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potentially fostering misunderstanding 
of the issue and leading to unnecessary or inappropriate workplace ‘corrective’ actions’’ (Document ID 0330, pp. 3–5). 
OSHA disagrees with HTIW’s 
suggestion and with its conclusion that the hazard presented by RCF should be excluded from Section 2 because, as HTIW explained in its example, RCF may form crystalline silica dust in the process. Section 2 requirements are set to address these very types of situations. Manufacturers must provide additional information on toxicity, if known, in Section 11, and may provide additional information in Section 16. However, any hazard information must be included in Section 2. Classification is based on the intrinsic properties of the chemical, not the anticipated level of exposure in the workplace, except in cases where the chemical is bound in such a way as to be incapable of resulting in exposure (see OSHA, Feb. 10, 2015, Letter of Interpretation, available at https://
www.osha.gov/laws-regs/standardinterpretations/2015-02-10-0). OSHA, therefore, does not agree that hazards from downstream chemical reactions may be addressed solely in Section 16 under the circumstances described by HTIW. 
Finally, OSHA received a question 
pertaining to Section 2 (e), which addresses requirements for stating the percentage of ingredients of unknown toxicity in a mixture. The anonymous commenter noted that Appendix A paragraph A.1.3.6.2.3, Appendix C paragraph C.3.3, and Appendix D of the proposed standard require a statement of the concentration of ingredients of unknown acute toxicity to appear in Section 2 of the SDS and on the label. They asked, in the case of a mixture for which the exact concentration(s) of hazardous component(s) are withheld as trade secrets and are reported as prescribed concentration range(s) in Section 3 of the SDS, in accordance with proposed paragraph (i)(1)(iv), whether it would be permissible to report the percentage of ingredient(s) of unknown acute toxicity as a range corresponding to one of the prescribed ranges in Section 2 of the SDS, or whether the exact percentage of those ingredients must be reported (Document ID 0266). 
Manufacturers are required to state 
the exact percentage of a mixture that is 
composed of ingredients of unknown acute toxicity if the concentration of at least one such ingredient is ≥ one 
percent and the mixture is not classified based on testing of the mixture as a whole. In this case, manufacturers are not required to report the individual concentrations of ingredients with unknown toxicity in Section 2, but 
rather the total percentage of unknown toxicity, which may include multiple chemicals. They may not use the prescribed ranges included in paragraph (i) for the purpose of reporting the concentration of unknown acute toxicity. To the extent that this presents concerns for CBI due to a single 
chemical having unknown toxicity, 
OSHA notes that SDS preparers still have the option to withhold the name of that chemical. 
Based on the comments received, 
OSHA is finalizing different language from its proposal in Section 2, as described above, to more accurately convey its intent and align the text of Section 2 with the revised regulatory text of paragraph (d)(1). 
IV. Section 3: Composition/Information 
on Ingredients 
Section 3 of the SDS contains 
information on the composition of the chemical and its ingredients, with specific requirements for substances and mixtures, as well as for chemicals where a trade secret is claimed. In the NPRM, OSHA proposed several changes to this section. Under the subheading For 
Substances OSHA proposed to add 
‘‘(constituents)’’ to paragraph (d) to clarify the term ‘‘additives.’’ The intention of this proposal was to clarify that any individual part of an ‘‘additive’’ that contributes to the classification of that material needs to be listed in Section 3 of the SDS. OSHA received no comments objecting to the addition of ‘‘(constituents)’’ in Section 3 and is 
therefore finalizing it as proposed. 
OSHA also proposed to revise the 
information required for mixtures. Section 3 requires, among other things, the chemical name of each ingredient in a mixture that is classified as a health hazard. OSHA proposed requiring the inclusion of the CAS number or other unique identifier for these ingredients. As noted in the NPRM, CAS numbers are unique numerical identifiers assigned by the American Chemical Society (ACS), internationally recognized as being reliable and readily validated; unique to only one compound, substance or chemical; and a common link between various nomenclatures that may be used as descriptors for a substance or compound (86 FR 9722). OSHA believes that the proposed requirement would provide the downstream user with important 
information, since it provides a unique 
descriptor of the chemical, whereas the 
chemical identity may be ambiguous. 
PLASTICS and API supported the 
proposed requirement to include the CAS number or other unique identifier for ingredients in mixtures (Document 
ID 0314, p. 21; 0316, p. 28). ICT commented that CAS numbers are not assigned to all chemicals and accession numbers exist only for substances on the confidential TSCA inventory and therefore identifying numbers may not be available for all chemicals which SDS preparers are required to disclose in Section 3. ICT suggested that OSHA should allow manufacturers to use ‘‘not available’’ for those chemicals without identifying numbers (Document ID 0324, p. 6). 
OSHA recognizes that a CAS number 
may not be available for all chemicals. OSHA notes, however, that the proposal required manufacturers to provide CAS or other unique identifier numbers for hazardous ingredients. While OSHA intends that CAS numbers be provided when available, in cases where a CAS number is not available or is protected as CBI, another unique identifier must be provided. For example, an identification number used internally by the manufacturer ( e.g., product number) 
can be used to identify the ingredient upon request in emergency and non- emergency situations. Accordingly, OSHA disagrees with ICT’s concern that SDS preparers will be unable to provide an appropriate unique identifier. 
However, ICT’s comment does raise 
the concern that in choosing an identifier, an SDS preparer might select one for which the source is not readily apparent. Certain product numbers or other identifiers used internally by the manufacturer may be of little use when placed on the SDS without context. Though OSHA proposed to permit the use of ‘‘other unique identifiers’’ for mixtures in Section 3 of the SDS, the agency wishes to clarify that it would only consider such a number to be an adequate identifier if it can actually be used by downstream recipients of the SDS to identify the chemical. Accordingly, OSHA has added a requirement in the final rule that, where a preparer of an SDS uses a unique identifier other than a CAS number, they must include the source of that unique identifier. This will ensure that any unique identifier functions as such for recipients of the SDS. OSHA is finalizing this language with the changes described above. 
OSHA also proposed a set of changes 
in Section 3 to reflect the proposed 
revision to paragraph (i), Trade secrets, which would allow companies to withhold concentration ranges as a trade secret. Under the proposed language in Section 3, when a company withholds the concentration or concentration range as a trade secret, it must provide a chemical concentration range in 
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accordance with the prescribed 
concentration ranges in paragraph (i)(1)(iv). 
OSHA received a variety of comments 
about the proposed revisions to paragraph (i), which the agency addressed in the Summary and Explanation for paragraph (i). Ameren supported the proposed changes to Section 3 of the SDS, stating that the changes could allow downstream manufacturers to more accurately classify their products where the mixture in question is one of their ingredients (Document ID 0309, p. 13). Toby Threet commented that the language in this section on trade secrets needed clarification. First, Threet noted that the word ‘‘or’’ in the phrase ‘‘. . . the specific chemical identity, exact percentage (concentration), or concentration range of composition has been withheld as a trade secret is required . . .’’ could imply that a trade secret may be claimed for only one of these three categories. Threet suggested that it is possible that both the specific chemical identity and either the exact concentration or the concentration range may need to be withheld and therefore an ‘‘and/or’’ should be inserted in an appropriate location in the sentence (Document ID 0279, p. 24). 
Toby Threet also commented that in 
the proposed language, the word ‘‘composition’’ normally refers to or includes chemical identities but in the proposed text, the word is used twice to refer to the concentration. Threet suggested that this could cause confusion and SDS preparers may believe that when the concentration of chemical is withheld, the chemical identity must be disclosed. Further, Threet suggested that the proposed language implied that an SDS could merely acknowledge that something was withheld as a trade secret but not specify which category of information was withheld, and recommended that OSHA add ‘‘as appropriate’’ to clarify (Document ID 0279, pp. 24–25). 
ICBA commented that the proposed 
language, which states the chemical composition must be provided in accordance with the prescribed concentration ranges, did not align with the language in paragraph (i)(1)(iv), which requires that the concentration must be provided in accordance with 
the prescribed ranges. ICBA expressed concern that requiring the chemical composition as part of the concentration ranges could reveal industry trade secrets, and requested that OSHA change the language in Appendix D to reflect the same requirement as paragraph (i)(1)(iv) (Document ID 0291, pp. 4–5). Michele Sullivan asked OSHA to clarify that both the specific chemical 
identity and the percentage concentration or concentration range can be claimed as trade secrets at the same time (Document ID 0366, p. 9). 
After reviewing comments from 
stakeholders, OSHA is modifying the proposed text under For All Chemicals Where a Trade Secret is Claimed in 
Section 3 of Table D.1. OSHA is adding 
‘‘and/or’’ to the first sentence and 
modifying the language about concentrations to read ‘‘When a trade secret is claimed in accordance with paragraph (i) of § 1900.1200, a statement that the specific chemical identity, and/ or concentration (exact or range) of the composition has been withheld as a trade secret is required.’’ This should clarify that manufacturers can claim the chemical identity and the concentration (exact or range) as trade secrets at the same time or can claim any subset of these as a trade secret. OSHA also agrees with the comments regarding the use of the term ‘‘composition’’ in the second sentence and has accordingly reworded to clarify that when the concentration or concentration range is withheld as a trade secret, the HCS requires SDS preparers to use the prescribed concentration ranges in § 1910.1200(f)(1)(iv)–(vi) in Section 3. OSHA is not, however, adding ‘‘as appropriate’’ to the first sentence because the proposed language already makes clear that the SDS must include a statement about which information is withheld as a trade secret. OSHA is finalizing this version of the language regarding trade secrets in Section 3. 
In addition, as described in the 
NPRM, the HCS requires Section 3 of the SDS to include the chemical name and concentration (exact percentage or ranges) of all ingredients which are classified as ‘‘health hazards’’ in accordance with paragraph (d). OSHA did not propose changes to this requirement but requested comments on whether the requirement should be expanded to also include chemicals classified as physical hazards and HNOCs. In particular, OSHA asked whether expanding the requirements for Section 3 in this way would ensure that both users and manufacturers fully understand any potential hazard when handling the chemical and whether 
such a change would result in the provision of additional information that would allow downstream manufacturers to more accurately classify their 
products where a mixture with an 
ingredient that presents a physical 
hazard or HNOC is one of their ingredients (86 FR 9689). 
NIOSH supported expanding Section 
3’s requirements to all classified chemicals for its potential to improve 
worker safety (Document ID 0281, Att. 2, p. 6; 0423, Tr. 24). Similarly, John Baker supported the change, noting it would be beneficial particularly because of the potential for some nanoscale materials to form combustible dusts (Document ID 0302). NABTU also stated that OSHA should expand the requirements and that doing so would provide construction workers and their employers with more complete information on all exposure hazards. NABTU commented that ‘‘specifying physical hazards will also require more careful examination of potentially deleterious effects to workers beyond health effects’’ and noted that construction workers would benefit from additional information about a variety of hazards, such as aerosols, flammable gases and liquids, and HNOCs. NABTU also expressed the belief that the HNOC classification would be used infrequently (Document ID 0334, pp. 2–3; 0425, Tr. 23). 
Several commenters opposed 
expanding the requirements of Section 3 to include ingredients classified as presenting physical hazards or HNOCs (see, e.g., Document ID 0293; 0316, pp. 28–29; 0327, p. 7; 0345, p. 6; 0346, pp. 2–3; 0347, pp. 22–23; 0359, p. 6; 0361, p. 3; 0366, p. 9). Several commenters stated that because the physical hazards of a mixture as a whole cannot be determined based on the physical properties of its ingredients, this requirement would only add complexity to the SDS without increasing worker protection, and could make it harder for workers to find relevant information (Document ID 0293; 0327, p. 7; 0329, p. 9; 0345, p. 6; 0346, pp. 2–3; 0347, pp. 22–23; 0359, p. 6; 0366, p. 9). 
Givaudan, Dow, ACC, and Michele 
Sullivan recommended against expanding Section 3’s requirements because it would be inconsistent with the GHS and requirements of other U.S. trade partners (Document ID 0293; 0347, p. 22; 0359, p. 6; 0366, p. 9). Dow noted that doing so could put the United States at a competitive disadvantage since some of these components may be considered intellectual property (Document ID 0359, p. 6). The Flavor and Extract Manufacturers Association, HCPA, NACD, and ADM also stated that expanding the Section 3 requirements would not provide any additional helpful information regarding safe handling of chemicals because other sections of the SDS provide that information (Document ID 0327, p. 7; 0329, p. 9; 0346, pp. 2–3; 0347, pp. 22– 23; 0361, p. 3). NAIMA opposed 
expanding Section 3 requirements, noting that doing so would impose 
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significant burdens (Document ID 0338, 
p. 10). OSHA appreciates stakeholders’ response to its request for comments. OSHA will consider these comments in determining whether Section 3’s requirements should be expanded in a future update. 
OSHA received one comment from an 
anonymous commenter about inaccurate information presented in Section 3 of SDSs. The commenter provided examples of inaccurate information such as SDSs listing chemical composition as ‘‘100% fertilizer’’ or ‘‘mixture,’’ and not providing accurate nutrient percentages (Document ID 0308). Although this comment is beyond the scope of this rulemaking because it does not relate to OSHA’s proposed updates to the HCS, OSHA notes that many of the changes in this final rule are intended to clarify the requirements of the HCS for SDS preparers, in order to improve the accuracy of SDSs. 
OSHA received a request from 
PRINTING regarding the existing requirement to list impurities and stabilizing additives. PRINTING requested guidance stating that downstream manufacturers may continue to rely on information provided by their upstream suppliers. (Document ID 0357, p. 3; 0423, Tr. 184– 185). OSHA agrees that its modifications to paragraph (d) and Appendix D, Table D.1 Section 3 have not altered the ability of downstream manufacturers to rely on information from upstream 
suppliers. 
V. Section 8: Exposure Controls/ 
Personal Protection 
Section 8 of the SDS includes 
information on exposure controls and personal protection. Section 8 (a) requires the SDS to include the OSHA PEL, the ACGIH TLV, and any other exposure limit used or recommended by the chemical manufacturer, importer, or employer preparing the SDS, when available. OSHA proposed to revise Section 8 (a) to clarify that this requirement applies to all ingredients or constituents listed in Section 3 regardless of the concentration at which they are present in a mixture. As OSHA noted in the NPRM, however, if the ingredient or constituent does not have an OSHA PEL, ACGIH TLV, or any other exposure limit or range used or recommended by the SDS preparer, then the ingredient or constituent would not need to be listed in Section 8. 
Several commenters supported this 
proposed revision to Section 8 (a) (Document ID 0313, p. 8; 0316, p. 29; 0338, pp. 8–9). Specifically, NAIMA strongly supported the proposed revision and pointed out that sharing 
information about PELs and TLVs with users communicates a clear message about appropriate protections and supports intelligent and informed choice on the use of respiratory protection (Document ID 0338, pp. 8–9). 
The American Pyrotechnics 
Association (APA) described the proposal as ‘‘adding known permissible exposure limits (PELs) and Threshold Limit Values (TLVs) for every ingredient 
or constituent listed in Section 3 of the 
SDS . . .’’ and argued that PELs and TLVs are irrelevant for finished pyrotechnic products because (1) these products are designed to combust and are consumed by the reaction before any personal exposure can occur and (2) if the products broke open in the workplace workers would not be exposed to the chemicals themselves. APA added that they ‘‘believe this is also applicable to numerous mixtures and compositions wherein the hazardous substances do not segregate nor return to their separate ingredients after being bound together chemically and/or physically’’ and that including numerous PELs and TLVs would lengthen the SDS. They requested that OSHA revisit this proposal (Document ID 0337, p. 4). 
APA’s comment that OSHA has 
‘‘proposed adding’’ known PELs and TLVs for every ingredient or constituent misconstrues the nature of OSHA’s proposal. Following the publication of the 2012 HCS, the agency received requests to clarify how an ingredient’s concentration and role in hazard classification relate to Section 8 requirements and requirements to list the ingredients in Section 3 and, as discussed in the NPRM (86 FR 9722), OSHA has issued LOIs clarifying that the required exposure limits must be provided for any ingredient or constituent identified in Section 3 of the SDS (see, e.g., Document ID 0088). 
OSHA’s proposal in this rulemaking thus does not change any existing requirements; it simply clarifies which 
ingredients Section 8 (a) applies to. 
In addition, OSHA is not persuaded 
by APA’s argument that the consumption of chemicals contained in 
pyrotechnic products during their use 
precludes occupational exposure to 
those chemicals. APA provided no 
evidence demonstrating that the consumption of chemical components during use of pyrotechnics results in no exposures to individuals in the vicinity. Furthermore, APA’s comment specifically references circumstances where workers can experience exposure to hazardous chemical components of pyrotechnic products: such products can rupture in the workplace and 
workers must clean up the spilled materials resulting from such accidents. For the reasons discussed above, OSHA declines APA’s request to reconsider the application of Section 8 (a)’s requirements to individual ingredients of chemical mixtures. 
Therefore, after reviewing the 
comments received on the inclusion of the proposed language in Section 8 (a) to clarify that this requirement applies to all ingredients or constituents listed in Section 3 regardless of the concentration, OSHA is finalizing the requirement as proposed. 
OSHA also proposed to add a new 
requirement for SDS preparers to include a range of exposure limits in Section 8 whenever a range is used or recommended by the chemical manufacturer, importer, or employer preparing the SDS. As explained in the NPRM, OSHA proposed this requirement due to the availability of new tools, such as occupational exposure banding or hazard banding methods, that provide a concentration range (band) based on toxicity and hazard information associated with a known chemical with similar properties. This range can help inform appropriate risk management decisions where a specific occupational exposure limit (OEL) or PEL is not available or is out of date (86 FR 9722). 
NIOSH, NABTU, and John Baker 
supported the proposed revision (Document ID 0281, Att. 2, p. 6; 0302; 0334, p. 3; 0425, Tr. 23–24). NABTU stated that, since quantitative and health-based occupational exposure limits are only available for a small number of chemicals, the inclusion of a range of exposure limits such as occupational exposure banding improves hazard communication and safeguards workers. NABTU added that exposure banding would move OSHA closer to the precautionary principle embodied in the EU’s REACH regulations that is intended to protect 
workers when uncertainty exists about chemical hazards (Document ID 0334, p. 3; 0425, Tr. 23–24). 
John Baker recommended that the 
SDS should include a hyperlink or other instructions on where the user can find supporting documentation regarding how the range was established. Baker gave the example of ranges established for nanomaterials, stating that these may be highly dependent on parameters selected for the banding analysis (Document ID 0302). OSHA agrees that supporting documentation can provide valuable information about exposure ranges. However, based on the format of and preparation process for SDSs the 
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agency does not believe it is practical to 
require inclusion of this information. Maintaining accurate and up-to-date hyperlinks and/or instructions on where to locate appropriate contextual information can be burdensome for SDS preparers, and employees who only have access to paper copies of SDSs would not be able to use hyperlinks or similar instructions to find supporting documentation. OSHA also notes that SDS preparers may provide information on supporting documentation to users in Section 16 of the SDS. OSHA is therefore not mandating inclusion of a hyperlink or instructions for locating supporting information on how the range was established. 
OSHA received no comments 
objecting to the proposed requirement for SDS preparers to include a range of exposure limits whenever a range is used or recommended by the chemical manufacturer, importer, or employer preparing the SDS, and is finalizing the requirement as proposed. 
Several commenters did not oppose 
the proposed revisions but suggested additional changes to the section. NIOSH recommended adding the NIOSH Recommended Exposure Limit (REL) to the list of relevant exposure limits, noting NIOSH is the only organization that offers OELs in some cases, such as engineered nanomaterials (Document ID 0281, Att. 2, p. 6; 0423, Tr. 24). NABTU similarly stated that, because few occupational exposure limits for engineered nanomaterials have been established, NIOSH RELs should be required on SDSs to convey the most accurate and appropriate hazard information for engineered nanomaterials (Document ID 0464, p. 7). Cal/HESIS also recommended adding the NIOSH REL to the list of occupational exposure limits, as well as California’s Risk Management Limit for Carcinogens (RML–CA). Cal/HESIS further recommended requiring state- or territory-specific PELs (such as Cal/ OSHA PELs) to be listed for substances that lack federal occupational exposure limits and are sold in a particular state with an OSHA-approved State Plan. Cal/HESIS reasoned that SDSs should advise employers and workers that an exposure limit has been established by a specific state or other non-regulatory organization for a substance, even if a PEL is not established by federal OSHA. Cal/HESIS provided supporting information from its review of SDSs for products sold in California that contained 1-bromopropane, a carcinogen that lacks a federal OSHA PEL, and the agency found that 80 
percent of SDSs did not include the Cal/ OSHA PEL for 1-bromopropane. Therefore, Cal/HESIS concluded, 
California users of these SDSs could erroneously conclude California does not regulate 1-bromopropane (Document ID 0313, p. 8). 
ICT suggested that OSHA should add 
a provision from Section G.5.d of OSHA’s compliance directive (Document ID 0007), which allows chemical manufacturers and importers to state ‘‘The following constituents are 
the only constituents of the product 
which have a PEL, TLV or other recommended exposure limit. At this time, the other constituents have no known exposure limits’’ in Section 8 of the SDS (Document ID 0066, p. 66). ICT requested that OSHA modify Section 8 to codify this language, noting that Section 3 of the SDS often contains substances that do not have established OELs (Document ID 0324, pp. 6–7). 
OSHA agrees with those commenters 
who stated that the NIOSH REL and state-specific limits can provide important information to chemical users; however, the suggested changes are out of scope for this rulemaking. While OSHA did propose to add ‘‘or range’’ to Section 8, indicating a broader scope of what needs to be listed, it did not propose to add RELs or otherwise modify the information required regarding OELs. Adding these limits as requirements would be a substantive change to the content of an SDS. Because OSHA did not indicate in the proposal that it was considering such a change, the agency believes stakeholders lacked sufficient notice for OSHA to adopt the commenters’ suggestions in this final rule. The agency notes, however, that Section 8 (a) may include any exposure limit or range used or recommended by the chemical manufacturer, importer, or employer preparing the safety data sheet, where available. 
With regard to ICT’s request to add 
language from OSHA’s directive, OSHA notes that ICT did not provide any justification for why adding this 
language to the HCS text of Appendix D would be useful and OSHA has not received any other comments suggesting that there is ambiguity about the fact that employers are allowed to add that statement. To the extent that ICT is requesting that OSHA mandate the inclusion of that statement about no 
other known exposure limits on SDSs, 
OSHA did not propose such a change 
and the agency considers such a 
suggestion outside the scope of this 
rulemaking. 
ACC submitted a comment requesting 
that OSHA remove the requirement to list OELs developed by voluntary 
standards organizations such as ACGIH TLVs. ACC suggested that OSHA should 
only require the listing of OELs that have been developed through a federal rulemaking process because those limits have been determined to be feasible. ACC argued that the requirement to include OELs developed by voluntary standards organizations creates the erroneous impression that they carry the same regulatory weight as OSHA PELs (Document ID 0347, p. 24). 
Inclusion of the TLVs and other OELs 
on the SDS has been a requirement since 1983 (48 FR 53280, 53343). During the rulemaking process for the 2012 HCS, OSHA received comments similar to ACC’s; the agency explained and reaffirmed its longstanding position that TLVs and other OELs provide useful information and should continue to be included (77 FR 17573, 17731–34). OSHA continues to affirm this position. Regardless, this comment is out of scope because the agency did not propose a change to this requirement. 
OSHA also received one comment 
regarding Section 8 (c), which the agency did not propose to change in the NPRM. Monica Hale commented that OSHA should add a requirement for manufacturers to list the specific types of required PPE in Section 8 based on the ‘‘actual hazard’’ and should not be permitted to include generic statements such as ‘‘use appropriate glove’’ or ‘‘use appropriate NIOSH Approved Respirator’’ (Document ID 0286). Because OSHA did not propose to change Section 8(c), this comment is out 
of scope for this rulemaking and the agency has not added the suggested language. Several other commenters raised similar concerns with regard to the language about PPE required on labels in Appendix C, and this issue is discussed in more depth in the Summary and Explanation of Appendix C. 
In conclusion, for the reasons 
discussed above, OSHA is finalizing all changes as proposed in Section 8 of the SDS. 
VI. Section 9: Physical and Chemical 
Properties 
OSHA proposed several updates to 
Section 9, Physical and chemical properties. OSHA proposed to revise the text of Section 9 to align with Rev. 7 by listing the required physical and chemical properties of the chemical in the same order that appears in Annex 4 of the GHS (Document ID 0060, p. 38). OSHA reasoned that this change would simplify the preparation of SDSs for chemical manufacturers who prepare them for global distribution. Similarly, OSHA also proposed aligning Section 9 with Rev. 7 by replacing ‘‘appearance’’ 
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with ‘‘physical state’’ and ‘‘color’’; 
eliminating ‘‘odor threshold’’ and ‘‘evaporation rate’’ as separate required properties; adding the term ‘‘kinematic’’ to the property ‘‘viscosity’’ to better define the appropriate parameter to be characterized (i.e., kinematic as opposed 
to dynamic viscosity); and adding ‘‘particle characteristics’’ as a new physical property for solids. OSHA stated in the NPRM that particle characteristics only apply to solids and should include the particle size (median and range) and, if available and appropriate, further properties such as size distribution (range), shape, aspect ratio, and specific surface area (86 FR 9723). 
OSHA received several comments on 
these proposed changes. API requested clarification on whether the physical and chemical properties must be ordered on the SDS in the same sequence that OSHA proposed to list them in the text of Appendix D (Document ID 0316, pp. 29–30). NACD expressed concern that individuals who read SDSs and labels would need to adjust to a re-ordered list of physical and chemical properties and that making this change would not enhance safety (Document ID 0329, p. 9). 
As OSHA explained in the NPRM, the 
proposal to list the required physical and chemical properties of the chemical in the same order that appears in the GHS applies to the order in which they appear in the text of the HCS, not to the order in which they appear on the SDS. SDS preparers are not required to list the physical and chemical properties in any particular order (86 FR 9722–9723). This also means that the order of the physical and chemical properties on the SDSs would not need to change and therefore individuals who use SDSs would not need to adjust or relearn anything about where the information is located. 
NIOSH recommended that 
information on odor threshold be retained on the SDS because detection of odor can be usefully combined with other information on toxic potency, for example, in cases where an odor threshold concentration can be compared to health-based ambient criteria (Document ID 0281, Att. 2, p. 7). Cal/OSHA commented that since odor threshold can be an important way to 
‘‘roughly’’ assess the risk level, it should be provided for all chemicals. Cal/ OSHA recommended retaining the odor threshold along with a statement regarding olfactory fatigue (Document ID 0322, Att. 2, p. 13). NIOSH and Cal/ HESIS commented that, since the evaporation rate can be important for assessing the risk from material spills, it should be retained on the SDS 
(Document ID 0281, Att. 2, p. 7; 0423, Tr. 24–25; 0313, p. 9). 
OSHA did not intend to eliminate the 
requirement to state the odor threshold on the SDS. The agency proposed to remove ‘‘Odor threshold’’ as a separate property from Section 9 in order to align with Rev. 7, which does not require an ‘‘Odor threshold’’ property in Section 9. 
However, Annex 4 of Rev. 7 states that 
a substance’s odor property should indicate the odor threshold, if available (Document ID 0060, p. 387). OSHA’s intent was to align with Rev. 7 by eliminating ‘‘odor threshold’’ from the list of properties but maintaining the requirement to report it by requiring it under the existing odor property already in Section 9. To prevent any future confusion, OSHA is adding a parenthetical stating ‘‘includes odor threshold’’ in Section 9 (c) Odor, thus indicating that SDSs preparers need to specify odor threshold for the substance, if available. OSHA is declining the recommendation to require a statement regarding olfactory fatigue since this recommendation does not align with Rev. 7 and Section 9 information requirements are limited to physical and chemical properties. However, OSHA notes that manufacturers may elect to include a statement regarding olfactory fatigue. 
With regard to evaporation rate, 
OSHA did propose to remove it from the list of properties in Section 9 to align with Rev. 7. The UNSCEGHS agreed to remove ‘‘evaporation rate’’ during revision of the GHS Annex 4 on the basis that it ‘‘is effectively covered by the vapour pressure, and all aspects that are important with regard to occupational safety and the risk of exposure can be dealt with based on the vapour pressure and the saturated vapour concentration’’ (Document ID 0129, p. 3). However, OSHA agrees with the point made by NIOSH and Cal/ HESIS that ‘‘Evaporation rate’’ is important to include in Section 9, as ready access to this information may be needed to evaluate the health and fire hazard qualities of chemicals and other substances in emergency situations. OSHA is therefore adding a parenthesis stating ‘‘includes evaporation rate’’ in Section 9 (o), Vapor pressure. 
NIOSH, Cal/HESIS, NABTU and John 
Baker supported the addition of 
‘‘particle characteristics’’ as a new physical property in Section 9 (Document ID 0281, p. 7; 0313, pp. 8– 9; 0302; 0423, Tr. 24; 0425, Tr. 24; 0464, p. 7). Cal/HESIS recommended that the proposed text should be revised to specifically include particle size distribution as a required type of particle characteristic, noting that 
particle size is an important determinant of particle behavior in air and how the inhaled particles are deposited in the respiratory system (Document ID 0313, pp. 8–9). NIOSH stated that ‘‘particle characteristics are critical determinants of the toxicity of inhaled particles’’ and provided suggested particle characteristics with standardized methods (Document ID 0456, Att. 2, p. 3). NIOSH suggested that surface reactivity and density are also important determinants of the toxicity of particles, and suggested standardized test methods for those measurements (Document ID 0456, Att. 2, p. 3). In addition, NIOSH stated that over the last 20 years particle characteristics have become critical in terms of their hazard potential and the kinds of control approaches that are needed, particularly with the advancement of commercial nanotechnology (Document ID 0423, Tr. 40–41). NABTU concurred with NIOSH’s assertion and pointed out that manufacturers are utilizing nanoparticles (or engineered nanomaterials) increasingly in numerous industry sectors, but not necessarily including information about nanoparticles in SDSs, and there is a clear need to improve hazard communication concerning particle size and other particle characteristics in order to understand the associated hazards to construction workers (Document ID 0425, Tr. 24; 0464, p. 7). 
