Human health risk assessment of chloroxylenol in liquid hand soap and dishwashing soap used by consumers and health-care professionals

An effective and rapidly degradable disinfectant from disinfection byproducts

Chloroxylenol is a worldwide commonly used disinfectant. The massive consumption and relatively high chemical stability of chloroxylenol have caused eco-toxicological threats in receiving waters. We noticed that chloroxylenol has a chemical structure similar to numerous halo-phenolic disinfection byproducts. Solar detoxification of some halo-phenolic disinfection byproducts intrigued us to select a rapidly degradable chloroxylenol alternative from them. In investigating antimicrobial activities of disinfection byproducts, we found that 2,6-dichlorobenzoquinone was 9.0-22 times more efficient than chloroxylenol in inactivating the tested bacteria, fungi and viruses. Also, the developmental toxicity of 2,6-dichlorobenzoquinone to marine polychaete embryos decreased rapidly due to its rapid degradation via hydrolysis in receiving seawater, even without sunlight. Our work shows that 2,6-dichlorobenzoquinone is a promising disinfectant that well addresses human biosecurity and environmental sustainability. More importantly, our work may enlighten scientists to exploit the slightly alkaline nature of seawater and develop other industrial products that can degrade rapidly via hydrolysis in seawater.

Biodegradation of chloroxylenol by an aerobic enrichment consortium and a newly identified Rhodococcus strain

Chloroxylenol is a commonly used antimicrobial agent in antibacterial and disinfection products, which has been detected in various environments, such as wastewater treatment plants, rivers, seawater, and even drinking water, with concentrations ranging from ng/L to mg/L. However, the biodegradation of chloroxylenol received limited attention with only sporadic reports available so far. In this study, an efficient chloroxylenol-degrading consortium, which could degrade 20 mg/L chloroxylenol within two days, was obtained after five months of enrichment. Amplicon sequencing analysis revealed a decrease in the α-diversity (e.g., Shannon index and Inv_Simpson index) of the community during the domestication process. Microbial community dynamics were uncovered, with sequences affiliated to Achromobacter, Pseudomonas, and Rhodococcus identified as the most abundant taxonomic groups. From the consortium, five pure isolates were obtained; however, it was found that only one strain of Rhodococcus could degrade chloroxylenol. Strain Rhodococcus sp. DMU2021 could degrade chloroxylenol efficiently under the conditions of temperature 30-40 °C, and neutral/alkaline conditions. Chloroxylenol was toxic to strain DMU2021 and triggered both enzymatic and non-enzymatic antioxidant systems in response. This study provides novel insights into the biodegradation process of chloroxylenol, as well as valuable bioresources for bioremediation.

Chloroxylenol

The Expert Panel for Cosmetic Ingredient Safety reviewed updated information that has become available since their original assessment from 1985, along with updated information regarding product types, and frequency and concentrations of use, and reaffirmed their original conclusion that Chloroxylenol is safe as a cosmetic ingredient in the practices of use and concentration as described in this report.

Long-term influence of chloroxylenol on anaerobic microbial community: Performance, microbial interaction, and antibiotic resistance gene behaviors

The use of antibacterial and disinfection products is increasing in recent years. Para-chloro-meta-xylenol (PCMX), a widely used antimicrobial agent, has been detected in various environments. Herein, the impacts of PCMX with long-term exposure on anaerobic sequencing batch reactors were investigated. The high concentration (50 mg/L, GH group) PCMX severely inhibited the nutrient removal process, and the low concentration group (0.5 mg/L, GL group) slightly affected the removal efficiency which was recovered after 120 days of adaptation compared to the control group (0 mg/L, GC group). Cell viability tests indicated that PCMX inactivated the microbes. A significant reduction in bacterial α-diversity was observed in the GH but not the GL group. The microbial communities were shifted upon PCMX exposure, among which Olsenella, Novosphingobium, and Saccharibacteria genera incertae Sedis became the predominant genera in the GH groups. Network analyses showed that PCMX significantly reduced the complexity and interactions of the microbial communities, consistent with the negative impacts on bioreactor performance. Real-time PCR analysis indicated that PCMX affected the behavior of antibiotic resistance genes (ARGs), and the relationship between ARGs and bacterial genera gradually became complicated after long-term exposure. Most detected ARGs decreased on Day 60 but increased on Day 120 especially in the GL group, implying the potential risk of environment-relevant concentration of PCMX in the ecosystems. This study provides new insights into the understanding of the impacts and risks of PCMX on wastewater treatment processes.

