Reaction mass of 4,4'-isopropylidenediphenol and phenol

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics

Type of information:

other: comprehensive risk assessment

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Principles of method if other than guideline:

Comprehensive Risk Assessment on Bisphenol A

GLP compliance:

no

See summary and discussion

Executive summary:

Summary of toxicokinetics, metabolism and distribution:

"The limited data available in humans, from a single study, indicate that bisphenol-A does not

accumulate in endometrium or body fat (the only tissues tested). In experimental animals,

toxicokinetic data are available from three oral studies in a single species, the rat and from an in

vitro dermal absorption study, using human skin. These studies provide the basis for a general

understanding of the main features of the toxicokinetic profile. Following oral administration,

absorption from the gastrointestinal tract is rapid and extensive, although it is not possible to

reliably quantify the extent of absorption. Following dermal exposure, the available data suggest

that there is limited absorption, in the region of about 10% of the applied dose. Bisphenol-A was

removed rapidly from the blood, and metabolism data indicate extensive first pass metabolism

following absorption from the gastrointestinal tract. A clear sex difference was observed in the

clearance of parent compound from the blood. In females parent compound was present in the

blood at much later sampling times. There are no data available to explain why this sex

difference was observed. In view of this first pass metabolism, the bioavailability of

unconjugated bisphenol-A is probably limited following oral exposure, at no more than 10-20%

of the administered dose. Limited data are available for the distribution of bisphenol-A following

oral administration: an in vivo DNA adduct study shows that bisphenol-A reaches the liver, an in

vivo micronucleus study suggests that bisphenol-A or a metabolite reaches the bone marrow, a

limited toxicokinetic study suggests that bisphenol-A or a metabolite reaches the testes, and a

repeated dose study in pregnant rats suggests that bisphenol-A reaches the liver of both the dam

and fetus. However, because of first pass metabolism, it is likely that the distribution and

bioavailability of unconjugated bisphenol-A is limited following oral exposure. There is also

evidence of enterohepatic circulation occurring.

The major metabolic pathway in rats involves glucuronide conjugation; limited sulphate

conjugation may also occur. Approximately 10% and 20% of the administered dose was

recovered in the urine as the glucuronide metabolite in males and females, respectively. There

are no data available to explain why this sex difference was observed. Comparative in vitro

studies of metabolism suggest some quantitative differences in the rate of metabolism between

rats, mice and humans. In general, human liver samples show slower rates of glucuronidation

compared with either rats or mice. Estimates of overall liver metabolic capacity suggest that

human liver may have greater metabolic capacity than either rats or mice and that capacity is

lowest in the mouse. However, these estimates are based on limited kinetic data and are therefore

of uncertain reliability. In vitro data in rats also indicate that fetuses do not metabolise bisphenol-

A as extensively as immature and adult animals. In addition, data from cell free systems and in

vivo studies on the interaction of bisphenol-A with DNA, supported by a chemical

photodecomposition study, suggest that limited oxidation of bisphenol-A to bisphenol O-quinone

by cytochrome P450 may occur.

The major route of excretion is via the faeces with the urinary route being of secondary

importance: over 7 days post dosing approximately 80% and 70% of the administered dose was

eliminated in the faeces in males and females, respectively. Elimination was rapid; the majority

of the dose was excreted by 72 hours post dose. A sex difference was also observed in

elimination, with females excreting approximately twice as much radioactivity in the urine

(24-28%) than males (14-16%). Again, there are no data available to explain why this sex

difference was observed. In addition, a strain difference was observed in elimination, with

female F344 rats excreting approximately twice as much radioactivity in the urine than female

CD rats. Data from a number of studies suggest limited excretion of bisphenol-A in the milk.

However, the data do not allow a reliable quantitative determination to be made.

The first pass metabolism and extensive and rapid elimination of bisphenol-A suggest that the

potential for transfer to the foetus and bioaccumulation may be limited. This is supported by data

from toxicokinetic studies in pregnant rats that suggest limited distribution of bisphenol-A to the

foetus, but no evidence for accumulation, and results from a repeated dose study in pregnant rats

which show limited distribution to the fetal liver, with no evidence to indicate accumulation in

the liver, the only organ tested.

