Methylisothiazolinone Research Articles

036 T cells in resolved allergic contact dermatitis drive inflammation and MMP-12–driven tissue modulation

Pathogenic memory T cells are implicated in the local relapse of allergic contact dermatitis (ACD), vitiligo and psoriasis. Here we investigate how resident T cells initiate relapses in response to the allergen Methylisothiazolinone (MI). MI–related ACD was sampled two months and two years after resolution of disease. T cells were activated in skin explants with MI or the pan T-cell agonist OKT-3. Epidermis was analysed by RNAseq, Nanostring and multiplex methods. Metalloproteinase 12 (MMP-12)–induction by ACD–related cytokines was assessed in primary keratinocytes and fibroblasts and a humanized xenograft mouse model was used.

Biodistribution and respiratory toxicity of chloromethylisothiazolinone/methylisothiazolinone following intranasal and intratracheal administration

A variety of isothiazolinone-containing small molecules have been registered and used as chemical additives in many household products. However, their biodistribution and potential harmful effects on human health, especially respiratory effects, were not yet identified in sufficient detail. The purpose of this study was to investigate whether a biocide comprising a mixture of chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT) could reach the lungs and induce lung injury when exposure occurs by two administration routes involving the respiratory tract: intratracheal and intranasal instillation. To investigate the biodistribution of CMIT/MIT, we quantified the uptake of 14C-labeled CMIT/MIT in experimental animals for up to seven days after intratracheal and intranasal instillation. In the toxicity study, lung injury was assessed in mice using total inflammatory cell count in bronchoalveolar lavage fluid (BALF) and lung histopathology. The results of the biodistribution study indicated that CMIT/MIT were rapidly distributed throughout the respiratory tract. Using quantitative whole-body autoradiogram analysis, we confirmed that following intranasal exposure, CMIT/MIT reached the lungs via the respiratory tract (nose–trachea–lung). After 5 min post intratracheal and intranasal instillation, the amount of radiotracer ([14C]CMIT/MIT) in the lungs was 2720 ng g−1 and 752 ng g−1 tissue, respectively, and lung damage was observed. A higher amount of the radiotracer resulted in higher toxicity. Both intratracheal and intranasal instillation of CMIT/MIT increased inflammatory cell counts in the BALF and induced injuries in the alveoli. The frequency and the severity scores of injuries caused by intratracheal instillation were approximately-four to five times higher than those induced by intranasal instillation. Therefore, we concluded that CMIT/MIT could reach the lungs following nasal and intratracheal exposure and cause lung injuries, and the extent of injury was dependent on the exposure dose.

Photocatalytic degradation of methylisothiazolinone in water by TiO2 and TiO2/persulfate systems with simulated solar radiation

The photocatalytic decomposition of methylisothiazolinone (MIT) in water was successfully attained with TiO2 and TiO2/persulfate systems under simulated solar irradiation. The TiO2 catalysts were synthesized by sol-gel process, controlling the hydrolysis rate of titanium n-butoxide by two procedures: external addition of water and in situ production of water via esterification between ethanol and a carboxylic acid. Crystalline structure, morphology and textural properties of materials were characterized by XRD, SEM and N2 adsorption-desorption isotherms. The photocatalytic activity of the obtained catalysts for MIT degradation was proved to be significantly dependent on both the procedure of water provision for the alkoxide hydrolysis and the calcination temperature. Adding persulfate (PS) to the system resulted in a great enhancement of the MIT degradation rate, which was kept in different water matrices due to a synergistic effect between the titania catalysts and PS activation. MIT transformation products (TPs) were identified by HPLC-HRMS and a mechanism for MIT degradation was proposed. Total Organic Carbon and toxicity measurements established the complete MIT mineralization and non-toxicity of the water solution after the photocatalytic treatment.

