Clorofene

Carcinogenicity

Description of key information

Combined 2 year chronic toxicity and carcinogenicity study, oral, rat:

carcinogenicity females: NOAEL = 60 mg/kg bw/day (equivocal evidence; based on the occurrence of a rare carcinogenic tumour of the renal transitional epithelium in one female from the mid dose group and one female from the highest dose; historical control data from the US NTP database showed that there were 0 incidences of this tumour out of 1068 controls)

carcinogenicity males: NOAEL >= 120 mg/kg bw/day (no evidence of carcinogenicity)

Combined 2 year chronic toxicity and carcinogenicity study, oral, mouse:

carcinogenicity females: NOAEL >= 480 mg/kg bw/day (no evidence of carcinogenicity)

carcinogenicity males: NOAEL = 120 mg/kg bw/day (some evidence of carcinogenicity at the highest dose level, based on increased incidence of renal tubule adenoma and combined renal tubule adenoma/carcinoma)

1 year initiation/promotion study, dermal, mouse:

weak promotion potential in males and females

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

120 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

The available information comprises an adequate and reliable study (Klimisch score 1), and is thus sufficient to fulfil the standard information requirements set out in Annex X, 8.5, of Regulation (EC) No 1907/2006.

System:

urinary

Organ:

kidney

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Quality of whole database:

The available information comprises an adequate and reliable study (Klimisch score 1), and is thus sufficient to fulfil the standard information requirements set out in Annex X, 8.5, of Regulation (EC) No 1907/2006.

Justification for classification or non-classification

The available data on carcinogenicity meet the criteria for classification according to Regulation (EC) 1272/2008. The test substance is classified as Carcinogenic Category 2, H351: Suspected of causing cancer.

In fact, the evaluation of the available and reliable study data, lead to the conclusion, that a carcinogenic potential cannot be properly excluded with respect to Chlorophene. Moreover, these data were also reviewed and evaluated by the ECHA Committee for Risk Assessment (RAC) and consequently, a RAC Opinion for harmonised EU classification and labelling of Chlorophene was adopted in 2015 ( RAC CLH-O-0000001412-86-58/F, 12 March 2015). As a result, and referring to the Adaptation to Technical Progress (ATP) to CLP Regulation, Chlorophene was inserted in ATP10 with following classification and labelling for carcinogenicity: Carc. 2, H351.

Additional information

Reliable carcinogenicity studies in rodents are available for the test substance.

Oral:

