Mercury

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

1981-09-30 (first dose) to 1982-04-05/09 (necropsy date)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well documented reliable study.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1993

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Six-month studies were conducted to evaluate the cumulative toxic effects of repeated exposure to mercuric chloride, since 13-week studies were not considered adequate to determine the doses to be used in the 2-year studies. Groups of 10 rats of each sex received 0, 0.312, 0.625, 1.25, 2.5, or 5 mg mercuric chloride per kg body weight in deionized water by gavage for 26 weeks.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Mercury dichloride

EC Number:

231-299-8

EC Name:

Mercury dichloride

Cas Number:

7487-94-7

IUPAC Name:

mercury dichloride

Details on test material:

- Name of test material (as cited in study report): mercuric chloride
- Molecular formula (if other than submission substance): HgCl2
- Molecular weight (if other than submission substance): 271.5
- Substance type: technical product
- Physical state: white powder
- Analytical purity: >99 %, water content >0.1 %; analysis performed by the analytical chemistry laboratory, Midwest Research Institute (Kansas City, MO).
- Impurities (identity and concentrations): no inorganic impurities were found by X-ray emission analysis. No organic impurities were detected by ultravioletbisible and NMR spectroscopies.
- Lot/batch No.: 792985
- Stability under test conditions: no bulk chemical stability studies were necessary because of the physical and chemical properties of mercuric chloride.
- Storage condition of test material:bBecause mercuric chloride is somewhat volatile at room temperature, the compound was stored protected from light in a Nalgene@' container at room temperature.
- Other: substance obtained from the Fisher Scientific Company (Fairlawn, NJ)
No further information given.

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., Portage, MI, USA
- Age at study initiation: 43 to 50 days
- Weight at study initiation: range of mean body weights per dose group: 137- 151 g (males), 119 - 127 g (females)
- Housing: housed five per cage, polycarbonate cages with Edstrom grommets (Hazleton Systems, Inc., Aberdeen, MD), changed twice weekly; bedding: BetaChips, heat-treated hardwood chips, (Northeastern Products Corp.,Warrensburg, NY), changed twice weekly
- Diet: ad libitum, NIH-07 Open Formula Rat Ration, mash (Zeigler Bros., Inc.,Gardnels, PA)
- Water: ad libitum, Source: Village of Mattawan, MI, and IRDC wells.
- Acclimation period: 15 days before being assigned to treatment groups

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 73 °F, 22.8 °C (average)
- Humidity (%): 39 %
- Air changes (per hr): 6-12 changes/hour
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 1981-09-30 (first dose) To: 1982-04-05/09 (necropsy date)

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

deionised

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
- Solutions were prepared by mixing the appropriate amount of mercuric chloride in deionized water.
- Stability studies were not conducted by the analytical laboratory, because no appropriate analytical procedures were available to differentiate between covalently bonded mercuric chloride and the potential ionic species. However, total mercury concentrations were analysed over a 3-week period.
- Dose formulations were stored protected from light at room temperature for up to 3 weeks.
- Dose formulations were prepared at least every 3 weeks.
- Amount of vehicle (if gavage): dose volume 5 mL/kg for 0, 0.312, 0.625, 1.25, 2.5, or 5 mg mercuric chloride / kg body weight.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Dose formulations were routinely analyzed throughout the studies by ultraviolet spectroscopy to determine mercury concentration. In the 6-month studies, dose formulations were analyzed prior to initiation, at mid-point, and at termination. All dose formulations analyzed were within 10% of the target concentrations.

Duration of treatment / exposure:

6 months (26 weeks for males and 27 weeks for females)

Frequency of treatment:

5 days/week

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0.312 mg HgCl2/kg bw
Basis:
actual ingested

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0.625 mg HgCl2/kg bw
Basis:
actual ingested

Doses / concentrations 3

Remarks:

Doses / Concentrations:
1.25 mg HgCl2/kg bw
Basis:
actual ingested

Doses / concentrations 4

Remarks:

Doses / Concentrations:
2.5 mg HgCl2/kg bw
Basis:
actual ingested

Doses / concentrations 5

Remarks:

Doses / Concentrations:
5 mg HgCl2/kg bw
Basis:
actual ingested

No. of animals per sex per dose:

Groups of 10 rats of each sex

Control animals:

yes

Details on study design:

- Route rationale: administration of mercuric chloride in water by gavage was selected as the route of exposure to ensure accurate and consistent exposure during the studies. Mercuric chloride was expected to exacerbate the naturally occurring renal disease of rodents, which increases water consumption; thus, drinking water administration was not chosen.
- Rationale for animal assignment (if not random): blocks were arranged by weight and animals were assigned to treatment groups by random numbers.

Positive control:

no data

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: once weekly, all animals were examined for toxic effects and were palpated for masses.