OSHA agrees that particle size 
distribution can be an important indicator of the potential for a solid particle to pose a hazard; as discussed in the NPRM, particles that are less than 100 microns increase the likelihood of exposure, especially through the route of inhalation (86 FR 9723; Document ID 0060, p. 117; 0129). OSHA also agrees with NIOSH regarding surface reactivity and density; if information on these characteristics is available, it should be included in the SDS. OSHA is not, however, including a list of particle characteristics that must be included because not all of this information is available for all chemicals covered by this provision. Additionally, because the HCS does not require testing, OSHA is not requiring testing for particle characteristics as NIOSH suggested, but notes that manufacturers must include these measurements, if available. 
John Baker argued that the proposed 
requirement to provide particle characteristics to Section 9 of the SDS should not be restricted to solids because liquids containing nanoparticles could pose a hazard 
particularly if there is a change in physical form (Document ID 0302). 
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OSHA recognizes that solid 
nanoparticles in liquid can pose a 
hazard, especially when the liquid is aerosolized and the nanoparticles become airborne. In the NPRM, when OSHA stated that ‘‘particle characteristics apply to solids only . . .,’’ it intended to include nanoparticles in its meaning of solid (86 FR 9723). Nanoparticles in a liquid are themselves in a solid form, and therefore SDS preparers are required to list characteristics of those nanoparticles in Section 9. 
Some commenters expressed 
confusion over the addition of ‘‘particle characteristics.’’ ICBA and PLASTICS asked for clarification about what data OSHA is seeking to capture by adding this term to Section 9 (Document ID 0291, p. 5; 0314, p. 21). As noted above, OSHA included in the NPRM a list of particle characteristics it intended for SDS preparers to provide, when available, and agrees with NIOSH that surface reactivity and density are also relevant particle characteristics that should be included. 
NAIMA opposed the addition of 
‘‘particle characteristics’’ as a new physical property in Section 9, including the proposed requirements to include median and range of particle size, size distribution, aspect ratio, and specific surface area. According to NAIMA, these particle characteristics are highly sensitive to certain production characteristics, and it would be hard to address attrition that might occur during application (Document ID 0338, p. 8). 
In response to NAIMA’s comment, 
OSHA notes that the requirement pertaining to particle characteristics is limited to cases where a substance’s particle characteristics are available and appropriate. If particle characteristics are not known, OSHA does not expect importers or manufacturers to perform testing to determine particle characteristics, consistent with the fact that the HCS does not require testing. However, the agency notes that many manufacturers already have this information available since this is an important commercial attribute provided to customers. Additionally, OSHA would not expect the SDS preparer to include the particle characteristics following attrition that could occur during downstream processing since, as NAIMA pointed out, this would be difficult to predict for all situations. 
For the reasons discussed above, 
OSHA is finalizing the proposed revisions with clarifying additions in Section 9 (c) and (o). VII. Footnote in Sections 7 and 9 
OSHA requested comments on 
whether it should add a footnote to Section 9 that is similar to the footnote the agency proposed to add to Appendix B.6.3. This footnote would explain that to determine the appropriate storage container size and type, the boiling point for a flammable liquid must be determined by paragraph (a)(5) of OSHA’s Flammable Liquids standard (29 CFR 1910.106(a)(5)), which allows for an alternate method to determine the boiling point under certain circumstances. If a manufacturer uses the alternative method to determine the boiling point for storage purposes, they must note that on the SDS in Sections 7 and 9 if the classification for storage differs from the classification listed in Section 2 of the SDS. 
ACC objected to the proposed note, 
including the requirements pertaining to Sections 7 and 9 of the SDS, because they believe that it would not provide any additional worker protection. ACC further asked OSHA to clarify why this provision was proposed, noting that it is not in the GHS Rev. 7 or 8 (Document ID 0347, p. 23). OSHA addressed ACC’s comments, along with other comments specifically on the footnote in B.6.3, in the Summary and Explanation for Appendix B and finalized the footnote, with modifications for clarity. 
OSHA received one comment 
specifically on the addition of the 
footnote to Appendix D, from Ameren, 
which agreed that it would be appropriate to add a footnote like the one proposed for B.6.3 to Appendix D for Section 9 (Document ID 0309, p. 17). OSHA agrees that a similar footnote should be included in Appendix D since Appendix D, Table D.1 lists what must be included in the SDS, and the footnote requires that in some cases this additional information is added to the SDS. However, OSHA has concluded that the footnote should be referenced in both Section 7 and Section 9, since it refers to information in both SDS sections. Adding the footnote, as modified, will ensure that if the storage recommendations appear to be in conflict with classification for flammable liquids in section 2 of the SDS, the preparer will appropriately mark the SDS in both Section 7 and Section 9 so the downstream user knows that the recommendations for storage of flammable liquids are correct. While OSHA believes this will be a rare occurrence, the addition of the use of the alternative method for boiling point ensures that the accuracy of the SDS is not in doubt. Therefore, OSHA is adding the footnote, as modified for B.6.3, in 
Appendix D. 
VIII. Section 10: Stability and Reactivity 
Section 10 of the SDS, Stability and 
reactivity, includes the requirement in 
Section 10 (c) that preparers include information about the possibility of 
hazardous reactions. In the NPRM, 
OSHA proposed to clarify that this includes hazardous reactions associated with foreseeable emergencies. 
OSHA received several comments 
expressing concerns about the proposed requirement. These arguments largely mirror the arguments raised regarding paragraph (d). For instance, commenters raised concerns about the feasibility of preparing comprehensive hazard classifications for every possible use of a product (Document ID 0277, p. 3); the vagueness and breadth of the language proposed (Document ID 0347, pp. 25– 26); the difficulty of obtaining continuous information from downstream users (Document ID 0348, p. 2); and the likelihood of over- warnings to avoid risk of regulatory citations and confusion about what hazards are associated with a chemical substance (Document ID 0356, pp. 9– 10). These arguments and others are discussed further in the Summary and Explanation for paragraph (d). 
Several commenters also suggested 
changes to the proposed text. Tom Murphy suggested that Section 10 (c) should be limited to universal conditions applicable to anyone in possession of the chemical product (Document ID 0277, p. 3). ACC suggested adding the phrase ‘‘for 
directed uses’’ (Document ID 0347, pp. 25–26). The Vinyl Institute suggested removing the proposed text from Section 10 of Table D.1 for the same reason they opposed the proposed revisions to paragraph (d) (Document ID 0369, Att. 2, p. 8) (see the Summary and Explanation of paragraph (d)). 
The proposed change in Section 10 (c) 
was consistent with the language OSHA proposed for paragraph (d)(1). OSHA proposed to add ‘‘including those associated with foreseeable emergencies’’ in Section 10 (c) to clarify that possible hazardous reactions also include hazardous reactions which may occur during foreseeable emergencies and to be consistent with the proposed revision to paragraph (d)(1). While the version of paragraph (d)(1) that OSHA is finalizing no longer aligns with the proposed change in 10 (c), OSHA still believes this clarification is warranted to ensure that downstream users are aware of potential hazardous reactions associated with foreseeable emergencies. OSHA is not convinced 
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that this would be a heavy burden since 
it is not tied to the classification process but a general warning of when a hazardous situation can occur. Therefore, adding the phrase ‘‘for directed use’’ as ACC suggests would not capture the intent of this requirement. This revision is also consistent with the GHS which indicates that the SDS preparer should describe the conditions in which the hazardous reaction could occur (Document ID 0060, p. 400). 
IX. Section 11: Toxicological 
Information 
OSHA proposed to revise Section 11, 
Toxicological information, to align with Rev. 7 (Document ID 0060, p. 395) by adding a new Section 11 (e), Interactive Effects. Because of that proposed change, OSHA also proposed moving the former Section 11 (e) to Section 11 (f). Additionally, OSHA proposed to add a new Section 11 (g) providing that when specific chemical data or information is not available, SDS preparers must indicate if alternative information was used and what method was used to derive the information ( e.g., 
where the preparer is using information from a class of chemicals rather than the exact chemical in question and using structure-activity relationships (SAR) to derive the toxicological information). 
With regard to proposed Section 11 
(e), several commenters requested a definition of ‘‘interactive effects’’ and sought clarification of specific requirements of the proposal. Tom Murphy commented that the proposal did not contain a definition of interactive effects and that a lack of clarity creates a ‘‘potential for systemic failure.’’ Murphy suggested that this issue could be resolved by defining the term interactive effects or striking the requirement (Document ID 0277, p. 2). Similarly, ACC requested clarification of ‘‘interactive effects’’ as they felt it was not clear from the NPRM or GHS what this proposed provision entails (Document ID 0347, p. 26). 
Michele Sullivan asked why OSHA 
proposed to add interactive effects to the SDS, suggesting that the requirement was inadequately explained in both the GHS and NPRM and noting it is not included in UN GHS Table 1.5.2 Minimum information for an SDS. Sullivan suggested that including this information was not ‘‘necessary or related to worker safety’’ and that OSHA should align as closely as possible with the GHS Table 1.5.2 from the UN GHS Purple Book to promote global harmonization (Document ID 0366, p. 9). While ‘‘interactive effects’’ are not 
listed in Table 1.5.2, the term is 
mentioned in Appendix 4 Guidance on the preparation of the safety data sheet (SDS) paragraph 4.3.11.11 (Document ID 0060, p. 401). ‘‘Interactive effects’’ such as synergistic or antagonistic effects occur when some or all individual components (ingredients) of a mixture influence the toxicity of individual ingredients and the combined effects deviate from additive predictions (see related considerations in Appendix A.0.4—Considerations for the classification of mixtures). When an SDS preparer has information that the combination of chemicals in a mixture have a different level and/or type of toxicity than would be predicted by adding the toxicity of its components, the preparer should state that on the SDS and describe the nature of the interactive effects. OSHA recognizes that testing and studies are often required to produce information on interactive effects. Since neither the GHS nor OSHA require testing, this information need only be disclosed if the toxicological data is available without testing. OSHA disagrees with Michele Sullivan’s comment that this requirement would not benefit worker safety; OSHA proposed adding this provision because it understood this to be a gap in the information provided in the SDS that could be important for understanding the hazards present in a workplace. 
With regard to proposed Section 11 
(g), ACC supported the inclusion of QSAR (quantitative SAR) and read across, which it characterized as ‘‘powerful and valuable tools for evaluating toxicological information.’’ However, ACC requested clarity regarding what OSHA intended with the 
phrase ‘‘if alternative information is 
used’’ in proposed Section 11(g). (Document ID 0347, p. 26). 
In the NPRM, OSHA noted several 
tools that would qualify as ‘‘using alternative information’’ under proposed Section 11 (g), including SAR, QSAR, and read across, which are used in the absence of specific data on a particular chemical to predict activities, properties, and endpoint information of untested chemicals based on their structural similarity to tested chemicals (86 FR 9723). When SDS preparers lack known chemical specific data, OSHA intends for this provision to require preparers to note that they have used other methods such as SAR, QSAR, and read across to provide toxicological information in Section 11, and then to describe the method they used for 
translating the non-specific data into toxicological information relevant to the untested chemical in question. Making such information accessible in the SDS to health and safety professionals could be useful to determine what kind of controls and PPE may be needed to protect workers who handle these chemicals. 
NACD commented that the proposed 
Section 11 (g) ‘‘essentially asks [SDS] preparers to provide information about their data sources.’’ NACD recommended that OSHA clarify when this is required and what specific information the agency is seeking. They also suggested that OSHA should update its chemical registries and chemical substance guidebook online (Document ID 0329, p. 9). OSHA notes that, while it is not clear which specific materials NACD is asking OSHA to update, the agency will be updating its HCS guidance to provide additional information and support for compliance with the final rule and anticipates including these topics. 
Proposed Section 11 (g) requires that 
SDS preparers note if the toxicity information for a chemical on the SDS is derived from studies which used data that is not specific to the chemical in question and which method was used to make that determination (for instance, QSAR or read-across methods). As NIOSH stated at the hearing, ‘‘structure- activity relationships, analogs of chemicals, and chemical families are all useful characteristics for understanding the toxicity of a chemical, particularly when there is little toxicity information about the particular chemical of interest’’ (Document ID 0423, Tr. 42– 43). NIOSH noted that it would be particularly useful to include such information on the SDS ‘‘for those chemicals for which the chemical families or the SAR have been well studied and well supported in the scientific literature’’ (Document ID 0423, Tr. 42–43). NIOSH also cautioned that ‘‘when the analogs, the SAR, and the chemical families are not well- defined or there is conflicting information about the critical characteristics of the analog chemicals for comparison’’ it can be difficult to interpret that information. Further, because no standard set of information on which to characterize SAR, analog, or chemical families currently exists, it may be difficult to provide guidelines to employers on what information to include (Document ID 0423, Tr. 42–43). OSHA agrees with this analysis of the state of the science regarding these methodologies. Ultimately, the SDS preparer must include the information in the toxicological information section unless they determine that it is of such 
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a quality as would not materially aid 
hazard communication. 
Michele Sullivan also noted that 
Section 11 (g) does not appear in GHS Table 1.5.2 and therefore is not harmonized with the GHS, so SDS preparers should be allowed to use alternative methods ( i.e., SAR, QSAR, 
read-across) to derive toxicity information but they should not be required to specify that alternative methods were used on the SDS because it would not be helpful or necessary for workers’ safety (Document ID 0366, p. 9). 
While OSHA supports the use of 
alternative methods to derive toxicity information, the agency notes that most of these methods would not be used as 
stand-alone (without the addition of in vivo or in vitro data) to classify hazardous substances. The requirement to provide information on the use of alternative methods in the classification allows the reader to evaluate the basis for the classification. Further, OSHA disagrees with the assertation that the proposed requirement does not align with GHS simply because the requirement is not listed on Table 1.5.2. Table 1.5.2 in the GHS is meant to list minimum information for an SDS (Document ID 0060, pp. 38–39). The GHS provides more detail about SDS requirements in the paragraph A4.3.11.12 of Annex 4 which specifies that when genetic data are used, or where data are not available, that information should be noted in the SDS (Document ID 0060, p. 396). 
For the reasons discussed above, 
OSHA is finalizing all of the changes to Section 11 of the SDS as proposed, including new Section 11 (e), the shifting of the prior Section 11 (e) to Section 11 (f), and the new Section 11 (g). 
X. Section 14: Transport Information 
(Nonmandatory) 
OSHA proposed to change non- 
mandatory Section 14 (f), Transport 
information, to read ‘‘Transport in bulk 
according to IMO instruments’’ instead of ‘‘Transport in bulk (according to Annex II of MARPOL 73/78 and the IBC Code)’’ to be consistent with the text in Rev. 7, which better aligns with the IMO (Document ID 0060, p. 39; 0141). OSHA received no comments objecting to the revision in Section 14. Therefore, OSHA is finalizing Section 14 as proposed. 
G. Out of Scope Comments 
As explained in the introduction to 
the Summary and Explanation, OSHA 
addresses all relevant comments submitted as part of a rulemaking. The agency received some comments that were submitted as part of the 
rulemaking process but are outside the scope of the rulemaking. This section addresses any such comments that are not addressed in other sections of the Summary and Explanation. 
DOD commented that OSHA should 
expand the types of hazards reported on SDSs and labels by aligning with the EU REACH regulation (Document ID 0299, p. 5). OSHA did not propose the adoption of any provision within REACH and cannot expand the types of hazards covered by the HCS without 
notice and comment on the issue, so the 
agency declines to adopt DOD’s proposed changes. 
OSHA received an anonymous 
comment regarding the classification of plastic articles which requested that ‘‘the correct approach for the classification of polymer compounds and concentrates . . . be specified in the proposed rule’’ (Document ID 0269). Since articles are exempt from the HCS and OSHA did not propose any changes to the standard that are relevant to the commenter’s concerns, this comment is out of scope for this rulemaking and the agency declines to take the action requested in this comment. 
An anonymous commenter suggested 
that OSHA should revise the training requirements for SDSs to reduce the amount of training but make it more useful for workers (Document ID 0300). OSHA did not propose any changes to the training provisions of the HCS, therefore the suggestion is out of scope for this rulemaking and the agency declines to adopt the commenter’s proposed changes. 
OSHA received another anonymous 
comment asking OSHA to extend the HCS to workers who are not currently 
covered by the standard, including State 
employees not covered by OSHA’s 
regulations (Document ID 0306). The 
comment suggested a number of options 
for extending the population of workers covered by the HCS that are not within OSHA’s power to implement. The agency appreciates the dilemma faced by the commenter and those not protected by the HCS, but States are specifically exempted from being an employer under the OSH Act (29 U.S.C. 652(5)). OSHA therefore cannot take any action in response to this comment. 
Loren Lowry, a private citizen, 
commented that SDS preparers and hazard classifiers do not apply the HCS or GHS the same way when developing hazard classifications for the same chemicals (Document ID 0333). OSHA recognizes this issue and has developed guidance to help stakeholders correctly apply the HCS hazard classification criteria to their chemical or substance. In addition, Lowry noted that countries 
are able to adopt parts or all of the GHS which leads to disharmonization (Document ID 0333, p. 1). While OSHA recognizes the issue as well, it is not within the agency’s power to address uneven or incomplete adoption of the GHS amongst foreign nations. 
WHSP submitted comments related to 
nanotechnology and international developments (Document ID 0341). While the agency appreciates the submission, these comments are outside the scope of this rulemaking. 
Cal/OSHA commented that the 
decision-making procedures for classifying and labelling chemicals are absent from this proposal (Document ID 0322, Att. 1, p. 2). OSHA notes that this issue was discussed during the 2012 HCS update (77 FR 17719, 17795, 17799) and OSHA did not propose any changes related to this issue in this rulemaking. Therefore, Cal/OSHA’s comments on this matter are outside the scope of this rulemaking and OSHA declines to make any changes to the rule 
in response. 
XV. Issues and Options Considered 
In the NPRM, OSHA solicited public 
feedback on specific issues associated 
with the proposed revisions to the HCS in the Issues and Options section, including timeframes for updates, issues related to proposed regulatory text and appendices (e.g., questions on (f)(12) 
small container labeling requirements), economic analyses, and potential guidance documents. The Issues and Options section also presented optional potential changes to the regulatory text and appendices associated with Rev. 8 of the GHS (e.g., inclusion of non- 
animal test methods in Appendix A.3.1—skin irritation and corrosion). For discussion of issues and options related to economic analyses, regulatory text, and appendices, please refer to those specific discussions in Section VI, Final Economic Analysis and Regulatory Flexibility Analysis, or Section XIV, Summary and Explanation of the Final Rule, for that specific provision. The remainder of this discussion addresses comments submitted on the timeframe for updates to the HCS and on electronic labeling. 
A. Timeframe for Updates to the HCS 
Since aligning the HCS with Rev. 3 in 
2012, OSHA has intended for the HCS 
to stay current with more recent revisions of the GHS. The GHS is updated biennially through published revisions; most recently, Rev. 9 was published in July 2021 (available at https://unece.org/transport/standards/ transport/dangerous-goods/ghs-rev9- 
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2021). Regulatory authorities around the 
world have implemented the GHS at stages ranging from Rev. 1 through Rev. 7. Few regulatory authorities have put programs in place to update their regulations on a routine schedule. The EU has made the most regular updates, and in March 2019, the European Commission (EC) published the adaptation of technical progress (ATP) to EC regulation 1272/2008 (the CLP regulation) to align with both the sixth and seventh revised editions of the GHS (Document ID 0176). These changes to the CLP regulation became effective October 2020. Other regulatory authorities, such as those in Canada, Australia, and New Zealand, have updated their regulations to align with the GHS and have either finalized or are in the process of aligning with Rev. 7; however, none of these countries have a mandate on how often they should do so (Document ID 0172; 0168; 0187). Similarly, to date, OSHA has not adopted a specific timeframe for regularly updating the HCS to implement GHS updates. 
OSHA requested public comment on 
whether the agency should adopt a schedule for updates to the HCS standard (e.g., every four years or every 
two revisions of the GHS) or wait until there are significant changes to the GHS before initiating rulemaking. The agency received several comments on the question but received no consensus on a specific timeframe for updating the 
HCS. 
Hugo Hidalgo commented that ‘‘the 
revision and updates to the HCS must be close together with the GHS latest versions to ensure alignment with the rest of the world, requiring a strong relationship with US major trading partners’’ (Document ID 0297, p. 4). 
CGA and GAWDA commented that 
OSHA should review the HCS every two revisions of the GHS to determine if the changes are substantive enough to reach ‘‘a threshold that would necessitate’’ implementing a change, which they noted ‘‘would help to ensure that the time, cost, and effort required to meet new requirements would result in enhanced employee safety’’ (Document ID 0310, p. 3). Similarly, SAAMI suggested that OSHA realign with the GHS every four years or two revisions (Document ID 0370, pp. 2–3). Hach recommended updates to the HCS every 8 years, or every fourth revision, while Michele Sullivan indicated that every 5 or 6 years may be more appropriate (Document ID 0323, p. 11; 0366, p. 10). Others indicated it would be more appropriate to coordinate updates either with trading partners or the DOT (Document ID 0279, p. 3; 0347, p. 27; 
0364, pp. 2–3). 
The Flavor Extract Manufacturers 
Association, Hawkins, and FCA suggested that OSHA should maintain a regular schedule for updates to provide more regulatory certainty to companies, but did not provide a suggested schedule (Document ID 0346, p. 3; 0423, Tr. 193; 0349, p. 6). IHSC noted ‘‘it is important to periodically revise the standard to stay aligned with the 
international standards to take 
advantage of the hard work done by our representatives to the UN subcommittee and the various working agencies’’ (Document ID 0349, p. 1). 
Cal/HESIS recommended that OSHA 
update the HCS ‘‘only when there are significant changes to the GHS that would justify opening rulemaking’’ and that OSHA should have flexibility in determining the need as a fixed schedule ‘‘may not be in the interest of all involved given the resources and effort required’’ (Document ID 0313, p. 3). Some other stakeholders’ comments similarly suggested that OSHA should update the HCS when significant or substantial changes to the GHS have occurred, or when these changes will 
lead to improved worker protections (Document ID 0309, p. 11; 0327, p. 3; 0329, p. 2; 0344, p. 3; 0368, p. 11). 
NIOSH also recommended that OSHA 
update the HCS only when significant changes to the GHS warrant rulemaking, noting that ‘‘[a]dhering to a regular schedule to update the OSHA HCS might not be prudent given the resources and effort required— especially if there were minor adjustments to the GHS that would not require major revisions to the HCS’’ (Document ID 0456, Att. 2, p. 2). Dow also supported updating the HCS when there are substantial updates in order to maintain harmonization with trading partners, but noted that ‘‘an update should be justified by advancement in science or technology resulting in clear 
benefits to worker safety’’ (Document ID 
0359, p. 1). NAIMA supported less 
frequent HCS updates to incorporate 
significant changes to the GHS because there are significant compliance costs associated with HCS updates (Document ID 0461, pp. 8–9). 
After careful consideration, the 
agency agrees with commenters who argued it is more prudent to only update the HCS when significant changes have occurred to the GHS that require realignment to improve worker safety. 
B. Electronic Labeling 
In the NPRM, OSHA requested 
comments on using electronic 
technology, such as quick response (QR) codes and radio-frequency identification 
(RFID) for labeling chemical packaging. OSHA was interested in gathering information from stakeholders on what technological, economic, and security challenges employers would face if electronic labeling was permitted in a future HCS revision. The agency also requested comments on the types of electronic chemical labeling already in existence or under development, information on the types of electronic coding systems utilized and the costs incurred, and benefits achieved from the programs if implemented. In addition, OSHA asked what backup measures are in place to ensure immediate access to the hazard information. OSHA was interested in gathering information about workers’ experiences with electronic labels, and foreseeable challenges that OSHA should consider (e.g., worker accessibility to electronic 
label information) (86 FR 9690). 
Many commenters supported 
exploring the use of electronic labels in the future (Document ID 0309, p. 13; 0327, p. 6; 0347, pp. 20–21; 0297, p. 3). Commenters stated that using technology (e.g., QR codes and RFID) for 
labels and SDSs will provide a quick (Document ID 0261), easy (Document ID 0368, p. 8), universal (Document ID 0271), and efficient (Document ID 0281, Att. 2, p. 7) way to access hazard information about the chemicals at workplaces. Givaudan indicated strong support and urged OSHA to implement the use of electronic labels (Document ID 0293, p. 1). Hugo Hidalgo indicated that given the worldwide use of this technology, hard copies should not be the only way to comply with the HCS (Document ID 0297, p. 4). 
Some commenters suggested that 
OSHA should make electronic labeling optional, but raised concerns about the possibility of broad implementation (Document ID 0316, p. 7; 0329, p. 9). Specifically, API indicated that this provision should be optional and further stakeholder engagement would be beneficial as there may be concerns related to wide use of electronic labels, including limited use of mobile phones in many workplaces, additional costs for implementation, and no demonstrated need for (and perhaps limited benefit of) electronic labels (Document ID 0316, pp. 7–8). They indicated that using digital hazard information during the transport phase could be useful, but implementing such provisions could require extensive revisions to the GHS (Document ID 0316, p. 8). Relatedly, IMA–NA commented that this would be costly and not work as a blanket 
approach across industries (Document ID 0363, pp. 8–9). 
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Additionally, NIOSH supported 
OSHA’s consideration of utilizing newer 
technology options, such as QR codes, RFID, or website addresses, to link to pertinent labeling information and SDSs. However, they also commented that electronic labeling should not be a substitute for maintaining label information and SDSs in the workplace in a physical form because in emergencies there must be a backup means of accessing the label and SDS in case the container becomes compromised or inaccessible (Document ID 0281, Att. 2, p. 7). 
Similarly, NABTU commented that 
electronic technology for labeling could improve the ability of manufacturers and importers to provide chemical hazard information, including access to emergency medical and first aid information, which they noted remains a challenge on construction sites. However, they stated that it should not be substituted for the hazard information and pictograms already required on labels. They provided examples of QR codes that are already being used in the construction industry to train workers on using hazardous equipment, working at heights, and accessing SDSs for masonry and concrete products. NABTU pointed out that the HCS already permits employers to provide electronic access to SDSs, therefore ‘‘amending the HCS to permit use of QR codes on labels for SDSs would not materially alter the standard’s requirement for SDSs but would encourage use of the technology’’ (Document ID 0334, p. 5). 
HCPA supported OSHA’s exploration 
of the HCS permitting electronic labeling in some situations. They stated that the product identifier, pictograms, and hazard statements should remain on labels affixed to the product, but employers should be able to convey other aspects digitally. In their view, this would allow employees to access the most important information in the event of an emergency, but they could still have ready access to the rest of the information. They specifically noted that it would facilitate employee access to SDSs in the case of an electrical failure. Additionally, HCPA stated that manufacturers and importers should still have labels online with complete information that can be downloaded, printed, and applied to containers when the employer cannot access information digitally (Document ID 0327, p. 6). Similarly, ADM supported the use of electronic labeling to provide enhanced safety information and reduce label sizes, but suggested that essential 
information should still be required on printed labels, including signal words and hazard statements, in the event of a power failure or for businesses not fully equipped with the latest technologies (Document ID 0361, p. 3). 
NACD stated that use of electronic 
labels and SDSs could benefit small packages and emergency responders, but requiring the use of electronic devices might present challenges because, among other things, some employers do not allow workers to use cell phones, there would need to be a 
standard format across operating 
systems, and network accessibility is not universal (Document ID 0329, p. 9). 
ACC supported the use of electronic 
labeling for chemical packaging and particularly supported the distribution of SDSs via electronic means. However, ACC noted a number of issues would need to be clarified in order to determine whether it would be realistic to incorporate electronic labeling in the HCS, including what would be considered an electronic label, whether it would only add to the label or replace elements of the label, and whether it would apply to the label or the SDS. ACC also raised concerns about using electronic devices in restricted areas due to potential fire hazards. Additionally, ACC requested clarification on how these changes would be coordinated with maintaining the pertinent data online for products. ACC suggested that OSHA provide clarification on the timing of OSHA’s adoption of electronic labeling and create a working group rather than attempting to address the issue in this rulemaking (Document ID 0347, pp. 20– 21). 
Similarly, Dow raised concerns 
regarding the potential fire and explosion hazards that would occur if 
unrated electronic devices such as cell 
phones were used in ‘‘electrically 
classified areas’’ to read electronic 
labels. Dow also stated that codes would 
have to link to a website to access the 
label information, which can be challenging for companies to maintain and update for extended periods at the same web address. Further, workers might be unable to access important safety information on the label if a company fails to maintain its website due to the company restructuring or shutting down. For these reasons, Dow suggested that electronic labeling should only be voluntary (Document ID 0359, pp. 6–7). 
OSHA appreciates commenters 
providing information on electronic labeling. OSHA is not proposing any new changes in this rulemaking on this issue, but the agency will consider these comments and concerns in future discussions at the UN and in future HCS revisions. 
List of Subjects in 29 CFR Part 1910 
Chemicals, Diseases, Explosives, 
Flammable materials, Gases, Hazardous 
substances, Incorporation by reference, Labeling, Occupational safety and health, Safety, Signs and symbols. 
Authority and Signature 
This document was prepared under 
the direction of Douglas L. Parker, 
Assistant Secretary of Labor for Occupational Safety and Health, U.S. Department of Labor, 200 Constitution Avenue NW, Washington, DC 20210. It is issued under the authority of sections 4, 6, and 8 of the Occupational Safety and Health Act of 1970 (29 U.S.C. 653, 655, 657); 5 U.S.C. 553; section 304, Clean Air Act Amendments of 1990 (Pub. L. 101–549, reprinted at 29 U.S.C.A. 655 Note); section 41, Longshore and Harbor Workers’ Compensation Act (33 U.S.C. 941); section 107, Contract Work Hours and Safety Standards Act (40 U.S.C. 3704); section 1031, Housing and Community Development Act of 1992 (42 U.S.C. 4853); section 126, Superfund Amendments and Reauthorization Act of 1986, as amended (reprinted at 29 U.S.C.A. 655 Note); Secretary of Labor’s Order No. 8–2020 (85 FR 58393–94); and 29 CFR part 1911. 
