Studies on the effects of orally administered Di-(2-ethylhexyl) phthalate in the ferret

Liver hypertrophy: a review of adaptive (adverse and non-adverse) changes--conclusions from the 3rd International ESTP Expert Workshop

Preclinical toxicity studies have demonstrated that exposure of laboratory animals to liver enzyme inducers during preclinical safety assessment results in a signature of toxicological changes characterized by an increase in liver weight, hepatocellular hypertrophy, cell proliferation, and, frequently in long-term (life-time) studies, hepatocarcinogenesis. Recent advances over the last decade have revealed that for many xenobiotics, these changes may be induced through a common mechanism of action involving activation of the nuclear hormone receptors CAR, PXR, or PPARα. The generation of genetically engineered mice that express altered versions of these nuclear hormone receptors, together with other avenues of investigation, have now demonstrated that sensitivity to many of these effects is rodent-specific. These data are consistent with the available epidemiological and empirical human evidence and lend support to the scientific opinion that these changes have little relevance to man. The ESTP therefore convened an international panel of experts to debate the evidence in order to more clearly define for toxicologic pathologists what is considered adverse in the context of hepatocellular hypertrophy. The results of this workshop concluded that hepatomegaly as a consequence of hepatocellular hypertrophy without histologic or clinical pathology alterations indicative of liver toxicity was considered an adaptive and a non-adverse reaction. This conclusion should normally be reached by an integrative weight of evidence approach.

Components of plastic: experimental studies in animals and relevance for human health

Components used in plastics, such as phthalates, bisphenol A (BPA), polybrominated diphenyl ethers (PBDE) and tetrabromobisphenol A (TBBPA), are detected in humans. In addition to their utility in plastics, an inadvertent characteristic of these chemicals is the ability to alter the endocrine system. Phthalates function as anti-androgens while the main action attributed to BPA is oestrogen-like activity. PBDE and TBBPA have been shown to disrupt thyroid hormone homeostasis while PBDEs also exhibit anti-androgen action. Experimental investigations in animals indicate a wide variety of effects associated with exposure to these compounds, causing concern regarding potential risk to human health. For example, the spectrum of effects following perinatal exposure of male rats to phthalates has remarkable similarities to the testicular dysgenesis syndrome in humans. Concentrations of BPA in the foetal mouse within the range of unconjugated BPA levels observed in human foetal blood have produced effects in animal experiments. Finally, thyroid hormones are essential for normal neurological development and reproductive function. Human body burdens of these chemicals are detected with high prevalence, and concentrations in young children, a group particularly sensitive to exogenous insults, are typically higher, indicating the need to decrease exposure to these compounds.

Transgenerational effects of Di (2-ethylhexyl) phthalate in the male CRL:CD(SD) rat: added value of assessing multiple offspring per litter

In the rat, some phthalates alter sexual differentiation at relatively low dosage levels by altering fetal Leydig cell development and hormone synthesis, thereby inducing abnormalities of the testis, gubernacular ligaments, epididymis, and other androgen-dependent tissues. In order to define the dose-response relationship between di(2-ethylhexyl) phthalate (DEHP) and the Phthalate Syndrome of reproductive alterations in F1 male rats, Sprague-Dawley (SD) rat dams were dosed by gavage from gestational day 8 to day 17 of lactation with 0, 11, 33, 100, or 300 mg/kg/day DEHP (71-93 males per dose from 12 to 14 litters per dose). Some of the male offspring continued to be exposed to DEHP via gavage from 18 days of age to necropsy at 63-65 days of age (PUB cohort; 16-20/dose). Remaining males were not exposed after postnatal day 17 (in utero-lactational [IUL] cohort) and were necropsied after reaching full maturity. Anogenital distance, sperm counts and reproductive organ weights were reduced in F1 males in the 300 mg/kg/day group and they displayed retained nipples. In the IUL cohort, seminal vesicle weight also was reduced at 100 mg/kg/day. In contrast, serum testosterone and estradiol levels were unaffected in either the PUB or IUL cohorts at necropsy. A significant percentage of F1 males displayed one or more Phthalate Syndrome lesions at 11 mg/kg/day DEHP and above. We were able to detect effects in the lower dose groups only because we examined all the males in each litter rather than only one male per litter. Power calculations demonstrate how using multiple males versus one male/litter enhances the detection of the effects of DEHP. The results at 11 mg/kg/day confirm those reported from a National Toxicology Program multigenerational study which reported no observed adverse effect levels-lowest observed adverse effect levels of 5 and 10 mg/kg/day DEHP, respectively, via the diet.

