Higher Molecular Weight Phthalate Esters Research Articles

Occurrence, spatial distribution and ecological risk assessment of phthalate esters in water, soil and sediment from Yangtze River Delta, China

A total of 96 water, soil, and sediment samples, collected from 32 sampling sites in the Yangtze River Delta (YRD) region, were analyzed for 9 phthalate esters (PAEs). The sum concentrations of 9 PAEs (∑9PAEs) in the water, soil, and sediment samples were 2.23–6.30 μg L−1 (mean: 4.11 μg L−1), 155–1410 μg kg−1 (408 μg kg−1), and 30.1–16,000 μg kg−1 (1200 μg kg−1), respectively. Among the 9 PAEs, di-n-butyl phthalate (DBP), bis(2-ethylhexyl) phthalate (DEHP), and di-isobutyl phthalate (DIBP) are the predominant congeners in the YRD region. DBP was the dominant PAE congener in water, accounting for 50.6% of the Σ9PAEs, while DEHP was the predominant one in soil and sediment (accounting for 69.6% and 83.1% of the Σ9PAEs, respectively). Soil and sediment samples collected from Wuxi city manifested relatively higher PAE concentrations. The partitioning of PAEs between water and sediment was attributed to the fact that low molecular weight PAEs (e.g., dimethyl phthalate (DMP) and diethyl phthalate (DEP)) were dominant in water, medium molecular weight PAEs (e.g., BzBP) were close to the equilibrium between sediment–water, and high molecular weight PAEs (e.g., DEHP) were more prevalent in sediment. The ecological risk assessment of PAEs in the surface water showed that the potential environmental risks followed the order of DEHP > DIBP > DBP > DMP > DEP. Comparatively, DEHP posed high ecological risk to sensitive algae, crustaceans and fish, while DMP and DEP exhibited low risk. In the sediment, DIBP exhibited a high risk to the sensitive fish, whereas DMP, DEP, DBP and DEHP displayed no risk.

Evaluating the spatial distribution and source of phthalate esters in the surface water of Xingkai Lake, China during summer

Increasing production and usage of phthalate esters (PAEs) has made them ubiquitous in the environment. In this study, the distribution and source of PAEs in the surface water of Xingkai Lake, China were analyzed. The concentration of ΣPAEs in the water of Xingkai Lake ranged from 0.26 to 3.83 μg/L with a median of 1.28 μg/L. It was observed that the difference in the concentration of ƩPAEs between the small and large Xingkai Lakes is not significant (p > 0.05). Agriculturally dominated land use types in the Xingkai Lake watershed may be mainly responsible for the occurrence of PAEs in this Lake. The distribution of butyl benzyl phthalate (BBP) in small and large Xingkai Lakes showed a significant difference (p < 0.05) which may be related to anthropogenic activities. ƩPAEs in the water of Xingkai Lake demonstrated significant positive correlations with the ratio of total nitrogen (TN) to concentration of TP (rp = 0.697, p < 0.01) and the concentration of suspended particulate organic matter (SPOM) (rp = 0.345, p < 0.05). These results further indicate that the concentration of nutrients from agricultural activity had an impact on the concentrations of PAE in the lakes. Furthermore, the more SPOM would lead to more suspension of PAEs in the water phase. The source analysis of PAEs showed that high molecular weight PAEs were dominant in the Xingkai Lake which may be arising from the combustion of plastics or from building materials and household furnishing.

Bacterial enzyme based spectrophotometric determination of phthalate esters in drinking water stored in PET bottles

Phthalate esters (PEs) are major water pollutants raising concern of endocrine disruption on daily uptake even at nano-gram level. Among PEs, di-(2-ethylhexyl) phthalate (DEHP) is a high molecular weight PE predominently found in most of the plastic and PVC products. In the present study, daily consumption of PET bottle stored drinking water was taken into account; where leaching PEs occurs easily from its supporting matrix. Determination of PEs in water and other environmental samples by conventional methods involves solvent extraction and sophisticated instruments. To overcome such scenario, in the present study enzyme based spectrophotometric determination of PEs is been proposed. Purified bacterial esterase of 38 kDa is used in the study with optimised pH, temperature and T50 as 7.0, 40 °C and 65 °C. The Km and Vmax values of the purified esterase were derived to be 138.88 µM for DEHP as substrate and 3.15 µmol of phthalic acid liberated min−1 mL−1. Inhibitory effect of metals, minerals and salts that are commonly present in water was assessed at two varied concentrations: 10 and 30 ppm. Magnesium, sodium and mercury exhibited maximum inhibition of 41–47% when compared to other inhibitors. In spectrophotometric determination, upon enzymatic reaction of purified esterase with condensed PET bottle stored drinking water, PE concentration was quantified to be 0.01–0.54 µg L−1. LoD and LoQ based on method validation were calculated to be 0.4 and 1.18 µg L−1. Thus, this study would serve to overcome tedious solvent based extraction process and sophisticated instruments in the detection and quantification of PEs.