Signed at Washington, DC. 
Douglas L. Parker, 
Assistant Secretary of Labor for Occupational 
Safety and Health. 
For the reasons set forth in the 
preamble, Chapter XVII of Title 29, part 
1910 of the Code of Federal Regulations is amended as follows: 
PART 1910—OCCUPATIONAL SAFETY 
AND HEALTH STANDARDS 
■1. The authority citation for part 1910 
continues to read as follows: 
Authority: 33 U.S.C. 941; 29 U.S.C. 653, 
655, 657; Secretary of Labor’s Order No. 12– 
71 (36 FR 8754); 8–76 (41 FR 25059), 9–83 (48 FR 35736), 1–90 (55 FR 9033), 6–96 (62 FR 111), 3–2000 (65 FR 50017), 5–2002 (67 
FR 65008), 5–2007 (72 FR 31160), 4–2010 (75 FR 55355), 1–2012 (77 FR 3912), or 08–2020 (85 FR 58393); 29 CFR part 1911; and 5 U.S.C. 553, as applicable. 
■2. Amend § 1910.6 as follows: 
■a. Revise paragraph (a), the 
introductory text of paragraph (e), and 
the introductory text of paragraph (h); 
■b. Redesignate paragraphs (h)(27) and 
(28) as (h)(28) and (29) and add new paragraph (h)(27); 
■c. Redesignate paragraphs n through 
(bb) as shown in the following redesignation table: 
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Old paragraph New paragraph 
n ................................ p. 
o ................................ s. 
p through x ................ t through bb. 
y ................................ o. 
z ................................ cc. 
aa .............................. r. 
bb .............................. dd. 
■d. Add new paragraphs (n) and (q); 
and 
■e. Revise newly redesignated 
paragraphs (v) and (dd). 
The revisions and additions read as 
follows: 
§ 1910.6 Incorporation by Reference. 
(a)(1) Certain material is incorporated 
by reference into this part with the 
approval of the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. To enforce any edition other than that specified in this section, the Occupational Safety and Health Administration (OSHA) must publish a document in the Federal 
Register and the material must be 
available to the public. 
(i) The standards of agencies of the 
U.S. Government, and organizations which are not agencies of the U.S. Government which are incorporated by reference in this part, have the same force and effect as other standards in this part. Only the mandatory provisions (i.e., provisions containing 
the word ‘‘shall’’ or other mandatory language) of standards incorporated by reference are adopted as standards under the Occupational Safety and Health Act. 
(ii) Any changes in the standards 
incorporated by reference in this part and an official historic file of such changes are available for inspection in the Docket Office at the national office of OSHA, U.S. Department of Labor, Washington, DC 20210; telephone: 202– 693–2350 (TTY number: 877–889– 5627). 
(2) All approved incorporation by 
reference (IBR) material is available for inspection at OSHA and at the National Archives and Records Administration (NARA). 
(i) Contact OSHA at any Regional 
Office of the Occupational Safety and Health Administration (OSHA), or at the OSHA Docket Office, U.S. Department of Labor, 200 Constitution Avenue NW, Room N–3508, Washington, DC 20210; telephone: 202–693–2350 (TTY number: 877–889–5627). 
(ii) For information on the availability 
of these standards at NARA, visit www.archives.gov/federal-register/cfr/ ibr-locations or email fr.inspection@
nara.gov. (3) The IBR material may be obtained 
from the sources in the following paragraphs of this section or from one or more private resellers listed in this paragraph (a)(3). For material that is no longer commercially available, contact OSHA (see paragraph (a)(2)(i) of this section). 
(i) Accuris Standards Store, 321 
Inverness Drive, South Englewood, CO 80112; phone: (800) 332–6077; website: https://store.accuristech.com . 
(ii) American National Standards 
Institute (see paragraph (e) for contact information). 
(iii) GlobalSpec, 257 Fuller Road, 
Suite NFE 1100, Albany, NY 12203– 3621; phone: (800) 261–2052; website: https://standards.globalspec.com . 
(iv) Nimonik Document Center, 401 
Roland Way, Suite 224, Oakland, CA 94624; phone (650)591–7600; email: info@document-center.com; website: www.document-center.com. 
(v) Techstreet, phone: (855) 999–9870; 
email: store@techstreet.com; website: 
www.techstreet.com. 
* * * * * 
(e) American National Standards 
Institute (ANSI), 25 West 43rd Street, 
Fourth Floor, New York, NY 10036– 7417; phone: (212) 642–4980; email: info@ansi.org; website: www.ansi.org. 
* * * * * 
(h) ASTM International, 100 Barr 
Harbor Drive, P.O. Box C700, West 
Conshohocken, PA 19428–2959; phone: (610) 832–9585; email: sevice@astm.org ; 
website: www.astm.org. (27) ASTM 
D4359–90, Standard Test Method for Determining Whether a Material is a Liquid or a Solid, approved July 1, 2019; IBR approved for § 1910.1200. 
* * * * * 
(27) ASTM D 4359–90, Standard Test 
Method for Determining Whether a 
Material is a Liquid or a Solid, Approved 2019, IBR approved for § 1910.1200. 
* * * * * 
(n) German Institute for 
Standardization (DIN) (Beuth Verlag 
GmbH) Am DIN-Platz Burggrafenstra+e 6 10787 Berlin, Germany; phone: +49 30 58885 70070; website: https://din.de/en/ 
about-standards/buy-standard. 
(1) DIN 51794:2003–05—Determining 
the ignition temperature of petroleum products, May 2003, IBR approved for appendix B to § 1910.1200. 
(2) [Reserved] 
* * * * * 
(q) International Electrotechnical 
Commission (IEC), IEC Secretariat, 3 rue de Varembe ´, PO Box 131, CH–1211 
Geneva 20, Switzerland; phone: +41 22 919 02 11; email: sales@iec.ch; website: 
https://www.iec.ch. (1) IEC 60079–20–1, Explosive 
atmospheres—Part 20–1: Material characteristics for gas and vapor classification—Test methods and data, Edition 1.0, 2010–01; IBR approved for appendix B to § 1910.1200. 
(2) [Reserved] 
* * * * * 
(v) International Organization for 
Standardization (ISO), ISO Central Secretariat, Chemin de Blandonnet 8 CP 401—1214 Vernier, Geneva, Switzerland; phone: +41 22 749 01 11; email: central@iso.org; website: 
www.iso.org/store.html. 
(1) ISO 817:2014(E), Refrigerants— 
Designation and safety classification, Third edition, 2014–04–15; IBR approved for appendix B to § 1910.1200. 
(2) ISO 10156:1996 (E), Gases and Gas 
Mixtures—Determination of Fire 
Potential and Oxidizing Ability for the 
Selection of Cylinder Valve Outlets, 
Second Edition, Feb. 15, 1996; IBR 
approved for appendix B to § 1910.1200. 
(3) ISO 10156:2017(E), Gas 
Cylinders—Gases and gas mixtures— Determination of fire potential and oxidizing ability for the selection of cylinder valve outlets, Fourth edition, 2017–07; IBR approved for appendix B to §
1910.1200. 
(4) ISO 10156–2:2005 (E), Gas 
cylinders—Gases and Gas Mixtures— Part 2: Determination of Oxidizing Ability of Toxic and Corrosive Gases and Gas Mixtures, First Edition, Aug. 1, 2005; IBR approved for appendix B to subpart Z. 
(5) ISO 13943:2000 (E/F); Fire 
Safety—Vocabulary, First Edition, April, 15, 2000, IBR approved for appendix B to §1910.1200. 
* * * * * 
(dd) United Nations (UN), United 
Nations Publications, P.O. Box 960 Herndon, VA 20172; phone: (703) 661– 1571;; email: order@un.org; website: 
https://shop.un.org/. 
(1) ADR 2019, European Agreement 
Concerning the International Carriage of Dangerous Goods by Road; Annex A: General provisions and provisions concerning dangerous substances and articles; (Volumes I and II) including December 2018 corrigendum to Volume II, applicable January 1, 2019; IBR approved for § 1910.1200. 
(2) ST/SG/AC.10/Rev.4 (‘‘UN ST/SG/ 
AC.10/Rev.4’’), The UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, Fourth Revised Edition, 2003; IBR approved for appendix B to § 1910.1200. 
(3) ST/SG/AC.10/11/Rev.6 (‘‘UN ST/ 
SG/AC.10/11/Rev.6’’), Recommendations on the Transport of 
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Dangerous Goods: Manual of Tests and 
Criteria, sixth revised edition, copyright 2015; IBR approved for appendix B to § 1910.1200. 
■3. Amend § 1910.1200 as follows: 
■a. Revise paragraphs (a)(1) and 
(b)(6)(x); 
■b. Revise and republish paragraph (c); 
■c. Revise paragraphs (d)(1), (e)(4), 
(f)(1), (5), and (11); 
■d. Add paragraph (f)(12); and 
■e. Revise paragraphs (g)(1) and (2), (7) 
and (10), (i)(1) through (3), (j), and appendices A through D. 
The revisions and additions read as 
follows: 
§ 1910.1200 Hazard Communication 
Standard. 
(a) * * * 
(1) The purpose of this section is to 
ensure that the hazards of all chemicals 
produced or imported are classified, and that information concerning the classified hazards is transmitted to employers and employees. The requirements of this section are intended to be consistent with the provisions of the United Nations Globally Harmonized System of Classification and Labeling of Chemicals (GHS), primarily Revision 7. The transmittal of information is to be accomplished by means of comprehensive hazard communication programs, which are to include container labeling and other forms of warning, safety data sheets and employee training. 
* * * * * 
(b) * * * 
(6) * * * (x) Nuisance particulates where the 
chemical manufacturer or importer can establish that they do not pose any physical hazard, health hazard, or other hazards covered under this section; 
* * * * * 
(c) Article means a manufactured item 
other than a fluid or particle: 
(i) Which is formed to a specific shape 
or design during manufacture; 
(ii) Which has end use function(s) 
dependent in whole or in part upon its 
shape or design during end use; and 
(iii) Which under normal conditions 
of use does not release more than very small quantities, e.g., minute or trace 
amounts of a hazardous chemical (as determined under paragraph (d) of this section), and does not pose a physical hazard or health risk to employees. 
Assistant Secretary means the 
Assistant Secretary of Labor for Occupational Safety and Health, U.S. Department of Labor, or designee. 
Bulk shipment means any hazardous 
chemical transported where the mode of transportation comprises the immediate container (i.e. contained in tanker truck, 
rail car, or intermodal container). 
Chemical means any substance, or 
mixture of substances. 
Chemical manufacturer means an 
employer with a workplace where chemical(s) are produced for use or distribution. 
Chemical name means the scientific 
designation of a chemical in accordance with the nomenclature system developed by the International Union of Pure and Applied Chemistry (IUPAC) or the Chemical Abstracts Service (CAS) rules of nomenclature, or a name that will clearly identify the chemical for the purpose of conducting a hazard classification. 
Classification means to identify the 
relevant data regarding the hazards of a chemical; review those data to ascertain the hazards associated with the chemical; and decide whether the chemical will be classified as hazardous according to the definition of hazardous chemical in this section. In addition, classification for health and physical hazards includes the determination of the degree of hazard, where appropriate, by comparing the data with the criteria for health and physical hazards. 
Combustible dust means finely 
divided solid particulates of a substance or mixture that pose a flash-fire hazard or explosion hazard when dispersed in air or other oxidizing media. 
Commercial account means an 
arrangement whereby a retail distributor sells hazardous chemicals to an employer, generally in large quantities over time and/or at costs that are below the regular retail price. 
Common name means any 
designation or identification such as code name, code number, trade name, brand name or generic name used to identify a chemical other than by its chemical name. 
Container means any bag, barrel, 
bottle, box, can, cylinder, drum, reaction vessel, storage tank, or the like that contains a hazardous chemical. For purposes of this section, pipes or piping systems, and engines, fuel tanks, or other operating systems in a vehicle, are not considered to be containers. 
Designated representative means any 
individual or organization to whom an employee gives written authorization to exercise such employee’s rights under this section. A recognized or certified collective bargaining agent shall be treated automatically as a designated representative without regard to written employee authorization. 
Director means the Director, National 
Institute for Occupational Safety and Health, U.S. Department of Health and Human Services, or designee. 
Distributor means a business, other 
than a chemical manufacturer or importer, which supplies hazardous chemicals to other distributors or to employers. 
Employee means a worker who may 
be exposed to hazardous chemicals under normal operating conditions or in foreseeable emergencies. Workers such as office workers or bank tellers who encounter hazardous chemicals only in non-routine, isolated instances are not covered. 
Employer means a person engaged in 
a business where chemicals are either used, distributed, or are produced for use or distribution, including a contractor or subcontractor. 
Exposure or exposed means that an 
employee is subjected in the course of employment to a hazardous chemical, and includes potential (e.g., accidental 
or possible) exposure. ‘‘Subjected’’ in terms of health hazards includes any route of entry (e.g., inhalation, 
ingestion, skin contact or absorption.) 
Foreseeable emergency means any 
potential occurrence such as, but not limited to, equipment failure, rupture of containers, or failure of control equipment which could result in an uncontrolled release of a hazardous chemical into the workplace. 
Gas means a substance which 
(i) At 122 °F (50 °C) has a vapor 
pressure greater than 43.51 PSI (300 kPa) (absolute); or 
(ii) Is completely gaseous at 68 °F (20 
°C) at a standard pressure of 14.69 PSI (101.3 kPa). 
Hazard category means the division of 
criteria within each hazard class, e.g., 
oral acute toxicity and flammable liquids include four hazard categories. These categories compare hazard severity within a hazard class and should not be taken as a comparison of hazard categories more generally. 
Hazardous chemical means any 
chemical which is classified as a physical hazard or a health hazard, a simple asphyxiant, combustible dust, or hazard not otherwise classified. 
Hazard class means the nature of the 
physical or health hazards, e.g., 
flammable solid, carcinogen, oral acute toxicity. 
Hazard not otherwise classified 
(HNOC) means an adverse physical or 
health effect identified through evaluation of scientific evidence during the classification process that does not meet the specified criteria for the physical and health hazard classes addressed in this section. This does not extend coverage to adverse physical and health effects for which there is a hazard 
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class addressed in this section, but the 
effect either falls below the cut-off value/concentration limit of the hazard class or is under a GHS hazard category that has not been adopted by OSHA (e.g., acute toxicity Category 5). 
Hazard statement means a statement 
assigned to a hazard class and category that describes the nature of the hazard(s) of a chemical, including, where appropriate, the degree of hazard. 
Health hazard means a chemical 
which is classified as posing one of the following hazardous effects: acute toxicity (any route of exposure); skin corrosion or irritation; serious eye damage or eye irritation; respiratory or skin sensitization; germ cell mutagenicity; carcinogenicity; 
reproductive toxicity; specific target organ toxicity (single or repeated exposure); or aspiration hazard. The criteria for determining whether a chemical is classified as a health hazard are detailed in Appendix A to § 1910.1200—Health Hazard Criteria. 
Immediate outer package means the 
first package enclosing the container of hazardous chemical. 
Immediate use means that the 
hazardous chemical will be under the control of and used only by the person who transfers it from a labeled container and only within the work shift in which it is transferred. 
Importer means the first business with 
employees within the Customs Territory of the United States which receives hazardous chemicals produced in other countries for the purpose of supplying them to distributors or employers within the United States. 
Label means an appropriate group of 
written, printed or graphic information elements concerning a hazardous chemical that is affixed to, printed on, or attached to the immediate container of a hazardous chemical, or to the outside packaging. 
Label elements means the specified 
pictogram, hazard statement, signal word and precautionary statement for each hazard class and category. 
Liquid means a substance or mixture 
which at 122 °F (50 °C) has a vapor 
pressure of not more than 43.51 PSI (300 kPa (3 bar)), which is not completely gaseous at 68 °F (20 °C) and at a 
standard pressure of 101.3 kPa, and which has a melting point or initial melting point of 68 °F (20 °C) or less at 
a standard pressure of 14.69 PSI (101.3 kPa). Either ASTM D4359–90 (R2019) (incorporated by reference, see § 1910.6); or the test for determining fluidity (penetrometer test) prescribed in section 2.3.4 of ADR 2019 (incorporated by reference, see § 1910.6) can establish whether a viscous substance or mixture is a liquid if a specific melting point cannot be determined. 
Mixture means a combination or a 
solution composed of two or more substances in which they do not react. 
Physical hazard means a chemical 
that is classified as posing one of the following hazardous effects: explosive; flammable (gases, liquids, or solids); aerosols; oxidizer (gases, liquids, or 
solids); self-reactive; pyrophoric (liquid 
or solid); self-heating; organic peroxide; corrosive to metal; gas under pressure; in contact with water emits flammable gas; or desensitized explosive. The criteria for determining whether a chemical is classified as a physical hazard are detailed in appendix B to this section. 
Physician or other licensed health 
care professional (PLHCP) means an 
individual whose legally permitted scope of practice (i.e., license, 
registration, or certification) allows the individual to independently provide or be delegated the responsibility to provide some or all of the health care services referenced in paragraph (i) of this section. 
Pictogram means a composition that 
may include a symbol plus other graphic elements, such as a border, background pattern, or color, that is intended to convey specific information about the hazards of a chemical. Eight pictograms are designated under this standard for application to a hazard category. 
Precautionary statement means a 
phrase that describes recommended measures that should be taken to minimize or prevent adverse effects resulting from exposure to a hazardous chemical, or improper storage or handling. 
Produce means to manufacture, 
process, formulate, blend, extract, generate, emit, or repackage. 
Product identifier means the name or 
number used for a hazardous chemical 
on a label or in the SDS. It provides a 
unique means by which the user can 
identify the chemical. The product 
identifier used shall permit cross- 
references to be made among the list of hazardous chemicals required in the written hazard communication program, the label and the SDS. 
Released for shipment means a 
chemical that has been packaged and labeled in the manner in which it will be distributed or sold. 
Responsible party means someone 
who can provide additional information on the hazardous chemical and appropriate emergency procedures, if necessary. Safety data sheet (SDS) means written 
or printed material concerning a hazardous chemical that is prepared in accordance with paragraph (g) of this section. 
Signal word means a word used to 
indicate the relative level of severity of hazard and alert the reader to a potential hazard on the label. The signal words used in this section are ‘‘danger’’ and ‘‘warning.’’ ‘‘Danger’’ is used for the more severe hazards, while ‘‘warning’’ is used for the less severe. 
Simple asphyxiant means a substance 
or mixture that displaces oxygen in the ambient atmosphere, and can thus cause oxygen deprivation in those who are exposed, leading to unconsciousness and death. 
Solid means a substance or mixture 
which does not meet the definitions of liquid or gas. 
Specific chemical identity means the 
chemical name, Chemical Abstracts Service (CAS) Registry Number, or any other information that reveals the precise chemical designation of the substance. 
Substance means chemical elements 
and their compounds in the natural 
state or obtained by any production process, including any additive necessary to preserve the stability of the product and any impurities deriving from the process used, but excluding any solvent which may be separated without affecting the stability of the substance or changing its composition. 
Trade secret means any confidential 
formula, pattern, process, device, information or compilation of information that is used in an employer’s business, and that gives the employer an opportunity to obtain an advantage over competitors who do not know or use it. Appendix E to §
1910.1200—Definition of Trade Secret, 
sets out the criteria to be used in evaluating trade secrets. 
Use means to package, handle, react, 
emit, extract, generate as a byproduct, or transfer. 
Work area means a room or defined 
space in a workplace where hazardous chemicals are produced or used, and where employees are present. 
Workplace means an establishment, 
job site, or project, at one geographical location containing one or more work areas. 
(d)(1)(i) Chemical manufacturers and 
importers shall evaluate chemicals produced in their workplaces or imported by them to classify the chemicals in accordance with this section. For each chemical, the chemical manufacturer or importer shall determine the hazard classes, and where appropriate, the category of each class 
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that apply to the chemical being 
classified. The hazard classification shall include any hazards associated with the chemical’s intrinsic properties including: 
(A) a change in the chemical’s 
physical form and; 
(B) chemical reaction products 
associated with known or reasonably anticipated uses or applications. 
(ii) Employers are not required to 
classify chemicals unless they choose not to rely on the classification performed by the chemical manufacturer or importer for the chemical to satisfy this paragraph (d)(1). 
* * * * * 
(e) * * * 
(4) The employer shall make the 
written hazard communication program 
available, upon request, to employees, their designated representatives, the Assistant Secretary and the Director, in accordance with the requirements of § 1910.1020(e). 
* * * * * 
(f) * * * 
(1) Labels on shipped containers. The 
chemical manufacturer, importer, or 
distributor shall ensure that each container of hazardous chemicals leaving the workplace is labeled, tagged or marked. Hazards not otherwise classified and hazards identified and classified under (d)(1)(ii) do not have to be addressed on the container. Where the chemical manufacturer, importer, or distributor is required to label, tag or mark the following shall be provided: 
(i) Product identifier; 
(ii) Signal word; (iii) Hazard statement(s); 
(iv) Pictogram(s); (v) Precautionary statement(s); (vi) Name, U.S. address, and U.S. 
telephone number of the chemical 
manufacturer, importer, or other responsible party. 
* * * * * 
(5) Transportation. (i) Chemical 
manufacturers, importers, or 
distributors shall ensure that each container of hazardous chemicals leaving the workplace is labeled, tagged, or marked in accordance with this section in a manner which does not conflict with the requirements of the Hazardous Materials Transportation Act (49 U.S.C. 5101 et seq.) and regulations 
issued under that Act by the Department of Transportation (49 CFR subtitle B). 
(ii) The label for bulk shipments of 
hazardous chemicals must be on the immediate container, transmitted with the shipping papers or the bills of lading, or, with the agreement of the receiving entity, transmitted by technological or electronic means so that it is immediately available to workers in printed form on the receiving end of shipment. 
(iii) Where a pictogram required by 
the Department of Transportation under title 49 of the Code of Federal Regulations appears on a shipped container, the pictogram specified in appendix C.4 to this section for the 
same hazard is not required on the label. 
* * * * * 
(11) Label Updates. (i) Chemical 
manufacturers, importers, distributors, 
or employers who become newly aware of any significant information regarding the hazards of a chemical shall revise the labels for the chemical within six months of becoming aware of the new information, and shall ensure that labels on containers of hazardous chemicals shipped after that time contain the new information. For chemicals that have been released for shipment and are awaiting future distribution, chemical manufacturers, importers, distributors, or employers have the option not to relabel those containers; however, if they do not relabel the containers, they must either provide the updated label for each individual container with each shipment or, with the agreement of the receiving entity, transmit the labels by electronic or other technological means. 
(ii) If the chemical is not currently 
produced or imported, the chemical manufacturer, importer, distributor, or employer shall add the information to the label before the chemical is shipped or introduced into the workplace again. 
(12) Small container labelling. (i) This 
paragraph applies where the chemical manufacturer, importer, or distributor can demonstrate that it is not feasible to use pull-out labels, fold-back labels, or tags containing the full label information required by paragraph (f)(1) of this section. 
(ii) For a container less than or equal 
to 100 ml capacity, the chemical manufacturer, importer, or distributor must include, at a minimum, the following information on the label of the container: 
(A) Product identifier; (B) Pictogram(s); (C) Signal word; 
(D) Chemical manufacturer’s name 
and phone number; and 
(E) A statement that the full label 
information for the hazardous chemical is provided on the immediate outer 
package. 
(iii) For a container less than or equal 
to 3 ml capacity, where the chemical manufacturer, importer, or distributor can demonstrate that any label interferes with the normal use of the container, no 
label is required, but the container must bear, at a minimum, the product 
identifier. 
(iv) For all small containers covered 
by paragraph (f)(12)(ii) or (iii) of this section, the immediate outer package must include: 
(A) The full label information 
required by paragraph (f)(1) of this section for each hazardous chemical in the immediate outer package. The label must not be removed or defaced, as required by paragraph (f)(9) of this section. 
(B) A statement that the small 
container(s) inside must be stored in the immediate outer package bearing the complete label when not in use. 
(g) Safety data sheets. (1) Chemical 
manufacturers and importers shall obtain or develop a safety data sheet for each hazardous chemical they produce or import. Employers shall have a safety data sheet in the workplace for each hazardous chemical which they use. 
(2) The chemical manufacturer or 
importer shall ensure that the safety data sheet is in English (although the employer may maintain copies in other languages as well), and includes at least the following section numbers and headings, and associated information under each heading, in the order listed (see appendix D to this section, for the specific content of each section of the safety data sheet): 
(i) Section 1, Identification; 
(ii) Section 2, Hazard(s) identification; (iii) Section 3, Composition/ 
information on ingredients; 
(iv) Section 4, First-aid measures; (v) Section 5, Fire-fighting measures; (vi) Section 6, Accidental release 
measures; 
(vii) Section 7, Handling and storage; (viii) Section 8, Exposure controls/ 
personal protection; 
(ix) Section 9, Physical and chemical 
properties; 
(x) Section 10, Stability and reactivity; (xi) Section 11, Toxicological 
information. 
(xii) Section 12, Ecological 
information; 
(xiii) Section 13, Disposal 
considerations; 
(xiv) Section 14, Transport 
information; 
(xv) Section 15, Regulatory 
information; and 
(xvi) Section 16, Other information, 
including date of preparation or last 
revision. 
Note 1 to paragraph (g)(2): To be 
consistent with the GHS, an SDS must also 
include the headings in paragraphs (g)(2)(xii) through (g)(2)(xv) of this section in order. 
Note 2 to paragraph (g)(2): OSHA will not 
be enforcing information requirements in 
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sections 12 through 15, as these areas are not 
under its jurisdiction. 
* * * * * 
(7)(i) Distributors shall ensure that 
safety data sheets, and updated 
information, are provided to other distributors and employers with their initial shipment and with the first shipment after a safety data sheet is updated; 
(ii) The distributor shall either 
provide safety data sheets with the shipped containers, or send them to the other distributor or employer prior to or at the time of the shipment; 
(iii) Retail distributors selling 
hazardous chemicals to employers having a commercial account shall provide a safety data sheet to such employers upon request, and shall post a sign or otherwise inform them that a safety data sheet is available; 
(iv) Wholesale distributors selling 
hazardous chemicals to employers over- the-counter may also provide safety data sheets upon the request of the employer at the time of the over-the-counter purchase, and shall post a sign or otherwise inform such employers that a safety data sheet is available; 
(v) If an employer without a 
commercial account purchases a hazardous chemical from a retail distributor not required to have safety data sheets on file ( i.e., the retail 
distributor does not have commercial accounts and does not use the materials), the retail distributor shall provide the employer, upon request, with the name, address, and telephone number of the chemical manufacturer, importer, or distributor from which a safety data sheet can be obtained; 
(vi) Wholesale distributors shall also 
provide safety data sheets to employers or other distributors upon request; and, 
(vii) Chemical manufacturers, 
importers, and distributors need not provide safety data sheets to retail distributors that have informed them that the retail distributor does not sell the product to commercial accounts or open the sealed container to use it in their own workplaces. 
* * * * * 
(10) Safety data sheets may be kept in 
any form, including as operating 
procedures, and may be stored in such a way to cover groups of hazardous chemicals in a work area where it may be more appropriate to address the hazards of a process rather than individual hazardous chemicals. However, the employer shall ensure that in all cases the required information is provided for each hazardous chemical, and is readily accessible during each work shift to employees when they are in their work area(s). 
* * * * * 
(i) Trade secrets. (1) The chemical 
manufacturer, importer, or employer 
may withhold the specific chemical identity, including the chemical name, other specific identification of a hazardous chemical, and/or the exact percentage (concentration) or concentration range of the substance in a mixture, from section 3 of the safety data sheet, provided that: 
(i) The claim that the information 
withheld is a trade secret can be supported; 
(ii) Information contained in the 
safety data sheet concerning the properties and effects of the hazardous chemical is disclosed; 
(iii) The safety data sheet indicates 
that the specific chemical identity and/ or concentration or concentration range of composition is being withheld as a trade secret; 
(iv) If the concentration or 
concentration range is being claimed as a trade secret then the safety data sheet provides the ingredient’s concentration as one of the prescribed ranges below in paragraphs (i)(1)(iv)(A) through (M) of this section. 
(A) from 0.1% to 1%; (B) from 0.5% to 1.5%; (C) from 1% to 5%; (D) from 3% to 7%; (E) from 5% to 10%; (F) from 7% to 13%; (G) from 10% to 30%; (H) from 15% to 40%; (I) from 30% to 60%; (J) from 45% to 70%; (K) from 60% to 80%; (L) from 65% to 85%; and (M) from 80% to 100%. (v) The prescribed concentration 
range used must be the narrowest range possible. If the exact concentration range falls between 0.1% and 30% and does not fit entirely into one of the prescribed concentration ranges of paragraphs (i)(1)(iv)(A) to (G) of this section, a single range created by the combination of two applicable consecutive ranges between paragraphs (i)(1)(iv)(A) and (G) of this section may be disclosed instead, provided that the combined concentration range does not include any range that falls entirely outside the exact concentration range in which the ingredient is present. 
(vi) Manufacturers may provide a 
range narrower than those prescribed in (i)(1)(v). 
(vii) The specific chemical identity 
and exact concentration or concentration range is made available to health professionals, employees, and designated representatives in accordance with the applicable provisions of this paragraph (i) of this section. 
(2) Where a treating PLHCP 
determines that a medical emergency exists and the specific chemical identity and/or specific concentration or concentration range of a hazardous chemical is necessary for emergency or first-aid treatment, the chemical 
manufacturer, importer, or employer 
shall immediately disclose the specific chemical identity or percentage composition of a trade secret chemical to that treating PLHCP, regardless of the existence of a written statement of need or a confidentiality agreement. The chemical manufacturer, importer, or employer may require a written statement of need and confidentiality agreement, in accordance with the provisions of paragraphs (i)(3) and (4) of this section, as soon as circumstances permit. 
