Chromium trioxide

Toxicity to reproduction

Administrative data

Endpoint:

fertility, other

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Long-term exposure of male and female mice to trivalent and hexavalent chromium compounds: effect on fertility

Author:

Elbetieha, A & Al-Hamood, M.H.

Year:

1997

Bibliographic source:

Toxicology 116: 39 - 47.

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The effects on fertility were investigated following the administration of potassium dichromate to male and female mice for 12 weeks before mating. Treated males were mated with untreated females (experiment 1) and treated females were mated with untreated males (experiment 2). Females were sacrificed one week following mating.

GLP compliance:

not specified

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:

The test substance was purchased from Aldrich Chemical Corp. and provided by the NTP through Research Triangle Institute (RTI), (Research Triangle Park, North Carolina). All bulk chemical analyses and test formulations analyses were conducted by RTI. Prior to the initiation of dosing, two 5 g samples of the bulk test article were collected into amber glass bottles with Teflon coated lids, sealed and stored in the freezer protected from light for possible analysis. A bulk test article of 5 g was collected and sent to RTI for purity and stability testing within 30 days of receipt. The compound was analyzed at RTI upon receipt from the vendor, Aldrich and the relative purity was determined to be approx. 99%, based on potassium content. The identity and purity of the compound was confirmed by infrared spectrometry and inductively coupled plasma emission spectrometry (ICP). A bulk chemical reanalysis was sent on May 9, 1995 and analyzed on August 16, 1995. The relative purity was determined to be 98.5% based on potassium content.

Specific details on test material used for the study:

hexavalent chromium (potassium dichromate: Fluka AG, Chemische Fabrik CH-9470, Bucks)

Test animals

Species:

mouse

Strain:

Swiss

Sex:

male/female

Details on test animals or test system and environmental conditions:

Sexually mature male and female Swiss mice (day 50 of age) were used in these experiments. They were raised in the animal house unit in the Medical Faculty at the Jordan University of Science and Technology in controlled temperature 21°C +/- 1°C under a 12 h light: 12 h darkness schedule (lights 06.00-18.00 h). Food and water were available ad libitum.

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on mating procedure:

1 treated male: 2 untreated females
1 untreated male: 3 treated females

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

Treated males or females were mated with untreated animals following exposure for 12 weeks

Frequency of treatment:

Continuous

Details on study schedule:

The effects of potassium dichromate on male and female fertility were investigated in sexually mature (7 weeks old) Swiss mice administered this hexavalent chromium compound in drinking water. Groups of 9-20 males were administered 0, 1000, 2000, 4000 or 5000 mg/l potassium dichromate equivalent to doses of approximately 0, 166, 333, 666, 833 mg/kg/ bw/d (0, 60, 120, 235, 290 mg Cr(VI)/kg/day) for 12 weeks and then mated for ten days, 1 male to 2 untreated females. The exposed males were then removed and 1 week later the females were terminated. Similarly, groups of 11-18 females were administered 0, 2000 or 5000 mg/l potassium dichromate equivalent to doses of approximately 0, 400, 1000 mg/kg bw/d (0, 140, 350 mg Cr(VI)/kg bw/d) for 12 weeks and then mated for ten days, 3 females to 1 untreated male. One week after the removal of the males, the females were terminated. The Number of pregnant females, total implantations, viable fetuses and resorptions were recorded. In addition, satellite groups of 10-13 males and 8-10 females administered 0, 2000 (males only) or 5000 mg/l potassium dichromate for 12 weeks were sacrificed at the end of the treatment. Body weights and reproductive organ weights were recorded in these animals.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/L drinking water

Doses / concentrations 2

Dose / conc.:

1 000 mg/L drinking water

Remarks:

males; equivalent to 166 mg/kg bw/d

Doses / concentrations 3

Dose / conc.:

2 000 mg/L drinking water

Remarks:

males; equivalent to 333 mg/kg bw/d
females; equivalent to 400 mg/kg bw/d

Doses / concentrations 4

Dose / conc.:

