Chloroform

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

Principles of method if other than guideline:

The original study is available in Japanese only. The following evaluation is based on an English translation (Harlan Japan) of the report. The study was carried out according to the skin sensitisation test method applying the local lymph node assay, method B.42, suggested by the European Commission with acceptable restrictions.

GLP compliance:

no

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

20 female mice of CBA/J strain (CBA/JNCrj, SPF) at 9 weeks of age; temperature between 21 and 25 °C, humidity between 40 and 75 %, air exchange rate approximately 15 times/hour, 12 hr light/12 hr darkness

Vehicle:

acetone/olive oil (4:1 v/v)

Concentration:

10%

No. of animals per dose:

5 animals

Details on study design:

4 groups: 1. 25 µL/ear chloroform; 2. 25 µL/ear acetone:olive oil (4:1); 3. 25 µL/ear 10% hexyl cinnamic aldehyde in chloroform; 4. 25 µL/ear; 10% hexyl cinnamic aldehyde in acetone:olive oil (4:1).
Application of test solutions to both auricles of the mice for three consecutive days. 3 days later, 3H-methyl thymidine (Amersham Pharmacia Biotech, Inc.) was administered intravenously (250 uL, 2.96 MBq/mL). Five hours later, animals were euthanised. The auricular lymph nodes were removed, in order to compare reactions to HCA with chloroform as vehicle and with acetone:olive oil as vehicle. Cells were isolated from the lymph nodes, cell suspensions prepared and radioactivity was measured with a beta scintillation counter.

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

Mean and standard deviation of the data were calculated and the groups were compared using student's t-test

Positive control results:

The positive control substance hexyl cinnamic aldehyde was characterised to be sensitising in the local lymph node assay.

Key result

Parameter:

SI

Remarks:

Chloroform (10%)

Value:

2.48

Test group / Remarks:

chloroform in acetone:oilve oil (4:1) at 10%

Key result

Parameter:

SI

Remarks:

Cinnamic aldehyde (positive control)

Value:

3.49

Test group / Remarks:

cinnamic aldehyde in acetone:olive oil (4:1)

Key result

Parameter:

SI

Remarks:

negative control

Value:

1

Test group / Remarks:

negative control

In the local lymph node assay, chloroform tended to be higher abundant in the lymph nodes than the acetone/olive oil in the solvent control. The lympho-proliferative activity is used as an index of sensitisation in the LLNA, but since primary irritation also activates lymph cell proliferation through inflammatory cytokine effects, the reactions are said to be difficult to differentiate. Since Montelius et al. (1994) showed activation due to primary irritation in LLNA using methanol/chloroform as the vehicle, it is very likely that the reactions to chloroform seen in the Japanese LLNA study were due to primary irritation rather than sensitisation.

Interpretation of results:

not sensitising

Conclusions:

In contrast to the positive control substance hexyl cinnamic aldehyde, chloroform was characterised to be not sensitising in the local lymph node assay.

Executive summary:

The skin sensitisation potential of chloroform was tested in a local lymph node assay with 20 female CBA/J mice according the test method B.42 suggested by the European Commission. Stimulation index determined for chloroform used in the vehicle acetone:olive oil (4:1) at a concentration of 10 % was 2.48, which was below the threshold of 3 indicating sensitising properties. In contrast, the positive control substance hexyl cinnamic aldehyde used in the vehicle acetone:olive oil (4:1) at a concentration of 10 % had a stimulation index of 3.49 and thus was identified as a skin sensitiser.

In the local lymph node assay the lymphoproliferative activity is used as an index of sensitisation, but since primary irritation also activates lymph cell proliferation through inflammatory cytokine effects, the reactions are said to be difficult to differentiate. Since Montelius et al. (1994) showed activation due to primary irritation in LLNA using methanol/chloroform as the vehicle, it is very likely that the reactions to chloroform seen in the Japanese LLNA study were due to primary irritation rather than sensitisation. In conclusion, chloroform should be considered as not sensitising to the skin.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

In the local lymph node assay (Matsuoka et al., 2002) the lymphoproliferative activity is used as an index of sensitisation, but since primary irritation also activates lymph cell proliferation through inflammatory cytokine effects, the reactions are said to be difficult to differentiate. Since Montelius et al. (1994) showed activation due to primary irritation in LLNA using methanol/chloroform as the vehicle, it is very likely that the reactions to chloroform seen in the Japanese LLNA study were due to primary irritation rather than sensitisation; CFM was not sensitizing in he LLNA using female CBA/J mice.

Another skin sensitisation test was carried out with female guinea pigs of the Std:Hartley strain (Matsuoka et al. 2002). Guinea pigs were used in the maximisation test. A strong irritation reaction was observed in all animals used in the maximisation test, which was comparable in test and control animals. From this it was concluded that chloroform was not sensitising to the skin of guinea pigs.

In conclusion, chloroform should be considered as not sensitising to the skin.

Respiratory sensitisation

Endpoint conclusion

Additional information:

No signs of respiratory sensitisation have been reported.

Justification for classification or non-classification

Based on the available data in can be concluded that chloroform is not sensitising to the skin. Therefore, chloroform does not need to be classified as a skin sensitiser according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.