(3) In non-emergency situations, a 
chemical manufacturer, importer, or employer shall, upon request, disclose a specific chemical identity or exact concentration or concentration range, otherwise permitted to be withheld under paragraph (i)(1) of this section, to a health professional (e.g., PLHCP, 
industrial hygienist, toxicologist, or epidemiologist) providing medical or other occupational health services to exposed employee(s), and to employees or designated representatives, if: 
(i) The request is in writing; 
(ii) The request describes with 
reasonable detail one or more of the 
following occupational health needs for the information: 
(A) To assess the hazards of the 
chemicals to which employees will be exposed; 
(B) To conduct or assess sampling of 
the workplace atmosphere to determine employee exposure levels; 
(C) To conduct pre-assignment or 
periodic medical surveillance of exposed employees; 
(D) To provide medical treatment to 
exposed employees; 
(E) To select or assess appropriate 
personal protective equipment for 
exposed employees; 
(F) To design or assess engineering 
controls or other protective measures for exposed employees; and, 
(G) To conduct studies to determine 
the health effects of exposure. 
(iii) The request explains in detail 
why the disclosure of the specific 
chemical identity or percentage 
composition is essential and that, in lieu 
thereof, the disclosure of the following 
information to the health professional, 
employee, or designated representative, 
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would not satisfy the purposes 
described in paragraph (i)(3)(ii) of this section: 
(A) The properties and effects of the 
chemical; 
(B) Measures for controlling workers’ 
exposure to the chemical; 
(C) Methods of monitoring and 
analyzing worker exposure to the chemical; and, 
(D) Methods of diagnosing and 
treating harmful exposures to the chemical; 
(iv) The request includes a 
description of the procedures to be used to maintain the confidentiality of the disclosed information; and, 
(v) The health professional, and the 
employer or contractor of the services of the health professional ( i.e. downstream 
employer, labor organization, or individual employee), employee, or designated representative, agree in a written confidentiality agreement that the health professional, employee, or designated representative, will not use the trade secret information for any purpose other than the health need(s) asserted and agree not to release the information under any circumstances other than to OSHA, as provided in paragraph (i)(6) of this section, except as authorized by the terms of the agreement or by the chemical manufacturer, importer, or employer. 
* * * * * 
(j) Dates—(1) Effective date. This 
section shall become effective July 19, 
2024. 
(2) Substances. (i) Manufacturers, 
importers, and distributors, evaluating substances shall be in compliance with all modified provisions of this section no later than January 19, 2026. 
(ii) For substances, all employers 
shall, as necessary, update any alternative workplace labeling used under paragraph (f)(6) of this section, update the hazard communication program required by paragraph (h)(1) of this section, and provide any additional employee training in accordance with paragraph (h)(3) of this section for newly identified physical hazard, or health hazards or other hazards covered under this section no later than July 20, 2026. 
(3) Mixtures. (i) Chemical 
manufacturers, importers, and distributors evaluating mixtures shall be in compliance with all modified provisions of this section no later than July 19, 2027. 
(ii) For mixtures, all employers shall, 
as necessary, update any alternative workplace labeling used under paragraph (f)(6) of this section, update the hazard communication program required by paragraph (h)(1) of this section, and provide any additional employee training in accordance with paragraph (h)(3) of this section for newly identified physical hazards, health hazards, or other hazards covered under this section no later than January 19, 2028. 
(4) Compliance. Between May 20, 
2024 and the dates specified in paragraphs (j)(2) and (3) of this section, as applicable, chemical manufacturers, importers, distributors, and employers 
may comply with either this section or 
§ 1910.1200 revised as of July 1, 2023, or both during the transition period. 
Appendix A to § 1910.1200—Health 
Hazard Criteria (Mandatory) 
A.0 General Classification Considerations 
A.0.1 Classification 
A.0.1.1 The term ‘‘hazard classification’’ 
is used to indicate that only the intrinsic 
hazardous properties of chemicals are considered. Hazard classification incorporates three steps: 
(a) Identification of relevant data regarding 
the hazards of a chemical; 
(b) Subsequent review of those data to 
ascertain the hazards associated with the chemical; 
(c) Determination of whether the chemical 
will be classified as hazardous and the degree of hazard. 
A.0.1.2 For many hazard classes, the 
criteria are semi-quantitative or qualitative and expert judgment is required to interpret the data for classification purposes. 
A.0.1.3 Where impurities, additives or 
individual constituents of a substance or mixture have been identified and are themselves classified, they should be taken into account during classification if they exceed the cut-off value/concentration limit for a given hazard class. 
A.0.2 Available Data, Test Methods and 
Test Data Quality 
A.0.2.1 There is no requirement for 
testing chemicals. 
A.0.2.2 The criteria for determining 
health hazards are test method neutral, i.e., 
they do not specify particular test methods, as long as the methods are scientifically validated. 
A.0.2.3 The term ‘‘scientifically 
validated’’ refers to the process by which the reliability and the relevance of a procedure 
are established for a particular purpose. Any test that determines hazardous properties, which is conducted according to recognized scientific principles, can be used for purposes of a hazard determination for health hazards. Test conditions need to be standardized so that the results are reproducible with a given substance, and the standardized test yields ‘‘valid’’ data for defining the hazard class of concern. 
A.0.2.4 Existing test data are acceptable 
for classifying chemicals, although expert judgment also may be needed for classification purposes. 
A.0.2.5 The effect of a chemical on 
biological systems is influenced, by the physico-chemical properties of the substance 
and/or ingredients of the mixture and the way in which ingredient substances are biologically available. A chemical need not be classified when it can be shown by conclusive experimental data from 
scientifically validated test methods that the chemical is not biologically available. 
A.0.2.6 For classification purposes, 
epidemiological data and experience on the effects of chemicals on humans (e.g., occupational data, data from accident databases) shall be taken into account in the evaluation of human health hazards of a chemical. 
A.0.3 Classification Based on Weight of 
Evidence 
A.0.3.1 For some hazard classes, 
classification results directly when the data 
satisfy the criteria. For others, classification of a chemical shall be determined on the basis of the total weight of evidence using expert judgment. This means that all available information bearing on the classification of hazard shall be considered together, including the results of valid in vitro tests, relevant animal data, and human 
experience such as epidemiological and clinical studies and well-documented case reports and observations. 
A.0.3.2 The quality and consistency of 
the data shall be considered. Information on chemicals related to the material being classified shall be considered as appropriate, as well as site of action and mechanism or mode of action study results. Both positive and negative results shall be considered together in a single weight-of-evidence determination. 
A.0.3.3 Positive effects which are 
consistent with the criteria for classification, whether seen in humans or animals, shall normally justify classification. Where evidence is available from both humans and animals and there is a conflict between the findings, the quality and reliability of the evidence from both sources shall be evaluated in order to resolve the question of classification. Reliable, good quality human data shall generally have precedence over other data. However, even well-designed and conducted epidemiological studies may lack a sufficient number of subjects to detect relatively rare but still significant effects, or to assess potentially confounding factors. Therefore, positive results from well- conducted animal studies are not necessarily negated by the lack of positive human experience but require an assessment of the robustness, quality and statistical power of both the human and animal data. 
A.0.3.4 Route of exposure, mechanistic 
information, and metabolism studies are pertinent to determining the relevance of an effect in humans. When such information raises doubt about relevance in humans, a lower classification may be warranted. When there is scientific evidence demonstrating that the mechanism or mode of action is not relevant to humans, the chemical should not be classified. 
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A.0.3.5 Both positive and negative results 
are considered together in the weight of 
evidence determination. However, a single positive study performed according to good scientific principles and with statistically and biologically significant positive results may justify classification. 
A.0.4 Considerations for the Classification 
of Mixtures 
A.0.4.1 Except as provided in A.0.4.2, the 
process of classification of mixtures is based 
on the following sequence: 
(a) Where test data are available for the 
complete mixture, the classification of the mixture will always be based on those data; 
(b) Where test data are not available for the 
mixture itself, the bridging principles designated in each health hazard chapter of this appendix shall be considered for 
classification of the mixture; 
(c) If test data are not available for the 
mixture itself, and the available information is not sufficient to allow application of the above-mentioned bridging principles, then the method(s) described in each chapter for estimating the hazards based on the information known will be applied to classify the mixture (e.g., application of cut-off values/concentration limits). 
A.0.4.2 An exception to the above order 
or precedence is made for Carcinogenicity, Germ Cell Mutagenicity, and Reproductive Toxicity. For these three hazard classes, mixtures shall be classified based upon information on the ingredient substances, unless on a case-by-case basis, justification can be provided for classifying based upon the mixture as a whole. See A.5, A.6, and A.7 
of this section for further information on case-by-case bases. 
A.0.4.3 Use of cut-off values/ 
concentration limits 
A.0.4.3.1 When classifying an untested 
mixture based on the hazards of its ingredients, cut-off values/concentration limits for the classified ingredients of the mixture are used for several hazard classes. While the adopted cut-off values/ concentration limits adequately identify the hazard for most mixtures, there may be some that contain hazardous ingredients at lower concentrations than the specified cut-off values/concentration limits that still pose an identifiable hazard. There may also be cases where the cut-off value/concentration limit is considerably lower than the established non- hazardous level for an ingredient. 
A.0.4.3.2 If the classifier has information 
that the hazard of an ingredient will be evident (i.e., it presents a health risk) below 
the specified cut-off value/concentration limit, the mixture containing that ingredient shall be classified accordingly. 
A.0.4.3.3 In exceptional cases, conclusive 
data may demonstrate that the hazard of an ingredient will not be evident ( i.e., it does 
not present a health risk) when present at a level above the specified cut-off value/ concentration limit(s). In these cases the mixture may be classified according to those data. The data must exclude the possibility 
that the ingredient will behave in the mixture in a manner that would increase the hazard over that of the pure substance. Furthermore, the mixture must not contain ingredients that would affect that determination. 
A.0.4.4 Synergistic or antagonistic effects When performing an assessment in 
accordance with these requirements, the evaluator must take into account all available information about the potential occurrence of synergistic effects among the ingredients of the mixture. Lowering classification of a mixture to a less hazardous category on the basis of antagonistic effects may be done only if the determination is supported by sufficient data. 
A.0.5 Bridging Principles for the 
Classification of Mixtures Where Test Data Are Not Available for the Complete Mixture 
A.0.5.1 Where the mixture itself has not 
been tested to determine its toxicity, but there are sufficient data on both the individual ingredients and similar tested mixtures to adequately characterize the hazards of the mixture, these data shall be used in accordance with the following bridging principles, subject to any specific provisions for mixtures for each hazard class. These principles ensure that the classification process uses the available data to the greatest extent possible in characterizing the hazards of the mixture. 
A.0.5.1.1 Dilution For mixtures classified in accordance with 
A.1 through A.10 of this Appendix, if a tested mixture is diluted with a diluent that has an equivalent or lower toxicity classification than the least toxic original ingredient, and which is not expected to affect the toxicity of other ingredients, then: 
(a) The new diluted mixture shall be 
classified as equivalent to the original tested mixture; or 
(b) For classification of acute toxicity in 
accordance with A.1 of this Appendix, paragraph A.1.3.6 (the additivity formula) shall be applied. 
A.0.5.1.2 Batching For mixtures classified in accordance with 
A.1 through A.10 of this Appendix, the toxicity of a tested production batch of a mixture can be assumed to be substantially equivalent to that of another untested production batch of the same mixture, when produced by or under the control of the same chemical manufacturer, unless there is reason to believe there is significant variation such that the toxicity of the untested batch has changed. If the latter occurs, a new classification is necessary. 
A.0.5.1.3 Concentration of mixtures For mixtures classified in accordance with 
A.1, A.2, A.3, A.4, A.8, A.9, or A.10 of this Appendix, if a tested mixture is classified in Category 1, and the concentration of the ingredients of the tested mixture that are in Category 1 is increased, the resulting untested mixture shall be classified in Category 1. A.0.5.1.4 Interpolation within one hazard 
category 
For mixtures classified in accordance with 
A.1, A.2, A.3, A.4, A.8, A.9, or A.10 of this 
Appendix, for three mixtures (A, B and C) with identical ingredients, where mixtures A and B have been tested and are in the same hazard category, and where untested mixture C has the same toxicologically active ingredients as mixtures A and B but has concentrations of toxicologically active ingredients intermediate to the concentrations in mixtures A and B, then mixture C is assumed to be in the same hazard category as A and B. 
A.0.5.1.5 Substantially similar mixtures For mixtures classified in accordance with 
A.1 through A.10 of this Appendix, given the following set of conditions: 
(a) Where there are two mixtures: (i) A + B; (ii) C + B; (b) The concentration of ingredient B is 
essentially the same in both mixtures; 
(c) The concentration of ingredient A in 
mixture (i) equals that of ingredient C in mixture (ii); 
(d) And data on toxicity for A and C are 
available and substantially equivalent; i.e., 
they are in the same hazard category and are not expected to affect the toxicity of B; then 
If mixture (i) or (ii) is already classified 
based on test data, the other mixture can be assigned the same hazard category. 
A.0.5.1.6 Aerosols 
For mixtures classified in accordance with 
A.1, A.2, A.3, A.4, A.8, or A.9 of this Appendix, an aerosol form of a mixture shall be classified in the same hazard category as the tested, non-aerosolized form of the mixture, provided the added propellant does not affect the toxicity of the mixture when spraying. 
A.1 Acute Toxicity A.1.1 Definition 
Acute toxicity refers to serious adverse 
health effects (i.e., lethality) occurring after a 
single or short-term oral, dermal, or 
inhalation exposure to a substance or mixture. 
A.1.2 Classification Criteria for Substances 
A.1.2.1 Substances can be allocated to 
one of four hazard categories based on acute 
toxicity by the oral, dermal or inhalation route according to the numeric cut-off criteria as shown in Table A.1.1. Acute toxicity values are expressed as (approximate) LD50 (oral, dermal) or LC
50(inhalation) values or 
as acute toxicity estimates (ATE). While some in vivo methods determine LD50/LC50 values directly, other newer in vivo methods (e.g., using fewer animals) consider other indicators of acute toxicity, such as significant clinical signs of toxicity, which are used by reference to assign the hazard category. See the footnotes following Table A.1.1 for further explanation on the application of these values. 
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TABLE A.1.1—A CUTE TOXICITY ESTIMATE (ATE) V ALUES AND CRITERIA FOR ACUTE TOXICITY HAZARD CATEGORIES  
Exposure route Category 1 Category 2 Category 3 Category 4 
Oral (mg/kg bodyweight) see: 
Note (a) ................................................... ATE ≤ 5 ...................... >5 ATE ≤ 50 .............. >50 ATE ≤ 300 .......... >300 ATE ≤ 2000. 
Note (b).
Dermal (mg/kg bodyweight) see: 
Note (a) ................................................... ATE ≤ 5 ...................... >50 ATE ≤ 200 .......... >200 ATE ≤ 1000 ...... >1000 ATE ≤ 2000. 
Note (b).
Inhalation—Gases (ppmV) see: 
Note (a) ................................................... ATE ≤ 100 .................. >100 ATE ≤ 500 ........ >500 ATE ≤ 2500 ...... >2500 ATE ≤ 20000. 
Note (b).
Note (c).
Inhalation—Vapors (mg/l) see: 
Note (a) ................................................... ATE ≤ 0.5 ................... >0.5 ATE ≤ 2.0 .......... >2.0 ATE ≤ 10.0 ........ >10.0 ATE ≤ 20.0. 
Note (b).
Note (c).
Note (d).
Inhalation—Dusts and Mists (mg/l) see: 
Note (a) ................................................... ATE ≤ 0.05 ................. >0.05 ATE ≤ 0.5 ........ >0.5 ATE ≤ 1.0 .......... >1.0 ATE ≤ 5.0. 
Note (b).
Note (c).
Note: Gas concentrations are expressed in parts per million per volume (ppmV). Notes to Table A.1.1: 
(a) The acute toxicity estimate (ATE) for the classification of a substance is derived using the LD 50/LC 50where available. 
(b) The acute toxicity estimate (ATE) for the classification of a substance or ingredient in a mixture is derived using: 
(i) the LD 50/LC 50where available. Otherwise, 
(ii) the appropriate conversion value from Table 1.2 that relates to the results of a range test, or (iii) the appropriate conversion value from Table 1.2 that relates to a classification category; (c) Inhalation cut-off values in the table are based on 4 hour testing exposures. Conversion of existing inhalation toxicity data which has been 
generated according to 1 hour exposure is achieved by dividing by a factor of 2 for gases and vapors and 4 for dusts and mists;  
(d) For some substances the test atmosphere will be a vapor which consists of a combination of liquid and gaseous phases. For other sub-
stances the test atmosphere may consist of a vapor which is nearly all the gaseous phase. In these latter cases, classification is based on ppmV as follows: Category 1 (100 ppmV), Category 2 (500 ppmV), Category 3 (2500 ppmV), Category 4 (20000 ppmV). 
The terms ‘‘dust’’, ‘‘mist’’ and ‘‘vapor’’ are defined as follows: (i) Dust: solid particles of a substance or mixture suspended in a gas (usually air); (ii) Mist: liquid droplets of a substance or mixture suspended in a gas (usually air); (iii) Vapor: the gaseous form of a substance or mixture released from its liquid or solid state. 
A.1.2.3 The preferred test species for 
evaluation of acute toxicity by the oral and 
inhalation routes is the rat, while the rat or rabbit are preferred for evaluation of acute dermal toxicity. Test data already generated for the classification of chemicals under existing systems should be accepted when reclassifying these chemicals under the harmonized system. When experimental data for acute toxicity are available in several animal species, scientific judgment should be used in selecting the most appropriate LD
50 
value from among scientifically validated tests. In cases where data from human experience (i.e., occupational data, data from 
accident databases, epidemiology studies, clinical reports) is also available, it should be considered in a weight of evidence approach consistent with the principles described in A.0.3. 
A.1.2.4 In addition to classification for 
inhalation toxicity, if data are available that 
indicates that the mechanism of toxicity was corrosivity of the substance or mixture, the classifier must consider if the chemical is 
corrosive to the respiratory tract. Corrosion of 
the respiratory tract is defined as destruction of the respiratory tract tissue after a single, limited period of exposure analogous to skin corrosion; this includes destruction of the mucosa. The corrosivity evaluation could be based on expert judgment using such evidence as: human and animal experience, existing (in vitro) data, Ph values, information from similar substances or any other pertinent data. 
A.1.2.4.1 If the classifier determines the 
chemical is corrosive to the respiratory tract and data are available that indicate that the effect leads to lethality, then in addition to the appropriate acute toxicity pictogram and hazard statement, the chemical must be labelled with the hazard statement ‘‘corrosive to the respiratory tract’’ and the corrosive pictogram. 
A.1.2.4.2 If the classifier determines the 
chemical is corrosive to the respiratory tract 
and the effect does not lead to lethality, then the chemical must be addressed in the 
Specific Target Organ Toxicity hazard classes (see A.8). If data is insufficient for 
classification under STOT, but the classifier determines, based on skin or eye data, that the chemical may be corrosive to the respiratory tract, then the hazard must be addressed using data for classification in the skin corrosion/irritation hazard class (see A.2) or Serious Eye Damage/Eye irritation hazard class (see A.3). 
A.1.3 Classification Criteria for Mixtures 
A.1.3.1 The approach to classification of 
mixtures for acute toxicity is tiered, and is 
dependent upon the amount of information available for the mixture itself and for its ingredients. The flow chart of Figure A.1.1 indicates the process that must be followed: 
A.1.1 Figure—1 Tiered Approach to 
Classification of Mixtures for Acute Toxicity 
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A.1.3.2 Classification of mixtures for 
acute toxicity may be carried out for each 
route of exposure, but is only required for one route of exposure as long as this route is followed (estimated or tested) for all ingredients and there is no relevant evidence to suggest acute toxicity by multiple routes. When there is relevant evidence of acute toxicity by multiple routes of exposure, classification is to be conducted for all appropriate routes of exposure. All available information shall be considered. The pictogram and signal word used shall reflect the most severe hazard category; and all relevant hazard statements shall be used. 
A.1.3.3 For purposes of classifying the 
hazards of mixtures in the tiered approach: 
(a) The ‘‘relevant ingredients’’ of a mixture 
are those which are present in concentrations ≥1% (weight/weight for solids, liquids, dusts, mists and vapors and volume/volume for gases). If there is reason to suspect that an ingredient present at a concentration <1% will affect classification of the mixture for acute toxicity, that ingredient shall also be considered relevant. Consideration of ingredients present at a concentration <1% is particularly important when classifying untested mixtures which contain ingredients that are classified in Category 1 and Category 2; 
(b) Where a classified mixture is used as 
an ingredient of another mixture, the actual or derived acute toxicity estimate (ATE) for that mixture is used when calculating the classification of the new mixture using the formulas in A.1.3.6.1 and A.1.3.6.2.4. 
(c) If the converted acute toxicity point 
estimates for all ingredients of a mixture are within the same category, then the mixture should be classified in that category. 
(d) When only range data (or acute toxicity 
hazard category information) are available for ingredients in a mixture, they may be converted to point estimates in accordance with Table A.1.2 when calculating the classification of the new mixture using the formulas in A.1.3.6.1 and A.1.3.6.2.4. 
A.1.3.4 Classification of mixtures where 
acute toxicity test data are available for the complete mixture 
Where the mixture itself has been tested to 
determine its acute toxicity, it is classified according to the same criteria as those used for substances, presented in Table A.1.1. If test data for the mixture are not available, the procedures presented below must be followed. 
A.1.3.5 Classification of mixtures where 
acute toxicity test data are not available for the complete mixture: bridging principles 
Where the mixture itself has not been 
tested to determine its acute toxicity, but there are sufficient data on both the individual ingredients and similar tested mixtures to adequately characterize the hazards of the mixture, these data will be used in accordance with the following bridging principles as found in paragraph A.0.5 of this Appendix: Dilution, Batching, Concentration of mixtures, Interpolation within one hazard category, Substantially similar mixtures, and Aerosols. 
A.1.3.6 Classification of mixtures based 
on ingredients of the mixture (additivity formula) 
A.1.3.6.1 Data available for all 
ingredients. 
The acute toxicity estimate (ATE) of 
ingredients is considered as follows: 
(a) Include ingredients with a known acute 
toxicity, which fall into any of the acute hazard categories, or have an oral or dermal LD
50greater than 2000 but less than or equal 
to 5000 mg/kg body weight (or the equivalent dose for inhalation); 
(b) Ignore ingredients that are presumed 
not acutely toxic (e.g., water, sugar); 
(c) Ignore ingredients if the data available 
are from a limit dose test (at the upper threshold for Category 4 for the appropriate route of exposure as provided in Table A.1.1) and do not show acute toxicity. 
Ingredients that fall within the scope of 
this paragraph are considered to be ingredients with a known acute toxicity estimate (ATE). See note (b) to Table A.1.1 
and paragraph A.1.3.3 for appropriate application of available data to the equation below, and paragraph A.1.3.6.2.4. 
The ATE of the mixture is determined by 
calculation from the ATE values for all relevant ingredients according to the following formula below for oral, dermal or inhalation toxicity: 
Where: 
Ci= concentration of ingredient i; 
n ingredients and i is running from 1 to n; 
ATE i= Acute toxicity estimate of ingredient 
i; A.1.3.6.2 Data are not available for one or 
more ingredients of the mixture. 
A.1.3.6.2.1 Where an ATE is not available 
for an individual ingredient of the mixture, but available information provides a derived conversion value, the formula in A.1.3.6.1 may be applied. This information may include evaluation of: 
(a) Extrapolation between oral, dermal and 
inhalation acute toxicity estimates. Such an evaluation requires appropriate 
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pharmacodynamic and pharmacokinetic 
data; 
(b) Evidence from human exposure that 
indicates toxic effects but does not provide lethal dose data; 
(c) Evidence from any other toxicity tests/ 
assays available on the substance that 
indicates toxic acute effects but does not necessarily provide lethal dose data; or 
(d) Data from closely analogous substances 
using structure/activity relationships. 
A.1.3.6.2.2 This approach requires 
substantial supplemental technical information, and a highly trained and experienced expert, to reliably estimate acute toxicity. If sufficient information is not 
available to reliably estimate acute toxicity, proceed to the provisions of A.1.3.6.2.4. 
A.1.3.6.2.3 In the event that an ingredient 
with unknown acute toxicity is used in a mixture at a concentration ≥1%, and the mixture has not been classified based on testing of the mixture as a whole, the mixture cannot be attributed a definitive acute toxicity estimate. In this situation the mixture is classified based on the known ingredients only. 
Note: A statement that × percent of the 
mixture consists of ingredient(s) of unknown acute (oral/dermal/inhalation) toxicity is required on the label and safety data sheet in such cases; see appendix C to this section, Allocation of Label Elements and appendix D to this section, Safety Data Sheets). 
A.1.3.6.2.4 If the total concentration of 
the relevant ingredient(s) with unknown acute toxicity is ≤10% then the formula presented in A.1.3.6.1 must be used. If the total concentration of the relevant ingredient(s) with unknown acute toxicity is ≤10%, the formula presented in A.1.3.6.1 is 
corrected to adjust for the percentage of the unknown ingredient(s) as follows: 
TABLE A.1.2—C ONVERSION FROM EXPERIMENTALLY OBTAINED ACUTE TOXICITY RANGE VALUES (ORACUTE TOXICITY  
HAZARD CATEGORIES ) TOACUTE TOXICITY POINT ESTIMATES FOR USE IN THE FORMULAS FOR THE CLASSIFICATION  
OFMIXTURES  
Exposure routes Classification category or experimentally obtained 
acute toxicity range estimate Converted 
acute toxicity 
point estimate 
Oral (mg/kg bodyweight) ............................................................ 0 < Category 1 ≤ 5 ..................................................................... 0.5 
5 < Category 2 ≤ 50 ................................................................... 5 
50 < Category 3 ≤ 300 ............................................................... 100 
300 < Category 4 ≤ 2000 ........................................................... 500 
Dermal (mg/kg bodyweight) ....................................................... 0 < Category 1 ≤ 50 ................................................................... 5 
50 < Category 2 ≤ 200 ............................................................... 50 
200 < Category 3 ≤ 1000 ........................................................... 300 
1000 < Category 4 ≤ 2000 ......................................................... 1100 
Gases (ppmV) ............................................................................ 0 < Category 1 ≤ 100 ................................................................. 10 
100 < Category 2 ≤ 500 ............................................................. 100 
500 < Category 3 ≤ 2500 ........................................................... 700 
2500 < Category 4 ≤ 20000 ....................................................... 4500 
Vapors (mg/l) .............................................................................. 0 < Category 1 ≤ 0.5 .................................................................. 0.05 
0.5 < Category 2 ≤ 2.0 ............................................................... 0.5 
2.0 < Category 3 ≤ 10.0 ............................................................. 3 
10.0 < Category 4 ≤ 20.0 ........................................................... 11 
Dust/mist (mg/l) .......................................................................... 0 < Category 1 ≤ 0.05 ................................................................ 0.005 
0.05 < Category 2 ≤ 0.5 ............................................................. 0.05 
0.5 < Category 3 ≤ 1.0 ............................................................... 0.5 
1.0 < Category 4 ≤ 5.0 ............................................................... 1.5 
Note: Gas concentrations are expressed in parts per million per volume (ppmV). 
A.2 Skin Corrosion/Irritation 
A.2.1 Definitions and General 
Considerations 
A.2.1.1 Skin corrosion refers to the 
production of irreversible damage to the skin; 
namely, visible necrosis through the epidermis and into the dermis occurring after initial exposure to a substance or mixture. 
Skin irritation refers to the production of 
reversible damage to the skin occurring after initial exposure to a substance or mixture. 
A.2.1.2 To classify, all available and 
relevant information on skin corrosion/ irritation is collected and its quality in terms of adequacy and reliability is assessed. Wherever possible classification should be 
based on data generated using internationally validated and accepted methods, such as OECD Test Guidelines (TG) or equivalent methods. Sections A.2.2.1 to A.2.2.6 provide classification criteria for the different types of information that may be available. A.2.1.3 A tiered approach (see A.2.2.7) 
organizes the available information into 
levels/tiers and provides for decision-making in a structured and sequential manner. Classification results directly when the information consistently satisfies the criteria. However, where the available information gives inconsistent and/or conflicting results within a tier, classification of a substance or a mixture is made on the basis of the weight of evidence within that tier. In some cases when information from different tiers gives inconsistent and/or conflicting results (see A.2.2.7.3) or where data individually are insufficient to conclude on the classification, an overall weight of evidence approach is used (see A.0.3). 
A.2.2 Classification Criteria for Substances 
Substances shall be allocated to one of the 
following categories within this hazard class: 
(a) Category 1 (skin corrosion) This category may be further divided into 
up to three sub-categories (1A, 1B, and 1C), 
which can be used by those authorities requiring more than one designation for corrosivity. 
Corrosive substances should be classified 
in Category 1 where sub-categorization is not required by a competent authority or where data are not sufficient for sub-categorization. 
When data are sufficient, substances may 
be classified in one of the three sub- categories 1A, 1B, or 1C. 
(b) Category 2 (skin irritation) 
A.2.2.1 Classification Based on Standard 
Human Data 
Existing reliable and good quality human 
data on skin corrosion/irritation should be given high weight for classification. Existing human data could be derived from single or repeated exposure(s), for example in occupational, consumer, transport or emergency response scenarios and 
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epidemiological and clinical studies in well- 
documented case reports and observations (see A.0.2.6 and A.0.3). Although human data from accident or poison center databases can provide evidence for classification, absence of incidents is not itself evidence for no classification, as exposures are generally unknown or uncertain. A.2.2.2 Classification Based on Standard 
Animal Test Data 
OECD TG 404 is the currently available 
internationally validated and accepted 
animal test for classification as skin corrosive or irritant (See Table A.2.1 and A.2.2) and is 
the standard animal test. The current version of OECD TG 404 uses a maximum of 3 animals. Results from animal studies conducted under previous versions of OECD TG 404 that used more than 3 animals are also considered standard animal tests. A.2.2.2.1 Skin Corrosion 
A.2.2.2.1.1 A substance is corrosive to the 
skin when it produces destruction of skin 
tissue, namely, visible necrosis through the epidermis and into the dermis, in at least one tested animal after initial exposure up to a 4- hour duration. 