4 000 mg/L drinking water

Remarks:

males; equivalent to 666 mg/kg bw/d

Doses / concentrations 5

Dose / conc.:

5 000 mg/L drinking water

Remarks:

males; equivalent to 833 mg/kg bw/d
females; equivalent to 1000 mg/kg bw/d

No. of animals per sex per dose:

9-20 males; 11-18 females

Control animals:

yes, concurrent vehicle

Examinations

Parental animals: Observations and examinations:

observation of mortality and clinical signs

Oestrous cyclicity (parental animals):

not examined

Sperm parameters (parental animals):

not examined

Litter observations:

not examined

Postmortem examinations (parental animals):

No of pregnant females, No of implantations, No of viable fetuses, No of mice with resorptions, Total no of resorptions were recorded. Body weights and reproductive organ weights were recorded in satellite animals

Postmortem examinations (offspring):

not examined

Statistics:

Data are expressed as means +/- S.D. Differences between control and chromium exposed groups were analyzed using either Chi-square or Student ‘t’ tests

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Description (incidence and severity):

Generally there were no mortality or clinical signs of toxicity in any group of male or female mice exposed to hexavalent chromium compounds.

Mortality:

no mortality observed

Description (incidence):

Generally there were no mortality or clinical signs of toxicity in any group of male or female mice exposed to hexavalent chromium compounds.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The body weight significantly decreased in 2000 mg/L and 5000 mg/L (p < 0.01) hexavalent chromium exposed males. Exposure of female mice to 5000 mg/L hexavalent chromium had no significant effect on body weights. For further details see 'Any other information on results'

Water consumption and compound intake (if drinking water study):

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

effects observed, treatment-related

Description (incidence and severity):

When the adult males exposed to hexavalent chromium and unexposed control males were tested with adult untreated females for 5 min, males were sexually interested, as females were pursued by males, their genitalia were examined and mounting occurred.
The number of implantation sites and the number of viable fetuses were reduced significantly in females impregnated by males exposed to 2000 mg/l (p < 0.01) and 4000 mg/l (p < 0.05) hexavalent chromium compound. The numbers of resorptions and dead fetuses were increased in females impregnated by hexavalent chromium exposed males.
Exposure of adult female mice to hexavalent chromium compounds had no effect on female fertility (pregnancy occurred in a similar frequency control and chromium exposed females). The numbers of implantations were significantly reduced in pregnant females exposed to 2000 mg/l (p < 0.01) and 5000 mg/l (p < 0.05) hexavalent chromium compounds. The number of viable fetuses was also significantly reduced in pregnant females exposed to 2000 mg/l (p < 0.05) and 5000 mg/l (p < 0.01) of hexavalent chromium compound.
The number of pregnant female mice with resorptions was significantly increased in females exposed to 2000 mg/l (p < 0.01) and 5000 mg/l (p < 0.005) hexavalent chromium compound. The number of resorptions was high in pregnant females exposed to hexavalent chromium compounds compared to control pregnant females.
For further details see 'Any other information on results'

Effect levels (P0)

1

Dose descriptor:

NOAEL

Effect level:

1 000 mg/L drinking water

Based on:

test mat.

Remarks:

Potassium dichromate in drinking water (nominal); equivalent to 166 mg/kg bw/d

Sex:

male

Basis for effect level:

reproductive performance

2

Dose descriptor:

LOAEL

Effect level:

2 000 mg/L drinking water

Based on:

test mat.