Fifteen years after "Wingspread"--environmental endocrine disrupters and human and wildlife health: where we are today and where we need to go

In 1991, a group of expert scientists at a Wingspread work session on endocrine-disrupting chemicals (EDCs) concluded that "Many compounds introduced into the environment by human activity are capable of disrupting the endocrine system of animals, including fish, wildlife, and humans. Endocrine disruption can be profound because of the crucial role hormones play in controlling development." Since that time, there have been numerous documented examples of adverse effects of EDCs in invertebrates, fish, wildlife, domestic animals, and humans. Hormonal systems can be disrupted by numerous different anthropogenic chemicals including antiandrogens, androgens, estrogens, AhR agonists, inhibitors of steroid hormone synthesis, antithyroid substances, and retinoid agonists. In addition, pathways and targets for endocrine disruption extend beyond the traditional estrogen/androgen/thyroid receptor-mediated reproductive and developmental systems. For example, scientists have expressed concern about the potential role of EDCs in increasing trends in early puberty in girls, obesity and type II diabetes in the United States and other populations. New concerns include complex endocrine alterations induced by mixtures of chemicals, an issue broadened due to the growing awareness that EDCs present in the environment include a variety of potent human and veterinary pharmaceutical products, personal care products, nutraceuticals and phytosterols. In this review we (1) address what have we learned about the effects of EDCs on fish, wildlife, and human health, (2) discuss representative animal studies on (anti)androgens, estrogens and 2,3,7,8-tetrachlorodibenzo-p-dioxin-like chemicals, and (3) evaluate regulatory proposals being considered for screening and testing these chemicals.

Diethylhexyl phthalate impairs insulin binding and glucose oxidation in Chang liver cells

The present study examined the dose-dependent effects of diethylhexyl phthalate (DEHP) on insulin receptor concentration and glucose oxidation in Chang liver cells. Chang liver cells (5 x 10(5) cells) were exposed to different concentrations (0, 50, 100, 200 and 400 microM) of DEHP for 24h. At the end of exposure, cells were utilized for assessing insulin receptor concentration and glucose oxidation. Both insulin receptor concentration and glucose oxidation in Chang liver cells were significantly reduced by high doses (200 and 400 microM) of phthalate exposure. The present study is first of its kind to report the direct adverse effects of DEHP on insulin receptor and glucose oxidation in Chang liver cells and suggests that DEHP exposure may have a negative influence on glucose homeostasis.

Disruption of reproductive development in male rat offspring following in utero exposure to phthalate esters

Certain Phthalate esters have been shown to produce reproductive toxicity in male rodents with an age dependent sensitivity in effects with foetal animals being more sensitive than neonates which are in turn more sensitive than pubertal and adult animals. While the testicular effects of phthalates in rats have been known for more than 30 years, recent attention has been focused on the ability of these agents to produce effects on reproductive development in male offspring after in utero exposure. These esters and in particular di-butyl, di-(2-ethylhexyl) and butyl benzyl phthalates have been shown to produce a syndrome of reproductive abnormalities characterized by malformations of the epididymis, vas deferens, seminal vesicles, prostate, external genitalia (hypospadias), cryptorchidism and testicular injury together with permanent changes (feminization) in the retention of nipples/areolae (sexually dimorphic structures in rodents) and demasculinization of the growth of the perineum resulting in a reduced anogenital distance (AGD). Critical to the induction of these effects is a marked reduction in foetal testicular testosterone production at the critical window for the development of the reproductive tract normally under androgen control. A second Leydig cell product, insl3, is also significantly down regulated and is likely responsible for the cryptorchidism commonly seen in these phthalate-treated animals. The testosterone decrease is mediated by changes in gene expression of a number of enzymes and transport proteins involved in normal testosterone biosynthesis and transport in the foetal Leydig cell. Alterations in the foetal seminiferous cords are also noted after in utero phthalate treatment with the induction of multinucleate gonocytes that contribute to lowered spermatocyte numbers in postnatal animals. The phthalate syndrome of effects on reproductive development has parallels with the reported human testicular dysgenesis syndrome, although no cause and effect relationship exists after exposure of humans to phthalate esters. However humans are exposed to and produce the critical phthalate metabolites that have been detected in blood of the general population, in children and also human amniotic fluid.

