Committee for Risk Assessment
RAC
Opinionproposing harmonised classification and labellingat EU level ofbis(α,α-dimethylbenzyl) peroxide
EC Number: 201-279-3
CAS Number: 80-43-3
CLH-O-0000001412-86-217/F
Adopted
8 June 2018

Annankatu 18, P.O. Box 400, FI-00121 Helsinki, Finland | Tel. +358 9 686180 | Fax +358 9 68618210 | echa.europa.eu[04.01-ML-014.02]

8 June 2018
CLH-O-0000001412-86-217/F

OPINION OF THE COMMITTEE FOR RISK ASSESSMENT ON
A DOSSIER PROPOSING HARMONISED CLASSIFICATION
AND LABELLING AT EU LEVELIn accordance with Article 37 (4) of Regulation (EC) No 1272/2008, the Classification,
Labelling and Packaging (CLP) Regulation, the Committee for Risk Assessment (RAC) has
adopted an opinion on the proposal for harmonised classification and labelling (CLH) of:
Chemical name:bis(α,α-dimethylbenzyl) peroxide

EC Number:

201-279-3

CAS Number:

80-43-3

The proposal was submitted by Norway and received by RAC on 28 April 2017.
In this opinion, all classification and labelling elements are given in accordance with the
CLP Regulation.

PROCESS FOR ADOPTION OF THE OPINION
Norway has submitted a CLH dossier containing a proposal together with the justification
and background information documented in a CLH report. The CLH report was madepublicly available in accordance with the requirements of the CLP Regulation at
http://echa.europa.eu/harmonised-classification-and-labelling-consultation/
on 20 June 2017. Concerned parties and Member State Competent Authorities (MSCA)
were invited to submit comments and contributions by 4 August 2017.

ADOPTION OF THE OPINION OF RAC
Rapporteur, appointed by RAC:

Peter Hammer Sørensen

The opinion takes into account the comments provided by MSCAs and concerned parties inaccordance with Article 37(4) of the CLP Regulation and the comments received arecompiled in Annex 2.
The RAC opinion on the proposed harmonised classification and labelling was adopted on
8 June 2018 by consensus.

12Classification and labelling in accordance with the CLP Regulation (Regulation (EC) 1272/2008)
Index No

Current
Annex VI
entry

617-00600-X

Dossier
submittersproposal

617-00600-X

RAC opinion

617-00600-X

ResultingAnnex VI
entry ifagreed byCOM

617-00600-X

International
Chemical
Identification

EC No

CAS Nobis(α,αdimethylbenzyl)
peroxide201279-3

80-43-3bis(α,αdimethylbenzyl)
peroxide201279-3

80-43-3bis(α,αdimethylbenzyl)
peroxide201279-3bis(α,αdimethylbenzyl)
peroxide201279-3

80-43-3

80-43-3Classification
Hazard Class andCategory Code(s)Hazardstatement
Code(s)Labelling
Pictogram,
Signal Word
Code(s)

Hazardstatement
Code(s)Org. Perox. FSkin Irrit. 2
Eye Irrit. 2
Aquatic Chronic 2
Add
Repr. 2

H242
H315
H319
H411
Add
H361d

GHS02
GHS09
GHS07
Wng
Add
GHS08

H242
H315
H319
H411
Add
H361d

RemoveSkin Irrit. 2
Eye Irrit. 2
Add
Repr. 1B

Remove
H315
H319
Add
H360D

RemoveGHS07

Remove
H315
H319
Add
H360D

RetainSkin Irrit. 2
Eye Irrit. 2
Org. Perox. F
Repr. 1B
Skin Irrit. 2
Eye Irrit. 2
Aquatic Chronic 2

