Toxicity and metabolism of phthalate esters

7 Final Report on the Safety Assessment of Dibutyl Phthalate, Dimethyl Phthalate, and Diethyl Phthalate

Dibutyl Phthalate (DBP), Dimethyl Phthalate (DMP), and Diethyl Phthalate (DEP) are dialkyl phthalates used primarily in cosmetics at concentrations of less than 10 percent as plasticizers, solvents, and perfume fixatives.

These phthalates are rapidly absorbed, metabolized, and excreted. Acute animal feeding studies indicate that these ingredients are nontoxic. The results of most subchronic and chronic tests indicate that these ingredients are relatively nontoxic to rats. The oral administration of DBP produced testicular atrophy in various test rodents. The available data are not adequate to prove that these ingredients are teratogenic agents to experimental animals. This was not observed after the administration of DMP and DEP. Undiluted DBP, DMP, and DEP produced only minimal irritation to eyes of rabbits.

The mutagenic activity of DBP, DMP, and DEP toward Salmonella typhimurium mutants is essentially negative, but some assays reported positive findings. Carcinogenesis was not observed in DBP feeding studies.

Limited clinical data on DBP, DMP, and DEP indicate that these ingredients are not human skin irritants, sensitizers, or phototoxic agents. On the basis of the available data, it is concluded that these compounds are safe for topical application in the present practices of use and concentration in cosmetics.

An interlaboratory comparison study for the determination of dialkyl phthalate esters in environmental and biological samples

A series of interlaboratory comparison exercises were conducted to assess the accuracy of dialkyl phthalate ester (DPE) concentration measurements in environmental and biological samples. Five laboratories participated in analyses to determine DPE concentrations in standard test solutions; marine sediments; three certified reference materials, including CARP-2 (fish muscle) and BCR-07 (fortified milk powder); and several livestock samples (sheep's milk, liver, and muscle). In addition, one laboratory determined DPE residue concentrations in 20 municipal sewage sludge samples, previously analyzed as part of the 2006/2007 U.S. Environmental Protection Agency's Targeted National Sewage Sludge Survey (TNSSS). The results showed relatively good interlaboratory agreement for analyses of di-ethylhexyl phthalate (DEHP). Three independent laboratories (Labs A, B, and C) reported concentrations of DEHP (ng/g wet wt) in fish muscle (CARP-2) of 1,550 ± 148, 1,410 ± 193, and 1,380 ± 187, respectively. Similarly, DEHP concentration measurements in sewage sludge samples showed good agreement with those reported in the 2006/2007 TNSSS report. Measured concentrations of individual DPEs and C6-C10 isomeric mixtures in these samples of municipal sewage sludge, which have not been previously reported, ranged between 1 and 200,000 ng/g dry weight. The results demonstrate that environmental monitoring of DPEs is often hampered by high method detection limits (MDLs), due to contamination of procedural blanks. It is important to note, however, that when background contamination is minimized (<10 ng/sample), relatively low MDLs (<0.1 ng/g) can be achieved, allowing for low-level quantification of DPEs in environmental and biological samples. Future efforts to develop better protocols to lower MDLs, as well to develop reference materials, would greatly benefit future DPE monitoring initiatives.

Ultra-trace determination of phthalate ester metabolites in seawater, sediments, and biota from an urbanized marine inlet by LC/ESI-MS/MS