Mild Fenton Processes for the Removal of Preservatives: Interfering Effect of Methylisothiazolinone (MIT) on Paraben Degradation

The degradation of various preservatives used in the cosmetics industry, including five parabens and their most employed substitute, methylisothiazolinone (MIT), was investigated. A mild photo-Fenton process was applied using low iron concentrations (5 mg/L) at a pH of five, instead of the traditional acidic value of three. At these conditions, the paraben degradation was very low after one hour of reaction and it was necessary to present humic-like substances (HLS) acting as iron chelators to improve the process. Values obtained when MIT was treated were very low, also in the presence of HLS, indicating that their complexing effect was not acting properly. When MIT was added to the mixture of parabens an inhibitory effect was found in the presence of HLS. A possible complex between iron and MIT was suggested and the studies of hydrogen peroxide consumption and Job’s plot technique confirmed this hypothesis. Evidence of the formation of this inactive complex, so far never reported, will be essential in future work when dealing with this compound using Fenton processes. Furthermore, this fact points out the importance of using mixtures of model contaminants instead of a single one or a group of the same family, since their ability to form active or inactive complexes with iron can strongly change the behavior of the whole system.

In vitro study of the ecotoxicological risk of methylisothiazolinone and chloroxylenol towards soil bacteria

Methylisothiazolinone (MIT) and chloroxylenol (PCMX) are popular disinfectants often used in personal care products (PCPs). The unregulated discharge of these micropollutants into the environment, as well as the use of sewage sludge as fertilizer and reclaimed water in agriculture, poses a serious threat to ecosystems. However, research into their ecotoxicity towards nontarget organisms is very limited. In the present study, for the first time, the ecotoxicity of biocides to Pseudomonas putida, Pseudomonas moorei, Sphingomonas mali, and Bacillus subtilis was examined. The toxicity of MIT and PCMX was evaluated using the microdilution method, and their influence on the viability of bacterial cells was investigated by the AlamarBlue® test. The ability of the tested bacteria to form biofilms was examined by a microtiter plate assay. Intracellular reactive oxygen species (ROS) production was measured with CM-H2DCFDA. The effect of MIT and PCMX on phytohormone indole-3-acetic acid (IAA) production was determined by spectrophotometry and LC‒MS/MS techniques. The permeability of bacterial cell membranes was studied using the SYTOX Green assay. Changes in the phospholipid profile were analysed using LC‒MS/MS. The minimal inhibitory concentrations (MICs) values ranged from 3.907 to 15.625 mg L−1 for MIT and 62.5 to 250 mg L−1 for PCMX, indicating that MIT was more toxic. With increasing concentrations of MIT and PCMX, the cell viability, biofilm formation ability and phytohormone synthesis were maximally inhibited. Moreover, the growth of bacterial cell membrane permeability and a significantly increased content of ROS were observed, indicating that the exposure caused serious oxidative stress and homeostasis disorders. Additionally, modifications in the phospholipid profile were observed in response to the presence of sublethal concentrations of the chemicals. These results prove that the environmental threat posed by MIT and PCMX must be carefully monitored, especially as their use in PCPs is still growing.

Ultrafast self-assembly Fe2O3 nanoparticles confined in carbon layers toward robust heterogeneous electro-Fenton reaction

Heterogeneous electro-Fenton (EF) is a promising advanced oxidation process for refractory wastewater treatment. However, typical calcination or hydrothermal method for heterogeneous EF cathode fabrication is time-consuming, energy-consuming, or harmful to the environment. High-temperature shock (HTS) technique is a novel and rapid material synthesis method with the advantages of low-cost, eco-friendly. In this study, the electrodes named Fe2O3@C/carbon cloth (Fe2O3@C/CC), were synthesized by HTS for the first time within an extremely short time (∼5 s). The Fe2O3 nanoparticles with an average diameter of 61.90 ± 15.09 nm are uniformly dispersed on carbon cloth (CC) with the confinement and protection of the carbon layers. The as-prepared Fe2O3@C/CC cathode exhibited excellent electrocatalytic properties in the EF system. The removal efficiency of methylisothiazolinone (MIT) could reach 90.60 ± 1.70% in 40 min at a low current density of 1.11 mA cm−2 under the oxidation of the hydroxyl radical. In addition, the degradation pathways of MIT were further studied. According to the results of theoretical calculation, the –S–N– bond is the primary active site attacked during MIT degradation process. Therefore, heterocyclic loop opening is the main pathway of MIT degradation. HTS is an ultrafast and convenient potential technique compared with other cathode synthesis methods.