Peroxisome Proliferator-Activated Receptors: Mediators of Phthalate Ester-Induced Effects in the Male Reproductive Tract?

Many phthalate ester plasticizers are classified as peroxisome proliferators (PP), a large group of industrial and pharmaceutical chemicals. Like PP, exposure to some phthalates increases hepatocyte peroxisome and cellular proliferation, as well as the incidence of hepatocellular adenomas in mice and rats. Most effects of PP are mediated by three nuclear receptors called peroxisome proliferator-activated receptors (PPARalpha,beta,gamma). An obligate role for PPARalpha in PP-induced events leading to liver cancer is well-established. Exposure of rats in utero or in the neonate to a subset of phthalate esters causes profound, sometimes irreversible malformations in the male reproductive tract. We review here the data that supports or discounts roles for PPARs in phthalate-induced testis toxicity including (1) toxic effects of phthalates on the male reproductive tract, (2) expression of PPARs in the testis, (3) activation of PPARs by phthalates, (4) role of PPARalpha in testis toxicity, (5) gene targets of phthalates involved in steroid biosynthesis and catabolism, and (6) interactions between PPARs and other nuclear receptors that play roles in testis development and homeostasis. Critical research needs are identified that will help determine the significance of PPARs in phthalate-induced effects in the rat male reproductive tract and the relevance of toxicity to humans.

Spontaneous development of fatty liver in ferrets in a toxicology study

Ferrets were maintained for 12 months on different diets (A, meat and biscuit; B, all meat; C, meat and fish; D, high fibre) to ascertain the cause of spontaneous development of fatty liver. High hepatic triglyceride contents resulted on diets B = C > D; whereas ferrets on diet A (control) showed no accumulation of lipid in liver. Serum triglyceride and total cholesterol were unchanged by diet. These ferrets (F0 generation) were mated with ferrets on the same diet and the offspring (F1 generation), maintained on the same diets as the parents, were killed at 12 months and the livers studied similarly. Histology showed that hepatic lipid accumulation in the F1 generation was identical with that in the same dietary groups of the F0 generation; liver glutathione (GSH) reductase and thiobarbituric acid-reacting substances (an index of lipid peroxidation) were increased in ferrets maintained on diets B, C and D, liver GSH concentration and GSH peroxidase activities were unchanged. Other ferrets fed a high-fat diet (diet A plus 20% w/w beef suet) for 18 days exhibited hepatic lipid accumulation and decreased hepatic cyanide-insensitive palmitoyl CoA oxidation (-30%), but hepatic lauric acid hydroxylation and carnitine acyl transferase activities were unchanged. These data indicate that ferrets on high-fat diets show no increased rates of liver fatty acid oxidation, as seen in rats, but instead accumulate triglyceride in the liver with some degree of lipid peroxidation.