This study presents results of an analytical method developed for the quantification of monoalkyl phthalate esters (MPEs) in seawater, sediments, and biota. The method uses accelerated solvent extraction, solid-phase extraction, and liquid chromatography electrospray ionization tandem mass spectrometry (LC/ ESI-MS/MS). Results show the method is robust and can provide trace measurement of several MPE analytes at low parts per trillion levels in water and low parts per billion levels in sediments and biological tissues. Analyte recoveries varied between 70% and 110%. Method detection limits (MDLs) varied between 0.19 and 3.98 ng/L in seawater and between 0.024 and 0.99 ng/g in sediment and biota, which is approximately 10-50 times lower than previously reported MDLs using gas chromatography mass spectrometry. We applied the method to field collected samples of seawater, sediments, and tissues of mussels, crabs, and fish from False Creek an urbanized marine inlet near Vancouver, Canada. The results indicate residues of several MPEs can be found in surface waters, sediments, and organism tissues of this marine system. Monoethyl phthalate (MEP), mono-n-butyl phthalate (MnBP), and mono-(2-ethylhexyl)-phthalate (MEHP) were frequently detected in all matrices. MnBP generally exhibited the highest concentrations among MPEs analyzed. Detectable concentrations of MPEs varied from 1 to 600 ng/L in seawater, 0.1 to 20 ng/g dry wt in sediments, and 0.1 to 600 ng/g wet wt in biota. Observed concentrations of low molecular weight MPEs in mussels were found to be significantly higher (P < 0.05) than those of corresponding parent DPEs (e.g., MnBP > DBP). Mono-iso-nonyl-phthalate (MoC9) and mono-iso-decyl phthalate (MoC10), which were routinely detected in water and sediments, were not detected in False Creek biota, indicating negligible uptake and/or in vivo bioformation of these high molecular weight MPEs. The ability to measure MPEs in complex environmental samples provided by this LC/ESI-MS/MS method expands the capability for future biomonitoring and risk assessment of phthalate plasticizers.

Biosynthesis of di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) from red alga--Bangia atropurpurea

The contents of di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) of red alga, Bangia atropurpurea, filaments cultured in artificial sea water medium were similar to those cultured in natural sea water medium. In the culture experiment, B. atropurpurea filaments were found to synthesize de novo phthalate esters. Additionally, DEHP and DBP contents in different species of algae grown in the same environment were different significantly, suggesting that it was due to the intrinsic nature of algae.

SUBCELLULAR DISTRIBUTION OF DI-(2-ETHYLHEXYL)PHTHALATE IN RAT TESTIS

Subcellular distribution of di-(2-ethylhexyl)phthalate (DEHP) in the testis was studied by single oral administration of [3,4,5,6-(3)H]-phthalic acid di-(2-ethylhexyl) ester (DEHP-3H) or phthalic acid di-(2-ethyl[1-(3)H]hexyl) ester (3H-DEHP) to 8-week-old male rats. Autoradiographs and electron microscopic autoradiographs were prepared from the testis, liver and kidney at 6 and 24 hr after administration and distribution of radioactive materials in the tissues were observed. In the autoradiographic specimen at 6 hr after administration of DEHP 3H-labeled at phthalic acid moiety (DEHP-3H), many grains were observed in the testis, mainly at the basal area of seminiferous tubules at the stages IX to I of the spermatogenic cycle. Electron microscopic autoradiographs taken at the same time revealed that localization of grains were in the smooth-surfaced endoplasmic reticulum and mitochondria of Sertoli cells. A few grains were also present at the Golgi apparatus and lysosome of Sertoli cells, and at the interfaces between the Sertoli cells or between Sertoli cells and spermatocytes, and in the cytoplasm of spermatocytes. Autoradiographs of the liver revealed grains in the centrilobular hepatocytes, localized at mitochondria, rough-surfaced endoplasmic reticulum and peroxisomes. In the kidney, the radioactivity was localized at the brush border of the tubular cells in the pars recta of proximal tubules. In the 24-hr specimen, the grain density in the seminiferous tubules obviously decreased. On the other hand, by autoradiography with DEHP 3H-labeled at the alcohol (3H-DEHP), only a few grains were observed in autoradiographs of the testes at 6 hr after administration. No grains were noted in autoradiographs of the liver and kidney with 3H-DEHP. The results showed that the phthalic acid ester was splitted rapidly in the body and only the phthalic acid moiety distributed into the cells.