Alkil glükozid szenzibilizáció – a környezetbarát termékek veszélyei Ajánlás a magyar környezeti standard sorba történő beemelésre

Alkyl glucosides are compounds with cleaning, foaming, and emulsifying properties. They have become increasingly popular in recent years due to their environmentally- friendly features. They are mainly used in products for environmentally conscious consumers. Alkyl glucosides are present in 10% of products according to the Contact Allergen Management Program (CAMP) database. They are present in shower gels, soaps, shampoos, sunscreens, detergents, hair dyes, perfumes, and deodorants. They are also found in wipes for newborns and infants, so there is a risk of early sensitization. Their presence has also been described in foam wound dressings and antimicrobial foam dressings. Their importance is highlighted by the fact that in 2017, the American Contact Dermatitis Society (ACDS) named alkyl glucosides as „allergens of the year”. The present article describes the frequency and characteristics of decyl glucoside and lauryl glucoside sensitization in patients patch tested between 2018 and 2021 at the Department of Dermatology, Venereology, and Dermatooncology of the Semmelweis University. From January 2018 to December 2021, a total of 1160 patients were patch tested and 30 patients (2,59%) had a positive reaction to at least one of the alkyl glucosides. 7 patients were sensitized only to decyl glucoside, 10 patients only to a lauryl glucoside, and 13 patients to both alkyl glucosides. 56.67% of the alkyl glucoside sensitized patients were female, and 26.67 - 26.67% were in the age group 20- 29 years and 60-69 years. Patients sensitized with alkyl glucoside most commonly had allergic contact dermatitis symptoms all over the body, on the face, and hands. The positive patch test reactions occurred mainly in the 72. hour. The most common co-sensitizations were methylisothiazolinone (MI) and nickel (II) sulfate. 30% of the alkyl glucoside sensitized patients had a history of atopic dermatitis. According to our results, we recommend the inclusion of decyl glucoside and lauryl glucoside in the Hungarian standard patch test series.

Chlorination of isothiazolinone biocides: kinetics, reactive species, pathway, and toxicity evolution

Due to the Covid-19 pandemic, the worldwide biocides application has been increased, which will eventually result in enhanced residuals in treated wastewater. At the same time, chlorine disinfection of secondary effluents and hospital wastewaters has been intensified. With respect to predicted elevated exposure in wastewater, the chlorination kinetics, transformation pathways and toxicity evolution were investigated in this study for two typical isothiazolinone biocides, methyl-isothiazolinone (MIT) and chloro-methyl-isothiazolinone (CMIT). Second-order rate constants of 0.13 M−1·s−1, 1.95 × 105 M−1·s−1 and 5.14 × 105 M−1·s−1 were determined for the reaction of MIT with HOCl, Cl2O and Cl2, respectively, while reactivity of CMIT was around 1-2 orders of magnitude lower. While chlorination of isothiazolinone biocides at pH 7.1 was dominated by Cl2O-oxidation, acidic pH and elevated Cl− concentration favored free active chlorine (FAC) speciation into Cl2 and increased overall isothiazolinone removal. Regardless of the dominant FAC species, the elimination of MIT and CMIT resulted in an immediate loss of acute toxicity under all experimental conditions, which was attributed to a preferential attack at the S-atom resulting in subsequent formation of sulfoxides and sulfones and eventually an S-elimination. However, chlorination of isothiazolinone biocides in secondary effluent only achieved <10% elimination at typical disinfection chlorine exposure 200 mg·L−1·min, but was predicted to be remarkably increased by acidizing solution to pH 5.5. Alternative measures might be needed to minimize the discharge of these toxic chemicals into the aquatic environment.

HPLC method with electrochemical detection on gold electrode for simultaneous determination of different antimicrobial agents in cosmetics

Antimicrobial agents are added to a wide variety of products such as cosmetics to reduce the risk of microbial contamination and ensure the suitability and safety of the product. However, recent studies have shown that these compounds can have negative effects on human health and the environment. Therefore, it is crucial to develop analytical methods to control the amount of these compounds in personal care products to guarantee human health and product quality. This paper presents an HPLC method with electrochemical detection using a gold electrode for the determination of the most used antimicrobial agents in cosmetic products: methylparaben (MP), 4-hydroxybenzoic acid (4-HBA), phenoxyethanol (PE) and methylisothiazolinone (MIT). For this purpose, the electrochemical response of these compounds was evaluated on the gold electrode. The optimal electrochemical detection of MP, 4-HBA; PE and MIT was performed at pH 2 and + 1.50 V (vs Ag/AgCl). Under the optimal separation and detection conditions, limits of detection (LODs) between 10 and 110 μg L−1 were obtained. These LODs are lower than those previously reported for other HPLC methods with mass spectrometry and diode-array detectors. Cosmetic products with different compositions were successfully analysed with the proposed HPLC method obtaining recoveries between 76 % and 119 %.

