Assessing the Risk of Phthalate Ester (PAE) Contamination in Soils and Crops Irrigated with Treated Sewage Effluent

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.

Effects of irrigation water quality on the presence of pharmaceutical and personal care products in topsoil and vegetables in greenhouses

The presence of pharmaceutical and personal care products (PPCPs) in the environment has harmful effects on humans and the ecosystem. Reclaimed water irrigation may introduce PPCPs into the agricultural system. Here, a greenhouse experiment investigated the impact of reclaimed water irrigation on PPCP levels in the edible parts of vegetables and topsoil in the North China Plain in 2015 and 2016. Three treatment protocols were applied to each vegetable: irrigation with reclaimed water, irrigation with groundwater, and mixed irrigation with groundwater and reclaimed water (1:1, v/v). The total concentrations of 10 PPCPs in the topsoil (0-20 cm deep) and vegetables were 4.06-19.0 and 2.33-189 μg/kg, respectively. Among the target PPCPs, acetyl-sulfamethoxazole (AC-SMX) had the highest concentration in both soil and vegetables (0.23-10.8 and 1.56-116 μg/kg, respectively). The total concentration of the 10 PPCPs among cabbage, cauliflower, carrot, and cucumber were 13.1-28.1, 10.3-28.3, 2.33-4.04, and 110-189 μg/kg, respectively. The total hazard quotients for the mixture of target PPCPs across all vegetables were 0.0007 and 0.0003 for toddlers and adults, respectively. Compared with groundwater irrigation, reclaimed water irrigation did not evidently affect the vegetable yields, soil-vegetable PPCP concentrations, and BCFs. In this study, we found no potential hazard to human health when people consumed vegetables grown using reclaimed water irrigation.

Groundwater contamination pathways of phthalates and bisphenol A: origin, characteristics, transport, and fate - A review

Phthalic acid esters (PAEs) or phthalates and bisphenol A (BPA) are emerging organic contaminants (EOCs) that may harm biota and human health. Humans can be exposed to these contaminants by drinking water consumption from water sources such as groundwater. Before their presence in aquifer systems, phthalates and BPA can be found in many matrices due to anthropogenic activities, which result in long-term transport to groundwater reservoirs by different mechanisms and reaction processes. The worldwide occurrence of phthalates and BPA concentrations in groundwater have ranged from 0.1 × 10^-3 to 3 203.33 µg L^-1 and from 0.09 × 10^-3 to 228.04 µg L^-1, respectively. Therefore, the aim of this review is to describe the groundwater contamination pathways of phthalates and BPA from the main environmental sources to groundwater. Overall, this article provides an overview that integrates phthalate and BPA environmental cycling, from their origin to human reception via groundwater consumption. Additionally, in this review, the readers can use the information provided as a principal basis for existing policy ratification and for governments to develop legislation that may incorporate these endocrine disrupting compounds (EDCs) as priority contaminants. Indeed, this may trigger the enactment of regulatory guidelines and public policies that help to reduce the exposure of these EDCs in humans by drinking water consumption.

Composting and green technologies for remediation of phthalate (PAE)-contaminated soil: Current status and future perspectives

Phthalate esters (PAEs) are hazardous organic compounds that are widely added to plastics to enhance their flexibility, temperature, and acidic tolerance. The increase in global consumption and the corresponding environmental pollution of PAEs has caused broad public concerns. As most PAEs accumulate in soil due to their high hydrophobicity, composting is a robust remediation technology for PAE-contaminated soil (efficiency 25%-100%), where microbial activity plays an important role. This review summarized the roles of the microbial community, biodegradation pathways, and specific enzymes involved in the PAE degradation. Also, other green technologies, including biochar adsorption, bioaugmentation, and phytoremediation, for PAE degradation were also presented, compared, and discussed. Composting combined with these technologies significantly enhanced removal efficiency; yet, the properties and roles of each bacterial strain in the degradation, upscaling, and economic feasibility should be clarified in future research.

