Bioaccumulation and metabolism of phthalate esters by oysters, brown shrimp, and sheepshead minnows

Widespread phthalate esters and monoesters in the aquatic environment: Distribution, bioconcentration, and ecological risks

Field research on phthalate monoesters (MPEs) and their relationships with phthalate esters (PAEs) is limited, especially in wild fishes. Here, PAEs and MPEs were measured in surface water, sediment, and wild fish collected from a representative river basin with high economic development. Several metabolites of emerging plasticizers, such as mono(3,5,5-trimethyl-1-hexyl) phthalate and mono(6-oxo-2-propylheptyl) phthalate, have already existed in fish with high detection frequencies (95 % and 100 %). Monobutyl phthalate and mono(2-ethylhexyl) phthalate were the predominant MPEs in fish and natural environment (surface water and sediment), while bis(2-ethylhexyl) phthalate was the most abundant PAEs in all matrices. The total concentrations (median) of 9 PAEs and 16 MPEs were 5980 and 266 ng/L in water, 231 and 10.6 ng/g (dw) in sediment, and 209 and 32.5 ng/g (ww) in fish, respectively. The occurrence of MPEs was highly related to their parent PAEs, with similar spatial distribution characteristics in the aquatic environments. Moreover, municipal wastewater discharge was recognized as the main source of MPEs in the research area. Fish species can accumulate targeted chemicals, and it seems more MPEs were from the PAE degradation in fish other than the direct uptake of MPEs in water. Parent PAEs showed higher ecological risk than their corresponding metabolites.

Antioxidant defenses and metabolic responses of Mytilus coruscus exposed to various concentrations of PAEs (phthalate esters)

Phthalate esters (PAEs), as a major plasticizer with multi-biotoxicity, are frequently detected in marine environments, and potentially affecting the survival of aquatic organisms. In the study, three typical PAEs (dimethyl phthalate [DMP], dibutyl phthalate [DBP] and di(2-ethylhexyl) phthalate [DEHP]) were selected to investigate the accumulation patterns and ecotoxicological effects on Mytilus coruscus (M. coruscus). In M. coruscus, the accumulation was DEHP>DBP>DMP, and the bioaccumulation in tissues was digestive glands>gills>gonads>muscles. Meanwhile, the activities of superoxide dismutase (SOD) and catalase (CAT) showed an activation-decrease-activation trend of stress, with more pronounced concentration effects. Glutathione reductase (GSH) activity was significantly increased, and its expression was more sensitive to be induced at an early stage. The metabolic profiles of the gonads, digestive glands and muscle tissues were significantly altered, and DEHP had a greater effect on the metabolic profiles of M. coruscus, with the strongest interference. PAEs stress for 7 d significantly altered the volatile components of M. coruscus, with potential implications for their nutritional value. This study provides a biochemical, metabolomic, and nutritional analysis of DMP, DBP, and DEHP toxic effects on M. coruscus from a multidimensional perspective, which provides support for ecotoxicological studies of PAEs on marine organisms. ENVIRONMENTAL IMPLICATION: Phthalate esters (PAEs), synthetic compounds from phthalic acid, are widespread in the environment, household products, aquatic plants, animals, and crops, posing a significant threat to human health. However, the majority of toxicological studies examining the effects of PAEs on aquatic organisms primarily focus on non-economic model organisms like algae and zebrafish. Relatively fewer studies have been conducted on marine organisms, particularly economically important shellfish. So, this study is innovative and necessary. This study provides a biochemical, metabolomic, and nutritional analysis of DMP, DBP, and DEHP toxic effects on mussels, and supports the ecotoxicology of PAEs on marine organisms.

Phthalate diester occurrence in marine feed and food (Mediterranean Sea)

Organic contaminants such as diesters of phthalic acid (PAEs) can be conveyed by microplastics in aquatic environment and constitute a relevant risk to marine organisms and humans that consume them. A method was developed for the identification and quantitative detection of 6 dimethyl phthalate (DMP), di-ethyl phthalate (DEP), di-n-butyl phthalate (DNBP), butyl benzyl phthalate (BBP), di-2-ethylesyl phthalate (DHEP), and di-n-octyl phthalate (DnOP). PAEs were then quantified in mesozooplankton, mollusk bivalves, and fish from the north-western Mediterranean Sea. Among all PAEs, DEHP was found in all zooplankton samples, in 30% of fish samples, and in 10% of bivalve samples. DBP was instead recovered in only 4% of samples (plankton and fish).

Phthalate levels in common sea anemone Actinia equina and Anemonia viridis: A proxy of short-term microplastic interaction?

Phthalates are widely employed plasticizers blended to plastic polymers that, during plastic aging and weathering are prone to leach in the surrounding environment. Thus, phthalates were proposed to indirectly evaluate MPs contamination in marine environments, with still uncertain and scarce data, particularly for wildlife. This study investigates simultaneously microplastics (MPs) and phthalates (PAEs) occurrence in wild Actinia equina and Anemonia viridis, two common and edible sea anemone species. Both species had a 100 % frequency of MPs occurrence, with similar average concentrations. PAEs were detected in 70 % of samples, with concentrations up to 150 ng/g in A. equina and 144.3 ng/g for A. viridis. MPs and PAEs present in sea anemone tissues appear to reflect seawater plastic contamination conditions in the study area. Given the rapid biodegradation of PAEs, occurrence and concentrations of both these additives and their metabolites could be useful tracers of short-term plastic debris-biota interactions.

