Toluene-2-sulphonamide

Endpoint summary

Description of key information

o-TSA has been tested in a combined repeated dose/reproduction screening test (OECD 422). The NOAEL was established at 20 mg/kg bw/d. The major effects of this chemical were clinical signs such as decreased locomotor activity and prone position, and histopathological change in liver observed at 100 mg/kgbw/d and higher.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental screening

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Original report in Japanese, but translation and OECD SIDS reporting are sufficient and trustworthy. Study has been assigned 'valid without restriction' following OECD SIDS evalauation with peer review.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

Sprague-Dawley lineage (Crj:CD, SPF) from Atsugi Breeding Center of Charles River Japan, Inc.
7-week-old male and female
Acclimatisation: 6 days
Weight at study initiation: 333.1±7.4 g for males, 216.3 ± 6.2 g for females
Housing: individually in a metal wire netting floor cage (22×27×19mm, Japan Cage Co., Ltd.)
Housing: Room temp: 24±1℃, relative humidity 50-65%, Air changes 15 times/hour, 12-hour lighting
Feed|: Ad libitum; solid feed (CE-2, CLEA Japan, Inc.) and tap water.
For females later than 14 days of pregnancy pulp and paper chips (ALPHA-dri, Kasho Co., Ltd.) were provided as bedding.

Route of administration:

oral: gavage

Vehicle:

other: 5% solution CMC

Details on oral exposure:

Test substance was administrated dissolved in an 5% (w/v) CMC solution and administered at a volume of 5 mL/kg bw.
Dose levels were selected following a 14-day range finder at 0, 125, 250 and 500 mg/kg bw with 5 animals/sex/dose. This showed at 500 mg of decreased food intake and BW gain, positive reaction of occult blood in urine, increase in the weight of liver and kidney. A tendency of sedation, including a mild decrease in locomotor activity was observed.

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

Males; for 42 days
Females; from 14 days before mating to day 3 of lactation

Frequency of treatment:

Daily, between 9 and 12 o'clock.

Remarks:

Doses / Concentrations:
0(vehicle), 20, 100, 500 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

13/sex/group

Control animals:

yes, concurrent vehicle

Details on study design:

Section: Animals were kept away from feed for approximately 18-24 hours until they were let to bleed to death under deep pentobarbital anesthesia for autopsy

Observations and examinations performed and frequency:

Clinical signs: daily

BW: weekly and on the day of dissection; in females also on 0 and 4 days after delivery
Food Consumption measured at same day as BW; not during mating period.

Urinalysis: In males on day 42, urine was collected following 4 hrs in metabolic cages, for evaluation of pH, presence and extent of occult blood, protein, sugar, urobilinogen, ketone bodies, bilirubin.

Full Haematological and biochemical examination in males.

Full autopsy. Weight of Organs and Histopathological examinations

Fertility indices:
- Mating period: maximum 14 days. Confirmation of mating completion was done by checking for the existence of sperm in vaginal plug and vaginal semen = day 0 of pregnancy. Calculated are:
- Time until mating,
- Mating rate [(number of copulated animals / number of animals kept in couples)×100],
- Conception rate [(number of pregnant animals / number of copulated animals)×100]
- Gestation period: number of days from day 0 of pregnancy to the day of delivery
- Birth rate [(number of females with live pups / number of pregnant females)×100].

Pups:
Pups observed daily and checked for mortality
Number of pups (viable pups + dead pups) on the day 1
Delivery rate [(number of pups / number of implantation sites)×100]
birth rate [(number of pups born / number of implantation sites)×100]
Sex ratio
Macroscopic malformations
Viability rate [(number of live pups /number of pups born)×100] on day 1
Viability rate [(number of live pups on day 4 / number of live pups on day 1)×100] on day 4
Weight (litter weight) of each litter was measured on days 1 and 4 to calculate [litter weight / number of pups weighed] for each litter
All pups were killed under deep ether anesthesia on day 4 of nursing to perform autopsy. Macroscopic observation was carried out on external and internal organs.

