Studies on the toxicity of phthalates via ingestion.

Some recent publications have revealed the presence of phthalates in rather unexpected locations (1-4). Mayer (3) reported that di-n-butyl phthalate and di-2-ethylhexyl phthalate had measurable effects on the Daphnia, an accepted subject for studying the aquatic food chain in the environment. The ubiquity of phthalates has been well documented. Their presence in stored blood samples and in some randomly sampled humans is reason for concern, even though no directly related harmful effect has been clearly demonstrated to date. Numerous nontechnical writings displayed serious concern about the subject of phthalates in the environment. Some of these writings showed signs of emotional reaction, inappropriate generalizations and an unawareness of the content of technical studies in the literature concerning the subject. Nearly one billion pounds of phthalates are consumed in the U.S.A. per year. They are a critically necessary component of plastics, coatings and other industries that are an integral part of our life. In order to encourage mature perspective concerning the presence and effects of phthalates in our environment, one must retain perspective concerning the relative hazard or safety of various substances as a


Introduction
Some recent publications have revealed the presence of phthalates in rather unexpected locations (1)(2)(3)(4). Mayer (3) reported that di-n-butyl phthalate and di-2-ethylhexyl phthalate had measurable effects on the Daphnia, an accepted subject for studying the aquatic food chain in the environment. The ubiquity of phthalates has been well documented. Their presence in stored blood samples and in some randomly sampled humans is reason for concern, even though no directly related harmful effect has been clearly demonstrated to date. Numerous nontechnical writings displayed serious concern about the subject of phthalates in the environment. Some of these writings showed signs of emotional reaction, inappropriate generalizations and an unawareness of the content of technical studies in the literature concerning the subject. Nearly one billion pounds of phthalates are consumed in the U.S.A. per year. They are a critically necessary component of plastics, coatings and other industries that are an integral part of our life.
In order to encourage mature perspective concerning the presence and effects of phthalates in our environment, one must retain perspective concerning the relative hazard or safety of various substances as a *Research and Development Department, Union Carbide Corporation, Tarrytown Technical Center, Tarrytown, New York 10591.
function of specific conditions involved. One accepted means for judging toxic characteristics of substances is to observe the effects due to oral ingestion. This report reviews published and unpublished studies on the oral ingestion of phthalates. The phthalates are compared to other known substances in terms of LD50 and acceptable daily intake (ADI) values.