A.2.2.2.1.2 Three sub-categories of 
Category 1 are provided in Table A.2.1, all of which shall be regulated as Category 1. 
TABLE A.2.1—S KINCORROSION CATEGORY AND SUB-CATEGORIESa 
Criteria 
Category 1 ....................... Destruction of skin tissue, namely, visible necrosis through the epidermis and into the dermis, in at least one tested 
animal after exposure ≤4 h. 
Sub-category 1A .............. Corrosive responses in at least one animal following exposure ≤3 min during an observation period ≤1 h. 
Sub-category 1B .............. Corrosive responses in at least one animal following exposure >3 min and ≤1 h and observations ≤14 days. 
Sub-category 1C .............. Corrosive responses in at least one animal after exposures >1 h and ≤ 4 h and observations ≤14 days. 
aThe use of human data is discussed in A.2.2.1. 
A.2.2.2.2 Skin Irritation 
A.2.2.2.2.1 A substance is irritant to skin 
when it produces reversible damage to the 
skin following its application for up to 4 hours. 
A.2.2.2.2.2 A single irritant category 
(Category 2) is presented in the Table A.2.2. A substance is irritant to skin, when after the first application, it produces reversible damage to the skin following its application for up to 4 hours. An irritation category 
(Category 2) is provided that: 
(a) recognizes that some test substances 
may lead to effects which persist throughout the length of the test; and (b) acknowledges that animal responses in 
a test may be variable. 
A.2.2.2.2.3 Reversibility of skin lesions is 
another consideration in evaluating irritant 
responses. When inflammation persists to the end of the observation period in two or more test animals, taking into consideration 
alopecia (limited area), hyperkeratosis, hyperplasia and scaling, then a chemical should be considered to be an irritant. 
A.2.2.2.2.4 Animal irritant responses 
within a test can be quite variable, as they are with corrosion. A separate irritant criterion accommodates cases when there is a significant irritant response but less than the mean score criterion for a positive test. 
For example, a substance should be designated as an irritant if at least 1 of 3 tested animals shows a very elevated mean score according to test method used throughout the study, including lesions persisting at the end of an observation period of normally 14 days. Other responses should also fulfil this criterion. However, it should be ascertained that the responses are the result of chemical exposure. Addition of this criterion increases the sensitivity of the classification system. 
TABLE A.2.2—S KINIRRITATION CATEGORIESa 
Criteria 
Irritant (Category 2) ......... (1) Mean score of ≥2.3 ≤4.0 for erythema/eschar or for edema in at least 2 of 3 testedanimals from gradings at 24, 
48, 72 hours after patch removal or, if reactions are delayed, from grades on 3 consecutive days after the onset of 
skin reactions; or 
(2) Inflammation that persists to the end of the observation period normally 14 days in at hyerplasia, and scaling; or 
(3) In some cases where there is pronounced variability of response among animals, with very definite positive ef-
fects related to chemical exposure in a single animal but less than the criteria above. 
aGrading criteria are understood as described in OECD Test Guideline 404. 
A.2.2.3 Classification Based on In Vitro/Ex Vivo Data 
A.2.2.3.1 The currently available 
individual in vitro/ex vivo test methods 
address either skin irritation or skin corrosion, but do not address both endpoints in one single test. Therefore, classification based solely on in vitro/ex vivo test results may require data from more than one method. 
A.2.2.3.2 Wherever possible classification 
should be based on data generated using internationally validated and accepted in 
vitro/ex vivo test methods, and the classification criteria provided in these test methods needs to be applied. In vitro/ex vivo 
data can only be used for classification when the tested substance is within the applicability domain of the test methods used. Additional limitations described in the published literature should also be taken into 
consideration. 
A.2.2.3.3 Skin corrosion 
A.2.2.3.3.1 Where tests have been 
undertaken in accordance with OECD Test Guidelines (TGs) 430, 431, or 435, a substance is classified for skin corrosion in category 1 (and, where possible and required into sub-categories 1A, 1B, or 1C) based on the criteria in Table A.2.6. 
A.2.2.3.3.2 Some in vitro/ex vivo methods 
do not allow differentiation between sub- 
categories 1B and 1C. Where existing in vitro/ex vivo data cannot distinguish between the sub-categories, additional information has to be taken into account to differentiate between these two sub- categories. Where no or insufficient additional information is available, category 1 is applied. A.2.2.3.3.3 A substance identified as not 
corrosive should be considered for 
classification as skin irritant. 
A.2.2.3.4 Skin irritation 
A.2.2.3.4.1 Where a conclusion of 
corrosivity can be excluded and where tests have been undertaken in accordance with OECD Test Guideline 439, a substance is classified for skin irritation in category 2 based on the criteria in Table A.2.7. 
A.2.2.3.4.2 A negative result in an 
internationally accepted and validated in vitro/ex vivo test for skin irritation, e.g., 
OECD TG 439, can be used to conclude as not 
classified for skin irritation. 
A.2.2.4 Classification Based on Other, 
Existing Skin Data in Animals 
Other existing skin data in animals may be 
used for classification, but there may be 
limitations regarding the conclusions that 
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can be drawn if a substance is highly toxic 
via the dermal route, an in vivo skin corrosion/irritation study may not have been conducted since the amount of test substance to be applied would considerably exceed the toxic dose and, consequently, would result in the death of the animals. When observations of skin corrosion/irritation in acute toxicity studies are made, these data may be used for 
classification, provided that the dilutions used and species tested are relevant. Solid substances (powders) may become corrosive or irritant when moistened or in contact with moist skin or mucous membranes. This is generally indicated in the standardized test methods. 
A.2.2.5 Classification Based on Chemical 
Properties 
Skin effects may be indicated by pH 
extremes such as ≤2 and ≥11.5 especially 
when associated with significant acid/ alkaline reserve (buffering capacity). Generally, such substances are expected to produce significant effects on the skin. In the absence of any other information, a substance is considered corrosive (Skin Category 1) if it has a pH ≤2 or a pH ≥11.5. However, if consideration of acid/alkaline reserve suggests the substance may not be corrosive despite the low or high pH, this needs to be confirmed by other data, preferably from an appropriate validated in vitro/ex vivo test. Buffering capacity and pH can be determined by test methods including OECD TG 122. A.2.2.6 Classification Based on Non-Test 
Methods 
A.2.2.6.1 Classification, including non- 
classification, can be based on non-test 
methods, with due consideration of reliability and applicability, on a case-by- case basis. Such methods include computer models predicting qualitative structure- activity relationships (structural alerts, SAR); quantitative structure-activity relationships (QSARs); computer expert systems; and read- across using analogue and category approaches. 
A.2.2.6.2 Read-across using analogue or 
category approaches requires sufficiently reliable test data on similar substance(s) and justification of the similarity of the tested substance(s) with the substance(s) to be classified. Where adequate justification of the read-across approach is provided, it has in general higher weight than (Q)SARs. 
A.2.2.6.3 Classification based on (Q)SARs 
requires sufficient data and validation of the 
model. The validity of the computer models and the prediction should be assessed using internationally recognized principles for the validation of (Q)SARs. With respect to reliability, lack of alerts in a SAR or expert system is not sufficient evidence for no classification. 
A.2.2.7 Classification in a Tiered Approach 
A.2.2.7.1 A tiered approach to the 
evaluation of initial information should be considered, where applicable (Figure A.2.1), 
recognizing that not all elements may be relevant. However, all available and relevant information of sufficient quality needs to be examined for consistency with respect to the resulting classification. 
A.2.2.7.2 In the tiered approach (Figure 
A.2.1), existing human and animal data form the highest tier, followed by in vitro/ex vivo 
data, other existing skin data in animals, and then other sources of information. Where information from data within the same tier is inconsistent and/or conflicting, the conclusion from that tier is determined by a weight of evidence approach. 
A.2.2.7.3 Where information from several 
tiers is inconsistent and/or conflicting with respect to the resulting classification, information of sufficient quality from a higher tier is generally given a higher weight than information from a lower tier. However, when information from a lower tier would result in a stricter classification than information from a higher tier and there is concern for misclassification, then classification is determined by an overall weight of evidence approach. The same would apply in the case where there is human data indicating irritation but positive results from an in vitro/ex vivo test for 
corrosion. 
Figure A.2.1—Application of the Tiered 
Approach for Skin Corrosion and Irritation 
(a) Before applying the approach, the 
explanatory text in A.2.2.7 should be 
consulted. Only adequate and reliable data of sufficient quality should be included in applying the tiered approach. (b) Information may be inconclusive for 
various reasons, e.g.: 
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—The available data may be of insufficient 
quality, or otherwise insufficient/ 
inadequate for the purpose of classification, e.g., due to quality issues 
related to experimental design and/or reporting. 
—The available data may be insufficient to 
conclude on the classification, e.g., they 
might be adequate to demonstrate irritancy, but inadequate to demonstrate absence of corrosivity. 
—The method used to generate the available 
data may not be suitable for concluding on no classification (see A.2.2. for details). Specifically, in vitro/ex vivo and non-test 
methods need to be validated explicitly for this purpose. 
A.2.3 Classification Criteria for Mixtures 
A.2.3.1 Classification of Mixtures When 
Data Are Available for the Complete Mixture 
A.2.3.1.1 In general, the mixture shall be 
classified using the criteria for substances, 
taking into account the tiered approach to evaluate data for this hazard class (as illustrated in Figure A.2.1) and A.2.3.1.2 and A.2.3.1.3. If classification is not possible using the tiered approach, then the approach described in A.2.3.2, or, if that is not applicable A.2.2.3.3 should be followed. 
A.2.3.1.2 In vitro/ex vivo data generated 
from validated test methods may not have been validated using mixtures; although these methods are considered broadly applicable to mixtures, they can only be used for classification of mixtures when all ingredients of the mixture fall within the applicability domain of the test methods used. Specific limitations regarding applicability domains are described in the respective test methods, and should be taken into consideration as well as any further information on the limitations from the published literature. Where there is reason to assume or evidence indicating that the applicability domain of a particular test method is limited, data interpretation should 
be exercised with caution, or the results should be considered not applicable. 
A.2.3.1.3 In the absence of any other 
information, a mixture is considered corrosive (Skin Category 1) if it has a pH ≤2 or a pH ≥11.5. However, if consideration of 
acid/alkaline reserve suggests the mixture may not be corrosive despite the low or high pH value, this needs to be confirmed by other data, preferably from an appropriate validated in vitro/ex vivo test. 
A.2.3.2 Classification of Mixtures When 
Data Are Not Available for the Complete Mixture: Bridging Principles 
A.2.3.2.1 Where the mixture itself has not 
been tested to determine its skin corrosion/ 
irritation potential, but there are sufficient data on both the individual ingredients and similar tested mixtures to adequately characterize the hazards of the mixture, these data will be used in accordance with the following bridging principles, as found in paragraph A.0.5 of this Appendix: Dilution, Batching, Concentration of mixtures, Interpolation within one hazard category, Substantially similar mixtures, and Aerosols. 
A.2.3.3 Classification of Mixtures When 
Data Are Available for All Ingredients or Only for Some Ingredients of the Mixture 
A.2.3.3.1 In order to make use of all 
available data for purposes of classifying the 
skin corrosion/irritation hazards of mixtures, the following assumption has been made and is applied where appropriate in the tiered approach: 
The ‘‘relevant ingredients’’ of a mixture are 
those which are present in concentrations ≥1% (weight/weight for solids, liquids, dusts, mists and vapors and volume/volume for gases.). If the classifier has reason to suspect that an ingredient present at a concentration <1% will affect classification of the mixture for skin corrosion/irritation, that ingredient shall also be considered relevant. 
A.2.3.3.2 In general, the approach to 
classification of mixtures as corrosive or irritant to the skin when data are available on the ingredients, but not on the mixture as a whole, is based on the theory of additivity, such that each corrosive or irritant ingredient contributes to the overall corrosive or irritant properties of the mixture in proportion to its potency and concentration. A weighting factor of 10 is used for corrosive ingredients when they are present at a concentration below the concentration limit for classification with Category 1, but are at a 
concentration that will contribute to the classification of the mixture as an irritant. The mixture is classified as corrosive or irritant when the sum of the concentrations of such ingredients exceeds a cut-off value/ concentration limit. 
A.2.3.3.3 Table A.2.3 below provides the 
cut-off value/concentration limits to be used to determine if the mixture is considered to be corrosive or irritant to the skin. 
A.2.3.3.4 Particular care shall be taken 
when classifying certain types of chemicals such as acids and bases, inorganic salts, aldehydes, phenols, and surfactants. The approach explained in A.2.3.3.1 and A.2.3.3.2 might not work given that many of 
such substances are corrosive or irritant at concentrations <1%. For mixtures containing strong acids or bases the pH should be used as classification criteria since pH will be a better indicator of corrosion than the concentration limits in Table A.2.3. A mixture containing corrosive or irritant ingredients that cannot be classified based on the additivity approach shown in Table A.2.3, due to chemical characteristics that make this approach unworkable, should be classified as skin corrosion Category 1 if it contains ≥1% of a corrosive ingredient and 
as skin irritation Category 2 when it contains ≥3% of an irritant ingredient. Classification of mixtures with ingredients for which the approach in Table A.2.3 does not apply is summarized in Table A.2.4 below. 
A.2.3.3.5 On occasion, reliable data may 
show that the skin corrosion/irritation of an ingredient will not be evident when present at a level above the generic cut-off values/ concentration limits mentioned in Tables A.2.3 and A.2.4. In these cases the mixture could be classified according to those data (See Use of cut-off values/concentration limits, paragraph A.0.4.3 of this Appendix ). 
A.2.3.3.6 If there are data showing that 
(an) ingredient(s) may be corrosive or irritant to skin at a concentration of <1% (corrosive) or <3% (irritant), the mixture shall be classified accordingly (See Use of cut-off values/concentration limits, paragraph A.0.4.3 of this Appendix). 
TABLE A.2.3—C ONCENTRATION OF INGREDIENTS OF A MIXTURE CLASSIFIED AS SKINCATEGORY 1 OR2 THATWOULD  
TRIGGER CLASSIFICATION OF THE MIXTURE AS HAZARDOUS TO SKIN 
[Category 1 or 2] 
Sum of ingredients classified as: Concentration triggering classi-
fication of a mixture as: 
Skin corrosive Skin irritant 
Category 1 Category 2 
Skin Category 1 ................................................................................................................ .................................... ≥5% ≥1% but <5% 
Skin Category 2 ................................................................................................................ .................................... ........................ ≥10% 
(10 × Skin Category 1) + Skin Category 2 ............................................................................................. .............. ........................ ≥10% 
Note: Where the sub-categories of skin Category 1 (corrosive) are used, the sum of all ingredients of a mixture classified as sub-category 1A, 
1B or 1C respectively, must each be ≥5% in order to classify the mixture as either skin sub-category 1A, 1B or 1C. Where the sum of 1A ingredi-
ents is <5% but the sum of 1A + 1B ingredients is ≥5%, the mixture must be classified as sub-category 1B. Similarly, where the sum of 1A + 1B ingredients is <5% but the sum of 1A + 1B + 1C ingredients is ≥5% the mixture must be classified as sub-category 1C. Where at least one rel-evant ingredient in a mixture is classified as a Category 1 categorization, the mixture must be classified as Category 1 without sub-categorization if the sum of all ingredients corrosive to skin is ≥5%. 
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TABLE A.2.4—C ONCENTRATION OF INGREDIENTS OF A MIXTURE WHEN THE ADDITIVITY APPROACH DOESNOTAPPLY, 
THATWOULD TRIGGER CLASSIFICATION OF THE MIXTURE AS HAZARDOUS TO SKIN 
Ingredient Concentration 
(percent) Mixture classified as: 
Skin 
Acid with pH ≤2 ....................................................................................................................................... ≥1 Category 1. 
Base with pH ≥11.5 ................................................................................................................................. ≥1 Category 1. 
Other corrosive (Category 1) ingredient ........................................................................................ ......... ≥1 Category 1. 
Other irritant (Category 2) ingredient, including acids and bases .......................................................... ≥ 3 Category 2. 
A.3 Serious Eye Damage/Eye Irritation 
A.3.1 Definitions and General 
Considerations 
A.3.1.1 Serious eye damage refers to the 
production of tissue damage in the eye, or 
serious physical decay of vision, which is not fully reversible, occurring after exposure of the eye to a substance or mixture. 
Eye irritation refers to the production of 
changes in the eye, which are fully reversible, occurring after exposure of the eye to a substance or mixture. 
A.3.1.2 Serious eye damage/eye irritation 
shall be classified using a tiered approach as detailed in Figure A.3.1. Emphasis shall be placed upon existing human data ( See 
A.0.2.6), followed by existing animal data, followed by in vitro data and then other sources of information. Classification results directly when the data satisfy the criteria in this section. In case the criteria cannot be directly applied, classification of a substance or a mixture is made on the basis of the total 
weight of evidence (See A.0.3.1). This means 
that all available information bearing on the determination of serious eye damage/eye irritation is considered together, including the results of appropriate scientifically validated in vitro tests, relevant animal data, 
and human data such as epidemiological and clinical studies and well-documented case reports and observations. 
A.3.2 Classification Criteria for Substances 
Substances are allocated to one of the 
categories within this hazard class, Category 
1 (serious eye damage) or Category 2 (eye irritation), as follows: 
(a) Category 1 (serious eye damage/ 
irreversible effects on the eye): substances that have the potential to seriously damage 
the eyes (see Table A.3.1). 
(b) Category 2 (eye irritation/reversible 
effects on the eye): substances that have the potential to induce reversible eye irritation (see Table A.3.2). 
A.3.2.1 Classification Based on Standard 
Animal Test Data 
A.3.2.1.1 Serious eye damage (Category 
1)/Irreversible effects on the eye A single hazard category is provided in 
Table A.3.1, for substances that have the 
potential to seriously damage the eyes. Category 1, irreversible effects on the eye, includes the criteria listed below. These observations include animals with grade 4 cornea lesions and other severe reactions (e.g., destruction of cornea) observed at any time during the test, as well as persistent corneal opacity, discoloration of the cornea by a dye substance, adhesion, pannus, and interference with the function of the iris or other effects that impair sight. In this context, persistent lesions are considered those which are not fully reversible within an observation period of normally 21 days. Category 1 also contains substances fulfilling the criteria of corneal opacity ≥ 3 and/or iritis > 1.5 
observed in at least 2 of 3 tested animals detected in a Draize eye test with rabbits, 
because severe lesions like these usually do 
not reverse within a 21-day observation period. 
TABLE A.3.1—S ERIOUS EYEDAMAGE /IRREVERSIBLE EFFECTS ON THE EYECATEGORYa 
Criteria 
Category 1: Serious eye damage/Ir-
reversible effects on the eye.A substance that produces: 
(a) in at least one animal effects on the cornea, iris or conjunctiva that are not expected to reverse or 
have not fully reversed within an observation period of normally 21 days; and/or 
(b) in at least 2 of 3 tested animals, a positive response of: 
(i) corneal opacity ≥3; and/or 
(ii) iritis >1.5; 
calculated as the mean scores following grading at 24, 48 and 72 hours after instillation of the test mate-
rial. 
aGrading criteria are understood as described in OECD Test Guideline 405. 
A.3.2.1.2 Eye irritation (category 2)/ 
reversible effects on the eye 
A single Category 2 is provided in Table 
A.3.2 for substances that have the potential 
to induce reversible eye irritation. 
When data are available, substances may 
be classified into Category 2A and Category 2B: (a) For substances inducing eye irritant 
effects reversing within an observation time of normally 21 days, Category 2A applies. 
(b) For substances inducing eye irritant 
effects reversing within an observation time of 7 days, Category 2B applies. 
When a substance is classified as Category 
2, without further categorization, the classification criteria are the same as those 
for 2A. 
A.3.2.1.3 For those substances where 
there is pronounced variability among animal responses this information must be taken into account in determining the classification. 
TABLE A.3.2—R EVERSIBLE EFFECTS ON THE EYECATEGORIESa 
Criteria 
Substances that have the potential to induce reversible eye irritation. 
Category 2/2A ................................. Substances that produce in at least 2 of 3 tested animals a positive response of: 
(a) corneal opacity ≥1; and/or. 
(b) iritis ≥1; and/or. 
(c) conjunctival redness ≥2; and/or.’ 
(d) conjunctival oedema (chemosis) ≥2. 
calculated as the mean scores following grading at 24, 48 and 72 hours after instillation of the test mate-
rial, and which fully reverses within an observation period of normally 21 days. 
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TABLE A.3.2—R EVERSIBLE EFFECTS ON THE EYECATEGORIESa—Continued 
Criteria 
Category 2B .................................... Within Category 2A an eye irritant is considered mildly irritating to eyes (Category 2B) when the effects 
listed above are fully reversible within 7 days of observation. 
aGrading criteria are understood as described in OECD Test Guideline 405. 
A.3.2.2 Classification in a Tiered Approach 
A.3.2.2.1 A tiered approach to the 
evaluation of initial information shall be 
used where applicable, recognizing that all elements may not be relevant in certain cases (Figure A.3.1). 
A.3.2.2.2 Existing human and animal data 
should be the first line of analysis, as they give information directly relevant to effects on the eye. Possible skin corrosion shall be evaluated prior to consideration of any testing for serious eye damage/eye irritation in order to avoid testing for local effects on eyes with skin corrosive substances. 
A.3.2.2.3 In vitro alternatives that have 
been validated and accepted should be used to make classification decisions. 
A.3.2.2.4 Likewise, pH extremes like ≤2 
and ≥11.5, may indicate serious eye damage, 
especially when associated with significant 
acid/alkaline reserve (buffering capacity). Generally, such substances are expected to produce significant effects on the eyes. In the 
absence of any other information, a substance is considered to cause serious eye damage (Category 1) if it has a pH ≤2 or ≥11.5. 
However, if consideration of acid/alkaline reserve suggests the substance may not cause serious eye damage despite the low or high pH value, this needs to be confirmed by other data, preferably by data from an appropriate validated in vitro test. 
A.3.2.2.5 In some cases sufficient 
information may be available from structurally related substances to make classification decisions. 
A.3.2.2.6 The tiered approach provides 
guidance on how to organize existing information and to make a weight-of- evidence decision about hazard assessment and hazard classification (ideally without conducting new animal tests). Animal testing with corrosive substances should be avoided wherever possible. Although information might be gained from the evaluation of single parameters within a tier, consideration 
should be given to the totality of existing information and making an overall weight of evidence determination. This is especially true when there is conflict in information 
available on some parameters. 
A.3.2.2.7 The tiered approach explains 
how to organize existing information and to make a weight-of-evidence decision about hazard assessment and hazard classification. Although information might be gained from the evaluation of single parameters within a tier, consideration should be given to the totality of existing information and making an overall weight of evidence determination. This is especially true when there is conflict in information available. 
BILLING CODE 4510–26–P 
Figure A.3.1—Tiered Evaluation for Serious 
Eye Damage and Eye Irritation (See Also Figure A.2.1) 
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BILLING CODE 4510–26–C 
aExisting human or animal data could be 
derived from single or repeated exposure(s), 
for example in occupational, consumer, transport, or emergency response scenarios; or from purposely-generated data from animal studies conducted according to validated and internationally accepted test methods. Although human data from accident or poison center databases can provide evidence for classification, absence of incidents is not itself evidence for no classification as exposures are generally unknown or uncertain; 
bClassify in the appropriate category as 
applicable; 
cExisting animal data should be carefully 
reviewed to determine if sufficient serious eye damage/eye irritation evidence is available through other, similar information. It is recognized that not all skin irritants are eye irritants. Expert judgment should be exercised prior to making such a determination; 
dEvidence from studies using validated 
protocols with isolated human/animal tissues or other non-tissue-based, validated protocols should be assessed. Examples of internationally accepted, validated test methods for identifying eye corrosives and severe irritants (i.e., Serious Eye Damage) include OECD Test Guidelines 437 (Bovine Corneal Opacity and Permeability (BCOP)), 438 (Isolated Chicken Eye (ICE) and 460 (Fluorescein leakage (FL)). Presently there are no validated and internationally accepted in vitro test methods for identifying eye irritation. A positive test result from a validated in vitro test on skin corrosion would lead to the conclusion to classify as causing serious eye damage; 
eMeasurement of pH alone may be 
adequate, but assessment of acid/alkaline 
reserve (buffering capacity) would be preferable. Presently, there is no validated and internationally accepted method for assessing this parameter; 
fAll information that is available on a 
substance must be considered and an overall determination made on the total weight of 
evidence. This is especially true when there is conflict in information available on some parameters. The weight of evidence including information on skin irritation may lead to classification for eye irritation. Negative results from applicable validated in vitro tests are considered in the total weight of evidence evaluation. 
A.3.3 Classification Criteria for Mixtures 
A.3.3.1 Classification of Mixtures When 
Data Are Available for the Complete Mixture 
A.3.3.1.1 The mixture will be classified 
using the criteria for substances, and taking 
into account the tiered approach to evaluate data for this hazard class (as illustrated in Figure A.3.1). 
A.3.3.1.2 When considering testing of the 
mixture, chemical manufacturers shall use a tiered approach as included in the criteria for classification of substances for skin corrosion and serious eye damage and eye irritation to help ensure an accurate classification, as well as to avoid unnecessary animal testing. In the absence of any other information, a mixture is considered to cause serious eye damage (Category 1) if it has a pH ≤2 or ≥11.5. 
However, if consideration of acid/alkaline reserve suggests the mixture may not have the potential to cause serious eye damage despite the low or high pH value, then further evaluation may be necessary. 
A.3.3.2 Classification of Mixtures When 
Data Are Not Available for the Complete Mixture: Bridging Principles 
A.3.3.2.1 Where the mixture itself has not 
been tested to determine its skin corrosivity 
or potential to cause serious eye damage or eye irritation, but there are sufficient data on both the individual ingredients and similar tested mixtures to adequately characterize the hazards of the mixture, these data will be used in accordance with the following bridging principles, as found in paragraph A.0.5 of this Appendix: Dilution, Batching, Concentration of mixtures, Interpolation within one hazard category, Substantially 
similar mixtures, and Aerosols. 
A.3.3.3 Classification of Mixtures When 
Data Are Available for All Ingredients or Only for Some Ingredients of the Mixture 
A.3.3.3.1 For purposes of classifying the 
serious eye damage/eye irritation hazards of 
mixtures in the tiered approach: 
The ‘‘relevant ingredients’’ of a mixture are 
those which are present in concentrations ≥1% (weight/weight for solids, liquids, dusts, mists and vapors and volume/volume for gases.) If the classifier has reason to suspect that an ingredient present at a concentration <1% will affect classification of the mixture for serious eye damage/eye irritation, that ingredient shall also be considered relevant. 
A.3.3.3.2 In general, the approach to 
classification of mixtures as seriously damaging to the eye or eye irritant when data are available on the ingredients, but not on the mixture as a whole, is based on the theory of additivity, such that each skin 
corrosive or serious eye damage/eye irritant ingredient contributes to the overall serious eye damage/eye irritation properties of the mixture in proportion to its potency and concentration. A weighting factor of 10 is used for skin corrosive and serious eye damaging ingredients when they are present at a concentration below the concentration limit for classification with Category 1, but are at a concentration that will contribute to the classification of the mixture as serious eye damaging/eye irritant. The mixture is classified as seriously damaging to the eye or eye irritant when the sum of the concentrations of such ingredients exceeds a threshold cut-off value/concentration limit. 
A.3.3.3.3 Table A.3.3 provides the cut-off 
value/concentration limits to be used to determine if the mixture must be classified as seriously damaging to the eye or an eye irritant. 
A.3.3.3.4 Particular care must be taken 
when classifying certain types of chemicals such as acids and bases, inorganic salts, aldehydes, phenols, and surfactants. The 
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approach explained in A.3.3.3.1 and 
A.3.3.3.2 might not work given that many of such substances are seriously damaging to the eye/eye irritating at concentrations <1%. For mixtures containing strong acids or bases, the pH should be used as classification criteria (See A.3.3.1.2) since pH will be a 
better indicator of serious eye damage (subject to consideration of acid/alkali reserve) than the concentration limits of Table A.3.3. A mixture containing skin corrosive or serious eye damaging/eye irritating ingredients that cannot be classified based on the additivity approach applied in Table A.3.3 due to chemical characteristics that make this approach unworkable, should be classified as serious eye damage (Category 1) if it contains ≥1% of a skin corrosive or serious eye damaging ingredient and as Eye Irritation (Category 2) when it contains ≥3% of an eye irritant ingredient. Classification of mixtures with ingredients for which the approach in Table A.3.3 does not apply is summarized in Table A.3.4. 
A.3.3.3.5 On occasion, reliable data may 
show that the irreversible/reversible eye effects of an ingredient will not be evident when present at a level above the generic cut- off values/concentration limits mentioned in Tables A.3.3 and A.3.4. In these cases the mixture could be classified according to those data (See also A.0.4.3 Use of cut-off 
values/concentration limits’’). On occasion, when it is expected that the skin corrosion/ irritation or the reversible/irreversible eye effects of an ingredient will not be evident when present at a level above the generic 
concentration/cut-off levels mentioned in Tables A.3.3 and A.3.4, testing of the mixture may be considered. In those cases, the tiered weight of evidence approach should be applied as referred to in section A.3.2, Figure A.3.1 and explained in detail in this chapter. 
A.3.3.3.6 If there are data showing that 
(an) ingredient(s) may be corrosive to the skin or seriously damaging to the eye/eye irritating at a concentration of ≤1% (corrosive to the skin or seriously damaging to the eye) or ≤3% (eye irritant), the mixture shall be 
classified accordingly (See also paragraph A.0.4.3, Use of cut-off values/concentration 
limits). 