Effect of the dietary exposure of rat to di(2-ethyl hexyl) phthalate on their metabolic efficiency

The nutritional impact of di(2-ethyl hexyl) phthalate (DEHP), specifically its energy efficiency and nitrogen utilization, was studied in the experimental rat. Groups of male Wistar rats were fed over 21 days with a standard diet alone or a standard diet supplemented with 2% (w/w) DEHP. Food intake, body weight and nitrogen compounds excretion were measured daily. The composition and energetic content of the carcass were determined in animals of both dietary groups after the feeding period, as well as in a separate group on day 0. The food and energy intakes were similar in both groups, however, the efficiencies of energy and nitrogen use were significantly reduced in the DEHP-fed rat. These alterations were reflected by a reduction of 31% on carcass energy retention and a decrease of 26% on cumulative nitrogen balance, without changes in the body composition. The increase of urinary nitrogen excretion, mainly as urea compound, is the major contributing factor to the lower nitrogen retention. These results indicate that DEHP decreases energy efficiency and nitrogen utilization, leading to a pronounced reduction in body weight gain. In addition, this study provides a possible conceptual framework that could explain the metabolic changes induced by DEHP and related compounds in experimental animals.

Polyethylene oxide additive-entrapped polyvinyl chloride as a new blood bag material

Until now, most widely used blood bag material has been a plasticized polyvinyl chloride (PVC) because it has many desirable properties as a blood bag material. One of main concerns of using plasticized PVC as a blood bag material is the toxicity of the plasticizers that are leached out of the material. We tried to solve this problem by the addition of polyethylene oxide (PEO)-containing amphiphilic block copolymers as additives in the PVC. The PEO additives may play two roles: they can act as nontoxic plasticizers to PVC, and they can also act as blood-compatible surface modifiers. In this study, PEO additive-entrapped PVC films were prepared by the addition (up to 30 wt%) of PEO-alkyl carbon block copolymers or PEO-polypropylene oxide (PPO)-PEO triblock copolymers with different PEO chain lengths in the PVC. The prepared PEO additive-containing PVC films were characterized by the measurements of water contact angle, Fourier transform IR spectroscopy in the attenuated total reflectance mode, mechanical properties (tensile strength and elongation at break), water absorption, and stability of the PEO additives entrapped in the films. It was observed that the PEO additive-entrapped PVC films were flexible and transparent. It seems that the PEO additives are surface active, resulting in the considerable change of surface characteristics without a significant change of the mechanical properties of the films compared to the control PVC without any additives or a commercial blood bag. The adhesion of platelets on the film surfaces was significantly reduced by the addition of PEO additives. It seems that 10% addition of PEO additives is enough for the suppression of platelet adhesion on the surfaces. This study demonstrated that the use of PEO-containing block copolymers as additives to the PVC can be a feasible approach to prepare a new type of blood bag.

Developmental toxicity evaluation of phthalic acid, one of the metabolites of phthalic acid esters, in rats

The objective of this study was to evaluate the developmental toxicity of phthalic acid (PA), which is one of the metabolites of phthalic acid esters (PAEs). Pregnant rats were given PA at a dose of 0 (control), 1.25, 2.5, or 5.0% in the diet on day 7 through day 16 of pregnancy. Average daily intakes of PA were 1021 mg/kg for the 1.25% group, 1763 mg/kg for the 2.5% group, and 2981 mg/kg for the 5.0% group. Maternal toxicity occurred in the 2.5 and 5.0% groups as can be seen by significant decreases in the maternal body weight gain and food consumption during the administration period. No significant changes in maternal parameters were found in the 1.25% group. Neither deaths nor clinical signs of toxicity were noted in any groups. No significant changes induced by PA were detected in the incidence of postimplantation loss and number and sex ratio of live fetuses. Significant decreases in the weight of male fetuses and number of ossification center of the caudal vertebrae were found in the 5.0% group. Morphological examinations of fetuses revealed no evidence of teratogenesis. Thus it appears unlikely that PA may be responsible for the production of the developmental toxicity of PAEs.