Discussion
The literature reports ingestion studies on phthalates ranging from dimethyl (CH3) up to ditridecyl (C13H27) and includes coesters of mixed alkyl alcohols as well as aryl alkyl phthalates. Dibutyl phthalates and di-2ethylhexyl phthalate were appropriately the most widely studied, since they are the most significant members of the phthalate family from the viewpoint of volume consumed.
Test animals covered a wide range, with the rat being the most common species. Other variables included the method of administration, i.e., stomach tube, capsules, added to diet, etc. Single-dose, acute-toxicity studies were generally employed for purposes of the statistically calculated LD50, the dosage required to cause fatality to 50% of the test species. Prolonged ingestion studies generally involved daily dosages well below the LD50 values. Di-2-ethylhexyl phthalate (commonly referred to as DOP) was administered to various species up to 2 years (5, 6). Harris et al. (6) pointed out that the natural lifetime of the control rats not receiving test sub-stances precluded extending the exposure period past 2 years. Lefaux (7) reports that extensive feeding tests were conducted on rats with dibutyl phthalate at Villejuif Cancer Institute. Five generations of rats were fed daily diets containing 100 mg of DBP per kilogram body weight; 300 mg/kg and 500 mg/kg daily doses were fed to three generations of rats. Both male and female rats showed normal weight gains and reproductive patterns. No signs of poisoning or carcinogenic effects were found. It was concluded that dibutyl phthalate is harmless. Similarly, diets containing 500 mg of DOP/ kg of body weight were fed to four generations of rats. Normal reproduction and no anomalies were found during parturition or nursing.
Tables 1-4 summarize the technical information contained in the literature on the ingestion of phthalates and related materials.
While lethal dosages were, of course, attained, all of the writers reached the general conclusion that the phthalates have a very low order of toxicity. No carcinogenic characteristics were found by any of the investigators. Generally, no adverse histological or pathological effects of significance were found. Most investigators observed a slight reduction in rate of weight gain, and a slight increase in liver and kidney weights with specimens receiving the larger doses over prolonged periods. However, Harris et al. (6) reported none of these shortcomings for rats receiving DOP at 0.5% of the daily diet for 2 yr. This daily dose corresponded to a dose per body weight value ranging from 1.5 g/kg/day to 0.33 g/kg/day over the 2-yr feeding period. In the same work, a dog was fed 5.0 g/kg/day over a 14-week period. The only effect on the dog was a slight loss in rate of weight gain. The work of Harris et al. (6,24) constituted the largest daily doses administered to test animals over extended periods.
Three cases of human ingestion, single dose, have been reported. Shaffer et al. (14) reported that an adult male intentionally took 10 g of di-2-ethylhexyl phthalate and experienced mild diarrhea; another adult male showed no effects whatsoever after having taken 5 g. Lefaux (7) reports that a young adult male mistakenly ingested about 10 g. of dibutyl phthalate. He was hospitalized on the next day, after having experienced nausea and vertigo. Signs of keratitis and toxic nephritis (excess albumen in the urine, together with red and white corpuscles) were observed. He was treated and released after 2 weeks observation with no after-effects. If a typical weight of the cited three subjects of 70 kg (154 lb) is assumed, it may be calculated that the 5 and 10 g dosages are equivalent to 72 and 144 mg/kg body weight, respectively. Hence, if a typical adult were to ingest a single dose of 10 g of phthalate plasticizer, it would be about 1/100 to 1/1000 of the single-dose LD50 levels reported in Table 1.
No investigator proposes that the quantitative values defined on test animals can be related to man. Uncontrolled dosages and exposures further complicate the problem of defining the safe use of substances. For the sake of comparison, therefore, Table 5 lists the LD50, in rats, of some commonly encountered substances. LD50 values of typical common household chemicals that are considered safe are as follows: vinegar (acetic acid), 3.5-5.2 g/kg; table salt (sodium chloride), 4.5 g/kg; rubbing alcohol (isopropanol, not denatured), 5.8-10.7 g/kg; drinking alcohol (ethanol, not denatured), 11.3-21.3 g/kg; soapy water (20%), > 16 g/kg. All LD50 values are calculated to reflect the dosage of the 100% pure substance causing fatality to 50% of the specimens (9). The ranges shown reflect findings that when administered in a more dilute condition, the animal has a reduced tolerance for total intake of the pure substance. The relative safety of the phthalates is recognized when the above substances are compared to the data in Table 1. Other than dimethyl phthalate, all of the phthalates tested for oral ingestion are included within the range of 8 g/kg to > 64 g/kg, LD50. Dimethyl phthalate is frequently applied as an insecticide and may be expected to be unique in this class of materials. Dibutyl phthalate is in the same gen-Environmental Health Perspectives  (16) o-Phthalic acid Rat 7.9 ml/kg (14) eral toxicity range of the household substances cited above, but all of the higher molecular weight phthalates are significantly less toxic than these substances. Because of the very low order of toxicity for these higher phthalates, no pattern is apparent as a function of variations in chemical structure.
Other diesters that are similar to the phthalates were found to have very low order of toxicity as shown in Table 1. Typical plasticizer alcohols and phthalic acid, however, appear to be more toxic than the phthalates. As shown in Table 1, these materials all have LD50 of less than 20 g/kg. The Joint FAO/WHO Expert Committee on Food Additives (32) strongly recommends that food additives be restricted to the minimum levels required to accomplish a given technical objective. It would, of course, be most desirable to have no foreign substance present in foods, but it must be recognized that such substances do enter foods by both direct and indirect means. Acceptable daily intake zones-commonly referred to as ADI-have been determined for various substances, and are expressed as milligrams per kilogram of man body weight (32). The ADI is determined by the equation: where N denotes the maximum "no effect" level of substance based on most sensitive test with most sensitive test species, in mg/kg/day. (This usually implies daily dosages of duration . 90 days), F is a safety factor to convert from animal species to man. FAO/WHO recommends (33) a factor of 100; commonly, a factor of 500 is used if N is based on 90-day feeding test data and a factor of 100 is used if N is based on 2-year feeding tests. The typical daily intake may be calculated for a given food additive and compared to the ADI. Table 6 takes the liberty of calculating ADI values for phthalates, wherever the cited reference provided the pertinent information. The values range from 0.04(7) to 8.0 mg/kg. From this it may be estimated that a typical adult of 60 kg weight could survive daily doses of phthalates ranging from 2.4 mg to 480 mg (0.48 g). For further comparison, Table 7 lists ADI values of selected chemical compounds commonly applied as food additives. The unconditional acceptable limits of these chemicals have ADI values of the same order of magnitude that has been calculated for the phthalates.