Persulfate activation with rice husk-based magnetic biochar for degrading PAEs in marine sediments.

Phthalate esters (PAEs) can interfere with the endocrine systems of humans and wildlife. The main objective of this study was to evaluate the suitability of a composite for remediating marine sediments contaminated with PAEs. The composite was synthesized with magnetite nanoparticles (Fe3O4) and rice husk biochar (RHB) by using chemical co-precipitation. Fe3O4, RHB, and Fe3O4-RHB substantially activated sodium persulfate (Na2S2O8, PS) oxidation to form SO4-• and thus degrade PAEs in marine sediments in a slurry system. The morphology and structural composition of the magnetic composites were examined using XRD, FTIR, environmental scanning electron microscopy-energy-dispersive X-ray spectrometry, and superconducting quantum interference device. The Fe3O4-RHB composites were confirmed to be prepared successfully. The influences of various parameters, including the PS concentration, composite loading, and initial pH, were investigated. The concentration of high-molecular-weight PAEs (HPAEs) in sediment was much higher than that of low-molecular-weight PAEs (LPAEs); di-(2-ethylhexyl) phthalate (DEHP) was an especially salient marker of PAE contamination in sediments. Furthermore, increasing the PS and Fe3O4-RHB doses accelerated PAE oxidation at pH3.0; 83% degradation of PAEs was achieved when the PS and Fe3O4-RHB concentrations were increased to 2.3 × 10-2mM and 1.67g/L, respectively. LPAEs such as dibutyl phthalate (DnBP) are easier to degrade than HPAEs such as DEHP, diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP). In addition, possible activation mechanisms of the interactions between S2O82- and Fe2+/Fe3+ on the Fe3O4 surface, which involve an efficient electron transfer mediator of the RHB oxygen functional groups promoting the generation of SO4-• in the Fe3O4-RHB/PS system, were clarified. Thus, the Fe3O4-RHB/PS oxidation process is expected to be a viable method for remediating PAE-contaminated marine sediment.

Effects of Push/Pull Perfusion and Ultrasonication on the Extraction Efficiencies of Phthalate Esters in Sports Drink Samples Using On-line Hollow-Fiber Liquid-Phase Microextraction

In previous studies, we developed a process, on-line ultrasound-assisted push/pull perfusion hollow-fiber liquid-phase microextraction (UA-PPP-HF-LPME), combining the techniques of push/pull perfusion (PPP) and ultrasonication with hollow-fiber liquid-phase microextraction (HF-LPME), to achieve rapid extraction of acidic phenols from water samples. In this present study, we further evaluated three more-advanced and novel effects of PPP and ultrasonication on the extraction efficiencies of neutral high-molecular-weight phthalate esters (HPAEs) in sports drinks. First, we found that inner-fiber fluid leakage occurs only in push-only perfusion-based and pull-only perfusion-based HF-LPME, but not in the PPP mode. Second, we identified a significant negative interaction between ultrasonication and temperature. Third, we found that the extraction time of the newly proposed system could be shortened by more than 93%. From an investigation of the factors affecting UA-PPP-HF-LPME, we established optimal extraction conditions and achieved acceptable on-line enrichment factors of 92-146 for HPAEs with a sampling time of just 2 min.

Determination of phthalate ester congeners and mixtures by LC/ESI-MS in sediments and biota of an urbanized marine inlet.

Phthalate esters (PEs) are a group of widely used commercial chemicals consisting of many different congeners. Concentrations of di(2-ethylhexyl) phthalate ester in the parts per million range have been observed in sediments from locations in North America and Europe. However, sediment and biota concentrations of other widely used PEs (i.e., dibutyl phthalate, diisononyl phthalate, and diisodecyl phthalate) are rare and often in doubt because of analytical difficulties. One of the problems is that commercial formulations predominantly consist of PEs with a specific molecular weight but include many isomers within each molecular weight class. Currently there are no analytical methods or required standards to fully separate PEs into the different molecular weight classes corresponding to the formulations from which they originate. Hence, ambient total and mixture-specific PE concentrations do not exist. This study presents a new method based on reversed-phase liquid chromatography/ electrospray ionization mass spectrometry (LC/ESI-MS) for the quantitative determination of individual PEs, including six congeners on the U.S. EPA Priority pollutant list and several commercial PE isomeric mixtures, in complex environmental matrixes. The method is applied to determine the composition of PE concentrations in sediments and fish in an urbanized marine ecosystem. PE fingerprints in sediments show a predominance of high molecular weight PEs and match per capita consumption levels of PEs. Fingerprints in fish tissue show a predominance of low molecular weight PEs and do not match per capita consumption levels. The findings indicate that the higher molecular weight PEs are less biologically available than the lower molecular weight ones.