Effects of phthalic acid esters on the liver and thyroid

The effects, over periods from 3 days to 9 months of administration, of diets containing di-2-ethylhexyl phthalate are very similar to those observed in rats administered diets containing hypolipidemic drugs such as clofibrate. Changes occur in a characteristic order commencing with alterations in the distribution of lipid within the liver, quickly followed by proliferation of hepatic peroxisomes and induction of the specialized P-450 isoenzyme(s) catalyzing omega oxidation of fatty acids. There follows a phase of mild liver damage indicated by induction of glucose-6-phosphatase activity and a loss of glycogen, eventually leading to the formation of enlarged lysosomes through autophagy and the accumulation of lipofuscin. Associated changes are found in the kidney and thyroid. The renal changes are limited to the proximal convoluted tubules and are generally similar to changes found in the liver. The effects on the thyroid are more marked. Although the levels of thyroxine in plasma fail to about half normal values, serum triiodothyronine remains close to normal values while the appearance of the thyroid varies, very marked hyperactivity being noted 7 days after commencement of treatment, this is less marked at 14 days, but even after 9 months treatment there is clear cut evidence for hyperactivity with colloid changes which indicate this has persisted for some time. Straight chain analogs of di-2-ethylhexyl phthalate, di-n-hexyl phthalate and di-n-oxtyl phthalate differ entirely in their short-term effects on the liver and kidney but have similar effects on the thyroid. The short-term in vivo hepatic effects of the three phthalate esters can be reproduced in hepatocytes in tissue culture. All three phthalate esters, as well as clofibrate, have early marked effects on the metabolism of fatty acids in isolated hepatocytes. The nature of these changes is such as to increase storage of lipid in the liver. A hypothesis is presented to explain the progress from these initial metabolic effects to the final formation of liver tumors.

Influence of dietary zinc on di(2-ethylhexyl)phthalate-induced testicular atrophy and zinc depletion in adult rats

Groups of 48 adult male F344 rats were maintained on synthetic diets containing 20 ppm (normal), 2 ppm (low), or 200 ppm (high) zinc. After 1 week of acclimation to the various diets, groups of 12 rats from each dietary regimen were gavaged for 13 consecutive days with 0.0 (vehicle), 0.33, 1.0, or 3.0 g/kg di(2-ethylhexyl)phthalate (DEHP). These were selected as relatively nontoxic, mildly toxic, and moderately toxic doses for producing testicular injury in adult male rats. At termination on the 14th day, body weight gain was reduced by 3.0 g/kg DEHP dose in the normal and low-zinc diet groups but not in the high-zinc diet group. The low-zinc diet alone reduced body weight gain, independent of DEHP treatment. DEHP had no perceptible effects on the weights of testis, seminal vesicle, prostate, or epididymis from rats maintained on normal- or high-zinc diets, but reduced the weights of all of these organs from animals on the low-zinc diet in a dose-dependent manner. Lactate dehydrogenase activity, total and free sulfhydryl contents, and zinc concentrations in testes were also reduced, and testicular degeneration was induced by DEHP in the low-zinc diet groups. In contrast, dose-dependent liver enlargement and hypolipidemia (reduction of serum cholesterol and triglyceride concentrations) were produced by equivalent doses of DEHP in all of the three zinc groups. The selectively enhanced susceptibility of adult male F344 rats on a zinc deficient diet to the gonadotoxic effects of DEHP supports the hypothesis that testicular zinc depletion is causally related to the ensuing testicular and accessory sex organ atrophies. Other biological effects of DEHP (e.g., hypolipidemia, hepatomegaly) appear to occur independent of zinc homeostasis.

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.

In vitro activation of the promutagens 2-acetamidofluorene, cyclophosphamide and 7,12-dimethylbenzanthracene by constitutive ferret and rat hepatic S-9 fractions

The ability of the ferret to metabolically activate promutagenic compounds was compared with that of the rat, using the Salmonella/microsome assay. Three compounds which require biotransformation to mutagenic metabolites, 2-acetamidofluorene (2-AAF), cyclophosphamide (CPA), and 7,12-dimethylbenzanthracene (DMBA), were studied. Metabolic activation was provided by ferret or rat hepatic S-9 fractions at 5 levels for each chemical, and optimal S-9 levels as well as dose-response curves were obtained. Interspecies mutagenic activity was quantitated on the basis of mg liver, mg S-9 protein, and nmoles P-450. The slopes of the dose-response curves and the lowest chemical dose required for a significant response were also compared. Although constitutive levels of rat hepatic cytochrome P-450 were shown to be higher than those of the ferret, in vitro mutagenic activation by ferret S-9, at S-9 levels which caused activation in both species, was greater than or equivalent to activation by rat S-9 for these chemicals, based on all parameters studied. The results showed that the equilibrium between activation and detoxification reactions is dependent upon the chemical dose and S-9 level present.

