Emerging contaminants in aquatic environments and coastal waters affected by urban wastewater discharge in Thailand: An ecological risk perspective

Environmental fate of organic UV filters: Global occurrence, transformation, and mitigation via advanced oxidation processes

Organic UV filters are used in personal care products, plastics, paints, and textiles to protect against UV radiation. Despite regulatory limits, these compounds still enter the environment through direct wash-off during swimming, evaporation, leaching from products, and incomplete removal in wastewater treatment plants. They have been detected in various environmental matrices worldwide. Once in the environment, organic UV filters can undergo phototransformation and biotransformation, forming transformation products that, together with parent substances, pose health risks to humans and wildlife and harm marine ecosystems, especially coral reefs. The increasing concern over water scarcity and the environmental impact of pollutants underscores the importance of eliminating these contaminants from aquatic environments. This review primarily focuses on organic UV filters approved for use in sunscreens, many of which are also utilized in other materials, with a few exceptions including UV stabilizer UV-328. It includes an in-depth analysis of 155 peer-reviewed articles published from 2015 to 2024, assessing the concentrations of these filters in various environmental matrices, including water and solid matrices, air and biota. Moreover, this review explores the environmental transformation of these chemicals and assesses the effectiveness of advanced oxidation processes (AOPs) in removing these pollutants. The findings highlight the pervasive presence of organic UV filters in the environment and the promising potential of AOPs to mitigate the associated environmental challenges.

Dynamic impact of different human activities on the distribution of organic ultraviolet absorbers in coastal aquatic environments: A case study in Beibu Gulf, South China Sea

The increasing environmental concern surrounding organic ultraviolet absorbers (OUVAs) has prompted heightened attention, particularly their presence in personal care products (organic ultraviolet filters, OUVFs) and industrial products (organic ultraviolet stabilizers, OUVSs). This study investigates the impact of human activities and environmental factors on the occurrence, spatiotemporal distribution, and ecological risk of eight commonly utilized OUVFs and OUVSs in the coastal region of Beibu Gulf, South China Sea. The study area is characterized by multiple functional zones with distinct human activities. Results reveal elevated concentrations of OUVAs during summer compared to winter, attributed to increased residential usage, tourist activities, industrial releases, and intensified ultraviolet (UV) radiation. Interestingly, the proportion of OUVFs increases during summer, while OUVSs decrease. Correlation analysis between OUVAs and sampling sites reveals that tourism and domestic wastewater are the main contributors to OUVF contamination in summer, whereas mariculture and port trade significantly impact OUVS contamination in winter. The ecological risk assessment indicates predominantly low or medium risk levels for most OUVAs in both local seawater and freshwater ecosystems. Nevertheless, OUVFs, with a particular focus on 4-methylbenzylidene camphor (4-MBC), and OUVSs, specifically 2-(2-hydroxy-5-methylphenyl) benzotriazole (UV-P), exhibit a heightened risk compared to alternative substances. These findings provide crucial insights into the development of targeted mitigation strategies for OUVAs, taking into account the varying contamination levels of OUVFs and OUVSs resulting from diverse human activities, aiming to protect the health of aquatic ecosystems in diverse functional zones.

Synthetic musks in the natural environment: Sources, occurrence, concentration, and fate-A review of recent developments (2010-2023)

