Skin irritation and inhalation toxicity of biocides evaluated with reconstructed human epidermis and airway models

Target and Suspect Screening for Organic Additives in Six Classifications of Personal Care Products Using Liquid Chromatography-High-Resolution Mass Spectrometry

Personal care products (PCPs) are integral components of daily human existence, including a large number of chemicals intentionally added for functional attributes (e.g., preservatives and fragrances) or unintentionally present, such as plasticizers. This investigation aimed to optimize the methodology for target and suspect screening via liquid chromatography-high-resolution mass spectrometry, focusing on nine prevalent organic additives (comprising bisphenols A, F, and S, methyl, ethyl, propyl, and butylparaben, 5-chloro-2-methyl-4-isothiazolin-3-one, and 4-hydroxybenzoic acid). A total of 50 high-selling PCPs were purchased from the local online market as samples. In detail, PCP samples were classified into body washes, shampoos, hair conditioners, facial cleansers, body lotions, and moisture creams. For calibration, the quality assurance and quality control results demonstrated a coefficient of determination (R2) surpassing 0.999, with detection and quantification limits ranging from 2.5 to 100.0 ng/g. For recovery experiments, replicate recoveries (n = 5) ranged from 61 to 134%. In purchased PCP samples, five of the nine target compounds were detected via a target screening. Methylparaben exhibited the highest concentration (7860 mg/kg) in a facial cleanser, which is known as an endocrine-disrupting chemical. A total of 248 suspects of organic additives were screened in PCPs, leading to a tentative identification of 9. Confirmation (confidence level 1) via reference standards was achieved for three suspects, while six were tentatively identified with a confidence level of 2. This two-step extraction methodology utilizing methyl tert-butyl ether and isopropyl alcohol enabled simultaneous analysis of diverse chemical groups with distinct properties.

In Vivo Toxicity of Industrial Biocide Containing 2,2-Dibromo-3-nitrilopropionamide in Adult and Zebrafish Larvae

2,2-Dibromo-3-nitrilopropionamide (DBNPA) is a widely used biocide with potential environmental implications due to its toxicity. This study aimed to investigate the in vivo toxicity of DBNPA in zebrafish (Danio rerio), a model organism in environmental toxicology. Both adult and larval zebrafish were exposed to varying concentrations of DBNPA, and significant morphological changes and mortality rates were observed. The study found that even relatively low concentrations of DBNPA can have detrimental effects on zebrafish embryonic development, and high concentrations resulted in rapid mortality in adult zebrafish and larvae. The LC50 values calculated from this study were 9.3 ppm for adults and 9.1 ppm for larvae, indicating the high toxicity of DBNPA to these organisms. These findings underscore the potential environmental impact of DBNPA and highlight the need for further research into its effects on aquatic ecosystems.

1,2,4-trihydroxybenzene induces stress granule formation and causes DNA damage in human keratinocytes

Household chemical products are typically evaluated for toxicity through ingestion and inhalation, with limited information on skin absorption. Furthermore, current research focuses on the long-term toxic effects of harmful substances contained in these household chemical products, however not much is known about their acute toxic effects. In this study, the effects of 1,2,4-trihydroxybenzene (THB) in human keratinocytes by examining its effects on stress granule (SG) formation, a marker of acute stress response, and DNA double strand breaks caused by repeated exposure. THB effectively induced SG formation via endoplasmic reticulum stress-mediated eIF2α phosphorylation in keratinocytes. Furthermore, repeated exposure to THB causes apoptotic cell death due to DNA double strand breaks. Collectively, THB exposure leads to skin toxicity, suggesting precautions for the use of THB-containing household chemical products.

Chloromethylisothiazolinone induces ER stress-induced stress granule formation in human keratinocytes

Chloromethylisothiazolinone (CMIT), a humidifier disinfectant, is known to be toxic to the respiratory system. While the toxic effect of CMIT on the lungs has been widely investigated, its effect on the skin is well unknown. In this study, we examined stress granule (SG) formation to investigate the cytotoxic effects of CMIT on human keratinocytes. We assessed the viability of the cells following CMIT exposure and performed immunofluorescence microscopy and immunoblot analyses to determine SG formation and downstream pathways. The IC50 values in human keratinocyte HaCaT cells after CMIT exposure for 1 and 24 h were 11 and 8 μg/mL, respectively, showing no significant difference. As determined using immunofluorescence microscopy, SG formation was effectively induced after CMIT exposure. Moreover, the phosphorylation of eukaryotic initiation factor-2α (eIF2α), a translation initiation factor, and protein kinase R-like endoplasmic reticulum (ER) kinase, which plays a role in the ER stress-mediated eIF2α phosphorylation, was confirmed by CMIT exposure. These results suggest that exposure to CMIT can have detrimental effects on the skin, even briefly, by inducing SG formation through ER stress in keratinocytes.