Biodegradability of Di(2-Ethylhexyl) Phthalate by Pseudomonas Fluorescens FS1

Di(2-ethylhexyl)phthalate (DEHP), one of high-molecular weight phthalate esters (PAEs), is used in the manufacturing of polyvinylchloride (PVC) resins, polyvinyl acetate, cellulosics, and polyurethanes, and contributes to environmental pollution. In this article, the characteristics of DEHP biodegradation by an effective degradation bacterium, Pseudomonas fluorescens FS1 that isolated from the activated sludge at a petrochemical factory, was capable of using phthalate esters as the sole carbon and energy source, were investigated. Experimental results showed that the biodegradation of DEHP by P. fluorescens FS1 could be described by the first-order reaction model, which could be expressed as: lnC = -0.0688t + A, and the half-life of DEHP biodegradation was 10.07 d when the initial concentrations of DEHP were less than 50 mg L −1 . The inhibition effects of DEHP as a substrate had become predominant above the concentration of 50 mg L −1 . The PAEs-degrading enzyme of P. fluorescens FS1, mainly located in the soluble part and the particle of cytoplasm, was an intracellular enzyme. The metabolites of DEHP degradation by P. fluorescens FS1, which monoester, phthalic acid, benzonic acid, phenol, were extracted using dichloromethane at different time intervals and identified by the GC-MS. The tentative pathway proposed for degradation of DEHP by P. fluor- escens FS1 under aerobic condition is monoester in the beginning, further enzymatic degradation of the monoester produces phthalic acid, benzonic acid, phenol and finally CO2 and H2O.

An assessment of the toxicity of phthalate esters to freshwater benthos. 2. Sediment exposures

Seven phthalate esters were evaluated for their 10-d toxicity to the freshwater invertebrates Hyalella azteca and Chironomus tentans in sediment. The esters were diethyl phthalate (DEP), di-n-butyl phthalate (DBP), di-n-hexyl phthalate (DHP), di-(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and a commercial mixture of C7, C9, and C11 isophthalate esters (711P). All seven esters were tested in a sediment containing 4.80% total organic carbon (TOC), and DBP alone was tested in two additional sediments with 2.45 and 14.1% TOC. Sediment spiking concentrations for DEP and DBP were based on LC50 (lethal concentration for 50% of the population) values from water-only toxicity tests, sediment organic carbon concentration, and equilibrium partitioning (EqP) theory. The five higher molecular weight phthalate esters (DHP, DEHP, DINP, DIDP, 711P), two of which were tested and found to be nontoxic in water-only tests (i.e., DHP and DEHP), were tested at single concentrations between 2,100 and 3,200 mg/kg dry weight. Preliminary spiking studies were performed to assess phthalate ester stability under test conditions. The five higher molecular weight phthalate esters in sediment had no effect on survival or growth of either C. tentans or H. azteca, consistent with predictions based on water-only tests and EqP theory. The 10-d LC50 values for DBP and H. azteca were >17,400, >29,500, and >71,900 mg/kg dry weight for the low, medium, and high TOC sediments, respectively. These values are more than 30x greater than predicted by EqP theory and may reflect the fact that H. azteca is an epibenthic species and not an obligative burrower. The 10-d LC50 values for DBP and C. tentans were 826, 1,664, and 4.730 mg/kg dry weight for the low, medium, and high TOC sediments, respectively. These values are within a factor of two of the values predicted by EqP theory. Pore-water 10-d LC50 values for DBP (dissolved fraction) and C. tentans in the three sediments were 0.65, 0.89, and 0.66 of the water-only LC50 value of 2.64 mg/L, thereby agreeing with EqP theory predictions to within a factor of 1.5. The LC50 value for DEP and C. tentans was >3,100 mg/kg dry weight, which is approximately 10x that predicted by EqP theory. It is postulated that test chemical loss and reduced organism exposure to pore water may have accounted for the observed discrepancies with EqP calculations for DEP

An assessment of the toxicity of phthalate esters to freshwater benthos. 1. Aqueous exposures

