Sulphamidic acid

Endpoint summary

Description of key information

NOAEL oral = 10000 ppm(equivalent to 1000 mg/kg bw/day) in rat;
LOAEL oral = 20000 ppm(equivalent to 2000 mg/kg bw/day)  in rat.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

March - July 1985

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well documented guideline study performed under GLP

Reason / purpose for cross-reference:

reference to other study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Wistar-Rats (Hoe:WISKf(SPF7l)) from Lab-internal breeding were used, having a medium bodyweight of 98 g/animal at the beginn of the study. Animals were renadomized in 4 groups of 30 males each and 4 groups of 30 females each.
Animals were kept in numbered metal cages Type III and were individually identified by ear marks. The room was kept at 22 ±2 °C with relative humidity of 65 ±10% (16 - 20 air changes per hour). A 12hours light/12 hours dark cycle was maintained throughout study period. Food (Altromin 1321 powder) and tap-water was provided ad libitum.

Route of administration:

oral: feed

Vehicle:

not specified

Details on oral exposure:

The test substance was administered as part of feeding. Feed was mixed as follows: Sulfamic acid was dissolved in boiling demineralised water under constant stirring and this solution was mixed with Atromin 1321 feeding powder. Thereafter the feed mixture was placed in a plystic container to cool off for 24 hours followed by grinding and sieving. Amounts of sulfamic acid and Atromin were selected to achieve the desired feed concentrations (5000, 10000 and 20000 ppm). Feed was prepared freshly once a week and stability of sulfamic acid in feed was confirmed by analysis.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Doses of 5000, 10000 and 20000 ppm were analytically verified and recorded in the raw data of the study.

Duration of treatment / exposure:

3 month exposure plus 4 weeks recovery period

Frequency of treatment:

continuous via feed

Remarks:

Doses / Concentrations:
0, 5000, 10000, 20000 ppm
Basis:
nominal in diet

No. of animals per sex per dose:

30 per sex per dose

Control animals:

yes, concurrent no treatment

Positive control:

none

Observations and examinations performed and frequency:

Behaviour changes, mortality and general clinical parameters were recorded twice daily (on Saturday and Sunday only once daily). Once weekly animals were assessed for neurological effects, eye were examined, teeth growth and oral mucosa changes. Body weigth, food and water consumption were checked once a week.

Sacrifice and pathology:

At end of exposure 20 males and 20 females were sacrificed by narcosis with phenobarbital/sodium, followed by cut-through of the vena cava cranialis. The following organs were isolated and weighed: Heart, liver, lung, kidneys, spleen brain, ovaries, adrenal glands, pituitary gland, thyroid and seminal vesicles. The remaining organs were kept in fixation bath without weighing for pathological examination.

Other examinations:

Hämatological examinations were made after 4 weeks of exposure, at end of exposure period and at the end of the recovery period. Blood samples were taken from 10 animals per group. Urine anaylsis was performed at the same intervals.

Statistics:

Statistics was performed by Dunnett method, Sidak-method and distributed free method by Nemenyi/Dunnett with a level of significance of 0.05. Details are provided in an Appendix covering 26 pages with detailed statistical anylsis in original report.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

no effects at 5.000 and 10.000 ppm but body weight reduction at 20.000 ppm

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Normal at 5.000 and 10.000 ppm but slightly reduced at 20.000 ppm dose group

Food efficiency:

not examined

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

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

changes in urine density

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

unspecific, see details on results

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

See details on results

Histopathological findings: neoplastic:

not specified

Details on results:

No mortality was observed throughout the study, except of one male animal from control group that died on day 14. At 20.000 ppm a third of males showed slightly soft feces.
No effects were seen on body weight development at 5.000 and 10.000 ppm but statistically significant body weight reduction at 20.000 ppm was seen. During recovery phase, the body weight of 20.000 ppm dose group animals returned to normal.
Food consumption was normal at 5.000 and 10.000 ppm but slightly reduced at 20.000 ppm dose group; from day 36-43 food consumption at the 20.000 ppm group was strongly decreased and the study authors assumed an error in food preparation (too much sulfamic acid in food for this week).
No effects on water consumption were noted.
Substance uptake was calculated from medium body weight and feed consumption as follows:
5000 ppm sulfamic acid = 458 mg/kg bw (males) and 499 mg/kg bw (females)
10000 ppm sulfamic acid = 929 mg/kg bw (males) and 1004 mg/kg bw (females)
20000 ppm sulfamic acid = 1928 mg/kg bw (males) and 1992 mg/kg bw (females)
No haematological effects were seen of statistical relevance. Although some parameters appeared statistically relevant in comparisson of dose groups to control groups, it was noted, that these parameters for the controls were out of the historical range and thus these deviations were not dose dependant and considered incidental.
Clinical chemistry parameters changes were sometimes of statistical significance but all values were within the historical range for such animals and changes obersved were often attribuatble to changes in control animals. Thus, from the changes seen, no substance-related effects could be deduced.
The urinanalysis showed a reduction in urine density (females after 4 weeks of exposure and males at the end of exposure period), correlating with reduced pH in the 20.000 ppm dose group only.
Neurological effects (change of tooth growth, changes of eyes and mucosa) were not observed in this study.
Relative organ weight of kidneys, spleen, testis, adrenal glands, hypophysis and seminal vesicle were statistically significant increased but this is attributable to the low body weight development in this dose group. All other changes were considered incidental and not attriutable to treatment with sulfamic acid.
Histologiocal examinations showed no special effects by treatment with sulfamic acid at the low and mid dose group. Only at the 20.000 ppm dose group in 5/20 maes and 15/20 females fat droplets were observed in Henle's slope of the kidneys. The animals sacrificed afterthe recovery period did not show such effects and thus this as considered reversible.

Dose descriptor:

NOAEL

Effect level:

10 000 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male

Basis for effect level:

other: see 'Remark'

Dose descriptor:

NOAEL

Effect level:

1 004 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: see 'Remark'

Critical effects observed:

not specified

At 20.000 ppm delayed growth and slightly reduced food ingestion, as well as weight increase in different relative organs.

Some animals displayed slight fattiness in kidney tubules (completely reversible).

Conclusions:

NOAEL = 10.000 ppm in food corresponds to about 1000 mg/kg bw/day (929 mg/kg bw males and 1004 mg/kg bw females).

Executive summary:

In this well documented guideline compliant GLP study repepated dose toxicity to rats was investigated for 3 month with a 4 weeks recovery period. The substance was applied via feed at doses of 0 (control), 5.000, 10.000 and 20.000 ppm (corresponds to 458, 929 and 1928 mg/kg bw for males and 499, 1004 and 1992 mg/kg bw for females). At 5.000 and 10.000 ppm no effects were seen. The effects observed at 20.000 ppm were non-specific mainly being reduced body weight gain in conjunction with relative weight increase of some organs, slight acidification of urine and fine dropletts of fatty tissue in the upper part of Henle's slope of the kidneys. Consequently, the NOAEL (equivalent to NOEL) was set to 10.000 ppm (i.e. approx. 1000 mg/kg bw) in this study.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

The selected key study findings are supported by two additional studies with sulphamidic acid and two more studies with ammonium sulphamate, all showing comparable results and describing similar symptoms at elevated doses. Thus, the quality of the database is considered very good.

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In total two subchronic oral repeated dose toxicity studies are available and two further subchronic oral toxicity studies on ammonium sulfamate (i.e. neutralized sulfamidic acid). All of these studies were designed as feeding studies, whereas a 14-day range-finder test on sulfamidic acid was dosed by gavage of an aqueous solution of sulfamidic acid and is of limited relevance for assessment of repeated dose toxicity, due to the short exposure period and the limited parameters assessed.

Repeated dose toxicity studies by dermal or inhalation exposure are not available.