Retain
H315
H319
H242
H360D
H315
H319
H411

Retain
GHS07

Add
GHS08

GHS02
GHS07
GHS08
GHS09
Dgr

Suppl.
Hazardstatement
Code(s)Specific Conc.
Limits, Mfactors and
ATE

Notes

Retain
H315
H319
H242
H360D
H315
H319
H411

3

GROUNDS FOR ADOPTION OF THE OPINION
RAC general comment
The current proposal for harmonised classification for bis(α,α-dimethylbenzyl) peroxide isintended to cover new data on developmental toxicity that has become available. However, inthe process of evaluating the substance it was discovered that the current harmonisedclassifications for skin and eye irritation were not supported by the available data in the current
REACH registration dossier. These classifications date back to before the CLP Regulation cameinto force and the grounds at that time, for giving this substance a harmonised classification as
an irritant, have not been found. Although skin and eye irritation are not prioritised endpoints,
while proposing a classification for reproduction toxicity, the dossier submitter (DS) proposed toremove the former classifications at the same time.

HUMAN HEALTH HAZARD EVALUATIONRAC evaluation of skin corrosion/irritation
Summary of the Dossier Submitter’s proposal
The DS included a study on New Zealand White rabbits to assess the skin irritation potential ofbis(α,α-dimethylbenzyl) peroxide. The study was mainly performed according to GLP and OECD
TG 404. There was however one deviation from the guideline: the laboratory had not used avehicle with the test substance, which was a crystalline powder. It may be that the substance
did not show its true irritating potential when applied in dry form, as in the OECD TG 404, it isstated that the smallest amount of liquid necessary in order to ensure good skin contact should
be used.
The effects of the test substance on the skin were very slight, grade one for both erythema andoedema, and were seen in only two out of three rabbits. The mean scores at 24, 48 and 72 hours
were below one for both effects and in all three rabbits and were reversed at 72 hours, see table
9 on the background document. As the study results were below the classification criteria for skinirritation, the DS proposed to remove the existing classification.

Comments received during public consultation
Four MSCAs supported the DS proposal to remove the existing classification. Two MSCAs notedthat no vehicle was used in the study and that the purpose of the vehicle was to optimise thecontact between the solid substance and the skin. These two MSCAs considered there was areasonable possibility of an increased skin reaction if the substance had been applied with avehicle, and thus they questioned whether this study should be considered sufficiently robust to
declassify the substance. One of these MSCAs disagreed with the DS proposal to declassify
because in their opinion the study suffered from a serious deficiency.

Assessment and comparison with the classification criteria
RAC agrees that the skin irritation study was deficient since the laboratory did not use a vehicle
in administrating the test substance, which is lipophilic with a Log K OW of 5.6 and was

4

administered in a crystalline state, raising doubts as to whether without a vehicle, it was madesufficiently bioavailable in the test.
In addition RAC noted that according to ECHA Guidance on the Application of the CLP Criteria(which cross refers to ECHA Guidance on Information Requirements & Chemical Safety
Assessment, Chapter R7, section R.7.2.6.2 “Testing and assessment strategy for skincorrosion/irritation”), if a substance is a peroxide it can be considered as a skin irritant Cat. 2 1.
Given the uncertainty of the available test data, the mentioned ‘evidence to the contrary’ islacking.
RAC recommended not to remove the current classification based on lack of proper data and inconclusion, agreed in line with the guidance to retain the current classification of Skin Irrit.
2; H315.

RAC evaluation of serious eye damage/irritation
Summary of the Dossier Submitter’s proposal
The DS included a study on Himalayan rabbits to assess the eye irritation potential of bis(α,αdimethylbenzyl) peroxide. The study was conducted in 2010 according to OECD TG 405. There
were some deviations however, such as a lack of information on the presence of impurities. There
was also a lack of information on the application of anaesthesia, which is a requirement in themost recent version of the guideline, but was to be applied on a case-by-case basis in an earlier
version used at the time of the study. The laboratory used Himalayan rabbits, which were notalbino rabbits and according to the guideline a justification must be given if the albino rabbit is
not used. Such a justification was not given in the study report.
There was a small degree of opacity seen in the cornea of animal no. 3 at 24 and 48 hours. Grade
1 opacity was described as "scattered or diffuse areas of opacity (other than slight dulling of
normal lustre), details of iris clearly visible". There was also some redness of the conjunctivae inall three animals at 1 hour and in two animals at 24 hours. Grade 1 redness was described as"some blood vessels hyperaemic (injected)". A fluorescein test was performed at 24 hours afteradministration and revealed corneal staining in animal no. 3 (up to 25 % of the surface). At 72
hours all effects were reversed in all three animals. The untreated eye that served as the control
did not show any pathological changes. No other effects were reported in the report, see table
12 in the background document.
As the values from the study results were below those in the classification criteria for eye irritation,
the DS proposed to remove the existing classification.

