaryocytes, with no significant differences in spleen and liver weight to body weight. Moreover, PHMG-p exposure significantly activated estrogen receptor signaling and RHOA signaling, and inhibited RHOGDI signaling. In IPA analysis, candidate genes were found to be strongly related to 'hematological system development and function' and 'hematological disease.' Accordingly, our results suggest that PHMG-p could affect hematopoiesis, which participates in monocyte differentiation and PLT production, and may induce hematologic diseases via the respiratory tract.

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.

Health Effects Associated With Humidifier Disinfectant Use: A Systematic Review for Exploration

BACKGROUND

It has been 10 years since the outbreak of lung disease caused by humidifier disinfectants in Korea, but the health effects have not yet been summarized. Therefore, this study aims to systematically examine the health effects of humidifier disinfectants that have been discovered so far.

METHODS

All literature with humidifier disinfectants and their representative components as the main words were collected based on the web, including PubMed, Research Information Sharing Service, and government publication reports. A total of 902 studies were searched, of which 196 were selected. They were divided into four groups: published human studies (group 1), published animal and cytotoxicology studies (group 2), technical reports (group 3), and gray literature (group 4).

RESULTS

Out of the 196 studies, 97 (49.5%) were published in peer-reviewed journals as original research. Group 1 consisted of 49 articles (50.5%), while group 2 consisted of 48 articles (49.5%). Overall, respiratory diseases such as humidifier disinfectant associated lung injury, interstitial lung disease, and asthma have a clear correlation, but other effects such as liver, heart, thymus, thyroid, fetal growth, metabolic abnormalities, and eyes are observed in toxicological experimental studies, but have not yet been identified in epidemiologic studies.

CONCLUSION

The current level of evidence does not completely rule out the effects of humidifier disinfectants on extrapulmonary disease. Based on the toxicological evidence so far, it is required to monitor the population of humidifier disinfectant exposure continuously to see if similar damage occurs.

Polyhexamethylene guanidine phosphate increases stress granule formation in human 3D lung organoids under respiratory syncytial virus infection

Polyhexamethylene guanidine phosphate (PHMG-p), a humidifier disinfectant, is known to cause lung toxicity, including inflammation and pulmonary fibrosis. In this study, we aimed to investigate the effect of PHMG-p on human lung tissue models (2D epithelial cells and 3D organoids) under conditions of oxidative stress and viral infection. The effect of PHMG-p was studied by evaluating the formation of stress granules (SGs), which play a pivotal role in cellular adaptation to various stress conditions. Under oxidative stress and respiratory syncytial virus (RSV) infection, exposure to PHMG-p remarkably increased eIF2α phosphorylation, which is essential for SG-related signalling, and significantly increased SG formation. Furthermore, PHMG-p induced fibrotic gene expression and caused cell death due to severe DNA damage, which was further increased under oxidative stress and RSV infection, indicating that PHMG-p induces severe lung toxicity under stress conditions. Taken together, toxicity evaluation under various stressful conditions is necessary to accurately predict potential lung toxicity of chemicals affecting the respiratory tract.

Exploring Socio-Demographic Factors Affecting Psychological Symptoms in Humidifier Disinfectant Survivors

This study aimed to compare the psychological symptoms of humidifier disinfectant survivors to the general population and explore socio-demographic factors influencing survivors’ psychological symptoms. A one-way Multivariate Analysis of Covariance (MANCOVA) and a series of two-way MANCOVA were conducted with a sample of 228 humidifier disinfectant survivors and 228 controls. The results demonstrated that the survivor group displayed higher anxious/depressed symptoms, withdrawn symptoms, somatic complaints, thought problems, attention problems, aggressive behavior and rule-breaking behavior than the general group. Moreover, among the socio-demographic factors, the two-way interaction effects of group × family economic status and group × number of friends were found to be statistically significant. The limitations and implications of this study are discussed.