Occurrence and stability of PCMX in water environments and its removal by municipal wastewater treatment processes

Para-chloro-meta-xylenol (PCMX) is a synthetic antiseptic used extensively to control the spread of germs and viruses, and as a result, enormous amount of PCMX could be discharged to water environments through drainage. To investigate the extent of PCMX contamination, water samples were collected from rivers and coastal waters in Hong Kong, and PCMX concentrations were determined by a newly developed method using liquid chromatography-tandem mass spectrometry combined with stable isotope-dilution. We discovered widespread PCMX pollution in the water environment. Then, we revealed for the first time that PCMX in wastewater is not effectively removed by chemically enhanced primary treatment (CEPT), one of the wastewater treatment processes used in Hong Kong (∼75% of wastewater) and other megacities around the world. This suggests that the CEPT effluent or the primary treatment effluent is an unintended continuous source of pollution for PCMX in water environments. Finally, we found that PCMX was relatively stable in the water environment and could pose a risk to aquatic organisms. These findings underscore the importance of raising public awareness of the environmental consequences from overuse of PCMX-based disinfectants and the need to reevaluate the various wastewater treatment processes in removing PCMX.

Testicular Toxicity of Chloroxylenol in Rats: Biochemical, Pathological and Flow Cytometric Study

Background

Chloroxylenol (para-chloro-meta-xylenol, PCMX) is claimed to be highly harmful both to humans and the environment. Toxic effects of PCMX on testicular functions are scarcely discussed in the literature.

Aim of Study

To study testicular toxic effects of PCMX on male Sprague-Dawley rats.

Materials and Methods

Forty animals were randomly distributed into three groups: negative control (G I), vehicle group (G II) and PCMX group (G III). PCMX group was subdivided into three subgroups: GIIIa: received PCMX 100 mg/kg, GIIIb: received PCMX 200 mg/kg and G IIIc: received PCMX 500 mg/kg. Hormonal assay included assessment of serum testosterone and estradiol levels. Histopathological examination of testicular tissue, analysis of cellular viability, necrosis and apoptosis in testicular tissue by flow cytometry, analysis of cellular DNA content and phases of cell cycle analysis by flow cytometry were also performed.

Results

Rats in the groups exposed to PCMX (G IIIa, G IIIb and G IIIc) had significantly lower estradiol and testosterone levels in comparison to control groups (G I and GII). Histopathological examination of testicular tissue of PCMX-exposed rats showed irregular crossly sectioned seminiferous tubules with their lumina containing scanty spermatids and spermatozoa. G IIIc animals showed eosinophilic proteinaceous material and vacuolated and necrotic interstitial cells of Leydig. Rats in PCMX-exposed groups (G IIIa, G IIIb and G IIIc) showed significantly lower testicular tissue viability in comparison to control groups (G I and G II). Rats in PCMX-exposed groups (G IIIa, G IIIb and G IIIc) showed significantly lower percentage of cells in the G0/G1 phase in comparison to control groups (G I and G II).

Conclusion

Rats exposed to PCMX had significant reduction in testosterone and estradiol levels with marked histopathological alterations affecting testicular tissues. These effects are dose-dependent.

Development and In Vitro Validation of Antibacterial Paints Containing Chloroxylenol and Terpineol

The establishment of self-disinfecting surfaces is an important method to avoid surface contamination. Recently, paints with antimicrobial properties have been developed to be applied on different surfaces, avoiding contamination with pathogens. In this work, self-disinfecting paints containing Chloroxylenol (CLX), Terpineol (TRP), and a mixture of both substances were developed. The goal was to evaluate and validate these paints using international standards for eventual commercialization and application in scenarios where surface contamination represents a problem. The paints were challenged with five different bacteria, Gram-positive and Gram-negative, before and after a scrub resistance test, where the long-term efficacy of the paints was evaluated. The antibacterial activity assessment was performed following ISO 22196 and JIS Z2801. In general, the paints showed very promising results, demonstrating their antibacterial activity, before and after scrub resistance test. The paint incorporating the mixture of CLX and TRP (CLX+TRP) stood out by revealing consistent results of antibacterial activity both before and after the scrub resistance test for most of the tested bacteria. The cytotoxicity of the developed paints was assessed in vitro by performing tests by direct contact with a human skin cell line, HaCaT, and testes on extracts with HaCaT and a pulmonary cell line, A549. The methodologies for cytotoxicity assessment were developed based in ISO 10993. For genotoxicity assessment, alkaline comet assay was conducted on both cell lines. The cytotoxicity assessment revealed promising results with the paints, demonstrating values of cellular viability above 70% and values of lactate dehydrogenase (LDH) leakage below 30%. The genotoxic assessment also revealed acceptable values of primary DNA damage for the developed antibacterial paints. In general, the selected methodologies presented good potential to be applied in the validation of both efficacy and safety of the antimicrobial paints, aiming to be applied in real scenarios.

