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Description of key information

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion
Dose descriptor:
NOAEL
32 mg/kg bw/day

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Dose descriptor:
NOAEC
500 mg/m³

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Dose descriptor:
NOAEL
500 mg/kg bw/day

Additional information

The primary findings in the repeated dose studies are effects observed in the liver and kidney in two separate two-year chronic toxicity studies.

The key study for which the NOAEL of 88 mg/kg bw/day is derived for effects observed from repeated dose administration, is the well documented study reported by Moore (1998a, Covance). Based on dose spacing, this study has been given preference for regulatory purposes. The study published by Lington et al. identified a NOAEL of 15 mg/kg bw/day for males and 18 mg/kg bw/day with a LOAEL of 152 mg/kg bw/day for females based on liver and kidney weight increases. Therefore the 88 mg/kg bw/day is regarded to be a better representation of the NOAEL. However, as outlined previously the results of these studies were pooled based on the endpoint and experimental suitability to derive a conservative BMDL of 32 mg/kg/day. The studies are examined below and the rational for the appropriateness of the pooled analysis can be found in the toxicological information summary. 

In this study (Moore, 1998) DINP was administered daily to rats in the diet for at least 104 weeks at dietary concentrations of 0, 500, 1500, 6000, and 12000 ppm. Rats in the recovery group were administered DINP at a dietary concentration of 12000 ppm for 78 weeks, followed by a 26-week recovery period during which they were administered the basal diet alone.

 

Administration of DINP for at least 104 weeks at levels of 6000 and 12000 ppm resulted in compound- related histomorphologic alterations in the liver and kidneys. Liver changes consisting of increased cytoplasmic eosinophilia and hepatocellular enlargement were observed only in the animals of the 12000 ppm group. An increased incidence of hepatocellular neoplasia was observed in rats of both sexes of the 12000 ppm group, but was not present in the high-dose recovery group.

 

Kidney changes at 104 weeks consisted of mineralization of the renal papilla and increased pigment in tubule cells at 6000 and 12000 ppm. Increased mineralization was noted in the renal papilla of the males of the 6000, 12000 ppm and recovery groups but was not present in the females.

 

Mononuclear cell leukemia occurred with increased frequency in rats of the 6000, 12000 ppm and recovery groups, and renal tubule cell carcinomas were noted in two and four males of the 12000 ppm and recovery groups. No evidence for sustained cell proliferation associated with the peroxisome proliferation induced by DINP was observed.

 

Based on the test results, the NOAEL for systemic toxicity was found to be 1500 ppm (88.3 and 108.6 mg/kg bw/d for males and females, respectively).

 

In the second two-year chronic study, DINP was administered to Fischer 344 rats (110/sex) at dietary concentrations of 0, 0.03, 0.3, and 0.6% (w/w) for 2 years (Lington et al., 1997). The mean daily intakes over the 2 years were 15, 152, and 307 mg/kg/day for male rats and 18, 184 and 375 mg/kg/day for female rats, corresponding to the 0.03, 0.3 and 0.6% dose levels, respectively. 

 

High dose males exhibited a statistically significant, dose-related decrease in body weight beginning at 12 months of treatment and persisting until termination. This was not noted for the females. Males and females from the mid and high-dose groups exhibited a statistically significant, dose related increase in relative kidney and liver weights throughout most of the treatment period; the absolute liver and kidney weights demonstrated a similar trend. Statistically significant changes in organ weights consisted of dose-related increased absolute and relative spleen weights of the high-dose males, increased relative spleen weights of the high-dose females and a relative increased adrenal weight in both sexes as well as relative increased testes weights in high-dose males. 

 

At 18 and 24 months, non-neoplastic lesions were observed in the liver and kidney of high-dose rats. Ultrastructural examination of liver specimens from representative rats of each sex from the four groups did not reveal any treatment-related peroxisome proliferation. An increased incidence of spongiosis hepatis, a degenerative change, was noted in males receiving 0.3 and 0.6% DINP in the diet, and of hepatocellular enlargement in both sexes at the high dose. Focal necrosis was increased in both sexes from 0.3%, but was only significant in males of the high-dose group. Hepatic pathology was significantly increased only in males from 0.3% and at 0.6% in females. 

 

Statistically significant increased incidence of mononuclear cell leukemia (MNCL), a spontaneous, age-related tumor in F344 rats, was observed in the mid and high-dose groups (both sexes) and with a significantly increasing trend over time. The MNCL was associated with a variety of hepatic alterations (non-neoplastic lesions), however scientific consensus indicates a low human relevance to the observation of MNCL in Fischer 344 rats. 

 

Chronic progressive nephropathy, a normal aging lesion in rodents, was seen in most of the rats, and not related to treatment of severity grade. Renal neoplasms were seen in 3 mid-dose and 2 high-dose male rats. The renal tumors were not statistically elevated when compared to controls and there was no evidence of any treatment related pre-neoplastic renal lesions. The underlying mechanism of the kidney tumors observed with the high-dose in male rats was determined to be an α2u-globulin mechanism of tumorigenesis which is not regarded as relevant to humans (EPA, IARC). 