Synthetic musks (SMs) have served as cost-effective substitutes for natural musk compounds in personal care and daily chemical products for decades. Their widespread use has led to their detection in various environmental matrices, raising concerns about potential risks. Despite numerous studies on SM levels in different natural environments, a systematic review of their contemporary presence is lacking. This review aims to address this gap by summarising recent research developments on SMs in diverse natural environments, including river water, lake water, seawater, estuarine water, groundwater, snow, meltwater, sediments, aquatic suspended matter, soils, sands, outdoor air, and atmospheric particulate matter. Covering the period from 2010 to 2023, the review focuses on four SM categories: nitro, polycyclic, macrocyclic, and alicyclic. It systematically examines their sources, occurrences, concentrations, spatial and temporal variations, and fate. The literature reveals widespread detection of SMs in the natural environment (freshwater and sediments in particular), with polycyclic musks being the most studied group. Both direct (e.g., wastewater discharges) and indirect (e.g., human recreational activities) sources contribute to SM presence. Levels of SMs vary greatly among studies with higher levels observed in certain regions, such as sediments in Southeast Asia. Spatial and temporal variations are also evident. The fate of SMs in the environment depends on their physicochemical properties and environmental processes, including bioaccumulation, biodegradation, photodegradation, adsorption, phase exchange, hydro-dilution effects. Biodegradation and photodegradation can decrease SM levels, but may produce more persistent and eco-toxic products. Modelling approaches have been employed to analyse SM fate, especially for indirect processes like photodegradation or long-distance atmospheric transport. Future studies should further investigate the complex fate if SMs and their environmental influence. This review enhances understanding of SM status in the natural environment and supports efforts to control environmental contamination.

Adsorptive behavior of engineered biochar /hydrochar for tetracycline removal from synthetic wastewater

In this research, engineered biochar and hydrochar derived from paddy husk were compared for the adsorption tetracycline (TC) in water effluents. Biochar was produced at three different pyrolysis temperatures (e.g., 250 °C, 300 °C and 350 °C) while hydrochar was produced using three different HTC temperatures (e.g., 180 °C, 200 °C and 220 °C). The adsorptive experiments were performed for both biochar and hydrochar using well-defined experimental conditions: pH (3); initial TC concentration (10 mg/L); adsorbent dosage (1 g/L); and temperature (27 °C) to study their adsorptive performances (qe in mg/g). After selecting the best qe values for both biochar and hydrochar, both materials were modified using 20% H3PO4. A comprehensive scientific evaluation of both engineered biochar (EBC 350) and hydrochar (EHC 220) was performed using adsorption isotherm, adsorption kinetics, rate-limiting, and thermodynamics tests along with their characterization using FTIR and point of zero charge (pzc). The effects of temperature, dosage, and initial TC concentration on the adsorption process were studied for both EBC 350 and EHC 220. Acid activation improved the adsorptive performance of EHC 220 almost four times (from 1.9 to 7.5 mg/g), whereas adsorptive performance of EBC 350 improved 2.4 times from 3.8 to 9.1 mg/g. The best pH for TC adsorption onto EHC 220 was 5, whereas it was 3 for EBC 350. EBC 350 exhibited a good fit with the Freundlich model, whereas EHC 220 followed the Langmuir model. At 100 mg/L TC concentration, EHC 220 exhibited higher qe value (46.9 mg/g) compared to EBC 350 (41.7 mg/g). The Pseudo-first order kinetic model was the best fit for EHC 220 adsorption, whereas Pseudo-second order model was most suitable for EBC 350. The adsorption mechanisms involved in TC adsorption by EHC 220 included hydrogen bonding, hydrophobic effect, and π-π interaction, whereas cation exchange, mass diffusion, and π-π interaction were involved for EBC 350. The results of this study will facilitate the development of cost-effective filters with the incorporation of engineered biochar/engineered hydrochar for the active removal of emerging contaminants, like tetracycline, from wastewater so as to increase its reusable potential.

A critical review of distribution, toxicological effects, current analytical methods and future prospects of synthetic musks in aquatic environments

Synthetic musks (SMs) have gained widespread utilization in daily consumer products, leading to their widespread dissemination in aquatic environments through various pathways. Over the past few decades, the production of SMs has consistently risen, prompting significant concern over their potential adverse impacts on ecosystems and human health. Although several studies have focused on the development of analytical techniques for detecting SMs in biological samples and cosmetic products, a comprehensive evaluation of their global distribution in diverse aquatic media and biological matrices remains lacking. This review aims to provide an up-to-date overview of the occurrence of SMs in both aquatic and various biological matrices, investigating their worldwide distribution trends, assessing their ecological toxicity, and comparing different methodologies for processing and analysis of SMs. The findings underscore the prevalence of polycyclic musks as predominant SMs, with consumption of various products in different countries leading to contrasting distribution of contaminants. Furthermore, the migration of SMs from sediments to the water phase is investigated, indicating the role of solid-phase reservoirs. Incomplete degradation of SMs in the environment could contribute to their accumulation in aquatic systems, impacting the growth and oxidative stress of aquatic organisms, and having a possibility of genotoxicity to them. Human exposure data highlight substantial risks for vulnerable populations such as pregnant women and infants. Moreover, contemporary methods for SMs analysis are presented in this review, particularly focusing on advancements made in the last five years. Finally, research enhancement and critical questions regarding the analysis of SMs are provided, offering suggestions for future research endeavors.