There are no data on the toxicokinetics of bisphenol-A following inhalation exposure. However,

on the basis of the observed absolute organ weight changes in a repeat inhalation study and high

partition coefficient, it would be prudent to assume that absorption via the inhalation route can

occur, but the data do not allow a quantitative estimation of absorption to be made. Furthermore,

because first pass metabolism would not take place following exposure by this route, or by the

dermal route, the systemic bioavailability is likely to be substantially greater for these routes than

is associated with the oral route."

Reference 2

Endpoint:

basic toxicokinetics

Type of information:

other: comprehensive risk assessment

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Principles of method if other than guideline:

Comprehensive Updated Risk Assessment on Bisphenol A

GLP compliance:

no

Executive summary:

Impact of new information and summary of toxicokinetics:

"The new information on the toxicokinetics of BPA in humans and in pregnant and nonpregnant

rodents of different ages provides an important contribution to our knowledge of the

kinetic properties of BPA. However, the most significant impact of the new information for

risk assessment purposes arises from the studies in humans. These studies have demonstrated

that at comparable exposure levels the blood concentrations of free BPA in humans are much

lower than those in rodents, indicating that there are important quantitative differences in the

fate of BPA between humans and rodents.

The toxicokinetics of BPA have been well studied in rats both in vivo and in vitro, and have

been investigated to a lesser extent in mice and cynomolgus monkeys. Two studies have

investigated the toxicokinetics and fate of an oral dose of labelled BPA in human volunteers.

Absorption

In the species studied (rats, mice, monkeys, humans), the available evidence suggests that

following oral administration, BPA is rapidly and extensively absorbed from the

gastrointestinal tract. Analysis of plasma AUC values suggests that the extent of absorption

from the GI tract is up to 86% in rats and up to 85% in monkeys. The only relevant human

studies suggest that, on the basis of the recovery of labelled BPA-glucuronide from the urine,

a relatively low dose of BPA (54-88 μg/kg) was completely absorbed after oral dosing.

An in vitro dermal absorption study using human skin found limited absorption of BPA at

millimolar concentrations; the extent of absorption was in the region of 10% of the applied

dose.

There are no data on the toxicokinetics of BPA following inhalation exposure. However, on

the basis of the observed absolute organ weight changes in a repeat inhalation study and the

high partition coefficient, it would be prudent to assume that absorption via the inhalation

route can occur, but the data do not allow a quantitative estimation of absorption to be made.

Furthermore, because first-pass metabolism would not take place following exposure by this

route, or by the dermal route, the systemic bioavailability is likely to be substantially greater

for these routes than is associated with the oral route.

For the purposes of risk characterisation, absorption via the oral and inhalation routes will be

assumed to be 100%; dermal absorption will be taken to be 10%.

Metabolism

The available data indicate that BPA is subject to extensive first-pass metabolism following

absorption from the gastrointestinal tract.

In all species studied, the major metabolic pathway involves conjugation of BPA to BPAglucuronide.

Studies conducted in rats suggest that in neonates the glucuronidation pathway

is more susceptible to saturation than in adults indicating an age-dependent increase in

metabolic capacity. In vitro studies with microsomal preparations also suggest species

differences, with the rank order for the metabolic clearance rate per unit weight of tissue

being mice > rats > humans. When the total clearance rates for the whole liver were

calculated, the rank order was reversed (humans > rats > mice).

In addition to the glucuronidation pathway, in vivo and in vitro studies suggest that in the rat,

BPA may be subject to limited oxididation to bisphenol O-quinone by cytochrome P450, and

also to conjugation to BPA-sulphate and 5-hydroxy-BPA.

A study in pregnant mice given subcutaneous doses of BPA also found that glucuronidation

was the major pathway for the metabolism of BPA, although dehydrated, sulphated and

methoxylated conjugates of BPA were also produced. Some minor metabolites were double

conjugates, such as a double conjugate of BPA with glucuronide and N-acetyl galactosamine

which was found in the intestine, placenta, amniotic fluid and foetal tissue. A study in

cynomolgus monkeys showed that BPA-glucuronide was the major metabolite, although

there was evidence for production of a minor metabolite, possibly BPA-sulphate or 5-

hydroxy-BPA. Studies conducted in humans provide evidence for the glucuronidation of

BPA in man; some studies also found evidence for the sulphation of BPA.