-2 year chronic oral toxicity and carcinogenicity study in the rat

The carcinogenicity of the test substance was assessed in a 2 year chronic oral toxicity study combined with carcinogenicity study in F344/N rats (National Toxicology Program, Report No. 424, 1994). Groups of 80male and 80 female rats were administered the test substance in corn oil by gavage at doses of 0, 30, 60 or 120 mg/kg bw/day (males) or 0, 60, 120 or 240 mg/kg bw/day (females) 5 days a week. 10 rats per sex and dose group were sacrificed after 13 weeks for interim evaluation. 10 rats per sex and dose group were sacrificed after 65 weeks for interim clinical pathology and histopathological examinations. All remaining animals were sacrificed after 104 weeks. The duration of the final undosed interval was 10-12 days for the 104 week scheduled termination. Animals were observed twice daily and clinical findings were recorded weekly. Body weights were determined at study initiation, weekly for the first 13 weeks, and monthly thereafter. Food consumption was measured monthly. Blood and urine samples were collected from all animals designated to the 13 and 65 week interim sacrifice at respective study termination for haematological and clinical chemistry examinations as well as urinalysis. At interim sacrifices organ weights of brain, heart, kidneys, liver, lung, right testis and thymus were determined. Gross pathological examinations were performed on all animals. Histopathological examinations were performed on all tissues with grossly visible lesions and on all animals killed moribund. At the 13 and 65 week interim sacrifices a complete histopathology was performed on all rats of the control and high dose group. At study termination a complete histopathology was performed on all rats. Survival of dosed male and female rats was similar to that of the controls. Mean body weights of dosed rats were generally similar to those of the controls. No chemical-related clinical findings were observed except yellow staining of the urogenital area hair coat in dosed female rats which was considered to be treatment-related (0 mg/kg bw/day: 9/80 females; 60 mg/kg bw/day: 66/80 females; 120 mg/kg bw/day: 69/80 females; 240 mg/kg bw/day: 77/80 females). Kidney weights were increased in a time- and dose-dependent manner with males as the most sensitive sex. At the 3-month interim evaluation, absolute and relative kidney weights were significantly increased in males receiving 120 mg/kg bw/day and females receiving 240 mg/kg bw/day. Microscopic lesion related to compound administration at the 13-weeks evaluation was nephropathy in female rats, for which the incidence and severity increased with dose. At the 65-week interim evaluation, absolute kidney weights were greater in all dosed male groups and absolute and relative kidney weights were significantly greater in mid- and high-dose females compared to the controls.Nephropathy was present in essentially all rats after 15 months of chemical administration; however, nephropathy increased in severity with dose and was more severe in male than in female rats. At study termination, relative kidney weights were increased in all dosed males and in females of the mid- and high dose groups. Severe, time- and dose-related nephropathy was observed in male and female rats, occurring as early as 13 weeks after the beginning of chemical administration (females). The nephropathy was characterized by tubule dilatation, flattening of the tubule epithelium, and the presence of regenerative tubules surrounded by a thickened basement membrane. With increased severity, the prominent dilated tubules contained hyaline casts and cellular debris. More advanced lesions were characterized by additional alterations of interstitial fibrosis, multiple interstitial foci of mononuclear cells, foci of mineralization, and degenerative changes with sclerosis of glomeruli. The dose-related increase in severity was particularly striking in high-dose female rats because of the usual minimal severity of spontaneous nephropathy in control female rats. The severity of the nephropathy was significantly increased in a time- and dose-dependent manner both in males and females, with males being the most sensitive sex. In male rats dosed for as long as 2 years, secondary hyperparathyroidism developed, with parathyroid gland hyperplasia, mineralization of the kidney and glandular stomach, and fibrous osteodystrophy occurring in the high-dose group. The kidney was the only organ in which chemical- related increased incidences of neoplasms may have occurred. One renal tubule adenoma occurred in a control male rat, one renal tubule adenoma and one transitional cell carcinoma occurred in high-dose female rats, and one transitional cell carcinoma occurred in a mid-dose female. One renal tubule carcinoma was observed in a high-dose male rat. Thus, under the conditions of this 2-year gavage study, there was no evidence of carcinogenic activity of the test substance in male F344/N rats receiving 30, 60, or 120 mg/kg bw/day. There was equivocal evidence of carcinogenic activity of the test substance in female F344/N rats based on the occurrence of two rare renal transitional cell carcinomas.

 

