Solvent naphtha (coal), xylene-styrene cut

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: GLP status unknown, guideline study, published in peer reviewed literature, no restrictions, fully adequate for assessment.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2003

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

mixed xylenes

IUPAC Name:

mixed xylenes

Constituent 2

Reference substance name:

Xylene

EC Number:

215-535-7

EC Name:

Xylene

Cas Number:

1330-20-7

Molecular formula:

C8H10

IUPAC Name:

xylene

Details on test material:

- Name of test material (as cited in study report): Technical xylene
- Composition of test material, percentage of components: 15.3% ethylbenzene, 21.3% o-xylene, 43.9% m-xylene, 19.4% p-xylene

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: IFFA CREDO Breeding Laboratories (Saint-Germain-sur-l'Arbresle, France)
- body weight at study initiation: 180 - 200 g
- Housing: Individually in clear polycarbonate cages with stainless-steel wire lids and corn cob granules as bedding
- Diet: Food pellets (UAR Alimentation Villemoisson, France) ad libitum except during exposures
- Water: filtered tap water ad libitum except during exposures
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 21±2°C
- Humidity: 50±5%
- Photoperiod: 12 hrs dark / 12 hrs light:

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Vehicle:

other: air

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 200 L glass/stainless steel inhalation chambers with dynamic and adjustable laminar air flow (6-8 m3/h), maintained at a negative pressure of ≤3 mm water.
- System of generation: a constant rate of liquid chemical was delivered (with a HPLC pump for 2000 ppm or with an infusion pump for the other concentrations). This liquid chemical was delivered at the top of a heated glass column filled with glass beads. Compressed air heated by a glass heater was introduced at the bottom of the glass column in a counter-current fashion to the liquid flow. The vaporized compounds were introduced into the main air-inlet pipe of the exposure chambers.
- Temperature, humidity, pressure in air chamber: 23±2°C, 50±5%

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatography with a flame ionization detector
- Samples taken from breathing zone: no data

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The actual concentrations were determined by gas chromatography with a flame ionization detector. The column temperature was maintained at 80°C. Concentrations of technical xylene were obtained by adding the analytical concentrations of ethylbenzene, o, m- and p-xylene.
The concentrations determined by analyses were essentially the same as the target concentrations.

Details on mating procedure:

Nulliparous females were housed overnight with adult males (one male to two or three females) from the same strain and supplier. The day that vaginal smears were found to be sperm-positive was considered day 0 of gestation (GD).

Duration of treatment / exposure:

6 hr/day

Frequency of treatment:

Daily, from day 6 through 20 of gestation.

Duration of test:

21 days

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 100, 500, 1000 or 2000 ppm
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 434, 2171, 4342, 8684 mg/m3
Basis:
nominal conc.

No. of animals per sex per dose:

23 - 26 mated females/group; 20 - 26 pregnant females/group

Control animals:

yes, concurrent vehicle

Details on study design:

Control animals were exposed concurrently to filtered room air in an adjacent chamber identical to those of the treatment groups.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- recorded on GD 0, 6, 13 and 21
- Body weight changes were calculated for the following gestation intervals: 0-6, 6-13 and 13-21.
- The corrected weight gain was the body weight gain between GD 6-21 subtracted from gravid uterus weight.

FOOD CONSUMPTION: Yes
- Measured for the intervals GD 6-13 and 13-21

POST-MORTEM EXAMINATIONS: Yes - killed on gestation day 21
- Organs examined: Uterus

Ovaries and uterine content:

The uterus was removed and weighed. The number of corpora lutea, implantation sites, resorptions, and dead and live foetuses were recorded. Uteri with no visible implantation sites were stained with ammonium sulphide (10%) to detect very early resorptions.

Fetal examinations:

Live foetuses were weighed, sexed, and examined for external anomalies including those of the oral cavity. Half of the live foetuses from each litter were preserved in Bouin's solution and examined for internal soft tissue changes. The other half were fixed in ethanol (70%), eviscerated, and then processed for skeletal staining with Alizarin Red S for subsequent skeletal examination.

Statistics:

Where appropriate, the data were presented as mean ± SD. One-way analysis of variance was used to analyse the number of corpora lutea, implantation sites and live foetuses, maternal food consumption and body weights and was followed by Dunnett's test where differences were found. The Kruskal-Wallis test was used to evaluate the percentages of non-live implants, resorptions, and males, and the proportions of foetuses with alterations in each litter and was followed by the Mann-Whitney test where appropriate. Pregnancy rates and percentages of litters with any malformations or with external, visceral or skeletal variations were analysed using Fisher's test. Least-squares analysis was carried out where applicable. The level of statistical significance reported was P<0.05. The litter was the unit of analysis for foetal variables.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
Mortality: No maternal deaths.
Bodyweight: At 1000 ppm, significant decrease in weight gain (and a non-significant decrease in absolute weight gain) between GD 6 and GD 13. At 2000 ppm, significant reduction in weight on GD 13 and GD 21 and in corrected weight gain (by 33% and 97% respectively).
Food consumption: significant reduction throughout exposure.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEC

Effect level:

500 ppm

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOAEC

Effect level:

100 ppm

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
No effects on mean number of implantation sites and of live foetuses, and the incidence of non-live implants and resorptions.
Foetal body weights showed a dose-related decrease (significantly different from the control at 500 ppm and above). The decrease was approximately 16% at 2000ppm, 7% at 1000 ppm and 4% at 500 ppm.
The occurrences of foetuses with external, visceral and skeletal variations did not differ between the control and the treatment groups. Visceral malformations occurred sporadically in one or two foetuses and were distributed across the different groups.

Effect levels (fetuses)

Dose descriptor:

NOAEC

Effect level:

>= 2 000 ppm

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The NOAEC for maternal toxicity was 500 ppm and for foetal effects was 100 ppm.

Executive summary:

Inhalation exposure of Sprague-Dawley rats from gestation days 6-20 to technical xylene resulted in maternal toxicity at 1000 and 2000 ppm. Foetal toxicity was seen at 1000 and 2000 ppm, in the presence of maternal toxic effects. There was a 4% lower foetal body weight at 500 ppm, which is considered to be of limited biological relevance. Technical mixed-xylene was not teratogenic up to 2000 ppm.