GE.15-

Committee of Experts on the Transport of Dangerous Goods

and on the Globally Harmonized System of Classification

and Labelling of Chemicals

Sub-Committee of Experts on the Transport 

of Dangerous Goods 

Sub-Committee of Experts on the Globally Harmonized 

System of Classification and Labelling of Chemicals 

Forty-seventh session Twenty-ninth session

Geneva, 22 - 26 June 2015

Item 10 (e) of the provisional agenda

Issues relating to the Globally Harmonized System 

of Classification and Labelling of Chemicals: 

Corrosivity criteria

Geneva, 29 June – 1 July 2015

Item 2 (c) of the provisional agenda

Classification criteria and related hazard communication: 

Corrosivity criteria

Proposal for revision of Chapter 2.8 of the Model Regulations

and follow-up questions

Transmitted by the expert from Canada1

Purpose

1. Following up on the discussions of the forty-sixth session of the Sub-Committee of 

Experts on the Transport of Dangerous Goods, to propose changes to Chapter 2.8 of the 

United Nations Model Regulations to the Sub-Committee of Experts on the Transport of 

Dangerous Goods (TDG Sub-Committee).

2. To refer, for clarification and further investigation, questions relating to the Globally 

Harmonised System (GHS) approaches to classification of corrosives to the Sub-Committee 

of Experts on the Globally Harmonised System (GHS Sub-Committee).

Introduction

3. Reference is made to documents:

1

In accordance with the programme of work of the Sub-Committee for 2015–2016 approved by the 

Committee at its seventh session (see ST/SG/AC.10/C.3/92, paragraph 95 and ST/SG/AC.10/42, para. 

15).

United Nations ST/SG/AC.10/C.3/2015/21−ST/SG/AC.10/C.4/2015/2

Secretariat Distr.: General

08 April 2015

English

Original: English and French
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

2

(a) ST/SG/AC.10/C.3/2014/69–ST/SG/AC.10/C.4/2014/12;

(b) ST/SG/AC.10/C.3/2014/99–ST/SG/AC.10/C.4/2014/18; 

(c) ST/SG/AC.10/C.3/2014/104;

(d) Informal document INF.15 (TDG, 46th session) – INF.7 (GHS, 28th session);

(e) Informal document INF.35 (TDG, 46th session) – INF.20 (GHS, 28th

session);

(f) Informal document INF.46 (TDG, 46th session) – INF.21 (GHS, 28th

session);

(g) Informal document INF.60 (TDG, 46th session) – INF.24 (GHS, 28th

session);

(h) Informal document INF.61 (TDG, 46th session) – INF.25 (GHS, 28th

session);

(i) Informal document INF.71 (TDG, 46th session) – INF.29 (GHS, 28th

session);

4. The efforts of the joint TDG-GHS Working Group on corrosivity criteria have led to 

several proposals for revisions to Chapter 2.8 of the Model Regulations. Significant 

support, in principle, exists within both the TDG and GHS Sub-Committees to revise the 

existing Chapter 2.8 and to advance new principles for addressing the transport of Class 8 –

Corrosive substances.

5. This proposal builds on the work of the referenced proposals above and the 

discussions that took place at the forty-sixth session of the TDG Sub-Committee. It focuses 

on the classification and packing group assignment of corrosive materials for transport, and 

presents proposed text in keeping with the generally established structure and regulatory 

format of chapters found in the Model Regulations. 

6. This proposal also removes references to some additional methods (such as the 

additivity method), as an interim measure, until the issues outlined in 

ST/SG/AC.10/C.3/2014/99 – ST/SG/AC.10/C.4/2014/18, informal document INF.46 (TDG 

46th session) – INF.21 (GHS 28th session), and raised at the forty-sixth session can be 

discussed and resolved.

7. This proposal requests clarification from the GHS Sub-Committee to address the 

significant concerns with some additional methods identified for corrosives classification 

and proposed previously in the proposals, including ST/SG/AC.10/C.3/2014/69 –

ST/SG/AC.10/C.4/2014/12, of the forty-sixth session of the TDG Sub-Committee.