Mn doping improves in-situ H2O2 generation and activation in electro-Fenton process by Fe/Mn@CC cathode using high-temperature shock technique

Fe/Mn@carbon cloth (CC) was successfully fabricated through high-temperature shock (HTS) technique and used as cathode modification in heterogeneous electro-Fenton (hetero-EF) process for methylisothiazolinone (MIT) degradation. The nanocrystalline on Fe/Mn@CC electrode is doped with Fe and Mn oxides and coated with carbon layer, which could markedly enhance the electrocatalysis with high electro-chemical active area and low resistance. Fe/Mn@CC modified cathode can efficiently in-situ produce and activate H2O2, showing high electrocatalytic activity to MIT degradation. The 95.2% MIT degradation with in 100 min were achieved under the condition of 30 mA current, 0.75 L min−1 aeration intensity and initial pH = 3. Based on the CV curves and stability test, the high degradation activity revealed the kinetically beneficial regeneration of FeII/MnII in Fe/Mn@CC and activation of H2O2. The electron transfer between FeII/III and MnII/III, together with the direct FeII/MnII regeneration on the cathode, could markedly promote the H2O2 utilization, and eventually lead to MIT degradation.

Contact Allergy in the Elderly: A Study of 600 Patients.

The proportion of elderly in the general population is increasing. Ageing of the skin and immune system can modify the features of contact hypersensitivity (CH). The number of epidemiological studies according to the age-related features of CH is very limited. We aimed to analyse the clinical characteristics of CH in an elderly patient population. A total of 600 patients (patient age > 60 years old) were patch tested with the European Environmental Baseline Series (EEBS) and 440 of them with the Complementary Fragrance Series (CFS) at the same time according to the actual international methodological standards in the Allergy Outpatient Unit of Department of Dermatology, Venereology and Dermato-Oncology of Semmelweis University between 2015–2019. Out of 600 tested patients, 54.8% had at least one allergen positivity. Female predominance was observed (78.7%). The most common diagnosis was contact dermatitis (63.7%), followed by psoriasis (6.2%). Most of the cases (58.0%) were found in the age group of 60–69. The five most common contact allergens were benzoic acid, methylisothiazolinone (MI), wood tar, nickel, and balsam of Peru. Allergic skin symptoms are present in all ages and also in the elderly. According to our data, the most common contact allergens are preservatives, followed by balsam of Peru among men and nickel among women. In case of contact dermatitis, stasis dermatitis, rosacea, and atopic dermatitis are worth patch testing to verify CH even in those above 60 years old.

Preservative Contact Hypersensitivity among Adult Atopic Dermatitis Patients.

Atopic dermatitis (AD) is a chronic inflammatory disease characterised by an impaired skin barrier. The prolonged use of topical preparations containing medications, emollients, fragrances and preservatives may increase the risk of contact hypersensitivity (CHS). In the Allergy Outpatient Unit of the Department of Dermatology, Venereology and Dermatooncology of Semmelweis University, 5790 adult patients were patch tested between 2007–2021 with the European Environmental Baseline Series according to international standards. Among all the tested adult patients, 723 had preservative CHS (PCHS) and 639 had AD. Among the 723 PCHS patients, 68 (9.4%) had AD; the female to male ratio was 3:1 in this group. Out of 639 AD patients, 68 had PCHS (10.6%). In the AD-PCHS group, 83.8% had CHS to methylisothiazolinone (MI) (tested from 2014), 36.8% to Kathon CG®, 16.2% to methyldibromo-glutaronitrile, 11.8% to paraben, 7.4% to formaldehyde, 4.4% to para-tert-butylphenol-formaldehyde resin and 1.5% to Quaternium-15. The most common concomitant PCHS combination was Kathon CG® + MI. Most patients (32.4%) belonged to the age group of 21–30, and skin symptoms affected mostly the limbs and face. The most common other concomitant allergens were nickel, lanolin alcohol and balsam of Peru. Preservatives (especially MI and Kathon CG®) are important contact allergens in adult AD, mostly among young women. The rate of AD in the PCHS group and the rate of PCHS in the AD group is remarkable; thus, the role of PCHS should be highlighted in the topical therapy and in the prevention of possible AD exacerbations.