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.

A review of possible toxicity of di-2-ethylhexylphthalate (DEHP) in plastic intravenous containers: effects on reproduction

Many containers for intravenous solutions are made with plasticized polyvinyl chloride, the common form of which is di-2-ethylhexylphthalate (DEHP). Extraction of DEHP into blood and plasma stored in such plastic containers can occur, and harmful effects of DEHP in the human body consequently have been suggested. Reports on toxicity of DEHP in animals during pregnancy and the developmental period are critically reviewed.

Comment on the carcinogenic potential of di(2-ethylhexyl) phthalate

Analysis of the carcinogen bioassay of di(2-ethylhexyl) phthalate (DEHP) has shown that the designated maximum tolerated dose was exceeded in the low- and high-dose groups of male rats, in the high-dose group of female rats, and in the low- and high-dose groups of female mice. Significant differences in tumor incidence among small populations of laboratory animals within the testing facility further confounded interpretation of the bioassay. Critical data on food consumption, nutritional status, clinical signs, clinical pathology, and intestinal microorganisms are lacking. This review concludes that because of major deficiencies in the available data, the studies cannot be interpreted as showing a carcinogenic effect due to DEHP alone. Epigenetic mechanisms to explain the biologic effects are examined.

A whole body autoradiographic study on the distribution of 14C-labelled di-(2-ethylhexyl)phthalate in mice

Di-(2-ethylhexyl)phthalate (DEHP), a plasticizer used for polyvinylchloride polymers, has been reported to leach from blood transfusion bags and the plastic material in hemodialysis units into the blood. Phthalate esters are known to be hepatotoxic and teratogenic in experimental animals. Reports on the distribution and metabolism of DEHP indicate that the compound in largely excreted from the body within a few days. In the present investigation the distribution and tissue retention after administration of [14C]DEHP (carbonyl-14C or 2-ethylhexyl-1-14c) was studied in pregnant and non-pregnant mice with whole body autoradiography. Initially a high activity was observed in the brown fat, liver, gall bladder, intestinal contents, kidney and urinary bladder. Pretreatment with DEHP, phenobarbital sodium or 3-methylcholanthrene caused a relative increase of the activity in the brown fat, indicating that induced metabolic conversion of DEHP leads to an increased deposition of radioactivity in brown fat. After administration of DEHP (carbonyl-14C), but not DEHP (2-ethylhexyl-1-14C),marked retention was observed in the skin, cartilage and tendons. The mechanism responsible for the slow accumulation in these connective tissues is not known. In the early embryo a high concentration was observed in the neuroepithelium. This pronounced uptake may be correlated to the DEHP-induced malformations exencephaly and spina bifida observed in mice.

Histopathological and biochemical changes in the liver and testes of desert gerbil, after repeated exposures of Thimet (phorate)

Intraperitoneal administration of Thimet (0.6 mg/kg) on alternate days for a period of 30 days produced various pathological and biochemical changes in the liver and testes of male gerbils. Histology of the liver showed necrosis, enlarged hepatocytes and fatty degeneration. Histological changes seen in the testes were enlarged interstitium, pyknotic spermatogenic cells, reduction in tubular size and atrophy of Leydig cells. The activities of alkaline and acid phosphatases increased in both liver and testes while that of ATPase decreased significantly. The activity of G-6-Pase decreased in liver but increased significantly in testes. Partial recovery was seen 15 days after termination of Thimet treatment. The activities of acid phosphatase, ATPase of liver and alkaline phosphatase, acid phosphatase, and ATPase of testes did not return to their normal values up to 15 days after stopping the injections.