Southeast Asia's environmental challenges: emergence of new contaminants and advancements in testing methods

Emerging contaminants, including pharmaceuticals, personal care products, microplastics, and per- and poly-fluoroalkyl substances, pose a major threat to both ecosystems and human health in Southeast Asia. As this region undergoes rapid industrialization and urbanization, the increasing presence of unconventional pollutants in water bodies, soil, and various organisms has become an alarming concern. This review comprehensively examines the environmental challenges posed by emerging contaminants in Southeast Asia and recent progress in toxicity testing methods. We discuss the diverse range of emerging contaminants found in Southeast Asia, shedding light on their causes and effects on ecosystems, and emphasize the need for robust toxicological testing methods. This review is a valuable resource for researchers, policymakers, and environmental practitioners working to mitigate the impacts of emerging contaminants and secure a sustainable future for Southeast Asia.

A contrast of emerging contaminants rac- and l-menthol toxicities to Microcystis aeruginosa through biochemical, physiological, and morphological investigations

Fragrances rac- and l-menthol extracted from peppermint are widely used and considered as emerging contaminants recently, which are persistent in the environment. Menthol has always been considered as a safe chemical for humans, but its potential adverse ecological effects on aquatic organisms and the toxic mechanisms have not yet been fully understood. The present study aims to investigate the physiological response of Microcystis aeruginosa after exposure to the two menthol isomers, and to explore the toxic mechanisms and ecological risks of these two chemicals. Results showed that rac-menthol exhibited a hormesis effect on the cell growth, chlorophyll a and protein contents; while l-menthol showed an inhibition effect. Adenosine triphosphate (ATP) content increased significantly at day 3 and then decreased markedly at day 6 after exposure to the two chemicals. Compared with rac-menthol, l-menthol can cause damage to the antioxidant system and plasmalemma more severely, promote the production and release of microcystins-LR (MC-LR) more dramatically, upregulate the expression of MC-transportation-related gene mcyH, and induce higher apoptosis rates. Overall results revealed that the toxic effects of l-menthol on cyanobacteria were significantly greater than those of rac-menthol. The significant increase in the malondialdehyde (MDA) content and the ultrastructural characteristics of the cells indicated that the plasma membranes were damaged. Thus, further attention should be paid to the scientific use, ecological and environmental risk assessment of chiral menthol. This study will also provide a scientific basis for future water quality criteria establishment on emerging contaminants such as fragrances.

Physiological impact of personal care product constituents on non-target aquatic organisms

Personal care products (PCPs) are products used in cleaning, beautification, grooming, and personal hygiene. The rise in diversity, usage, and availability of PCPs has resulted in their higher accumulation in the environment. Thus, these constitute an emerging category of environmental contaminants due to the potential of its constituents (chemical and non-chemical) to induce various physiological effects even at lower concentrations (ng/L). For analyzing the impact of the PCPs constituents on the non-target organism about 300 article including research articles, review articles and guidelines were studied from 2000 to 2023. This review aims to firstly discuss the fate and accumulation of PCPs in the aquatic environment and organisms; secondly provides overview of environmental risks that are linked to PCPs; thirdly review the trends, current status of regulations and risks associated with PCPs and finally discuss the knowledge gaps and future perspectives for future research. The article discusses important constituents of PCPs such as antimicrobials, cleansing agents and disinfectants, fragrances, insect repellent, moisturizers, plasticizers, preservatives, surfactants, UV filters, and UV stabilizers. Each of them has been found to display certain toxic impact on the aquatic organisms especially the plasticizers and UV filters. These continuously and persistently release biologically active and inactive components which interferes with the physiological system of the non-target organism such as fish, corals, shrimps, bivalves, algae, etc. With a rise in the number of toxicity reports, concerns are being raised over the potential impacts of these contaminant on aquatic organism and humans. The rate of adoption of nanotechnology in PCPs is greater than the evaluation of the safety risk associated with the nano-additives. Hence, this review article presents the current state of knowledge on PCPs in aquatic ecosystems.