Discussion and questions for the GHS Sub-Committee

Structure of the proposed text

8. In line with the comments raised previously in informal document INF.46 (TDG 46th

session) – INF.21 (GHS 28th session), this proposal proposes adapted text that is aligned 

with the generally accepted format and presented as regulatory text; key definitions are 

presented first followed by the criteria for packing group assignment.

9. Paragraph 5 of informal document INF.71 (TDG 46th session) – INF.29 (GHS 28th

session) identifies that the use of the GHS text is “included with the aim of optimal global 

harmonization of criteria now and in the future. Despite the non-legislative style of the 

GHS text, several examples of successful implementation in jurisdictions exist.” 
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

3

10. While the expert from Canada recognises the intent, the “Guiding Principles for the 

Development of the UN Model Regulations”

2

state that the one of the purposes of presenting 

the Recommendations on the Transport of Dangerous Goods in the form of a model 

regulation is “To ‘recommend’ the Recommendations on the Transport of Dangerous 

Goods to modal organizations, regional bodies and national governments (in particular 

those governments considering the development of national regulations affecting the 

transport of dangerous goods) in a form [original emphasis] that can be adopted with little 

or no modification directly into modal, regional or national regulations.” 

11. It is with this understanding that the emphasis on developing regulatory text remains 

the primary purpose of this proposal and of work towards incorporating further criteria for 

the classification of corrosives in the Model Regulations. While principles and guidance are 

useful in discussing concerns relating to regulatory provisions, they do not readily form text 

that can be incorporated into regulation and that can be readily enforced.

Introduction of sub-classifications

12. The introduction of sub-categories (8A, 8B, 8C) in ST/SG/AC.10/C.3/2014/69 –

ST/SG/AC.10/C.4/2014/12, adapted from the GHS, is a concept from the GHS that is 

foreign to the Model Regulations. The introduction and use of this classification system in 

the Model Regulations would create a lot of confusion amongst transport stakeholders and 

introduce new concepts that have not been carried over from the GHS in other sections of 

the Model Regulations.

13. Informal document INF.46 (TDG 46

th session) – INF.21 (GHS 28th session) 

originally proposed text under 2.8.3.3.1 that would allow packing group assignment for 

substances that have been classified in one of the GHS sub-categories 1A, 1B, or 1C for 

skin corrosion. This element has been removed from the current proposal – several 

questions remain regarding uncertainties with the GHS classification of a Class 8 without 

sub-classification.

Generic concentration limits

14. Tables 2.8.3 and 2.8.4 of the proposed text in ST/SG/AC.10/C.3/2014/69–

ST/SG/AC.10/C.4/2014/12 and informal document INF.71 TDG (46th session) – INF.29 

(GHS 28th session) attempt to assign (generic) concentration limits for determining packing 

group of mixtures in Class 8A and Class 8 without sub-classification respectively. 

Concentration alone is not an appropriate selection criterion for assigning packing group. 

Concentration is linked to pH for Brønsted-Lowry acids/bases and it can be a useful 

parameter to infer the corrosivity of a strong Brønsted-Lowry acid/base. Weaker

Brønsted-Lowry acid/bases are governed by their dissociation into a liquid and this 

dissociation will vary with each weaker acid/base – generic concentration limits for 

determining corrosivity become very problematic due to the huge variation in dissociation 

possible for weaker acids/bases. A concentration threshold is also problematic when 

considering corrosivity of Lewis acids/bases (an alternative acid/base definition). 