Distribution

Most studies investigating the distribution of BPA measured tissue radioactivity levels after

giving labelled BPA to experimental animals. An oral dosing study in rats found that the

tissue concentrations of BPA-derived-radioactivity were highest in the liver, kidney and

carcass, and lowest in the brain and testes, and there were no large differences between adult

and neonatal animals. A number of studies in rats suggest that BPA metabolites and

especially free BPA have a limited distribution to the embryo/foetal or placental

compartments following oral administration. No selective affinity of either yolk sac/placenta

or embryo/foetus for BPA or BPA metabolites relative to maternal plasma or tissues was

observed in a recent study in rats after oral dosing. However, maternal and embryo/foetal

exposure to free BPA did occur, but systemic levels were found to be low due to extensive

first-pass metabolism.

Regarding the distribution of free, unconjugated BPA to tissues after oral dosing, since free

BPA is removed rapidly from the blood after absorption by first pass metabolism, it has been

suggested that in animals the availability of free BPA to extrahepatic tissues is likely to be

limited following oral exposure. In adult rats it has been estimated that no more than 5-10%

of the administered dose of free BPA is available to the tissues, although this figure may be

higher in neonates. In humans, the systemic availability of free BPA is very low as

enterohepatic recirculation of BPA does not occur.

In summary, there are differences between humans and rodents in the distribution of BPA.

After oral administration, BPA is rapidly metabolised in the gut wall and the liver to BPAglucuronide.

This metabolite is devoid of endocrine activity. In humans, the glucuronide is

released from the liver into the systemic circulation and cleared by urinary excretion. Due to

the rapid biotransformation and excretion (t1/2 = 5 hours) and plasma protein binding, peak

free BPA concentrations in humans after oral exposure that are available for estrogen

receptor binding are very low. In contrast, BPA glucuronide is eliminated in bile in rodents

and undergoes enterohepatic recirculation after cleavage to BPA and glucuronic acid by

glucuronidase in the intestinal tract. The enterohepatic recirculation results in slow excretion

(t1/2 = 15-22 hours) and increased systemic availability of free BPA in rodents.

This conclusion is supported by the observation that in urine of rats dosed orally with BPA, a

part of the dose was excreted as free BPA in urine (1 -4 % of applied dose, whereas BPAglucuronide

in urine accounted for 20-40 % of applied dose). In both of the human studies

and the monkey study free BPA was below the limit of detection in all urine and blood

samples (equivalent to a ratio of free BPA to BPA-glucuronide of < 0.5 %). Since free BPA

found in urine is translocated from blood to urine in the kidney, these observations of higher

free BPA levels in urine of rats compared with primates further support the existence of

species differences in blood levels of free BPA between rodents and humans with higher

AUCs for free BPA in rats.

Excretion

The major route of elimination in the rat is via the faeces. The available data indicate that the

percentage of the administered dose recovered in the faeces is in the range 50% to 83%.

Urinary excretion is of secondary importance in the rat, with 13% to 42% of the administered

dose being recovered in the urine. Over 7 days post-dosing approximately 80% and 70% of

the administered dose was eliminated in the faeces in males and females, respectively.

Elimination was rapid; the majority of the dose was excreted by 72 hours post-dosing. A sex

difference was also observed for urinary elimination, with females excreting approximately

twice as much radioactivity (24-28%) than males (14-16%). A study in female SD rats found

that excretion was not affected by pregnancy at 3 different stages of gestation. Data from a

number of studies suggest limited excretion of BPA in the milk. However, the data do not

allow a reliable quantitative determination to be made.

