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Toxicity to reproduction

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Administrative data

Endpoint:
toxicity to reproduction
Remarks:
other: 13-week subchronic study with information on reproductive organs.
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
supporting study
Study period:
1993
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
This is a guideline study of sodium cyanide (CAS No. 143-33-9). Experimental data was reviewed by the ECETOC Task Force, author of the JACC Report No. 53, “Cyanides of Hydrogen, Sodium and Potassium, and Acetone Cyanohydrin (CAS No. 74-90-8, 143-33-9, 151-50-8 and 75-86-5)”, 2007. The report is a weight of evidence approach to an extensive body of literature, much of which was undertaken prior to development of guidelines. The report was peer reviewed by the scientific non-governmental organization (NGO), which judged the data to be reliable with restrictions.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1993

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
other: Precedes establishment of EPA 870.3100, 90-day Oral Toxicity in Rats
Deviations:
yes
Remarks:
; pH of drinking water is 8.5; difficulty maintaining dose level in drinking water.
Principles of method if other than guideline:
This experiment preceeds establishment of this method. This is a standard 90-day subchronic protocol with histopathology of the reproductive organs, vaginal cytology and examination of sperm parameters including motility
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
The test material was characterized by NTP, and purity was 99.9%. Test material administered is sodium cyanide, (CAS 143-33-9), but is present as hydrogen cyanide in the GI tract. The pKa is approximately 9, so at physiological pH and 37 °C, all cyanide species are present in the non-ionized form of hydrogen cyanide.

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
This study also utilized B6C3F1 mice, males and females. Rats were obtained from Taconic Laboratory Animals and Services, Germantown, NY. Mice were obtained from Simonsen Laboratories (Gilroy, CA). Rats and mice were approx 31 days of age at receipt and were quarantined 11 days; the animals were 6 weeks when the studies began. Sera obtained from blood samples were analyzed for anitbody titiers to rodent viruses and were negative.

Administration / exposure

Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
The water in treatment groups was pH 8.5. No information is given for the pH of water consumed by control animals. As the pKa for cyanides is 9.36 at 20 degrees C, the form of cyanide present in the water is hydrogen cyanide. Authors suspected volatilization of the cyanide in the drinking water (phase change from liquid to vapour at 25 degrees C).
Details on mating procedure:
No mating occurred in this protocol.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Concentrations were periodically analyzed by spectrophotometric measures. All formulations for dosing were within 10% of the thoretical concentrations when analyzed within 2 days of preparation. Water bottles were changed at least once every 4 days. For the first, middle and last mixing periods, samples of drinking water at each dose level were taken from the animal room water bottles on the last day of use and analyzed form sodium cyanide. Five of 15 animal room samples for rats and 11 of 15 animal rooms for mice were more than 10% lower than the theoretical concentrations. This was thought due to volatilization. Results of referee analyses performed by Midwest Research Institute were in agreement with study laboratory results.
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
daily, 7 days per week.
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 3, 10, 30, 100 and 300 ppm
Basis:
analytical conc.
No. of animals per sex per dose:
10
Control animals:
other: given water, but there is no information about whether the pH was adjusted to 8.5, as with cyanide groups.
Details on study design:
See discussion 7.5.1.2.
The pH of the water with test material was 8.5.

Examinations

Parental animals: Observations and examinations:
Clinical signs, food and water consumption values, haematology, clinical chemistry and urinalysis.
Oestrous cyclicity (parental animals):
Vaginal cytology according to Morrissey et al, 1988, were used to determine estrous cycle stage.
Sperm parameters (parental animals):
Sperm motility, spermatid counts and sperm head counts
Postmortem examinations (parental animals):
haematology and clinical chemistry, body weight, organ weights (absolute and relative), histopathology.
Statistics:
Arcsine transformations were used on data expressed as proportions. Multivariate analysis of vaginal cytology data was performed. Other measures were analyzed with analysis of continuous variables by Williams (1971) or Dunnett (1955).

