Spatial distribution, historical trend, and ecological risk assessment of phthalate esters in sediment from Taihu Lake, China

Phthalic acid esters: Are they a big concern for rivers flowing into reservoir with ecological facilities?

The city-river-reservoir system is an important system for safeguarding drinking water. Phthalic acid esters (PAEs) are emerging contaminants in drinking water sources that are gaining attention, and they could pose risks to human health and aquatic organisms. In this study, field studies that lasted four years were conducted to analyze the concentrations, spatial-temporal distribution, and removal effects of six PAEs. The total concentrations of the Σ6PAEs in the water and sediment samples were 0.2-7.4 μg L-1 (mean: 1.3 μg L-1) and 9.2-9594.1 ng g-1 (mean: 847.5 ng g-1), respectively. Di-n-butyl phthalate (DBP) and, bis(2-ethylhexyl) phthalate (DEHP) were the predominant congeners, accounting for 57.2 % in the water samples and 94.1 % in the sediment samples. The urban area contributed 72 % of the PAEs in the system. A significant removal effect of PAEs was observed in the wetland, with a removal rate of 40.2 %. The partitioning of PAEs between the water and sediment was attributed to the removal of dimethyl phthalate and diethyl phthalate that occurred during the water phase, while the removal of DBP and DEHP primarily occurred during the sediment phase. The ecological risk calculation based on the sensitivity distribution model indicated that DBP (HQwater = 0.19, HQsediment = 0.46) and DEHP (HQwater = 0.20, HQsediment = 0.13) possessed moderate risks according to some water and sediment samples. The ecological projects were verified to be effective engineering strategies to reduce ecological risk in the drinking water source.

Historical sedimentary and evolutionary characteristics of POPs and EDCs in typical regions of the three Gorges reservoir, China

The historical sedimentary and evolutionary characteristics of persistent organic pollutants and endocrine disruptors in typical regions of the Three Gorges Reservoir are scarcely studied. Herein, the 96-year data on contaminated sediment history were reconstructed using Caesium 137 isotope dating. Polychlorinated biphenyl concentrations in the involved sediment cores ranged from non-detected (ND) to 11.39 ng/g. The concentrations of polycyclic aromatic hydrocarbons ranged from ND to 2075.20 ng/g and peaked in the 1970s owing to natural, agricultural and human activities. Further, phthalate esters (PAEs) and heavy metals (HMs) were detected at concentrations ranging from ND to 589.2 ng/g and 12.10-93.67 μg/g, respectively, with highest values recorded in the 1980s owing to rapid industrialisation and insufficient management during China's early reform and development stages. PAE and HM concentrations have increased in recent years, suggesting the need to focus on industrial and agricultural activities that have caused this impact. Although current pollutant concentrations in sediments do not pose a risk to the aquatic ecosystem, they should be continuously monitored.

Evidence of economic development revealed in centennial scale sedimentary records of organic pollutants in Huguangyan Marr Lake

Sedimentary records of polycyclic aromatic hydrocarbons (PAHs) and phthalates could reflect energy consumption and industrial production adjustment. However, there is limited knowledge about their effects on variations of PAH and phthalate compositions in the sediment core. The PAH and phthalate sedimentary records in Huguangyan Maar Lake in Guangdong, China were constructed, and random forest models were adopted to quantify the associated impact factors. Sums of sixteen PAH (∑16 PAH) and seven phthalate (∑7 PAE) concentrations in the sediment ranged from 28.8 to 1110 and 246-4290 μg/kg dry weight in 1900-2020. Proportions of 5-6 ring PAHs to the ∑16 PAHs increased from 32.0 %-40.7 % in 1900-2020 with increased coal and petroleum consumption, especially after 1980. However, those of 2-3 ring PAHs decreased from 30.7 % to 23.6 % due to the biomass substitution with natural gas. The proportions of bis (2-ethylhexyl) phthalate to the ∑7 PAEs decreased from 52.3 %-29.1 % in 1900-2020, while those of di-isobutyl phthalate increased (13.7 % to 42.3 %). The shift from traditional plasticizers to non-phthalates drove this transformation, though the primary plastic production is increasing. Our findings underscore the effectiveness of optimizing energy structures and updating chemical products in reducing organic pollution in aquatic environments.