Effects of chronic di(2-ethylhexyl) phthalate intake on the secretion and removal rate of triglyceride-rich lipoproteins in rats

This work intends to characterize the nature of the plasma triglyceride level decrease in male Wistar rats fed with diets supplemented with 2% (w/w) di(2-ethylhexyl) phthalate (DEHP), a packaged-food chemical contaminant. After being fed for 21 days, the animals were assessed to determine plasma and liver lipids or to quantify the in vivo hepatic secretion and in vitro plasma removal of triglyceride-rich lipoproteins. The liver cholesterol and triglyceride contents in DEHP-fed rats were closely similar to those found in controls, co-existing with a decrease in plasma cholesterol (19%), phospholipid (14%) and triglyceride (36%) levels. The decrease of the plasma triglyceride pool size was not associated with a reduction in hepatic secretion of triglyceride. The total triglyceride lipase activity rose (32%) due to a remarkable increase (100%) of the extrahepatic lipoprotein lipase activity. We can conclude that extrahepatic lipoprotein lipase activity accounts for the hypotriglyceridaemic effect of DEHP through an increase of triglyceride removal rate.

Influence of intravenous administration set composition on the sorption of isosorbide dinitrate

The influence of the composition of administration sets on the sorption of isosorbide dinitrate was investigated in-vitro. Isosorbide dinitrate solutions (250 micrograms mL-1) in 0.9% NaCl or 10% glucose were stored in glass containers and administered at a flow rate of 20 mL h-1. The influence of the concentration of different plasticizers (di-ethylhexylphthalate, tri-ethylhexyltrimelitate) in polyvinylchloride tubings was determined. Polybutadiene tubings of different mol. wt coextruded laminates of these polybutadienes with PVC of different composition and a polyethylene tubing were evaluated. The higher the Shore hardness of the PVC tubing, the lower the sorption. The infusion fluid played an additional role only for the tubings with high Shore hardness (greater than 70). The sorption of isosorbide dinitrate to polybutadiene tubings of different mol. wt was less than 2.5% after 5 h and was comparable with the sorption to the polyethylene tubing. When polybutadiene/PVC laminates were used, the sorption increased significantly and was in most cases dependent on the Shore hardness of the PVC (higher Shore hardness gave lower sorptions) and on the mol. wt of the polybutadiene (lower mol. wt resulted in higher sorption). Sorption was not dependent on the type of PVC plasticizer.

Effects of co-administration of di(2-ethylhexyl)phthalate and testosterone on several parameters in the testis and pharmacokinetics of its mono-de-esterified metabolite

The administration of 1 g/kg di(2-ethylhexyl)phthalate (DEHP) or 5 mg/kg testosterone for 1 week did not affect the testicular and prostatic gland weights in rats. However, co-administration of DEHP and testosterone induced severe testicular atrophy accompanied by a decrease of zinc concentration in the testis and reduction of the activity of testicular specific lactate dehydrogenase isozyme. These changes were similar to the results of high dose administration of DEHP alone. Values of biological half-life and area under the concentration-time curve (AUC) of mono(2-ethylhexyl)phthalate, the main metabolite of DEHP, in testes after a single co-administration of DEHP (p.o.) and testosterone (i.p.) were higher than those after DEHP administration alone. Results suggest that the co-administration of DEHP and testosterone enhanced the adverse effects of DEHP on testes as the result of changes in pharmacokinetic values of MEHP.

Extraction of diethylhexylphthalate from total nutrient solution-containing polyvinyl chloride bags

Total nutrient solution (TNS) is a new method for delivering total parenteral nutrition (TPN) by admixing dextrose, amino acids, and lipids in a single container. Recommendations are to use nonpolyvinyl chloride (PVC) containers for admixture of these solutions. PVC is a hard, brittle, and inflexible substance, and plasticizers, predominantly diethylhexylphthalate (DEHP), are added to impart flexibility. DEHP is a lipid soluble suspected carcinogen, hepatotoxin, and teratogen which has been shown to leach from PVC products containing lipophilic admixtures. The purpose of this study was to quantitate the amount of DEHP which leaches from PVC bags containing TNS. Six study groups, which contained three formulas stored at 25 degrees C +/- 2 degrees C and 4 degrees C +/- 1 degree C, were assayed for DEHP at time 0, 12, 24, 48 and 72 hr, 1 wk, and 3 wk using high-performance liquid chromatography. The control group contained an amino acid source, a carbohydrate source, and standard electrolytes, and the other groups contained a 10% lipid source or a 20% lipid source in addition to the constituents of the control group. Lipid-containing groups demonstrated detectable levels of DEHP at 48 hr, and DEHP content increased in these groups throughout the 21-day study. DEHP concentrations were lower in lipid-containing groups stored at 4 degrees C than comparable groups stored at 25 degrees C.