Characterization and quantification of endocrine disruptors in female menstrual blood samples

Selected endocrine disrupting chemicals (EDCs) were measured in adult female menstrual blood for the first time in Ghana, Africa, taking into account the importance of non-invasive means of matrices sampling in vulnerable groups, such as pregnant women, the elderly or chronically ill people. The menstrual blood samples of twenty (20) female adults between the ages of 25-45 years were sampled. The Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method was applied for the extraction and clean up, while gas chromatography-mass spectrometry (GC-MS) was used to measure the selected EDCs in adult female menstrual blood, taking into account the composition of menstrual discharge. Diethyl phthalate (DEP), Dibutyl phthalate (DBP) and Bis (2-ethylhexyl) phthalate (DEHP) were detected in all samples, whereas bisphenol A (BPA) was found in 13 participants. Dimethyl phthalate (DMP) was detected in 7 participants, Di-n-octyl phthalate (DNOP) was detected in 3 participants, Bis (2-ethylhexyl) adipate (DEHA) and pyrimidine were detected in 2 participants, while benzyl butyl phthalate (BBP) was detected in only 1 participant. The maximum concentration of DEP measured was 115.6 µg.L^-1and the minimum was 439 µg.L^-1. DEHP was the next most abundant phthalate with a maximum measured concentration of 982 µg.L^-1 and minimum of 95 µg.L^-1. The presence of parent phthalates (rather than metabolites) in menstrual blood of all participants studied suggests that bioaccumulation of selected phthalate compounds such as DEHP, DEP and DBP may be occurring with appreciable human toxicity though the carcinogenic exposure risks of DEHP via various routes were much lower than 1 × 10^-6 considered to be very low.

Characteristics and Health Risks of Phthalate Ester Contamination in Soil and Plants in Coastal Areas of South China

Phthalate esters (PAEs) are widely used as plasticizers in industrial and commercial products, and are classified as endocrine-disrupting compounds. In this study, we investigated the contamination characteristics and health risks of PAEs in the soil–plant system in coastal areas of South China. PAEs were detected in soil and plant samples at all 37 sampling sites. The total concentration of the 15 PAEs in soil samples ranged from 0.445 to 4.437 mg/kg, and the mean concentration was 1.582 ± 0.937 mg/kg. The total concentration of the 15 PAEs in plant samples ranged from 2.176 to 30.276 mg/kg, and the mean concentration was 8.712 ± 5.840 mg/kg. Di(2-Ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DnBP) were the major PAEs compounds in all samples. The selected contaminants exhibited completely different spatial distributions within the study area. Notably, higher concentrations of PAEs were found in the coastal Guangdong Province of South China. The average noncarcinogenic risks of Σ6 PAEs were at acceptable levels via dietary and nondietary routes. However, the noncarcinogenic risks posed by DEHP and DBP at some sampling sites were relatively high. Furthermore, dietary and nondietary carcinogenic risks were very low for BBP, but carcinogenic risks posed by DEHP via diet. The results suggest that PAEs in the coastal soil–plant system in South China, through human risk assessment, will induce some adverse effects on human health, especially in children. This study provides an important basis for risk management of PAEs in agriculture, and safety in coastal areas of South China.

Effects of reclaimed wastewater irrigation on soil-crop systems in China: A review

Reclaimed wastewater (RW) use represents a substantial opportunity to alleviate the growing scarcity of water for irrigation of agricultural crops in China. However, insufficient understanding of the effects and fates of possible contaminants in RW promotes concerns over crop safety and prevents the extensive incorporation of RW in agriculture. We reviewed the characteristics of contaminants in RW, the fate of contaminants in soil-crop systems, and the effects of RW irrigation on soil quality and crop growth in China. We found that concentrations of heavy metals in RW were higher than the permissible limits in some areas. The total concentrations and main categories of emerging contaminants and pathogens in RW varied markedly among municipal wastewater treatment plants, and the greatest risks of contamination were posed by ofloxacin, sulfamethoxazole, and erythromycin, the most frequently observed compounds with risk quotients >1. The negative effects of salts and nutrients in RW on soil quality and crop growth were minor and manageable. The accumulation of heavy metals and emerging contaminants in soils irrigated with RW did not pose an immediate risk to soils and crops. Changes in soil microbial populations, diversity, and activity caused by RW irrigation increased crop yields and protected crops against contaminants. However, attention is necessary to the risks of bioaccumulation in soils and crops of heavy metals, emerging contaminants, intermediate metabolites, and pathogens, and their effects on human health with long-term RW irrigation. We recommend irrigation practices, crop screening, soil treatments, prioritizing the risks of contaminants, and comprehensive management to increase safety in RW used for agricultural irrigation.

