N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine

Endpoint summary

Description of key information

Several oral repeated dose toxicity studies were conducted to evaluate the toxicity of the test substance 77PD. In a subacute feeding study with rats (Monsanto Co. 1989) effects on body weight and body weight gain was noted in treated animals. In addition, increases in mean platelet counts and mean erythrocyte counts and alterations in several clinical chemistry parameters were noted in animals of the higher dose groups. In a subchronic feeding study with rats (Monsanto Co. 1989) decreases in body weight and body weight gain were noted in treated animals. Moreover, changes in clinical chemistry were noted in treated animals. In an early two-year chronic feeding study (Monsanto Co. 1978) slight reductions of body weight and body weight gain were noted in treated animals. Because of the limitations of the early chronic feeding study, which is used only as supporting study, the subchronic feeding study is considered to be the most relevant study for hazard assessment. Based on the findings of this study, the suggested LOAEL of 250 ppm (15.9 mg/kg bw/day) is used for DNEL calculation, taking also into consideration the NOAEL from the chronic study of 100 ppm. 

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Dose descriptor:

LOAEL

15.9 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Additional information

Repeated dose toxicity: oral

The repeated dose toxicity of 77PD was evaluated in a subacute feeding study in Sprague-Dawley rats (Monsanto Co. 1989). Five male and five female rats per treatment group were feed with 77PD in the diet for 28 days. The animals were feed with 100, 300, 500, 1000 and 2000 ppm (males: 8, 24.4, 37.7, 73, 142.7 mg/kg/day; females: 9.3, 26.1, 43.3, 79.2, 153.8 mg/kg/day). Control animals (5 per sex and group) received standard laboratory diet. Physical observations, body weight and food consumption measurements were performed on all animals pretest and at selected intervals during the treatment period. Hematology and clinical chemistry determinations were performed on all animals at study termination. After at least four weeks of treatment, all survivors were sacrificed, selected organs were weighed and organ/body weight ratios calculated. Complete gross postmortem examinations were conducted on all animals. No histopathology was conducted.

No mortality occurred during in the study. In addition, no test substance-related clinical signs were observed during the study in any of the treated animals.

Differences from control in mean body weights were statistically significant in males of the 500 ppm and 1000 ppm treatment groups (p<0.05) and in males and females of the 2000 ppm treatment group (p<0.01). During week 1 mean food consumption values were reduced in treated males and females (males 500 ppm and higher, females 300 ppm and higher); whereas mean food consumption data during Weeks 3 and 4 were comparable to control values.

The males and females of the highest dose groups (1000 ppm and 2000 ppm) exhibited increased mean platelet counts following four weeks of treatment. The males in these groups also exhibited increased mean erythrocyte counts. These increases in mean platelet and erythrocyte counts were considered treatment-related. No treatment-related differences were noted in hemoglobin concentrations, hematocrit values and total leukocyte counts in treated animals compared to control.

Alterations were noted in several clinical chemistry parameters, which occurrence at higher dose levels only. Serum Glutamic Pyruvic Transaminase values were significant reduced in females of the 500 ppm group (p<0.05) and in males and females of the 1000 ppm and 2000 ppm groups (p<0.05 or <0.01). In addition, fasting glucose values were slightly reduced in high-dose males and inorganic phosphorus was slightly increased in males of the 1000 ppm and 2000 ppm treatment groups. In females of the highest dose group values of the alkaline phosphate, and blood urea nitrogen were increased whereas the total protein value was decreased. For the most part these changes were statistically significant.

Several organs in the treated males and females exhibited alterations in mean absolute and/or relative (to body weight) weight data; however these alterations noted were generally consistent with the reductions noted in terminal body weights. These organ weight changes were considered secondary effects and were not considered indicative of significant organ toxicity. No treatment-related gross pathology alterations were observed.