Following oral administration to rats, a high proportion of the administered dose (45-66%)

was rapidly excreted in the bile in the form of BPA-glucuronide, with the rate of biliary

excretion tending to be higher in males than females. Most of the faecal radioactivity was

found to be in the form of free BPA. Since BPA has a high oral bioavailability in the rat, the

free BPA found in the faeces is more likely to be derived from BPA-glucuronide excreted in

the bile and hydrolysed to free BPA in the gastrointestinal tract rather than representing

unabsorbed BPA which might have passed along the gastrointestinal tract into the faeces

unchanged. Most of the urinary radioactivity was found to be in the form of BPA-glucuronide

(82%) with free BPA and BPA-sulphate making minor contributions (14% and 4%

respectively).

In contrast to the findings in rodents, in cynomolgus monkeys given BPA orally most of the

administered dose (82–85%) was recovered in the urine, with only 2-3% of the dose being

recovered in the faeces. In two studies in human volunteers given a low dose of BPA orally,

the administered dose was completely recovered in the urine as BPA-glucuronide. No free

BPA was detected and no gender differences in the kinetics of BPA-glucuronide in plasma

and urine were reported.

Reference 3

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

(different routes of exposure but only one dose level studied; partly limited documentation, e.g. fasting period; expiration not measured as a possible route of elimination [minor restriction, no main route of elimination])

Objective of study:

toxicokinetics

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Deviations:

yes

Remarks:

[only one (low) dose tested]

GLP compliance:

not specified

Specific details on test material used for the study:

Uniformly 14C-ring labelled phenol (specific activity 100 µCi/µmol)
Radiochemical purity > 98% determined by radiochromatography
Source: Moravek Biochemicals (Brea, CA, USA)

Radiolabelling:

yes

Remarks:

14C-phenol

Species:

rat

Strain:

Fischer 344

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories (Raleigh, NC, USA)
- Age at study initiation: 96 +- 2 days old
- Weight at study initiation: 168 to 189 g
- Fasting period before study: no data
- Housing: after dosing rats were housed in metabolism cages
- Individual metabolism cages: yes
- Diet & water ad libitum
- Acclimation period: The animals were placed in metabolism cages 24 h before dosing


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23-27
- Humidity (%): 40-60
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

other: oral, dermal, intratracheal and intravenous

Details on exposure:

Rats used for dermal exposure were anaesthetized 24 h before treatment and hair on the dorsal skin surface removed with an electric clipper; animals received then a collar (for acclimatization). Animals were dosed with 0.033 mg 14C-phenol/kg bw via oral, dermal, intratracheal or intravenous routes.
- Oral: via gavage, phenol in 1 ml Emulphor/ethanoJ/water (1/1/3)
- i.v.: rats placed in a nose cone bag and administered phenol in 0.2 ml Emulphor/ethanol/water (1/1/3) via the tail vein
- intratracheal: rats anaesthetized with halothane and administered phenol in 0.2 ml Emulphor/ethanol/water (1/1/3), followed by a bolus of air (0.2 ml) to ensure
consistent delivery to the lung
- dermal: rats anaesthetized by ether and phenol applied on a marked skin area of 2.57 cm²; plastic blister glued over the treated skin with cyanoacrylate adhesive

Duration and frequency of treatment / exposure:

single application, duration 72 h

Dose / conc.:

0.033 mg/kg bw/day

No. of animals per sex per dose / concentration:

3-4 females

Details on study design:

After dosing rats returned to the metabolism cages; urine collected at 4, 8, 12, 24, 48 and 72 h and faeces at 24, 48 and 72 h; samples weighed after collection and stored at - 70°C until analysed. Urine (0,1 ml) analysed for radioactivity in the scintillation counter. Faeces air-dried, weighed, pulverized, and 200-300 mg of the pulverized faeces combusted in the oxidizer and also analysed for radioactivity. Aliquots of the 4 and 8-h urine were directly analysed by HPLC methods (metabolites measured).
At 72 h post-exposure, the orally, intravenously, and intratracheally treated animals sacrificed (cardiac puncture) and tissues removed [liver, kidney, trachea, Iung, skin, muscle (vastus lateralis), epididymal fat, stomach, small intestine, large intestine (including caecum) and the contents of the last three tissues]. Tissues weighed, combusted and analysed for radioactivity; carcasses homogenized, combusted and also analysed for radioactivity.

