Pollution characteristics and affecting factors of phthalate esters in agricultural soils in mainland China

Occurrence and health risk assessment of phthalate ester pollution in mulched farmland soil at a national scale, China

Phthalate esters (PAEs), widely used as plasticizers in mulching films, are emerging contaminants of concern in farmland soils. However, systematic data on their pollution characteristics and health risks in long-term mulched soils across China remain limited. In this study, 53 typically mulched farmland soil samples from 29 provinces were analyzed using gas chromatography-tandem mass spectrometry to investigate PAEs occurrence, spatial distribution, drivers, and risks. Method validation showed recoveries of 76.3-111.6 % for 16 PAEs, with limits of detection and quantification ranging from 0.2-3.7 ng/mL and 0.1-0.8 ng/mL, respectively. Results revealed Σ16PAE concentrations of 108-2970 μg/kg (mean: 852 μg/kg), with elevated levels in southern/eastern China. Di-isobutyl phthalate and di-butyl phthalate (DBP) showed 100 % detection rates, while DBP dominated contamination (mean: 323 μg/kg). Redundancy analysis identified precipitation and polyethylene microplastic abundance as key drivers. Although non-carcinogenic risks (hazard quotients <1) were low, di(2-ethylhexyl) phthalate posed carcinogenic risks exceeding 10⁻⁴ in 11.3 % of samples. This nationwide assessment highlights the urgency to regulate PAEs emissions from plastic mulch residues and prioritize child health protection in agricultural policies.

Uptake, translocation, and biotransformation of phthalate acid esters in crop plants: A comprehensive review

Phthalate acid esters (PAEs) are prevalent emerging contaminants in agricultural environments. The uptake of PAEs by crop plants has attracted extensive attention due to the risks posed to human health through transfer in food chains. Despite its importance, the interaction between PAEs and crop plants remains poorly understood. In this critical review, the occurrence of six priority control PAEs in various food crops grown in greenhouses and conventional farms is investigated, with detected concentrations reaching up to mg/kg (dry weight) levels. PAEs enter plants through roots, foliar gas, or foliar particle uptake. After entry, PAEs exhibit acropetal translocation from the root and basipetal translocation from the leaf. PAEs are transformed into various metabolites through hydroxylation, hydrolysis, and oxidation in phase I metabolism and further conjugated with biomolecules such as amino acids or sugars in phase II metabolism. Exposure to PAEs disrupts plant homeostasis and activated antioxidant enzymes to alleviate phytotoxicity. Dietary intake of PAEs-contaminated food crops presents potential risks to human health, particularly from fruit and root vegetables consumed by children, warranting specific attention. Furthermore, current knowledge gaps and future perspectives are proposed. This review provides a comprehensive assessment of the knowledge on the uptake, translocation, and transformation of PAEs in crop plants, emphasizing the need for an integrated investigation into the full life cycle of PAEs in plants to ensure food safety.

Corn-derived biochar mitigates oxidative stress and increases the content of essential elements in lettuce leaves grown in phthalate-polluted soil

Phthalic acid esters (PAEs) are recognized markers of microplastic pollution of the environment. The study assessed the effects of different biochars (BC) derived from sewage sludge (SS), corn residues (CR), sunflower (SF), and residues from biogas production (BG) on lettuce grown in PAEs-polluted soil. The BC varied in composition, porosity, and carbon structure, with CR-BC exhibiting the highest surface area and optimal aliphatic carbon content, making it the most effective for soil application. SS had the highest heavy metal and PAHs content, though within safe limits. Elevated phosphate levels in lettuce leaves, influenced by high PAHs, ash, and metal content in BC, were associated with increased CAT activity, indicating oxidative stress. A strong positive correlation was found between Cd and phosphate content, especially in SS-treated plants, and between phosphate and B. CR-BC limited heavy metal uptake while promoting beneficial nutrient interactions (such as between Ca and Mg). PAEs accumulation in lettuce was strongly negatively correlated with phosphate and B levels, suggesting these elements reduce pollutant uptake. Among treatments, CR-BC significantly reduced PAEs accumulation in lettuce leaves, which is critical for food safety. CR-BC also enhanced lettuce biomass, chlorophyll content, and nutrient uptake, and it decreased oxidative stress (lower levels of MDA and enhanced antioxidant enzyme activity of SOD and CAT). Conversely, BG-BC negatively affected plant growth, likely due to its high pH. Overall, the findings highlight the importance of BC feedstock properties, with corn-derived BC offering the most beneficial effects on plant health and pollutant mitigation in polluted soils.