 

The effects observed in the liver in both of these studies, besides some minor and probably adaptive effects, are indicative of peroxisomal proliferation and include increased PCoA, liver weights, and liver hypertrophy and are not relevant for humans. Indeed, it has been shown that these effects are mediated through the peroxisome proliferation-activated receptor alpha (PPARα) and the levels of PPARα are higher in rodents than humans and the phthalate monoesters are more avid receptor agonists in rats than in humans.

 

It is accepted that peroxisome proliferation is specific to rodents. Peroxisome proliferators exhibit their pleiotropic effects due to activation of PPARα. PPARα is expressed only at low level in humans, explaining the absence of a significant response in humans to peroxisome proliferators. In studies conducted in non-human primates, the data obtained following oral administration of DINP for up to 13 weeks provides no evidence that the compound caused induction of peroxisome proliferation (Hall et al, 1999; Pugh et al., 2000). The NOAEL of 500 mg/kg/d from the marmoset and cynomolgus monkey studies clearly indicates that non-human primates and by read-across humans, are far less sensitive than rodents to peroxisome proliferation and its relative liver effects.

 

For the observed kidney effects, a NOAEL of 88 mg/kg/d is also derived from the Moore (1998) and based on increased kidney weights in both sexes. Effects on the rat kidneys were described in the majority of the rat studies as slight to moderate changes in the kidney weight, sometimes with modifications of physiological parameters often more marked in males (increases of blood urea and/or blood creatinine concentrations, proteins in urine and decrease of the specific gravity). Histologically, there was an increase in frequency/severity of chronic progressive nephropathy at low doses, specifically in males. Histological features are consistent with the specific male rat nephropathy irrelevant to humans, namely alpha 2u globulin nephropathy. It is assumed that the accumulation of protein droplets from continued chemical treatment results in progressive histological changes in male rats: papillary mineralization and atypical hyperplasia, leading to renal adenomas or carcinomas on prolonged exposure. Exposure to DINP results in a dose-dependent alpha 2u-globulin accumulation in male rat kidneys (ExxonMobil, 1986) and is likely the mechanism for kidney tumors seen only in male rats administered high dietary levels (1.2%) of DINP (Moore, 1998; Caldwell et al.,1999, Schoonhoven et al.2001).

 

In mice, progressive nephropathy is also observed at higher doses: tubular nephrosis at 20,000 ppm (5,700 mg/kg/d) in a 13-week study and granular pitted/rough kidneys in female mice at 8,000 ppm (1,900 mg/kg/d) in a chronic/carcinogenicity study (Moore, 1998b). Progressive renal nephrosis is an agre-related lesion in rodents. In dogs, renal effects were observed at the high dose of 2% (2,000 mg/kg/d), and consisted of hypertrophy of kidney tubular epithelial cells in few animals in the 13-week study (ExxonMobil, 1971). No kidney effects were reported in monkeys up to 2,500 mg/kg/d in a 13-week study (Huntington life Sciences, 1998).

 

Concerning effects on reproductive organs, in the 2-year study with Fischer 344 rats (Lington et at, 1997) there was a statistically significant increase in relative testis weights at the high dose of 0.6% (307 mg/kg/d in males) associated with a slight, but not statistically significant, increase (13%) of absolute testis weight. In some sub-acute and sub-chronic studies with Fischer 344 rats, relative testis weights were statistically significantly increased with or without concurrent increase of absolute testis weights and decrease of body weights at quite high doses (about 1,500 mg/kg/d in one week study, about 700 mg/kg/d in 13-week studies).

 

In mice, a NOAEL of 1,500 ppm (276 mg/kg/d) can be derived from a 104-week study (Moore, 1998b) based on testicular weight decrease observed from 4,000 ppm (742 mg/kg/d) and is used for the risk characterization. In addition, in a 4-week and a 13-week repeated-dose mouse studies, slight decreases of testis weight were observed accompanied by the presence of abnormal / immature sperm forms in the epididymis at doses of 6,500 mg/kg/d and 5,700 mg/kg/d, respectively (25,000 and 20,000 ppm). In those mouse studies (4-week and 13-week) effects were noted in uterus (hypoplasia and absence of endometrial glands) and in ovaries (absence of corpora lutea suggesting an arrest of ovulation) at doses of 20,000 ppm and 25,000 ppm.

 

It should be noted that in the 13-week study in monkeys, no changes were reported in testis weight and testis microscopic examination. In addition, there were no treatment-related changes in estradiol and testosterone concentrations assessed (Hall et al, 1999).

 

In a 6-week dermal exposure study in beagle dogs, the highest dose tested only produced a localized response of slight to moderate erythema. No systemic toxicity was observed (ExxonMobil, 1969). 