The four subchronic feeding studies consistently show that sulphamidic acid and its’ ammonium salt are of low toxicity when dosed over a longer period (90 days and 105 days respectively) and the findings are discussed in more detail here:

Donaubauer et al. investigated the repeated dose toxicity of sulphamidic acid in a GLP-compliant 90-day feeding study with rats (doses of 0, 5000, 10000 and 20000 ppm were applied) and this study is selected as key study. No adverse effects were seen at 10000 ppm in males and females (equivalent to 929 mg/kg bw/d for males and 1004 mg/kg bw/d females). At 20000 ppm only non-specific effects were seen such as slightly reduced body weight gain and increase of some organ weights associated with acidification of the urine. 5 out of 20 male animals and 15 out of 20 females of the high dose group (20000 ppm equivalent to 1928 and 1992 mg/kg bw/d respectively) showed some fine droplets of fatty tissue in the upper part of Henle's slope of the kidneys. Thus, in summary a NOAEL of 1000 mg/kg bw/d is considered justified in this study.

These findings are supported by another feeding study with sulphamidic acid being dosed over 105 days to rats by Ambrose in 1942. Although this study predates GLP and OECD testing protocols and only few details on study design are reported in the peer-reviewed article at that time, the findings reported do correlate very well with those of Donaubauer et al. (see above). Also in this study inhibition of growth rate was the only clinical effect observed at a dose of 20000 ppm and therefore the NOAEL was set to 10000 ppm, which corresponded to approx. 600 mg/kg bw/d in this study (only females were used in this study).

Ambrose also investigated ammonium sulfamate (neutralized sulphamidic acid) in an equivalent study set-up which was performed in parallel to the one above. The doses were kept equivalent to the study with sulphamidic acid based on sulphamidic acid and the finding of growth rate reduction at 20000 ppm were also seen, although not so pronounced as in the study with sulphamidic acid. Consequently, the NOAEL in this study also was set to 10000 ppm (i.e. 600 mg/kg bw/d calculated as sulphamidic acid).

Gupta et al. in 1979 reported about their findings when feeding rats with 0, 100, 250 and 500 mg/kg bw/d ammonium sulphamate over a period of 90 days. In this study female adult rats were exposed but also in parallel weanling male and female rats. No substance related effects were seen in this study, neither with adult female rats nor with weanling male/female rats and thus the NOAEL was set to the high dose group dose (500 mg/kg bw/d). Effects considered non-adverse were a slightly reduced weight gain of adult females but this was not seen with weanling rats. Weanling rats were observed to consume slightly more water in the high dose group and less food, but weight gain development was unaffected. Based on these observations, an influence of ammonium sulfamate on the acid/base balance was assumed.

In a very recent range-finding study, performed as preparation for a reproductive toxicity study with rats, doses of 0, 100, 300 and 1000 mg/kg bw/d sulphamidic acid were dosed to three female rats by gavage (as aqueous solution) over 14 days. One out of three animals was found dead at test day 3 and thus the NOAEL was set to 300 mg/kg bw/d and the doses for the reproductive toxicity test were defined up to 600 mg/kg bw/d. The combination of gastro-intestinal lesions in the ceased animal, application of a strong acid as aqueous solution by gavage, pre-lethal symptoms beginning directly following the first exposure on day 2 (reduced motility, breathing sounds and a haemorrhagic nose/snout) and low number of test animals cannot provide a significant relevance to this finding. However, animals dosed with 300 mg/kg bw/d showed no significant symptoms, supporting the more relevant findings of the subchronic studies above.

In conclusion, sulphamidic acid is considered of low repeated dose toxicity and the study by Donaubauer et al. is selected as key study due to its reliability, supported by the other studies with sulphamidic acid and ammonium sulphamate. The NOAEL of 1000 mg/kg bw/d is taken forward for hazard and risk assessment and the kidneys are chosen as target organ.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
see discussion

Repeated dose toxicity: via oral route - systemic effects (target organ) urogenital: kidneys

Justification for classification or non-classification

Based on the test results, no classification for repeated dose toxicity is proposed for sulphamidic acid according to Regulation (EC) No 1272/2008 of the European parliament and of the council of 16 December 2008 or according to DSD (Directive 67/548/EEC).