Results and discussion

Results: P0 (first parental animals)

General toxicity (P0)

Clinical signs:
no effects observed
Description (incidence and severity):
No treatment-related clinical signs attributable to NaCN were seen in rats or mice.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Mean body weight at necropsy was decreased compared to controls in the 300 ppm dose group in rats.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Mean body weight at necropsy was decreased compared to controls in the 300 ppm dose group in rats.
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Female rats and mice: increased absolute and relative liver weights (300 ppm); male mice: increased relative liver & kidney weights. Male rats and mice: increased absolute testis weight (300 ppm); decreased absolute & relative weight of cauda epididymus
Gross pathological findings:
no effects observed
Description (incidence and severity):
No histological findings.
Histopathological findings: non-neoplastic:
no effects observed
Other effects:
effects observed, treatment-related
Description (incidence and severity):
Test substance intake: Water consumption by all rats and mice in the 100 and 300 ppm groups was less than that by the controls.

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:
effects observed, treatment-related
Description (incidence and severity):
Female rats at 100 and 300 ppm spent significantly more time in proestrus and diestrus compared with controls. No effects were observed in mice.
Reproductive function: sperm measures:
effects observed, treatment-related
Description (incidence and severity):
Male rats and mice: decreased absolute testis weight (300 ppm); decreased absolute & relative weights of cauda epididymus. In rats only, decreased sperm motility at all doses; decreased sperm heads at 300 ppm.
Reproductive performance:
no effects observed

Details on results (P0)

Reproductive findings in males after exposure to oral NaCN include a mild but significant decrease in sperm motility in rats at all dose levels, but not in mice. In high dose male rats and mice (300 ppm), there was a significant decrease in the absolute weight of the epididymis and cauda epididymus, along with decrements in spermatid head counts/testis. In rats at the high dose, there was also a significant absolute decrease in the weight of the testis. U.S. EPA, in 2009, obtained additional data on individual animals, and determined that relative cauda epididymis weight was significantly decreased at all dose levels in both rats and mice. Relative weight changes in the testis and epididymis of rats were not significantly different from control values. Authors indicate that sperm motility values are within the range of normal values reported by other laboratories, and are likely insufficient to decrease fertility. Similarly, the observed changes in oestrus cycle in females was not dose-related, and could be spurious.
Examination of the details of the study supports the proposition that physiologically significant water restriction occurred in the study, leading to the observed minor reproductive effects including effects in the cauda epididymus which is the site of maturation of spermatids. These potentially represent nonspecific dehydration and stress effects, which can be considered adaptive and may be considered in the NOEL determinations, but not NOAEL determinations.

Effect levels (P0)

open allclose all
Dose descriptor:
LOEL
Remarks:
Rat: cauda epididymal weight
Effect level:
ca. 30 ppm (analytical)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: Authors indicate that this weight decrease is minimal. This is typically seen under conditions of dehydration and stress, and can be considered an adaptive rather than an adverse effect.
Dose descriptor:
NOAEL
Remarks:
Rat: sperm motility
Effect level:
ca. 0 ppm (analytical)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: see 'Remark'
Remarks on result:
not determinable
Remarks:
no NOAEL identified
Dose descriptor:
LOEL
Remarks:
Rat: prolonged pro-oestrus and dioestrus
Effect level:
ca. 30 ppm (analytical)
Based on:
test mat.
Sex:
female
Basis for effect level:
other: No dose-response relationship was evident; possibly spurious.
Dose descriptor:
NOAEL
Remarks:
Rat
Effect level:
100 ppm (analytical)
Sex:
male
Basis for effect level:
other: No adverse effect level is 100 ppm, equivalent to 12.5 mg CN ion/kg bw/day, as body weight changes occurred at the higher dose of 300 ppm. Effects could be impacted by decreases in water consumption.
Dose descriptor:
NOEL
Remarks:
Mouse: Cauda Epididymis weight
Effect level:
30 ppm (analytical)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: Relative cauda epididymis weight was decreased in rats given 100 ppm, compared to controls , equivalent to 8.6 mg CN-/kg bw/day. Authors believe these effects to be mild.
Dose descriptor:
NOAEL
Remarks:
Mouse
Effect level:
300 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: see 'Remark'

