Chromium trioxide

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-standard published study; reported in sufficient detail

Data source

Reference

Reference Type:

publication

Title:

Embro- and foetotoxicity of chromium in pregestationally exposed mice

Author:

Junaid M, Murthy RC & Saxena DK

Year:

1996

Bibliographic source:

Bull Environ Contam Toxicol 57. 327-334

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

In a study specifically performed to assess the effect of pre-gestational exposure to chromium on development, groups of 15 female Swiss albino mice of proven fertility were administered daily 0, 250, 500 or 750 ppm potassium dichromate (equivalent to doses of approximately 0, 63, 119 and 174 mg/kg/day (0, 20, 40 and 60 mg Cr(VI)/kg/day) in drinking water for 20 days. The animals were then immediately mated for 24 hours with untreated males, and, subsequently, 10 pregnant females were randomly selected from each group and sacrificed on day 19 of gestation. Both ovaries were removed from the dams to determine the number of corpora lutea. Numbers of implantations and resorptions were recorded and the fetuses were subjected to routine external, visceral and skeletal examination. In addition, at sacrifice, levels of total chromium in the maternal blood, in the placenta and in the fetal tissues were measured.

GLP compliance:

no

Remarks:

Published study

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Potassium dichromate

EC Number:

231-906-6

EC Name:

Potassium dichromate

Cas Number:

7778-50-9

Molecular formula:

Cr2H2O7.2K

IUPAC Name:

sodium dichromate

Details on test material:

No further details

Test animals

Species:

mouse

Strain:

Swiss

Details on test animals or test system and environmental conditions:

Sixty, 4-month old, Swiss albino, female mice (body weight 30 +/- 5 g) of proven fertility from the Industrial Toxicology Research Centre colony were divided into four groups of fifteen mice each. The animals were individually housed under standard animal house conditions (room temperture 20-22°C, relative humidity 50+/-5%) where a regular cycle of 12 hrs light: 12 hrs darkness was maintained and were provided with feed pellets (Lipton India Ltd.) and water ad libitum.

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on exposure:

Females were administered potassium chromate in the drinking water for 20 days, prior to mating

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

Exposed females were mated for 24 hours with untreated males

Duration of treatment / exposure:

Females were administered potassium chromate in the drinking water for 20 days, prior to mating

Frequency of treatment:

Continous (in drinking water)

Duration of test:

Females were treated for 20 days prior to a 24-hour mating period with untreated males. Pregnant females were sacrificed on Day 19 of gestation.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

250 ppm

Remarks:

equivalent to approx. 63 mg/kg/day and 20 mg Cr(VI)/kg/day

Doses / concentrations 2

Dose / conc.:

500 ppm

Remarks:

equivalent to approx. 119 mg/kg/day and 40 mg Cr(VI)/kg/day

Doses / concentrations 3

Dose / conc.:

750 ppm

Remarks:

equivalent to approx. 174 mg/kg/day and 60 mg Cr(VI)/kg/day

No. of animals per sex per dose:

15 females were treated and mated; 10 pregnant animals were randomly selected for further investigation

Control animals:

yes, concurrent vehicle

Details on study design:

The selection of doses was based on our earlier study (Trivedi et al. 1989) and the fact that the average chromium intake of humans is approximately 200 g/day in drinking water (NRC 1989)

Examinations

Maternal examinations:

Maternal investigations were limited; blood levels of chromium were investigated

Ovaries and uterine content:

Both ovaries were removed from the dams to determine the number of corpora lutea; the numbers of implantations were recorded

Blood sampling:

Known amounts of maternal blood (withdrawn from the heart of 5 animals/group), of placentae and the fetuses were digested in Nitric acid:Perchloric acid (6:1) mixture till a white residue remained at the bottom of the flask. The residue was dissolved in 5.0 ml of 0.1 N Nitric acid and read on DC Plasma Emission Spectrophotometer (Beckman Spectrospan V). Blank and spiked samples were also run and analyzed simultaneously

Fetal examinations:

Foetuses were assessed for external, visceral and skeletal findings.