Comments received during public consultation
Four MSCAs supported the DS proposal to remove the existing classification.

1 Figure R.7.2-2 line 1b Consider classifying as: corrosive (Skin Corrosive Cat. 1B) if the substance is ahydroperoxide, or irritating (Skin Irritant Cat. 2) if the substance is a peroxide OR Provide evidence for thecontrary.

5

Assessment and comparison with the classification criteria
RAC agrees with the DS that the test substance had only a slight eye irritant effect in rabbits andthe effects were reversible at 72 hours after administration. However, considering the lipophilicity
and the very low water solubility, the effects seen could be related to a physical/mechanicalirritation of the particles in the eye. To adequately observe the irritation effects of this lipophilic
substance, an appropriate vehicle should have been used.
In conclusion RAC agreed to retain the current classification as Eye Irrit. 2; H319.

RAC evaluation of reproductive toxicity
Summary of the Dossier Submitter’s proposal
The DS did not include studies on adverse effects on sexual function and fertility.
One developmental toxicity study in Wistar rats was performed according to OECD TG 414. No
information on the GLP status was included in the CLH dossier. The study findings are
summarised in the table below.
Method,Test substance,
guideline,
dose levels
deviations if
duration ofany, species,
exposurestrain, sex,
no/groupDevelopmental Bis(α,αtoxicity study
dimethylbenzyl)(OECD
peroxide
guideline 414)
Purity: 99.0%
Rats: 24
sperm-positive Oral: gavage
Wistarrats/treatment 0, 50, 150, 450
groupmg/kg bw/day
Reliability
score: 1

Results

Maternal and developmental NOAEL: 150 mg/kg
bw/dayReference

Study report
788.410.4505,

Maternal and developmental LOAEL: 450 mg/kg bw/day Toxi-Coop Zrt.
(2014) (notMaternal toxicity:
published)
Mortality:
Control, 50 and 150 mg/kg bw/day dose groups: No
mortality

vehicle: sunflower
450 mg/kg bw/day dose group: one dam died onoilgestation day 20 (the day of scheduled necropsy)
Exposure: Days
5-19 of gestation Clinical symptoms:(daily)control group: alopecia in one female
50 mg/kg bw/day dose group: no clinical symptoms.
150 mg/kg bw/day dose group: salivation (4/21
dams).
450 mg/kg bw/day dose group: No clinical signs in
7/17 dams. Salivation (8/17 dams); piloerection (3/17
dams); alopecia (3/17); reduced activity, vaginal
bleeding, pale, cold, hypo tonicity and red colouration
around red eye (deceased dam).
Necropsy findings:
0, 50 and 150 mg/kg bw/day dose groups: no
necropsy findings.
450 mg/kg bw/day dose group: No necropsy findingsin 11/17 dams. In the remaining dams: enlarged
adrenals (4/17 dams); blood in uterus (3/17); enlarged
spleen (2/17); uterus filled up with blood (1/17);
stomach distended filled up with darker content (1/17);
pale liver and pale kidneys (1/17). See confidential