Dermally treated animals anaesthetized and a piece of untreated skin removed (dorsal side); plastic blister cut with a razor blade and the treated skin washed with 3x1 ml of soap/water mixture, followed by 1x 1 ml water and dried; wash samples analysed for radioactivity; the treated skin was then removed from the animal and rat sacrificed (cardiac puncture), tissues collected as described above. Radioactivity detected in the skin washes and treated skin added to the recovered dose; radioactivity in blisters 2.5% (not in recovered dose).

Details on absorption:

Data on excretion profile suggested rapid and extensive absorption after oral, intratracheal and dermal application. Slightly reduced absorption rates were detected after dermal application: ca. 80% of the applied dose

Details on distribution in tissues:

Phenol was distributed throughout the body. At termination (post exposure duration 72 h) only 1-5% of the recovered dose remained in the body by the four routes.

Details on excretion:

The urinary excretion profile of radioactivity was similar in rats receiving phenol by intravenous, oral and intratracheal route; 70-85% of the recovered dose was excreted in urine 4h after administration and urinary elimination was essentially complete by 12 h; after 72 h totally 95% of the applied dose were excreted via urine and only 1-3% were excreted via faeces. After dermal exposure 75% of applied radioactivity was excreted via urine and 3% in faeces within 72 h.

Metabolites identified:

yes

Remarks:

Main metabolite excreted in urine was phenyl sulphate; smaller amounts were excreted as phenyl glucuronide.

Distribution

At termination (post exposure duration 72 h) only 1-5% of the recovered dose remained in the body by the four routes. The highest percentage of the recovered dose was detected in the carcass and the large intestinal contents (see Table below) in the orally, dermally, and intravenously treated animals. The lung of the intratracheally treated animals also had a higher percentage of the recovered dose than the lungs of the other animals. The percentage of recovered dose in other organs (not presented in the Table) was <0.1%.

Excretion

The urinary excretion profile of radioactivity was similar in rats receiving phenol by intravenous, oral and intratracheal route. Urinary excretion of radioactivity was extensive by 4 h post-exposure in the orally, intratracheaIly, and i.v. treated animals: 70-85% of the recovered dose was excreted in urine 4h after administration and urinary elimination was essentially complete by 12 h; after 72 h totally 95% of the applied dose were excreted via urine by intravenous, oral and intratracheal route and only 1-3% were excreted via faeces. Dermal exposure: only 40% of the recovered dose was excreted in urine by 4 h and 70% by 12 h; urinary elimination of radioactivity after dermal exposure was essentially complete by 24 h; after 72 h totally 75% of applied radioactivity was detected in urine and 3% in faeces; washing the dermal site 72 h post-exposure removed 14% of the dose, 2% of the dose were detected in the skin. In comparison to excretion via urine faecal elimination was considerably lower independent on the route of application.

Metabolites

In HPLC analysis (4 and 8 h samples) only two peaks were observed. Percentage of the recovered dose of phenol excreted in urine by rats as phenyl sulphate (peak I), and phenyl glucuronide (peak II) by 8-h post-exposure after administration by the corresponding route is shown in the Table below.

Table 1

Percentage of the recovered dose of phenol excreted in urine by rat as phenyl sulphate

(peak I) and phenyl glucuronide (peak II) 8 h after administration of 0.033 mg/kg bw
14C-labelled phenol by various routes

Exposure route	phenyl sulphate	phenyl glucuronide
Oral	63.4 +- 2.3	26.8 +- 2.7
Dermal	48.4 +- 3.3	16.2 +- 3.4
Intratracheal	68.7 +- 2.6	19.4 +- 2·1
i.v.	72.6 +- 5.0	14.3 +- 0.9
mean +- SD of 3-4 animals

 

Table 2

Percentage of the recovered dose in the tissues of rats 72 h after application by various routes

Tissue	Oral	Intratracheal	Dermal	i.v.
Contents large intestine	0.14	2.8	0.28	0.21
Lung	0.001	0.13	0.002	0.006
Untreated skin	0.072	0.13	0.21	0.11
Carcass	0.75	1.5	0.98	2.2
mean +- SD of 3-4 animals; other organs < 0.1%

Conclusions:

The oral, dermal, intratracheal, and i.v. exposure to phenol results in its rapid absorption, conjugation and elimination via urine.