The seasonal distribution of plasticizers in estuarine system: Controlling factors, storage and impact on the ecosystem

Plasticizers such as phthalate esters (PAEs) are commonly used in various consumer and industrial products. This widespread use raises valid concerns regarding their ubiquity in the environment and potential negative impacts. The present study investigates the distribution of eight common plasticizers in the largest European lagoon (Curonian Lagoon) located in the SE Baltic Sea. The concentration levels of plasticizers in the water column, containing both the dissolved and particulate-bound phases, and in sediments were evaluated to reveal seasonal patterns in distribution and potential effects on the lagoon ecosystem. A total of 24 water samples and 48 sediment samples were collected across all four seasons from the two dominant sedimentary areas within the lagoon. The average concentration of total PAEs in the water column ranged from 1 to 21 μg L-1, whereas sediment concentration varied from 5.0 to 250 ng g-1. The distribution of plasticizers was influenced by the patterns in hydrodynamics and water circulation within the lagoon. The confined south-central area contained a higher amount of PAEs in sediments, accounting for most of the lagoon's plasticizer accumulation. More than 7 tons of plasticizers are stored in the 5 upper centimetres of sediment, with over 3 tons persisting for more than five years. Di(2-ethylhexyl) phthalate (DEHP), Diisobutyl phthalate (DiBP), and Dibutyl phthalate (DnBP) were the most abundant PAE congeners, with DEHP posing the highest risk quotient to algae, based on water column concentration. Several other congeners demonstrated medium to high-risk levels for organisms living in the lagoon.

Assessment of phthalic acid esters plasticizers in sediments of coastal Alabama, USA: Occurrence, source, and ecological risk

Considering the ubiquitous occurrences and ecotoxicity of phthalates (PAEs), it is essential to understand their sources, distribution, and associated ecological risks of PAEs in sediments to assess the environmental health of estuaries and support effective management practices. This study provides the first comprehensive dataset on the occurrence, spatial variation, inventory, and potential ecological risk assessment of PAEs in surface sediments of commercially and ecologically significant estuaries in the southeastern United States, Mobile Bay and adjoining eastern Mississippi Sound. Fifteen PAEs were widely detected in the sediments of the study region, with total concentrations varying between 0.02 and 3.37 μg/g. The dominance of low-molecular-weight (LMW) PAEs (DEP, DBP and DiBP) relative to high-molecular-weight (HMW) PAEs (DEHP, DOP, DNP) indicates that residential activities have stronger impacts than industrial activities on PAE distributions. The total PAE concentrations displayed an overall decreasing trend with increasing bottom water salinity, with the maximum concentrations occurring near river mouths. These observations suggest that river inputs were an important pathway by which PAEs were transported to the estuary. Linear regression models identified sediment adsorption (measured by total organic carbon and median grain size) and riverine inputs (measured by bottom water salinity) as significant predictors for the concentrations of LMW and HMW PAEs. Estimated 5-year total inventories of sedimentary PAEs in Mobile Bay and the eastern Mississippi Sound were 13.82 tons and 1.16 tons, respectively. Risk assessment calculations suggest that LMW PAEs posed a medium-to-high risk to sensitive aquatic organisms, and DEHP posed a low or negligible risk to the aquatic organisms. The results of this study provide important information needed for establishing and implementing effective practices for monitoring and regulating plasticizer pollutants in estuaries.

Distribution, Source Apportionment and Risk Assessment of Phthalate Esters in the Overlying Water of Baiyang Lake, China

As a kind of endocrine disruptor compounds, the presence of phthalate esters (PAEs) has become a global concern. In this study, the pollution levels and spatial distribution of sixteen PAEs were investigated. Their potential sources and eco-environmental health risk were discussed in Baiyang Lake and its upstream rivers during different periods. PAEs were detected in all of samples, ranging from 1215 to 3014 ng·L-1 in October 2020 and 1384 to 3399 ng·L-1 in May 2021. Dibutyl phthalate (DBP) and di-isobutyl phthalate (DIBP) were the predominant monomers, with a detection rate of 100% and the highest concentrations in the overlying water. Restricted by multiple factors, the spatial distribution difference between Baiyang Lake and its upstream rivers in October was more significant than in May. The source apportionment revealed that agricultural cultivation and disorderly use and disposal of plastic products were the primary factors for the contamination. The human health risk assessment indicated that eight PAE congeners did not pose significant carcinogenic and non-carcinogenic harms to males, females and children. However, the ecological risks of DBP, DIBP and di (2-ethylhexyl) phthalate to algae, crustaceans and fish species were moderate or high-risk levels. This study provides an appropriate dataset for the assessment of the pollution of PEs to the water ecosystem affected by anthropogenic activities.