6

Method,
guideline,
deviations if
any, species,
strain, sex,
no/group

Test substance,
dose levels
duration of
exposure

Results

Referenceannex for individual data.
Food consumption:
50 mg/kg bw/day dose group: a statisticallysignificant temporary decrease in food intake wasrecorded.
150 and 450 mg/kg bw/day dose groups: astatistically significant dose related decrease in the foodconsumption was recorded in the whole treatment
period.
Body weight:
50 mg/kg bw/day dose group: a transient decrease inbody weight gain.
150 and 450 mg/kg bw/day dose groups: lower
mean body weight, lower corrected body weight,
transient weight loss day 5-8 of gestation, andmarkedly reduced body weight gain and corrected bodyweight were observed. See annex I and confidential
annex for more details.
All treatment groups had positive weight gain at theend of treatment period compared with the startweight.
Foetal toxicity:
50 and 150 mg/kg bw/day dose groups: nostatistically significant effect on the intrauterine
development of embryos and foetuses.
450 mg/kg bw/day dose group: statistically significant
increase in the post-implantation loss (17%, 15/17
litters) compared to in the control group (7 %, 14/23
litters). By consequence, the number of viable foetusesin the 450 mg/kg bw/day dose group (9.0/litter) was
statistically significantly lower than in the control group(11.6/litter).
Furthermore, a statistically significant increase in total
intrauterine mortality was observed. The total
intrauterine mortality in the high dose group (65 cases)
was 29 % of the number of examined corpora lutea,
compared to 14% in the control group.
Foetal weight:
50 and 150 mg/kg bw/day dose groups: nostatistically significant decrease in the pup’s bodyweight compared with control group.
450 mg/kg bw/day dose group: increase inpercentage of foetuses with decreased body weight(11/17 litters; 31 cases) compared with control group(5/11; 6 cases).
External malformations:
50 and 150 mg/kg bw/day dose groups: no externalmalformations were observed.
450 mg/kg bw/day dose group: mal-rotated fore- andhind limbs in six foetuses (5/17 litters; 6 cases;
statistically significant) and hydrops fetalis in one

7

Method,
guideline,
deviations if
any, species,
strain, sex,
no/group

Test substance,
dose levels
duration of
exposure

Results

Reference

foetus.
Visceral variations: Hydroureter (bilateral) in 4 pups
50 mg/kg bw/day dose group: hydroureter (bilateral)in two cases.
150 mg/kg bw/day dose group: no visceral variations.
450 mg/kg bw/day dose group: hydroureter(bilateral) in two cases (in two litters).
Visceral malformations: four malformations in threepups
control group: one pup with an absent brain tissue
and one with situs intersus totalis
50 mg/kg bw/day dose group: no visceralmalformations.
150 mg/kg bw/day dose group: one pup with absent
lung lobes and with situs intersus totalis.
450 mg/kg bw/day dose group: no visceralmalformations.
Skeletal variations:
50 mg/kg bw/day dose group: incomplete ossified
sternum (2 cases; 2/20 litters), incomplete ossification
marked of skull bones (2 cases; 2/20 litters), one caseof not ossified supraoccipital, thoracic or lumbar centra(3 cases; 3/20 litters) and 7 cases (3/20 litters) ofwavy ribs.
150 mg/kg bw/day dose group: incomplete ossified
sternum (8 cases; 5/21 litters), one case incomplete
ossification (more than three bones), 4 cases (1/21
litters) of incomplete ossification marked of skull bones,
one case of not ossified supraoccipital, thoracic or
lumbar centra (2 cases; 2/21 litters) and 16 cases(7/21 litters) of wavy ribs.
450 mg/kg bw/day dose group: incomplete
ossification of skull bones (10 cases; 8/17 litters),
incomplete ossified sternum (10 cases; 9/17 litters),
metacarpal/metatarsal (4 cases; 4/17 litters), thoracic
or lumbar centra (4 cases; 4/17 litters) and wavy (24cases; 11/17 litters) and marked wavy ribs (6 cases;
5/17 litters).
Skeletal malformations:
50 mg/kg bw/day dose group: no skeletal
malformations.
150 mg/kg bw/day dose group: short and/or bent
scapula (3 cases; 2/21 litters).
450 mg/kg bw/day dose group: short and/or bent
scapula (12 cases, 9/17 litters), clavicular (2 cases;
2/17 litters), humerus (9 cases; 7/17 litters), radius (8cases; 7/11 litters) and ulna (5 cases; 5/17 litters).