BODY WEIGHT: Yes
- Time schedule for examinations: initially and once a week; rats were also weighed prior to special study evaluation and at study termination.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): No data

FOOD EFFICIENCY: No data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No data

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at 2 and 4 months and at 6 months
- Animals fasted: No data
- Parameters checked: urea nitrogen, creatinine, sodium, potassium, chloride, calcium, phosphorus, total protein, albumin, A/G ratio, total bilirubin, acid phosphatase, alkaline phosphatase, alanine, aminotransferase, aspartate aminotransferase, lactate dehydrogenase, ornithine carbamoyltransferase, sorbitol dehydrogenase, serum cholinesterase, pH

URINALYSIS: No, only done during chronic study

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

After 6 months, all surviving animals not designated for mercury analysis were killed (CO2) and necropsied. Organ weights were determined for the brain, heart, liver, lung, right kidney, and thymus of all animals, and the right testis of all males. Average age at necropsy: 32-33 weeks.

GROSS PATHOLOGY: Yes.

HISTOPATHOLOGY: Yes. Complete histopathologic examinations were performed on all rats in the control and 5 mg/kg dose groups: adrenal gland, bone marrow, brain, clitoral gland, epididymis, esophagus, heart, kidney, large intestine, liver, lung, lymph nodes (mandibular, mesenteric), mammary gland, nose, ovary, pancreas, parathyroid gland, pituitary gland, preputial gland, prostate, testis (males), thymus, thyroid gland, trachea, urinary bladder, uterus (females), and gross lesions. Kidneys, stomach, preputial gland (males), and clitoral gland (females) were examined from rats of all dose groups.

Other examinations:

no data

Statistics:

The probability of survival was estimated by the product-limit procedure of Kaplan and Meier (1958). Statistical analysis for a possible dose-related effect on survival used the method of Cox (1972) for testing two groups for equality and Tarone(’1s9 75) life table test to identify dose-related trends. The incidence of neoplasms or nonneoplastic lesions is given as the ratio of the number of animals bearing such lesions at a specific anatomic site to the number of animals in which that site was examined. Two approaches were employed to assess the significance of pairwise comparisons between dosed and control groups in the analysis of continuous variables. Organ and body weight data, which have approximately normal distributions, were analyzed using the multiple comparison procedures of Williams (1971, 1972) and Dunnett (1955). Clinical chemistry and haematology data, which typically have skewed distributions, were analyzed using the multiple comparison methods of Dunn (1964) and Shirley (1977). Jonckheere’s test (Jonckheere, 1954) was used to assess the significance of dose-response trends and to determine whether a trend-sensitive test (Williams’ or Shirley’s test) was more appropriate for pairwise comparisons than a test that does not assume a monotonic dose-response trend (Dunnett’s test or Dunn’s test). Average nephropathy severity values were analyzed for significance using the Mann-Whitney U test (Hollander and Wolfe, 1973).

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Description (incidence and severity):

no toxicological relevant changes

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not specified

Details on results:

CLINICAL SIGNS AND MORTALITY
- All rats survived to study end.

BODY WEIGHT AND WEIGHT GAIN
- Effects on body weight in males and females were within 10% of controls and not regarded as adverse.
- No other biologically significant differences in body weights occurred.

CLINICAL CHEMISTRY
- At 4 months, creatine and potassium levels and alanine aminotransferase and aspartate aminotransferase activities were significantly
less than those of the controls for all dosed males.
- Effects on clinical chemistry parameters at months 4 in males were not regarded as adverse.
- No other biologically significant diffences in clinical chemistry parameters were observed

ORGAN WEIGHTS
- Effects on absolute and relative kidney weights were observed at and above 0.312 mg/kg bw/d in males and 0.625 mg/kg bw/d in females.
- No other biologically significant differences in organ weights occurred.

GROSS PATHOLOGY
- Macroscopic changes in dosed males included granular kidneys and enlargement of the parathyroid and thyroid glands
- No biologically significant changes were noted at necropsy for dosed females.

HISTOPATHOLOGY: NON-NEOPLASTIC
- Treatment-related histopathological changes (nephropathy characterized by foci of tubule regeneration, basement membrane thickening and scattered dilated tubules containing hyaline casts) were observed in males with increased severity at and above 1.25 mg/kg bw/d.

OTHER FINDINGS
- Mercury levels in kidney, liver, and brain tissues tended to increase with dose. Mercury levels were highest in the kidney and lowest in the brain. Mercury levels in males and females tended to be similar.

Effect levels

Dose descriptor:

LOAEL

Effect level:

0.312 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: LOAEL based on effects on kidney weights of male rats at 0.312 mg/kg bw/d (0.23 mg/kg bw/d Hg).

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Dose selection rationale: based on body weight changes and renal toxicity, the dose levels of mercuric chloride selected for administration by gavage to male and female rats for the 2 -year studies were 0, 2.5 and 5 mg/kg.

Applicant's summary and conclusion

Conclusions:

In conclusion, only a LOAEL could be established based on effects on kidney weights of male rats at 0.312 mg/kg bw/d (0.23 mg/kg bw/d Hg).