Multimedia contamination characteristics, risk assessment, and source quantification of phthalates in the Shaying River Basin, China

Phthalates (PAEs), a class of typical endocrine-disrupting chemicals, have been widely detected in the environment due to their prevalent use as plasticizers in plastic products. This study investigates the multimedia contamination characteristics and potential ecological risks of PAEs in water, soil, and sediments of the Shaying River (SYR) Basin. A Geodetector model (GDM) was employed to identify the key drivers influencing the spatial distribution of PAEs, while factor analysis and the Positive Matrix Factorization (PMF) model were utilized to quantitatively apportion the potential sources of PAEs. Results revealed that the concentrations and spatial variation of PAEs were significantly higher in soil and sediments than in water, with distinct compositional profiles. Water samples exhibited a higher proportion of low-molecular-weight PAEs compared to soil and sediment, where high-molecular-weight PAEs prevailed to a lesser extent. Notably, among the 6 target PAEs, di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) were uniformly the primary PAEs in water, soil, and sediment of the SYR Basin, posing higher ecological risks to algae, crustaceans, amphibians, and fish compared to the other 4 PAEs. The spatial distribution of PAEs in the SYR Basin was comprehensively influenced by land use, precipitation, human activities, and soil types. Key factors vary across media, but the interaction between popdensity and other variables significantly enhanced the interpretation degree, jointly shaping the PAEs distribution patterns. Primary sources of PAEs in the basin were sewage and wastewater discharges (37.0%), nonpoint industrial sources (36.4%), and domestic sources (25.6%).

Soil enzyme activities and bacterial communities respond to co-exposure of butyl benzyl phthalate and TiO2 nanomaterials: Earthworm-mediated effects

Phthalic acid esters (PAEs) are widely used due to their advantageous properties, which enhance the durability, flexibility, and transparency of plastic products. Nanomaterials are also commonly used in plastic additives and agricultural fertilizers. However, both are easy to fall off, diffuse, and release into the environment during production, use, and disposal. The adsorption and transportation of PAEs by nanomaterials may jointly affect soil health. However, less attention is paid to the soil microorganisms caused by co-exposure between PAEs and nanomaterials, especially mediated by earthworms. The present study investigated the effects of BBP (1 mg kg-1) and nTiO2 (1 mg kg-1), alone and in combination, on soil enzyme activities, microbial composition, and bacterial community diversity, with and without mediation by the earthworm Metaphire guillelmi. Results showed that co-exposure to BBP and nTiO2 activated enzyme activities in earthworm-mediated soil. Both contaminants, individually and combined, altered the composition, distribution, diversity, and complexity of the soil bacterial community mediated by earthworms. Bacteroidetes, Proteobacteria, and Actinobacteria were the dominant phyla. However, the complexity of soil bacterial community networks decreased. The findings highlight the importance of considering co-exposure and soil fauna mediation when evaluating the ecological impacts of emerging contaminants and fill the lack of ecotoxicity data on the co-exposure of PAEs and nanomaterials, thus promoting the design and synthesis of safer and more efficient nanomaterials.

Screening, identification, metabolic pathway of di-n-butyl phthalate degrading Priestia megaterium P-7 isolated from long-term film mulched cotton field soil in Xinjiang

Introduction

Di-n-butyl phthalate (DBP) is one of the most widely used phthalate esters (PAEs) and is considered an emerging global pollutant. It may pose a significant threat to ecosystem and human health due to its residual hazards and accumulation in the environment. Bacteria-driven PAE biodegradation is considered an economical and effective strategy for remediating such polluted environments.

Methods

A DBP-degrading bacterium (P-7), was isolated from long-term film mulched cotton field soil. Its identity was confirmed via physiological, biochemical, and 16S rRNA gene analyses. The degradation conditions were optimized through single-factor experiments and response surface methodology (RSM).Furthermore, the whole-genome sequencing coupled with metabolomics was employed to elucidate metabolic mechanisms.

Results

Priestia megaterium P-7 (P. megaterium P-7) achieved 100% DBP removal within 20 h under optimal conditions and exhibited broad substrate specificity for other PAEs. Genomic analysis identified key genes (lip, aes, ybfF, estA, and yvaK) encoding esterases/hydrolases that initiate DBP catabolism, converting it to phthalic acid (PA). Subsequent decarboxylation (pdc, bsdCD, mdcACDH, and lysA) and dioxygenase-mediated steps integrated PA into the TCA cycle. Metabolomics revealed three degradation pathways: decarboxylation (DBP → MBP → BB → BA→Catechol), hydrolysis (DBP → MBP → PA → PCA → Catechol) and direct β-oxidation (DBP → DEP → MEP → PA → Catechol).

Conclusion

P. megaterium P-7 demonstrates exceptional degradation efficiency, substrate versatility, and environmental stress tolerance, making it a promising candidate for bioremediation of organic pollutants in contaminated soil.