Uptake of a plasticizer (di-n-butyl phthalate) impacts the biochemical and physiological responses of barley

BACKGROUND

DBP is one of the most commonly used plasticizers for imparting desirable properties to polymers. The introduction of phthalates is reported to have occurred in the late 1920s, and there has been a significant rise in their release into the environment in past decades due to a lack of covalent bonding with the parent matrix. Because of their numerous applications in day-to-day life, phthalates have become ubiquitous and also classified as endocrine disruptors. Hence, several studies have been conducted to investigate the phthalate-mediated toxicities in animals; however, plants have not been explored to the same amount.

METHODS

Therefore, in the present study, the accumulation and translocation along with morpho-physiological perturbations in barley plants after 15, 30, 60, and 120 days of exposure to di-n-butyl phthalate (DBP) are investigated using standard protocols.

RESULTS

The maximal accumulation and translocation of DBP in the roots and shoots of barley plants was observed after 60 days of exposure. The exposure of DBP from 15 to 120 days was recorded to decline all the morphological indices (i.e., dry weight, net primary productivity, seed number per spike, and seed weight) of barley plants. The pigments content declined under DBP treatment for all exposure durations except 120 days exposure. Carbohydrate content increased after 15-30 days of exposure afterward it was observed to be decreased under 60 and 120 days of exposure. The protein content was declined in DBP stressed plants for 15-120 days. Proline content was increased in all exposure durations and maximal percent increase was recorded in 120 days of exposure. MDA content showed an increase at earlier exposure durations then followed by a decline in long-term exposure. Hydrogen peroxide content increased at all exposure durations. There were significant alterations observed in the activities of all antioxidative enzymes in comparison to the control. Furthermore, DBP stressed plants after 60 days were analyzed for the macromolecular variations using Fourier transform infrared spectroscopy (FTIR).

CONCLUSION

Thus, the outcomes of the current work provide an appraisal of phthalates' uptake and translocation mediated phytotoxic responses in barley plants. These observations can help in developing genetically modified edible plants that are resistant to phthalates uptake, thereby ensuring food security.

Major contaminants of emerging concern in soils: a perspective on potential health risks

Soil pollution by the contaminants of emerging concern (CECs) or emerging contaminants deserves attention worldwide because of their toxic health effects and the need for developing regulatory guidelines. Though the global soil burden by certain CECs is in several metric tons, the source-tracking of these contaminants in soil environments is difficult due to heterogeneity of the medium and complexities associated with the interactive mechanisms. Most CECs have higher affinities towards solid matrices for adsorption. The CECs alter not only soil functionalities but also those of plants and animals. Their toxicities are at nmol to μmol levels in cell cultures and test animals. These contaminants have a higher propensity in accumulating mostly in root-based food crops, threatening human health. Poor understanding on the fate of certain CECs in anaerobic environments and their transfer pathways in the food web limits the development of effective bioremediation strategies and restoration of the contaminated soils and endorsement of global regulatory efforts. Despite their proven toxicities to the biotic components, there are no environmental laws or guidelines for certain CECs. Moreover, the information available on the impact of soil pollution with CECs on human health is fragmentary. Therefore, we provide here a comprehensive account on five significantly important CECs, viz., (i) PFAS, (ii) micro/nanoplastics, (iii) additives (biphenyls, phthalates), (iv) novel flame retardants, and (v) nanoparticles. The emphasis is on (a) degree of soil burden of CECs and the consequences, (b) endocrine disruption and immunotoxicity, (c) genotoxicity and carcinogenicity, and (d) soil health guidelines.

Contaminants of emerging concern: sources, soil burden, human exposure, and toxicities.

The spatiotemporal distribution and potential risk assessment of 19 phthalate acid esters in wastewater treatment plants in China

The spatiotemporal distribution of phthalate acid esters (phthalates, PAEs) in wastewater treatment plants (WWTPs) in China was studied. The concentration of PAEs in influent and effluent increased from 2009 to 2016, indicating that the exposure level of PAEs in China increased continuously. Although the concentration of PAEs in sewage sludge in China ranged from 33.3 to 298 ug/g, there was no obvious spatial distribution pattern. Among the 19 PAE homologues, DEHP, DnBP, and DIBP were the most abundant phthalates detected in wastewater and sludge. Ecological risk assessment confirmed that there was a high chronic and acute risk of DIBP in effluent since 2015. Therefore, this study highlights the need for further studies on the exposure and toxicology of DIBP. Dietary intake accounted for more than 98% of the total risk, indicating that the risk of sludge application in agricultural land was much higher than that in nonagricultural land. The results from this study will provide valuable information for the safe disposal of sludge and wastewater.