-2 year chronic oral toxicity and carcinogenicity study in the mouse

The carcinogenicity of the test substance was assessed in a 2 year chronic oral toxicity study combined with carcinogenicity study in B6C3F₁mice (National Toxicology Program, Report No. 424, 1994). Groups of 70male and 70 female mice were administered the test substance in corn oil by gavage at doses of 0, 120, 240 or 480 mg/kg bw/day 5 days a week. 10 mice per sex and dose group were sacrificed after 13 weeks for interim evaluation. Further 10 mice per sex and dose group were sacrificed after 65 weeks. All remaining animals were sacrificed after 104 weeks. Animals were observed twice daily and clinical findings were recorded weekly. Body weights were determined at study initiation, weekly for the first 13 weeks, and monthly thereafter. Food consumption was recorded weekly. At interim sacrifices organ weights of brain, heart, kidneys, liver, lung, right testis and thymus were determined. Gross pathological examinations were performed on all animals. Histopathological examinations were performed on all tissues with grossly visible lesions and on all animals killed moribund. At the 13 and 65 week interim sacrifices a complete histopathology was performed on all rats of the control and high dose group. At study termination a complete histopathology was performed on all rats. Survival of dosed male and female rats was decreased compared to that of the controls. The probability of survival for dosed males ranged from 64 – 81% (control 90%). The probability of survival for females of the highest dose group was significantly lower (51%) compared to that of the controls (74%). Renal disease was considered a significant factor in the decreased survival of male and female mice. Mean final body weights were statistically significantly lower in males at all dose groups and females of the mid and high dose compared to control animals. Decreased body weights (by 10%) were apparent from weeks 28, 68 and 84 for males dosed at 120, 240 and 480 mg/kg bw/day, respectively. In females dosed at 240 and 480 mg/kg bw/day a 10% lower mean body weight compared to controls occurred from weeks 93 and 26, respectively. Treatment-related clinical signs included emaciation, abnormal posture, rough hair coat and hypoactivity. No effect on food consumption was observed. At the 13-week interim evaluation, nephropathy was observed in treated animals of both sexes with dose-related incidence and severity (more severe in males; severity grades based on the extent oif parenchymal involvement). Kidney weights of high dose males were significantly decreased. Microscopic lesions were confined to the kidney and included multiple foci of dilated tubules with a flattened epithelium, a few tubules with hyaline casts, regenerated tubules with basophilic epithelium, a few necrotic tubules with neutrophils and debris in the lumen and foci of mononuclear cells in the renal cortical interstitium. Additionally, significantly increased absolute and relative liver weights were observed in high dose males and females after 13 weeks of treatment. At the 65-week interim evaluation, spontaneous nephropathy in control males increased and, thus, incidences in dosed males was similar to controls. The incidence of nephropathy in dosed females increased. However, a dose-related increase in severity occurred in both, dosed males and females. Absolute and relative kidney weights of treated males as well as absolute kidney weights of treated females were statistically significantly decreased compared to corresponding control animals. With regard to macroscopic lesions affected kidneys, particularly in males, were pale, tan and/or granular. Correspondingly, histopathology revealed multifocal dilatation of renal tubules with flattening of the tubule epithelium, luminal hyaline casts and cellular debris, thickened tubule basement membranes, tubule cell necrosis, regeneration of tubule cells and infiltrates of mononuclear cells in the renal cortical interstitium. Absolute and relative liver weights were significantly increased in high dose females after 65 weeks of treatment. At the end of the 2 year study, proliferative lesions were observed in the kidneys of treated males (renal tubule hyperplasia in mid and high dose males, renal tubule adenoma and carcinoma). In the standard evaluation, the combined incidence of renal tubule adenoma and carcinoma was increased in 240 mg/kg bw/day male mice. Six renal tubule adenomas and three renal tubule carcinomas occurred in dosed male mice. No renal neoplasms occurred in female mice. Due to the marginal increase in renal neoplasia, and the small size of renal neoplasms, an extended evaluation of the kidney was conducted. No significant alteration in the neoplasm incidences were observed in female mice. However, a dose-related increased trend of renal tubule adenoma was observed in male mice. Combination of the extended evaluation with the original evaluation resulted in an increased incidence of renal tubule adenomas in the 480 mg/kg bw/day males and an increased incidence of renal tubule adenomas or carcinomas in both the 240 and 480 mg/kg bw/day males. Additionally, a dose-related increased incidence in hyperplasia of the forestomach was observed in female mice probably related to an irritant effect of the test substance. Incidence was also increased in treated males but without dose relation. Treatment-related lesion occurring in males and females was focal mucosal ulceration of the forestomach. This effect might also be attributed to the irritant properties of the test substance or might occur secondary to nephropathy. Further findings (mineralization of the glandular mucosa with focal gastric and duodenal ulcers (all dosed groups of males and females), myocardial degeneration (mid- and high-dose males) and focal coagulative necrosis of the liver (high-dose females)) were considered to be secondary to the combined disturbances of nephropathy and an associated secondary hyperparathyroidism. Thus, under the conditions of this 2-year gavage study, there was some evidence of carcinogenic activity of the test substance in male B6C3F₁mice based on increased incidences of renal tubule adenoma and renal tubule adenoma or carcinoma (combined). There was no evidence of carcinogenic activity of the test substance in female B6C3F₁mice receiving 120, 240, or 480 mg/kg bw/day.

 

Dermal:

- 1 year dermal initiation/promotion study in the mouse

The carcinogenicity of the test substance was assessed in a 1 year initiation/promotion study in Swiss (CD-1®) mice (National Toxicology Program, Report No. 444, 1995). Groups of 50male and 50 female mice were topically exposed to the test substance to study the potential of the test substance to act as an initiator or promoter during carcinogenesis as well as to act as a complete carcinogen. The potential of the test substance as an initiator was evaluated by applying a single dose (100 µL) of the test substance formulated in acetone at a concentration of 10 mg/mL to the backs of the mice during week 1. 12-0-tetradecanoylphorbol-13-acetat (TPA) was used as a promoter which was applied three times per week for the first 6 months and once weekly for the second 6 months of the study (5 µg TPA in 100 µL acetone per application). The potential of the test substance as a promoter was also evaluated. For this purpose, 7,12-dimethylbenz(a)anthracene (DMBA) was used as initiator and applied at a single dose during week 1 (50 µL DMBA in 100 µL acetone). The test substance formulated in acetone was administered three times weekly for up to 51 weeks (0.1, 1 or 3 mg test substance in acetone; 100 µL per application). Additionally, the potential of the test substance to act as complete carcinogen was assessed by administration of a single initiating dose of the test substance (10 mg in 100 µL acetone) and subsequent promoting applications of 0.1, 1 or 3 mg of the test substance (100 µL per application) three times weekly up to study termination. Comparative control groups were used during the study (initiator/promoter; vehicle control: acetone/acetone; reference promoter control: TPA/TPA; reference initiator control: DMBA/acetone; reference initiator/promoter control: DMBA/TPA; reference complete carcinogen control: acetone/DMBA). Animals were observed twice daily and clinical findings were recorded weekly. To follow the appearance and progression of any tumor development the skin was observed for clinical signs once weekly. Body weights were determined weekly for the first 3 months and monthly thereafter. Gross pathological examinations were performed on all animals and the kidneys, liver and thymus were weighed. Histopathological examinations were performed on skin (up to five tumors), nose, liver, kidney, thymus and on all tissues with grossly visible lesions.