Addressing the challenges of combined sewer overflows

Europe's ageing wastewater system often combines domestic sewage with surface runoff and industrial wastewaters. To reduce the associated risk of overloading wastewater treatment works during storms, and to prevent wastewater backing-up into properties, Combined Sewer Overflows (CSOs) are designed into wastewater networks to release excess discharge into rivers or coastal waters without treatment. In view of growing regulatory scrutiny and increasing public concern about their excessive discharge frequencies and potential impacts on environments and people, there is a need to better understand these impacts to allow prioritisation of cost-effective solutions.We review: i) the chemical, physical and biological composition of CSOs discharges; ii) spatio-temporal variations in the quantity, quality and load of overflows spilling into receiving waters; iii) the potential impacts on people, ecosystems and economies. Despite investigations illustrating the discharge frequency of CSOs, data on spill composition and loading of pollutants are too few to reach representative conclusions, particularly for emerging contaminants. Studies appraising impacts are also scarce, especially in contexts where there are multiple stressors affecting receiving waters. Given the costs of addressing CSOs problems, but also the likely long-term gains (e.g. economic stimulation as well as improvements to biodiversity, ecosystem services, public health and wellbeing), we highlight here the need to bolster these evidence gaps. We also advocate no-regrets options to alleviate CSO problems taking into consideration economic costs, carbon neutrality, ecosystem benefit and community well-being. Besides pragmatic, risk-based investment by utilities and local authorities to modernise wastewater systems, these include i) more systemic thinking, linking policy makers, consumers, utilities and regulators, to shift from local CSO issues to integrated catchment solutions with the aim of reducing contributions to wastewater from surface drainage and water consumption; ii) broader societal responsibilities for CSOs, for example through improved regulation, behavioural changes in water consumption and disposal of waste into wastewater networks, and iii) greater cost-sharing of wastewater use.

Phthalate plasticizer decreases the prion-like protein doppel essential for structural integrity and function of spermatozoa

Di-n-butyl phthalate (DBP), a well-known endocrine disruptor, causes male reproductive dysfunction. To understand the underlying mechanisms, we performed histological, endocrinological, and biochemical analyses and assessed the expression of genes involved in spermatogenesis and sperm function according to OECD test guideline 407. Following 28 days of administration of the lowest observed adverse effect level dose of DBP to mice, no significant changes in body weight, testis and epididymis weights and histology, serum testosterone level, or testicular daily sperm production were found. Nonetheless, the motility of the epididymal sperm of the DBP group was significantly decreased together with an increase in the incidence of bent tails and abnormal heads. In the testes of the DBP group, lipid peroxidation (LPO) level was significantly increased and testicular Bcl-2 mRNA level was significantly decreased together with an increase in the Bax/Bcl-2 mRNA ratio. In the testes of the DBP group, levels of Prnd mRNA and protein and Pou4f1 mRNA, an activator of the Prnd promotor, were significantly decreased. Of note, prion-like protein doppel (PRND) was significantly decreased together with decreased PRND immunoreactivity in the head, midpiece, and tail of sperm. In the testes of the DBP group, levels of Sox9, Sgp1, and Sgp2 mRNA, which are functional Sertoli cell markers, were significantly decreased. Level of Amh mRNA, a Sertoli cell immaturity marker, was significantly increased together with that of Inha mRNA, suggesting deregulation of the brain-gonadal axis. Together, our findings suggest that DBP at present dosage may potentiate LPO generation and Sertoli cell immaturity via downregulation of Sox9 and disruption of the Pou4f1-Prnd gene network in post-meiotic germ cells without visible changes in spermatogenesis or testosterone level. This may result in structural and functional abnormalities in spermatozoa. Additionally, our findings suggest that assessment of the male reproductive toxicity of phthalate ester plasticizers based on conventional OECD test guidelines should be reconsidered.

A novel report on phthalates levels in Biscayne Bay surface waters and drinking water from South Florida

In this research, we have developed and validated a modified version of the U.S.EPA method 506 using a liquid-liquid extraction method followed by gas-chromatography mass spectrometry analysis to assess the occurrence and spatial and seasonal variation of six phthalates (di(2-ethylhexyl) phthalate-DEHP, dibutyl phthalate-DBP, butyl benzyl phthalate-BBP, diethyl phthalate-DEP, dimethyl phthalate-DMP, and di-n-octyl phthalate-DOP) in surface and tap waters from South Florida, collected during the wet and dry seasons. The most frequently detected phthalate was DEHP, with concentrations up to 1.56 μg/L in surface water. Higher DEHP concentrations were observed in tap water during the wet season, which aligns with the higher temperature during the summer months facilitating leaching from plastic materials. Preliminary ecological and human health risk assessments suggested low hazard risk based on concentrations observed in tap and surface waters, respectively. PAEs could however still constitute a great concern to sensitive marine species, including early stages organisms and coral reefs.

"Oxidative stress induced by phthalates in mammals: State of the art and potential biomarkers"

BACKGROUND

Phthalates, plasticizers that are widely used in consumer products including toys, cosmetics, and food containers, have negative effects in liver, kidney, brain, lung and reproductive system of humans and other mammals.

OBJECTIVES

To summarize, describe and discuss the available information on the effects of phthalate exposure in mammals, with emphasis on oxidative stress, and to suggest potential biomarkers of the health risks associated with phthalate exposure.

METHODS

An assessment of scientific journals was performed using the PRISMA model for systematic reviews. Manuscripts reporting effects of phthalate exposure on mammalian health published in the last decade were selected according to originality, content, and association to health hazards.