Unveiling Human Exposure to Plasticizers through Drinking Tea: A Nationwide Study

Dietary intake represents a significant exposure pathway for phthalates (PAEs) and nonphthalate plasticizers (NPPs). However, the associated exposure risk linked to tea consumption remains unclear. This study analyzed 10 PAEs and 10 NPPs in six types of tea collected from 18 provinces in China. Both PAEs and NPPs were detected in all samples, with concentrations ranging from 309 to 8150 ng/g for PAEs and 42.2 to 899 ng/g for NPPs, respectively. Source apportionment analysis indicates that packaging materials are important sources of plasticizer contamination in tea. The concentrations of di-isobutyl phthalate (DiBP), benzyl-butyl phthalate (BzBP), and trioctyl trimellitate (TOTM) in tea exhibited a significant correlation with those found in packaging materials (r: 0.414-0.465, p < 0.01). Five transformation products (TPs) of plasticizers were identified in brewed tea samples through suspect screening analysis, raising concerns about their potential health effects. Comparisons suggest that cold brewing may result in higher plasticizer exposure than hot brewing after a single brew. However, as the brewing times for hot brewed tea increased, the risk of human exposure rose, ultimately exceeded that of cold brewed tea. This study provides national-scale data on plasticizer contamination in Chinese tea and valuable insights into tea consumption practices.

Assessing the distribution and human health risks of cationic surface-active agents in honey from China

Cationic surface-active agents (CSAAs) can persist in ambient water, be ingested by bees, and contaminate honey. Residues of CSAAs in honey remains unknown. This study measured the residual levels of five CSAAs in 271 honey samples from China using ultrahigh-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry. Residual benzalkonium chloride-C12 (BAC-C12), BAC-C14, BAC-C16, chlorhexidine (CHG), and 4-chloraniline levels were 0.0098-2.1468, 0.0061-1.7492, 0.0012-1.6305, 0.1576-0.8401, and 0.0019-0.0234 μg kg-1, respectively. CHG and all BAC were detected in 100 % of Z. jujuba, V. negundo var. heterophylla, wildflower, L. chinensis, and D. longan Lour honey; T. tuan honey had the lowest detection rate of any CSAAs. BAC-C16 had the highest residual level among all BAC tested in Central, North China. CHG levels were detected in 91.38 % of samples in North China and 100 % in East China. BAC-C12 was significantly higher in A. cerana versus A. mellifera honey (P < 0.001). Hazard quotient and Hazard index values indicate that CSAAs residuals in honey do not pose a health risk. Correlation analysis revealed a positive correlation between BACs resides in honey and surrounding environment. The findings suggest that continuous monitoring of CSAAs in honey is imperative to ensure its safety for human consumption, while also serving as an effective matrix to assess the environmental pollution of a given region.

Microbial augmented aerobic composting for effective phthalates degradation in activated sludge

Phthalate esters (PAEs) accumulated in activated sludge posed serious threats to agroecosystems and environment. Traditional aerobic (AE) and anaerobic (AN) composting were limited in achieving sustained PAEs degradation due to the single structure of microbial community. Here, the effectiveness and microbiological mechanisms of bacterial-augmented aerobic composting (AEB) in reducing activated sludge PAEs were investigated, with comparison of anaerobic composting (ANB). Results showed that AEB treatments significantly enhanced PAEs degradation efficiency through batch degradation experiments and microbial community analysis. At initial PAEs contamination levels of 50 mg/kg and 100 mg/kg, di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) removal rates increased by 2.11-3.93-fold and 2.18-3.36-fold, respectively. Notably, AEB treatment reshaped bacterial community structure, forming communities dominated by efficient PAEs-degrading bacteria. Network analysis revealed a more complex microbial interaction networks under AE treatment, with the numbers of node and connectivity being 1.5 and 1.8 times than that of AN treatment. Functional gene prediction indicated increased abundances of PAEs degradation-related functional groups. Environmental factor analysis demonstrated optimized conditions through pH control, oxygen supply, and active carbon-nitrogen metabolism. These findings provided important supports for safe activated sludge disposal and resource utilization.

Neonicotinoid metabolites in farmland surface soils in China based on multiple agricultural influencing factors: A national survey

Certain neonicotinoid metabolites (mNEOs) are causing widespread concern because they are equally or even more toxic than the parent NEOs. Currently, there is limited information on the distribution of mNEOs in soil. Especially, it is unknown that the effects of agricultural factors, such as plastic filming, plowing, irrigation, and fertilization, on mNEOs. This study is the first to reveal that mNEOs were commonly found in agricultural topsoil in China, with a geometric mean concentration of ΣmNEOs of 0.298 μg/kg. Among 31 provinces in Mainland China, Fujian had the highest mNEO residues, whereas Shanghai had the lowest. Among topsoil of various crop types, that of fruits and vegetables were found the highest mNEO residues. Furthermore, higher levels of film cover were associated with higher mNEO residues. Microplastics (MPs, serving as contaminant carriers) were positively correlated with mNEOs under field conditions, which was related to the adsorption capacity of microplastics and its influence on the soil conditions and the years of film cover. Alternatively, this study shows for the first time that irrigation water and manure might be sources of mNEO input into the soil, and that the plowing frequency might also influence on mNEOs.