TABLE A.3.3—C ONCENTRATION OF INGREDIENTS OF A MIXTURE CLASSIFIED AS SKINCATEGORY 1 AND/OREYE 
CATEGORY 1 OR2 THATWOULD TRIGGER CLASSIFICATION OF THE MIXTURES AS HAZARDOUS TO THE EYE 
Sum of ingredients classified as Concentration triggering 
classification of a mixture as 
Serious eye 
damage Eye irritation 
Category 1 Category 2/2A 
Skin corrosion (Category 1) + Serious eye damage (Category 1)a.................................................................... ≥3% ≥1% but <3% 
Eye irritation (Category 2) .................................................................................................... ................................ ........................ ≥10%b 
10 × (Skin corrosion (Category 1) + Serious eye damage (Category 1))a+ Eye irritation (Category 2) ........... ........................ ≥10% 
Notes: 
aIf an ingredient is classified as both skin Category 1 and eye Category 1 its concentration is considered only once in the calc ulation. 
bA mixture may be classified as Eye Irritation Category 2B in cases when all relevant ingredients are classified as Eye Irritation Category 2B. 
TABLE A.3.4—C ONCENTRATION OF INGREDIENTS OF A MIXTURE FOR WHICH THE ADDITIVITY APPROACH DOESNOT 
APPLY, THATWOULD TRIGGER CLASSIFICATION OF THE MIXTURE AS HAZARDOUS TO THE EYE 
Ingredient Concentration 
(percent) Mixture classified as 
Acid with pH <2 ............................................................................................................ ≥1 Serious eye damage (Category 1). 
Base with pH ≥11.5 ...................................................................................................... ≥1 Serious eye damage (Category 1). 
Other skin corrosive or serious eye damage (Category 1) ingredients ....................... ≥1 Serious eye damage (Category 1). 
Other eye irritant (Category 2) ingredients .................................................................. ≥3 Eye irritation (Category 2). 
A.4 Respiratory or Skin Sensitization 
A.4.1 Definitions and General 
Considerations 
A.4.1.1 Respiratory sensitization refers to 
hypersensitivity of the airways occurring 
after inhalation of a substance or mixture. 
Skin sensitization refers to an allergic 
response occurring after skin contact with a substance or mixture. 
A.4.1.2 For the purpose of this chapter, 
sensitization includes two phases: the first phase is induction of specialized immunological memory in an individual by 
exposure to an allergen. The second phase is elicitation, i.e., production of a cell-mediated 
or antibody-mediated allergic response by exposure of a sensitized individual to an allergen. 
A.4.1.3 For respiratory sensitization, the 
pattern of induction followed by elicitation phases is shared in common with skin sensitization. For skin sensitization, an 
induction phase is required in which the immune system learns to react; clinical symptoms can then arise when subsequent exposure is sufficient to elicit a visible skin reaction (elicitation phase). As a consequence, predictive tests usually follow this pattern in which there is an induction phase, the response to which is measured by a standardized elicitation phase, typically involving a patch test. The local lymph node assay is the exception, directly measuring the induction response. Evidence of skin sensitization in humans normally is assessed by a diagnostic patch test. 
A.4.1.4 Usually, for both skin and 
respiratory sensitization, lower levels are necessary for elicitation than are required for induction. 
A.4.1.5 The hazard class ‘‘respiratory or 
skin sensitization’’ is differentiated into: 
(a) Respiratory sensitization; and (b) Skin sensitization 
A.4.2 Classification Criteria for Substances 
A.4.2.1 Respiratory Sensitizers 
A.4.2.1.1 Hazard Categories 
A.4.2.1.1.1 Effects seen in either humans 
or animals will normally justify classification 
in a weight of evidence approach for respiratory sensitizers. Substances may be allocated to one of the two sub-categories 1A or 1B using a weight of evidence approach in accordance with the criteria given in Table A.4.1 and on the basis of reliable and good quality evidence from human cases or epidemiological studies and/or observations from appropriate studies in experimental animals. 
A.4.2.1.1.2 Where data are not sufficient 
for sub-categorization, respiratory sensitizers 
shall be classified in Category 1. 
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1As of May 20, 2024, recognized and validated 
animal models for the testing of respiratory 
hypersensitivity are not available. Under certain circumstances, data from animal studies may provide valuable information in a weight of evidence assessment. 
2At this writing, recognized and validated animal 
models for the testing of respiratory hypersensitivity are not available. Under certain circumstances, data from animal studies may provide valuable information in a weight of evidence assessment. 
3The mechanisms by which substances induce 
symptoms of asthma are not yet fully known. For 
preventive measures, these substances are considered respiratory sensitizers. However, if on the basis of the evidence, it can be demonstrated 
that these substances induce symptoms of asthma by irritation only in people with bronchial hyperactivity, they should not be considered as respiratory sensitizers. TABLE A.4.1—H AZARD CATEGORY AND SUB-CATEGORIES FOR RESPIRATORY SENSITIZERS  
Category 1 Respiratory sensitizer 
A substance is classified as a respiratory sensitizer 
(a) if there is evidence in humans that the substance can lead to specific respiratory hypersensitivity 
and/or 
(b) if there are positive results from an appropriate animal test.1 
Sub-category 1A ............................. Substances showing a high frequency of occurrence in humans; or a probability of occurrence of a high 
sensitization rate in humans based on animal or other tests.1Severity of reaction may also be consid-
ered. 
Sub-category 1B ............................. Substances showing a low to moderate frequency of occurrence in humans; or a probability of occurrence 
of a low to moderate sensitization rate in humans based on animal or other tests.1Severity of reaction 
may also be considered. 
A.4.2.1.2 Human Evidence 
A.4.2.1.2.1 Evidence that a substance can 
lead to specific respiratory hypersensitivity 
will normally be based on human experience. 
In this context, hypersensitivity is normally seen as asthma, but other hypersensitivity reactions such as rhinitis/conjunctivitis and alveolitis are also considered. The condition will have the clinical character of an allergic reaction. However, immunological mechanisms do not have to be demonstrated. 
A.4.2.1.2.2 When considering the human 
evidence, it is necessary that in addition to the evidence from the cases, the following be taken into account: 
(a) The size of the population exposed; (b) The extent of exposure. A.4.2.1.3 The evidence referred to above 
could be: 
(a) Clinical history and data from 
appropriate lung function tests related to exposure to the substance, confirmed by other supportive evidence which may include: 
(i) In vivo immunological test (e.g., skin 
prick test); 
(ii) In vitro immunological test (e.g., 
serological analysis); 
(iii) Studies that may indicate other 
specific hypersensitivity reactions where immunological mechanisms of action have 
not been proven, e.g., repeated low-level 
irritation, pharmacologically mediated effects; 
(iv) A chemical structure related to 
substances known to cause respiratory hypersensitivity; 
(b) Data from positive bronchial challenge 
tests with the substance conducted according to accepted guidelines for the determination of a specific hypersensitivity reaction. 
A.4.2.1.2.4 Clinical history should 
include both medical and occupational history to determine a relationship between exposure to a specific substance and development of respiratory hypersensitivity. Relevant information includes aggravating factors both in the home and workplace, the onset and progress of the disease, family history and medical history of the patient in question. The medical history should also include a note of other allergic or airway disorders from childhood and smoking history. 
A.4.2.1.2.5 The results of positive 
bronchial challenge tests are considered to provide sufficient evidence for classification on their own. It is, however, recognized that 
in practice many of the examinations listed above will already have been carried out. 
A.4.2.1.3 Animal studies A.4.2.1.2.3 Data from appropriate animal 
studies
2which may be indicative of the 
potential of a substance to cause sensitization 
by inhalation in humans3may include: 
(a) Measurements of Immunoglobulin E 
(IgE) and other specific immunological parameters, for example in mice 
(b) Specific pulmonary responses in guinea 
pigs. 
A.4.2.2 Skin Sensitizers 
A.4.2.2.1 Hazard categories 
A.4.2.2.1.1 Effects seen in either humans 
or animals will normally justify classification in a weight of evidence approach for skin sensitizers. Substances may be allocated to one of the two sub-categories 1A or 1B using a weight of evidence approach in accordance with the criteria given in Table A.4.2 and on the basis of reliable and good quality evidence from human cases or epidemiological studies and/or observations from appropriate studies in experimental animals according to the guidance values provided in A.4.2.2.2.1 and A.4.2.2.3.2 for sub-category 1A and in A.4.2.2.2.2 and A.4.2.2.3.3 for sub-category 1B. 
A.4.2.2.1.2 Where data are not sufficient 
for sub-categorization, skin sensitizers shall be classified in Category 1. 
TABLE A.4.2—H AZARD CATEGORY AND SUB-CATEGORIES FOR SKINSENSITIZERS  
Category 1 Skin sensitizer 
A substance is classified as a skin sensitizer 
(a) if there is evidence in humans that the substance can lead to sensitization by skin contact in a 
substantial number of persons, or 
(b) if there are positive results from an appropriate animal test. 
Sub-category 1A ............................. Substances showing a high frequency of occurrence in humans and/or a high potency in animals can be 
presumed to have the potential to produce significant sensitization in humans. Severity of reaction may 
also be considered. 
Sub-category 1B ............................. Substances showing a low to moderate frequency of occurrence in humans and/or a low to moderate po-
tency in animals can be presumed to have the potential to produce sensitization in humans. Severity of reaction may also be considered. 
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4Test methods for skin sensitization are 
described in OECD Guideline 406 (the Guinea Pig 
Maximization test and the Buehler guinea pig test) and Guideline 429 (Local Lymph Node Assay). Other methods may be used provided that they are 
scientifically validated. The Mouse Ear Swelling 
Test (MEST), appears to be a reliable screening test to detect moderate to strong sensitizers, and can be used, in accordance with professional judgment, as 
a first stage in the assessment of skin sensitization potential. A.4.2.2.2 Human Evidence 
A.4.2.2.2.1 Human evidence for sub- 
category 1A may include: 
(a) Positive responses at ≤500 mg/cm2 
(Human Repeat Insult Patch Test (HRIPT), 
Human Maximization Test (HMT)— induction threshold); 
(b) Diagnostic patch test data where there 
is a relatively high and substantial incidence 
of reactions in a defined population in relation to relatively low exposure; 
(c) Other epidemiological evidence where 
there is a relatively high and substantial incidence of allergic contact dermatitis in 
relation to relatively low exposure. 
A.4.2.2.2.2 Human evidence for sub- 
category 1B may include: 
(a) Positive responses at >500 mg/cm2 
(HRIPT, HMT—induction threshold); 
(b) Diagnostic patch test data where there 
is a relatively low but substantial incidence 
of reactions in a defined population in relation to relatively high exposure; 
(c) Other epidemiological evidence where 
there is a relatively low but substantial incidence of allergic contact dermatitis in relation to relatively high exposure. A.4.2.2.3 Animal Studies 
A.4.2.2.3.1 For Category 1, when an 
adjuvant type test method for skin 
sensitization is used, a response of at least 30% of the animals is considered as positive. For a non-adjuvant Guinea pig test method, a response of at least 15% of the animals is considered positive. For Category 1, a stimulation index of three or more is considered a positive response in the local lymph node assay.
4 
A.4.2.2.3.2 Animal test results for sub- 
category 1A can include data with values indicated in the following Table A.4.3: 
TABLE A.4.3—A NIMAL TESTRESULTS FOR SUB-CATEGORY 1A 
Assay Criteria 
Local lymph node assay ................. EC3 value ≤2%. 
Guinea pig maximization test ......... ≥30% responding at ≤0.1% intradermal induction dose or ≥60% responding at >0.1% to ≤1% intradermal induction dose. 
Buehler assay ................................. ≥15% responding at ≤0.2% topical induction dose or ≥60% responding at >0.2% to ≤20% topical induction dose. 
Note: EC3 refers to the estimated concentration of test chemical required to induce a stimulation index of 3 in the local lymph node assay. 
A.4.2.2.3.3 Animal test results for sub- 
category 1B can include data with values 
indicated in Table A.4.4 below: 
TABLE A.4.4—A NIMAL TESTRESULTS FOR SUB-CATEGORY 1B 
Assay Criteria 
Local lymph node assay ................. EC3 value >2%. 
Guinea pig maximization test ......... ≥30% to <60% responding at >0.1% to ≤1% intradermal induction dose or 
≥30% responding at >1% intradermal induction dose. 
Buehler assay ................................. ≥15% to <60% responding at >0.2% to ≤20% topical induction dose or ≥15% responding at >20% topical induction dose. 
Note: EC3 refers to the estimated concentration of test chemical required to induce a stimulation index of 3 in the local lymph node assay. 
A.4.2.2.4 Specific Considerations 
A.4.2.2.4.1 For classification of a 
substance, evidence shall include one or 
more of the following using a weight of evidence approach: 
(a) Positive data from patch testing, 
normally obtained in more than one dermatology clinic; 
(b) Epidemiological studies showing 
allergic contact dermatitis caused by the substance. Situations in which a high proportion of those exposed exhibit characteristic symptoms are to be looked at with special concern, even if the number of cases is small; 
(c) Positive data from appropriate animal 
studies; 
(d) Positive data from experimental studies 
in humans (See paragraph A.0.2.6 of this 
Appendix); 
(e) Well documented episodes of allergic 
contact dermatitis, normally obtained in more than one dermatology clinic; 
(f) Severity of reaction. A.4.2.2.4.2 Evidence from animal studies 
is usually much more reliable than evidence from human exposure. However, in cases 
where evidence is available from both sources, and there is conflict between the results, the quality and reliability of the evidence from both sources must be assessed in order to resolve the question of classification on a case-by-case basis. Normally, human data are not generated in controlled experiments with volunteers for the purpose of hazard classification but rather as part of risk assessment to confirm lack of effects seen in animal tests. Consequently, positive human data on skin sensitization are usually derived from case- control or other, less defined studies. Evaluation of human data must, therefore, be carried out with caution as the frequency of cases reflect, in addition to the inherent properties of the substances, factors such as the exposure situation, bioavailability, individual predisposition and preventive measures taken. Negative human data should 
not normally be used to negate positive results from animal studies. For both animal and human data, consideration should be given to the impact of vehicle. A.4.2.2.4.3 If none of the above- 
mentioned conditions are met, the substance 
need not be classified as a skin sensitizer. However, a combination of two or more indicators of skin sensitization, as listed below, may alter the decision. This shall be considered on a case-by-case basis. 
(a) Isolated episodes of allergic contact 
dermatitis; 
(b) Epidemiological studies of limited 
power, e.g., where chance, bias or 
confounders have not been ruled out fully with reasonable confidence; 
(c) Data from animal tests, performed 
according to existing guidelines, which do not meet the criteria for a positive result described in A.4.2.2.3, but which are sufficiently close to the limit to be considered significant; 
(d) Positive data from non-standard 
methods; 
(e) Positive results from close structural 
analogues. 
A.4.2.2.4.4 Immunological contact 
urticaria 
A.4.2.2.4.4.1 Substances meeting the 
criteria for classification as respiratory 
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sensitizers may, in addition, cause 
immunological contact urticaria. Consideration shall be given to classifying these substances as skin sensitizers. 
A.4.2.2.4.4.2 Substances which cause 
immunological contact urticaria without meeting the criteria for respiratory sensitizers shall be considered for classification as skin sensitizers. 
A.4.2.2.4.4.3 There is no recognized 
animal model available to identify substances which cause immunological contact urticaria. Therefore, classification will normally be based on human evidence, similar to that for skin sensitization. A.4.3 Classification Criteria for Mixtures 
A.4.3.1 Classification of Mixtures When 
Data Are Available for the Complete Mixture 
When reliable and good quality evidence, 
as described in the criteria for substances, 
from human experience or appropriate studies in experimental animals, is available for the mixture, then the mixture shall be classified by weight of evidence evaluation of these data. Care must be exercised in evaluating data on mixtures that the dose used does not render the results inconclusive. 
A.4.3.2 Classification of Mixtures When 
Data Are Not Available for the Complete Mixture: Bridging Principles 
A.4.3.2.1 Where the mixture itself has not 
been tested to determine its sensitizing 
properties, but there are sufficient data on both the individual ingredients and similar 
tested mixtures to adequately characterize 
the hazards of the mixture, these data will be used in accordance with the following agreed bridging principles as found in paragraph A.0.5 of this Appendix: Dilution, Batching, Concentration of mixtures, Interpolation within one hazard category/subcategory, Substantially similar mixtures, and Aerosols. 
A.4.3.3 Classification of Mixtures When 
Data Are Available for All Ingredients or Only for Some Ingredients of the Mixture 
The mixture shall be classified as a 
respiratory or skin sensitizer when at least 
one ingredient has been classified as a respiratory or skin sensitizer and is present at or above the appropriate cut-off value/ concentration limit for the specific endpoint as shown in Table A.4.5. 
TABLE A.4.5—C UT-OFFVALUES /CONCENTRATION LIMITS OF INGREDIENTS OF A MIXTURE CLASSIFIED AS EITHER  
RESPIRATORY SENSITIZERS OR SKINSENSITIZERS THATWOULD TRIGGER CLASSIFICATION OF THE MIXTURE  
Ingredient classified as Cut-off values/concentration limits triggering classi-
fication of a mixture as 
Respiratory sensitizer 
Category 1 Skin sensitizer 
Category 1 
Solid/liquid 
(%) Gas 
(%) All physical states 
(%) 
Respiratory Sensitizer Category 1 ......................................................................................... ≥0.1 ≥0.1 ..............................
Respiratory Sensitizer Sub-category 1A ............................................................................... ≥0.1 ≥0.1 ..............................
Respiratory Sensitizer Sub-category 1B ............................................................................... ≥1.0 ≥0.2 ..............................
Skin Sensitizer Category 1 .................................................................................................... . ....................... ........................ ≥0.1 
Skin Sensitizer Sub-category 1A ........................................................................................... ..... ................... ........................ ≥0.1 
Skin Sensitizer Sub-category 1B ........................................................................................... ..... ................... ........................ ≥1.0 
A.5 Germ Cell Mutagenicity 
A.5.1 Definitions and General 
Considerations 
A.5.1.1 Germ cell mutagenicity refers to 
heritable gene mutations, including heritable 
structure and numerical chromosome aberrations in germ cells occurring after exposure to a substance or mixture. 
A.5.1.2 A mutation is defined as a 
permanent change in the amount or structure of the genetic material in a cell. The term mutation applies both to heritable genetic 
changes that may be manifested at the phenotypic level and to the underlying DNA modifications when known (including, for example, specific base pair changes and chromosomal translocations). The term 
mutagenic and mutagen will be used for 
agents giving rise to an increased occurrence of mutations in populations of cells and/or organisms. 
A.5.1.3 The more general terms genotoxic 
and genotoxicity apply to agents or processes 
which alter the structure, information content, or segregation of DNA, including those which cause DNA damage by interfering with normal replication processes, or which in a non-physiological manner (temporarily) alter its replication. Genotoxicity test results are usually taken as indicators for mutagenic effects. 
A.5.1.4 This hazard class is primarily 
concerned with chemicals that may cause mutations in the germ cells of humans that can be transmitted to the progeny. However, 
mutagenicity/genotoxicity tests in vitro and in mammalian somatic cells in vivo are also considered in classifying substances and mixtures within this hazard class. 
A.5.2 Classification Criteria for Substances 
A.5.2.1 The classification system 
provides for two different categories of germ 
cell mutagens to accommodate the weight of evidence available. The two-category system is described in the Figure A.5.1. 
Figure A.5.1—Hazard Categories for Germ 
Cell Mutagens 
CATEGORY 1: Substances known to induce 
heritable mutations or to be regarded as 
if they induce heritable mutations in the germ cells of humans 
Category 1A: Substances known to induce 
heritable mutations in germ cells of 
humans 
Positive evidence from human 
epidemiological studies. 
Category 1B: Substances which should be 
regarded as if they induce heritable mutations in the germ cells of humans 
(a) Positive result(s) from in vivo heritable 
germ cell mutagenicity tests in mammals; or 
(b) Positive result(s) from in vivo somatic 
cell mutagenicity tests in mammals, in combination with some evidence that the substance has potential to cause mutations to germ cells. This supporting evidence may, for example, be derived 
from mutagenicity/genotoxic tests in germ cells in vivo, or by demonstrating the ability of the substance or its metabolite(s) to interact with the genetic material of germ cells; or 
(c) Positive results from tests showing 
mutagenic effects in the germ cells of humans, without demonstration of transmission to progeny; for example, an increase in the frequency of aneuploidy in sperm cells of exposed people. 
CATEGORY 2: Substances which cause 
concern for humans owing to the possibility that they may induce heritable mutations in the germ cells of humans 
Positive evidence obtained from 
experiments in mammals and/or in some cases from in vitro experiments, obtained from: 
(a) Somatic cell mutagenicity tests in vivo, 
in mammals; or 
(b) Other in vivo somatic cell genotoxicity 
tests which are supported by positive results from in vitro mutagenicity assays. 
Note: Substances which are positive in in 
vitro mammalian mutagenicity assays, and 
which also show structure activity relationship to known germ cell mutagens, should be considered for classification as Category 2 mutagens. 
A.5.2.2 Specific considerations for 
classification of substances as germ cell mutagens: 
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5It should be noted that the classification criteria 
for health hazards usually include a tiered scheme 
in which test data available on the complete mixture are considered as the first tier in the evaluation, followed by the applicable bridging principles, and lastly, cut-off values/concentration 
limits or additivity. However, this approach is not used for Germ Cell Mutagenicity. These criteria for Germ Cell Mutagenicity consider the cut-off values/ 
concentration limits as the primary tier and allow the classification to be modified only on a case-by- case evaluation based on available test data for the mixture as a whole. 
6See Non-mandatory appendix F of this section, 
part A for further guidance regarding hazard classification for carcinogenicity. This appendix is consistent with the GHS and is provided as guidance excerpted from the International Agency for Research on Cancer (IARC) ‘‘Monographs on the Evaluation of Carcinogenic Risks to Humans’’ (2006). A.5.2.2.1 To arrive at a classification, test 
results are considered from experiments 
determining mutagenic and/or genotoxic effects in germ and/or somatic cells of exposed animals. Mutagenic and/or genotoxic effects determined in in vitro tests shall also be considered. 
A.5.2.2.2 The system is hazard based, 
classifying chemicals on the basis of their intrinsic ability to induce mutations in germ cells. The scheme is, therefore, not meant for the (quantitative) risk assessment of chemical substances. 
A.5.2.2.3 Classification for heritable 
effects in human germ cells is made on the 
basis of scientifically validated tests. Evaluation of the test results shall be done using expert judgment and all the available 
evidence shall be weighed for classification. 
A.5.2.2.4 The classification of substances 
shall be based on the total weight of evidence available, using expert judgment. In those instances where a single well-conducted test is used for classification, it shall provide clear and unambiguously positive results. The relevance of the route of exposure used in the study of the substance compared to the route of human exposure should also be taken into account. A.5.3 Classification Criteria for Mixtures
5 
A.5.3.1 Classification of Mixtures When 
Data Are Available for All Ingredients or Only for Some Ingredients of the Mixture 
A.5.3.1.1 Classification of mixtures shall 
be based on the available test data for the individual ingredients of the mixture using cut-off values/concentration limits for the ingredients classified as germ cell mutagens. 
A.5.3.1.2 The mixture will be classified 
as a mutagen when at least one ingredient has been classified as a Category 1A, Category 1B or Category 2 mutagen and is present at or above the appropriate cut-off value/concentration limit as shown in Table A.5.1 below for Category 1 and 2 respectively. 
TABLE A.5.1—C UT-OFFVALUES /CONCENTRATION LIMITS OF INGREDIENTS OF A MIXTURE CLASSIFIED AS GERM CELL 
MUTAGENS THATWOULD TRIGGER CLASSIFICATION OF THE MIXTURE  
Ingredient classified as Cut-off/concentration limits 
triggering classification of a 
mixture as: 
Category 1 
mutagen Category 2 
mutagen 
Category 1A/B mutagen .......................................................................................................... ................................ ≥0.1% ........................
Category 2 mutagen ............................................................................................................. ................................... ........................ ≥1.0% 
Note: The cut-off values/concentration limits in the table above apply to solids and liquids (w/w units) as well as gases (v/v units) . 
A.5.3.2 Classification of Mixtures When Data Are Available for the Mixture Itself 
The classification may be modified on a 
case-by-case basis based on the available test 
data for the mixture as a whole. In such cases, the test results for the mixture as a whole must be shown to be conclusive taking into account dose and other factors such as duration, observations and analysis (e.g., statistical analysis, test sensitivity) of germ cell mutagenicity test systems. 
A.5.3.3 Classification of Mixtures When 
Data Are Not Available for the Complete Mixture: Bridging Principles 
A.5.3.3.1 Where the mixture itself has not 
been tested to determine its germ cell 
mutagenicity hazard, but there are sufficient data on both the individual ingredients and similar tested mixtures to adequately characterize the hazards of the mixture, these data will be used in accordance with the following bridging principles as found in paragraph A.0.5 of this Appendix: Dilution, Batching, and Substantially similar mixtures. 
A.5.4 Examples of Scientifically Validated 
Test Methods 
A.5.4.1 Examples of in vivo heritable 
germ cell mutagenicity tests are: 
(a) Rodent dominant lethal mutation test 
(OECD 478) 
(b) Mouse heritable translocation assay 
(OECD 485) (c) Mouse specific locus test 
A.5.4.2 Examples of in vivo somatic cell 
mutagenicity tests are: 
(a) Mammalian bone marrow chromosome 
aberration test (OECD 475) 
(b) Mammalian erythrocyte micronucleus 
test (OECD 474) 
A.5.4.3 Examples of mutagenicity/ 
genotoxicity tests in germ cells are: 
(a) Mutagenicity tests: (i) Mammalian spermatogonial 
chromosome aberration test (OECD 483) 
(ii) Spermatid micronucleus assay (b) Genotoxicity tests: (i) Sister chromatid exchange analysis in 
spermatogonia 
(ii) Unscheduled DNA synthesis test (UDS) 
in testicular cells 
A.5.4.4 Examples of genotoxicity tests in 
somatic cells are: 
(a) Liver Unscheduled DNA Synthesis 
(UDS) in vivo (OECD 486) 
(b) Mammalian bone marrow Sister 
Chromatid Exchanges (SCE) 
A.5.4.5 Examples of in vitro mutagenicity 
tests are: 
(a) In vitro mammalian chromosome 
aberration test (OECD 473) 
(b) In vitro mammalian cell gene mutation 
test (OECD 476) 
(c) Bacterial reverse mutation tests (OECD 
471) A.5.4.6 As new, scientifically validated 
tests arise, these may also be used in the total 
weight of evidence to be considered. 
A.6 Carcinogenicity A.6.1 Definitions 
Carcinogenicity refers to the induction of 
cancer or an increase in the incidence of 
cancer occurring after exposure to a substance or mixture. Substances and mixtures which have induced benign and malignant tumors in well-performed experimental studies on animals are considered also to be presumed or suspected 
human carcinogens unless there is strong evidence that the mechanism of tumor formation is not relevant for humans. 
Classification of a substance or mixture as 
posing a carcinogenic hazard is based on its inherent properties and does not provide information on the level of the human cancer risk which the use of the substance or mixture may represent. 
A.6.2 Classification Criteria for Substances
6 
A.6.2.1 For the purpose of classification 
for carcinogenicity, substances are allocated 
to one of two categories based on strength of evidence and additional weight of evidence considerations. In certain instances, route- specific classification may be warranted. 
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7It should be noted that the classification criteria 
for health hazards usually include a tiered scheme 
in which test data available on the complete mixture are considered as the first tier i the 
evaluation, followed by the applicable bridging principles, and lastly, cut-off values/concentration 
limit or addivity. However, this approach is not used for Carcinogenicity. These criteria for Carcinogenicity consider the cut-off values/ 
concentration limits as the primary tier and allow the classification to be modified only on a case-by- 
case evaluation based on available test data for the mixture as a whole. Figure A.6.1—Hazard Categories for 
Carcinogens 
CATEGORY 1: Known or presumed human 
carcinogens 
The placing of a substance in Category 1 
is done on the basis of epidemiological 
and/or animal data. An individual substance may be further distinguished: 
Category 1A: Known to have carcinogenic 
potential for humans; the placing of a substance is largely based on human evidence. 
Category 1B: Presumed to have carcinogenic 
potential for humans; the placing of a substance is largely based on animal evidence. 
Based on strength of evidence together 
with additional considerations, such 
evidence may be derived from human studies that establish a causal relationship between human exposure to a substance and the development of cancer (known human carcinogen). Alternatively, evidence may be derived from animal experiments for which there is sufficient evidence to demonstrate animal carcinogenicity (presumed human carcinogen). In addition, on a case by case basis, scientific judgement may warrant a decision of presumed human carcinogenicity derived from studies showing limited evidence of carcinogenicity in humans together with limited evidence of carcinogenicity in experimental animals. 
Classification: Category 1 (A and B) 
Carcinogen 
CATEGORY 2: Suspected human carcinogens 
The placing of a substance in Category 2 
is done on the basis of evidence obtained from human and/or animal studies, but which is not sufficiently convincing to place the substance in Category 1. Based on strength of evidence together with additional considerations, such evidence may be from either limited evidence of carcinogenicity in human studies or from limited evidence of carcinogenicity in animal studies. 
Classification: Category 2 Carcinogen 
A.6.2.2 Classification as a carcinogen is 
made on the basis of evidence from reliable 
and acceptable methods, and is intended to be used for substances which have an intrinsic property to produce such toxic effects. The evaluations are to be based on all existing data, peer-reviewed published studies and additional data accepted by 
regulatory agencies. 
A.6.2.3 Carcinogen classification is a one- 
step, criterion-based process that involves two interrelated determinations: evaluations of strength of evidence and consideration of all other relevant information to place substances with human cancer potential into hazard categories. 