Removal of methylisothiazolinone biocide from wastewater by VUV/UV advanced oxidation process: Kinetics, mechanisms and toxicity

Methylisothiazolinone (MIT) is frequently used as antimicrobial in household and industrial products, and poses ecological and health risks to aquatic organisms and humans. In this study, vacuum ultraviolet (VUV)/ultraviolet (UV) irradiation was found highly efficient for removal of MIT. The rate constant of MIT degradation (kobs) under VUV/UV irradiation was 3.75 μEinstein−1 cm2, which was around 12.5 times higher than that under UV irradiation. The •OH concentration during the VUV/UV process was 1.0 × 10−12 M. The contributions of UV photolysis and •OH oxidation to MIT degradation under VUV/UV irradiation were 7.3% and 92.7%, respectively. The optimum solution pH (6.0–7.1) gave kobs 33%–39% higher than those at pH 3.9 and 9.3. CO32−/HCO3− inhibited MIT degradation and the kobs decreased by 74% when the concentration of CO32−/HCO3− was increased to 1 mM. The order of MIT removal efficiency under VUV/UV irradiation was ultrapure water > secondary effluent > reverse osmosis (RO) concentrate, because of the light screening and •OH quenching effect of actual wastewater. In RO concentrate, the rate constant of MIT degradation under VUV/UV irradiation was 22% higher than that obtained under UV irradiation. The reduction of TOC, UV254, and total fluorescence regional integration of the RO concentrate during VUV/UV process were 7.2%, 34.9%, and 52.3%, respectively. Twelve main transformation products of MIT were identified after VUV/UV degradation. The main degradation mechanisms of MIT were sulfur atom oxidation and hydroxyl addition. Quantitative structure–activity relationship analysis showed that VUV/UV degradation was an efficient method to remove the toxicity of MIT.

Cosmetic preservative labeling in Philippine products in accordance with Philippine regulations.

Preservatives are usually added to a wide array of consumer products to prevent growth of microbes and to prevent product destabilization and degradation. However, many of these preservatives are common skin sensitizers and may cause allergic contact dermatitis. The amount of preservatives may vary per country or region according to their respective legislation and may be reported in differences in prevalence rates of contact dermatitis. To examine and identify preservatives in consumer products in accordance with Philippine legislation. To verify the accuracy of the list of ingredients of Philippine cosmetic products as legislated by the Philippine Bureau of Food and Drug Administration. A total of 65 commonly used Philippine consumer products ranging from liquid facial and body washes, bar soaps, laundry detergents, feminine hygiene washes and wipes, shampoos and conditioners, sunblock, and moisturizers were selected. Ingredients noted on labels were documented. Products were subsequently investigated chemically for the presence of methylchloroisothiazolinone, methylisothiazolinone, or formaldehyde. The preservatives most commonly used in cosmetic products in the Philippine market are methylchloroisothiazolinone (MCI), methylisothiazolinone (MI), and/or formaldehyde. In accordance with Philippine legislation, almost all products provided a detailed ingredient list as printed on the packaging. Measurements of MCI/MI ranged from less than 1ppm to 16 ppm, and MI ranged from only less than 1 ppm to 66 ppm, whereas formaldehyde was noted to range from less than 2.5ppm to greater than 40 ppm in the products tested. Most products are manufactured by international brands, with a few products being manufactured locally. The preservatives found in cosmetic products were MCI, MI, and formaldehyde. Discrepancies were found in the preservatives and labeling of these products, with a majority of investigated Philippine products labeled inaccurately with varying concentrations of preservatives.

Review of Inhalation Health Risks Involving Chloromethylisothiazolinone (CMIT) and Methylisothiazolinone (MIT) Used as Disinfectants in Household Humidifiers.