The occurrence and safety evaluation of phthalic acid esters in Oasis agricultural soils of Xinjiang, China

Soil pollution caused by plastic residues containing additives (e.g. phthalic acid esters (PAEs)) is ubiquitous and has become a global concern. However, the distribution, accumulation, and potential risks associated with PAEs in agricultural soils have not been fully explored. This study quantified the types, concentrations, and distribution patterns of common PAEs in 29 agricultural soil samples collected from the Xinjiang Oasis, China. The results indicated that no significant variation in PAE concentrations across the oasis farmlands in Xinjiang. The PAEs were predominantly concentrated in the topsoil layer (0-20 cm), with an average concentration of 102.3 μg/kg, with some migration observed to the deeper soil layer (20-40 cm). The most abundant PAEs detected were Di (2-ethylhexyl) phthalate (DEHP), diisobutyl phthalate (DIBP), and diethyl phthalate (DEP), which accounted for 49.82 %, 23.74 %, and 20.96 % of the total, respectively. Furthermore, the concentrations of all PAEs were below China's soil quality risk control standards, and the non-carcinogenic risks to both adults and children were below the current threshold, indicating relatively low risks to both the human health and the environment. These findings are crucial for understanding the presence and safety evaluation of PAEs in Xinjiang Oasis farmland, and they provide important reference data for managing and controlling PAE contamination in agricultural soils.

Levels, distribution, and health risk assessment of phthalic acid esters in urban surface soils of Nagpur city, India

Surface soil samples from residential, commercial, and industrial areas of Nagpur city, India, were collected to study the levels, distribution, and impact of land use patterns on phthalic acid ester (PAEs) contamination. The Σ6PAEs concentrations in soils from residential, commercial, and industrial areas ranged between 6,493 to 13,195 µg/kg, 707 to 18,446 µg/kg, and 1,882 to 5,004 µg/kg with medians of 10,399, 6,199, and 3,401 µg/kg, respectively. Bis-2-ethylhexyl phthalate (DEHP) and dimethyl phthalate (DMP) were the dominant PAEs in the urban soils. The concentrations of DEHP and DMP were significantly greater than those in Ontario's soil quality guidelines. Among the PAEs, benzyl-butyl phthalate (BzBP) was found at relatively high concentrations (1,238 and 9,171 µg/kg) at two locations (i.e., S1 and S15). The chronic toxic risk (CTR) of PAEs was below the threshold, although the risk to children through ingestion and dermal exposure routes was greater than that to adults. The CR due to BzBP and DEHP were below the threshold level; however, the CR due to DMP was > 1 × 10-6 in residential areas. The cumulative CR of the six PAEs for adults (1.33-1.41 × 10-5) and children (8.08-8.89 × 10-6) surpassed the threshold level. This study revealed that PAEs in urban soils pose a risk to public health and require immediate risk reduction strategies.

Phthalate ester (PAEs) accumulation in wheat tissues and dynamic changes of rhizosphere microorganisms in the field with plastic-film residue

Phthalates acid esters (PAEs) have accumulated in soil and crops like wheat as a result of the widespread usage of plastic films. It is yet unclear, nevertheless, how these dynamic variations in PAE accumulation in wheat tissues relate to rhizosphere bacteria in the field. In this work, a field root-bag experiment was conducted to examine the changes of PAEs accumulation in the rhizosphere soil and wheat tissues under film residue conditions at four different growth stages of wheat, and to clarify the roles played by the microbial community in the alterations. Results showed that the plastic film residues significantly increased the concentrations of PAEs in soils, wheat roots, straw and grains. The maximum ΣPAEs concentration in soils and different wheat tissues appeared at the maturity, with the ΣPAEs concentration of 1.57 mg kg-1, 4.77 mg kg-1, 5.21 mg kg-1, 1.81 mg kg-1 for rhizosphere soils, wheat roots, straw and grains, respectively. The plastic film residues significantly changed the functions and components of the bacterial community, increased the stochastic processes of the bacterial community assembly, and reduced the complexity and stability of the bacterial network. In addition, the present study identified some bacteria associated with plastic film residues and PAEs degradation in key-stone taxa, and their relative abundances were positive related to the ΣPAEs concentration in soils. The PAEs content and key-stone taxa in rhizosphere soil play a crucial role in the formation of rhizosphere soil bacterial communities. This field study provides valuable information for better understanding the role of microorganisms in the complex system consisting of film residue, soil and crops.