Executive summary:

The study is comparable to OECD Guideline 417 with acceptable restrictions (different routes of exposure but only one dose level studied; partly limited documentation, e.g. fasting period; expiration not measured [minor restriction, no main route of elimination]).

Female F344 rats (n=3 -4 per group) received 0.03 mg/kg bw 14C-labelled phenol via oral, dermal, intratracheal, or i.v. administration. Radioactivity in urine and feaces was analysed after sampling in metabolism cages; the animals were sacrificed 72 h after application and radioactivity in organs, carcass and washings determined. Rapid and complete absorption of the administered radioactivity was found after oral and intratracheal exposure: 70-85% of the recovered dose was excreted in urine 4h after administration and urinary elimination was essentially complete by 12 h, after 72 h totally 95% of the applied dose were excreted via urine and only 1 -3% were excreted via faeces. Slightly reduced absorption rates were detected after dermal application: total amount of applied radioactivity excreted via urine was 75%, 3% were measured in faeces, 14% in skin washing at 72 h, 2% in the treated skin, and 2.5% in plastic blisters. The total dermal absorption rate was ca. 80% of the applied dose. Independent on the route of exposure low amounts (1 -5% of the recovered dose) retained in the rat 72 h after application. Phenol was distributed throughout the body. At a dose level of 0.033 mg/kg bw phenol was metabolized in rats to the sulphate (main metabolite) and glucuronide conjugates after absorption from the four routes of exposure.

Reference 4

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

metabolism

Principles of method if other than guideline:

14C-phenol has been administered to humans and 18 animal species and the urine examined for metabolites by radiochromatogram scanning.

GLP compliance:

no

Radiolabelling:

yes

Remarks:

U-14C]Phenol (266/µCi/mg)

Strain:

other: human, Rhesus monkey; Squirrel monkey; Capuchin, Ferret, cat, dog, Rat, mouse, Jerboa, gerbil, golden hamster, lemming

Sex:

male/female

Details on test animals or test system and environmental conditions:

3 male volunteers
Primate: Rhesus monkey (2 f); Squirrel monkey (3 f); Capuchin (1 f)
Carnivores: Ferret (3 f), cat (3 f), dog (1 f, 1 m)
Rodents: Rat (3 f; Wistar), mouse (3x10 f; ICI), Jerboa (3 f), gerbil (2 f & 1 m), golden hamster (2 f), lemming (3 f), guinea-pig (2 f)
Other: Pig (3 f), hedgehog (2 m), fruitbat (2 f), rabbit (3 f, New Zealand White), chicken (3 f)

Route of administration:

oral: unspecified

Vehicle:

water

Details on exposure:

14C-phenol in water administered by gavage except in the case of the primates, carnivores and pigs, when it was given incorporated in the food or drink (no further details; but this application suggested also a bolus effect comparable to gavage).

Duration and frequency of treatment / exposure:

Single oral application

Remarks:

0.01 mg/kg bw in human volunteers and 20-50 mg/kg bw in mammalian species plus chicken

Details on study design:

Urine wos collected for 24 h and chromatographed (see below). Radiochromatograms prepared and areas corresponding to peaks cut out and analysed by scintillation counting.

Details on dosing and sampling:

Collection of urine: animals placed in suitable metabolism cages; urine collected daily in receptacles containing a few ml of saturated aq. HgCl2 solution to prevent bacterial breakdown of conjugates (excreta of chickens collected on galvanized metal trays). These excreta extracted with three separate portions (40 ml) of water to remove the water soluble conjugates of phenol; the three extracts pooled and made up to 150 ml with water. This solution was then treated in the same way as the urines of other animals for the estimation of 14C and for paper chromatography.
For analysis of phenol and its metabolites paper chromatography ( Whatman No. 1 paper) and the descending technique were used. For radiochromatogram scanning the urine (0.1-0.5 ml) was placed as band on strips (5 cm wide) of Whatman No. 1 paper and developed with different solvents. The paper was scanned in a Packard radiochromatogram scanner. Thin-layer chromatography was carried out with fluorescent silica gel.
Radiochemical techniques: 14C was determined using a Packard Tri-Carb Scintillation Spectrometer.

