5-Isothiazolecarboxamide, 3,4-dichloro-N-(2-cyanophenyl)-

Endpoint summary

Description of key information

NOAEL oral subchronic toxicity = 29.7 mg/kg bw/day (males) and 35.1 mg/kg bw/day (females)
NOAEL oral subacute toxicity = 279 mg/kg bw/day (females)
NOAEL dermal subacute toxicity = 1000 mg/kg bw/day

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

29.7 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

The available information comprises adequate, reliable (Klimisch score 1-2) and consistent studies, and is thus sufficient to fulfil the standard information requirements set out in Annex VIII-IX, 8.6, of Regulation (EC) No 1907/2006.

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 adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The available information comprises an adequate and reliable study, and is thus sufficient to fulfil the standard information requirements set out in Annex VIII, 8.6, of Regulation (EC) No 1907/2006.

Additional information

Two subacute repeated dose toxicity studies, one subchronic repeated dose toxicity study and a 2 -year carcinogenicity study were performed with the test substance.

In an oral repeated dose study performed according to OECD 407, rats (5/sex/dose) were exposed to 0, 1000, 3000 and 10000 ppm, corresponding to 82.7, 286 and 949 mg/kg bw/d (males), and 111, 279 and 1040 mg/kg bw/d (females) continuously in the feed for 28 days (Kroetlinger, 2003).  

No mortalities occurred and no treatment-related clinical signs were observed.

In all the treated males and the high dose females, a statistically significant increase in relative liver weight and effects on liver enzyme parameters were observed, with general decrease in phase I and induction of phase II enzymes. Since there was no histopathological correlation, this is most probably an adaptation effect of the liver to exposure to the test substance, rather than an adverse effect per se.

A statistically significant decrease in the eosinophil count in females of the high dose group was observed, along with a (not statistically significant) almost 50% reduction in the level of leucocytes, neutrophiles, lymphocytes and monocytes, compared to the control group (see table 1). For the male high dose group, a similar, but smaller reduction (>25%) in white blood cell levels was observed (see table 1). The effect in the high dose group is considered to be a treatment-related effect as the reduction is consistent for most of the blood cell values. 

Table 1

Dose ppm	Eosinophiles 10E9/L	Leucocytes 10E9/L	Neutrophiles 10E9/L	Lymphocytes 10E9/L	Monocytes 10E9/L
Males (n=4)
0	0.07	8.28	0.53	7.37	0.18
10000	0.05	5.77	0.36	5.15	0.12
Females (n=5)
0	0.05	4.72	0.42	4.07	0.11
10000	0.02*	2.39	0.18	2.10	0.06

* p<0.05

Therefore, based on the hematological effects, a dietary concentration of 3000 ppm (corresponding to an average daily test substance intake of 286 mg/kg bw/d for males and 279 mg/kg bw/d for females) is considered to be the no observable adverse effect level (NOAEL) for the test article in this study.

The potential neurotoxicity of the test substance was assessed in the oral repeated dose study (Kroetlinger, 2003), beyond the requirements of OECD 407. In addition to the standard functional observational battery (FOB) with grip strength measurements and associated parameters of behaviour and activity, motor activity and locomotor activity were assessed by testing the rats individually in a figure of eight maze. No effects on neurobehaviour were observed.

Subchronic oral repeated dose toxicity study

In order to evaluate the subchronic toxicity of the test substance, rats were fed with the test substance at dose levels of 20, 500, 2500 and 20000 ppm (corresponding to 1.18, 29.7, 148, 1238 mg/kg bw/day in males and 1.39, 35.1, 178, 1398 mg/kg bw/day in females) for a period of 90 days (13 weeks). The study was performed according to OECC 408 and under GLP conditions. Each dose group consisted of 10 male and 10 female rats. During the treatment period, all animals were checked daily for mortality and general condition. All animals were subjected to functional observation at Week 11 and urinalysis at Week 13. Ophtalmological examination was performed on all animals before initiation of treatment and on all males and females in the control and high dose groups at Week 13. After 13 weeks all animals were subjected to hematological and biochemical examinations, organ weight analysis, and necropsy. Major organs/tissues of animals in the control and the high dose groups and the forestomach in all groups were examined histopathologically.