8One developmental toxicity study in rats had been performed with exposure to bis(α,αdimethylbenzyl) peroxide, and the maternal and foetal toxicity findings are presented in the table
above.
The table below shows the groups and number of animals/foetuses included and analysed in the
study.
Dose

0

50

150

450

24

24

24

23 (1 mortality
on day 20)

Number of females withpregnant uteri, necropsied

23

20

21

17

Number of foetuses
necropsied for skeletal
examination

133

109

114

76

(mg/kg bw/day)Number of females

Animals treated with bis(α,α-dimethylbenzyl) peroxide exhibited increased signs of toxicity fromthe low dose (transient decrease in food consumption and body weight gain) to the high dose,
where adverse clinical symptoms some necropsy findings, weight loss, markedly reduced bodyweight gain, and reduced food consumption were observed. These effects were marked in damsof the highest treatment group (450 mg/kg bw/day) and this dose is considered a LOAEL formaternal effects.
Mortality, clinical symptoms, necropsy
One dam died in the 450 mg/kg bw/day dose group on gestation day 20 (the day of scheduled
necropsy) with the following adverse clinical symptoms: vaginal bleeding, piloerection, paleness,coldness and hypotonicity. However, there were no pathological examination data of the foetuses
from the deceased dam: usually examination of foetuses from deceased dams is conducted when
the death occurs on the day of scheduled necropsy. The death was considered by the performing
laboratory to be treatment related, although it was stated in the study report that the dam "dieddue to unclear reason". No mortality was observed in the 50 and 150 mg/kg bw/day dose groups.
No clinical observations were noted for the dams in the 50 mg/kg bw/day dose group. The only
clinical sign in the 150 mg/kg bw/day dose group was salivation, seen in four (4/21) dams.
Salivation was seen in eight dams (8/17 dams) in the 450 mg/kg bw/day dose group. Salivation
was judged to be treatment-related however, it was not considered an adverse effect. In the 450
mg/kg bw/day dose group, 1/17 dams had vaginal bleeding, 3/17 had piloerection and 1/17 was
hypotonic. These were considered adverse clinical signs and an effect of the test item.
Necropsy findings in the high dose group were: 4/17 dams had enlarged adrenals and bloody
uterine content (blood in the uterus (2/17 dams), blood in uterine horn (1/17 dam) and uterus
filled with blood (1/17 dam)). One dam had an enlarged spleen. These findings were considered
to be treatment related. There were no necropsy findings in the remaining 11/17 dams examinedin the high dose group.
Overall, a majority of the examined dams did not have adverse clinical symptoms, and only 4/17
dams (23%) had both adverse clinical signs and necropsy findings, while 5/17 dams (29%) had
no adverse clinical signs and no necropsy findings. Another 5 dams (29%) had salivation and/or
alopecia as only clinical signs and no necropsy findings.