Overall reproductive toxicity

Reproductive effects observed:
not specified

Any other information on results incl. tables

Water consumption was reduced at 100 and 300 mg/l, up to a 40% decrease. Corresponding decreases in urine excretion and increases in urine specific gravity were reported in rats. A significant decrease in body-weight gain was observed in male rats and a nonsignificant decrease in final mean body weight in female mice exposed to 300 mg/l NaCN, but no such decrease was seen in female rats or male mice. Minor effects judged to be insignificant physiologically were observed in male reproductive parameters. The left and caudal epididymal weights of all male rats and the 300 mg/l male mice were significantly lower than those of the controls. In rats receiving 300 mg/l NaCN, the left epididymal and testis weights and the number of spermatid heads per testis were also lower than in the controls. Sperm motility in all exposed male rats was less than in the controls, but the changes were in the range of normal values reported from different laboratories. In mice, no changes in sperm motility were observed. Pro-oestrus and dioestrus time was prolonged in female rats of the 100 and 300 mg/l groups compared to controls, without a clear dose-related response. No such effects occurred in female mice. NOAELs of 100 ppm for rats and 300 ppm for mice can be derived from this study. According to the authors, the effects on pro-oestrus and dioestrus time cannot unequivocally be attributed to cyanide exposure. Decreases in the weight of the cauda epididymis and the testes, as well as decreases in sperm motility, are consistent with dehydration and stress, and may not be causally associated with exposure to CN anion.

Potassium cyanide and sodium cyanide can be considered as a chemical category, along with hydrogen cyanide (HCN) and acetone cyanohydrin (ACH, also known as 2-hydroxy-2-methylpropanenitrile), based on structural similarity, similar physico-chemical properties and common breakdown/metabolic products in physical and biological systems. Particular attention is paid to the dissociation constant of HCN. In the vast majority of physiologic conditions, the cyanide salts will dissolve in water to form hydrogen cyanide. The physico-chemical hazards and toxicity result from the activity of this common proximal toxicant, HCN.An ECETOC Task Force, in the 2007 ECETOC Joint Assessment of Commodity Chemicals ( JACC ) Report No. 53, “Cyanides of Hydrogen, Sodium and Potassium, and Acetone Cyanohydrin (CAS No. 74-90-8, 143-33-9, 151-50-8 and 75-86-5)” supports the development of this chemical category. Hydrogen cyanide (Index No.006-006-00-X) and salts of hydrogen cyanides (Index No.006-007-00-5) are both listed in Annex VI,Table 3.1 of Regulation (EC) No. 1272/2008, entry 006-007-00-5, and are restricted in comparable ways taking into account physical characteristics. Thus, the assignment of potassium cyanide and sodium cyanide to a chemical category does not result in a less protective regulatory status.

Applicant's summary and conclusion

Conclusions:
NaCN was applied via drinking water to F344 rats and B6C3F1 mice for 13 weeks. At the highest dose level (300 ppm) rats absorbed an average dose of 12.5 mg CN ion/kgbw/d, and mice absorbed an average dose of 26.5 mg CN ion/kgbw/d. Survival and bodyweight at this dose were similar to that of the control group. No effects were observed in thyroid structure or function. No changes in gross or microscopic histopathology occurred in testes, epididymis or ovaries. Caudal epididymis weight was significantly reduced (absolute and relative) in treated rats , and sperm motility was decreased in all dose levels. In rats receiving 300 mg/l NaCN, the left epididymal and testis weights and the number of spermatid heads per testis were also lower than in the controls. These finding can be explained by decreased water consumption due to palatability issues, dehydration and stress. Pro-oestrus and dioestrus time was prolonged in female rats of the 100 and 300 mg/l groups compared to controls, without a clear dose-related response. According to the authors these effects cannot unequivocally be attributed to cyanide exposure. A NOAEL of 100 mg/l for rats (equivalent to 4.9 mg CN ion/kgbw/d) and 300 mg/l in mice (equivalent to 26.5 mg CN ion/kgbw/d) can be derived from this study. Other studies are available which provide relevant information on rats where water intake was matched with animals consuming cyanide salts in drinking water (Leuschner, et. al., 1989).
iets fumigated with HCN .The dietary concentrations were 100 and 300 mg/kg. The animals did not accept higher concentrations due to reduced palatability. Survival, body-weight gain, food intake, and clinical behaviour were not different between treated and control groups in the two year study. Absolute and relative organ weights were also comparable to controls. No treatment-related histopathological changes were observed in the organs examined. The NOAEL in this study was approximately 8.2 mg HCN/kg bw/d, or 7.9 mg CN ion/kg bw/d.