Styrene

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well-documented study report meeting basic scientific principles.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Reference 2

Reference Type:

secondary source

Title:

European risk assessment report, Styrene CAS No. 100-42-5, EINECS No. 202-851-5, Draft for submission to SCHER, November 2007.

Author:

European Union

Year:

2007

Bibliographic source:

European risk assessment report, Styrene CAS No. 100-42-5, EINECS No. 202-851-5, Draft for submission to SCHER, November 2007.

Materials and methods

Principles of method if other than guideline:

Mice were dosed orally with styrene, daily, for five consecutive days. 24 hours after the last dose, animals were killed and the lung examined microscopically and the cell replication (BrdU incorporation) determined in this tissue.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Styrene

EC Number:

202-851-5

EC Name:

Styrene

Cas Number:

100-42-5

Molecular formula:

C8H8

IUPAC Name:

ethenylbenzene

Specific details on test material used for the study:

- Name of test material (as cited in study report): styrene, Sigma Aldrich
- Physical state: liquid
- Analytical purity: 99%, stabilised with 10 - 15 ppm 4-tert-butylcatechol
- Storage condition of test material: stored at 4 °C

Test animals

Species:

mouse

Strain:

CD-1

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Margate, Kent
- Weight at study initiation: 22 - 27 g
- Diet: certified CT1 diet, ad libitum
- Water: mains water, ad libitum


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 23
- Humidity (%): 40 - 70
- Air changes (per hr): 25 - 30
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

coconut oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Amount of vehicle (if gavage): 10 mL/kg

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

single dose

Frequency of treatment:

5 doses on five consecutive days

Doses / concentrations

Remarks:

Doses / Concentrations:
10, 100 and 200 mg/kg
Basis:
actual ingested

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Examinations

Observations and examinations performed and frequency:

Body weight and clinical signs.

Sacrifice and pathology:

Macroscopical and microscopical examination of the lung.

Other examinations:

Three days prior to sacrifice each animal was fitted with an osmotic pump containing 200 µL 5-bromo-2'-deoxyuridine in order to quantify pulmonar cell replication. 500 cells were counted for each compartment of the lung.

Statistics:

Two-sided student's t-test

Results and discussion

Effect levels

Dose descriptor:

NOAEL

Effect level:

10 mg/kg bw/day (actual dose received)

Sex:

male

Basis for effect level:

body weight and weight gain

clinical signs

gross pathology

histopathology: non-neoplastic

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Two mice in the control group died.

Bodyweight gains and clinical signs in animals dosed with styrene were normal and comparable to those in the control group.

There were no treatment-related macroscopic findings at any dose. Microscopically there were no effects observed in mice dosed with 10 or 100 mg/kg. In mice, dosed 200 mg/kg, 3/10 animals exhibited minimal to slight focal crowding of non-ciliated cells (Clara cells) in the epithelium of the terminal bronchiole. There was no evidence of either cellular necrosis or damage.

There was no evidence of an increase in cell replication in the large bronchioles or alveolar regions of animals at any dose level, nor in the terminal bronchioles of animals administered 10 mg/kg/day styrene. However, in animals administered 100 or 200 mg/kg/day styrene there was a statistically significant and dose dependent increase in the frequency of S-phase cells in the terminal bronchioles, with levels being increased up to 5-fold in top dose animals compared with controls.

Dose [mg/kg]	Labelling index in terminal bronchiole
0	1.8 ± 0.9
10	1.1 ± 0.5
100	3.8 ± 2.5
200	9.9 ± 2.7

During inhalation exposure the cell type which is morphologically affected and the one which undergoes increasedcell devision appears to be the non-ciliated Clara cell. The same target cell and virtual identical response is seen after oral dosing with styrene.