A.6.2.4 Strength of evidence involves the 
enumeration of tumors in human and animal studies and determination of their level of statistical significance. Sufficient human evidence demonstrates causality between human exposure and the development of cancer, whereas sufficient evidence in animals shows a causal relationship between the agent and an increased incidence of tumors. Limited evidence in humans is demonstrated by a positive association between exposure and cancer, but a causal relationship cannot be stated. Limited evidence in animals is provided when data suggest a carcinogenic effect, but are less than sufficient. (Guidance on consideration 
of important factors in the classification of carcinogenicity and a more detailed description of the terms ‘‘limited’’ and ‘‘sufficient’’ have been developed by the International Agency for Research on Cancer (IARC) and are provided in non-mandatory appendix F of this section.) 
A.6.2.5 Weight of evidence: Beyond the 
determination of the strength of evidence for carcinogenicity, a number of other factors should be considered that influence the overall likelihood that an agent may pose a carcinogenic hazard in humans. The full list of factors that influence this determination is very lengthy, but some of the important ones are considered here. 
A.6.2.5.1 These factors can be viewed as 
either increasing or decreasing the level of concern for human carcinogenicity. The relative emphasis accorded to each factor depends upon the amount and coherence of evidence bearing on each. Generally, there is a requirement for more complete information to decrease than to increase the level of concern. Additional considerations should be used in evaluating the tumor findings and the other factors in a case-by-case manner. 
A.6.2.5.2 Some important factors which 
may be taken into consideration, when assessing the overall level of concern are: 
(a) Tumor type and background incidence; (b) Multisite responses; (c) Progression of lesions to malignancy; (d) Reduced tumor latency; 
Additional factors which may increase or 
decrease the level of concern include: 
(e) Whether responses are in single or both 
sexes; 
(f) Whether responses are in a single 
species or several species; 
(g) Structural similarity or not to a 
substance(s) for which there is good evidence 
of carcinogenicity; 
(h) Routes of exposure; (i) Comparison of absorption, distribution, 
metabolism and excretion between test animals and humans; 
(j) The possibility of a confounding effect 
of excessive toxicity at test doses; and, 
(k) Mode of action and its relevance for 
humans, such as mutagenicity, cytotoxicity with growth stimulation, mitogenesis, immunosuppression. 
Mutagenicity: It is recognized that genetic 
events are central in the overall process of cancer development. Therefore, evidence of mutagenic activity in vivo may indicate that a substance has a potential for carcinogenic effects. 
A.6.2.5.3 A substance that has not been 
tested for carcinogenicity may in certain instances be classified in Category 1A, Category 1B, or Category 2 based on tumor data from a structural analogue together with substantial support from consideration of other important factors such as formation of common significant metabolites, e.g., for 
benzidine congener dyes. 
A.6.2.5.4 The classification should also 
take into consideration whether or not the substance is absorbed by a given route(s); or whether there are only local tumors at the site of administration for the tested route(s), and adequate testing by other major route(s) show lack of carcinogenicity. 
A.6.2.5.5 It is important that whatever is 
known of the physico-chemical, toxicokinetic and toxicodynamic properties of the substances, as well as any available relevant information on chemical analogues, i.e., 
structure activity relationship, is taken into consideration when undertaking classification. 
A.6.3 Classification Criteria for Mixtures
7 
A.6.3.1 The mixture shall be classified as 
a carcinogen when at least one ingredient has 
been classified as a Category 1 or Category 2 carcinogen and is present at or above the appropriate cut-off value/concentration limit as shown in Table A.6.1. 
TABLE A.6.1—C UT-OFFVALUES /CONCENTRATION LIMITS OF INGREDIENTS OF A MIXTURE CLASSIFIED AS CARCINOGEN  
THATWOULD TRIGGER CLASSIFICATION OF THE MIXTURE  
Ingredient classified as Category 1 
carcinogen Category 2 
carcinogen 
Category 1 carcinogen .......................................................................................................... ............................ ≥0.1% ..............................
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8See Non-mandatory appendix f of this section 
for further guidance regarding hazard classification 
for carcinogenicity and how to relate carcinogenicity classification information from IARC and NTP to GHS. TABLE A.6.1—C UT-OFFVALUES /CONCENTRATION LIMITS OF INGREDIENTS OF A MIXTURE CLASSIFIED AS CARCINOGEN  
THATWOULD TRIGGER CLASSIFICATION OF THE MIXTURE —Continued 
Ingredient classified as Category 1 
carcinogen Category 2 
carcinogen 
Category 2 carcinogen .......................................................................................................... ............................ ........................ ≥0.1% (note 1) 
Note: If a Category 2 carcinogen ingredient is present in the mixture at a concentration between 0.1% and 1%, information is required on the 
SDS for a product. However, a label warning is optional. If a Category 2 carcinogen ingredient is present in the mixture at a concentration of 
≥1%, both an SDS and a label is required and the information must be included on each. 
A.6.3.2 Classification of mixtures when 
data are available for the complete mixture 
A mixture may be classified based on the 
available test data for the mixture as a whole. 
In such cases, the test results for the mixture as a whole must be shown to be conclusive taking into account dose and other factors such as duration, observations and analysis (e.g., statistical analysis, test sensitivity) of 
carcinogenicity test systems. 
A.6.3.3 Classification of mixtures when 
data are not available for the complete mixture: bridging principles 
Where the mixture itself has not been 
tested to determine its carcinogenic hazard, but there are sufficient data on both the 
individual ingredients and similar tested mixtures to adequately characterize the hazards of the mixture, these data will be used in accordance with the following bridging principles as found in paragraph A.0.5 of this Appendix: Dilution; Batching; and Substantially similar mixtures. 
A.6.4 Classification of Carcinogenicity
8 
A.6.4.1 Chemical manufacturers, 
importers and employers evaluating 
chemicals may treat the following sources as establishing that a substance is a carcinogen or potential carcinogen for hazard communication purposes in lieu of applying the criteria described herein: 
A.6.4.1.1 National Toxicology Program 
(NTP), ‘‘Report on Carcinogens’’ (latest edition); 
A.6.4.1.2 International Agency for 
Research on Cancer (IARC) ‘‘Monographs on the Evaluation of Carcinogenic Risks to Humans’’ (latest editions) 
A.6.4.2 Where OSHA has included cancer 
as a health hazard to be considered by classifiers for a chemical covered by 29 CFR part 1910, subpart Z, chemical manufacturers, importers, and employers shall classify the chemical as a carcinogen. 
A.7 Reproductive Toxicity A.7.1 Definitions and General 
Considerations 
A.7.1.1 Reproductive toxicity refers to 
adverse effects on sexual function and 
fertility in adult males and females, as well as developmental toxicity in the offspring, occurring after exposure to a substance or mixture. Some reproductive toxic effects cannot be clearly assigned to either impairment of sexual function and fertility or to developmental toxicity. Nonetheless, substances and mixtures with these effects 
shall be classified as reproductive toxicants. For classification purposes, the known induction of genetically based inheritable effects in the offspring is addressed in Germ cell mutagenicity (See A.5). 
A.7.1.2 Adverse effects on sexual 
function and fertility means any effect of chemicals that interferes with reproductive ability or sexual capacity. This includes, but is not limited to, alterations to the female and male reproductive system, adverse effects on onset of puberty, gamete production and transport, reproductive cycle normality, sexual behavior, fertility, parturition, pregnancy outcomes, premature reproductive senescence, or modifications in other functions that are dependent on the integrity of the reproductive systems. 
A.7.1.3 Adverse effects on development 
of the offspring means any effect of chemicals which interferes with normal development of the conceptus either before or after birth, which is induced during pregnancy or results from parental exposure. These effects can be manifested at any point in the life span of the organism. The major manifestations of developmental toxicity include death of the developing organism, structural abnormality, altered growth and functional deficiency. 
A.7.1.4 Adverse effects on or via lactation 
are also included in reproductive toxicity, but for classification purposes, such effects are treated separately (See A.7.2.1). 
A.7.2 Classification Criteria for Substances 
A.7.2.1 For the purpose of classification 
for reproductive toxicity, substances shall be classified in one of two categories in accordance with Figure A.7.1(a). Effects on sexual function and fertility, and on development, shall be considered. In addition, effects on or via lactation shall be classified in a separate hazard category in accordance with Figure A.7.1(b). 
Figure A.7.1(a)—Hazard Categories for 
Reproductive Toxicants 
CATEGORY 1: Known or presumed human 
reproductive toxicant 
This category includes substances which 
are known to have produced an adverse 
effect on sexual function and fertility or on development in humans or for which there is evidence from animal studies, possibly supplemented with other information, to provide a strong presumption that the substance has the capacity to interfere with reproduction in humans. For regulatory purposes, a substance can be further distinguished on the basis of whether the evidence for classification is primarily from human data (Category 1A) or from animal data 
(Category 1B). 
CATEGORY 1A: Known human reproductive 
toxicant 
The placing of the substance in this 
category is largely based on evidence from humans. 
CATEGORY 1B: Presumed human 
reproductive toxicant 
The placing of the substance in this 
category is largely based on evidence from experimental animals. Data from animal studies should provide clear evidence of an adverse effect on sexual function and fertility or on development in the absence of other toxic effects, or if occurring together with other toxic effects the adverse effect on reproduction is considered not to be a secondary non- specific consequence of other toxic effects. However, when there is mechanistic information that raises doubt about the relevance of the effect for humans, classification in Category 2 may be more appropriate. 
CATEGORY 2: Suspected human 
reproductive toxicant 
This category includes substances for 
which there is some evidence from humans or experimental animals, possibly supplemented with other information, of an adverse effect on sexual function and fertility, or on development, in the absence of other toxic effects, or if occurring together with other toxic effects the adverse effect on reproduction is considered not to be a 
secondary non-specific consequence of the other toxic effects, and where the evidence is not sufficiently convincing to place the substance in Category 1. For instance, deficiencies in the study may make the quality of evidence less convincing, and in view of this Category 2 could be the more appropriate classification. 
Figure A.7.1(b)—Hazard Category for Effects on or Via Lactation 
EFFECTS ON OR VIA LACTATION 
Effects on or via lactation are allocated to a 
separate category. It is appreciated that for many substances there is no information on the potential to cause adverse effects on the offspring via lactation. However, substances which are absorbed by women and have been shown to interfere with lactation, or which may be present (including metabolites) in breast milk in amounts sufficient to cause concern for the health of a breastfed child, should be classified to indicate this property. 
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Classification for effects via lactation shall be 
assigned on the basis of: 
(a) absorption, metabolism, distribution 
and excretion studies that would 
indicate the likelihood the substance would be present in potentially toxic levels in breast milk; and/or 
(b) results of one or two generation studies 
in animals which provide clear evidence of adverse effect in the offspring due to transfer in the milk or adverse effect on the quality of the milk; and/or 
(c) human evidence indicating a hazard to 
babies during the lactation period. 
A.7.2.2 Basis of Classification 
A.7.2.2.1 Classification is made on the 
basis of the criteria, outlined above, an assessment of the total weight of evidence, and the use of expert judgment. Classification as a reproductive toxicant is intended to be used for substances which have an intrinsic, specific property to produce an adverse effect on reproduction and substances should not be so classified if such an effect is produced solely as a non-specific secondary consequence of other toxic effects. 
A.7.2.2.2 In the evaluation of toxic effects 
on the developing offspring, it is important to consider the possible influence of maternal toxicity. 
A.7.2.2.3 For human evidence to provide 
the primary basis for a Category 1A classification there must be reliable evidence of an adverse effect on reproduction in humans. Evidence used for classification shall be from well conducted epidemiological studies, if available, which include the use of appropriate controls, balanced assessment, and due consideration of bias or confounding factors. Less rigorous data from studies in humans may be sufficient for a Category 1A classification if supplemented with adequate data from studies in experimental animals, but classification in Category 1B may also be considered. 
A.7.2.3 Weight of Evidence 
A.7.2.3.1 Classification as a reproductive 
toxicant is made on the basis of an 
assessment of the total weight of evidence using expert judgment. This means that all available information that bears on the determination of reproductive toxicity is considered together. Included is information such as epidemiological studies and case reports in humans and specific reproduction studies along with sub-chronic, chronic and special study results in animals that provide relevant information regarding toxicity to reproductive and related endocrine organs. Evaluation of substances chemically related to the material under study may also be included, particularly when information on the material is scarce. The weight given to the available evidence will be influenced by factors such as the quality of the studies, consistency of results, nature and severity of effects, level of statistical significance for intergroup differences, number of endpoints affected, relevance of route of administration to humans and freedom from bias. Both 
positive and negative results are considered together in a weight of evidence determination. However, a single, positive study performed according to good scientific principles and with statistically or 
biologically significant positive results may justify classification (See also A.7.2.2.3). 
A.7.2.3.2 Toxicokinetic studies in 
animals and humans, site of action and mechanism or mode of action study results may provide relevant information, which could reduce or increase concerns about the hazard to human health. If it is conclusively demonstrated that the clearly identified mechanism or mode of action has no relevance for humans or when the toxicokinetic differences are so marked that it is certain that the hazardous property will not be expressed in humans then a chemical 
which produces an adverse effect on reproduction in experimental animals should not be classified. 
A.7.2.3.3 In some reproductive toxicity 
studies in experimental animals the only effects recorded may be considered of low or minimal toxicological significance and classification may not necessarily be the outcome. These effects include, for example, small changes in semen parameters or in the incidence of spontaneous defects in the fetus, small changes in the proportions of common fetal variants such as are observed in skeletal examinations, or in fetal weights, or small differences in postnatal developmental assessments. 
A.7.2.3.4 Data from animal studies shall 
provide sufficient evidence of specific reproductive toxicity in the absence of other systemic toxic effects. However, if developmental toxicity occurs together with other toxic effects in the dam (mother), the potential influence of the generalized adverse effects should be assessed to the extent possible. The preferred approach is to consider adverse effects in the embryo/fetus first, and then evaluate maternal toxicity, along with any other factors which are likely to have influenced these effects, as part of the weight of evidence. In general, developmental effects that are observed at maternally toxic doses should not be automatically discounted. Discounting developmental effects that are observed at maternally toxic doses can only be done on a case-by-case basis when a causal relationship is established or refuted. 
A.7.2.3.5 If appropriate information is 
available it is important to try to determine whether developmental toxicity is due to a specific maternally mediated mechanism or to a non-specific secondary mechanism, like maternal stress and the disruption of homeostasis. Generally, the presence of maternal toxicity should not be used to negate findings of embryo/fetal effects, unless it can be clearly demonstrated that the effects are secondary non-specific effects. This is especially the case when the effects in the offspring are significant, e.g., irreversible 
effects such as structural malformations. In some situations it is reasonable to assume that reproductive toxicity is due to a secondary consequence of maternal toxicity and discount the effects, for example if the chemical is so toxic that dams fail to thrive and there is severe inanition; they are incapable of nursing pups; or they are prostrate or dying. A.7.2.4 Maternal Toxicity 
A.7.2.4.1 Development of the offspring 
throughout gestation and during the early 
postnatal stages can be influenced by toxic effects in the mother either through non- specific mechanisms related to stress and the disruption of maternal homeostasis, or by specific maternally-mediated mechanisms. So, in the interpretation of the developmental outcome to decide classification for developmental effects it is important to consider the possible influence of maternal toxicity. This is a complex issue because of uncertainties surrounding the relationship between maternal toxicity and developmental outcome. Expert judgment and a weight of evidence approach, using all available studies, shall be used to determine the degree of influence to be attributed to maternal toxicity when interpreting the criteria for classification for developmental effects. The adverse effects in the embryo/ fetus shall be first considered, and then maternal toxicity, along with any other factors which are likely to have influenced these effects, as weight of evidence, to help reach a conclusion about classification. 
A.7.2.4.2 Based on pragmatic observation, 
it is believed that maternal toxicity may, depending on severity, influence development via non-specific secondary mechanisms, producing effects such as depressed fetal weight, retarded ossification, and possibly resorptions and certain malformations in some strains of certain species. However, the limited numbers of studies which have investigated the relationship between developmental effects and general maternal toxicity have failed to demonstrate a consistent, reproducible relationship across species. Developmental effects which occur even in the presence of maternal toxicity are considered to be evidence of developmental toxicity, unless it can be unequivocally demonstrated on a case by case basis that the developmental effects are secondary to maternal toxicity. Moreover, classification shall be considered where there is a significant toxic effect in the offspring, e.g., irreversible effects such as structural 
malformations, embryo/fetal lethality, or 
significant post-natal functional deficiencies. 
A.7.2.4.3 Classification shall not 
automatically be discounted for chemicals that produce developmental toxicity only in association with maternal toxicity, even if a specific maternally-mediated mechanism has been demonstrated. In such a case, classification in Category 2 may be considered more appropriate than Category 1. However, when a chemical is so toxic that maternal death or severe inanition results, or the dams (mothers) are prostrate and incapable of nursing the pups, it is reasonable to assume that developmental toxicity is produced solely as a secondary consequence of maternal toxicity and discount the developmental effects. Classification is not necessarily the outcome in the case of minor developmental changes, e.g., a small reduction in fetal/pup body 
weight or retardation of ossification when seen in association with maternal toxicity. 
A.7.2.4.4 Some of the endpoints used to 
assess maternal toxicity are provided below. Data on these endpoints, if available, shall be 
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9It should be noted that the classification criteria 
for health hazards usually include a tiered scheme 
in which test data available on the complete mixture are considered as the first tier in the evaluation, followed by the applicable bridging principles, and lastly, cut-off values/concentration limits or additivity. However, this approach is not used for Reproductive Toxicity. These criteria for Reproductive Toxicity consider the cut-off values/ concentration limits as the primary tier and allow the classification to be modified only on a case-by- case evaluation based on available test data for the mixture as a whole. evaluated in light of their statistical or 
biological significance and dose-response relationship. 
(a) Maternal mortality: An increased 
incidence of mortality among the treated dams over the controls shall be considered evidence of maternal toxicity if the increase occurs in a dose-related manner and can be attributed to the systemic toxicity of the test material. Maternal mortality greater than 10% is considered excessive and the data for 
that dose level shall not normally be considered to need further evaluation. 
(b) Mating index (Number of animals with 
seminal plugs or sperm/Number of mated × 
100) 
(c) Fertility index (Number of animals with 
implants/Number of matings × 100) 
(d) Gestation length (If allowed to deliver) (e) Body weight and body weight change: 
Consideration of the maternal body weight change and/or adjusted (corrected) maternal body weight shall be included in the evaluation of maternal toxicity whenever such data are available. The calculation of an adjusted (corrected) mean maternal body weight change, which is the difference between the initial and terminal body weight minus the gravid uterine weight (or alternatively, the sum of the weights of the fetuses), may indicate whether the effect is maternal or intrauterine. In rabbits, the body weight gain may not be a useful indicator of maternal toxicity because of normal fluctuations in body weight during pregnancy. 
(f) Food and water consumption (if 
relevant): The observation of a significant decrease in the average food or water consumption in treated dams (mothers) compared to the control group may be useful in evaluating maternal toxicity, particularly when the test material is administered in the diet or drinking water. Changes in food or water consumption must be evaluated in conjunction with maternal body weights when determining if the effects noted are reflective of maternal toxicity or more simply, unpalatability of the test material in feed or water. 
(g) Clinical evaluations (including clinical 
signs, markers, and hematology and clinical chemistry studies): The observation of increased incidence of significant clinical signs of toxicity in treated dams (mothers) relative to the control group is useful in evaluating maternal toxicity. If this is to be used as the basis for the assessment of maternal toxicity, the types, incidence, degree and duration of clinical signs shall be reported in the study. Clinical signs of maternal intoxication include, but are not limited to: coma, prostration, hyperactivity, loss of righting reflex, ataxia, or labored breathing. 
(h) Post-mortem data: Increased incidence 
and/or severity of post-mortem findings may be indicative of maternal toxicity. This can include gross or microscopic pathological findings or organ weight data, including 
absolute organ weight, organ-to-body weight ratio, or organ-to-brain weight ratio. When 
supported by findings of adverse histopathological effects in the affected organ(s), the observation of a significant change in the average weight of suspected target organ(s) of treated dams (mothers), compared to those in the control group, may be considered evidence of maternal toxicity. 
A.7.2.5 Animal and Experimental Data 
A.7.2.5.1 A number of scientifically 
validated test methods are available, 
including methods for developmental toxicity testing (e.g., OECD Test Guideline 
414, ICH Guideline S5A, 1993), methods for peri- and post-natal toxicity testing (e.g., ICH 
S5B, 1995), and methods for one or two- generation toxicity testing (e.g., OECD Test 
Guidelines 415, 416, 443). 
A.7.2.5.2 Results obtained from screening 
tests (e.g., OECD Guidelines 421— 
Reproduction/Developmental Toxicity Screening Test, and 422—Combined Repeated Dose Toxicity Study with Reproduction/Development Toxicity Screening Test) can also be used to justify classification, although the quality of this evidence is less reliable than that obtained through full studies. 
A.7.2.5.3 Adverse effects or changes, seen 
in short- or long-term repeated dose toxicity studies, which are judged likely to impair reproductive function and which occur in the absence of significant generalized toxicity, may be used as a basis for classification, e.g., histopathological changes in the gonads. 
A.7.2.5.4 Evidence from in vitro assays, 
or non-mammalian tests, and from analogous substances using structure-activity relationship (SAR), can contribute to the procedure for classification. In all cases of this nature, expert judgment must be used to assess the adequacy of the data. Inadequate data shall not be used as a primary support for classification. 
A.7.2.5.5 It is preferable that animal 
studies are conducted using appropriate routes of administration which relate to the potential route of human exposure. However, in practice reproductive toxicity studies are commonly conducted using the oral route, and such studies will normally be suitable for evaluating the hazardous properties of the substance with respect to reproductive toxicity. However, if it can be conclusively demonstrated that the clearly identified mechanism or mode of action has no relevance for humans or when the toxicokinetic differences are so marked that it is certain that the hazardous property will not be expressed in humans then a substance which produces an adverse effect on reproduction in experimental animals should not be classified. 
A.7.2.5.6 Studies involving routes of 
administration such as intravenous or intraperitoneal injection, which may result in exposure of the reproductive organs to unrealistically high levels of the test 
substance, or elicit local damage to the reproductive organs, e.g., by irritation, must 
be interpreted with extreme caution and on their own are not normally the basis for classification. 
A.7.2.5.7 There is general agreement 
about the concept of a limit dose, above which the production of an adverse effect may be considered to be outside the criteria 
which lead to classification. Some test guidelines specify a limit dose, other test guidelines qualify the limit dose with a statement that higher doses may be necessary if anticipated human exposure is sufficiently high that an adequate margin of exposure would not be achieved. Also, due to species differences in toxicokinetics, establishing a specific limit dose may not be adequate for situations where humans are more sensitive than the animal model. 
A.7.2.5.8 In principle, adverse effects on 
reproduction seen only at very high dose levels in animal studies (for example doses that induce prostration, severe inappetence, excessive mortality) do not normally lead to classification, unless other information is available, for example, toxicokinetics information indicating that humans may be more susceptible than animals, to suggest that classification is appropriate. 
A.7.2.5.9 However, specification of the 
actual ‘‘limit dose’’ will depend upon the test method that has been employed to provide the test results. 
A.7.3 Classification Criteria for Mixtures
9 
A.7.3.1 Classification of Mixtures When 
Data Are Available for All Ingredients or Only for Some Ingredients of the Mixture 
A.7.3.1.1 The mixture shall be classified 
as a reproductive toxicant when at least one 
ingredient has been classified as a Category 1 or Category 2 reproductive toxicant and is present at or above the appropriate cut-off value/concentration limit specified in Table A.7.1 for Category 1 and 2, respectively. 
A.7.3.1.2 The mixture shall be classified 
for effects on or via lactation when at least one ingredient has been classified for effects on or via lactation and is present at or above the appropriate cut-off value/concentration limit specified in Table A.7.1 for the additional category for effects on or via lactation. 
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TABLE A.7.1—C UT-OFFVALUES /CONCENTRATION LIMITS OF INGREDIENTS OF A MIXTURE CLASSIFIED AS REPRODUCTIVE  
TOXICANTS OR FOR EFFECTS ON OR VIALACTATION THATTRIGGER CLASSIFICATION OF THE MIXTURE  
Ingredient classified as Cut-off values/concentration limits 
triggering classification of a mixture as 
Category 1 
reproductive 
toxicant Category 2 
reproductive 
toxicant Additional 
category for 
effects on or 
via lactation 
Category 1 reproductive toxicant ............................................................................................... .. ≥0.01% ........................ ........................
Category 2 reproductive toxicant ............................................................................................... .. ........................ ≥0.01% ........................
Additional category for effects on or via lactation ....................................................................... ..... ................... ........................ ≥0.01% 
A.7.3.2 Classification of Mixtures When 
Data Are Available for the Complete Mixture 
Available test data for the mixture as a 
whole may be used for classification on a case-by-case basis. In such cases, the test results for the mixture as a whole must be shown to be conclusive taking into account dose and other factors such as duration, observations and analysis (e.g., statistical 
analysis, test sensitivity) of reproduction test systems. 
A.7.3.3 Classification of Mixtures When 
Data Are Not Available for the Complete Mixture: Bridging Principles 
A.7.3.1.1 Where the mixture itself has not 
been tested to determine its reproductive toxicity, but there are sufficient data on both the individual ingredients and similar tested mixtures to adequately characterize the hazards of the mixture, these data shall be used in accordance with the following bridging principles as found in paragraph A.0.5 of this Appendix: Dilution, Batching, and Substantially similar mixtures. 
A.8 Specific Target Organ Toxicity Single 
Exposure 
A.8.1 Definitions and General 
Considerations 
A.8.1.1 Specific target organ toxicity— 
single exposure, (STOT–SE) refers to specific, non-lethal toxic effects on target organs occurring after a single exposure to a substance or mixture. All significant health effects that can impair function, both reversible and irreversible, immediate and/or delayed and not specifically addressed in A.1 to A.7 and A.10 of this Appendix are included. Specific target organ toxicity following repeated exposure is classified in accordance with SPECIFIC TARGET ORGAN TOXICITY—REPEATED EXPOSURE (A.9 of this Appendix) and is therefore not included here. 
A.8.1.2 Classification identifies the 
chemical as being a specific target organ toxicant and, as such, it presents a potential for adverse health effects in people who are exposed to it. 
A.8.1.3 The adverse health effects 
produced by a single exposure include consistent and identifiable toxic effects in humans; or, in experimental animals, toxicologically significant changes which have affected the function or morphology of a tissue/organ, or have produced serious changes to the biochemistry or hematology of the organism, and these changes are relevant for human health. Human data is the primary 
source of evidence for this hazard class. 
A.8.1.4 Assessment shall take into 
consideration not only significant changes in a single organ or biological system but also generalized changes of a less severe nature involving several organs. 
A.8.1.5 Specific target organ toxicity can 
occur by any route that is relevant for humans, i.e., principally oral, dermal or 
inhalation. 
A.8.1.6 The classification criteria for 
specific target organ toxicity—single exposure are organized as criteria for substances Categories 1 and 2 ( See A.8.2.1), 
criteria for substances Category 3 ( See 
A.8.2.2) and criteria for mixtures ( See A.8.3). 
See also Figure A.8.1. 
A.8.2 Classification Criteria for Substances 
A.8.2.1 Substances of Category 1 and 
Category 2 
A.8.2.1.1 Substances shall be classified 
for immediate or delayed effects separately, 
by the use of expert judgment on the basis of the weight of all evidence available, including the use of recommended guidance values (See A.8.2.1.9). Substances shall then 
be classified in Category 1 or 2, depending upon the nature and severity of the effect(s) observed, in accordance with Figure A.8.1. 
Figure A.8.1—Hazard Categories for Specific 
Target Organ Toxicity Following Single Exposure 
CATEGORY 1: Substances that have 
produced significant toxicity in humans, 
or that, on the basis of evidence from studies in experimental animals can be presumed to have the potential to produce significant toxicity in humans following single exposure 
Placing a substance in Category 1 is done 
on the basis of: 
(a) reliable and good quality evidence from 
human cases or epidemiological studies; or 
(b) observations from appropriate studies 
in experimental animals in which significant and/or severe toxic effects of relevance to human health were produced at generally low exposure concentrations. Guidance dose/ concentration values are provided below (see 3.8.2.1.9) to be used as part of weight-of-evidence evaluation. 
CATEGORY 2: Substances that, on the basis 
of evidence from studies in experimental animals can be presumed to have the potential to be harmful to human health 
following single exposure 
Placing a substance in Category 2 is done 
on the basis of observations from appropriate studies in experimental animals in which significant toxic effects, of relevance to human health, were produced at generally moderate exposure concentrations. Guidance dose/ concentration values are provided below (see 3.8.2.1.9) in order to help in classification. 
In exceptional cases, human evidence can 
also be used to place a substance in Category 2 (see 3.8.2.1.9). 
CATEGORY 3: Transient target organ effects 
There are target organ effects for which a 
substance/mixture may not meet the criteria to be classified in Categories 1 or 2 indicated above. These are effects which adversely alter human function for a short duration after exposure and from which humans may recover in a reasonable period without leaving significant alteration of structure or function. This category only includes narcotic effects and respiratory tract irritation. Substances/mixtures may be classified specifically for these effects as discussed in 3.8.2.2. 
Note: For these categories the specific 
target organ/system that has been primarily affected by the classified substance may be identified, or the substance may be identified as a general toxicant. Attempts should be made to determine the primary target organ/ system of toxicity and classify for that purpose, e.g., hepatotoxicants, neurotoxicants. One should carefully evaluate the data and, where possible, not include secondary effects, e.g., a hepatotoxicant can produce secondary effects in the nervous or gastro-intestinal systems. 
A.8.2.1.2 The relevant route(s) of 
exposure by which the classified substance produces damage shall be identified. 
A.8.2.1.3 Classification is determined by 
expert judgment, on the basis of the weight of all evidence available including the guidance presented below. 
A.8.2.1.4 Weight of evidence of all 
available data, including human incidents, epidemiology, and studies conducted in 
experimental animals is used to substantiate specific target organ toxic effects that merit classification. 
