Aromatic hydrocarbons, C9-12, benzene distn.

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable well-documented publication which meets basic scientific principles.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1990

Materials and methods

Principles of method if other than guideline:

Groups of 30 pregnant female mice were exposed via inhalation to 100, 500, or 1500 ppm of high flash aromatic naphtha for 6 hrs per day during gestation days 6 -15. The mice were sacrificed on gestation day 18, and examined for a variety of fetal developmental parameters including number of viable and nonviable fetuses, number of resorptions, total implantations, and number of corpea lutea. Animals were also examined for maternal toxicity signs including body weight, and changes in appearance and behaviour.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Hydrocarbons, C9, aromatics

EC Number:

918-668-5

IUPAC Name:

Hydrocarbons, C9, aromatics

Test animals

Species:

mouse

Strain:

CD-1

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Portage, MI
- Age at study initiation: 10-11 weeks
- Housing: Inidividually housed in wire mesh cages
- Diet (e.g. ad libitum): Purina Certified Rodent Chow No. 5002 ad libitum except during exposure
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 2-3 weeks


ENVIRONMENTAL CONDITIONS
Animal husbandry followed standards by the US Department of Health, Education, and Welfare (1985)

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 16 m glass and steel chambers.
- Method of holding animals in test chamber: cages
- Source and rate of air: Air was provided by a separate HVAC system.
- Method of conditioning air: Air was filtered for particulates and temperature and humidity controlled.
- System of generating particulates/aerosols: Test atmosphere was generated by heating nitrogen to 200°C by passing it through a 1 l stainless steel cylinder with a 1500 W band heater. The nitrogen then passed through a glass column 7.6 cm diameter and 30 cm long packed with glass beads. Test material was delivered by a metering pump into Teflon tubing, to the bottom of the column. The liquid test substance vaporized as it went up the column with the nitrogen. The vapor then went into the test chambers where dilution with the chamber ventilation air produced the desired concentrations.
- Temperature, humidity, pressure in air chamber: Air flow rate, temperature and relative humidity were monitored every half-hour during exposure.


TEST ATMOSPHERE
- Brief description of analytical method used: Measurements made hourly using gas-phase IR.
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentration of the test material in the test chambers was determined by GC analysis.

Details on mating procedure:

- Proof of pregnancy: vaginal plug

Duration of treatment / exposure:

6 hours per day

Frequency of treatment:

gestation day (GD) 6 - 15 and GD 18

Duration of test:

Through GD 18.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
100 ppm
Basis:
nominal conc.
102 ppm mean measured

Doses / concentrations 2

Remarks:

Doses / Concentrations:
500 ppm
Basis:
nominal conc.
500 ppm mean measured

Doses / concentrations 3

Remarks:

Doses / Concentrations:
1500 ppm
Basis:
nominal conc.
1514 ppm mean measured

No. of animals per sex per dose:

30 pregnant females per dose

Control animals:

yes, concurrent no treatment

Details on study design:

- Rationale for animal assignment: random

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Check twice daily for viability and changes in appearance and/or behaviour.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: GD 6-15 and GD18

BODY WEIGHT: Yes
- Time schedule for examinations: GD 0 and GD6-18

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #: 18
- Organs examined: Lung, liver, kidney, uteri


OTHER: Blood samples were drawn on GD15 from the control, 500 ppm, and 1500 ppm groups and evaluated for leukocyte, erythrocyte counts, hemoglobin, and hematocrit

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: uterine content was examined
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: number of viable and non-viable fetuses

Fetal examinations:

- External examinations: Yes: all per litter were examined for weight, sex, malformations, and variations
- Soft tissue examinations: Half of the fetuses were dissected, internally sexed, and examined for internal malformations and variations. Heads were used for soft tissue examination, also hearts were dissected.
- Skeletal examinations: Yes: all per litter
- Head examinations: Yes: Heads of half the fetuses were used for soft tissue examination.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
At the 100 ppm level, weight gain was reduced, but not significantly different from control. No other signs of maternal toxicity were seen. In the 500 ppm group, one animal died due to an unrelated injury, another animal died due to unknown reasons. There was significantly reduced weight gain in this group. No other signs of toxicity were seen. The 1500 ppm group showed severe maternal toxicity. 14 animals at this exposure level died. Other signs of toxicity include abnormal gait, labored breathing, hunched posture, weakness, inadequate grooming, circling, and ataxia.

No differences in organ weights were noted between the groups. The hematological examination showed significant decreases in hematocrit, and mean corpuscular volume in the high exposure groups. Leukocyte count was reduced in the 500 ppm group, but was not dose related.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEC

Effect level:

100 ppm

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOAEC

Effect level:

100 ppm

Basis for effect level:

other: developmental toxicity

3

Dose descriptor:

LOAEC

Effect level:

500 ppm

Basis for effect level:

other: maternal toxicity

4

Dose descriptor:

LOAEC

Effect level:

500 ppm

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Number of live fetuses/litter was in the 100 ppm group significantly reduced, however, this effect was not dose related. The 500 ppm group showed significant reduction in fetal body weight. There was no other evidence of developmental toxicity in this group. In the 1500 ppm group there was a significant reduction in the number of live fetuses/litter, and mean fetal body weight. Postimplantation loss was significantly higher, as was the number of fetuses with cleft palate. Ossification, particularly in the skull and sternebrae, was delayed.

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

	Control	100 ppm	500 ppm	1500 ppm
Number of maternal deaths	0	0	2	14/32 (two replacement dams added on GD6)
Number of litters with viable fetuses	24	21	23	13 (3 litters resorptions only)
Live fetuses/litter	10.7 ±1.8	8.7 ± 4.6	9.3 ± 3.1	7.9 ± 4.3
Postimplantation loss/dam	0.9 ± 0.9	2.3 ± 4.1	2.0  ± 3.1	4.3 ± 3.7
Fetal body weight (grams)	1.25 ± 0.14	1.24 ± 0.08	1.16 ± 0.11	0.82 ± 0.17
Maternal weight gain	23  ± 2.7	19 ± 8.8	19 ± 5.6	14 ± 6.8

Applicant's summary and conclusion

Conclusions:

The maternal and developmental toxicity NOAEC = 100 ppm. The maternal toxicity LOAEC was 500 ppm based on significant reduction in weight gain for the dams. The development toxicity LOAEC was 500 ppm based on significant reduction in weight gain likely caused by the significant reduction in maternal body weight.

Executive summary:

This study was conducted to determine the developmental toxicity of high flash aromatic naphtha. Groups of 30 pregnant female mice were exposed via inhalation to 100, 500, or 1500 ppm of high flash aromatic naphtha for 6 hrs per day during gestation days 6 -15. The mice were sacrificed on gestation day 18, and examined for a variety of fetal developmental parameters including number of viable and nonviable fetuses, number of resorptions, total implantations, and number of corpea lutea. Animals were also examined for maternal toxicity signs including body weight, and changes in appearance and behaviour. There was a statistically significant reduction in body weight gain in dams and reduced mean body weight for fetuses in the 500 ppm exposure group. Therefore, the maternal and developmental toxicity NOAEC = 100 ppm. The maternal toxicity LOAEC was 500 ppm based on significant reduction in weight gain for the dams. The development toxicity LOAEC was 500 ppm based on significant reduction in weight gain likely caused by the significant reduction in maternal body weight.