Effect of di-2-ethylhexyl phthalate (DEHP) on glycogen metabolism in rat liver

Effect of di-2-ethylhexyl phthalate (DEHP) on glycogen contents and certain enzymes of carbohydrate metabolism of rat liver was investigated. A significant decrease in glycogen content of unfasted and an increase in fasted animals was observed. Blood glucose tolerance was reduced and the rate of both glycogenesis and glycogenolysis, as judged by measuring glycogen contents after feeding labelled and unlabelled glucose, was also decreased. Activities of glucose-6-phosphate dehydrogenase, phosphorylase and glucose-6-phosphatase were significantly decreased while activities of fructose-1-6-diphosphatase and aldolase remained unaltered. The present results suggest that DEHP affects both glycogenesis and glycogenolysis in rat liver.

Effect of di-(2-ethylhexyl) phthalate on rat liver injured by chronic carbon tetrachloride treatment

The effect of Di-(2-ethylhexyl) phthalate (DEPH), a widely used plasticizer, was studied using histopathological and biochemical parameters on rat liver injured by carbon tetrachloride (CCl4). The mild centrilobular necrosis observed with CCl4 (7.7 mmol/kg subcutaneously and biweekly up to 38 days) and mild congestion and bile duct proliferation produced by DEHP (2.5 mmol/kg intraperitoneally daily for ten days after the day 28 of experiment) were modified into extensive necrosis of the parenchymal cells when the animals received both chemicals. Groups of hepatocytes mostly at the periphery of the lobules also showed coagulative necrosis and some central and portal veins were completely occluded. Alterations in the activity of serum and liver enzymes of the animals receiving both chemicals were not significantly different from those treated with CCl4 alone, except in case of glucose-6-phosphatase (G-6Pase) and SGPT. The characteristic decrease of G-6-Pase and increase of SGPT was less marked. Although the exact mechanism of the chemical interaction between CCl4 and DEHP is not known, the results indicate their combined toxic potentiality.

Effect of Di-(2-ethylhexyl) phthalate (DEHP) on chemical constituents and enzymatic activity of rat liver

Effect of Di(2-ethylhexyl) phthalate (DEHP), was investigated on chemical constituents and activity of certain enzymes of rat liver. A significant increase in liver weight; total and relative to body weight; decrease in total, free and esterified cholesterol; and no change in dry weight, moisture; RNA, DNA, total lipids, phospholipids, pyruvic acid and lactic acid contents was observed in liver of DEHP-treated rats as compared to controls. Activity of 3 mitochondrial enzymes, malic dehydrogenase, cytochrome-c-oxidase and diaphorase were significantly decreased while that of NADH-cytochrome c reductase, RNAase and DNAase remained unaltered upon treatment. The results suggest that DEHP exerts its hepatotoxic effects by interfering with bioenergetics of the cell.

Diethylhexyl phthalate as a factor in blood transfusion and haemodialysis

Di-2-ethylhexyl phthalate (DEHP), the most frequently occurring plasticiser in medical equipment manufactured from polymers of vinyl chloride, forms about 40% w/w of tubes and containers used for storing blood and for haemodialysis. The plasticiser leaches out into liquids with lipid contents, although it is very sparingly soluble in purely aqueous solutions. On infusion of 2-3 1 of stored blood, up to 200 mg DEHP may be transferred to the patient, while much higher quantities may be given during dialysis, which is moreover often repeated frequently over long periods. The acute toxicity of DEHP is very low (greater than 20 g/kg as LD50 in rats), and the ester is rapidly metabolised to products which are excreted in the urine and bile; chronic toxicity from the levels of dosage obtaining is thus very improbable. Carcenogenicity has never been demonstrable in animals, while teratological effects are of a very low order. Serious acute results observed after transfusion of neonates have not been proved to be caused by DEHP, and might be ascribable to accompanying foreign substances. Atheroma in chronic dialysis subjects is still unexplained, but hepatitis probably caused by diethylphthalate from plastic was resolved when apparatus plasticised by DEHP alone was substituted. The benefits of DEHP appear vastly to outweigh any risks. The status of DEHP as environmental contaminant is noted.