 5.
What health effects can DIDP and DINP
cause in laboratory animals?
DIDP
"Effects assessment
Toxicokinetics, metabolism
and distribution
The data available on
toxicokinetic suggest that, via gastro-intestinal
tract (GIT), absorption of DIDP
decreases as dose increases (56% at the
low dose of 0.1 mg/kg, 46% at the mid
dose of 11.2 mg/kg and 17% at the high
dose of 1,000 mg/kg) and seems to be of
saturable mechanism; when dose increases,
an increasing amount of unabsorbed compound
is eliminated. Via the dermal route, the
absorption is very low in rats. DIDP showed
a very slow excretion, reflecting a slow
dermal uptake process. The maximum percentage
of absorption may be estimated 4% of applied
dose in 7 days by analogy with DINP.
In humans, skin absorption is still lower
than in rat as indicated by in vitro comparative
studies. Inhaled
DIDP aerosol
seems readily absorbed, thus a 75 % bioavailability
seems realistic. In tissues,
DIDP
is mainly recovered in GIT, liver, kidneys,
by the oral or inhalation route, whereas
following dermal exposure, muscle and
adipose tissues contain most of the dose
remaining in the body. Only metabolites
of DIDP (the oxidative monoester derivative
and phthalic
acid) are excreted in urine. In feces,
the monoester oxidative derivative, MIDP
(monoisodecyl phthalate) as well as DIDP
were detected. DIDP is rapidly eliminated
and not accumulated in tissues. By the
oral and inhalation routes, excretion
is shared between urine and faeces. By
dermal exposure, only faecal elimination
was indicated. In addition, results from
a two-generation study suggest a possible
transfer of DIDP through the milk when
dams are exposed by the oral route.
Acute toxicity
Upon single exposure,
DIDP
has a low acute toxicity
by all routes of administration.
Irritation
Human or animal data suggest no potential
irritant effects on skin, eyes or respiratory
system. Sensitisation
There is no evidence for
skin or respiratory sensitisation.
Repeated dose toxicity
The liver was identified
as a target organ as a result of oral
repeated exposure. In rodents, increases
in liver weight were accompanied by biochemical
evidence of peroxisomal proliferation;
thus, a NOAEL
of 60 mg/kg/d was identified in rats from
a standard 90-day study. Findings in dogs
were qualitatively consistent (increases
in liver weight and swollen and vacuolated
hepatocytes); a NOAEL of 15 mg/kg/d was
derived from a 13-week oral dog study,
in spite of the large limitations of this
study.
Increases in kidney weights
are also observed in repeated dose toxicity
tests but in a non- consistent way and
with no concurrent histopathological changes.
Renal damages are only observed in a two-generation
study (about 12 weeks) from 100 - 200
mg/kg/d, but only in male rats; a specific
male rat effect is generally assumed.
In an inhalation
study, there was no systemic effect observed
and toxicity
was limited to local inflammatory changes
in the lung.
Mutagenicity
DIDP
is not mutagenic in vitro in bacterial
mutation assays (with and without metabolic
activation) and is negative in a mouse
lymphoma assay. It is not clastogenic
in a mouse micronucleus assay in vivo.
This indicates that DIDP is a non-genotoxic
agent. Carcinogenicity
Regarding carcinogenicity,
cell transformation tests were conducted
on DIDP. One positive result obtained
is in accordance with those obtained with
well-known peroxisome proliferators. No
carcinogenicity long-term study is available
for DIDP but an increase in incidence
of hepatocellular tumours
in rats related to peroxisome proliferation
might be anticipated, in regard with the
increased incidence in tumour liver cells
observed with DEHP
and DINP
in carcinogenicity studies. Indeed, it
is now well-accepted that peroxisome proliferation
is specific to rodents. It has been established
that peroxisome proliferators exhibit
their pleiotropic effects due to activation
of PPARα (peroxisome proliferator-activated
receptor α) and that PPARα
is expressed only at low level in humans,
explaining the absence of significant
response in humans to the action of peroxisome
proliferators. Thus, there is no concern
for a potential carcinogenic effect in
humans through such a mechanism.