Risk assessment of the asthma-induction potential of substances in spray products for car cabin detailing - based on EU's Chemical Agents Directive, using harmonised classifications and quantitative structure-activity relationship (QSAR)

Exposure to spray-formulated products for car cabin detailing is a potential risk for asthma induction. With a focus on the asthma-related endpoints sensitisation and irritation of the lungs, we performed an occupational risk assessment based on requirements in the EU Chemical Agents Directive. We identified 71 such spray products available in Denmark. We identified ingredient substances in safety data sheets and screened for harmonised classifications of respiratory sensitisation and airway irritation. For respiratory sensitisation, we also applied quantitative structure-activity relationship (QSAR). We modelled the exposure during 15 min of work inside a car cabin, and determined the risk ratio of the products by further applying occupational exposure limits - mainly derived no-effect levels (DNELs) from the European Chemicals Agency (ECHA) set on respiratory irritation. Four substances had a harmonised classification for respiratory irritation (bronopol, 2-phenoxyethanol, 2-methoxypropanol, and butan-1-ol). Seven substances were positive in the QSAR model for respiratory sensitisation (monoethanolamine, bronopol, glycerol, methyl salicylate, benzoic acid, ammonium benzoate, and sodium benzoate). Two vinyl treatment products had a risk ratio > 1 based on the level of sodium benzoate and its DNEL set on respiratory irritation. Two products had risk ratios of 0.69 and 0.73, respectively, based on 2-methyl-2 H-isothiazol-3-one and its acute DNEL set on respiratory irritation. In conclusion, 10 substances that may pose a risk for asthma induction were identified in the products. Two of the 71 products had a risk ratio > 1, meaning they may pose an asthma-induction risk in the modelled exposure scenario and using respiratory irritation DNELs from ECHA.

Evaluation of Skin Irritation of Acids Commonly Used in Cleaners in 3D-Reconstructed Human Epidermis Model, KeraSkinTM

Cleaners such as dishwashing liquids contain various chemicals that cause skin damage. Alkaline agents used in cleaners alter the lipid composition of the skin and damage the skin barrier. However, little is known about the effects of acids used in cleaners on the skin. Here, we investigated the effects of acidic pH on the skin and evaluated the skin irritation of acids commonly used in cleaners with a 3D-reconstructed human epidermis model, KeraSkin^TM, according to OECD TG439. First, to examine the effects of acidic pH, we evaluated the skin irritation of citrate buffers (0.1 M, McIlvaine buffer) prepared in a wide pH range (pH 1.5-6.0). Surprisingly, cell viability was not significantly affected even at pH 1.5, reflecting that the acidity alone may not be sufficient to induce skin irritation. Even after longer exposure (180 min), the cell viability was not reduced below 50%, a cutoff to determine an irritant. To examine the effect of the anionic part, several organic acids used in cleaners (citric acid, glycolic acid, lactic acid, malic acid, and succinic acid) were examined. These organic acids also failed to reduce viability at 0.1 M. However, at 1 M, most of the acids tested, except lactic acid, were determined to be skin irritants. Histology further supported the skin irritancy of acids at 1 M. Similarly, inorganic acids (hydrogen bromide, hydrogen chloride, nitric acid, and sulfuric acid) were determined to be irritants only at 1 M. In the case of alkaline agents, pH and concentrations were also important factors to determine the skin irritancy, although the epidermal structure and lipids were more damaged than acids. Collectively, we demonstrated that both the pH and concentration are important factors for the skin irritancy of acids, shedding an important insight into the mechanism of skin irritation.

Effect of Cosmetics Use on the In Vitro Skin Absorption of a Biocide, 1,2-Benzisothiazolin-3-one

1,2-Benzisothiazolin-3-one (BIT) is a commonly used organic biocide containing an isothiazolone ring. However, it may have adverse effects on human health and its risk needs to be properly evaluated. Dermal exposure is the main route of BIT exposure, and co-exposed substances may affect its absorption. The dermal permeation profile of BIT has not been well-studied. This study aimed to investigate the dermal permeation profiles of BIT with or without cosmetic use. Dermal permeation profiles of BIT were investigated after infinite- (100 μg/cm²), or a finite-dose (10 μg/cm²) application with or without cosmetics using a minipig skin and Strat-M^®, an artificial membrane. A cream, lotion, and essence (namely, face serum) were pre-treated as representative cosmetics on minipig skin for 30 min, with BIT treatment afterward. After the treatment, BIT left on the skin surface was collected by cotton swabbing, BIT in the stratum corneum, by sequential tape stripping, and BIT retained in the remaining skin was extracted after cutting the skin into pieces before LC-MS/MS analysis. When an infinite dose was applied, permeation coefficients (K_p, cm/h) for minipig skin and Strat-M^® were 2.63 × 10⁻³ and 19.94 × 10⁻³, respectively, reflecting that skin permeation was seven to eight times higher in Strat-M^® than in the minipig skin. BIT, in the presence of cosmetics, rapidly permeated the skin, while the amount in the stratum corneum and skin deposit was reduced. We performed a risk assessment of dermally applied BIT in the absence or presence of cosmetics by calculating the skin absorption rate at 10 h based on the toxicological data from several references. The risk level was higher in the presence of essence as compared to lotion, which was higher than cream, which was higher than the control (non-treated). However, all of the margins of safety values obtained were greater than 100, suggesting that BIT is safe for use in dermally exposed consumer products. We believe that this research contributes to a greater understanding of the risk assessment of isothiazolinone biocides.

