Mercaptoacetic acid

Carcinogenicity

Description of key information

No carcinogenicity data is available on mercaptoacetic acid and its salts by the inhalation or oral routes. The information on the carcinogenicity potential of mercaptoacetic acid and its salts is limited to a study in mice by chronic cutaneous application of sodium mercaptoacetate.

 

The carcinogenicity of sodium mercaptoacetate was evaluated using 94 Swiss female mice (7 weeks old) from the Eppley colony. 0.02 ml of a 1.0 and 2.0 % solutions of sodium mercaptoacetate in acetone (equivalent to dose levels of 6.6 and 13.3 mg/kg bw) were applied twice per week to the shaved skin (interscapular region) of each of the 49 or 45 mice, respectively. Ninety-three mice served as negative controls. Positive control groups, 40 mice, were treated with 7,12-dimethylbenz-[a]-anthracene. None of the experimental or control mice survived beyond week 120 of treatment. Infectious diseases, such as pneumonia and hepatitis, occurred in a small number of animals, resulting in an increased number of deaths. Large numbers of neoplasms were observed in treated and negative control mice: lymphomas, pulmonary adenomas, hepatic hemangiomas, ovarian neoplasms, and dermal fibromas. Epidermal neoplasms were not observed. Differences in the incidence of neoplasms between experimental and negative control mice were not statistically significant. No significant decrease in the life span of mice in experimental groups was observed. The authors concluded that sodium mercaptoacetate was not carcinogenic (Stenback et al., 1977).

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

GLP compliance:

no

Species:

mouse

Strain:

Swiss

Sex:

female

Details on test animals or test system and environmental conditions:

-Animals:
Source: the Eppley colony
Age: 7 weeks old
Housing: 10 per cage plastic cage
Diet: Wayne diet (Allied Mills, Chicago, IL) ad libitum
Water: ad libitum

Route of administration:

dermal

Vehicle:

acetone

Details on exposure:

The chemicals were applied in a volume of 0.02 ml twice weekly to a 1-cm  diameter regularly-shaved area of intrascapular skin of the mice.

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

life-time

Frequency of treatment:

twice weekly

Remarks:

Doses / Concentrations:
1 and 2% in acetone solution
Basis:

No. of animals per sex per dose:

50 per treated group, n=100 for control group, n=40 for positive  control group

Control animals:

yes, concurrent vehicle

Details on study design:

Post-exposure period: none

Positive control:

7,12-Dimethylbenz[a]anthracene
Supplier: Aldrich Chemical Co.
Purity: no data

Observations and examinations performed and frequency:

Animals were checked weekly and all lesions and tumours were recorded.

Sacrifice and pathology:

Complete autopsy was performed on all animals and skin samples, grossly  observed tumours and lesions of lungs, kidneys and other tissues were  studies histologically. Formalin-fixed paraffin embedded specimens were  cut and stained with haematoxylin and eosin, and with other stains as  appropriate. 

Statistics:

The statistical significance of the results was evaluated using the  method of Armitage (1971).

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

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

not examined

Histopathological findings: neoplastic:

no effects observed

Details on results:

The average lifespan of the animals were not affected by the  treatment.None of the experimental or control mice survived beyond week  120 of treatment. Infectious diseases, such as pneumonia and hepatitis,  occurred in a small number of animals, resulting in an increased number  of deaths.  

The behaviour of mice in test groups was normal and there were no marked  differences between groups with respect to the body weight changes and  food intake. No local changes occurred in treated mice and no treatment related  epidermal hyperplasia, ulceration or dermatitis was observed.

No significant difference was seen in the incidence or tissue location of  neoplasms or in the numbers of mice with neoplasms, following the  application of 0.02 ml of 1% and 2% solutions of sodium thioglycolate in  acetone to the shaved backs of 49 and 45 female Swiss mice, twice weekly  for up to 120 weeks. No epidermal tumours were  reported. One each of the following tumours was found in the treated mice  but not in controls; subcutaneous haemangioma, mammary adenoma, liver  leiomyosarcoma, uterine leiomyosarcoma. Of 49 and 45 mice treated with 1  and 2% solutions respectively, 19 (39%) and 22 (49%) had tumours,  compared to 39 (42%) of 93 mice, which were apparently untreated. The  total number of tumours in each case was 22 and 24 compared to 46 in the  untreated controls.

Relevance of carcinogenic effects / potential:

In a non-standard study by dermal route, sodium thioglycolate was administered to mice as 0, 1.0 and 2.0% solutions, until all animals died. Differences in the life span and the incidence of neoplasms between experimental and negative control mice were not statistically significant.

Dose descriptor:

conc. level: 1.0 and 2.0 %

Sex:

female

Basis for effect level:

other: Differences in the life span and the incidence of neoplasms between experimental and negative control mice were not statistically significant.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Frequencies of neoplams in mice

	Conc. applied (%)	Total # of rats	# of rats with tumours (%)	Total # of tumours	Lym-phoma	Lung adenoma	Liver haeman-gioma	Ovarian	Sub-cutaneous fibroma	Others
Negative control	-	93	39 (42)	46	25	16	1	3	1	-
Sodium thioglycolate	1.0	49	19 (39)	22	14	3	1	0	1	Sc. haemangioma (1) Mammary adenoma (1)
	2.0	45	22 (49)	24	13	7	2	0	0	Liver and uterine leiomyosarcomas (1)
DMBA (+ control)	0.1	40	38 (95)	67	5	0	0	0	0	Keratoacenthomas (14) Squamuous-cell carcinomas (10)

Executive summary:

The carcinogenicity of sodium thioglycolate was evaluated using 94 Swiss female mice (7 weeks old) from the Eppley colony. 0.02 ml of a 1.0 and 2.0 % solutions of sodium thioglycolate in acetone (equivalent to dose levels of 6.6 and 13.3 mg/kg bw) were applied twice per week to the shaved skin (interscapular region) of each of the 49 or 45 mice, respectively. Ninety-three mice served as negative controls. Positive control groups, 40 mice, were treated with 7,12-dimethylbenz-[a]-anthracene. None of the experimental or control mice survived beyond week 120 of treatment. Infectious diseases, such as pneumonia and hepatitis, occurred in a small number of animals, resulting in an increased number of deaths. Large numbers of neoplasms were observed in treated and negative control mice: lymphomas, pulmonary adenomas, hepatic hemangiomas, ovarian neoplasms, and dermal fibromas. Epidermal neoplasms were not observed. Differences in the incidence of neoplasms between experimental and negative control mice were not statistically significant. No significant decrease in the life span of mice in experimental groups was observed. Sodium thioglycolate was not carcinogenic under this experimental condition..

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Justification for classification or non-classification

According to REGULATION (EC) No 1272/2008 of 16 December 2008 and the available carcinogenicity data, no classification is warranted for mercaptoacetic acid.