Toxicity for reproduction
Regarding toxicity
for reproduction, in 42-44 day year old
(pubertal) or adult rats there is no indication
of organ reproductive effects evidenced
by histological observation in repeated
dose toxicity studies and a two-generation
study. In this two-generation study, a
decrease in mean percent normal sperm
was observed but of low incidence and
only in P1 generation. In pups (F1, F2
and in the cross fostering satellite group)
decreases in testes weight and cryptorchidism
in F2 high-dose offspring were observed,
likely due to the low body weight, since
no histopathological damages were observed
in adult testes. There were no changes
in reproductive indices. From those assays,
no adverse effects on fertility
may be anticipated.
Regarding developmental
effects, treatment of dams from gd 6-15
did not cause structural malformations
but consistently demonstrated skeletal
variations (increased fœtal cervical
and lumbar ribs) at 1,000 mg/kg/d concurrently
with slight signs of maternal toxicity
and lead to a NOAEL
of 500 mg/kg/d; in a two-generation rat
study, body weight decrease was observed
in offspring partly related to lactation
at the highest dose of 0.8% and leads
to a NOAEL of 0.4% (253 to 761 mg/kg/d
seeing that received doses are widely
dependent on the period considered).
Developmental toxicity
was observed consistently in the two-generation
studies, where decrease in survival indices
leads to a NOAEL of 0.06% (33 mg/kg/d
DIDP).
A prenatal exposure study
in mice conducted at 9,650 mg/kg/d does
not affect pregnancy outcome, however,
as this test was drawn for screening purpose,
it is insufficient to conclude to an absence
of effect.
DIDP
is devoid of estrogenic activity in vitro,
it shows no ability of binding to rodent
or human estrogen receptors or to induce
estrogen receptors-mediated gene expression.
In vivo assays demonstrated that DIDP
does not increase uterine wet
weight or does not give rise to vaginal
epithelial cell cornification. In a two-generation
study, developmental landmarks (anogenital
distance, nipple retention and preputial
separation) are not impaired; this suggests
a lack of anti-androgenic activities."
Source
& © : ECB
 "2003
Risk Assessment Report (RAR 041) on
Di-"isodecyl" Phthalate (DIDP),
Summary of the Report,
chapter 4: Human Health
For more information,
see the full ECB Risk Assessment Report:
Chapter
4: Human Health
DINP
"Effects assessment
Toxicokinetics, metabolism
and distribution
The data available on
toxicokinetic suggest that, via gastro-intestinal
tract (GIT), absorption of DINP
decreases as dose increases (49% at the
low dose of 50 mg/kg and 39% at the high
dose of 500 mg/kg eliminated in urine);
in addition, absorption of the substance
seems to be a saturable mechanism. Dermal
absorption is slow in rats. The maximum
percentage of the applied substance being
absorbed in 7 days is less than 4%. In
humans skin absorption is still lower
than in rat as indicated by in vitro comparative
studies. Via inhalation,
a bioavailability of 75% may be assumed
by analogy with DIDP.
In tissues,
DINP is mainly recovered in GIT, liver
and kidney by oral route whereas following
dermal exposure, liver, muscle and adipose
tissues contain most of the dose remaining
in the body. DINP metabolites
were excreted in urine and to a lesser
extent in feces. DINP was de-esterified
to the monoester which was further metabolised
by side-chain oxidation of the ester group
or by hydrolysis
to phthalic
acid. Repeated dosing caused no accumulation
of DINP and/or its metabolites in blood
and tissue, but resulted in increased
formation and elimination of the monoester-oxidation
products. DINP is rapidly eliminated.
By the oral and dermal routes, excretion
is shared between urine and feces. By
dermal exposure, biliary excretion is
shown.
Acute toxicity
Upon single exposure,
DINP
has a low acute toxicity
by all routes of administration.
Irritation
Human or animal data suggest
no potential irritant effects on skin,
eyes or respiratory system.
Repeated dose toxicity
The liver is a target
for chronic
toxicity
and a NOAEL
of 88 mg/kg/d was assumed for liver effects
based on hepatic biochemical changes (increased
aspartate-aminotransferase, AST and alanine-aminotransferase,
ALT) and on increases of liver weight
with histopathological findings. Repeated-dose
studies performed to assess the peroxisomal
proliferation potential of DINP,
reveal biochemical evidence of peroxisome
proliferation in rodents. In contrast,
there was no evidence of peroxisome proliferation
in marmosets or in cynomolgus monkeys;
in humans as well, there is no significant
response to peroxisome proliferators.