Mitigating abortion risk of synthetic musk-contained body wash in pregnant women: Risk assessment and mechanism analysis

Synthetic musks (SMs), the widely used odor component in personal care products have attracted attention due to their environmental impacts, especially the abortion risks. Given that women comprise a significant consumer demographic for personal care products, it is imperative to promptly initiate research on avoidance strategies for pregnant women concerning their exposure to synthetic chemicals (SMs). This study tried to establish novel theoretical approaches to eliminate the abortion risks of SM-contained body wash by designing the SM-contained proportioning scheme and analyzing the abortion risk mechanisms. The binding energy of SMs to estrogen-progesterone protein complex was used as an indicator of the abortion risk. A total of 324 SM-contained body wash proportioning schemes were designed using full factorial design and No. 218 was found as the most effective formula for body wash proportioning with the binding energy value of 68.6 kJ/mol. Results showed the abortion risk could be effectively alleviated (reduced 0.6%-163.4%) by regulating the proportioning scheme of SM-contained body wash. In addition, the mechanism analysis of SM-contained proportioning scheme proportioning scheme found that xanthan gum and disodium EDTA played essential roles in reducing the abortion risk in pregnant women after exposure. The selection of proper body wash components for reducing the abortion risk of SMs on pregnant women was first proposed. It sheds lights on the potential risks of people's daily life and proposes risk-eliminating strategies.

Cosmetic UV filters in the environment-state of the art in EU regulations, science and possible knowledge gaps

OBJECTIVE

The aim of this work was to review the principals of environmental hazard and risk assessment (ERA) of cosmetic UV filters registered under EU REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals). Furthermore, effects as obtained from non-standardized testing methods and organisms from scientific literature were compared against the predicted no effect concentrations (PNECs) as derived based on standardized test methods for the various environmental compartments under REACH.

METHODS

The REACH dossiers at the ECHA webpage were screened for available information related to basic physico-chemical data (i.e. water solubility, octanol-water partitioning coefficient), PNECs and associated data (data basis, assessment factors (AFs)). Scientific literature was screened for available ecotoxicity data and the adverse effect levels were compared against the derived PNECs under REACH. Current approaches for environmental risk assessments of UV filters were evaluated for its applicability for a direct release scenario.

RESULTS

Under REACH, PNECs were derived for all hazardous UV filters. Although, PNECs were often derived for various environmental compartments (i.e. freshwater, marine water, sediment, soil), results from literature focused on aquatic data. Effects as observed within scientific literature matches in principle with the hazardous profile of the UV filters. Effects levels both on the acute and the chronic toxicity as retrieved from the non-standardized test organisms (literature) were above the derived PNECs under REACH. Currently, ERAs performed for cosmetic UV filters under REACH are solely tonnage driven and thus do not fully capture the use in sunscreens and associated leisure activities.

CONCLUSION

Existing EU REACH regulation is considered as sufficient to evaluate the environmental safety of UV filters used in sunscreens. To cover the direct release of UV filters due to various leisure activities into the aquatic freshwater and marine environment, an additional application-based ERA is considered necessary.