15. Given the huge variation in the types of potentially corrosive acids/bases and other 

substances that exist, determining generic concentration limits for corrosive substances 

becomes problematic and risks under or over-classifying many types of corrosives that may 

be transported. It also does not take into account the effect of the corrosive substance’s

solvent and additives in solution, which may amplify or mitigate corrosivity – a generic 

2

http://www.unece.org/fileadmin/DAM/trans/danger/publi/unrec/

GuidingPrinciples/Guiding_Principles_Rev18.pdf
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

4

concentration threshold may properly classify a specific corrosive substance in one solvent 

but not in another. For example, the presence of surfactants in solutions of certain 

household cleaning products has been found to affect the corrosivity of these products; 

when surfactants are contained in a product, some otherwise corrosive products no longer 

meet the corrosive criteria and would then be classified as irritants,

3

the opposite may also 

be true.

16. This paper poses the following questions to the GHS Sub-Committee, to aid in 

developing revised text regarding concentration limits:

(a) How does the GHS schema account for the wide range of dissociation 

potential for weak acids/bases when determining generic concentration limits?

(b) How does the GHS account for potentially synergistic effects between the 

corrosive substance and its solvent which may vary considerably based on the 

chosen solvent?

Acid/Alkaline reserve

17. The consideration of acid/alkaline reserve is raised in the proposed text of most 

previous submissions. Canada supports the consideration of acid/alkaline reserve but would 

raise several issues with the text originally proposed in ST/SG/AC.10/C.3/2014/69 –

ST/SG/AC.10/C.4/2014/12 and the references to published papers such as Young et al. 

(1988):

4

(a) While the references mentioned in the GHS5present peer-reviewed 

approaches to quantifying acid/alkaline reserve, they are not standardised 

approaches consistent with other standards referenced in the Model Regulations for 

use in classification. The lack of a standardised approach for determining 

acid/alkaline reserve presents a significant challenge in ensuring consistent, 

reproducible, and reliable results for classification of corrosive substances, and in 

the verification for enforcement of classification from a member state perspective. 

Significant variation in acid/alkaline reserve data was witnessed in Craan et al. 

(1997) between industry data and the experimental test data obtained by Health 

Canada as part of the study.6 While this may be a result of issues in the quality of 

data taken from Safety Data Sheets, the lack of a formal standard for determination 

of acid/alkali raises issues of reproducibility and consistency of data.

3 Craan A. J., Sanfaçon G., Walker R. H. (1997): The use of pH and acid/alkaline reserve for the 

classification and labelling of household cleaning products: data from a poison control center. 

International Journal for Consumer Safety Vol. 4, Iss. 4, 191-213.

4 Acid/Alkaline reserve may be determined e.g. by the methodology detailed in Young J.R., How M.J., 

Walker A.P., Worth W.M.H. (1988): Classification as corrosive or irritant to skin of preparations 

containing acidic or alkaline substances, without testing on animals. Toxicology in Vitro 2, 19-26 and 

Young J.R., How M.J. (1994): Product classification as corrosive or irritant by measuring pH and 

acid / alkali reserve. In Alternative Methods in Toxicology vol. 10 - In Vitro Skin Toxicology: 

Irritation, Phototoxicity, Sensitization, eds. A.Rougier, A.M. Goldberg and H.I.Maibach, Mary Ann 

Liebert, Inc. 23-27.

5

Ibid.

6

Ibid.
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

5

(b) More recent work on acid/alkaline reserve has built on the works referenced 

in the GHS. For example, the Craan et al. (1997)7paper has built on and furthered 

the body of work on acid/alkaline reserve. Of note, Craan et al. (1997) proposes an 

alternative definition for corrosives incorporating pH and acid/alkaline reserve based 

on thresholds and varying the acid/alkaline reserve ranges based on whether the 

substance is a solid or liquid. As well, it makes note of the impact additives (e.g., 

surfactants) can have in altering the validity of these ranges and revealed an 

asymmetric distribution along the pH axis of six classes of consumer products, 

which deviates from the proposal presented in Young et al. (1988).