Irrigation using hybrid constructed wetland treated domestic sewage: Uptake of phthalic acid esters and antibiotics by Ipomoea aquatica forssk

Irrigation with treated wastewater (WW) has been promoted to meet global water demands. This study investigates the occurrence and accumulation of targeted phthalic acid esters (PAEs) and antibiotics in soil and Ipomoea aquatica Forssk. irrigated with WW discharged from six hybrid constructed wetlands (HCWs), with evaluation of the associated human health risks. Results revealed that HCWs can effectively reduce the transfer of PAEs and antibiotics to soil and I. aquatica. HCW2 (VF-SF-HF) was found to be most efficient for the removal of PAEs (68.4%-95.3%) and antibiotics (28.5%-99.4%). Among the targeted PAEs, the concentration of bis (2-ethyl) hexylphthalate (DEHP) was the highest in irrigation water, soil and I. aquatica, while benzylphthalate (BBP) exhibited the highest bioconcentration factor (BCF_F). Among the targeted antibiotics, the concentration of sulfapyridine (SPD) was highest in various environmental media, while norfloxacin (NFX) exhibited the highest BCF_F. The properties of PAEs and antibiotics were found to be responsible for the differential uptake patterns. The estimation of the threshold of toxicological concern and hazard quotient showed that I. aquatica irrigated with HCWs treated wastewater presented a minor risk to human health. However, comprehensive safety evaluation is required for the widespread use of HCWs treated wastewater for irrigation purposes.

Biochemical pathways and enhanced degradation of dioctyl phthalate (DEHP) by sodium alginate immobilization in MBR system

As one of the most representative endocrine disrupting compounds, dioctyl phthalate (DEHP) is difficult to remove due to its bio-refractory characteristic. In this study, an immobilization technology was applied in an MBR system to improve the degradation of DEHP. The degradation efficiency of DEHP was significantly improved and the number of degradation genes increased by 1/3. A bacterial strain that could effectively degrade DEHP was isolated from activated sludge and identified as Bacillus sp. The degradation pathway of DEHP was analyzed by GC-MS. DEHP was decomposed into phthalates (DBP) and Diuretic sylycol (DEP), then further to Phthalic acid (PA). PA was oxidized, dehydrogenated, and decarboxylated into protocatechins, further entered the TCA cycle through orthotopic ring opening. The DEHP degrading strain was immobilized by sodium alginate and calcium chloride under the optimized immobilization conditions, and added to MBR systems. The removal rate of DEHP (5 mg/L) (91.9%) and the number of 3, 4-dioxygenase gene copies was significantly improved by adding immobilized bacteria. Micromonospora, Rhodococcus, Bacteroides and Pseudomonas were the dominant genuses, and the results of bacterial community structure analysis show that immobilization technology is beneficial to system stability. The results showed the potential applications of the immobilized technique in DEHP wastewater treatment in MBR.

Phthalate esters (PAEs) in soil and vegetables in solar greenhouses irrigated with reclaimed water