The association between lung injury and exposure to humidifier disinfectant (HD) containing a mixture of chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT) has been controversial in South Korea. This study conducts a literature review in order to evaluate the likelihood of CMIT/MIT reaching the lower part of the respiratory tract and causing lung injury. A literature review focused on the inhalation risk of HD containing a mixture of CMIT and MIT. The major contents included the physicochemical properties of CMIT and MIT contained in HDs and methodological reviews on substance analysis, toxicity tests and clinical cases. HD products marketed in South Korea have been reported to contain approximately 1–2% CMIT and 0.2–0.6% MIT along with magnesium nitrate (20–25%), magnesium chloride (0.2–1.0%), and water (70–75%). The types of CMIT and MIT dispersed into the air and deposited in the respiratory tract are assumed to be either gaseous substances or nanoparticles mixed with magnesium salts. The result of the literature review including clinical cases of lung injury among CMIT/MIT HD product users, demonstrated that these chemicals likely reach the lower respiratory tract and accordingly cause lung injury. A number of humidifier disinfectant-associated lung injury cases with clinical evidence should be prioritized in risk assessment of HD containing CMIT and MIT, even though there might be insufficient evidence in all related areas, including inhalation exposure assessment studies, animal testing, and epidemiological studies.

Chronic hand eczema: clinical characterization, aetiology, concomitant foot eczema and polysensitization.

Chronic hand eczema (CHE) is a disabling dermatosis that presents with concomitant conditions, such as foot eczema and contact sensitization To identify the characteristics of the CHE population, with particular emphasis on occupational relevance and evaluation of concomitant foot eczema and polysensitization A total of 2,926 patch-tested patients, presenting with CHE from different specialized dermatological units from 2004 to 2014, were evaluated. A global descriptive characterization was performed including hand subtype analysis, as well as accurate evaluation of polysensitization The most frequent global CHE diagnostic was irritant contact dermatitis (42%) and, for patients with foot and chronic hand eczema (FCHE), allergic contact dermatitis (28%). Of CHE cases, 39% showed occupational relevance. Positivity to at least one allergen was found in 55% of patients, with nickel and methylisothiazolinone (MI) being the most prevalent. Methylchloroisothiazolinone/MI, nickel and potassium dichromate showed the highest occupational relevance. Patients with concomitant FCHE (8%) showed greater sensitization for potassium dichromate and cobalt chloride. Twelve percent were polysensitized, with MI being the most frequently involved contact allergen Patch testing for FCHE and CHE revealed a specific contact allergen and occupational profile. MI was the most frequently reported allergen related to polysensitization in CHE.

Effects of methylisothiazolinone and octylisothiazolinone on development and thyroid endocrine system in zebrafish larvae

Methylisothiazolinone (MIT) and octylisothiazolinone (OIT) are used as preservatives and biocides to prevent product decay or deterioration. In the present study, developmental toxicity and the effect on the thyroid endocrine system were investigated in zebrafish embryos exposed to MIT and OIT for 96 h. Coagulation was significantly increased when zebrafish embryos were exposed to a concentration of 300 μg/L MIT and ≥ 0.3 μg/L OIT, resulting in a significant decrease in hatchability and larvae survival. The body length in zebrafish larvae exposed to 30 μg/L OIT was significantly shorter than that of the control group. The whole-body levels of triiodothyronine and thyroxine were significantly decreased in larvae exposed to MIT and OIT. Significant upregulation of crh, trh, tshβ, and tshr genes and downregulation of trαa, tg, ttr, and deio2 genes were observed in fish exposed to two isothiazolinones. The expression of dre-miR-193b and dre-miR-499 was significantly increased in zebrafish larvae exposed to MIT and OIT, indicating that epigenetic deregulation of miRNAs modulated genes involved in thyroid hormone regulation. OIT has a higher magnitude of toxicity than MIT, corresponding to the observed changes in thyroid hormones and developmental toxicity.

Synergistic effects of ozone/peroxymonosulfate for isothiazolinone biocides degradation: Kinetics, synergistic performance and influencing factors