8

18. Consideration of acid/alkaline reserve is maintained in the proposal below 2.8.3.1.2 

but stated as optional text. The GHS references concerning acid/alkaline reserve could be 

updated to reflect recent work in this area. They may also need to be revised, and the 

considerations around non-standardised approaches and variability in acid/alkaline reserve 

between data sets would need to be addressed before the consideration of acid/alkaline 

reserve could reasonably be incorporated into the Model Regulations – failure to do so may 

create inconsistent approaches, enforcement issues, and inconsistent classification for some 

products.

19. This paper poses the following questions to the GHS Sub-Committee to aid in 

developing revised text that would address issues relating to acid/alkaline reserve:

(a) Has the GHS Sub-Committee of Experts undertaken a review of the new 

literature on acid/alkaline reserve since its original incorporation in the GHS? Would 

the GHS Sub-Committee consider such a review with the intention of updating the 

current knowledge on acid/alkaline reserve?

(b) Would the GHS Sub-Committee consider the development or adoption of a 

standardised test method(s) for the determination of acid/alkaline reserve (e.g., 

similar to ASTM D1121-11)?9

(c) What methods exist in the GHS to account for the effects/synergies of 

additives that may impact on the validity of pH ranges and contributions of 

acid/alkaline reserve? Is the GHS Sub-Committee aware of ways in which these 

issues could be addressed and that could be incorporated into the GHS?

Additivity and dilution

20. The additivity approach presented in 2.8.2.3.3.2 of ST/SG/AC.10/C.3/2014/69 –

ST/SG/AC.10/C.4/2014/12 does not account for potential synergistic effects between 

corrosive substances in a mixture. The additivity approach presented in the GHS assumes a 

simple additive relationship between components, which may not be the case; mixtures of 

components may result in a corrosivity that is greater than or less than the sum of the 

individual components. Additional investigation of these interactions needs to be conducted 

7 Craan A. J., Sanfaçon G., Walker R. H. (1997): The use of pH and acid/alkaline reserve for the 

classification and labelling of household cleaning products: data from a poison control center. 

International Journal for Consumer Safety Vol. 4, Iss. 4, 191-213.

8 Acid/Alkaline reserve may be determined e.g. by the methodology detailed in Young J.R., How M.J., 

Walker A.P., Worth W.M.H. (1988): Classification as corrosive or irritant to skin of preparations 

containing acidic or alkaline substances, without testing on animals.

9 ASTM D1121-11, Standard Test Method for Reserve Alkalinity of Engine Coolants and Antirusts, 

ASTM International, West Conshohocken, PA, 2011, www.astm.org.
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

6

and quantification of interactions needs to be developed (along with guidance on impacting 

factors) before this approach could successfully be brought into a regulatory context.

21. The dilution approach presented in 2.8.2.3.2.2 of ST/SG/AC.10/C.3/2014/69–

ST/SG/AC.10/C.4/2014/12 states that a corrosive substance diluted with another corrosive 

substance that has an equivalent or lower corrosivity classification would be classified as 

equivalent to the original corrosive substance; this does not take into account the potential 

additivity impacts as discussed in paragraph 20. The proposed text in the annex revises the 

text originally submitted in ST/SG/AC.10/C.3/2014/69–ST/SG/AC.10/C.4/2014/12 to 

specify dilution as the process of diluting a corrosive with a non-corrosive, and would need 

to account for the impact of additives in the diluent as discussed in paragraph 15. Dilution 

with another corrosive may raise additivity issues and should be considered separately as to 

the mixing of corrosives and the subsequent classification / packing group assignment.

22. This paper poses the following questions to the GHS Sub-Committee to aid in 

developing revised text that would address the issues of additivity:

(a) Has the GHS Sub-Committee considered the effects of dilution of one 

corrosive with another corrosive? What methods exist to account for these potential 

synergistic effects when applying the classification principles outlined in 3.2.3.2.2. 

of the GHS?

Proposal

23. The questions raised in this proposal and directed at the GHS Sub-Committee are 

meant to stimulate discussion on issues that, if resolved, may lead to further harmonisation 

proposals of the Model Regulations with the GHS criteria for classification of corrosives.