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Critical effects observed:

not specified

1) Mortality, moribund sacrifice and clinical signs

Males: There were no deaths or moribund sacrifice in any dose group. As changes in clinical signs, animals dosed 100mg/kg or more showed decrease in locomotor activity and prone position after initiation of administration, and salivation was observed from the mid period of administration. All these signs, however, disappeared by the next morning. Moreover, as changes unrelated to the test compound, loss of fur was observed in the control and 500 mg/kg groups. No abnormality was seen in the 20 mg/kg group.

Females: Three animals died on Day 3 of administration and two each animals were sacrificed in moribund condition on Days 3 and 5 of administration at 500 mg/kg. All these animals had shown decrease in locomotor activity and prone position at the first administration, but the signs disappeared by the next day. As the administration was repeated, however, the recovery of signs became worse, and animals found dead or sacrificed in moribund condition after showing sedation, reddish tear, dyspnoea, lacrimation and chromaturia. Among survivors animals, signs such as decrease in locomotor activity and prone position, which were seen in the animals found dead or sacrificed in moribund condition, were observed after administration at 100 mg/kg or more. In the 100 mg/kg group, prone position was observed sporadically and all the animals made a recovery by the next day. In the 500 mg/kg group, however, there appeared cases showing waddling gait or extension of extremities and signs such as sedation, subnormal body temperature, reddish tear and brown urine, which were seen in the animals died or sacrificed in moribund condition. At the beginning of administration, there were cases in which the signs appearing after administration of the day before persisted, such as decrease of locomotor activity and prone position. Salivation began to be seen transiently mainly after administration and appeared also in the 100 mg/kg group at the time when the serious signs as above were not observed in the 500 mg/kg group any more. Loss of fur, which was unrelated to the test compound, was observed in the 100 mg/kg group.

No abnormal finding of clinical signs was noted at 20 mg/kg.

 

2) Body weight and food consumption

Males: Significant decrease, when compared with the control values, was observed for body weight of Days 8 -22 of administration and for food consumption of Days 1-8 and Days 8-15 of administration in the 100 mg/kg group, and significant decrease was also observed for body weight of Days 8- 42 of administration and for food consumption of Days 1-8 of administration in the 500 mg/kg group (p<0.01,p<0.05). In the 20 mg/kg group, there was no significant difference from the control value either for the body weight or for the food consumption.

 

Females: At the beginning of administration before mating, significantly lower values, when compared with the control values, were recorded for the body weight on Day 8 of administration and for the food consumption on Days 1-8 of administration at 500 mg/kg (p<0.01, p<0.05). During the gestation and lactation periods, the body weight gain at 100 mg/kg or more was suppressed, with the body weight on Day 7of gestation and on Day 4 of lactation being significantly lower than the control values (p<0.01, p<0.05). In the 500 mg/kg group, the food consumption was also significantly decreased, when compared with the control group, on Days 0-7 of gestation (p<0.05). In the 20 mg/kg group, no significant difference was noted for any period.

 

3) Urinalysis

(males only) In the 20 and 100 mg/kg groups, there were 2 and 1 cases of occult blood positive, respectively. These cases were judged to be unrelated to the administration of test compound, however, since there were no positive cases both in the control and 500 mg/kg group. For other parameters, no animal in any dose group showed abnormality.

 

4) Examinations at necropsy

A. Males

(1) Haematology

When compared with the control group, significantly higher values were obtained for MCH in all the groups given o-toluenesulfonamide and for MCHC in the groups given 100 mg/kg or more (p<0.05, p<0.01). In addition, the platelet count at 500 mg/kg was significantly higher than that of the control group (p<0.05). The clotting time w as significantly shortened at 100 mg/kg or more when compared to the control (p<0.05), because some control animals showed a relatively prolonged PT. For APTT, there was no significant difference when compared with the control group. There were no effects of test compound for any of the remaining parameters and for the differential white blood cell count.