Fragrance materials affect life history parameters and gene expression in Daphnia magna: An emerging issue for freshwater ecosystems

A chronic toxicity test (21 d exposure) with the model organism Daphnia magna was performed to study the single-compound and combined effects of four fragrance materials (FMs), including musk xylene (MX), Celestolide™ (ADBI), Galaxolide™ (HHCB), and ethylene brassylate (MT). Furthermore, the transcriptional responses of ten target genes related to detoxification, molting and reproduction (DHR96, P-gp, CYP360A8, GST, CYP314, EcRb, Vtg, CAT, GPX, and GCLC) were determined by performing a quantitative real-time polymerase chain reaction (qRT‒PCR) after juvenile D. magna was exposed for 48 h. The results showed that MX, ADBI and HHCB affected development and reproduction after chronic exposure at a concentration of 10 μg L^-1. Conversely, MT did not affect reproduction, growth or molting during the 21 d exposure. In juvenile D. magna, gene expression was significantly altered by ADBI (DHR96, CYP260A8, and GCLC) and MX (DHR96, CYP360A8, EcRb, Vtg, CYP314, and GCLC) but not by HHCB. These results suggest that compared to biochemical measures, conventional biological endpoints provide more informative data regarding the effects of this FM. Compared to single substances in the chronic test, the mixture of the four FMs showed effects at lower concentrations and increased gene expression for EcRb and CYP314 during juvenile exposure, indicating a possible additive or synergistic effect of the four FMs compared to single compound exposure.

Enantioselective effects of chiral fragrance carvone (L- and D-carvone) on the physiology, oxidative damage, synthesis, and release of microcystin-LR in Microcystis aeruginosa

Carvone is a widely used chiral fragrance with two isomers (L-carvone and D-carvone). D-carvone smells like a caraway, whereas L-carvone smells like mint. Carvone imposes a potential burden on the aquatic ecosystem. However, the enantioselective toxic effect of carvone enantiomers on cyanobacteria remains unknown. This study aims to investigate the effects of L- and D-carvone on the physiological processes and related gene transcription (phoU, rbcL, and mcyH) in M. aeruginosa. Results showed that in the presence of L- and D-carvone, the oxidative damage and inhibitory effects on growth occurred in a concentration-dependent manner. The contents of chlorophyll a and protein and the rbcL transcription level were inhibited in M. aeruginosa. In addition, intracellular adenosine triphosphate (ATP) was heavily depleted because of various biological processes, including growth, oxidation reactions, and gene regulation. Meanwhile, L- and D-carvone stimulated the production and release of MC-LR and upregulated the expression level of the MC-LR-related gene mcyH. Intracellular MC-LR likely leaked to the water body under L-carvone exposure, posing a potential threat to the water environment. This study indicated that L- and D-carvone can regulate the physiological and metabolic activity of M. aeruginosa and show enantioselective toxic effects. The findings will also provide important insights into the influence of chiral fragrance on cyanobacterial blooms. Furthermore, this study will guide the safe application of chiral fragrance as personal care products.

Wastewater reclamation trends in Thailand

Thailand constantly faces the problem of water scarcity, resulting from an imbalance between available water supply and increasing water demand for economic and community expansion, as well as climate change. To address this shortage, wastewater reclamation is being planned and implemented throughout the country, along with a 20-year, long-term integrated water resource management plan. Significant opportunities from municipal wastewater treatment plants (WWTPs) are dependent on the following factors: the establishment of a reuse water framework and a tangible target for treated wastewater set by local government authorities; widespread recognition and adaptation of wastewater reuse measures in the agriculture, industry, tourism and service sectors regarding climate change and water stress; and the implementation of joint investment water reuse projects between private and government agencies. However, wastewater reclamation faces some significant challenges, specifically: the limitations of regulation and monitoring for specific reuse purposes; a lack of public confidence in the water quality; the limited commercial development of reclaimed wastewater research; and difficulties in self-sustaining business models through adapting circular economy principles. This study aims to provide an overview of the wastewater reclamation, present research trends, currently operating WWTPs as well as opportunities and challenges to speed up water reuse activities in Thailand.

