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Toxicological information

Toxicity to reproduction: other studies

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Administrative data

Endpoint:
toxicity to reproduction: other studies
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
unsuitable test system

Data source

Reference
Reference Type:
publication
Title:
Diesel exhaust particles cause increased levels of DNA deletions after transplacental exposure in mice
Author:
Reliene R., Hlavocova A., Mahadevan B., Baird WM., Schiestl RH
Year:
2005
Bibliographic source:
Mutation Research 570 (2005) 245–252

Materials and methods

Principles of method if other than guideline:
In an in vivo DNA Deletion Assay, pregnant C57BL mice, homozygous for the pun allele were given daily oral doses of 500 mg/kg bw carbon black for 5 consecutive days from day 10.5 to day 15.5 post coitum. Method of dose delivery was not specified. Day of identification of vaginal plug was designated day 0.5 post coitum. Phosphate buffered saline (PBS) served as vehicle. To determine DNA deletion frequencies, 20-day-old offspring were sacrificed, and their retinal pigment epithelium isolated to visualize the eye-spots by determining the frequency of 70 kb DNA deletions at the pink-eyed unstable (pun) allele of the pink -eyed dilution (p) gene in melanocyte precursor cells. Mice homozygous for the pun allele have a light grey coat colour and a transparent retinal pigment epithelium (RPE). A deletion of one copy of a duplicated 70-kb DNA fragment within the pun locus restores the pink-eyed dilute (p) gene, which encodes a protein responsible for the assembly of a black colour melanin complex. Deletion events occurring in pre-melanocytes cause visible black patches (fur-spots) on the light gray fur of offspring and black pigmented cells (eye-spots) on the unpigmented retinal pigment epithelium (RPE). Deletion are scored and visualised as eye-spots defined as a pigmented cell or a group of adjacent pigmented cells separated from each other by no more than five unpigmented cells was considered as an eye-spot that resulted from one deletion/pun reversion event.

GLP compliance:
not specified
Type of method:
in vivo

Test material

Constituent 1
Chemical structure
Reference substance name:
Carbon black
EC Number:
215-609-9
EC Name:
Carbon black
Cas Number:
1333-86-4
Molecular formula:
C
IUPAC Name:
Carbon black
Test material form:
not specified

Test animals

Species:
mouse
Strain:
other: C57BL Further characterisation of animals: C57BL/6Jp^un/p^un
Details on test animals or test system and environmental conditions:
C57BL/6Jpun/pun mice were obtained from the Jackson Laboratory (Bar Harbor, ME). Mice were bred in the institutional specific pathogen free animal facility under standard conditions with a 12 h light/dark cycle, and were fed standard diet and water ad libitum.

Administration / exposure

Route of administration:
oral: unspecified
Vehicle:
other: Foetal calf serum
Duration of treatment / exposure:
5 days
Frequency of treatment:
Daily on days 10.5–15.5 (days post coitum)
Doses / concentrations
Dose / conc.:
500 mg/kg bw/day (nominal)
No. of animals per sex per dose:
4-6 dams
Control animals:
yes, concurrent vehicle
Details on study design:
Pregnancy was timed by checking for vaginal plugs, with noon of the day of discovery counted as 0.5 days post-coitum (dpc). Similarly, the birth of a litter was timed with the noon of discovery counted as 0.5 days post-partum (dpp).

Results and discussion

Effect levels

Dose descriptor:
NOEL
Effect level:
500 mg/kg bw/day (nominal)
Based on:
test mat.

Observed effects

No effects observed. CB exposure (500 mg/kg bw) did not increase the number of eye-spots.

Applicant's summary and conclusion

Conclusions:
Study is considered not reliable as it is not ascertainable whether a commercial form of CB or lab spark generated CB was used for the experimnent.
Executive summary:

In an in vivo DNA Deletion Assay, pregnant C57BL mice, homozygous for the punallele were given daily oral doses of 500 mg/kg bw carbon black for 5 consecutive days from day 10.5 to day 15.5 post coitum. Method of dose delivery was not specified. Day of identification of vaginal plug was designated day 0.5 post coitum. Phosphate buffered saline (PBS) served as vehicle. To determine DNA deletion frequencies, 20 days olds offspring of treated dams were sacrificed, eyes removed, and the whole mount retinal pigment epithelium (RPE) slides prepared for eye-spot analysis. An eye-spot that resulted from one deletion/pun reversion event was defined as a pigmented cell or a group of adjacent pigmented cells separated from each other by no more than five unpigmented cells. CB exposure (500 mg/kg bw) did not increase the number of eye-spots. The authors provide too limited a description of the test substance as to allow an indubitable identification as CB. It appears that the investigators may have used laboratory spark-generated product and not a commercially attainable one meeting the CAS description of CB. It is important to note the morphological differences between spark-generated CB (SGCB) and commercially attainable CB products. Unlike commercial products, which are manufactured, shipped or put on the market principally as agglomerates of covalently fused primary particles, laboratory spark-generated CB is comprised of singlet particles. SGCBs are therefore poor representations of commercially available CB products