 

(2) Blood chemistry

ALP values were significantly lower than the control values in all the treatment groups (p<0.01). Total cholesterol level was significantly increased at 100 mg/kg or more when compared to the control (p<0.05, p<0.01). In the 500 mg/kg group, total protein and Gamma-GTP activity showed, though being a minor difference, a significant increase when compared to the control (p<0.05) and glucose level, triglyceride level and A/G ratio showed significantly lower values (p<0.05, p<0.01). For the remaining parameters, there was no significant difference between each treatment group and the control group

 

(3) Necropsy

Changes associated with the administration of the test compound were as follows: liver, darkness at 100 mg/kg or more and swelling at 500 mg/kg; kidney, swelling and darkness at 100 mg/kg or more.

 

(4) Organ weight

For the body weight at necropsy, significant lower values than in the control were obtained at 500 mg/kg (p<0.01). When viewed by organ, the liver and kidney weights at 500 mg/kg showed a significant increase when compared with the control (p<0.05, p<0.01). The liver and kidney weight ratio to the body weight was significantly increased at 500 mg/kg and 100 mg/kg or more, respectively. The adrenal weight ratio to the body weight was significantly increased at 100 mg/kg or more (p<0.05, p<0.01). At 100 mg/kg or more, although there were some significant differences in the organ/body weight ratio for the heart and testis (p<0.05, p<0.01), their absolute weight did not show any dose-dependent changes. At 20 mg/kg, no significant difference was noted for the organ weight or organ/body weight ratio.

 

(5) Histopathology

There were dose-related findings in the liver and kidney. There were no abnormal changes in the brain, thymus, heart, adrenal gland and femoral bone marrow.

 

(Liver) At 100 mg/kg or more, hypertrophy of the centrilobular hepatocytes with the cytoplasm having an ground glass appearance was observed in a dose-dependent manner (p<0.01).

 

(Kidney) Although eosinophilic bodies were observed in all the groups including the control, the incidence and severity were significantly higher in the treatment groups than in the control (p<0.01). Although the kidney having eosinophilic bodies was PAS -stained, no positive reaction was obtained.

 

B. Females

(1) Necropsy

All the animals found dead during the course of the study showed retention of pleural effusion and redness or dark-reddish area in the lung, which was accompanied by incomplete involution, oedema and adhesion to the diaphragm with white materials attached. Moreover, these animals showed whitish cortico-medullar border in the kidney, opaque left eyeball, swelling of the liver, pale discoloration of the glandular stomach mucosa, yellowish area in the glandular stomach mucosa, reduced size and pale discoloration of the spleen. Animals sacrificed in moribund condition, all showed retention of pleural effusion, pulmonary oedema and redness or reddish area, with the lung adhered to the costal pleura and diaphragm in some cases. Other than these, changes such as redness or pale discoloration of the cortico-medullar border in the kidney, opacity of the thymus, pale discoloration of the liver, reduced size and pale discoloration of the spleen, and yellowish area in the glandular stomach mucosa were observed. For animals died or sacrificed in a moribund condition, the oesophagus which had been removed, and stored together with the abnormal lung was examined for the second time after histopathological examinations. As a result, perforation or reddish area was observed under the adventitia along the oesophagus. Animals examined by periodic necropsy showed the following changes which were related to administration of test compound: the liver swelled at 100 mg/kg or more and darkness at 500 mg/kg; the lung adhered to the costal pleura and pale-discoloured spots or areas at 100 mg/kg or more, adhered to the diaphragm and dark red spots or areas at 500 mg/kg. Moreover, the lung of the 100 mg/kg group adhered to costal pleura also showed attachment of yellowish white mass at the adhesion site.