Distribution and ecological risks of pharmaceuticals and personal care products with different anthropogenic stresses in a coastal watershed of China

The occurrences of pharmaceutical and personal care products (PPCPs) in both freshwater and sea have been widely reported. However, pollution control requires further information on riverine discharges with influence of land-based activities and associated risks to estuarine ecosystems. This study investigated the spatial occurrences and the relationship to sociodemographic parameters of 30 PPCPs in 67 rivers along the Bohai coastal region. The results showed that PPCPs were mainly deposited in aquatic phase, and the partitioning coefficient between water and sediment was highly determined by chemical properties. The levels of 30 PPCPs in rivers ranged from 8.33 to 894.48 ng/L, showing a large variance among regions. Caffeine, sulfamethoxazole, sulfamethazine, ofloxacin, anhydro-erythromycin, and trimethoprim were found to be the major pollutants. Multivariable analysis method was used to assess the correlation of PPCPs markers to socio-economic parameters. The results indicated that domestic emissions contributed most to the occurrences of PPCPs in the riverine water. Risk assessment result indicated that sulfamethoxazole, caffeine, tetracycline, and carbamazepine ranked top four with the highest risks to the most sensitive aquatic organisms. The results identified caffeine and carbamazepine with high detection frequency and concentration as the priority chemicals, while sulfamethoxazole and erythromycin should also be concerned due to their potential threats in specific rivers. This study provides valuable information for pollution control over PPCPs riverine discharges in estuarine regions.

Developmental toxicity assessment of 4-MBC in Danio rerio embryo-larval stages

Enormous production of cosmetic products and its indiscriminate use tends to discharge into the aquatic environment and might threaten non-target organisms inhabiting aquatic ecosystems. In the present study, developmental toxicity of 4-methylbenzylidene camphor (4-MBC), a widely used organic UV filter in personal care products has been evaluated using zebrafish embryo-larval stages. Waterborne exposure induced developmental toxicity and deduced 2.71 mg/L as 96 h LC₅₀ whereas embryos exposed to sub-lethal concentrations (50 and 500 μg/L) caused a significant delay in hatching rate, heart rate, reduced larval length, and restricted hatchlings motility besides the axial curvature. Chronic exposure to 10 dpf resulted in significant decrease in SOD activity at 500 μg/L with no changes in CAT level besides a significant increase in GST enzyme at 5 μg/L concentration in 5 dpf sampled larvae. However, all the three enzymes were significantly elevated in 10 dpf larvae indicating differential oxidative stress during the stages of development. Similar trend is noticed for acetylcholine esterase enzyme activity. A concentration dependent increase in malondialdehyde content was noted in larvae sampled at 5 and 10 dpf. In addition, multixenobiotic resistance (MXR) activity inhibition, and elevated oxidative tissue damage were noticed at 5 dpf with no significant changes in 10 dpf larvae. Furthermore, immunoblot analysis confirms 4-MBC induced apoptosis in zebrafish larvae with promoted cleaved Caspase-3, Bax and inhibited Bcl-2 proteins expression. Subsequently, docking studies revealed the binding potential of 4-MBC to zebrafish Abcb4 and CYP450 8A1 proteins with the binding energy of -8.1 and -8.5 kcal/mol representing target proteins interaction and toxicity potentiation. Our results showed that 4-MBC exposure triggers oxidative stress at sub-lethal concentrations leading to apoptosis, deformities and locomotion perturbations in developing zebrafish.This is first of its kind in systematically demonstrating developmental toxicity of 4-MBC and the information shall be used for aquatic toxicity risk assessment.

Study on the Combined Toxicities and Quantitative Characterization of Toxicity Sensitivities of Three Flavor Chemicals and Their Mixtures to Caenorhabditis elegans