RESULTS AND DISCUSSION

We identified 25 peer-reviewed articles published between January 1st, 2010 and June 1st, 2021 that fit the aims and selection criteria. Phthalates induce oxidative stress and cell degenerative processes by increasing intracellular reactive species. Antioxidant cytoprotective systems decrease with time of exposure; conversely, oxidative damage markers, including thiobarbituric acid-reactive substances (TBARS), 8-hydroxy-2'-desoxyguanosine (8-OHdG) and malondialdehyde (MDA), increase. Phthalates were associated with endocrine system disfunction, metabolic disorders, infertility, nonviable pregnancy, cell degeneration, growth impairment, tumor development, and cognitive disorders. Phthalates can also aggravate health conditions such as asthma, hepatitis, diabetes, allergies, chronic liver and kidney diseases. Among humans, the more vulnerable subjects to phthalate exposure effects were children and individuals with a prior health condition.

CONCLUSION

Chronic exposure to phthalates induces oxidative stress in mammals with concomitant adverse effects in reproductive, respiratory, endocrine, circulatory, and central nervous systems in both in vitro and in vivo trials. Oxidative damage markers and phthalate metabolites levels were the most common biomarkers of phthalate exposure effects. Studies in free-ranging and wild mammals are nil. Further studies on the pathways that lead to metabolic disruption are needed to identify potential treatments against phthalate-induced detrimental effects.

Di-butyl phthalate (DBP) induces defects during embryonic eye development in zebrafish

Di-butyl phthalate (DBP) is a phthalate ester (PAEs) added during the manufacturing of plastics to make them stronger, yet more pliable. DBP is noncovalently bound to plastics resulting in leaching into the environment. Concerning concentrations of DBP have been noted in surface and groundwater, aquatic ecosystems, soil and atmospheric environments globally. Global production of phthalates and thus concomitant exposure has increased over the years making studies on the ecological and environmental safety needed. Most of the literature on DBP focuses on the endocrine disrupting properties of phthalate esters, but the developmental toxicity of DBP is an understudied area. Here, we treat gastrula staged zebrafish embryos with environmentally relevant concentrations of DBP (2.5 µM). We find defects in eye development at 96 h post fertilization including a decrease in the size of the lens and retina in DBP-treated embryos. Defects in eye vascularization as well as loss of the optic nerve and optic tectum were also noted. Here we conclude that exposure to environmentally relevant doses of DBP during early embryonic development is toxic to eye development.

A model for phthalic acid esters' biodegradability and biotoxicity multi-effect pharmacophore and its application in molecular modification

The objective of this study was to investigate 13 phthalic acid esters (PAEs) with medium or long straight-alkyl-chain, branching or unsaturated side chains, because their structural characteristics make them difficult to biodegrade or highly toxic. A biodegradability and biotoxicity multi-effect pharmacophore model was built using comprehensive evaluation method. The results suggested that introducing hydrophobic groups to the side chains of the PAEs could improve the molecules' biodegradability and biotoxicity effects simultaneously. Thus, 40 target PAE (HEHP, DNOP, DUP) derivatives were designed. Two environmentally friendly PAE derivatives (HEHP-Anthryl and HEHP-Naphthyl) were screened via the test of environmental friendliness and functionality. In addition, the biodegradation and biotoxicity of derivatives were found to have improved as a result of the change in van der Waals forces between molecules and their corresponding proteins. Moreover, the environmental safety of the screened PAE derivatives was confirmed by predicting the toxicity of their intermediates and calculating the energy barrier values for biodegradation and metabolic pathways. This study could provide theoretical guidance for the practical development of environmentally friendly plasticizer.

Plastic-derived contaminants in Aleutian Archipelago seabirds with varied foraging strategies

Phthalates, plastic-derived contaminants, are of increasing global concern. This study quantified phthalates in seabirds collected across >1700 km of the Aleutian Islands, Alaska, and contributes to a body of knowledge on plastic contaminants in marine wildlife. We measured six phthalate congeners in seabirds representing ten species and four feeding guilds. Phthalates were detected in 100% of specimens (n = 115), but varied among individuals (3.64-539.64 ng/g). DEHP and DBP occurred at an order of magnitude higher than other congeners. Total phthalates did not vary geographically, but differed among feeding guilds, with significantly higher concentrations in diving plankton-feeders compared to others. Plastic particles were detected in 36.5% of randomly subsampled seabird stomachs (n = 74), suggesting plastic ingestion as a potential route of phthalate exposure. Our findings suggest feeding behavior could influence exposure risk for seabirds and lend further evidence to the ubiquity of plastic pollutants in marine ecosystems.

Derivation of aquatic life criteria for four phthalate esters and their ecological risk assessment in Liao River

As a critical family of endocrine disruptors, phthalate esters (PAEs) attracted considerable attentions due to increasingly detected worldwide. Aquatic life criteria (ALC) for PAEs are crucial for their accurate ecological risk assessment (ERA) and have seldom been derived before. Given this concern, the purpose of the present study is to optimize the ALCs of four priority PAEs to estimate their ecological risks in Liao River. Reproductive endpoint was found to be more sensitive than other endpoints. Thus, reproduction related toxicity data were screened to derive ALCs applying species sensitivity distribution (SSD) method. ALCs of DEHP, DBP, BBP and DEP were calculated to be 0.04, 0.62, 4.71 and 41.9 μg L^-1, which indicated decreased toxicity in sequence. Then, the derived ALCs of the four PAEs were applied to estimate their ecological risks in Liao River. A total of 27 sampling sites were selected to detect and analyze the exposure concentrations of PAEs. ERA using the hazard quotient (HQ) method was conducted. The results demonstrated that DEHP exhibited higher risks at 92.6% of sampling sites, and risks posed by DBP were moderate at 63.0% sampling sites. However, risks posed by BBP were low at 70.4% of sampling sites, and there were no risks posed by DEP at 96.3% of sampling sites. The results of probabilistic ecological risk assessment (PERA) indicated that probabilities of exceeding effects thresholds on 5% of species were 60.41%, 0%, 0.12%, 14.28% for DEHP, DEP, BBP and DBP, respectively. The work provides useful information to protect aquatic species in Liao River.