Summary and Conclusions
Extensive testing has been reported concerning the effects of ingestion of phthalates. The literature contairns studies including phthalates ranging from dimethyl to ditridecyl. Acute toxicity tests define rather high LD50 values, indicating a very low order of toxicity as compared to many common chemical substances. The acceptable daily intake (ADI) values calculated for phthalates from the works cited are in the same order of magnitude as some chemicals that are approved for use as direct food additives. Three instances of human ingestion were reported. In one of the cases (dibutyl), some toxic symptoms were reported, but the person recovered with no after-effects; the other cases (DOP) showed no toxic effects.
The various works did reach levels of administration causing toxic effects, including fatalities of some of the test species. Nearly all of the investigators were willing to conclude that the phthalates constitute a chemical family of very low order of toxicity, as measured by ingestion methods. Dimethyl phthalate, the lowest molecular weight member of the family, is mildly more toxic than all of the other phthalates, but is not considered lethal. The extensive feeding studies that have been reported appear to verify that the phthalates have a very low order of toxicity when administered by oral ingestion. Mortality: no effect due to DOP Body weight: no effect due to DOP Food intake: no effect for first year; but 0.5% group ate only 75% of control group during second year 0.4%, Carpenter's rats t 0.2 No effect g/kg/day = 200 mg/kg 0.1% in rats for 2 years Organ weights: no difference, except for slight increase of liver and kidney with 0.5% diet Pathology: no effect (24) 2 Dogs 5 g/kg/day, stomach tube 0.1 g/kg/day in diet 14 wk

wk
Mild toxic changes at 14 weeks, 0.1 g/kg/ day gave no effect at 14 weeks, but it is pointed out that Carpenter (5) had found 0.09 ml/kg/day to give toxic changes in liver and kidney after 1 year feeding. Not harmful in industry or food wraps.
Environmental Health Perspectives (23) 15 wk 34 wk Weights of all organs and bone marrow measured; only liver and kidney weights showed slight gains at 3 and 6 months. No clear-cut evidence of toxic effects, but 6-month specimens indicated that changes in bladder of 20% of species may be due to diet.
Control group had 44/46 fatality; 2 yr is maximum period useful for rats AWeight: all same; all organs: no change.
Liver and kidney definitely not > controls. Lungs, brain, stomach, heart, spleen, testes, also weighed Pathological: test animals similar to controls (aging changes) No effect: slight loss of weight gain. Hematology: normal; Histological: normal; Urinalyses: no effect (on female only). At 10 g/kg, the dog refused to eat for 2 days. a Test started at 2 months age of rats. bEqual to 0.05 0.08 g/kg/day. C Equal to 0.3 0.4 g/kg/day. dReports DOP much less toxic than DCP (22). January 1973 (22) Mice Rats.  cWt-% of daily diet.  aFor method, see Smyth et al. (16) bAll values calculated on basis of 100% purity, irrespective of administration purity. c 70.7 ml/kg wine equals 11.3 ml/kg ethanol content.
Environmental Health Perspectives   (34). bThe first part of the overall acceptable daily intake zone is termed unconditional, and this represents levels which can be safely used without further expert supervision and advice. The second part is termed conditional and represents levels of use that can be safely employed but at which it is thought desirable that some degree of expert supervision and advice should be readily availabfe. C As sum of benzoic acid and sodium and potassium benzoate (calculated as benzoic acid). dAs sum of methyl, ethyl, and propyl esters of p-hydroxybenzoic acid. eAs sum of butylated hydroxytoluene and butylated hydroxyanisole.