It was shown that flavor chemicals with high toxicity sensitivities mean that small changes in their effective concentrations can lead to significant changes in toxicity. Flavors are widely used in personal care products. However, our study demonstrated that some flavor chemicals and their mixture rays have high toxicity sensitivities to Caenorhabditis elegans (C. elegans), which may have an impact on human health. In this paper, three flavor chemicals (benzyl alcohol, phenethyl alcohol, and cinnamaldehyde) were used as components of the mixture, and three binary mixture systems were constructed, respectively. Five mixture rays were designed for each mixture system by a direct equipartition ray design method. The lethal toxicities of the three flavor chemicals and mixture rays to C. elegans at three exposure volumes were determined. A new concept (inverse of the negative logarithmic concentration span (iSPAN)) was introduced to quantitatively evaluate the toxicity sensitivity of chemicals or mixture rays, and the combination index (CI) was employed to identify the toxicological interactions in the mixtures. It was shown that the three flavor chemicals as well as the binary mixture rays have a significant concentration-response relationship on the lethality of C. elegans. The iSPAN values of the three flavor chemicals and their mixture rays were larger than 3.000, showing very strong toxicity sensitivity to C. elegans. In mixture systems, the toxicity sensitivities of mixture rays with different mixture ratios were also different at different exposure volumes. In addition, it can be seen from the CI heat map that the toxicological interaction not only shows the mixture ratio dependence but also changes with the different exposure volumes, which implies that the mixtures consisting of flavor chemicals with high toxicity sensitivity have complex toxicological interactions. Therefore, in environmental risk assessment, special attention should be paid to chemicals with high toxicity sensitivities.

3D-QSAR-aided toxicity assessment of synthetic musks and their transformation by-products

Synthetic musks (SMs) are fragrance additives widely used in personal care products. SMs and their transformation by-products may reach the environment even after wastewater treatment, resulting in ecological and health concerns. The identification and toxicity assessment of SM by-products generated from different chemical and biological treatment processes have been rarely studied. This study established a 3D-QSAR model based on SMs' molecular structures (independent variable) and their lethal concentration (LC₅₀) of mysid (dependent variable). The developed model was further used to predict the LC₅₀ of SMs transformation by-products. Fifty-eight by-products of six common SMs (i.e., galaxolide (HHCB), tonalide (AHTN), phantolide (PHAN), traseolide (TRASE), celestolide (ADBI), and musk ketone (MK)) generated from biodegradation, photodegradation, advanced oxidation, and chlorination were identified through literature review and lab experiment as the model inputs. Predicted LC₅₀ results indicated that the toxicity of 40% chlorination by-products is higher than their precursors. Biodegradation is an effective method to treat AHTN. The advanced oxidation may be the best way to treat HHCB. This is the first study on biotoxicity of SM transformation by-products predicted by the 3D-QSAR model. The research outputs helped to provide valuable reference data and guidance to improve management of SMs and other emerging contaminants.

Effects of fragrance compounds on growth of the silkworm Bombyx mori

Due to the contamination and biological toxicity of some fragrance compounds, the environmental and ecological problems of such compounds have attracted more and more attention. However, studies of the toxicity of fragrance compounds for insects have been limited. The toxicity of 48 fragrance compounds for the silkworm Bombyx mori were investigated in this study. All of the fragrance compounds examined had no acute toxicity for B. mori larvae, but eight of them (menthol, maltol, musk xylene, musk tibeten, dibutyl sulfide, nerolidol, ethyl vanillin, and α-amylcinnamaldehyde) exhibited chronic and lethal toxicity with LC₅₀ values from 20 to 120 µM. In a long-term feeding study, musk tibeten, nerolidol, and musk xylene showed significant growth regulatory activity. They were also extremely harmful to the cocooning of B. mori, resulting in small, thin, and loose cocoons. Two important insect hormones, namely, juvenile hormone (JH) and 20-hydroxyecdysone (20-E), were quantified in hemolymph following chronic exposure to musk tibeten, nerolidol, and musk xylene, respectively. Musk tibeten significantly increased JH titer and decreased the 20-E titer in hemolymph, and musk xylene had a significant inhibitory effect on JH titer and increased 20-E titer. Although nerolidol had no effect on hormone levels, exogenous JH mimic nerolidol increased the physiological effects of JH and significantly slowed the growth rate of B. mori larvae. The results showed that these fragrance compounds could interfere with the insect endocrine system, leading to death and abnormal growth. The risk to insects of residual fragrance compounds in the environment is worthy of attention.