Statistics:

Embryo- and feto-toxicity data and chromium estimation data were analysed by one-way ANOVA followed by Student's 't' test while gross and skeletal abnormalities data were analysed by Fischer's Exact Test

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

no effects observed

Description (incidence and severity):

No signs of toxicity were observed in any of the treated females.

Mortality:

mortality observed, treatment-related

Description (incidence):

Mortality of 20% (3 of 15 females) was observed in the top dose group. Although autopsy of these animals could not establish the cause of death, given the number of deaths and the fact that they occurred at the highest dose level, they are likely to be treatment-related.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight gain was unaffected during the treatment period, however during gestation, almost no body weight gain was seen in the top-dose dams, and a reduction in body weight gain of 14% was observed in the mid-dose dams.

Description (incidence and severity):

Daily chromium (VI) intake as calculated by water consumed: 1.9 ± 0.02, 3.56 + 0.03, and 5.23 + 0.07 mg Cr for groups II, III, and IV, respectively. Water consumption in the control group was 8.52 + 0.21 mL/mouse/day,

Maternal developmental toxicity

Pre- and post-implantation loss:

effects observed, treatment-related

Description (incidence and severity):

Compared to controls, a statistically significant reduction in the number of corpora lutea of 44% was noted at 750 ppm. Also, no implantations were seen in this group. The number of implantations was also statistically significantly reduced (by 29% of the control value) in the dams pre-gestationally treated with 500 ppm potassium dichromate. A dose-related (statistically significant in the mid-dose group) increase in pre-implantation loss was seen at 250 and 500 ppm. Statistically significantly increased incidences of post-implantation losses were observed at 250 and 500 ppm, and of resorptions at 500 ppm.

Effect levels (maternal animals)

1

Dose descriptor:

LOAEL

Effect level:

20 mg/kg bw/day

Based on:

element

Remarks:

equivalent to 250 ppm test material

Basis for effect level:

other: developmental toxicity

2

Dose descriptor:

LOAEL

Effect level:

750 ppm

Based on:

test mat.

Remarks:

equivalent to 174 mg/kg bw/day (60 mg CrVI/kg bw/day)

Basis for effect level:

body weight and weight gain

3

Dose descriptor:

LOAEL

Effect level:

500 ppm

Based on:

test mat.

Remarks:

equivalent to 119 mg/kg bw/day (40 mg CrVI/kg bw/day)

Basis for effect level:

pre and post implantation loss

Results (fetuses)

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

Fetal weight and crown-rump length were statistically significantly reduced in the low- and mid-dose groups.

Changes in litter size and weights:

effects observed, treatment-related

Description (incidence and severity):

There was also a dose-related (statistically significant in the mid-dose group) reduction in litter size at 250 and 500 ppm.

External malformations:

effects observed, treatment-related

Description (incidence and severity):

A statistically significant increased incidence of kinky tail, short tail and subdermal hemorrhagic patches was seen at 500 ppm.

Skeletal malformations:

effects observed, treatment-related

Description (incidence and severity):

A statistically significant reduced ossification in the parietal, interparietal and caudal bones was observed in fetuses of dams pregestationally treated with 500 ppm. Fetal caudal ossification was also significantly reduced at 250 ppm.

Visceral malformations:

no effects observed

Description (incidence and severity):

No significant abnormalities were seen during soft tissue examinations in any of the treated groups.

Description (incidence and severity):

Total chromium levels were significantly increased above levels in the control group for the maternal blood in all the treated groups, for the placenta at 250 and 500 ppm and for the fetal tissues at 500 ppm.

Effect levels (fetuses)

Dose descriptor:

LOAEL

Effect level:

250 ppm

Based on:

test mat.