Phthalate esters (PAEs) in environments have become a public concern due to their harmful impacts on human and environments, and waste/reclaimed water irrigation maybe one of their sources in agricultural soil. A field experiment was setup to analyze the impacts of reclaimed water irrigation on levels of PAEs in vegetables and topsoil in solar greenhouse on the North China Plain during 2015 and 2016. There were 6 varieties of vegetables. For each variety, there were three irrigation treatments, including groundwater irrigation, reclaimed water irrigation, and alternative irrigation with groundwater and reclaimed water (1:1, v/v). The results show that the levels of the 6 PAEs in soil and vegetables varied between 0.73 and 9.48 mg/kg and 1.89 and 6.35 mg/kg, respectively. There were no significant differences for PAE concentrations among these different treatments at each vegetable harvest (p > 0.05). For both soil and vegetable samples, Di-n-butyl phthalate (DnBP) and Di (2-ethylhexyl) phthalate (DEHP) were the most dominant PAEs, with contents of 0.39-4.43 mg/kg and 0.25-6.31 mg/kg, respectively, contributing12.5-74.60% and 21.24-76.48% of the total 6 PAEs, respectively. The contents of DnBP and dimethyl phthalate (DMP) in topsoil were higher than the suggested allowable values, while the concentration of each individual PAE in topsoil was lower than the suggested cleanup objectives. The levels of 6 PAEs, DEHP, and DnBP in vegetables were below the reference doses. The yields of eggplant, cauliflower, bean, cabbage, cucumber, and carrot were 64.4-67.0 t/ha, 10.9-13.0 t/ha, 12.3-15.1 t/ha, 17.3-17.5 t/ha, 43.9-44.5 t/ha, and 19.0-22.9 t/ha, respectively, and no significant differences were found among these different treatments for each kind of vegetable. The bioaccumulation factors (BCFs) of 6 PAEs in vegetable samples were 0.43-5.79 and the corresponding values for each PAE were 0.00-27.32, respectively. The BCFs of butyl benzyl phthalate were the greatest (with a mean of 9.28), followed by DEHP (with a mean of 3.03) and DMP (with a mean of 1.90). In one word, the reclaimed water in this study did not affect the vegetable yields obviously. PAE levels in soil and vegetables irrigated with reclaimed water were in the acceptable range. Considering the difference of reclaimed water quality of Sewage Treatment Plants in different areas, so more reclaimed water from different areas is needed to assess the impacts of reclaimed water irrigation on PAE contamination in soil and vegetables.

Accumulation and metabolism of di(n-butyl) phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) in mature wheat tissues and their effects on detoxification and the antioxidant system in grain

Di(2-ethylhexyl) phthalate (DEHP) and di(n-butyl) phthalate (DBP) are the major phthalic acid esters to be used during the plastic manufacturing process; they have emerged as pollutants that result in serious environmental problems. However, their impacts on wheat at the reproductive stage remain unclear. Here, we examined the distribution of DEHP and DBP and their respective metabolites mono(2-ethylhexyl) phthalate (MEHP) and mono-n-butyl phthalate (MBP) in mature wheat, along with the mechanism of detoxification and oxidative burst in wheat grains under DBP and DEHP stress conditions in a pot experiment. High-performance liquid chromatography showed that the contents of DBP and DEHP, as well as their metabolites, i.e., MBP and MEHP, presented the highest values in the grain, followed by the stem, leaf, and root. Entry of DBP and DEHP into the grain from the soil induced the production of reactive oxygen species, accompanied by the upregulated expression and activity of the antioxidant enzymes (e.g., cytochrome P4503A4 and peroxidase). The metacaspase type I gene was also upregulated in response to DBP and DEHP stress in grains, which is indicative of programmed cell death to maintain normal physiological activities and to resist cell damage. DBP and DEHP stress-damaged cells in the grains underwent programmed cell death by upregulating the expression levels of the metacaspase type I gene. These results provide a new perspective for improving wheat tolerance to DBP and DEHP through the use of genetic engineering strategies.

Presence and Natural Treatment of Organic Micropollutants and their Risks after 100 Years of Incidental Water Reuse in Agricultural Irrigation

The aim of the research was to show the presence of micropollutants contained in the wastewater of Mexico City within the distribution canals of the Mezquital Valley (MV), as well as their retention in agricultural soil and aquifers. This system constitutes the world's oldest and largest example of the use of untreated wastewater for agricultural irrigation. The artificial recharge associated with the MV aquifers, with groundwater extracted for human consumption showing its importance as a water resource for Mexico City. The results of sampling show the presence of 18 compounds, with 10 of these considered as endocrine disruptor compounds (EDCs). The concentration of these pollutants ranged from 2 ng/L for 17 β-estradiol to 99 ng/L for DEHP, with these values decreasing throughout the course of the canals due to the wastewater dilution factor, their retention in agricultural soil, and their accumulation in the local aquifer. The main mechanisms involved in natural attenuation are adsorption, filtration, and biodegradation. Drinking water equivalent levels (DWELs) were estimated for 11 compounds with regard to acceptable daily intakes (ADIs), by assuming local exposure parameters for a rural Mexican population. These were compared with the maximum groundwater concentrations (Cgw) to screen the potential risks. The very low ratios of Cgw to DWELs indicate no appreciable human health risk from the presence of trace concentrations of these compounds in the source of drinking water in the MV. Despite this, far from being exceeded after more than 100 years of irrigation with residual water, the natural soil attenuation seems to remain stable.