9

Food consumption
Evaluation of food consumption data showed that there was a test substance treatment related
decrease in the average food intake in the 150 and 450 mg/kg bw/day dose groups and atemporary decrease in the average food intake in the 50 mg/kg bw/day dose group. The foodconsumption reduction in the 150 mg/kg bw/day dose group, although statistically significant,
was judged not to be adverse and was considered biologically non-relevant since the lower foodconsumption only resulted in a small reduction of body weight (less than 10% lower than thecontrol group). When the individual food consumption data for the dams in the high dose groupwere compared with the data for observed clinical signs and its adversity, there was no clear
correlation between lower food intake and adverse clinical symptoms.
Body weight
Evaluation of the body weight parameters showed a dose-dependent decrease in all recorded
body weight parameters, for the 150 and 450 mg/kg bw/day dose groups. The decrease in the
body weight parameters were considered to be related to the test item. Further, a transient
reduced body weight gain was noticed in the 50 mg/kg bw/day dose group and it was considered
to be a non-adverse effect. In the 150 mg/kg bw/day group the body weight reduction at theend of treatment was less than 10% lower than the control group, however body weight gain
was reduced by 15%. The dams of the high dose group had a body weight at the end of treatmentthat was 17% lower than the control dams, however the body weight gain was about half of thegain seen in the control group. At the end of the treatment period, all dams in all treatmentgroups gained some weight compared with the start weight.
The body weight parameters of the dams with adverse clinical signs did not differ with statisticalsignificance from the dams without such signs. Thus, reduction both in food intake and bodyweight gain alone could not explain the observed clinical signs and necropsy findings.
Toxicity in pups
In the 450 mg/kg bw/day dose group, examination of the dams showed a statistically significant
increase in post-implantation loss (17%, 15/17 litters) compared with the control group (7%,14/23 litters). There were 32 cases of post-implantation loss. Ten of these cases occurred in fivedams without clinical or necropsy findings.
A statistically significant decrease in the number of viable foetuses was observed in the high dosegroup and this was considered treatment related. Furthermore, a statistically significant increase
in total intrauterine mortality was observed. There were 65 cases of intrauterine mortality (29%vs 14% in the control groups). Five dams with no clinical signs or necropsy findings had 20 cases(20/65) of the total intrauterine mortality; i.e., ~1/3 of the total intrauterine mortality was foundin dams without any adverse clinical symptoms or necropsy findings.
This suggests that post-implantation loss and increased intrauterine mortality was not related tomaternal clinical symptoms nor necropsy findings in the dams and thus raises a concern for thedevelopmental effects of bis(α,α-dimethylbenzyl) peroxide.
Furthermore, there was an increase in the percentage of foetuses with body weight retardationin the 450 mg/kg bw/day dose group (11/17 litters; 31 cases) compared with the control group(5/23; 6 cases). These observations could not be explained by maternal toxicity, since several
dams without adverse clinical signs, necropsy findings, or drastically reduced body weight or foodintake, had foetuses with decreased body weight. There was no difference in the incidence ofpups with decreased body weight in the 50 (5/20 litters; 5 cases) and 150 (7/21 litters; 8 cases)
mg/kg bw/day dose groups compared with the control group (5/23 litters; 6 cases).

10

External examination of the pups in the 450 mg/kg bw/day dose group showed malrotated foreand hind limbs in six foetuses (5/17 litters; 6 cases, statistically significant) and hydrops fetalis
in one foetus. This was considered to be treatment related. Of the six cases with malrotated foreand hind limbs, none of them were from the 3/17 dams with adverse clinical symptoms, and 3/6
cases were from two dams with no clinical and necropsy findings.
There was a high incidence of foetuses with skeletal malformations in the 450 mg/kg bw/day
dose group: short and/or bent scapula (12 cases, 9/17 litters), clavicular (2 cases; 2/17 litters),
humerus (9 cases; 7/17 litters), radius (8 cases; 7/11 litters) and ulna (5 cases; 5/17 litters). In
the 150 mg/kg bw/day dose group, short and/or bent scapula (3 cases; 2/21 litters) wererecorded. This high incidence of malformations, without marked maternal toxicity, is sufficient toraise a concern about the developmental effects of bis(α,α-dimethylbenzyl) peroxide.
In the 450 mg/kg bw/day dose group, there was a statistically significant increase in the incidenceof skeletal variations such as incomplete ossification of skull bones, incomplete ossified sternum,
metacarpal/metatarsal, and wavy and marked wavy ribs, and these incidences occurred without
adverse maternal toxicity. Similarly, in the 150 mg/kg bw/day dose group, some variations wereobserved without clear correlation to maternal clinical signs.
Maternal toxicity is apparent in the present study, but there is no clear connection between
maternal toxicity and foetal malformations, not even in the high dose group. This indicates thatthe developing foetuses are more sensitive than the dams to exposure to the test substance. The
evaluation of the presented data supports the conclusion that the observed developmental effects
following the exposure to bis(α,α-dimethylbenzyl) peroxide are not secondary non-specificconsequences of maternal toxicity.
The DS proposed to classify bis(α,α-dimethylbenzyl) peroxide as Repr. Cat. 2; H361d.