Details on absorption:

In humans 90% (range 85-98) of the orally applied dose was excreted via the 24 h-urine indicating nearly complete oral absorption. Similar results were obtained with rats, lower rates were reported for other species.

Metabolites identified:

yes

Details on metabolites:

The metabolites phenylsulphate, phenylglucuronide, hydroquinone (quinol) monosulphate and hydroquinone monoglucuronide were detected. In humans 90% of an oral dose was excreted in 24 h mainly as phenylsulphate (77% of 24 h excretion) and phenylglucuronide (16%) with very small amounts of hydroquinone sulphate and glucuronide. A similar excretion pattern was found in the rat. Significant differences in metabolic pathways and quantities of metabolites in urine were detected in other species.

Metabolites

Species receiving l4C-phenol showed four peaks which corresponded to phenylsulphate, phenylglucuronide, hydroquinone (quinol) monosulphate and hydroquinone monoglucuronide. Details are presented in the Table below. Catechol conjugates did not appear to be formed in sufficient quantities to be detected on any of the radiochromatograms ( <1%) under the conditions of these experiments and at the dose level of phenol. The results demonstrated that humans can conjugate phenol (0.01 mg/kg bw; lower dose than in animals) with sulphate and glucuronic acid and oxidize it to hydroquinone. In three men 90% of an oral dose was excreted in 24 h mainly as phenylsulphate (77% of 24 h excretion) and phenylglucuronide (16%) with very small amounts of hydroquinone sulphate and glucuronide. The above four metabolites of phenol were also detected in the urine of the following species: rat, mouse, jerboa, gerbil, hamster, lemming, and guinea pig. Three metabolites were excreted by some species, namely, phenol and hydroquinone glucuronides and phenylsulphate by the squirrel monkey and capuchin monkey, and phenol and hydroquinone sulphates and phenylglucuronide by the ferret, dog, hedgehog and rabbit. Only 2 metabolites were excreted by the rhesus monkey, fruit bat and hen (phenylsulphate and phenylglucuronide) and by the cat (phenylsulphate and hydroquinone sulphate). One metabolite (phenylglucuronide) only was excreted by the pig.

Urinary metabolites of 14C-phenol in various species

Species (number and sex)	Dose in mg/kg bw	% of applied 14C excreted in urine	%14C excreted in 24 h found as
			Phenyl sulfate	Hydroquinone sulfate	Phenyl glucuronide	Hydroquinone glucuronide
Humans (3 m)	0.01	90 (85-98)	77(69-90)	1 (n=1)	16(4-23)	tr
Primates
Rhesus monkey ( 2 f)	50	37, 49	60, 70	-	40, 30	-
Squirrel monkey (3 f)	25	31 (18-52)	7 (2-17)	-	68 (55-86)	25 (11-36)
Capuchin (1 f)	25	73	14	-	65	21
Carnivores
Ferret (3 f)	25	51 (49-54)	28 (19-34)	30 (21-34)	40 (22-52)	-
Cat (3 f)	25	59 (52-61)	87 (86-89)	13 (11-14)	-	-
Dog (1 f, 1 m)	25	53, 62	33, 68	43, 20	24, 12	-
Rodents
Rat (3 f)	25	95 (91-100)	54 (44-65)	1 (0-2)	42 (35-55)	2 (0-5)
Mouse· (3 x 10 f)	25	66 (64-68)	46 (40-51)	5 (3-8)	35 (33-37)	15 (12-17)
Jerboa (3 f)	25	47 (28-65)	61 (51-71)	12 (9-15)	26 (20-33)	1 (0-4)
Gerbil (2 f & 1 m)	25	55 (45-68)	42 (22-53)	19 (13-23)	35 (30-49)	1 (0-4)
Hamster (2 f)	25	73, 78	27, 24	1, tr	44, 41	28, 27
Lemming (3 f)	25	40 (15-67)	35 (18-51)	10 (8-12)	39 (28-48)	15 (10-23)
Guinea pig (2 f)	25	64, 64	13, 22	tr, tr	82, 73	5, 5
Other species
Pig (3 f)	21	51 (18-72)	-	-	100	-
Hedgehog (2 m)	20	34, 43	63, 86	17, 4	20, 10	-
Fruitbat (2 f)	25	50, 58	9, 11	-	91, 89	-
Rabbit (3 f)	25	48 (35-60)	45 (41-48)	9 (7-13)	46 (39-52)	-
Chicken (3 f)	25	57 (53-60)	78 (57-91)	-	22 (9-43)	-