For kidney effects, a
NOAEL of 88 mg/kg/d was determined, based
on increased kidney weights. Histologically,
there was an increase in frequency/severity
of chronic
progressive nephropathy at quite low doses,
but specifically in males. Histological
features are consistent with the specific
male rat nephropathy irrelevant to humans,
namely alpha 2u globulin nephropathy.
It was demonstrated, by immunohistochemical
techniques, that exposure to DINP
results in a dose dependant alpha 2u globulin
accumulation in male rat kidneys and is
likely the mechanism for kidney tumours
seen only in male rats administered high
dietary levels of DINP. In mice, there
was also progressive nephropathy observed
at very high doses.
Mutagenicity
DINP
is not mutagenic in vitro in bacterial
mutation assays or mammalian gene mutation
assay (with and without metabolic activation)
and is not clastogenic in one cytogenetic
assay in vitro on CHO cells and in one
in vivo assay on bone marrow cell of Fisher
344 rats. This suggests that DINP is not
genotoxic.
Carcinogenicity
In chronic/carcinogenicity
studies, DINP
was found to induce significant excess
of liver neoplasia in rats and mice after
oral administration. This is consistent
with a peroxisome proliferation mode of
action for hepatic tumour
induction specific in rodent. It has been
established that peroxisome proliferators
exhibit their pleiotropic effects due
to activation of PPARα (peroxisome
proliferator-activated receptor α)
and that PPARα is expressed only
at low level in humans, explaining the
absence of significant response to the
action of peroxisome proliferators, thus,
there is no concern for a potential carcinogenic
effect in humans.
Regarding MNCL (mononuclear
cell leukemia), a clearly increased incidence
is observed in the two studies conducted
with Fisher rats. However, MNCL, a common
neoplasm in the Fischer 344 rats, was
categorised by IARC as “an unclassified
leukemia with no known human counterpart”
and substances which increase MNCL frequency
as “not classifiable as to carcinogenicity
in humans”. Pertaining to kidney
tumours,
the species and sex-specific alpha 2u
globulin mechanism likely responsible
for kidney tumours seen in male rats is
not considered as relevant to humans.
Toxicity for reproduction
Regarding fertility,
no adverse effects are anticipated in
adult rats on reproductive organs, in
repeated dose toxicity
and in one-generation studies. In mice,
a very high dose (5,770 mg/kg/d) leads
to decrease in testicular weight with
abnormal/immature sperm forms and uterus/ovaries
atrophy in the 13-week study. In the 104-week
chronic
study, a NOAEL
of 1,500 ppm (276 mg/kg/d) can be assumed
for testicular effects, based on decrease
in testicular weight (relative and absolute)
observed from 742 mg/kg/d. Testicular
lesions were not observed in a 13-week
gavage study in adult marmosets well as
in a 2-week gavage study in prepubertal
cynomolgus monkeys. In a two-generation
study, no changes in reproductive indices
are observed.
In the developmental studies,
visceral (dilated renal pelvis and hydroureter)
and skeletal variations (increases in
lumbar and cervical ribs) were significantly
increased on a litter basis at 1,000 mg/kg/d,
leading to a NOAEL
of 500 mg/kg/d. In addition, a decrease
of mean offspring body weight was observed
following parental administration of DINP
in the one and two-generation studies
from the lowest dose tested (LOAEL
of 159 mg/kg/d). In a two-generation study,
parental toxicity
was limited to lower mean body weight
and hepatic changes.
In regard with offspring
survival in rats, a decrease of life birth
and survival indices was observed in a
one-generation range-finding study at
doses higher than 1,000 mg/kg/d.
DINP
is devoid of estrogenic activity in
vitro, it does not show ability of
binding to rodent or human estrogen receptors
or to induce estrogen receptors-mediated
gene expression. In vivo assays
demonstrated that DINP does not increase
uterine wet
weight or does not give rise to vaginal
epithelial cell cornification. However,
a recent study in rats (perinatal exposure)
indicated that infants male displayed
female like areolas/nipples and that incidence
of reproductive malformation was slightly
but significantly increased (7.7% versus
91% with DEHP)."
Source
& © : ECB
"2003
Risk Assessment Report (RAR 046) on
Di-"isononyl" Phthalate (DINP), Summary
of the Report,
chapter 4: Human Health
For more information,
see the full ECB Risk Assessment Report:
Chapter
4: Human Health
|