Comments received during public consultation
Three MSCAs agreed with the DS proposal for classification in Repr. Cat. 2 for development.
There was disagreement from the company-manufacturer, based on limited evidence only seenfrom the high dose group and no clear dose-response relationship was observed. In addition, thecompany-manufacturer pointed out that, marked maternal toxicity was apparent in the high dosegroup and this may account for the foetal toxicity. A testing proposal related to a PND study inthe rabbit as a second species is ongoing. The study may be available within 1 year, therefore
the company argued that the assessment for teratogenicity should be discussed when the data
are available.

Assessment and comparison with the classification criteria
Reproductive toxicity includes adverse effects on sexual function and fertility in adult males andfemales, as well as developmental toxicity in the offspring. For bis(α,α-dimethylbenzyl) peroxidefindings concerned developmental toxicity, which was described in the CLP Annex 1: 3.7.1.4“Adverse effects on development of the offspring”.
Only one prenatal developmental toxicity study in rats was available, performed according toOECD TG 414.

11

The table below shows the maternal toxicity findings.
Effects
Mortality
Salivation
Piloerection
alopecia
Clinical signs: (Reduced
activity, vaginal bleeding,pale, cold, hypotonicity, red
colouration around eye)
Necropsy finding
Enlarged adrenals
Blood in uterus
Enlarged spleen
Uterus filled with blood
Stomach distended fill up
Pale liver
Pale kidney

Control

50 mg/kg bw/d

150 mg/kg
bw/d

450 mg/kg bw/d

0
0
0
0

0
0
0
0

0
4/21
0
0

1
8/17
3/17
3/17

0

0

0

10/17

0
0
0
0
0
0
0

0
0
0
0
0
0
0

0
0
0
0
0
0
0

6/17
4/17
3/17
2/17
1/17
1/17
1/17

None

A statisticallysign. temporary
decrease was

Statistically sign.
decrease wasrecorded

Statistically sign.
decrease wasrecorded

233.1 ± 10.7
254. 8 ± 13.1*
321.2 ± 14.5**88 ± 12.8**

234.1 ± 11.0
246.3 ± 15.2**
283.6 ± 24.5**
49.5 ± 20**

Food consumption

recorded.
Body weight
Start weight (g)Weight day 11 (g)Weight day 20 (g)Body weight gain (g)236 ± 20.7
267.3 ± 21.5
338.7 ± 27.6
102.7 ± 14.7

236.8 ± 14.9
265.3 ± 16.3
335.8 ± 20.7
99 ± 13.1** p<0.01
Body weight: The DS argued that the observed body weight parameters of the dams with adverse
clinical signs did not differ statistically significantly from the dams without such signs. Thus,
reduction in food intake and body weight gain alone could not explain the observed clinical signs
and necropsy findings. In addition, no corrected body weight values were given, and the dams
at high does had an average of 9.0 pups per litter which was statistically significantly lower thanin the control group (11.6/litter). Furthermore, the high dose pups had a lower mean foetal
weight, 2.9 vs 3.3 g in the control group. The lower number of pups and their lower weight may
explain the lower uncorrected body weight.
RAC identifies the following observations as relevant for the assessment of the developmental
toxicity/ teratogenicity classification.
Effects
Pre implantation loss

Control

50 mg/kg bw/d

150 mg/kg
bw/d

7%

12%

9%

14%**

450 mg/kg bw/dPost implantation loss

7% (14/23 litters)

4%

5%17%** (15/17
litters)

Late embryonic death

1%

1%

1%

12%**

Dead foetuses

0%

0%

0%

3%**

Total intrauterine mortality

14%

16%

13%

29%**

External examination
Foetuses withabnormalities

2.5%

2.3%

3.5%

26.2%**

Variations

2.5%

2.3%

3.5%

21.5%**

Malformations

0%

0%

0%

4.7%**

1%

2%

Visceral examination
Foetuses withabnormalities

1.3%

2%

12

Skeletal examination
Foetuses withabnormalities

19.4%

15%

22.7%

61.4%**

Variations

17.8%

15%

19.9%

39.8%**

Malformations

1.6%

0%

2.9%

21.6%**

Type of skeletal abnormalities, variations
Skull
Incomplete ossification,marked (> three bones)
Incomplete ossification,marked (1 bone or more)