 

(2) Organ weight

The body weights at necropsy of animals receiving 100 mg/kg or more were significantly lower than the control value (p<0.05, p<0.01). Although the absolute weight ofeach organ did not show any significant difference between each treatment group and the control, the organ/body weight ratio increased significantly with increasing tendency of the absolute weight for the liver at 100 mg/kg or more (p<0.01) and for the kidney (p<0.05) and adrenal gland (p<0.01) at 500 mg/kg. For the brain at 500 mg/kg, although the ratio to body weight was significantly higher (p<0.05) than in the control group, its absolute weight was not increased.

 

(3) Histopathology

For the liver, kidney, spleen, heart, thymus and urinary bladder, the following findings were noted. There were no abnormal findings, however, for the brain, adrenal gland, femoral bone marrow and the ovary of sterile females. Although the organs with abnormality observed at necropsy were examined, no abnormal change was detected. Moreover, after histopathological examinations, some animals (1 and 3 animals at 100 and 500 mg/kg, respectively) including one animal having a perforation were subjected to the second histopathological examinations, which resulted in additional findings in the oesophagus, heart, thymus and lung. In the animals subjected to the second examinations, however, the pancreas (one each animal of the control and 100 mg/kg groups) and thyroid (1 and 3 animals at 100 and 500 mg/kg, respectively) showed no abnormal change.

 

(Liver) Hypertrophy of centrilobular hepatocytes with cytoplasm of ground glass appearance was observed in a dose-dependent manner in the groups receiving 100 mg/kg or more (p<0.01). At 500 mg/kg, this finding was noted in all the animals subjected to scheduled sacrifice but not noted in the animals necropsied in the mid-course of study (cases of death or moribund sacrifice).

 

(Kidneys) Since vacuolation probably due to fat deposition was observed on the proximal uriniferous tubules of four animals in the 500 mg/kg group, these animals were subjected to the oil red O-staining by using one control animal as the control; the vacuoles proved to be fatty degeneration. Its incidence was significantly higher than in the control group (p<0.05). This change was observed mainly in the animals examined by mid-course necropsy and for animals examined by scheduled necropsy, there was no significant difference from control animals.

 

(Spleen) At 500 mg/kg, the white and red pulps were found to be atrophied, with the incidence being significantly higher than the control group (p<0.05). Atrophy of the white pulp was observed mainly in animals examined by the mid-course necropsy. Atrophy of the red pulp was not observed in animals of scheduled necropsy but observed in all the animals of mid-course necropsy. When its incidence in animals of scheduled necropsy was compared to that in the control group, therefore, significant difference was not detected any more.

 

(Heart) At 500 mg/kg, fibrosis and cellular infiltration of the epicardium were noted in the animals subjected to scheduled necropsy. Cellular infiltration into the epicardium was observed also in the animals subjected to the second histopathological examination at mid-course necropsy. The incidence was significantly high, when compared to the control, both when only animals of scheduled necropsy were analyzed and when all the animals of the 500 mg/kg group were analyzed (p<0.05).

 

(Thymus) At 500 mg/kg, atrophy of the thymus was observed in animals examined by mid-course necropsy and periodic necropsy. Its incidence was significantly (p<0.05, p<0.01) higher than in control animals both when only animals of scheduled necropsy were analyzed and when all the animals of the 500 mg/kg group were analyzed. At 100 mg/kg or more, fibrosis, oedema and cellular infiltration of the capsule as well as exudate containing neutrophils on the capsule were observed. The incidence of these findings at 500 mg/kg was compared with that in the control group. In the case when all the animals were analyzed, significantly (p<0.05, p<0.01) higher values were obtained for oedema and cellular infiltration of the capsule, and when the animals subjected to scheduled necropsy were analyzed, significantly (p<0.05) higher values were obtained for fibrosis and cellular infiltration. In the 100 mg/kg group, there was no significant difference from the control group.