Legend: where 3 or more animals were used averages are given with ranges in parentheses. Individual values are given where only one or two animals were used. tr.: traces < 1%; -: no peaks detected

Conclusions:

Significant species differences in metabolism of phenol has been shown. Humans and rats showed similar metabolic pathways and quantities of metabolites in urine. Comparing 18 different mammalian species including humans highest absorption rates were found in humans and rats after oral application. The rat is likely a good surrogate for human metabolism of phenol.

Executive summary:

 

The study meets scientific standards with acceptable restrictions (partly limited documentation; low number of animals per studied species).

Three volunteers ingested a single dose of 0.01 mg 14C-labelled phenol/kg bw and 17 mammalian species plus chicken received orally the labelled phenol at dose levels between 20 and 50 mg/kg bw. Metabolites were determined in 24h-urine by radiochromatogram scanning. Four peaks which corresponded to phenylsulphate, phenylglucuronide, hydroquinone (quinol) monosulphate and hydroquinone monoglucuronide were detected. Catechol conjugates did not appear to be formed in sufficient quantities. In three men 90% of an oral dose was excreted in 24 h mainly as phenylsulphate (77% of 24 h excretion) and phenylglucuronide (16%) with very small amounts of hydroquinone sulphate and glucuronide. The above four metabolites of phenol were also detected in the urine of the following species: rat, mouse, jerboa, gerbil, hamster, lemming, and guinea pig. Three metabolites were excreted by some species, namely, phenol and quinol glucuronides and phenylsulphate by the squirrel monkey and capuchin monkey, and phenol and quinol sulphates and phenylglucuronide by the ferret, dog, hedgehog and rabbit. Only 2 metabolites were excreted by the rhesus monkey, fruit bat and hen (phenylsulphate and phenylglucuronide) and by the cat (phenylsulphate and quinol sulphate). One metabolite (phenylglucuronide) only was excreted by the pig.

In humans 90% (range 85 -98) of the applied dose was excreted via the 24 h-urine indicating nearly complete oral absorption. Similar results were obtained with rats. Furthermore, the amount of specified metabolites excreted are very similar in rats and humans.

Conclusion: Significant species differences in metabolism of phenol has been shown. Humans and rats showed similar metabolic pathways and quantities of metabolites in urine. Comparing 18 different mammalian species including humans highest absorption rates were found in humans and rats after oral application. The rat is likely a good surrogate for human metabolism of phenol.

 

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

The reaction mass consists of two constituents and several impurities, the toxicokinetics of which have been assessed separately. All of the constituents are assumed to be absorbed to large extent upon oral exposure, extensively metabolised via conjugation and quickly excreted. Accordingly, bioaccumulation is not expected to occur. Due to low vapour pressures and moderate to high log Kow, inhalation absorption plays a minor role for all constituents except phenol, which has a low Kow and will be readily available if inhaled.

For considerations on the analogue approach used please refer to the justification for read-across attached to Iuclid section 13.

Due to the extensive datasets available for BPA and phenol, the constituents of the target substance Reaction mass of phenol and 4,4’-isopropylidenediphenol, we refrained from including all available data on both substances into this dataset, but used the key and weight of evidence information of phenol and BPA to document the hazard profile of the reaction mass. The assessments of phenol and BPA by the respective consortia is based on the EU risk assessment reports and has been adopted for this reaction mass.