Effects of DEHP on post-embryonic development, nuclear receptor expression, metabolite and ecdysteroid concentrations of the moth Spodoptera littoralis

Di (2-ethylhexyl) phthalate (DEHP) is recognized in vertebrates as an Endocrine Disrupting Chemical (EDC). DEHP can alter steroid hormones production, development, reproduction and behavior in vertebrates. Only few studies investigated DEHP effects on insects. However, some recent studies on aquatic insects showed that DEHP could also act as an EDC by interfering with the signaling pathways of ecdysteroids, the main hormones involved in the control of insect post-embryonic development and physiology. The aim of the study was to investigate (1) the fate of DEHP within a terrestrial insect species by exposing larvae to food containing a wide range of DEHP concentrations and (2) the effects of this chemical on their post-embryonic development and metamorphosis, by using a multi-level approach. DEHP was shown to be present both in larvae and resulting stages, with higher concentrations in chrysalises and adults than in larvae. DEHP concentrations also decreased at the end of the last larval instar, suggesting the metabolic transformation or excretion of this chemical during this time. Only the two highest DEHP doses induced higher insect mortality, whereas low and intermediate concentrations increased larval food consumption without affecting body weight. Metabolic profiles showed that in control insects, the last three days before metamorphosis correspond to a metabolic transition, but with time-dependent changes in treated insects. Interestingly, DEHP treatments also alter both hemolymphatic ecdysteroid titers and expression levels of ecdysteroid response genes. These results confirm that DEHP can alter insect post-embryonic development and metamorphosis, by interfering with ecdysteroid pathways.

Raw and biologically treated paper mill wastewater effluents and the recipient surface waters: Cytotoxic and genotoxic activity and the presence of endocrine disrupting compounds

Paper mill effluents are complex mixtures containing different toxic compounds including endocrine-disrupting (EDCs) and genotoxic compounds. In the present study non-concentrated raw and biologically treated wastewaters from two paper mill plants with different paper production technologies i) Paper mill A uses virgin fibres, and ii) Paper mill B uses recycled fibres for paper production and the corresponding receiving surface waters, were assessed for their cytotoxic/genotoxic activity with SOS/umuC, Ames MPF 98/100 Aqua, and comet assay with human hepatoma HepG2 cells. In addition the levels of seven selected EDCs were quantified in wastewater samples and receiving surface waters. All investigated EDCs were confirmed in raw and biologically treated effluents from both paper mills with concentrations being markedly higher in Paper mill B effluents. In the receiving surface waters three of the studied EDCs were determined downstream of both paper mills effluent discharge. The wastewater samples and the recipient surface water samples from Paper mill A were not mutagenic for bacteria and did not induce DNA damage in HepG2 cells. On the contrary, half of the raw wastewater samples from Paper mill B were mutagenic whereas biologically treated wastewater and the recipient surface water samples were negative. In HepG2 cells most of the raw and biologically treated wastewater samples from Paper mill B as well as surface water samples collected downstream of Paper mill B effluent discharge induced DNA damage. The results confirmed that genotoxic contaminants were present only in wastewaters from Paper mill B that uses recycled fibres for paper production, and that the combined aerobic and anaerobic wastewater treatment procedure efficiently reduced contaminants that are bacterial mutagens, but not those that induce DNA damage in HepG2 cells. This study highlights that in addition to chemical analyses bioassays are needed for a comprehensive toxicological evaluation of complex wastewater samples.

Accumulation patterns of lipophilic organic contaminants in surface sediments and in economic important mussel and fish species from Jakarta Bay, Indonesia

Non-target screening analyses were conducted in order to identify a wide range of organic contaminants in sediment and animal tissue samples from Jakarta Bay. High concentrations of di-iso-propylnaphthalenes (DIPNs), linear alkylbenzenes (LABs) and polycyclic aromatic hydrocarbons (PAHs) were detected in all samples, whereas phenylmethoxynaphthalene (PMN), DDT and DDT metabolites (DDX) were detected at lower concentrations. In order to evaluate the uptake and accumulation by economic important mussel (Perna viridis) and fish species, contaminant patterns of DIPNs, LABs and PAHs in different compartments were compared. Different patterns of these contaminant groups were found in sediment and animal tissue samples, suggesting compound-specific accumulation and metabolism processes. Significantly higher concentrations of these three contaminant groups in mussel tissue as compared to fish tissue from Jakarta Bay were found. Because P. viridis is an important aquaculture species in Asia, this result is relevant for food safety.

Influence of Lipophilicity on the Toxicity of Bisphenol A and Phthalates to Aquatic Organisms

Bisphenol A (BPA) and phthalates are among the most popular plasticizers used today and have been reported ubiquitously in surface water, ground water, and sediment. For aquatic organisms, BPA was the most toxic (96 h LC50s) to aquatic invertebrates (0.96-2.70 mg/L) and less toxic to fish (6.8-17.9 mg/L). The toxicity of BPA to amphibians differed among developmental stages, with embryos having an LC50 of 4.6-6.8 mg/L and juveniles 0.50-1.4 mg/L. The toxicity of phthalates is affected by aromatic ring substitution, alkyl chain length, and metabolism. The toxicity (96 h LC50s) of phthalates was similar to aquatic invertebrates (0.46-377 mg/L) and fish (0.48-121 mg/L). In general, the toxicity of phthalates appears to be highest around a log KOW of 6, which corresponds to the highest potential for bioconcentration and bioaccumulation. In conclusion, the lipophilicity of BPA and phthalates influence their toxicity to aquatic species.