Exploring the impact of daily food habit and modification of lifestyle for boosting immunity against COVID-19

The lockdown crisis due to novel coronavirus (COVID-19) mainly affected people who live under economic despair. Since boosting the immune system against the virus depends on a variety of food intake and lifestyle approaches; hence, it is crucial to know how daily food habits and lifestyle modification protect from pathogenic viral infections. This study focused on the benefit of plant-based foods, functional foods and the modified lifestyle which enhance the immunity of all aged groups against COVID-19 in Bangladesh. An online close-ended randomly selected structured multiple-choice questionnaire survey was conducted for people of different parts of Bangladesh (n = 161; male 51.55%, female 48.45%). The total percentage was counted for all variables. We found that plant-based foods, functional foods, and physical exercise played a vital role in enhancing people's immunity to control COVID-19. Plant-based micronutrients, nutraceuticals and antioxidants mainly took part to boost the immune system against the virus. Furthermore, physical activity had a vital role in improving people's immunity to manage COVID-19. Literature suggested that food habits, body immunity, awareness, stress and weight variation were affected by the COVID-19 pandemic. The vaccine or proper medication of COVID-19 still remains in an enigma. In this situation, boosting immunity to combat Coronavirus is the only way to survive.

Molecular evidence for suppression of swimming behavior and reproduction in the estuarine rotifer Brachionus koreanus in response to COVID-19 disinfectants

The increased use of disinfectants due to the spread of the novel coronavirus infection (e.g. COVID-19) has caused burden in the environment but knowledge on its ecotoxicological impact on the estuary environment is limited. Here we report in vivo and molecular endpoints that we used to assess the effects of chloroxylenol (PCMX) and benzalkonium chloride (BAC), which are ingredients in liquid handwash, dish soap products, and sanitizers used by consumers and healthcare workers on the estuarine rotifer Brachionus koreanus. PCMX and BAC significantly affected the life table parameters of B. koreanus. These chemicals modulated the activities of antioxidant enzymes such as superoxide dismutase and catalase and increased reactive oxygen species even at low concentrations. Also, PCMX and BAC caused alterations in the swimming speed and rotation rate of B. koreanus. Furthermore, an RNA-seq-based ingenuity pathway analysis showed that PCMX affected several signaling pathways, allowing us to predict that a low concentration of PCMX will have deleterious effects on B. koreanus. The neurotoxic and mitochondrial dysfunction event scenario induced by PCMX reflects the underlying molecular mechanisms by which PCMX produces outcomes deleterious to aquatic organisms.

Achieving stable and long-term partial nitrification of domestic wastewater by side-stream sludge treatment using a novel nitrite oxidation inhibitor chloroxylenol

Using inhibitors to selectively suppress the activity of nitrite-oxidizing bacteria (NOB) was an emerging way to rapidly achieve partial nitrification (PN). This study explored the feasibility of inactivating NOB by a novel inhibitor chloroxylenol (PCMX) in real domestic wastewater. Different frequencies (periodic strategy and concentrative time strategy) of PCMX side-stream sludge treatment were used to achieve and maintain PN during 250 days. PN was realized by PCMX treatment once a day about 20 days, due to the inhibition of Nitrospira. PN was completely destroyed after 212 days by periodic strategy, caused by the increase of Candidatus Nitrotoga. PN maintained without PCMX in following 201 days by concentrative time strategy. The risks of PCMX were assessed and almost no PCMX was detected in the effluent of mainstream sequencing batch reactors. These results meant PN realized by PCMX side-stream sludge treatment was feasible and concentrative time strategy was a better operating strategy.