Di-(2-ethylhexyl)-phthalate as plasticizer in PVC respiratory tubing systems: indications of hazardous effects on pulmonary function in mechanically ventilated, preterm infants

Several PVC medical devices contain the plasticizer Di-(2-ethylhexyl)-phthalate (DEHP) in high concentration. Taken systematically DEHP only has minor toxic effects in the human organism. In three preterm infants artificially ventilated with PVC respiratory tubes unusual lung disorders resembling those observed in hyaline membrane disease, verified both clinically and radiologically, were observed during the fourth week of life. It was assumed that these lung disorders were causally related to the exposure to high doses of DEHP, which was released from the walls of the respiratory tubes. DEHP was found in the lung tissue of one patient who died of pneumothorax soon after birth after being artificially ventilated. It is strongly recommended that for disposable PVC respiratory devices the plasticizer DEHP should be used with more restrictions.

Tissue distribution and excretion of tri-(2-ethylhexyl)trimellitate in rats

The disposition kinetics of tri-(2-ethylhexyl)trimellitate (TEHTM), a new plasticizer for polyvinyl chloride (PVC) plastic, was studied in rats following intravenous administration of [14C-carbonyl]tri-(2-ethylhexyl)trimellitate using an oil in water emulsion as the vehicle. The distribution half-life, elimination half-life, and clearance values estimated from the plasma concentration of radioactivity data obtained following iv administration of 10.5 mg/kg of TEHTM (59.9 muCi/kg), were 46.2 min, 5.34 d, and 40.5 ml/kg X h, respectively. Following iv dosage of 15.6 mg/kg of TEHTM (28.0 muCi/kg), significant accumulation of radioactivity was found in the liver, lungs, and spleen, with liver accounting for 72% of the administered dosage at 24 h. Excretion of TEHTM and its biotransformation products was slow, with 21.3% of the administered radioactivity found in the feces and 2.8% in the urine during the 14-d collection period. Biliary excretion seems to be the major route of elimination of TEHTM. The pharmacokinetic data gathered in the present investigation are compared to di-(2-ethylhexyl)phthalate (DEHP), a widely used plasticizer for PVC.

Contamination of platelet storage bags by phthalate esters

Phthalate esters are the most extensively used plasticizers in the manufacture of polyvinylchloride (PVC) plastic. Many medical devices used in the collection and storage of blood components are made of PVC plastic containing di(2-ethylhexyl) phthalate (DEHP). DEHP leaches at a rate of 100 micrograms/ml X d into platelet concentrate (PC) supernatant when PCs are stored in PVC containers. It is only possible to store PCs for 72 h in this DEHP plastic, after which time the platelet function has deteriorated and they cannot be used for transfusion therapy. Since it was desirable to find a container that permitted longer storage times and because of the concern for the toxicity of DEHP, new bags, manufactured with different plastic formulations without this plasticizer, were tested for PC storage. Using these new containers, such as the PL732 [polyolefin (PO) plastic], and the CLX300 and PL1240 [tri(2-ethylhexyl) trimellitate (TEHTM) PVC plastic], it was possible to store PCs for 5 d while preserving platelet function. In spite of these new plastic bags being manufactured without DEHP, we found DEHP and its metabolite mono(2-ethylhexyl) phthalate (MEHP) as contaminants of the supernatant of the PCs stored in these containers. After analyzing the plastic material of each of these containers, we were able to identify the source of the contamination as coming from the plastic materials that were used in the manufacture of the bags. The sterilization process of the PL732 bag was investigated, since it was found that when the plastic of the PL732 bag was analyzed prior to sterilization, no contamination by DEHP was detected; however, whether the PL732 bag was sterilized together with the primary PVC bag or separately, using ethylene oxide, contamination by DEHP was found, suggesting contamination of the sterilization unit by DEHP.