The authors suggested a NOEL for males of 100 ppm and females of 300 ppm, which based on very slight effects in body weight gain and body weight. Since the body weight effects seen in males at 300 ppm are not statistically significant and rather weak (body weight -12%, body weight gain -4.8%) a NOAEL of 300 ppm (ca. 24.4 mg/kg bw/day) is suggested.

A three-months feeding study with 77PD was conducted to assess the potential subchronic toxicity of 77PD (Monsanto Co. 1989). Sprague Dawley rats (10 per dose and sex) were administered orally, via dietary admixture, at dose levels of 100, 250 and 500 ppm for male rats (6.6, 15.9, 32.4 mg/kg bw/day) and 250, 500 and 750 ppm for female rats (18.1, 36, 54.5 mg/kg bw/day) for a period of three months. Control animals (10 per sex) received standard laboratory diet. Physical observations, ophthalmoscopic examinations, body weight and food consumption measurements were performed on all animals pre-test and at selected intervals during the treatment period. Hematology and clinical chemistry evaluations were performed on all animals at months 1.5 and three. After three months of treatment, all animals were sacrificed, selected organs were weighed and organ/body and organ/brain weight ratios calculated. Complete gross post-mortem examinations were conducted on all animals. Histopathological evaluation of selected tissues was performed for all control and high-dose animals. The lung, spleen, liver and kidney were examined microscopically for all animals in all groups.

No mortality occurred during the study. No treatment-related clinical signs were noted in any of the treated animals. There were no ophthalmoscopic findings noted following three months of treatment which were attributed to the administration of the test substance. Mean body weights were slightly reduced in males of the 250 ppm group (-5%) and significant reduced (p<0.05) in males of the 500 ppm group (-12%). The body weights of females of the 250 ppm (-11%), 500 ppm (-11%) and 750 ppm (-15%) groups were significant reduced (p<0.01) compared to control. The body weight gain was reduced in males of the 250 ppm group (-9%) and significant reduced (p<0.01) in males of the 500 ppm group (-20%). Females of the 250 ppm, 500 ppm and 750 ppm groups showed a significant reduction in body weight gain (p<0.01); -23%, -22% and -32 %, respectively. In general with the exception of week 1, the mean food consumption values of the treated males and females were comparable to control throughout the study. During week 1 the mean food consumption values of the males in the 250 ppm and 500 ppm groups and of the females in the 250 ppm, 500 ppm, and 750 ppm groups were significantly reduced compared to controls. These reduced mean food consumption values were attributed to the administration of the test substance, possibly due to poor initial palatability.

The mean hematology data of the treated males and females was unremarkable. There were no findings which were attributed to the administration of the test substance.

Several clinical chemistry parameters exhibited statistically significant differences from control which were attributed to the administration of the test substance. The alkaline phosphatase was significant elevated in males of the 500 ppm group and in females of the 750 ppm group at three months. Blood urea nitrogen values were significant elevated in females of the 750 ppm group at three months. Glutamic oxaloacetic transaminase mean serum levels were significant reduced in males of the 100 ppm, 250 ppm and 500 ppm groups at month 1.5 but not at study termination (three months). The glutamic pyruvic transaminase mean serum levels were significant reduced in females of the 750 ppm group at 1.5 months and in 500 ppm and 750 ppm females at three months. The significance of the changes noted in serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase are unclear. Other sporadic differences from control (some statistically significant) were observed in the clinical chemistry data. However, there were no treatment-related findings noted in any of the other clinical chemistry parameters.

Several organs in the treated males and females exhibited alterations in mean absolute and/or relative (to body weight or to brain weight) weight data. The mean brain to body weight ratio and the mean testes/epididymides to body weight ratio were increased in males of the 500 ppm group; whereas the mean liver weight of these males was reduced. The mean brain to body weight ratios and the mean liver to body weight ratios were increased in females of the 250 ppm, 500 ppm, and 750 ppm groups; whereas the mean kidney/brain weight ratios were slightly reduced in females of the 500 ppm and 750 ppm groups. The mean spleen to body weight ratios were slightly increased in females of the 250 ppm, 500 ppm and 750 ppm groups. The authors concluded that these alterations in absolute and relative (to body weight and brain weight) organ weight data were generally consistent with the reductions noted in terminal body weights. These organ weight changes were considered to be secondary effects and were not considered indicative of significant organ toxicity.