Occurrence, fate, behavior and ecotoxicological state of phthalates in different environmental matrices

Because of their large and widespread application, phthalates or phthalic acid esters (PAEs) are ubiquitous in all the environmental compartements. They have been widely detected throughout the worldwide environment. Indoor air where people spend 65-90% of their time is also highly contaminated by various PAEs released from plastics, consumer products as well as ambient suspended particulate matter. Because of their widespread application, PAEs are the most common chemicals that humans are in contact with daily. Based on various exposure mechanisms, including the ingestion of food, drinking water, dust/soil, air inhalation and dermal exposure the daily intake of PAEs may reach values as high as 70 μg/kg/day. PAEs are involved in endocrine disrupting effects, namely, upon reproductive physiology in different species of fish and mammals. They also present a variety of additional toxic effects for many other species including terrestrial and aquatic fauna and flora. Therefore, their presence in the environment has attracted considerable attention due to their potential impacts on ecosystem functioning and on public health. This paper is a synthesis of the extensive literature data on behavior, transport, fate and ecotoxicological state of PAEs in environmental matrices: air, water, sediment, sludge, wastewater, soil, and biota. First, the origins and physicochemical properties of PAEs that control the behavior, transport and fate in the environment are reviewed. Second, the compilation of data on transport and fate, adverse environmental and human health effects, legislation, restrictions, and ecotoxicological state of the environment based on PAEs is presented.

Dioxin and phthalate uptake and assimilation by the green mussel Perna viridis

In this study, the aqueous uptake and dietary assimilation (trophic transfer) of two endocrine disrupting compounds (dioxin and phathalic acid) in the green mussel Perna viridis were quantified. During short-term exposure period, dioxin rapidly sorbed onto phytoplankton and its accumulation was much higher than that of phthalate. The uptake of these two compounds by the mussels increased with increasing temperature and salinity (for dioxin only). The dietary assimilation of the two contaminants was rather modest (10-64% for dioxin and 20-47% for phthalate), and was greatly dependent on the food species and concentration. Interestingly, dietary assimilation increased with increasing diatom food concentration. Gut passage time was partially responsible for the variable dietary assimilation. Given the high dissolved uptake rate and the modest dietary assimilation, aqueous exposure was predicted to be the dominant bioaccumulation source for both dioxin and phthalate in the green mussels under most conditions.

Designing green plasticizers: influence of molecular geometry on biodegradation and plasticization properties

The plasticizer di (2-ethylhexyl) phthalate (DEHP) and its metabolites are considered ubiquitous contaminants, which have a range of implications on the environment and human health. This work considered several alternative compounds with structural features similar to DEHP. This added to the understanding of why DEHP is so poorly biodegraded once it enters the environment. These alternative compounds were based on 2-ethylhexyl diesters of maleic acid (cis-isomer), fumaric acid (trans-isomer) and succinic acid (saturated analogue). The rates of biodegradation by the common soil bacterium Rhodococcus rhodocrous were shown to be dependent on the structure of the central unit derived from the diacid used to make the ester. The diacid components of DEHP and the maleate both had a cis orientation and they were the two that were slow to biodegrade. Plasticizing properties were also compared and, because the ester of the saturated succinic acid was degraded quickly and also had good plasticizing properties, it was concluded that the succinic esters of straight chain alcohols would make the best green plasticizers. The maleate ester had excellent plasticizing properties but this is mitigated by a significant resistance to biodegradation.

Bioconcentration, bioaccumulation, and metabolism of pesticides in aquatic organisms