Circulating concentrations of di(2-ethylhexyl) phthalate and its de-esterified phthalic acid products following plasticizer exposure in patients receiving hemodialysis

The degree of exposure to the plasticizer di(2-ethylhexyl) phthalate (DEHP) was assessed in 11 patients undergoing maintenance hemodialysis for the treatment of renal failure. The amount of DEHP leached from the dialyzer during a 4-hr dialysis session was estimated by monitoring the DEHP blood concentration gradient across the dialyzer. Circulating concentrations of the biologically active products of DEHP de-esterification, viz., mono(2-ethylhexyl) phthalate (MEHP) and phthalic acid, were also determined during the dialysis session. On the average, an estimated 105 mg of DEHP was extracted from the dialyzer during a single dialysis session, with a range of 23.8 to 360 mg. The rate of extraction of DEHP from the dialyzer was correlated with serum lipid content as expressed by the sum of serum cholesterol and triglyceride concentrations (r = +0.65, p less than 0.05). Time-averaged circulating concentrations of MEHP during dialysis (1.33 +/- 0.58 micrograms/ml) were similar to those of DEHP (1.91 +/- 2.11 micrograms/ml). Blood concentrations of phthalic acid (5.22 +/- 3.94 micrograms/ml) were higher than those of the esters. The length of time patients had been receiving regular dialysis treatment was not a determinant of circulating concentrations of DEHP or MEHP. In contrast, time-averaged circulating concentrations of phthalic acid correlated strongly with the duration (in years) of dialysis treatment (r = +0.92, p less than 0.001). The results indicated substantial exposure to DEHP during hemodialysis and that the de-esterified products of DEHP are present in significant concentrations in the systemic circulation. Further study is needed to assess the contribution of these metabolites to the biological actions of DEHP in man.

Comparison of the short-term effects of di(2-ethylhexyl) phthalate, di(n-hexyl) phthalate, and di(n-octyl) phthalate in rats

This study compares changes in the livers of rats treated with di(2-ethylhexyl) phthalate (DEHP) and its straight-chain analogs di(n-hexyl) phthalate (DnHP) and di(n-octyl phthalate (DnOP). Groups of rats were fed diets containing 20,000 ppm of one of these compounds. Subgroups were killed after 3, 10, and 21 days, and the livers were examined by histological, cytological, and biochemical methods. The results show considerable differences between the effects of the branched-chain phthalate ester DEHP and its straight-chain analogs. The major effects on the liver following administration of diets containing DEHP were midzonal and periportal accumulation of small droplets of lipid, hepatomegaly accompanied by an initial burst of mitosis, proliferation of hepatic peroxisomes and of smooth endoplasmic reticulum accompanied by induction of peroxisomal fatty acid oxidation, damage to the peroxisomal membranes as evidenced by increased leakage of catalase to the cytosol, and centrilobular loss of glycogen and falls in glucose-6-phosphatase activity and in low-molecular-weight reducing agents. In contrast, diets containing DnHP or DnOP induced accumulation of large droplets of fat around central veins leading, by 10 days, to mild centrilobular necrosis and a very slight induction of one peroxisomal enzyme and an increase in liver weight, but no significant changes in any other parameters which were affected by DEHP.

Biological effects of di-(2-ethylhexyl) phthalate and other phthalic acid esters

Esters of o-phthalic acid are widely distributed in the ecosystem. The phthalate acid esters (PAE's) are used as plasticizers in the manufacture of polyvinylchlorides. They are also used as solvents in certain industrial processes and as vehicles for pesticides. The PAE's are used in enormous quantities for a variety of industrial uses in the formulation of plastics. While there are a number of important PAE's, di-ethylhexyl phthalate has perhaps been used the most extensively in the formulation of plastics used in medical devices and blood bag assemblies. The metabolism, biodistribution and excretion varies to some extent among the various PAE's. There are species differences with respect to the metabolism of the PAE's. The route of administration, and the level and length of exposure, are known to affect the toxicological profile of the various PAE's. There is little evidence of bioaccumulation of the various PAE's, and only at very large doses have there been reports of overt toxicity. Evidence for the carcinogenicity of certain PAE's apparently is related to prolonged exposure to high levels.