 

(Organs showing abnormal changes at necropsy) At 500 mg/kg, very slight to slight focal haemorrhage and infiltration of neutrophils and lymphocytes in the lung were observed both in animals of midcourse necropsy and those of kill on schedule. In the cases of mid-course necropsy, very slight to moderate oedema and infiltration of macrophages as well as exudate containing neutrophils on the pleura were noted. There were also the cases in which foreign materials were mixed with the exudate. In animals of kill on schedule at 100 and 500 mg/kg, very slight to slight aggregation of foamy cells as well as slight to moderate fibrosis of the pleura was observed. In animals of mid-course necropsy at100 and 500 mg/kg, very slight to moderate cases of cellular infiltration into the pleura were observed. Other than these cases, moderate foreign granuloma was observed on the pleura at 100 mg/kg. Of two animals of mid-course necropsy subjected to additional histopathological examinations, one animal showed in the oesophagus slight perforation, degeneration of the mucosa and muscular layers and infiltration of neutrophils, and moderate haemorrhages under the adventitia of oesophagus and in the pleura. For the other animal, although histopathological examinations did not reveal any abnormal change in the site with miniscule perforation noted macroscopically, exudate containing neutrophils as well as foreign matters was noted on the pleura. Moreover, slight cellular infiltration was observed on the pleural plane of the diaphragm, accompanied by slight exudate containing neutrophils.

Conclusions:

o-TSA has been tested in a combined repeated dose/reproduction screening test (OECD 422). The NOAEL was established at 20 mg/kg bw/d. The major effects of this chemical were clinical signs such as decreased locomotor activity and prone position, and histopathological change in liver.

Executive summary:

OECD 422, Combined Repeat Dose and Reproductive/Developmental Toxicity Screening Test in rat by gavage under GLP. Dose levels: 0 (vehicle, 5% CMC), 20, 100, 500 mg/kg bw/day, with 13 animals per dose group per sex. Dosing period: Females, from 14 days before mating to day 3 of lactation. Males were treated for 42 days.

Three females died and two females were sacrificed in moribund condition during the pre-mating period at 500 mg/kg bw, but no males were found dead or moribund in any group. Decreased locomotor activity and appearance of prone position and salivation were observed in both sexes at 100 and 500 mg. In these groups, significantly low body weights were recorded in both sexes. Blood chemical examination in males showed an increase in total cholesterol at 100 mg or more, and a decrease in glucose and triglyceride at 500 mg. Relative liver weight of males at 500 mg and of females at 100 and 500 mg, and relative kidney weight of males at 100 and 500 mg and of females at 500 mg were significantly increased. In histopathological examinations, hypertrophy of the centrilobular hepatocytes with the cytoplasm having a ground glass appearance was observed in both sexes at 100 and 500 mg. In the kidneys, increased incidence and severity of eosinophilic body was observed in males of all treated groups. Very slight diffuse hyperplasia of the bladder epithelium was seen in one male at 100 mg and in 2 males at 500 mg. In addition, the incidence of fibrosis and cellular infiltration of the pericardium, and fibrosis and cellular infiltration of the capsule and atrophy of the thymus were significantly increased in females at 500 mg. Renal change observed in male rats may be due to the complex accumulation of this chemical with the male rat specific protein, alpha-2u-globulin, although no direct evidence is given. Therefore, the NOAEL for repeated dose toxicity is considered to be 20 mg/kg bw/day for both sexes, based on clinical signs and hepatic change.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

20 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Multiple studies available, including lifelong, that are adequate for use for hazard evaluation.

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

Repeated dose - by oral route

Available data: There is one study available for evaluation on o-TSA itself. Additionally, cross-reading to p-TSA is possible (See document in support of cross-reading). Additional supportive information can be derived from chronic studies reported in literature.

 

Available data on o-TSA:

OECD 422, Combined Repeat Dose and Reproductive/Developmental Toxicity Screening Test in rat by gavage under GLP. Dose levels: 0 (vehicle, 5% CMC), 20, 100, 500 mg/kg bw/day, with 13 animals per dose group per sex. Dosing period: Females, from 14 days before mating to day 3 of lactation. Males were treated for 42 days.