 

In conclusion, the most sensitive endpoints, which are also not relevant to humans, are for effects on the liver and kidneys observed in two well-documented studies. A NOAEL of 88 mg/kg/d is determined in rats regarding results found in a chronic / carcinogenic study (Moore, 1998a). Refer to section 5.11.2 selection of the DNEL(s) or other hazard conclusion for critical health effects for a complete explaination of he justification on endpoint selection for the derivation of the DNEL.

 

Summary Table of Results.

Test Species  Protocol  NOAEL  LOAEL  Reference
One-week prechronic oral study  rat Fischer 344  0 -2% in diet    2% (1700 mg/kg/d): increased kidney and liver weights, macroscopic liver changes, and decreased cholesterol and triglycerides.  ExxonMobil (1982a) 
 13 week study rat Wistar 0, 3000, 10000, 30000 ppm in diet    3000 ppm (152 -200 mg/kg/d): decreased triglyceride levels, decreased alimentary peripheral fat, and deposits in hepatocytes   BASF (1987a)
 13 week study rat Fischer 344 1, 2500, 5000, 10000, 20000 ppm in diet     2500 ppm (176 -218 mg/kg/d): increased liver and kidney weight  Hazleton (1991a)
 2 year study  rat Fischer 344 0, 0.03, 0.3, 0.6 % in diet   0.03% (15 -18 mg/kg/d) 0.3% (152 -184 mg/kg/d): increased liver and kidney weights, increased incidnece of non-neoplastic changes.  ExxonMobil (1986a) Lington et al (1997)
 2 year study rat Fischer 344  0, 500, 1500, 6000, 12000 ppm in diet 1500 ppm (88 -103 mg/kg/d)  6000 ppm (358 -422 mg/kg/d): increased kidney weights in both sexes, histopathological findings in males, liver toxicity (increased ALT, AST values, liver weights), and liver histopathological findings.  Moore (1998a) 
 4 week  mouse B6C3F1 0, 3000, 6000, 12000, 25000 ppm in diet   3000 ppm (635 mg/kg/d) 6000 ppm (1300 mg/kg/d) decreased absolute and relative testes weight, increased liver weight.  Hazleton (1991b) 
 13 week  mouse B6C3F1 0, 1500, 4000, 10000, 20000 ppm in diet  1500 ppm (365 mg/kg/d)  4000 ppm (972 mg/kg/d) enlarged liver, increased absolute and relative liver weight.  Hazleton (1992) 
2 year study  mouse B6C3F1  0, 500, 1500, 4000, 8000 ppm in diet  500 ppm (female: 112 mg/kg/d) 1500 ppm (male: 276 mg/kg/d)  1500 ppm (275-335 mg/kg) increased kidney and liver weights. 4000 ppm (742 mg/kg/d) decreased absolute and relative (to brain weight) testis weight.  Moore (1998b) 
 13 week study dog Beagle  0.125, 0.5, 2% in diet    0.125% (37 mg/kg): increased AST in females, increased liver weight.  ExxonMobil (1971a) 
 2 week study  adule male cynomolgus monkeys 0, 500 mg/kg/d gavage 500 mg/kg/d  No adverse effects noted  Pugh et al. (2000) 
13 week study  marmoset monkeys  0, 100, 500, 2500 mg/kg/d gavage 500 mg/kg/d   2500 mg/kg/d: minor changes: decreased body weight, decreased body weight gain.  Hall et al. (1999)
 6 week study rabbit New Zealand  0, 0.5, 2.5 ml/kg dermal  0.5 ml/kg (500 mg/kg)  2.5 ml/kg/d: slight or moderate erythema and slight desquamation.  ExxonMobil (1969) 

Inhalation:

Due to its extremely low vapour pressure, DINP vapour phase concentrations may not attain high levels, even at the high temperatures used in some industrial conditions (e.g. processing, mixing, calendering). At 20°C, DINP has a vapour pressure of 6.10-5 Pa (best estimated value) and a calculated satured vapour concentration of 10 μg/m3. If vapours are inhaled up to a temperature of around 35°C (where maximum vapour pressure would be around 2.10-4 Pa and prolonged inhalation unlikely), the satured vapour concentration is ca. 115 μg.m-3.

Occupational exposure to vapour will actually be far below these values.

At high temperatures and mechanical pressures,aerosol formation may be observed with DINP.

Due to similar physico-chemical mechanisms of aerosol formation, similar aerosol concentrations are likely to be observed with heavy phthalates like DIDP in similar conditions of use. Therefore, the NOAEC (500 mg/m-3) of the repeat dose inhalation study with rats using DIDP will be used for risk characterization.


Repeated dose toxicity: via oral route - systemic effects (target organ) digestive: liver; urogenital: kidneys

Repeated dose toxicity: dermal - systemic effects (target organ) other: skin

Justification for classification or non-classification

No classification for repeated dose toxicity is indicated according to the general classification and labeling requirements for dangerous substances and preparations (Directive 67-548-EEC) or the classification, labeling, and packaging (CLP) regulation (EC) No 1272/2008.