Remarks:

equivalent to 63 mg/kg bw/day (20 mg CrVI/kg bw/day)

Sex:

male/female

Basis for effect level:

other: fetotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Chromium-induced embryo- and feto-toxicity in mice treated during pregestational period

Parameters	Group I (control)	Group II (250 ppm)	Group III (500 ppm)	Group IV (750 ppm)
Weight gain in mothers (g)	14.40 ± 1.01	13.43 ± 0.50	12.38 ± 0.49	1.7 ± 0.93
Number of corpora Iutea/mice	7.9 ± 1.01	7.4 ± 0.50	7.3 ± 0.37	4.4 ± 0.50abc*
Number of implantations/mice	7.7 ± 0.74	6.8 ± 0.41	5.4 ± 0.27a*	0
Number of live fetuses/mice	7.7 ± 0.74	5.8 ± 0.50	3.4 ± 0.24ab*	0
Number of resorptions/mice	0	1.20 ± 0.44	2.0 ± 0.31a*	0
Pre-implantation loss (%)	2.77 ± 1.21	8.38 ± 3.53	24.79 ± 2.17ab*	100
Post-implantation loss (%)	0	17.51 ± 2.22a*	36.66 ± 4.94ab*	0
Fetal weight (g)	1.59 ± 0.04	1.11 ± 0.04a*	0.97 ± 0.03ab*	0
Placental weight (g)	0.137 ± 0.003	0.128 ± 0.005a*	0.223 ± 0.005ab*	0
Crown-rump length (cm)	2.92 ± 0.07	2.41 ± 0.08a*	2.09 ± 0.08ab*	0

Value represents mean± S.E. of 10 female mice in each group.

The significance of the difference among various groups was evaluated by applying one-way ANOVA followed by Student’s ‘t’ test. * Significance p< 0.05. Comparison between two groups: a –vs. control; b –vs. 250 ppm; c –vs. 500 ppm

Incidence of gross and skeletal abnormalities in the pups of dams treated with chromium during the pregastational period

Parameters	Group I (control)	Group II (250 ppm)	Group III (500 ppm)
Gross abnormalities
Number of pups/litter observed	72/10	51/10	19/10
Drooping wrist	0/10	0/10	6/4 (32)
Sub-dermal hemorrhagic patches	0	8/6 (16)	8/4 (42)a*
Kinky tail	0	0	8/6 (42)a*
Short tail	0	4/4 (9)	10/4 (53) a*
Skeletal abnormalities
Number of pups/litter observed	43/10	34/10	19/10
Reduced parietal ossification	0	0	12/10 (63)a*
Reduced interparietal ossification	0	0	10/10 (53)a*
Reduced caudal ossification	6/4 (12)	18/8 (53)a*	18/10 (95)a*

Gross and skeletal abnormalities are represented as number of abnormal pups/litters observed. The statistical significance was evaluated by Fisher’s Exact test. Percentage on parentheses calculated by the total number of pups observed. * Significance p< 0.05. Comparison between two groups: a –vs. control.

Applicant's summary and conclusion

Conclusions:

Exposure of female mice to potassium chromate prior to mating resulted in reduced fertility (decreased numbers of corpora lutea, increased implantation loss) and also in developmental toxicity. Maternal toxicity was seen at the top dose level (mortality).

Executive summary:

Female mice were exposed to potassium dichromate in drinking water at levels of 0, 250, 500 or 750 ppm (equivalent to Cr (VI) intakes of 0, 20, 40 and 60 mg/kg bw/d) for 20 days prior to mating with untreated males. Dams were sacrificed at Day 19 of gestation and the foetuses examined.

Deaths occurred at the top dose level of 60 mg/kg bw/d; no additional maternal toxicity was apparent. At 60 mg/kg bw/d there were reduced corpora lutea and no implantations; implantation numbers were also reduced at 40 mg/kg bw/d. Pre-implantation loss was increased at 20 and 40 mg/kg bw/d; increased post-implantation losses were also seen at 20 and 40 mg/kg bw/d and resorptions were increased at 40 mg/kg bw/d.

Foetal numbers were significantly lower and foetal weight and size were significantly lower at 20 and 40 mg/kg bw/d.

There was no evidence of teratogenicity. Increased incidences of kinky tail, short tail and subcutaneous haemorrhage were seen at 40 mg/kg bw/d. Reduced ossification of a number of bones was seen at 40 mg/kg bw/d; findings at 20 mg/kg bw/d were limited to reduced caudal ossification. Analysis of chromium levels revealed distribution to the maternal blood, placenta and foetal tissue at 40 mg/kg bw/d.