Three females died and two females were sacrificed in moribund condition during the pre-mating period at 500 mg/kg bw, but no males were found dead or moribund in any group. Decreased locomotor activity and appearance of prone position and salivation were observed in both sexes at 100 and 500 mg. In these groups, significantly low body weights were recorded in both sexes. Blood chemical examination in males showed an increase in total cholesterol at 100 mg or more, and a decrease in glucose and triglyceride at 500 mg. Relative liver weight of males at 500 mg and of females at 100 and 500 mg, and relative kidney weight of males at 100 and 500 mg and of females at 500 mg were significantly increased. In histopathological examinations, hypertrophy of the centrilobular hepatocytes with the cytoplasm having a ground glass appearance was observed in both sexes at 100 and 500 mg. In the kidneys, increased incidence and severity of eosinophilic body was observed in males of all treated groups. Very slight diffuse hyperplasia of the bladder epithelium was seen in one male at 100 mg and in 2 males at 500 mg. In addition, the incidence of fibrosis and cellular infiltration of the pericardium, and fibrosis and cellular infiltration of the capsule and atrophy of the thymus were significantly increased in females at 500 mg. Renal change observed in male rats may be due to the complex accumulation of this chemical with the male rat specific protein, alpha-2u-globulin, although no direct evidence is given. Therefore, the NOAEL for repeated dose toxicity is considered to be 20 mg/kg bw/day for both sexes, based on clinical signs and hepatic change.

 

These results were later confirmed in an additional 28-day study also performed by Hatano Research Institute, Food and Drug Safety Center in Japan (available at http://dra4.nihs.go.jp/mhlw_data/jsp/SearchPageENG.jsp, not included in this dossier). In this 28-day study 5 rats(Crj:CD(SD)IGS)/sex/dose were treated with 0 (vehicle: 0.5% CMC solution), 4, 20 and 100 mg/kgbw/d by gavage. An additional group of 5 animals/sex/dose were added to control and high dose groups for a 14-day recovery period.

No deaths occurred. At 100mg observed effects included: clinical signs involved salivation reduced activity following dosing observed from second week, and hunched posture in one male; a slightly decreased BW (statistically significant in females); At necropsy there was a tendency of increased eosinophilic bodies in the epithelial cells of renal proximal tubules of males. In females there was a tendency of a higher pH in the urine. Based on these observations the NOAEL was set at 20 mg/kgbw/d.

 

Further relevant is a two generation lifetime feeding study (Arnold et al, 1980; see chapter 7.7 carcinogenicity). SD rats were given o-TSA in the diet at 0, 2.5, 25, 250 mg/kg/day, or 250 mg/kg/day with 1% NH4Cl in drinking water. NH4CI was added to the drinking water of one o-TSA-treated group, to prevent the formation of alkaline urine.The first generation (F0) was treated from 32 days of age for 142 weeks, and the second (F1) generation was treated from 21 days (weaning from treated parents) of age for 127 weeks.The time-to-death for parental animals was not affected by treatment, although the average adult body weights for parental animals were significantly lower in the 250 mg/kg group than that in the control group.

 

 

For evaluation of repeated dose toxicity cross-reading to p-TSA can be done. (see document Justification in support of cross-reading between Toluenesulphonamides). Included in this dossier is a 90-day study of p-TSA.

Following a 28-day range finding study a 90-day oral study in rat with dosing by dietary admixture (OECD 408) was performed, applying dose levels of 0, 1000, 3000 and 10.000 ppm were, equivalent to an average intake of 0, 70, 214 and 738 mg/kg body weight/day for males, and 0, 80, 248 and 795 mg/kg body weight/day for females.

Results: At 10.000 ppm, a significant and consistent reduction of body weight gain was recorded (up to 21% compared to control animals). Histopathology revealed a minimal degree of hyperplasia of the urothelium of the urinary bladder in two males at 10.000 ppm.

No other treatment-related toxicologically significant changes were noted in any of the remaining parameters examined/determined in this study (i.e. clinical appearance, functional observations, food consumption, clinical laboratory investigations, macroscopic examination and organ weights).