Phthalic acid esters in grains, vegetables, and fruits: concentration, distribution, composition, bio-accessibility, and dietary exposure

Grain, vegetable, and fruit samples were collected from Xi'an City in Northwest China and analyzed for the characteristics, bio-accessibility, and dietary exposure of 22 phthalic acid esters (PAEs). All the studied PAEs were ubiquitously detected, except for diethyl phthalate in vegetables and fruits. In grains, the sum of detectable PAEs (∑22PAEs) varied between 0.0840 and 40.0 µg/g, with a mean of 4.19 µg/g, presenting rice >  > beans > flour, and the major PAEs were di-n-butyl phthalate (DnBP) and bis(2-ethylhexyl) phthalate (DEHP). In vegetables, the ∑21PAEs ranged from 0.190 to 56.8 µg/g, with a mean of 8.07 µg/g, exhibiting leafy vegetables > root vegetables > fruits-vegetables > fungus > cauliflower > beans, and the main PAEs were di-iso-butyl phthalate (DiBP), DnBP, DEHP, di-iso-nonyl phthalate (DiNP), and di-iso-decyl phthalate (DiDP). In fruits, the ∑21PAEs varied between 0.300 and 12.6 µg/g, with a mean of 3.97 µg/g, presenting spring-winter season fruits > summer-autumn season fruits and shell-less fruits > shelled fruits, and the predominant PAEs were DiBP, DnBP, DEHP, DiNP, and DiDP. The bio-accessibility of PAEs in the gastrointestinal fluid simulant was higher than that in the single gastric or intestinal fluid simulant. The bio-accessibility of PAEs was correlated with the physiochemical properties of PAEs. The estimated daily intakes (EDIs) of human dietary exposure to PAEs were lower than the reference doses of United States Environmental Protection Agency and the tolerable dairy intakes (TDIs) of European Food Safety Authority (EFSA), except for the EDI of DnBP in the grains and DiBP in the vegetables higher than or close to the TDI of the EFSA. The research suggested that special attention should be paid to human dietary exposure to DnBP and DiBP, especially for children and adolescents.

National-scale urinary phthalate metabolites in the general urban residents involving 26 provincial capital cities in China and the influencing factors as well as non-carcinogenic risks

Phthalates (PAEs) are widely used in daily products but can cause a variety of adverse effects in humans. Few studies have been carried out on human internal exposure levels of PAEs on a large-scale, especially in developing countries. In the present study, 1161 urine samples collected from residents of 26 provincial capitals in China were analyzed for nine phthalate metabolites (mPAEs). The chemicals were widely detected, and the median specific gravity adjusted urinary concentration of Σ₉mPAEs was 278 μg/L. Di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DnBP) were the main parent PAEs that the residents were exposed to. Demographic characteristics, such as age and educational level, were significantly associated with PAE exposure. Children and the elderly had higher mPAE levels. Subjects with lower educational levels were more frequently exposed to DnBP and DEHP. However, mono-ethyl phthalate showed the opposite trend, i.e., higher concentrations in subjects aged 18-59 years and with higher educational levels. Geographic differences were detected at the national scale. Residents in northeastern and western China had higher levels of mPAEs than those in central China, most likely because of different industrial usage of the chemicals and different living habits and living conditions of the residents. Health risk assessment showed that hazard indices of PAEs ranged from 0.07 to 9.34, with 20.0% of the subjects being concern for potential non-carcinogenic risk as assessed by Monte Carlo simulation. DEHP and DnBP were the primary contributors, representing 96.7% of total risk. This first large-scale study on PAE human internal exposure in China provides useful information on residents' health in a developing country, which could be used for chemical management and health protection.