Human exposure and health risk assessment of an increasingly used antibacterial alternative in personal care products: Chloroxylenol

The ban of some antibacterial ingredients, such as triclosan (TCS) and triclocarban (TCC), in personal care products (PCPs) in some countries (but not in China) has resulted in the increasing use of antibacterial alternatives, such as chloroxylenol (PCMX). However, the underlying human health risks and environmental impacts of PCMX exposure are largely unknown. Thus, the distribution characteristics of PCMX in PCPs and susceptible populations and the major routes and health risks of human exposure to PCMX were investigated. The PCMX, TCS, and TCC concentrations in PCPs, urine, drinking water, and surface water were determined using high-performance liquid chromatograph system equipped with diode array detector or triple quadrupole mass spectrometer. Results showed that PCMX is widely used in antibacterial hand sanitizers and household disinfectants in China. The addition of PCMX as an antibacterial ingredient in PCPs showed an increasing trend. The geomean concentrations of urinary PCMX in children and pregnant women were 21.6 and 31.9 μg·L^-1, respectively, which were much higher than TCS and TCC. A considerable concentration of PCMX ranging from 1.62 to 9.57 μg·L^-1 was observed in the aquatic environment, suggesting a potential massive-use of PCMX by humans. Human PCMX exposure via drinking was negligible because the PCMX concentrations in drinking water were less than 2.00 ng·L^-1. During human simulation experiment, we found that dermal contact was the dominant route of human PCMX exposure, accounting for 92.1% of the urinary PCMX concentration. The estimated daily intake of PCMX in 9.68% of children and 5.66% of pregnant women was higher than the reference dose. However, the urinary 8-hydroxy-2'-deoxyguanosine concentrations remained stable despite the elevated PCMX concentrations, thereby suggesting that daily PCMX exposure may not cause oxidative DNA damage in humans. Nevertheless, the potential ecotoxicity and health risks induced by chronic PCMX exposure cannot be ignored because of its increasing use.

Review, analysis, and education of antiseptic related ocular injury in the surgical settings

Preoperative skin antiseptic preparation is the gold standard for prevention of surgical infection. However, improper use of antiseptics may lead to severe ocular damage. Currently, the most common surgical antiseptics can be divided into aqueous-based and alcohol-based disinfectants, with chlorhexidine and iodine/iodophors being the two major components. Chlorhexidine has a persistent antimicrobial effect and is resistant to neutralization by blood or organic products in surgical wounds. Nevertheless, due to its toxicity to the ears, meninges, and eyes, application of chlorhexidine should be prohibited in these surgical fields. Iodine/iodophor is better tolerated by the ocular surface and is the recommended antiseptic for ophthalmic or head and neck surgeries close to the periocular area. Alcohol is less pricey and has a rapid antiseptic effect, though its desiccating effect and flammability restrict the use in mucosal or laser surgeries. The single or combined use of these antiseptics may inadvertently induce severe ocular damage, especially during time-consuming head and neck surgeries with prone, hyperextension, or lateral tilt positions, or surgeries under general anesthesia. Apart from the choice of antiseptics, appropriate selection and attachment of bio-occlusive dressings are key to avoiding antiseptic-related ocular injuries. In this review, we provided a comprehensive summary of the characteristics of antiseptics used in surgical settings and the possible mechanisms and outcomes of antiseptic-related ocular injuries. The prevention, diagnosis, and acute management of these complications were also discussed.

Degradation and mechanism analysis of chloroxylenol in aqueous solution by gas-liquid discharge plasma combined with ozonation

Gas-liquid discharge non-thermal plasma (NTP) coupled with an ozonation reactor was used to investigate the removal of a broad-spectrum antibacterial agent, chloroxylenol (PCMX), from aqueous solution. Under the same experimental conditions (discharge power of 50.25 W, the initial concentration of PCMX of 60 mg L-1, oxygen flow of 1.0 L min-1 and PCMX solution flow of 150 mL min-1), the PCMX degradation rates in the ozonation-only, NTP-only and NTP/O3 systems were 29.25%, 67.04% and 79.43%, respectively. Correspondingly, the energy efficiency has also been greatly improved, and increased to 0.45, 1.03 and 1.21 g kW-1 h-1. In addition, the effects of the initial concentration of PCMX, initial pH, the flow rate of oxygen, the addition of H2O2 and the addition of a radical scavenger on the degradation rate of PCMX were investigated in the NTP/O3 system. The degradation rate in acidic solutions was higher than that in alkaline solutions. During the removal process of PCMX, the rate of degradation was strongly increased with the addition of H2O2 and acutely decreased with the addition of the radical scavenger. Compared with deionized water the degradation rates of PCMX in secondary effluent were inhibited. Four main intermediates of PCMX degradation by the NTP/O3 system were identified by gas chromatography-mass spectrometry (GC-MS) and a possible degradation pathway of PCMX was proposed. The changes in toxicity of the PCMX solution during the NTP/O3 system oxidation process were also evaluated using bioluminescent bacteria and Quantitative Structure Activity Relationship (QSAR) models with the help of the ECOSAR software.