Il Silenzio: The First Renaissance Oil Painting on Canvas from the Uffizi Museum Restored with a Safe, Green Antimicrobial Emulsion Based on Citrus aurantium var. amara Hydrolate and Cinnamomum zeylanicum Essential Oil

Preserving artworks from the attacks of biodeteriogens is a primary duty of humanity. Nowadays, restorers use chemicals potentially dangerous for both artworks and human health. The purpose of this work was to find a green and safe formulation based on natural substances with fungicidal activity to restore ancient oil paintings, particularly “Il Silenzio” (by Jacopo Zucchi) preserved at the Uffizi Museum in Florence, Italy. The study was divided into two phases. First phase (in vitro study): three essential oils (EOs) and four hydrolates (Hys) were analysed by GC-mass spectrometry and in vitro tested against six ATCC strains of molds. An emulsion based on the more active natural compounds was tested on aged and unaged canvases samples to evaluate both their fungicidal activity and the impact on chemical-physical parameters. Finally, an in vivo toxicity test performed on the Galleria mellonella model assessed the safety for health. Second phase (in situ application): the emulsion was sprayed on the back of the painting and left to act for 24 h. Biodeteriogens present on the “Il Silenzio” painting were microbiologically identified before and after the treatment. The emulsion formulated with C. zeylanicum EO and C. aurantium var. amara Hy showed the best antifungal activity both in vitro and in situ without altering the chemical-physical characteristics of paintings. Furthermore, no in vivo toxicity was shown. For the first time, a green antimicrobial emulsion based on Hy and EO, safe for operators, was used to decontaminate an artwork colonised by fungi before the restoration practices.

Anti-Mold Effectiveness of a Green Emulsion Based on Citrus aurantium Hydrolate and Cinnamomum zeylanicum Essential Oil for the Modern Paintings Restoration

A modern painting is characterized by multi-material bases extremely exposed to biodeteriogenic attacks. The aim of this work was to test the antifungal effectiveness of a natural, eco-friendly, and safe emulsion based on Citrus aurantium L. var. amara hydrolate and Cinnamomum zeylanicum Blume (from bark) essential oil, named “Zeylantium green emulsion” (Zege), on modern paintings. Colored unaged and aged canvas samples, performed with modern techniques (acrylic, vinylic and alkyd), were used to test in vitro both the antifungal effectiveness of Zege and its impact on the chemical–physical characteristics. Microbiological tests were performed according to the EUCAST international guidelines. pH measurements and colorimetric analysis were performed on unaged and aged canvases before and after Zege spray treatment. Finally, in situ tests were performed using the spray emulsion on canvas samples obtained from Ilaria Margutti’s modern artwork, which had been colonized by molds. Microbiological tests on canvas prototypes showed a time- and dose-dependent effectiveness of the Zege spray. None of the techniques underwent relevant changes in pH. Only the acrylic colors were unaffected in the colorimetric analysis, among all colored unaged or aged canvases. Tests made with modern artwork samples confirmed the in situ antifungal effectiveness. The Zege spray showed encouraging results in regard to the use of this formulation in the restoration of modern paintings.

Targeted Delivery of Zinc Pyrithione to Skin Epithelia

Zinc pyrithione (ZnPT) is an anti-fungal drug delivered as a microparticle to skin epithelia. It is one of the most widely used ingredients worldwide in medicated shampoo for treating dandruff and seborrheic dermatitis (SD), a disorder with symptoms that include skin flaking, erythema and pruritus. SD is a multi-factorial disease driven by microbiol dysbiosis, primarily involving Malassezia yeast. Anti-fungal activity of ZnPT depends on the cutaneous availability of bioactive monomeric molecular species, occurring upon particle dissolution. The success of ZnPT as a topical therapeutic is underscored by the way it balances treatment efficacy with formulation safety. This review demonstrates how ZnPT achieves this balance, by integrating the current understanding of SD pathogenesis with an up-to-date analysis of ZnPT pharmacology, therapeutics and toxicology. ZnPT has anti-fungal activity with an average in vitro minimum inhibitory concentration of 10-15 ppm against the most abundant scalp skin Malassezia species (Malassezia globosa and Malassezia restrica). Efficacy is dependent on the targeted delivery of ZnPT to the skin sites where these yeasts reside, including the scalp surface and hair follicle infundibulum. Imaging and quantitative analysis tools have been fundamental for critically evaluating the therapeutic performance and safety of topical ZnPT formulations. Toxicologic investigations have focused on understanding the risk of local and systemic adverse effects following exposure from percutaneous penetration. Future research is expected to yield further advances in ZnPT formulations for SD and also include re-purposing towards a range of other dermatologic applications, which is likely to have significant clinical impact.