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

Phthalates and organophosphorus insecticide residues in shrimp determined by liquid/gas chromatography-Tandem mass spectrometry and a health risk assessment

Shrimps are the most widely and increasingly cultured crustaceans in land-based ponds in Taiwan. However, few studies have investigated the phthalate contamination of and insecticide residues in shrimp. In this study, we applied a validated method to analyze the phthalate and 18 insecticides residues in shrimp. A total of 46 samples of whiteleg, grass, or giant river shrimp were collected from aquafarms and production areas in Taiwan. We detected 0.02-0.70 mg/kg of di-2-ethylhexyl phthalate (DEHP) in three shrimps; 0.02-0.03 mg/kg of chlorpyrifos in three shrimps, and 0.03 mg/kg of trichlorfon in one shrimp, indicating that 6.52% and 8.70% of the samples contained phthalate and insecticide residues, respectively. Furthermore, the assessed risk was negligible and indicated no immediate health risk associated with shrimp consumption. Continual monitoring of the residues in shrimps is critical for further assessment of possible effects on human health.

Characterisation of immune-related gene expression in clam (Venerupis philippinarum) under exposure to di(2-ethylhexyl) phthalate

Di(2-ethylhexyl) phthalate (DEHP) mediates the immune system mainly by triggering the production of reactive oxygen species (ROS) and nitric oxide (NO) in higher animals. In the present study, spatial variation in the expression of immune-related genes in clam (Venerupis philippinarum) under acute short-term DEHP treatment was assessed by qPCR. The expression of six genes including glutamine synthetase (GS), IkB (IK), transcription factor activator protein-1 (AP-1), cyclophilin A-1 (CypA-1), heat shock protein 90 (HSP90) and superoxide dismutase (SOD) was dose-dependent. A negative correlation between expression and DEHP treatment was observed for big defensin (BD), glutathione S-transferase (GST), and thioredoxin peroxidase (TP). Surprisingly, lysozyme (LYZ) exhibited two distinct expression patterns at two DEHP doses. Significant differences between the experimental and control groups were observed for all tested genes at the various time points. Overall, our results revealed that DEHP mediates immune responses in clams by various means, and certain genes are promising candidate for biomarkers in DEHP monitoring.

The toxic effect of phthalate esters on immune responses of giant freshwater prawn (Macrobrachium rosenbergii) via oral treatment

A previous in vitro study has indicated that four phthalate esters (PAEs) could damage hemocytes and decreases the cellular immunity of prawns [Sung, H.H., Kao, W.Y., Su, Y.J., 2003. Effects and toxicity of phthalate esters to hemocytes of giant freshwater prawn, Macrobranchium rosenbergii. Aquat. Toxicol. 64, 25-37]. The aim of this study was to investigate the in vivo effect of four PAEs, diethyl phthalate (DEP), dihexyl phthalate (DHP), dipropyl phthalate (DPrP) and diphenyl phthalate (DPP) on the defense system of the giant freshwater prawn, M. rosenbergii. PAE dissolved in corn oil was continuously fed to prawns for 8 days and five immune parameters (total hemocyte count, THC; ratio of granulocytes to hyalinocytes, G/H; intrahemocytic total phenoloxidase activity, PO(T); intracellular superoxide anion (O2-) production; transglutaminase (TGase) activity) were separately detected on days 1, 4 and 8. In addition, mortality was determined on days 4 and 8 after challenging the prawns with Lactobacillus garvieae. In comparison with untreated prawns, the results showed that DHP demonstrated the lowest toxicity in that it only influenced the PO activity and O2- production before 4 days after treatment and caused 6.6% mortality on day 8. DEP decreased G/H, PO(T) and TGase activity on day 1 and reduced THC, G/H and PO(T) and caused 16.6% mortality on day 4; however, on day 8, it increased O2- production and caused no mortality. In the DPrP-treated group, a reduction of all the immune reactions apart from TGase activity and 22.2% mortality were detected on day 4. As for the effect of DPP, results showed that it decreased all the immune parameters apart from THC on days 1 and 4, but caused no mortality on day 4; but on day 8, an increase of O2- production and 17.7% mortality were detected. These results indicated that the immune reactions of prawns were variable due to the different toxic effects of PAEs. In addition, it was found that, on day 8 after treatment, the three PAEs, DHP, DPrP and DPP increased O2- production and did not influence the other four reactions, but mortality was detected in these groups. These results suggest that other physiological responses may also be affected to increase the susceptibility of prawns to pathogens.

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.

Application of quantitative structure--activity relationships for assessing the aquatic toxicity of phthalate esters

Phthalate esters (PEs) are an important class of industrial chemicals for which an extensive aquatic toxicity database is available. The objectives of this study were to use these data to develop quantitative structure-activity relationships (QSARs) that describe aquatic toxicity for different freshwater and marine species, gain insights into toxicity mechanisms, and calculate PE water quality criteria using statistical extrapolation procedures. Results for low-molecular-weight PEs with log Kow<6 indicate that toxicity data conform to a simple log Kow-dependent QSAR. Fish were found to be more sensitive than algae while invertebrates spanned a wide range in toxicological response. Freshwater and marine species demonstrated a similar distribution of sensitivities. Comparison of species-dependent QSARs supports the hypothesis that biotransformation plays an important role in explaining toxicity differences observed between species. Estimated critical body residues (CBRs) for parent PE in fish were in the range reported for other polar organic chemicals while CBRs for parent PE plus associated metabolites were in the range reported for nonpolar narcotics (i.e., baseline toxicity) suggesting a possible putative role of PE metabolites. Depending on extrapolation procedure and assumptions, predicted no-effect concentrations (PNECs) for dimethyl, diethyl, dibutyl, and butybenzyl phthalate ranged from 3109 to 4780, 865 to 1173, 43 to 62, and 38 to 60 microg l(-1), respectively. PNECs derived using this approach provide a transparent technical basis to support aquatic risk assessment for low-molecular-weight PEs. Results for high-molecular-weight PEs (log Kow>6) indicate that these chemicals are not acutely or chronically toxic to freshwater or marine organisms due to the combined role of low water solubility and limited bioconcentration potential which precludes attainment of internal concentrations that are required to elicit adverse effects. It is concluded that attempts to establish aquatic PNECs for high-molecular-weight PEs are not scientifically defensible.

Impacts of structural photomodification on the toxicity of environmental contaminants: anthracene photooxidation products

The toxicity of polycyclic aromatic hydrocarbons (PHAs) is known to be enhanced by light via photosensitization reactions (production of active oxygen) and photomodification of the chemicals (e.g., oxidation) to more toxic compounds. Anthracene (ANT) toxicity in particular has been found to increase dramatically following photomodification. The objective of this study was to identify the photooxidation products of ANT and assess the toxicity of selected photoproducts. High performance liquid chromatography (HPLC) analysis of anthracene photooxidation revealed a complex array of oxidation products; prevalent among these were anthraquinone (ATQ) and hydroxy-anthraquinones (hATQs). Eleven of these compounds were tested for toxicity using growth inhibition of the duckweed Lemna gibba L. G-3. All but one of the compounds tested were found to be toxic, and when UV radiation was present in the light source toxicity was generally enhanced. The chemicals were also irradiated under SSR prior to toxicity testing. In about half the cases, the ATQ compounds were rapidly photooxidized and the resultant photoproducts were more toxic than the parent compounds. Interestingly, 2-hydroxyanthraquinone, which was not subject to photooxidation, was the most toxic of the compounds tested. As a light stable compound it presents the risk of a persistent environmental hazard.