The ecotoxicological assessment of pesticide effects in the aquatic environment should normally be based on a deep knowledge of not only the concentration of pesticides and metabolites found but also on the influence of key abiotic and biotic processes that effect rates of dissipation. Although the bioconcentration and bioaccumulation potentials of pesticides in aquatic organisms are conveniently estimated from their hydrophobicity (represented by log K(ow), it is still indispensable to factor in the effects of key abiotic and biotic processes on such pesticides to gain a more precise understanding of how they may have in the natural environment. Relying only on pesticide hydrophobicity may produce an erroneous environmental impact assessment. Several factors affect rates of pesticide dissipation and accumulation in the aquatic environment. Such factors include the amount and type of sediment present in the water and type of diet available to water-dwelling organisms. The particular physiological behavior profiles of aquatic organisms in water, such as capacity for uptake, metabolism, and elimination, are also compelling factors, as is the chemistry of the water. When evaluating pesticide uptake and bioconcentration processes, it is important to know the amount and nature of bottom sediments present and the propensity that the stuffed aquatic organisms have to absorb and process xenobiotics. Extremely hydrophobic pesticides such as the organochlorines and pyrethroids are susceptible to adsorb strongly to dissolved organic matter associated with bottom sediment. Such absorption reduces the bioavailable fraction of pesticide dissolved in the water column and reduces the probable ecotoxicological impact on aquatic organisms living the water. In contrast, sediment dweller may suffer from higher levels of direct exposure to a pesticide, unless it is rapidly degraded in sediment. Metabolism is important to bioconcentration and bioaccumulation processes, as is detoxification and bioactivation. Hydrophobic pesticides that are expected to be highly stored in tissues would not be bioconcentrated if susceptible to biotic transformation by aquatic organisms to more rapidly metabolized to hydrophilic entities are generally less toxic. By analogy, pesticides that are metabolized to similar entities by aquatic species surely are les ecotoxicologically significant. One feature of fish and other aquatic species that makes them more relevant as targets of environmental studies and of regulation is that they may not only become contaminated by pesticides or other chemicals, but that they constitute and important part of the human diet. In this chapter, we provide an overview of the enzymes that are capable of metabolizing or otherwise assisting in the removal of xenobiotics from aquatic species. Many studies have been performed on the enzymes that are responsible for metabolizing xenobiotics. In addition to the use of conventional biochemical methods, such studies on enzymes are increasingly being conducted using immunochemical methods and amino acid or gene sequences analysis. Such studies have been performed in algae, in some aquatic macrophytes, and in bivalva, but less information is available for other aquatic species such as crustacea, annelids, aquatic insecta, and other species. Although their catabolizing activity is often lower than in mammals, oxidases, especially cytochrome P450 enzymes, play a central role in transforming pesticides in aquatic organisms. Primary metabolites, formed from such initial enzymatic action, are further conjugated with natural components such as carbohydrates, and this aids removal form the organisms. The pesticides that are susceptible to abiotic hydrolysis are generally also biotically degraded by various esterases to from hydrophilic conjugates. Reductive transformation is the main metabolic pathway for organochlorine pesticides, but less information on reductive enzymology processes is available. The information on aquatic species, other than fish, that pertains to bioconcentration factors, metabolism, and elimination is rather limited in the literature. The kinds of basic information that is unavailable but is needed on important aquatic species includes biochemistry, physiology, position in food web, habitat, life cycle, etc. such information is very important to obtaining improved ecotoxicology risk assessments for many pesticides and other chemicals. More research attention on the behavior of pesticides in, and affect on many standard aquatic test species (e.g., daphnids, chironomids, oligochaetes and some bivalves) would particularly be welcome. In addition to improving ecotoxicology risk assessments on target species, such information would also assist in better delineating affects on species at higher trophic levels that are predaceous on the target species. There is also need for designing and employing more realistic approaches to measure bioconcentration and bioaccumulation, and ecotoxicology effects of pesticides in natural environment. The currently employed steady-state laboratory exposure studies are insufficient to deal with the complexity of parameters that control the contrasts to the abiotic processes of pesticide investigated under the strictly controlled conditions, each process is significantly affected in the natural environment not only by the site-specific chemistry of water and sediment but also by climate. From this viewpoint, ecotoxicological assessment should be conducted, together with the detailed analyses of abiotic processes, when higher-tier mesocosm studies are performed. Moreover, in-depth investigation is needed to better understand the relationship between pesticide residues in organisms and associated ecotoxicological endpoints. The usual exposure assessment is based on apparent (nominal) concentrations fo pesticides, and the residues of pesticides or their metabolites in the organisms are not considered in to the context of ecotoxicological endpoints. Therefore, more metabolic and tissue distribution information for terminal pesticide residues is needed for aquatic species both in laboratory settings and in higher-tier (microcosm, mesocosm) studies.

Distribution of phthalate esters in a marine aquatic food web: comparison to polychlorinated biphenyls

Dialkyl phthalate esters (DPEs) are widely used chemicals, with over 4 million tonnes being produced worldwide each year. On the basis of their octanol-water partition coefficients (Kow), which range from 10(1.61) for dimethyl phthalate to 10(9.46) for di-iso-decyl phthalate, certain phthalate esters have the potential to bioconcentrate and biomagnify in aquatic food webs. However, there are no reported field studies on the trophodynamics of phthalate ester in aquatic food webs. This study reports the distribution of 8 individual phthalate esters (i.e., dimethyl, diethyl, di-isobutyl, di-n-butyl, butylbenzyl, di(2-ethylhexyl), di-n-octyl, and di-n-nonyl) and 5 commercial isomeric mixtures (i.e., di-iso-hexyl (C6), di-iso-heptyl (C7), di-iso-octyl (C8), di-iso-nonyl (C9), and di-iso-decyl (C10)) in a marine aquatic food web. DPE concentrations were determined in 18 marine species, representing approximately 4 trophic levels. Co-analysis of DPEs and 6 PCB congeners (i.e., PCB-18, 99, 118, 180, 194, and 209) in all samples produced a direct comparison of the bioaccumulation behavior of PCBs and DPEs. Lipid equivalent concentrations of the PCBs increased with increasing trophic position and stable isotope ratios (delta15N). The Food-Web Magnification Factor (FWMF) of the PCB congeners ranged from 1.8 to 9.5. Lipid equivalent concentrations of low and intermediate molecular weight DPEs (i.e., C1-C7 DPEs: dimethyl, diethyl, di-iso-butyl, di-n-butyl, benzylbutyl, and C6 and C7 isomers) did not exhibit statistically significant trends with trophic position or stable nitrogen isotope ratios (delta15N) in the food web and FWMFs were not significantly different from 1. Lipid equivalent concentrations of the high-molecular-weight DPEs (i.e., C8-C10 DPEs: di(2-ethylhexyl), di-n-octyl, di-n-nonyl, C8, C9, and C10) declined significantly with increasing trophic position and stable isotope ratios (delta15N), producing FWMFs between 0.25 and 0.48. These results show that all DPEs tested did not biomagnify in the studied aquatic food web whereas PCBs did biomagnify.