24. It is proposed that Chapter 2.8 of the Model Regulations be replaced with the text in 

the attached annex to this document. The proposed section is aligned with the general 

format and approach utilised in the Model Regulations. It focuses on the packing group 

assignment of corrosive materials for transport, reviews work conducted in the previous 

biennium, and proposes a first step towards better harmonisation with Chapter 3.2 of the 

GHS.

25. New text is underlined in the proposal and deleted text is crossed-out.
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

7

Annex

Proposal for revision of Chapter 2.8 of the Model Regulations for 

harmonization with the GHS

CHAPTER 2.8

CLASS 8 – CORROSIVE SUBSTANCES

2.8.1 Definition and general provisions

2.8.1.1 Class 8 substances (c Corrosive substances) are substances which, by chemical 

action, will cause irreversible damage to the skin when in contact with living tissue, or, in the 

case of leakage, will materially damage, or even destroy, other goods or the means of transport. 

2.8.1.2 For substances and mixtures that are corrosive to skin, hazard classification is 

determined using criteria in section 2.8.2, where they will be assigned to a packing group. A 

substance is corrosive to skin when it leads to the destruction of skin tissue, namely, visible 

necrosis through the epidermis and into the dermis, in at least one tested animal after exposure 

for up to 4 hours. Hazard classification can alternatively be determined using section 2.8.3 for 

mixtures.

2.8.1.3 Liquids and solids which may become liquid during transport, which are judged 

not to be skin corrosive shall still be considered for their potential to cause corrosion to certain 

metal surfaces in accordance with the criteria in 2.8.2 (c) (ii).

2.8.2 Assignment of packing groups 

2.8.2.1 Substances and preparations mixtures of Class 8 are divided among the three 

packing groups according to their degree of hazard in transport as follows, in accordance with 

the following criteria:

(a) Packing group I: Very dangerous substances and preparations is assigned to 

substances and mixtures that cause full thickness destruction of intact skin tissue within 

an observation period up to 60 minutes starting after the exposure time of three (3) 

minutes or less;

(b) Packing group II: substances and preparations presenting medium danger is 

assigned to substances and mixtures that cause full thickness destruction of intact skin 

tissue within an observation period up to 14 days starting after the exposure time of 

more than three (3) minutes but not more than 60 minutes;

(c) Packing group III: Substances and preparations presenting minor danger is 

assigned to substances and mixtures that:

(i) cause full thickness destruction of intact skin tissue within an observation 

period up to 14 days starting after the exposure time of more than 60 minutes but 

not more than four (4) hours; or
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

8

(ii) are judged not to cause full thickness destruction of intact skin tissue but 

which exhibit a corrosion rate on either steel or aluminium surfaces exceeding 

6.25 mm a year at a test temperature of 55 °C when tested on both materials. For 

the purposes of testing steel, type S235JR+CR (1.0037 resp. St 37-2), 

S275J2G3+CR (1.0144 resp. St 44-3), ISO 3574 or Unified Numbering System 

(UNS) G10200 or a similar type or SAE 1020, and for testing aluminium, nonclad, types 7075–T6 or AZ5GU-T6 shall be used. An acceptable test is prescribed 

in the Manual of Tests and Criteria, Part III, Section 37.

NOTE: Where an initial test on either steel or aluminium indicates the substance 

being tested is corrosive the follow up test on the other metal is not required. 