With regard to the assessment of the test substance as an initiator survival rates of both sexes initiated with the test substance and promoted with TPA were lower compared to vehicle and promoter controls but greater compared initiator/promoter control. No effects on body weights were observed in males and females compared to initiator/promoter and promoter control groups as well in females compared to vehicle controls. Mean final body weight of test substance/TPA treated males was 95% of the vehicle control. Reversible signs of skin irritation were observed due to TPA administration from day 11. Papillomas were observed in 12/50 male mice administered test substance/TPA after 22 weeks and in 7/50 females after 12 weeks. However, the incidences of papillomas in mice treated with test substance/TPA were lower compared to promoter control animals (16/50 males and 16/50 females). Additionally, incidences were much lower compared to initiator/promoter control (40/50 males and 48/50 females). Thus, it is considered that the test substance does not have an initiating potential.

With regard to the assessment of the test substance as a promoter no effects on survival rates were observed compared to the initiator and initiator/promoter control group. Additionally, no effects on body weights were noted. Few skin lesions wererecorded in animals promoted with 0.1 or 1 mg test substance. Irritation incidence in animals promotes with 3 mg test substance were comparable to the corresponding initiator/promoter control group but much higher compared to initiator control animals. A dose-related increasedincidence of papillomas was observed in males following initiation with DMBA and promotion with the test substance (0 mg: 8/50; 0.1 mg: 3/50; 1.0 mg: 5/50 and 3.0 mg: 14/50) as well as in females treated accordingly (0 mg: 2/50; 0.1 mg: 6/50; 1.0 mg: 6/50 and 3.0 mg: 18/50). The incidence of papillomas in females at the highest dose group was statistically significantly increased compared to initiator control females but only marginally increased in males. Although the time to appearance of the first papilloma was shorter in animals initiated with DMBA and promoted with 3.0 mg test substance the time it took for half of the number of responding animals to develop papillomas was similar between these groups. Since topical exposure to the test substance alone did not result in altered papilloma incidences and incidences at the highest promoted dose group were increased compared to the initiator control, the test substance was considered to have a promotion potential. However, the promotion potential was judged to be weak since incidences of papillomas in animals initiated with DMBA and promoted with 3.0 mg test substance (14/50 males and 18/50 females) were much lower compared to the respective initiator/promoter control animals (40/50 males and 48/50 females).

With regard to the assessment of the test substance as a complete carcinogen survival rates of both sexes initiated and promoted with 3.0 mg test substance were significantly lower compared to vehicle controls but significantly greater compared to complete carcinogen control. Final mean body weights were decreased compared to vehicle control females while no effect on body weights of males was observed. Incidences in skin lesions (scales and/or crusts and irritation) were generally greater in animals initiated with 10 mg and promoted with 3.0 mg test substance compared to animals promoted with 0.1 or 1.0 mg test substance. However, incidences were comparable to the complete carcinogen control animals. The test substance showed no activity as complete carcinogen. During the course of the study 1/50 low dose male developed a papilloma after 11 weeks of application and 3/50 low dose females developed papillomas after 22 weeks. In 1/50 female receiving the highest dose of the test substance two papillomas were observed after 10 weeks. No mice administered the test substance as initiator and promoter had papillomas at the end of the study and no malignant cutaneous epithelial tumors were observed at the application sites. Thus, the test substance is not considered to be a complete carcinogen.

There were no chemical-related increased incidences of tumors or nonneoplastic lesions in the kidney, liver, nose, or thymus of mice when the test substance was applied as an initiator, a promoter or a complete carcinogen.

Thus, under the conditions of this 1 year mouse skin initiation/promotion study, the test substance was shown to be a weak skin tumor promoter relative to strong promoters such as TPA. The test substance had no activity as an initiator or a complete carcinogen.