The following treatment-related changes were found:

20000 ppm group: Males showed a statistically significant decrease in body weight gain from Week 4 to 5 compared to the control group. Overall body weight gain throughout the treatment period (93%) and mean body weight at Week 13 (95%) were slightly lower than in the control group, although there was no statistical significance. Overall mean food consumption (94%) of males was slightly lower compared to the control group. Urinalysis revealed a statistically significant decrease in specific gravity in females. A statistically significant increases in gamma-glutamyl transpeptidase and total cholesterol were observed in males and females. Organ weight analysis revealed statistically significant increases in absolute and relative liver weights in males and females and relative kidney weight in females. Histopathologically, mucosal epithelial hyperplasia in the limiting ridge of the forestomach in 7/10 males and 5/10 females.

2500 ppm: A statistically significant increase in total cholesterol was observed in males and females. The relative liver weight was statistically significantly increased in males and females. The females showed also a statistically significant increase in absolute liver weight.

No treatment-related effects were observed in the 500 and 20 ppm dose group in males and females.

Based on the observed effects on body weight, liver, kidney and forestomach, the NOAEL was considered to be 500 ppm in males (corresponding to 29.7 mg/kg bw/day) and females (corresponding to 35.1 mg/kg bw/day).

The dermal exposure of male and female rats to 100, 300 and 1000 mg/kg bw/day of the test substance was performed in a 28-day study where 21 doses in total were administered (5 days/week) (Eigenberg, 2009).

Three females died during the study, one in the control group (day 24), one in the 300 mg/kg bw/day group (day 1) and one in the 1000 mg/kg bw/day group (day 24). The deaths were considered incidental and were probably due to the wrapping that holds the test substance in place. Skin lesions and scabs that were observed were also due to wrapping the animals with elastic tape. Urine staining that was observed in some females in the treatment groups was due to the dosing procedure. On day 21, the body weight of the females in all treated groups was statistically significantly reduced compared to the control group, but the effect was not observed at any other time point and was therefore considered not to be treatment-related.

Some minor changes in clinical chemistry and haematology values were observed, but none were considered to be treatment-related as they were not consistent in both sexes and/or there were no corresponding histopathological findings. Hepatic microgranuloma was present in several control and treated animals of both sexes, and in females acute necrosis (in some case encapsulated) was observed. The changes were attributed to the tight wrapping around the abdomen of the rats to protect the exposure site.

In females dosed 1000 mg/kg bw/day, there was a significant increase in the absolute (28%) and relative (31%) ovary weights. No macroscopic or microscopic histopathologic changes were observed and data from previous subacute oral and dermal studies indicated the ovarian weight is not unusual. Although the biological significance of the increase in ovarian weight is unclear, there are no indications that it is a treatment-related effect. 

Therefore, the dermal no-observable-adverse-effect level (NOAEL) for the test substance is set at 1000 mg/kg bw/day for both sexes.

No inhalation repeated dose study was available. Because the total particle size distribution of the substance includes inhalable particles, there is a potential for human exposure to the test substance via inhalation. Using the derived no-effect levels (DNELs) and the exposure levels, the risk characterisation ratios (RCRs) were shown to be below 1.

In accordance with REACh Annex XI, 3.1, the repeated dose inhalation dose toxicity study does then not need to be conducted.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
The selected study is the most adequate and reliable study with the lowest dose descriptor.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
The reliable GLP compliant OECD Guideline study was chosen.

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

Justification for classification or non-classification

The available data are conclusive but not sufficient for classification according to the criteria of DSD (67/548/EEC) and CLP (1272/2008/EC).