Table 2.8.2.1: Table summarizing the criteria in 2.8.2.1

Packing

Group

Exposure

Time

Observation

Period Effect

I ≤ 3 min ≤ 60 min Full thickness destruction of intact skin

II > 3 min ≤ 1 h ≤ 14 d Full thickness destruction of intact skin

III > 1 h ≤ 4 h ≤ 14 d Full thickness destruction of intact skin

III - - Corrosion rate on either steel or aluminium 

surfaces exceeding 6.25 mm a year at a test 

temperature of 55 oC when tested on both 

materials

2.8.2.2 Allocation of substances listed in the Dangerous Goods List in Chapter 3.2 to the 

packing groups in Class 8 has been made on the basis of experience taking into account such 

additional factors as inhalation risk (see 2.8.2.3) and reactivity with water (including the 

formation of dangerous decomposition products). New substances, including mixtures, can be 

assigned to packing groups on the basis of the length of time of contact necessary to produce 

full thickness destruction of human skin in accordance with the criteria in 2.8.2.14; alternatively 

the criteria in 2.8.3 can also be used. Liquids and solids which may become liquid during 

transport, which are judged not to be skin corrosive shall still be considered for their potential to 

cause corrosion to certain metal surfaces in accordance with the criteria in 2.8.2.5 (c) (ii).

2.8.2.3 A substance or preparation meeting the criteria of Class 8 having an inhalation 

toxicity of dusts and mists (LC50) in the range of packing group I, but toxicity through oral 

ingestion or dermal contact only in the range of packing group III or less, shall be allocated to 

Class 8 (see note under 2.6.2.2.4.1).

2.8.2.4 In assigning the packing group to a substance in accordance with 2.8.2.2, account 

shall be taken of human experience in instances of accidental exposure. Except as provided in 

2.8.3, in the absence of human experience the grouping shall be based on data obtained from 

experiments in accordance with OECD Test Guideline 40410 or 43511. A substance which is 

10 OECD Guideline for the testing of chemicals No. 404 "Acute Dermal Irritation/Corrosion" 2002.

11 OECD Guideline for the testing of chemicals No. 435 "In Vitro Membrane Barrier Test Method for 

Skin Corrosion” 2006.
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

9

determined not to be corrosive in accordance with OECD Test Guideline 43012 or 43113 may be 

considered not to be corrosive to skin for the purposes of these Regulations without further 

testing.

2.8.2.5 Packing groups are assigned in accordance with the following criteria:

(a) Packing group I is assigned to substances that cause full thickness destruction of 

intact skin tissue within an observation period up to 60 minutes starting after the 

exposure time of three (3) minutes or less;

(b) Packing group II is assigned to substances that cause full thickness destruction of 

intact skin tissue within an observation period up to 14 days starting after the exposure 

time of more than three (3) minutes but not more than 60 minutes;

(c) Packing group III is assigned to substances that:

(a) cause full thickness destruction of intact skin tissue within an observation 

period up to 14 days starting after the exposure time of more than 60 minutes but 

not more than four (4) hours; or

(b) are judged not to cause full thickness destruction of intact skin tissue but 

which exhibit a corrosion rate on either steel or aluminium surfaces exceeding 

6.25 mm a year at a test temperature of 55 °C when tested on both materials. For 

the purposes of testing steel, type S235JR+CR (1.0037 resp. St 37-2), 

S275J2G3+CR (1.0144 resp. St 44-3), ISO 3574 or Unified Numbering System 

(UNS) G10200 or a similar type or SAE 1020, and for testing aluminium, nonclad, types 7075–T6 or AZ5GU-T6 shall be used. An acceptable test is prescribed 

in the Manual of Tests and Criteria, Part III, Section 37.

NOTE: Where an initial test on either steel or aluminium indicates the substance 

being tested is corrosive the follow up test on the other metal is not required. 

Table 2.8.2.5: Table summarizing the criteria in 2.8.2.5

Packing

Group

Exposure

Time

Observation

Period Effect

I ≤ 3 min ≤ 60 min Full thickness destruction of intact skin

II > 3 min ≤ 1 h ≤ 14 d Full thickness destruction of intact skin

III > 1 h ≤ 4 h ≤ 14 d Full thickness destruction of intact skin

III - - Corrosion rate on either steel or aluminium 

surfaces exceeding 6.25 mm a year at a test 

temperature of 55 oC when tested on both 

materials

12 OECD Guideline for the testing of chemicals No. 430 "In Vitro Skin Corrosion: Transcutaneous 

Electrical Resistance Test (TER)” 2004.