1%

0%

0%

1%

2%

2%

4%

13%**

Supraoccipital not ossified

0%

1%

1%

1%

Hyoid not ossified

1%

0%

0%

1%

Three or less ossified

4%

2%

7%

13%**

Misaligned

1%

0%

0%

0%

Bipartite

0%

0%

0%

1%

6%

6%

14%*

32%**

0%

1%

1%

8%**

Sternebrae

Ribs
Wavy
Wavy, marked

Type of skeletal abnormalities, malformations
Sternebrae
1%

0%

1%

3%

2%

0%

0%

0%

Scapula bent and/or short

0%

0%

3%

16%**

Clavicula bent and/or short

0%

0%

0%

2%

- Humerus bent and/or short

0%

0%

0%

12%**

Ulna bent and/or short

0%

0%

0%

8%**

Radius bent and/or short

0%

0%

0%

11%**

Femur short, bent

0%

0%

0%

5%**

Tibia bent and/or short

0%

0%

0%

3%

Fibula bent and/or short

0%

0%

0%

4%*

Xiphoid split
Vertebrae, thoracic centra
thoracic bipartite cartilage
dumb-bell shaped
Pectoral girdle

Forelimbs

Hind limbs** (p<0.01)
A statistically significant decrease in the number of viable foetuses was observed in the high dosegroup and this was considered treatment related by the DS. Furthermore, a statisticallysignificant increase in total intrauterine mortality was observed (65 cases of intrauterinemortality). Five dams with no clinical signs or necropsy findings had 20 (~1/3) cases of total
intrauterine mortality. This suggests that post-implantation loss and increased intrauterinemortality may not be related to maternal clinical symptoms.
Toxic effects of the substance were noted in both the dams and the foetuses of the high dosegroup at 450 mg/kg bw/d. There was an increase in some clinical signs as well as reduced bodyweight, body weight gain, reduced food intake and some necropsy findings in the dams of thehigh dose group compared to the control group.
There was also a clear effect of the test substance on the foetuses of the high dose group,
manifested as increased intrauterine mortality, lower foetal weight and an increase in the13incidence of variations and malformations in the pups in the high dose group compared to thecontrol group.
There was a statistically significant increase in post implantation loss, late embryonic death,foetal death and a statistically significant reduction in number of viable foetuses in the high dosegroup. However, the DS assessed the relationship between the individual dams with symptoms
of maternal toxicity and the individual pups showing skeletal abnormalities or with a highincidence of intrauterine mortality including post implantation losses. Regarding intrauterinemortality, the DS reported that it was not possible to relate the higher incidences to the maternal
toxicity. When the findings were studied on an individual basis it was seen that there was noclear correlation between the dams with clinical signs of toxicity and/or necropsy findings andthe intrauterine mortality. Therefore, these findings cannot be ascribed to maternal toxicity and
RAC considers the implantation losses and the total intrauterine mortality to be related to thesubstance administration.
The observations of skeletal malformations, including the statistically significant higher incidencesof effects in the pectoral girdle, the forelimbs and the hind limbs, were specific and could not be
explained only by maternal toxicity.
Placing greater weight, both on the increased intrauterine mortality and on the specific effects
observed from the skeletal malformations, and with the comparisons of the individual dam/litter
data between maternal toxicity and foetal toxicity showing no correlation, then the observed
teratogenicity / developmental toxicity was not secondary to the maternal toxicity. Overall RAC
considered that the criteria for classification for developmental toxicity were met for a presumed
human reproductive toxicant, thus bis(α,α-dimethylbenzyl) peroxide warrants classification as
Repr. 1B; H360D.

ANNEXES:
Annex 1The Background Document (BD) gives the detailed scientific grounds for the opinion.
The BD is based on the CLH report prepared by the Dossier Submitter; the evaluation
performed by RAC is contained in ‘RAC boxes’.

Annex 2

Comments received on the CLH report, response to comments provided by the Dossier
Submitter and RAC (excluding confidential information).

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