Tests were performed with the freshwater invertebrates Hyalella azteca, Chironomus tentans, and Lumbriculus variegatus to determine the acute toxicity of six phthalate esters, including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP), di-n-hexyl phthalate (DHP), and di-2-ethylhexyl phthalate (DEHP). It was possible to derive 10-d LC50 (lethal concentration for 50% of the population) values only for the four lower molecular weight esters (DMP, DEP, DBP, and BBP), for which toxicity increased with increasing octanol-water partition coefficient (Kow) and decreasing water solubility. The LC50 values for DMP, DEP, DBP, and BBP were 28.1, 4.21, 0.63, and 0.46 mg/L for H. azteca; 68.2, 31.0, 2.64, and > 1.76 mg/L for C. tentans; and 246, 102, 2.48, and 1.23 mg/L for L. variegatus, respectively. No significant survival reductions were observed when the three species were exposed to either DHP or DEHP at concentrations approximating their water solubilities.

The environmental fate of phthalate esters: A literature review

A comprehensive and critical review was performed on the environmental fate of eighteen commercial phthalate esters with alkyl chains ranging from 1 to 13 carbons. A synthesis of the extensive literature data on physicochemical properties, partitioning behavior, abiotic and biotic transformations and bioaccumulation processes of these chemicals is presented. This chemical class exhibits an eight order of magnitude increase in octanol-water partition coefficients (Kow) and a four order of magnitude decrease in vapor pressure (VP) as alkyl chain length increases from 1 to 13 carbons. A critical review of water solubility measurements for higher molecular weight phthalate esters (i.e. alkyl chains ≥ 6 carbons) reveals that most published values exceed true water solubilities due to experimental difficulties associated with solubility determinations for these hydrophobic organic liquids. Laboratory and field studies show that partitioning to suspended solids, soils, sediments and aerosols increase as Kow increases and VP decreases. Photodegradation via free radical attack is expected to be the dominant degradation pathway in the atmosphere with predicted half-lives of ca. 1 day for most of the phthalate esters investigated. Numerous studies indicate that phthalate esters are degraded by a wide range of bacteria and actinomycetes under both aerobic and anaerobic conditions. Standardized aerobic biodegradation tests with sewage sludge inocula show that phthalate esters undergo ≥ 50% ultimate degradation within 28 days. Biodegradation is expected to be the dominant loss mechanism in surface waters, soils and sediments. Primary degradation half-lives in surface and marine waters range from <1 day to 2 weeks and in soils from <1 week to several months. Longer half-lives may occur in anaerobic, oligotrophic, or cold environments. Numerous experiments have shown that the bioaccumulation of phthalate esters in the aquatic and terrestrial foodchein is limited by biotransformation, which increases with increasing trophic level. Consequently, models that ignore biotransformation grossly exaggerate bioaccumulation potential of higher molecular weight phthalate esters. This review provides the logical first step in elucidating multimedia exposure to phthalate esters.

Aquatic toxicity of eighteen phthalate esters

AbstractThe extensive database of acute and chronic aquatic toxicity data for 18 phthalate esters was reviewed and summarized for freshwater and saltwater aquatic microorganisms, algae, invertebrates, and fish. Phthalate esters have been tested with six species of microorganisms, including bacteria and protozoans. Fifteen algal species have been tested, including green and bluegreen algae in both freshwater and saltwater. Nineteen freshwater and saltwater invertebrate species inhabiting surface waters and sediments and 21 freshwater and saltwater fish inhabiting cold and warm water bodies have been tested. The results of most studies indicate that acute and chronic toxicity to microorganisms, algae, aquatic invertebrates, and fish are limited to the lower molecular weight phthalate esters (i.e., dimethyl‐, diethyl‐, diallyl‐, dipropyl‐, dibutyl‐, diisobutyl‐, and butylbenzylphthalate). In contrast, higher molecular weight phthalate esters are not acutely or chronically toxic to aquatic organisms. Although conflicting data on chronic effects for high molecular weight phthalate esters have been reported for daphnids, these inconsistencies are attributed to physical effects imposed on daphnids when exposed to test concentrations in excess of true water solubilities. Altogether, nearly 400 test results covering more than 60 species of microorganisms, algae, invertebrates, and fish are reported for both freshwater and saltwater aquatic species. While most investigators used several common species and standard protocols to assay conventional endpoints, many nontraditional species and toxicological endpoints were also used. This has created a toxicological database of both sufficient depth to compare many similar tests and sufficient breadth to encompass virtually all important types of aquatic habitats and classes of aquatic species.