13 OECD Guideline for the testing of chemicals No. 431 "In Vitro Skin Corrosion: Human Skin Model 

Test" 2004.
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

10

2.8.3 Alternative hazard classification of mixtures corrosive to skin

2.8.3.1 Hazard classification of mixtures when data are available for the complete mixture

2.8.3.1.1 Where sufficient data is available for classification, the mixture shall be classified 

using the criteria for substances in 2.8.2.1 as illustrated in Table 2.8.2.1, if data is appropriate.

2.8.3.1.2 [Unless the consideration of acid/alkaline reserve14 suggests otherwise,] a mixture 

with an extreme pH of ≤ 2 and ≥ 11.5 may be considered to meet the criteria of Class 8 and 

assigned to PG I without further testing. 

2.8.3.2 Hazard classification of mixtures when data are not available for the complete mixture

2.8.3.2.1 Where a mixture has not been tested to determine its skin corrosion potential, but 

there are sufficient data on both the individual ingredients and similar tested mixtures to 

adequately classify the mixture, these data may be used in accordance with the following 

bridging principles:

(a) Dilution: Unless the consideration of synergistic or antagonistic effects suggests 

otherwise, if a tested mixture is diluted with a diluent which does not meet the criteria 

for Class 8 and does not affect the packing group of other ingredients, then the new 

diluted mixture may be assigned to the same packing group as the original tested 

mixture. 

(b) Batching: The skin corrosion potential of a tested production batch of a mixture 

may be assumed to be substantially equivalent to that of another untested production 

batch of the same commercial product when produced by or under the control of the 

same manufacturer, unless there is reason to believe there is significant variation such 

that the skin corrosion potential of the untested batch has changed. If the latter occurs, a 

new classification is necessary.

(c) Concentration of mixtures of packing group I: If a tested mixture meeting the 

criteria for inclusion in packing group I is concentrated, the more concentrated untested 

mixture may be assigned to packing group I without additional testing.

(d) Interpolation within one packing group: For three mixtures (X, Y and Z) with 

identical ingredients, where mixtures X and Y have been tested and are in the same skin 

corrosion packing group, and where untested mixture Z has the same active ingredients 

as mixtures X and Y but has concentrations of active ingredients intermediate to the 

concentrations in mixtures X and Y, then mixture Z is assumed to be in the same skin 

corrosion packing group as X and Y. 

(e) Substantially similar mixtures: 

Given the following:

14 [Acid/Alkaline reserve may be determined e.g. by the methodology detailed in Young J.R., How M.J., 

Walker A.P., Worth W.M.H. (1988): Classification as corrosive or irritant to skin of preparations 

containing acidic or alkaline substances, without testing on animals. Toxicology in Vitro 2, 19-26 and 

Young J.R., How M.J. (1994): Product classification as corrosive or irritant by measuring pH and acid / 

alkali reserve. In Alternative Methods in Toxicology vol. 10 - In Vitro Skin Toxicology: Irritation, 

Phototoxicity, Sensitization, eds. A.Rougier, A.M. Goldberg and H.I.Maibach, Mary Ann Liebert, Inc. 23-

27.]
ST/SG/AC.10/C.3/2015/21

ST/SG/AC.10/C.4/2015/2

11

(i) Two mixtures: (X + Y) and (Z+Y);

(ii) The concentration of ingredient Y is essentially the same in both mixtures;

(iii) The concentration of ingredient X in mixture (X+Y) equals the 

concentration of ingredient Z in mixture (Z+Y);

(iv) Data on skin corrosion for X and Z are available and substantially 

equivalent, i.e. they are in the same packing group and do not affect the skin 

corrosion potential of Y.

If mixture (X+Y) or (Z+Y) is already classified based on test data, then the other mixture may 

be assigned to the same packing group.