No treatment-related gross lesions or treatment-related histological alterations were noted in animals sacrificed at study termination. Tissues from the dietary controls were comparable histological with those from treated rats.

Based on the body weight data obtained during this study, the authors suggested a NOEL of 100 ppm for males and a LOAEL of 250 ppm for female rats.

The toxicity of 77PD was evaluated in a limited early two-year chronic feeding study (Monsanto Co. 1978). Groups of albino rats were feed (50 per dose and sex) with 0, 30, 100 or 300 ppm test substance in the diet. Body weights were recorded on the first day of the test, weekly for 13 weeks, and monthly thereafter. Food consumption was recorded at weekly intervals for 13 weeks and a monthly interval thereafter (7-day collection period each month). Routine checks for mortalities and moribund animals were conducted daily during the investigation. Clinical signs and were recorded as noted during the daily mortality checks during months 1 through 17; these observations were recorded once per month for month 18 through 22 and twice per month for months 23 and 24. Haematology, clinical chemistry and urinalyses were done on all remaining animals at study termination. In addition, blood and urine samples were collected individually from 10 rats of each sex from the control and 300 ppm group at 3, 6, 12, 18, and 24 months of testing.

Complete gross necropsies were conducted on all animals found dead, on all animals sacrificed in extremis and on all remaining animals at 24 months of testing. Microscopic examinations were conducted on some animals found dead, selected animals sacrificed in extremis, and on all surviving animals of the control and 300 ppm groups at 24 months of testing.

Survival among treated animals was similar to that among the control animals. However, an increase in mortality among control and test animal occurred 17 months of testing because of a severe respiratory infection. All animals received tetracycline hydrochloride treatment for a 2-week period (30 g/kg of diet). No clinical signs were noted. A slight reduction in body weights and body weight gains were noted for males and females treated with 300 ppm throughout the study (body weight reduction ca. 8 % -13 %, body weight gain reduced ca. 9% to16 %). Body weights of animals fed 100 ppm were statistically reduced only during the initial 7 weeks of testing; whereas in the following weeks the body weights were comparable to control. Animals of the lowest dose group (30 ppm) had body weights comparable to control during the whole study. Food consumption of animals from the 100 ppm and 300 ppm treatment groups was reduced during the first weeks of testing. The food intake of these animals was similar to the control during subsequent weeks. The food intake of low dose group animals was comparable to control.

The results of hematologic studies conducted, including total and differential leukocyte count, erythrocyte count, hemoglobin concentration, hematocrit value, mean carpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration were either similar to the controls or within range of expected values for albino rats of this age and strain in this laboratory. The results of clinical chemistry conducted were considered normal for albino rats of this age and strain in this laboratory. Examination of the urinalyses was similar between test and control animals. No treatment-related gross lesions were noted in animals sacrificed at study termination. In addition, no relevant treatment-related effects on organ weights, organ to body and organ to brain weight ratios were noted. No treatment-related alterations in histopathology were noted in animals of the highest dose group (300 ppm) at study termination. The lesions noted were those of naturally occurring diseases and were present in test and control animals with similar incidence and relative severity. In addition, microscopic evaluations of suspected neoplasms among all sacrificed and all animals that died during the study were conducted. No differences were noted between test and control rats as to the organ system involved, type or classification of neoplasms. The spectrum of neoplasms observed was comparable to the historical control data.

Based on findings from this study, a NOAEL of 100 ppm is suggested, which based on the body weight and body weight gain effects seen at 300 ppm.

Justification for classification or non-classification

No classification is required according to the classification criteria 67/548/EWG and regulation no. 1272/2008 (GHS).