Polar metabolites of di-(2-ethylhexyl)phthalate in the rat

Di-(2-ethylhexyl)phthalate (DEHP) is an important industrial chemical widely used as a plasticizer for vinyl and other plastics. DEHP is extensively metabolized by mammals, different species showing dramatic differences in metabolite distributions. Previous studies of the metabolism in rats led to the suggestion that the enzymatic processes normally associated with omega-, omega-1, alpha-, and beta-oxidation of fatty acids could account for the known metabolites of DEHP found in the urine. Several additional metabolites of DEHP have been identified in the present study. Their formation requires that the initial hydroxylation process be less specific than fatty acid omega- and omega-1 oxidation are thought to be. Furthermore, it is necessary to postulate either that the aliphatic chain of mono-(2-ethylhexyl)phthalate can be oxidized at two sites simultaneously, or that oxidation products can be recycled for a second hydroxylation prior to excretion.

Phthalate esters I: Effects on cytochrome P-450 mediated metabolism in rat liver and lung, serum enzymatic activities and serum protein levels

Dimethylphthalate (DMP), dibutylphthalate (DBP) and di(2-ethylhexyl)phthalate (DEHP) were given i.p. (3.8 mM/kg) to Sprague Dawley rats for 5 days. DBP increased significantly the liver concentration of cytochrome P-450, but decreased the lung concentration by about 40%. DBP decreased the lung concentration of cytochrome b5 and NADPH-cytochrome-c-reductase activity by about 30%. Only minor effects were seen after treatment with DMP and DEHP. The direction of B(a)P metabolism was changed and the formation of 2- and 3-hexanol metabolites were increased in liver microsomes after DBP treatment. All phthalate esters decreased the lung metabolism of B(a)P. The cytochrome P-450 enzyme system in the lung was ten times more effective than that in the liver as far as metabolism of n-hexane was concerned. Only minor effects were observed in serum enzyme activities, but a significant decrease in the serum level of albumin was observed after treatment with DBP. No relationship was found between the carbon chain length of the investigated chemicals and effects on microsomal enzymatic activities.

Toxicity and metabolism of monoethylhexyl phthalate and diethylhexyl phthalate: a survey of recent literature

The literature dealing with monoethylhexyl phthalate (MEHP), the principal metabolite of di (2-ethylhexyl) phthalate (DEHP), a widely used plasticizer, is discussed. MEHP has been shown to be moderately toxic and, following oral administration, undergoes omega- and omega- 1 oxidation to yield the same metabolites as does DEHP. In plasma there is an equilibrium between MEHP absorbed to albumin and in free solution, whereas DEHP is bound to lipoproteins. Studies involving orally administered MEHP revealed the mild hepatic changes occurred but there was no bioaccumulation of the monoester. Studies of the rat and rabbit indicated that MEHP has no teratogenic effects.

Degradation of Phthalic Acids by Denitrifying, Mixed Cultures of Bacteria

Mixed cultures of bacteria, enriched from aquatic sediments, grew anaerobically on all three isomers of phthalic acid. Each culture grew anaerobically on only one isomer and also grew aerobically on the same isomer. Pure cultures were isolated from the phthalic acid ( o -phthalic acid) and isophthalic acid ( m -phthalic acid) enrichments that grew aerobically on phthalic and isophthalic acids. Cell suspension experiments indicated that protocatechuate is an intermediate of aerobic catabolism. Pure cultures which grew aerobically on terephthalic acid ( p -phthalic acid) could not be isolated from the enrichments, and neither could pure cultures that grew anaerobically on any of the isomers. Cell suspension experiments suggested that separate pathways exist for the aerobic and anaerobic oxidation of phthalic acids. Each enrichment culture used only one phthalic acid isomer under anaerobic conditions, but all isomers were simultaneously adapted for the anaerobic catabolism of benzoate. Cells grown anaerobically on a phthalic acid immediately attacked the isomer under anaerobic conditions, whereas there was a lag before aerobic breakdown occurred, and, for phthalic and terephthalic acids, chloramphenicol stopped aerobic adaptation but had no effect on anaerobic catabolism. This work suggests that phthalic acids are biodegradable in anaerobic environments.