Polydopamine-coated magnetic nanoparticles for the determination of nitro musks in environmental water samples by stir bar sorptive-dispersive microextraction

Magnetic-based microextraction approaches have gained popularity in recent years due to the magnetic properties of the extraction phases allowing to handle them easier and more efficiently. This work describes a magnetic-based analytical method for the determination of the family of nitro musks in environmental water samples. These compounds have been of great concern due to their environmental impacts and potential health effects. The method is based on stir bar sorptive-dispersive microextraction (SBSDME) as extraction approach, prior to thermal desorption coupled to gas chromatography-mass spectrometry analysis (TD-GC-MS). For this purpose, polydopamine-coated cobalt ferrite magnetic nanoparticles (CoFe₂O₄@PDA) were used as extraction material. The main parameters involved in the extraction procedure (i.e., sorbent amount, extraction time and ionic strength) as well as in the thermal desorption step (i.e., temperature and desorption time) were evaluated in order to obtain the highest sensitivity. Under the selected conditions, the method showed good linearity, limits of detection and quantification in the low ng L^-1 range, intra- and inter-day repeatability with RSD <15%, and high enrichment factors (178-640). Finally, the method was applied to four environmental water samples of different origin. Relative recovery values ranging from 91 to 120% highlighted that the matrices under consideration do not affect the extraction process. This work constitutes the first time in which nitro musks compounds were selectively extracted by taking advantage the high potential that magnetic-based microextraction techniques offer, specially SBSDME.

Photochemical degradation of fragrance ingredient benzyl formate in water: Mechanism and toxicity assessment

Recently, fragrance ingredients have attracted increasing attention due to their imperceptible risks accompanying the comfortable feeling. To understand transformation mechanisms and toxicity evolution of benzyl formate (BF) in environment, its photochemical degradation in water was thoroughly studied herein. Results showed that 83.5% BF was degraded under ultraviolet (UV) irradiation for 30 min. Laser flash photolysis and quenching experiments demonstrated that triplet excited state (³BF*), O₂^•-, and ¹O₂ were three main reactive species found during BF photodegradation. Eight degradation intermediates, including benzaldehyde, benzyl alcohol, o-cresol, bibenzyl, benzyl ether, 1,2-diphenylethanol, benzoic acid, and benzylhemiformal, were mainly formed as identified by LC-Q-TOF/MS and GC-MS analyses. Furthermore, the degradation mechanism was explained as the bond cleavage of ³BF* and BF^•+, O₂^•-/¹O₂ oxidation, e_aq^- reduction, and ^•OH addition reactions. Aquatic assessment suggests that except benzyl alcohol, benzoic acid, and benzylhemiformal, all the products were persistent and could result in increased aquatic toxicity compared to original BF. Consequently, these degradation products may cause more toxicity to organisms if they remain accumulated in water environment for a long time.

Occurrence and Sources of Synthetic Musk Fragrances in the Sewage Treatment Plants and the Han River, Korea

Levels of synthetic musk fragrances (SMFs) and various personal care products (PCPs) were measured in the Han River and its tributaries in Seoul, Korea. The most abundant SMF in all river and PCP samples was 4,6,6,7,8,8-hexamethyl-1,3,4,7-tetrahydrocyclopenta(g)sochromene (HHCB), followed by 1-(3,5,5,6,8,8-hexamethyl-6,7-dihydronaphthalen-2-yl)ethanone (AHTN), musk ketone (MK), and 1,1,2,3,3-pentamethyl-2,5,6,7-tetrahydroinden-4-one (DPMI). The most abundant SMF in both PCPs and the Han River samples was HHCB, followed by AHTN. Moving from upstream to downstream in the Han River, the median SMF concentration was 6.756, 2.945, 0.304, and 0.141 μg/L in the sewage treatment plant (STP) influents, effluents, tributaries, and mainstream, respectively, implying that effective SMF removal was achieved during the sewage treatment process, followed by dilution in the receiving water. Four STPs using advanced biological treatment processes had removal efficiencies of 58.5%, 56.8%, and 38.1% for HHCB, AHTN, and MK, respectively. The highest SMF concentrations in the tributaries were observed at locations close to the STPs. Our study confirmed that the main source of SMFs in the receiving water were sewage effluents containing untreated SMFs, which largely originate from household PCPs, especially hair care products (e.g., shampoo) and perfumes.