Remarks:

Potassium dichromate in drinking water (nominal); equivalent to 400 mg/kg bw/d

Sex:

female

Basis for effect level:

reproductive performance

Target system / organ toxicity (P0)

Critical effects observed:

not specified

Results: F1 generation

Effect levels (F1)

Remarks on result:

not measured/tested

Overall reproductive toxicity

Reproductive effects observed:

not specified

Any other information on results incl. tables

At higher concentrations, the treated animals consumed less water per day compared to the control group (no more details provided). It is unclear whether or not the dose was adjusted for the reduced water consumption or if these animals received a lower dose. There were no deaths or clinical signs of toxicity in any group of male or female mice exposed. Compared to the control group, a statistically significant reduction in absolute body weight of 10% and 12% was seen in satellite group males at 2000 and 5000 mg/l (the only two dose levels at which body weight was recorded), respectively. Body weight of satellite group females administered 5000 mg/l potassium dichromate (the only dose at which body weight was recorded) was unaffected. Relative testes weights were statistically significantly increased at 2000 (by 17.5%) and at 5000 mg/l (by 21.5%). Relative seminal vesicles and preputial gland weights were statistically significantly reduced at 5000 mg/l only (by 27% and 34%, respectively). A statistically significant increase in relative ovarian weight (by 50%) was reported at 5000 mg/l. It is noted that in the absence of information on the absolute organ weights, the increase seen in relative testis weight could be accounted for by the reduction in absolute body weight observed in males. It is also noted that, in the absence of histopathological examinations, it is difficult to interpret the toxicological significance of these organ weight changes.

Compared to the control groups, the percentage of pregnant unexposed females mated with treated males and of pregnant exposed females mated with untreated males was unaffected by treatment. The mean number of implantation sites was statistically significantly reduced in females impregnated by males treated with 2000 (6.33 versus 8.18 in the control group) and 4000 mg/l potassium dichromate (6.86 versus 8.18), but not with the highest dose (7.84 versus 8.18). Given the absence of a dose-response relationship, the toxicological significance of this finding is uncertain. However, it is possible that at higher concentrations, the actual doses the animals received were lower than the nominal doses, due to the reduced water consumption. There were no resorptions or dead foetuses in the control groups, or in the females impregnated by males treated with 2000 or 4000 mg/l potassium dichromate. However, 3 resorptions were noted in the females impregnated by males treated with the lowest dose (1000 mg/l). Given the absence of a clear dose-response relationship and that it is not clearly reported whether these findings occurred in one single litter or in different litters, the 3 resorptions seen at 1000 mg/l are regarded as being incidental. A total number of 6 resorptions and of 6 dead fetuses was also observed in the females impregnated by males treated with the highest dose (5000 mg/l). Although it is not reported whether these findings occurred in one single litter or in different litters, given the incidence, it is unlikely they occurred in one isolated litter. Hence, the fetolethality reported at this dose level (5000 mg/l) is regarded as being treatment-related. The mean number of implantations and of viable fetuses was also statistically significantly reduced in females treated with 2000 mg/l (7.35 versus 9.00 and 6.55 versus 8.76, respectively) and 5000 mg/l potassium dichromate (7.44 versus 9.00 and 5.88 versus 8.76, respectively). There was also a statistically significant increase in the number of pregnant females with resorptions at 2,000 (53% versus 11%) and at 5000 mg/l (63% versus 11%). Similarly, a total number of 37 and 14 resorptions (versus 4 in the control group) were observed at 2000 and 5000 mg/l, respectively.

Applicant's summary and conclusion

Conclusions:

Administration of high concentrations of potassium (VI) dichromate in drinking water to male and female mice prior to mating was found to have adverse effects on fertility (reduced numbers of implantations).

Executive summary:

Male and female Swiss mice were administered potassium (VI) dichromate in drinking water for 12 weeks prior to mating with untreated animals. Female mice were sacrificed one week following treatment; the numbers of pregnant animals, total implantations, viable foetuses and resorptions were recorded. Satellite groups of animals were also treated for 12 weeks (without mating) and the weights of the reproductive organs recorded.

There were no deaths or signs of toxicity; slightly reduced bodyweights were seen in both groups of treated males. Relative testes weights were significanlty increased in both satellite groups, however findings may be secondary to bodyweight effects. Relative seminal vesicle and preputial gland weights were significantly lower, however the toxicological significance of these findings is unclear in the absence of histopathology. Relative ovary weight was increased in females at 1000 mg/kg bw/d. Mean numbers of implantation sites were lower in treated groups, however a dose-response relationship is not apparent.