Effect of Triclosan and Chloroxylenol on Bacterial Membranes

Triclosan and chloroxylenol are broad-spectrum biocides used extensively in healthcare and consumer products. They have been suggested to perturb the structure of bacterial membranes, but studies so far have not considered that most bacterial membranes contain large amounts of branched-chain lipids. Here, molecular dynamics simulation is used to examine the effect of the two biocides on membranes consisting of lipids with methyl-branched chains, cyclopropanated chains, and nonbranched chains. It is shown that triclosan and chloroxylenol induced a phase transition in membranes from a liquid-crystalline to a liquid-ordered phase irrespective of the presence and nature of branching groups. At high concentration, chloroxylenol promoted chain interdigitation. Our results suggest that triclosan and chloroxylenol decrease the degree of fluidity of membranes and that this effect is more pronounced in bacterial membranes. As a result, their biocidal activity could be associated with a change in the function of membrane proteins.

Benzalkonium chloride, benzethonium chloride, and chloroxylenol - Three replacement antimicrobials are more toxic than triclosan and triclocarban in two model organisms

With the recent ban of triclosan (TCS) and triclocarban (TCC) from some personal care products, many replacement antimicrobial compounds have been used. Yet the potential health risk and environmental impact of these replacement compounds are largely unknown. Here we investigated the toxicological effects of three commonly used replacement antimicrobials, benzalkonium chloride (BAC), benzethonium chloride (BEC), and chloroxylenol (CX) to two model organisms, the nematode C. elegans and zebrafish (Danio rerio), and compared them to the banned TCS and TCC. We found that these replacement compounds are not any safer than the banned antimicrobials. In the worm, at least one of the three, BAC, showed comparable toxicity to TCS from organismal to molecular levels, with toxic effects occurring at lower hundred μg/L to lower mg/L levels. In the fish, all three compounds at the tested concentration ranges (0.05-5 mg/L) showed toxicity effects to zebrafish embryos, indicated by hatching delay or inhibition, embryonic mortality, morphological malformations, and neurotoxicity. BAC was the most toxic among the three, with acute lethal toxicity occurring at environmentally relevant concentrations (hundreds of μg/L), which is comparable to the banned TCC. However, the toxicity effects of BAC and TCC occurred within different time windows, potentially suggesting different mechanisms of toxicity. CX was the only compound that induced a "body curvature" phenotype among the five compounds examined, suggesting a unique mode of toxic action for this compound. Furthermore, all five compounds except TCS induced neurotoxicity in fish larvae, indicated by alterations in secondary motoneuron axonal projections. Such neurotoxicity has been largely understudied for these antimicrobials in the past years and calls for further investigations in terms of its underlying mechanisms and ecological significance. These findings strongly indicate that scrutiny should be put on these replacement compounds before their introduction into massive use in personal care products.

Antimicrobial agents, triclosan, chloroxylenol, methylisothiazolinone and borax, used in cleaning had genotoxic and histopathologic effects on rainbow trout

Triclosan (TRC), chloroxylenol (PCMX) and methylisothiazolinone (MIT) have been commonly used as an antimicrobial in soaps while borax (BRX) is used in household cleaning. After using these chemicals, they are washed down drains and getting into the aquatic ecosystem in which they may affect aquatic living organisms. In the present study, the chronic effects of TRC, PCMX, MIT and BRX on genotoxicity, gene expression and histopathology of rainbow trout (Oncorhynchus mykiss) were evaluated for 40 days under semi static condition. The comet assay results indicated that MIT, TRC and PCMX caused significant DNA damage to erythrocytes of the fish. Transcription of SOD, GPX1, GPX2, GSTA, HSP90BB, HSP90BA, CAT, and HSC70A genes were significantly regulated as a result of TRC, PCMX, MIT, and BRX exposure except PCMX exposed GSTA gene. Histological lesions were detected in gills, spleen liver, and trunk kidney of the fish. Lamellar fusion, hyperplasia and epithelial necrosis in gills, melanomacrophage centers and splenic necrosis in spleen, pyknotic nucleus, fat vacuoles, necrotic hepatocytes in liver, cloudy swelling in the tubules, renal tubule epithelial cells degeneration, glomerular capillaries dilation and glomerulus degeneration in kidney, were observed. Our study demonstrates the chronic toxic effect of TRC, PCMX, MIT, and BRX is high in rainbow trout. Therefore, we should be more careful when using these chemicals for cleaning in order to protect aquatic environment.