 The observed minimal urethelial hyperplasia in two animals seems to be caused by local irritation by the chronic of p-TSA metabolite (p-sulphamonylbenzoic acid) in the urine, following the rapid and complete excretion of p-TSA. Such effect is local and fully reversible when exposure ends. As the hyperplasia is observed in only two animals, is minimal and likely a fully reversible temporal effect upon exposure, it is not considered an adverse effect persé. The reduction of the body weight gain of 21% in males is considered serious enough to assign the 10000 ppm a LOAEL, especially as a relation to palatability is not completely clear.

LOAEL: 10.000 ppm (738 mg/kg/day for males, or 795 mg/kg/day for females).

NOAEL: 3000 ppm (214 mg/kg/day for males, or 248 mg/kg/day for females).

 

However, a 2-generation study with p-TSA of similar quality indicated effects of reduced body weight especially in pregnant and lactating animals from 3000 ppm, resulting to a NOAEL of 1000 ppm, equivalent to 52 -78 (average 65) mg/kg bw/day for males and 75-161 mg/kg bw/day for females. Also a recent developmental study mentions transient effects at 3000 ppm, and no effects at 1000 ppm. Hence the overall NOAEL for p-TSA was set toNOAEL = 65 mg/kg bw/day.

 

 

Evaluation:

Both toluenesulphonamides show a comparable toxicokinetics pattern. Following rapid absorption and excretion in urine, the concentrations of (metabolites of) the TSA substances is highest and longest present in the urinary tract, where therefore the toxic effects are first seen. Information available on benzenesulphonamides supports a common mechanism of action for toxicity to urinary tract observed in repeated dose studies with these compounds. The effect is indirect mediated by the appearance of calcium phosphate calculi caused by induced alkaline urine.

It seem that studies based on dosing by gavage result to lower NOAEL levels compared to studies involving dietary admixture. The differences between these studies can be explained by the differences in kinetics leading to higher peak concentrations resulting to subsequent higher urinary concentrations.

 

Based on the above data, the overall NOAEL is set to 20 mg/kgbw/d, being the lowest value obtained following repeated dosing by gavage.

 

Repeated dose – by inhalation

vp is 0.000066 Pa at 25°C, and the respirable fraction (≤ 4 µm) of the crystalline solid is 0.23%. In combination of low likelihood of exposures by aerosols from the use of the substance (also water solubility is low: 1.6 g/L at 20°C), the limited local effects, and the quick complete absorption, distribution and excretion which can also be expected for the inhalation route, do not make additional testing by inhalation of high priority.

 

Repeated dose – by dermal route

Substance is of low acute oral toxicity, not requiring classification. Also no classification is required for skin or eye irritation. Information on absorption indicates that o-TSA is rapidly and completely absorbed by oral route, but only 20% by dermal route. Further testing by dermal route is therefore scientifically unjustified.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Although not the study with longest duration, it represents the lowest NOAEL.

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
Justification: Testing by the inhalation route is not appropriate since exposure of humans via inhalation is not likely taking into account the vapour pressure of the substance and/or the possibility of exposure to particles or droplets of an inhalable size. The vapour pressure is very low ((0.000066 Pa at 25°C), inhalable and respirable fraction low (0.23% with particle size ≤4µ) and the pattern of use does not lead to the formation of droplets of an inhalable size. In addition the substance is of general low toxicity and not irritating. Testing by inhalation is therefore not necessary.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
Information on absorption indicates that o-TSA is rapidly and completely absorbed by oral route, but only 20% by dermal route. Dermal route is therefore not the optimum route for testing.

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

Justification for classification or non-classification

Available studies do not indicate a need for classification for STOT-RE. o-TSA is of limited toxicity at levels of 100 mg/kg bw/day and below. Effects at this level involved some clinical signs and increased relative liver weight. Levels of 250 mg/kgbw/d were tolerated well in a lifelong study.