Pollutant-specific and general lysosomal responses in digestive cells of mussels exposed to model organic chemicals

The present study was carried out to elucidate whether lysosomal size reduction in digestive cells of mussels Mytilus galloprovincialis constitutes a selective response against a particular group of organic chemical compounds, in contrast to the lysosomal enlargement characteristic of general stress response. Mussels were treated with di(2-ethylhexyl) phthalate (DEHP), benzo(a)pyrene (B[a]P), and the water accommodated fraction (WAF) of a lubricant oil, which were daily applied by either injection through the adductor muscle for 7 days or water-exposure for 21 days. Control mussels were either kept untreated in clean sea water, or treated with acetone (injection and water-exposure), vehicle used for DEHP and B[a]P. A third set of controls consisted of mussels with pierced shell kept in clean seawater. Digestive glands were excised at various treatment days and beta-glucuronidase activity was demonstrated in 8-microm cryotome sections. Lysosomal volume, surface and numerical densities, and surface-to-volume ratio were quantified by image analysis. Other sections were stained with oil red 0 to demonstrate neutral lipids and changes in lipid levels were quantified by image analysis. Neutral lipid accumulation in digestive cells was used as a complementary indication of exposure to organic chemicals. It resulted to be a very prompt and all-or-nothing response, which reached a plateau before 1 day of treatment with WAF, DEHP and B[a]P after both injection and water-exposure. DEHP-treatment induced a general stress response characterised by lysosomal enlargement in digestive cells, which was already induced after 1 day. Treatment with either WAF or B[a]P elicited a comparable biphasic response. A transient lysosomal enlargement, shorter with WAF than with B[a]P treatment, was evidenced after both injection and water-exposure. Further, under water-exposure conditions, WAF reduced the endo-lysosomal system in size more markedly than B[a]P. Such lysosomal size reduction constitutes a transient response after exposure to diverse organic xenobiotics (acetone, WAF and B[a]P). In addition, this lysosomal size reduction might be followed by a further lysosomal enlargement, which later might yet again give rise to an apparent lysosomal size reduction under chronic exposure conditions. As a whole, the lysosomal response is intricate and cannot be simply interpreted in environmental pollution monitoring programmes. Nevertheless, it still constitutes a powerful and sensitive biomarker extremely useful as early-warning signal.

Effects and toxicity of phthalate esters to hemocytes of giant freshwater prawn, Macrobrachium rosenbergii

Phthalate esters (PAEs) have been considered as environmental pollutants and have been subject to control in the United States of America and Japan. The aim of this study was to investigate the effects and toxicity of eight PAEs to hemocytes and the defense functions of giant freshwater prawn (Macrobrachium rosenbergii), including hemocytic adhesion, pseudopodia formation, phenoloxidase (PO) activity, and superoxide anion (O(2)(-)) production, by means of in vitro exposure experiments. After hemocytes were treated separately with eight PAEs at concentrations of 100 microg/ml, the results showed that two PAEs (dipropyl phthalate, DPrP and diethyl phthalate, DEP) increased cells with pseudopodia formation, but decreased adhesive cells; reduction in the percentages of both pseudopodia formation and adhesive cells were detected in the dihexyl phthalate (DHP) and diphenyl phthalate (DPP) experiment groups; and di-(2-ethyl hexyl) phthalate (DEHP) decreased pseudopodia formation, but did not affect the adhesion. In addition, both PO activity and O(2)(-) production were decreased after hemocytes were treated with five PAEs (benzyl butyl phthalate (BBP), di-n-butyl phthalate (DBP), DEP, DHP and DPrP), respectively. At the same time, microscopy showed that both DPrP and DHP altered morphology of the cell nucleus and led to the presence of vacuoles in cytosol of hemocytes. Using the annexin assay, and after analysis of DNA fragmentation and transmission electron microscopy (TEM), it was found that hemocytes exposed to DHP and DPrP for more than 10 min would primarily die via apoptosis, the fatality correlates with increasing treatment time; and hemocytes treated with either BBP, dicyclohexyl phthalate (DCP), DEP or DPP would primarily die via necrosis. According to these results, we suggest that all eight PAEs examined could damage hemocytes and further influence the defense mechanism of prawns. This study reveals an important precaution for prawn cultivation.

Interactive effects of benzo(a)pyrene and cadmium and effects of di(2-ethylhexyl) phthalate on antioxidant and peroxisomal enzymes and peroxisomal volume density in the digestive gland of mussel Mytilus galloprovincialis Lmk

Exposure of marine animals to certain organic and metal pollutants is thought to enhance reactive oxygen species (ROS) production with concomitant alterations of antioxidant defence mechanisms. Some of these organic pollutants cause peroxisome proliferation, a process resulting also in possible enhanced production of ROS. The aim of this study was to investigate the effects of two organic xenobiotics, benzo(a)pyrene (B(a)P) and di(2-ethylhexyl)phthalate (DEHP), as well as the effects of cadmium (Cd), on antioxidant and peroxisomal enzymes and on peroxisomal volume density in the digestive gland of mussel, Mytilus galloprovincialis Lmk., experimentally exposed for 21 days. Special attention was paid to the interactive effects of organic and metal compounds by exposing one group of mussels to a mixture of B(a)P and Cd. Exposure of mussels to Cd caused a decrease in superoxide dismutase (SOD) activity, in Mn-SOD protein levels and in volume density of peroxisomes. B(a)P exposure significantly increased catalase and glutathione peroxidase (GPX) and inhibited Mn-SOD after 21 days of exposure. B(a)P also caused a slight increase in acyl-CoA oxidase (AOX) activity and peroxisomal volume density after 21 days of exposure. Cd tended to inhibit changes provoked by B(a)P, indicating that responses to organic xenobiotics can be modulated by concomitant exposure to metal contaminants. Exposure to DEHP increased catalase and AOX and inhibited SOD activity and Mn-SOD protein levels. In conclusion, peroxisome proliferation, measured as an increase of the peroxisomal enzymes catalase and AOX (up to 1.53-fold for AOX), is a specific response to organic contaminants such as B(a)P and DEHP, whereas Cd does not cause peroxisome proliferation. Thus, peroxisome proliferation may be a specific biomarker of organic pollutants in mussels. Both organic and metal pollutants inhibited SOD activity and protein levels (up to 0.21-fold for Mn-SOD protein levels), the latter offering potential as general marker of pollution.