Spatial-temporal distributions and influential factors of phthalate acid esters in sediments of three lakes in Inner Mongolia

The spatiotemporal distributions, influential factors, and ecological risks of 15 phthalate acid esters (PAEs) in the sediments of three typical lakes in Inner Mongolia were investigated in this work. PAEs were widespread in all surface sediments ranging from 598.3 to 3873.8 μg/kg dry weight. Average PAE concentrations were highest in the surface sediments of Wuliangsuhai Lake followed by Daihai and Hulun Lakes, which were consistent with population density and intensity of anthropogenic activities. Dibutyl phthalate, di-iso-butyl phthalate (DIBP), and diethyl phthalate (DEP) were the dominant PAEs with similar abundance orders for the three lakes. The cold climate could explain the higher DEP abundance in the sediments of lakes at higher latitudes. The highest Σ PAE and most individual PAE concentrations were located at one of the discharge river estuaries because most PAEs were terrestrial pollutants. Σ PAE concentrations in the core sediments increased with years and fluctuations owing to the increasing PAE usage and input. The second highest PAE concentration peaks were associated with the high gross domestic product growth rates in 2003-2008. Redundancy analysis revealed that butyl benzyl phthalate and diamyl phthalate in the surface sediments of Hulun Lake were principally positively influenced by organic matter (65.6% contribution among geochemical variables), Fe oxides (25.1% contribution among metals), and Mn oxides (23.8% contribution among metals). The DIBP and DEP exhibited high risks to sensitive fish according to a risk quotient assessment. This work presents new insights into PAE status and deposition mechanisms in the lakes within high latitudes or cold climates, and provides important information for future environmental protection and management.

Engineering Transcription Factor XylS for Sensing Phthalic Acid and Terephthalic Acid: An Application for Enzyme Evolution

Poly(ethylene terephthalate) (PET) and phthalate esters (PAEs) are used extensively as plastics and plasticizers. Enzymatic degradation of PET and PAEs has drawn great attention in recent years; however, evolution of PET- and PAE-degrading enzymes is still a big challenge, partly because of the lack of an effective screening method to detect phthalic acid (PA) and terephthalic acid (TPA), which are the main hydrolysis products of PAEs and PET. Here, by directed evolution of a promiscuous transcription factor, XylS from Pseudomonas putida, we created two novel variants, XylS-K38R-L224Q and XylS-W88C-L224Q, that are able to bind PA and TPA and activate the downstream expression of a fluorescent reporter protein. Based on these elements, whole-cell biosensors were constructed, which enabled the fluorimetric detection of as little as 10 μM PA or TPA. A PAE hydrolase, GoEst15, was preliminarily engineered using this new biosensor, yielding a mutant GoEst15-V3 whose activity toward dibutyl phthalate (DBP) and p-nitrophenyl butyrate was enhanced 2.0- and 2.5-fold, respectively. It was shown that 96.5% DBP (5 mM) was degraded by GoEst15-V3 in 60 min, while the wild-type enzyme degraded only 55% DBP. This study provides an effective screening tool for directed evolution of PAE-/PET-degrading enzymes.

Investigation and risk assessment of dibutyl phthalate in a typical region by a high-throughput dual-signal immunoassay

The systematic investigation and risk assessment of dibutyl phthalate (DBP) were performed using an ultrasensitive dual-signal immunoassay in Zhenjiang, Jiangsu Province. In this study, C-dots@H-MnO₂ nanohybrid were synthesized and labelled on the secondary antibody to generate fluorometric and colorimetric signals. Attributed to the efficient catalysis of carbon dots (C-dots) and the high C-dots loading of hollow manganese (IV) oxide (H-MnO₂), the excellent sensitivity and low detection limits (0.243 and 0.692 μg/L respectively) were produced. Based on the proposed method, 25 water and 119 beverage samples were investigated. DBP was found in all water samples and 65.5% of beverage samples, with the concentrations varying in 16.5-32.1 μg/L and 0-553 μg/L, respectively. In addition, the mean concentration (22.9 μg/L) in waters was decreased significantly compared with that detected in 2016 (43.5 μg/L) by our Lab. For beverages, a similar phenomenon was observed by the measured concentrations from coffee. Furthermore, the potential ecological risks of DBP were evaluated, the results indicated that human activities had caused serious pollution and high risks to the local aquatic ecosystem. On the other hand, the results of health risk assessment suggested that DBP in beverages might not cause obvious side effects to local residents.