Synergistic effects of ozone (O3) and peroxymonosulfate (PMS, HSO5−) for isothiazolinone biocides degradation was studied. The synergistic ozonation process (O3/PMS) increased the efficiency of methyl-isothiazolinone (MIT) and chloro-methyl-isothiazolinone (CMIT) degradation to 91.0% and 81.8%, respectively, within 90 s at pH 7.0. This is 30.6% and 62.5% higher than the corresponding ozonation efficiency, respectively. Total radical formation value (Rct,R) for the O3/PMS process was 24.6 times that of ozonation alone. Calculated second-order rate constants for the reactions between isothiazolinone biocides and ▪ (kSO4-,MIT and kSO4-,CMIT) were 8.15 × 109 and 4.49 × 109 M−1 s−1, respectively. Relative contributions of O3, hydroxyl radical (OH) and ▪ oxidation to MIT and CMIT removal were estimated, which were 15%, 45%, and 40% for O3, OH and ▪ oxidation to MIT, and 1%, 67%, and 32% for O3, OH and ▪ oxidation to CMIT at pH 7.0, respectively. Factors influencing the O3/PMS process, namely the solution pH, chloride ions (Cl−), and bicarbonate (HCO3−), were evaluated. Increasing the solution pH markedly accelerated O3 decay and OH and ▪ formation, thus weakening the relative contribution of O3 oxidation while enhancing that of OH and ▪. Cl− had a negligible effect on MIT and CMIT degradation. Under the dual effect of bicarbonate (HCO3−) as inhibitor and promoter, low concentrations (1–2 mM) of bicarbonate weakly promoted MIT and CMIT degradation, while high concentrations (10–20 mM) induced strong inhibition. Lastly, oxidation performance of O3 and O3/PMS processes for MIT and CMIT degradation in different water matrices was compared.

Assessment of agonistic and antagonistic properties of humidifier disinfectants to the estrogenic and androgenic receptors by transactivation assay.

Before being recalled and banned from the Korean market, humidifier disinfectants (HDs) were added to the humidifier water tank to prevent microbial growth. The known HDs active ingredients included the are oligo(2-(2-ethoxy)ethoxyethyl guanidine (PGH), polyhexamethylene guanidine (PHMG), a mixture of methylisothiazolinone (MIT) and chloromethylisothiazolinone (CMIT), didecyldimethyl ammonium chloride (DDAC), Sodium dichloroisocyanurate (NaDCC), and alkyldimethylbenzyl ammonium chloride (BAC). Previous epidemiological studies have suggested that PHMG induces fatal lung disease in pregnant, post-partum women, and young children. In an animal study, a mixture of DDAC and BAC exhibited decreased fertility and fecundity; increased time to first litter, longer pregnancy intervals, fewer pups per litter, and fewer pregnancies. In this study, endocrine-disrupting effects of HDs were investigated using estrogen receptor (ER) and androgen receptor (AR) transactivation assay based on OECD Test guidelines. Unexpectedly, unlike the previously reported reproductive toxicity data, in the present study, HDs did not show ER and AR transcriptional activation agonist and/or antagonist effects. However, it is difficult to conclude that HDs has no endocrine disruption effects, and further research on the effects of HDs mixtures, and in vivo tests including Uterotrophic bioassay and Hershberger bioassay would be necessary.

A Study on the Behavior Patterns of Liquid Aerosols Using Disinfectant Chloromethylisothiazolinone/Methylisothiazolinone Solution.

This study evaluates the behavioral characteristics of components (methylisothiazolinone (MIT) and chloromethylisothiazolinone (CMIT)) contained in disinfectant solutions when they convert to liquid aerosols. The analytical method for MIT and CMIT quantitation was established and optimized using sorbent tube/thermal desorber-gas chromatography-mass spectrometry system; their behavioral characteristics are discussed using the quantitative results of these aerosols under different liquid aerosol generation conditions. MIT and CMIT showed different behavioral characteristics depending on the aerosol mass concentration and sampling time (sampling volume). When the disinfectant solution was initially aerosolized, MIT and CMIT were primarily collected on glass filter (MIT = 91.8 ± 10.6% and CMIT = 90.6 ± 5.18%), although when the generation and filter sampling volumes of the aerosols increased to 30 L, the relative proportions collected on the filter decreased (MIT = 79.0 ± 12.0% and CMIT = 39.7 ± 8.35%). Although MIT and CMIT had relatively high vapor pressure, in liquid aerosolized state, they primarily accumulated on the filter and exhibited particulate behavior. Their relative proportions in the aerosol were different from those in disinfectant solution. In the aerosol with mass concentration of ≤5 mg m−3, the relative proportion deviations of MIT and CMIT were large; when the mass concentration of the aerosol increased, their relative proportions constantly converged at a lower level than those in the disinfectant solution. Hence, it can be concluded that the behavioral characteristics and relative proportions need to be considered to perform the quantitative analysis of the liquid aerosols and evaluate various toxic effects using the quantitative data.