Differential inhibition of xenobiotic-metabolizing carboxylesterases by organotins in marine fish

The hydrolytic metabolism of xenobiotics in the liver of two tropical marine fish, Siganus canaliculatus and Acanthopagrus latus, was found to be catalyzed by both microsomal and cytosolic carboxylesterases; the latter forms were more active than the former. Remarkably greater efficiency of S. canaliculatus for p-nitrophenylacetate hydrolysis was attributed to manyfold higher V(max) and lower K(m) values of hepatic microsomal and cytosolic carboxylesterases of S. canaliculatus as compared with those of A. latus. Comparative characterization of the in vitro responses of hepatic microsomal and cytosolic carboxylesterases to the organotin group of marine pollutants-tributyltin (TBT), triphenyltin (TPT), and dibutyltin (DBT), a relatively persistent metabolite of TBT-revealed species-, isozymic form-, and organotin structure-related differences in the hydrolytic detoxication. In general, carboxylesterases of S. canaliculatus exhibited severalfold greater susceptibility to organotin inhibition and DBT was the most potent inhibitor (IC(50) in micromolar range). Notably, the IC(50) of SnCl(2), a metal present in all the compounds studied, was higher than 2 mM. Cytosolic forms in both species were more sensitive to organotin inhibition than microsomal counterparts. In line with these differences the nature of inhibition of cytosolic and microsomal carboxylesterases by organotins was competitive and noncompetitive, respectively. These results suggest that organotins may aggravate the toxicity of other environmental contaminants in fish and other aquatic organisms. Moreover, highly sensitive cytosolic carboxylesterases of S. canaliculatus liver may serve as molecular biomarkers of organotin pollution.

Induction of peroxisomal oxidases in mussels: comparison of effects of lubricant oil and benzo(a)pyrene with two typical peroxisome proliferators on peroxisome structure and function in Mytilus galloprovincialis

Marine mussels are used as bioindicators of water pollution in marine and estuarine environments in the so-called "Mussel Watch" programs because of their capacity to accumulate numerous organic xenobiotics including aromatic hydrocarbons. In this study, we have analyzed the effects of two xenobiotics [benzo(a)pyrene and the water accommodated fraction of a lubricant oil] and two typical (rodent) peroxisome proliferators (clofibrate and dioctyl phthalate) on structure and function of peroxisomes in digestive glands of mussels Mytilus galloprovincialis, either following water exposure (for 1, 7, and 21 days) or after direct injection through the adductor muscle (for 1 and 7 days). The activities of catalase (CAT), acyl-CoA oxidase (AOX), and D-amino acid oxidase were determined in whole homogenates of digestive glands. In addition, stereological methods were applied on sections stained histochemically for demonstration of catalase activity in order to quantify the morphological changes of peroxisomes. The peroxisomal acyl-CoA oxidase and D-amino acid oxidase were increased in mussels injected for 7 days with benzo(a)pyrene, phthalate, and clofibrate and a similar trend was noted for benzo(a)pyrene and lubricant oil in water exposure experiments (21 days). The catalase activity was reduced or unchanged depending on the mode of exposure of animals. By stereology, significant increases of numerical and volume densities of peroxisomes were found in animals injected for 7 days with lubricant oil or clofibrate. These observations indicate that peroxisomal oxidases in mussels are induced at moderate rates in response to different xenobiotics and that their determination could provide a (sensitive) marker for detection of effects of some toxic pollutants, particularly the lubricant oils which in addition induce significant structural alterations of mussel peroxisomes.

The metabolism of di(2-ethylhexyl)phthalate in the earthworm Lumbricus terrestris

1. Earthworms can hydrolyze di-(2-ethylhexyl) phthalate (DEHP) to mono-2-ethylhexyl phthalate (MEHP) and phthalic acid (PA). 2. They apparently cannot produce the side-chain-oxidized derivatives of MEHP that constitute the major DEHP metabolites in higher animals. 3. With the assistance of intestinal bacterial Pseudomonas, the worm-derived PA is degraded through protocatechuic and beta-carboxymuconic acids to CO2. 4. There is an indication of a second pathway for degradation of PA leading through benzoic acid.

Toxicity of a phthalate ester in the diet of a penaied shrimp

The toxicity of di-2-ethylhexyl phthalate (DEHP), a ubiquitous environmental pollutant, was measured experimentally as a contaminant in shrimp aquaculture feeds. Diets containing 40 to 50,000 ppm DEHP were fed to Penaeus vannamei for 14 d at 4% body weight/d. DEHP concentrations in shrimp, diet, and water were measured by electron-capture gas chromatography. Whole-body residues in shrimp were 18 ppm at the highest dose, and bioconcentration factors were inversely proportional to dose. DEHP in water was less than or equal to 1.7 ppb for all dose levels. No increased mortality or histopathological alterations were observed at any dose. Absorption of DEHP by P. vannamei was measured in static 24- and 96-h bioassays. Diets enriched with [14C]DEHP to levels of 60, 600, and 6000 ppm were fed at 2% body weight/d. At all dose levels, 3.7% of total radioactivity was measured as body burden in shrimp and 40% as polar species in test water after 96 h. DEHP by oral administration was absorbed, metabolized, and excreted, and this process was linear with dose for the dose range studied.