A.8.2.1.5 The information required to 
evaluate specific target organ toxicity comes either from single exposure in humans ( e.g., 
exposure at home, in the workplace or 
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environmentally), or from studies conducted 
in experimental animals. The standard animal studies in rats or mice that provide this information are acute toxicity studies which can include clinical observations and detailed macroscopic and microscopic examination to enable the toxic effects on target tissues/organs to be identified. Results of acute toxicity studies conducted in other species may also provide relevant information. 
A.8.2.1.6 In exceptional cases, based on 
expert judgment, it may be appropriate to place certain substances with human evidence of target organ toxicity in Category 2: (a) when the weight of human evidence is not sufficiently convincing to warrant Category 1 classification, and/or (b) based on the nature and severity of effects. Dose/ concentration levels in humans shall not be considered in the classification and any available evidence from animal studies shall be consistent with the Category 2 classification. In other words, if there are also animal data available on the substance that warrant Category 1 classification, the chemical shall be classified as Category 1. 
A.8.2.1.7 Effects Considered To Support 
Classification for Category 1 and 2 
A.8.2.1.7.1 Classification is supported by 
evidence associating single exposure to the substance with a consistent and identifiable toxic effect. 
A.8.2.1.7.2 Evidence from human 
experience/incidents is usually restricted to reports of adverse health consequences, often with uncertainty about exposure conditions, and may not provide the scientific detail that can be obtained from well-conducted studies in experimental animals. 
A.8.2.1.7.3 Evidence from appropriate 
studies in experimental animals can furnish much more detail, in the form of clinical observations, and macroscopic and microscopic pathological examination and this can often reveal hazards that may not be 
life-threatening but could indicate functional impairment. Consequently, all available evidence, and relevance to human health, must be taken into consideration in the classification process. Relevant toxic effects in humans and/or animals include, but are not limited to: 
(a) Morbidity resulting from single 
exposure; 
(b) Significant functional changes, more 
than transient in nature, in the respiratory system, central or peripheral nervous systems, other organs or other organ systems, including signs of central nervous system depression and effects on special senses ( e.g., 
sight, hearing and sense of smell); 
(c) Any consistent and significant adverse 
change in clinical biochemistry, hematology, or urinalysis parameters; 
(d) Significant organ damage that may be 
noted at necropsy and/or subsequently seen or confirmed at microscopic examination; 
(e) Multi-focal or diffuse necrosis, fibrosis 
or granuloma formation in vital organs with regenerative capacity; 
(f) Morphological changes that are 
potentially reversible but provide clear 
evidence of marked organ dysfunction; and, 
(g) Evidence of appreciable cell death 
(including cell degeneration and reduced cell number) in vital organs incapable of regeneration. 
A.8.2.1.8 Effects Considered Not To 
Support Classification for Category 1 and 2 
Effects may be seen in humans and/or 
animals that do not justify classification. Such effects include, but are not limited to: 
(a) Clinical observations or small changes 
in bodyweight gain, food consumption or water intake that may have some toxicological importance but that do not, by themselves, indicate ‘‘significant’’ toxicity; 
(b) Small changes in clinical biochemistry, 
hematology or urinalysis parameters and/or transient effects, when such changes or 
effects are of doubtful or of minimal toxicological importance; 
(c) Changes in organ weights with no 
evidence of organ dysfunction; 
(d) Adaptive responses that are not 
considered toxicologically relevant; and, 
(e) Substance-induced species-specific 
mechanisms of toxicity, i.e., demonstrated 
with reasonable certainty to be not relevant for human health, shall not justify classification. 
A.8.2.1.9 Guidance Values To Assist With 
Classification Based on the Results Obtained From Studies Conducted in Experimental Animals for Category 1 and 2 
A.8.2.1.9.1 In order to help reach a 
decision about whether a substance shall be 
classified or not, and to what degree it shall be classified (Category 1 vs. Category 2), dose/concentration ‘‘guidance values’’ are provided for consideration of the dose/ concentration which has been shown to produce significant health effects. The principal argument for proposing such guidance values is that all chemicals are potentially toxic and there has to be a 
reasonable dose/concentration above which a degree of toxic effect is acknowledged. 
A.8.2.1.9.2 Thus, in animal studies, when 
significant toxic effects are observed that indicate classification, consideration of the dose/concentration at which these effects were seen, in relation to the suggested guidance values, provides useful information to help assess the need to classify (since the toxic effects are a consequence of the hazardous property(ies) and also the dose/ concentration). 
A.8.2.1.9.3 The guidance value (C) ranges 
for single-dose exposure which has produced a significant non-lethal toxic effect are those applicable to acute toxicity testing, as indicated in Table A.8.1. 
TABLE A.8.1—G UIDANCE VALUE RANGES FOR SINGLE -DOSEEXPOSURES  
Route of exposure Units Guidance value ranges for: 
Category 1 Category 2 Category 3 
Oral (rat) ............................................. mg/kg body weight ..... C ≤ 300 .......... 2,000 ≥ C > 300 ........ Guidance values do not apply. 
Dermal (rat or rabbit) ......................... mg/kg body weight ..... C ≤ 1,000 ....... 2,000 ≥ C > 1,000.
Inhalation (rat) gas ............................. ppmV/4h ..................... C ≤ 2,500 ....... 20,000 ≥ C > 2,500.
Inhalation (rat) vapor .......................... mg/1/4h ...................... C ≤ 10 ............ 20 ≥ C > 10.
Inhalation (rat) dust/mist/fume ........... mg/l/4h ....................... C ≤ 1.0 ........... 5.0 ≥ C > 1.0.
A.8.2.1.9.4 The guidance values and 
ranges mentioned in Table A.8.1 are intended only for guidance purposes, i.e., to be used 
as part of the weight of evidence approach, and to assist with decisions about classification. They are not intended as strict 
demarcation values. Guidance values are not provided for Category 3 since this classification is primarily based on human data; animal data may be included in the weight of evidence evaluation. 
A.8.2.1.9.5 Thus, it is feasible that a 
specific profile of toxicity occurs at a dose/ concentration below the guidance value, e.g., <2,000 mg/kg body weight by the oral route, however the nature of the effect may result in the decision not to classify. Conversely, a 
specific profile of toxicity may be seen in animal studies occurring at above a guidance value, e.g., ≥2,000 mg/kg body weight by the 
oral route, and in addition there is supplementary information from other sources, e.g., other single dose studies, or 
human case experience, which supports a 
conclusion that, in view of the weight of evidence, classification is the prudent action to take. 
A.8.2.1.10 Other Considerations 
A.8.2.1.10.1 When a substance is 
characterized only by use of animal data the 
classification process includes reference to dose/concentration guidance values as one of 
the elements that contribute to the weight of evidence approach. 
A.8.2.1.10.2 When well-substantiated 
human data are available showing a specific target organ toxic effect that can be reliably 
attributed to single exposure to a substance, the substance shall be classified. Positive human data, regardless of probable dose, predominates over animal data. Thus, if a substance is unclassified because specific target organ toxicity observed was considered not relevant or significant to humans, if subsequent human incident data become available showing a specific target organ toxic effect, the substance shall be classified. 
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A.8.2.1.10.3 A substance that has not 
been tested for specific target organ toxicity 
shall, where appropriate, be classified on the basis of data from a scientifically validated structure activity relationship and expert judgment-based extrapolation from a structural analogue that has previously been classified together with substantial support from consideration of other important factors such as formation of common significant metabolites. 
A.8.2.2 Substances of Category 3 
A.8.2.2.1 Criteria for respiratory tract 
irritation 
The criteria for classifying substances as 
Category 3 for respiratory tract irritation are: 
(a) Respiratory irritant effects 
(characterized by localized redness, edema, 
pruritis and/or pain) that impair function with symptoms such as cough, pain, choking, and breathing difficulties are included. It is recognized that this evaluation is based primarily on human data; 
(b) Subjective human observations 
supported by objective measurements of clear respiratory tract irritation (RTI) (e.g., electrophysiological responses, biomarkers of inflammation in nasal or bronchoalveolar lavage fluids); 
(c) The symptoms observed in humans 
shall also be typical of those that would be produced in the exposed population rather than being an isolated idiosyncratic reaction or response triggered only in individuals with hypersensitive airways. Ambiguous 
reports simply of ‘‘irritation’’ should be excluded as this term is commonly used to describe a wide range of sensations including those such as smell, unpleasant taste, a tickling sensation, and dryness, which are outside the scope of classification for respiratory tract irritation; 
(d) There are currently no scientifically 
validated animal tests that deal specifically with RTI; however, useful information may be obtained from the single and repeated inhalation toxicity tests. For example, animal studies may provide useful information in terms of clinical signs of toxicity (dyspnoea, rhinitis etc.) and histopathology ( e.g., 
hyperemia, edema, minimal inflammation, thickened mucous layer) which are reversible and may be reflective of the characteristic clinical symptoms described above. Such animal studies can be used as part of weight of evidence evaluation; and, 
(e) This special classification will occur 
only when more severe organ effects including the respiratory system are not observed as those effects would require a higher classification. 
A.8.2.2.2 Criteria for Narcotic Effects 
The criteria for classifying substances in 
Category 3 for narcotic effects are: 
(a) Central nervous system depression 
including narcotic effects in humans such as 
drowsiness, narcosis, reduced alertness, loss of reflexes, lack of coordination, and vertigo are included. These effects can also be manifested as severe headache or nausea, and can lead to reduced judgment, dizziness, irritability, fatigue, impaired memory function, deficits in perception and coordination, reaction time, or sleepiness; and, 
(b) Narcotic effects observed in animal 
studies may include lethargy, lack of coordination righting reflex, narcosis, and ataxia. If these effects are not transient in nature, then they shall be considered for classification as Category 1 or 2. 
A.8.3 Classification Criteria for Mixtures 
A.8.3.1 Mixtures are classified using the 
same criteria as for substances, or 
alternatively as described below. As with substances, mixtures may be classified for specific target organ toxicity following single exposure, repeated exposure, or both. 
A.8.3.2 Classification of Mixtures When 
Data Are Available for the Complete Mixture 
When reliable and good quality evidence 
from human experience or appropriate studies in experimental animals, as described 
in the criteria for substances, is available for the mixture, then the mixture shall be classified by weight of evidence evaluation of this data. Care shall be exercised in evaluating data on mixtures, that the dose, duration, observation or analysis, do not render the results inconclusive. 
A.8.3.3 Classification of Mixtures When 
Data Are Not Available for the Complete Mixture: Bridging Principles 
A.8.3.3.1 Where the mixture itself has not 
been tested to determine its specific target 
organ toxicity, but there are sufficient data on both the individual ingredients and similar tested mixtures to adequately characterize the hazards of the mixture, these data shall be used in accordance with the following bridging principles as found in paragraph A.0.5 of this Appendix: Dilution, Batching, Concentration of mixtures, Interpolation within one hazard category, Substantially similar mixtures, or Aerosols. 
A.8.3.4 Classification of Mixtures When 
Data Are Available for All Ingredients or Only for Some Ingredients of the Mixture 
A.8.3.4.1 Where there is no reliable 
evidence or test data for the specific mixture 
itself, and the bridging principles cannot be used to enable classification, then classification of the mixture is based on the classification of the ingredient substances. In this case, the mixture shall be classified as a specific target organ toxicant (specific organ specified), following single exposure, repeated exposure, or both when at least one ingredient has been classified as a Category 1 or Category 2 specific target organ toxicant and is present at or above the appropriate cut-off value/concentration limit specified in Table A.8.2 for Categories 1 and 2, respectively. 
TABLE A.8.2—C UT-OFFVALUES /CONCENTRATION LIMITS OF INGREDIENTS OF A MIXTURE CLASSIFIED AS A SPECIFIC  
TARGET ORGAN TOXICANT THATWOULD TRIGGER CLASSIFICATION OF THE MIXTURE AS CATEGORY 1 OR2 
Ingredient classified as Cut-off values/concentration 
limits triggering classification of a 
mixture as 
Category 1 Category 2 
Category 1 Target organ toxicant ............................................................................................... ................. ≥1.0% ..............................
Category 2 Target organ toxicant ............................................................................................... ................. .............................. ≥1.0% 
A.8.3.4.2 These cut-off values and 
consequent classifications shall be applied equally and appropriately to both single- and repeated-dose target organ toxicants. 
A.8.3.4.3 Mixtures shall be classified for 
either or both single and repeated dose toxicity independently. 
A.8.3.4.4 Care shall be exercised when 
toxicants affecting more than one organ system are combined that the potentiation or synergistic interactions are considered, because certain substances can cause target organ toxicity at <1% concentration when other ingredients in the mixture are known 
to potentiate its toxic effect. 
A.8.3.4.5 Care shall be exercised when 
extrapolating the toxicity of a mixture that contains Category 3 ingredient(s). A cut-off value/concentration limit of 20%, considered as an additive of all Category 3 ingredients 
for each hazard endpoint, is appropriate; however, this cut-off value/concentration limit may be higher or lower depending on the Category 3 ingredient(s) involved and the fact that some effects such as respiratory tract irritation may not occur below a certain concentration while other effects such as narcotic effects may occur below this 20% 
value. Expert judgment shall be exercised. Respiratory tract irritation and narcotic effects are to be evaluated separately in accordance with the criteria given in A.8.2.2. When conducting classifications for these hazards, the contribution of each ingredient 
should be considered additive, unless there is evidence that the effects are not additive. 
A.8.3.4.6 In cases where the additivity 
approach is used for Category 3 ingredients, the ‘‘relevant ingredients’’ of a mixture are those which are present in concentrations ≥1% (w/w for solids, liquids, dusts, mists, 
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and vapours and v/v for gases), unless there 
is a reason to suspect that an ingredient present at a concentration <1% is still relevant when classifying the mixture for respiratory tract irritation or narcotic effects. 
A.9 Specific Target Organ Toxicity— 
Repeated or Prolonged Exposure 
A.9.1 Definitions and General 
Considerations 
A.9.1.1 Specific target organ toxicity— 
repeated exposure (STOT–RE) refers to 
specific toxic effects on target organs occurring after repeated exposure to a substance or mixture. All significant health effects that can impair function, both reversible and irreversible, immediate and/or delayed and not specifically addressed in A.1 to A.7 and A.10 of this Appendix are included. Specific target organ toxicity following a single-event exposure is classified in accordance with SPECIFIC 
TARGET ORGAN TOXICITY—SINGLE EXPOSURE (A.8 of this Appendix) and is 
therefore not included here. 
A.9.1.2 Classification identifies the 
substance or mixture as being a specific target organ toxicant and, as such, it may present a potential for adverse health effects in people who are exposed to it. 
A.9.1.3 These adverse health effects 
produced by repeated exposure include consistent and identifiable toxic effects in humans, or, in experimental animals, toxicologically significant changes which have affected the function or morphology of a tissue/organ, or have produced serious changes to the biochemistry or hematology of the organism and these changes are relevant for human health. Human data will be the primary source of evidence for this hazard class. 
A.9.1.4 Assessment shall take into 
consideration not only significant changes in 
a single organ or biological system but also generalized changes of a less severe nature involving several organs. 
A.9.1.5 Specific target organ toxicity can 
occur by any route that is relevant for humans, e.g., principally oral, dermal or 
inhalation. 
A.9.2 Classification Criteria for Substances 
A.9.2.1 Substances shall be classified as 
STOT—RE by expert judgment on the basis 
of the weight of all evidence available, including the use of recommended guidance values which take into account the duration of exposure and the dose/concentration which produced the effect(s), ( See A.9.2.9). 
Substances shall be placed in one of two categories, depending upon the nature and severity of the effect(s) observed, in accordance with Figure A.9.1. 
Figure A.9.1—Hazard Categories for Specific 
Target Organ Toxicity Following Repeated Exposure 
CATEGORY 1: Substances that have 
produced significant toxicity in humans, 
or that, on the basis of evidence from studies in experimental animals can be presumed to have the potential to produce significant toxicity in humans following repeated or prolonged exposure Substances are classified in Category 1 for 
specific target organ toxicity (repeated 
exposure) on the basis of: 
(a) reliable and good quality evidence from 
human cases or epidemiological studies; or, 
(b) observations from appropriate studies 
in experimental animals in which significant and/or severe toxic effects, of relevance to human health, were produced at generally low exposure concentrations. Guidance dose/ concentration values are provided below (See A.9.2.9) to be used as part of weight- 
of-evidence evaluation. 
CATEGORY 2: Substances that, on the basis 
of evidence from studies in experimental animals can be presumed to have the potential to be harmful to human health following repeated or prolonged exposure 
Substances are classified in Category 2 for 
specific target organ toxicity (repeated exposure) on the basis of observations from appropriate studies in experimental animals in which significant toxic effects, of relevance to human health, were produced at generally moderate exposure concentrations. Guidance dose/ 
concentration values are provided below 
(See A.9.2.9) in order to help in 
classification. 
In exceptional cases human evidence can 
also be used to place a substance in Category 2 (See A.9.2.6). 
Note: The primary target organ/system 
shall be identified where possible, or the substance shall be identified as a general toxicant. The data shall be carefully evaluated and, where possible, shall not include secondary effects (e.g., a hepatotoxicant can produce secondary effects in the nervous or gastro-intestinal systems). 
A.9.2.2 The relevant route of exposure by 
which the classified substance produces damage shall be identified. 
A.9.2.3 Classification is determined by 
expert judgment, on the basis of the weight of all evidence available including the guidance presented below. 
A.9.2.4 Weight of evidence of all data, 
including human incidents, epidemiology, and studies conducted in experimental animals, is used to substantiate specific target organ toxic effects that merit classification. 
A.9.2.5 The information required to 
evaluate specific target organ toxicity comes either from repeated exposure in humans, e.g., exposure at home, in the workplace or 
environmentally, or from studies conducted in experimental animals. The standard animal studies in rats or mice that provide this information are 28 day, 90 day or lifetime studies (up to 2 years) that include hematological, clinico-chemical and detailed macroscopic and microscopic examination to enable the toxic effects on target tissues/ organs to be identified. Data from repeat dose studies performed in other species may also be used. Other long-term exposure studies, e.g., for carcinogenicity, neurotoxicity or 
reproductive toxicity, may also provide evidence of specific target organ toxicity that could be used in the assessment of classification. 
A.9.2.6 In exceptional cases, based on 
expert judgment, it may be appropriate to place certain substances with human 
evidence of specific target organ toxicity in Category 2: (a) when the weight of human evidence is not sufficiently convincing to warrant Category 1 classification, and/or (b) based on the nature and severity of effects. Dose/concentration levels in humans shall not be considered in the classification and any available evidence from animal studies 
shall be consistent with the Category 2 
classification. In other words, if there are also animal data available on the substance that warrant Category 1 classification, the substance shall be classified as Category 1. 
A.9.2.7 Effects Considered To Support 
Classification 
A.9.2.7.1 Classification is supported by 
reliable evidence associating repeated 
exposure to the substance with a consistent and identifiable toxic effect. 
A.9.2.7.2 Evidence from human 
experience/incidents is usually restricted to reports of adverse health consequences, often with uncertainty about exposure conditions, and may not provide the scientific detail that can be obtained from well-conducted studies in experimental animals. 
A.9.2.7.3 Evidence from appropriate 
studies in experimental animals can furnish much more detail, in the form of clinical observations, hematology, clinical chemistry, macroscopic and microscopic pathological examination and this can often reveal hazards that may not be life-threatening but could indicate functional impairment. Consequently, all available evidence, and relevance to human health, must be taken into consideration in the classification process. Relevant toxic effects in humans and/or animals include, but are not limited to: 
(a) Morbidity or death resulting from 
repeated or long-term exposure. Morbidity or death may result from repeated exposure, even to relatively low doses/concentrations, due to bioaccumulation of the substance or its metabolites, or due to the overwhelming of the de-toxification process by repeated exposure; 
(b) Significant functional changes in the 
central or peripheral nervous systems or other organ systems, including signs of central nervous system depression and effects on special senses ( e.g., sight, hearing 
and sense of smell); 
(c) Any consistent and significant adverse 
change in clinical biochemistry, hematology, or urinalysis parameters; 
(d) Significant organ damage that may be 
noted at necropsy and/or subsequently seen 
or confirmed at microscopic examination; 
(e) Multi-focal or diffuse necrosis, fibrosis 
or granuloma formation in vital organs with regenerative capacity; 
(f) Morphological changes that are 
potentially reversible but provide clear evidence of marked organ dysfunction (e.g., severe fatty change in the liver); and, 
(g) Evidence of appreciable cell death 
(including cell degeneration and reduced cell number) in vital organs incapable of regeneration. 
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A.9.2.8 Effects Considered Not To Support 
Classification 
Effects may be seen in humans and/or 
animals that do not justify classification. 
Such effects include, but are not limited to: 
(a) Clinical observations or small changes 
in bodyweight gain, food consumption or water intake that may have some toxicological importance but that do not, by themselves, indicate ‘‘significant’’ toxicity; 
(b) Small changes in clinical biochemistry, 
hematology or urinalysis parameters and/or transient effects, when such changes or effects are of doubtful or of minimal toxicological importance; 
(c) Changes in organ weights with no 
evidence of organ dysfunction; 
(d) Adaptive responses that are not 
considered toxicologically relevant; 
(e) Substance-induced species-specific 
mechanisms of toxicity, i.e., demonstrated 
with reasonable certainty to be not relevant for human health, shall not justify classification. 
A.9.2.9 Guidance Values To Assist With 
Classification Based on the Results Obtained From Studies Conducted in Experimental Animals 
A.9.2.9.1 In studies conducted in 
experimental animals, reliance on 
observation of effects alone, without reference to the duration of experimental 
exposure and dose/concentration, omits a fundamental concept of toxicology, i.e., all 
substances are potentially toxic, and what 
determines the toxicity is a function of the dose/concentration and the duration of exposure. In most studies conducted in experimental animals the test guidelines use an upper limit dose value. 
A.9.2.9.2 In order to help reach a decision 
about whether a substance shall be classified or not, and to what degree it shall be classified (Category 1 vs. Category 2), dose/ concentration ‘‘guidance values’’ are provided in Table A.9.1 for consideration of the dose/concentration which has been shown to produce significant health effects. The principal argument for proposing such guidance values is that all chemicals are potentially toxic and there has to be a reasonable dose/concentration above which a degree of toxic effect is acknowledged. Also, repeated-dose studies conducted in experimental animals are designed to produce toxicity at the highest dose used in order to optimize the test objective and so most studies will reveal some toxic effect at least at this highest dose. What is therefore to be decided is not only what effects have been produced, but also at what dose/ 
concentration they were produced and how relevant is that for humans. 
A.9.2.9.3 Thus, in animal studies, when 
significant toxic effects are observed that indicate classification, consideration of the duration of experimental exposure and the dose/concentration at which these effects 
were seen, in relation to the suggested guidance values, provides useful information to help assess the need to classify (since the toxic effects are a consequence of the hazardous property(ies) and also the duration of exposure and the dose/concentration). 
A.9.2.9.4 The decision to classify at all 
can be influenced by reference to the dose/ concentration guidance values at or below which a significant toxic effect has been observed. 
A.9.2.9.5 The guidance values refer to 
effects seen in a standard 90-day toxicity study conducted in rats. They can be used as a basis to extrapolate equivalent guidance values for toxicity studies of greater or lesser duration, using dose/exposure time extrapolation similar to Haber’s rule for inhalation, which states essentially that the effective dose is directly proportional to the exposure concentration and the duration of exposure. The assessment should be done on a case- by-case basis; for example, for a 28- day study the guidance values below would be increased by a factor of three. 
A.9.2.9.6 Thus for Category 1 
classification, significant toxic effects observed in a 90-day repeated-dose study conducted in experimental animals and seen to occur at or below the (suggested) guidance values (C) as indicated in Table A.9.1 would 
justify classification: 
TABLE A.9.1—G UIDANCE VALUES TOASSIST IN CATEGORY 1 CLASSIFICATION  
[Applicable to a 90-day study] 
Route of exposure Units Guidance values 
(dose/concentration) 
Oral (rat) ............................................................................................................ mg/kg body weight/day ....................... C ≤ 10 
Dermal (rat or rabbit) ......................................................................................... mg/kg body weigh t/day ....................... C ≤ 20 
Inhalation (rat) gas ............................................................................................. ppmV/6h/day ... .................................... C ≤ 50 
Inhalation (rat) vapor ......................................................................................... mg/liter/6h/day . .................................... C ≤ 0.2 
Inhalation (rat) dust/mist/fume ........................................................................... mg/liter/6h/day ...... ............................... C ≤ 0.02 
A.9.2.9.7 For Category 2 classification, 
significant toxic effects observed in a 90-day 
repeated-dose study conducted in experimental animals and seen to occur 
within the (suggested) guidance value ranges as indicated in Table A.9.2 would justify classification: 
TABLE A.9.2—G UIDANCE VALUES TOASSIST IN CATEGORY 2 CLASSIFICATION  
[Applicable to a 90-day study] 
Route of exposure Units Guidance value range 
(dose/concentration) 
Oral (rat) ............................................................................................................ mg/kg body weight/day ....................... 10 < C ≤ 100 
Dermal (rat or rabbit) ......................................................................................... mg/kg body weight/day ....................... 20 < C ≤ 200 
Inhalation (rat) gas ............................................................................................. ppmV/6h/day ....................................... 50 < C ≤ 250 
Inhalation (rat) vapor ......................................................................................... mg/liter/6h/day ..................................... 0.2 < C ≤ 1.0 
Inhalation (rat) dust/mist/fume ........................................................................... mg/liter/6h/day ..................................... 0.02 < C ≤ 0.2 
A.9.2.9.8 The guidance values and ranges 
mentioned in A.2.9.9.6 and A.2.9.9.7 are 
intended only for guidance purposes, i.e., to 
be used as part of the weight of evidence approach, and to assist with decisions about classification. They are not intended as strict demarcation values. 
A.9.2.9.9 Thus, it is possible that a 
specific profile of toxicity occurs in repeat- dose animal studies at a dose/concentration below the guidance value, e.g., <100 mg/kg 
body weight/day by the oral route, however the nature of the effect, e.g., nephrotoxicity 
seen only in male rats of a particular strain known to be susceptible to this effect, may result in the decision not to classify. Conversely, a specific profile of toxicity may 
be seen in animal studies occurring at above a guidance value, e.g., ≥100 mg/kg body 
weight/day by the oral route, and in addition 
there is supplementary information from other sources, e.g., other long-term 
administration studies, or human case experience, which supports a conclusion that, in view of the weight of evidence, classification is prudent. 
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A.9.2.10 Other Considerations 
A.9.2.10.1 When a substance is 
characterized only by use of animal data the 
classification process includes reference to dose/concentration guidance values as one of the elements that contribute to the weight of evidence approach. 
A.9.2.10.2 When well-substantiated 
human data are available showing a specific target organ toxic effect that can be reliably attributed to repeated or prolonged exposure to a substance, the substance shall be classified. Positive human data, regardless of probable dose, predominates over animal data. Thus, if a substance is unclassified because no specific target organ toxicity was seen at or below the dose/concentration guidance value for animal testing, if subsequent human incident data become available showing a specific target organ toxic effect, the substance shall be classified. 
A.9.2.10.3 A substance that has not been 
tested for specific target organ toxicity may 
in certain instances, where appropriate, be classified on the basis of data from a scientifically validated structure activity relationship and expert judgment-based extrapolation from a structural analogue that has previously been classified together with substantial support from consideration of 
other important factors such as formation of common significant metabolites. 
A.9.3 Classification Criteria for Mixtures 
A.9.3.1 Mixtures are classified using the 
same criteria as for substances, or 
alternatively as described below. As with substances, mixtures may be classified for specific target organ toxicity following single exposure, repeated exposure, or both. 
A.9.3.2 Classification of Mixtures When 
Data Are Available for the Complete Mixture 
When reliable and good quality evidence 
from human experience or appropriate studies in experimental animals, as described in the criteria for substances, is available for the mixture, then the mixture shall be classified by weight of evidence evaluation of these data. Care shall be exercised in evaluating data on mixtures, that the dose, duration, observation or analysis, do not render the results inconclusive. 
A.9.3.3 Classification of Mixtures When 
Data Are Not Available for the Complete Mixture: Bridging Principles 
A.9.3.3.1 Where the mixture itself has not 
been tested to determine its specific target organ toxicity, but there are sufficient data on 
both the individual ingredients and similar tested mixtures to adequately characterize the hazards of the mixture, these data shall be used in accordance with the following bridging principles as found in paragraph A.0.5 of this Appendix: Dilution; Batching; Concentration of mixtures; Interpolation within one hazard category; Substantially similar mixtures; and Aerosols. 
A.9.3.4 Classification of Mixtures When 
Data Are Available for All Ingredients or Only for Some Ingredients of the Mixture 
A.9.3.4.1 Where there is no reliable 
evidence or test data for the specific mixture 
itself, and the bridging principles cannot be used to enable classification, then classification of the mixture is based on the 
classification of the ingredient substances. In this case, the mixture shall be classified as a specific target organ toxicant (specific organ specified), following single exposure, repeated exposure, or both when at least one ingredient has been classified as a Category 1 or Category 2 specific target organ toxicant and is present at or above the appropriate cut-off value/concentration limit specified in Table A.9.3 for Category 1 and 2 respectively. 
TABLE A.9.3—C UT-OFFVALUE /CONCENTRATION LIMITS OF INGREDIENTS OF A MIXTURE CLASSIFIED AS A SPECIFIC  
TARGET ORGAN TOXICANT THATWOULD TRIGGER CLASSIFICATION OF THE MIXTURE AS CATEGORY 1 OR2 
Ingredient classified as Cut-off values/concentration 
limits triggering classification of a mix-
ture as 
Category 1 Category 2 
Category 1 Target organ toxicant ............................................................................................... ................. ≥1.0% ..............................
Category 2 Target organ toxicant ............................................................................................... ................. .............................. ≥1.0% 
A.9.3.4.2 These cut-off values and 
consequent classifications shall be applied 
equally and appropriately to both single- and repeated-dose target organ toxicants. 
A.9.3.4.3 Mixtures shall be classified for 
either or both single- and repeated-dose toxicity independently. 
A.9.3.4.4 Care shall be exercised when 
toxicants affecting more than one organ system are combined that the potentiation or synergistic interactions are considered, because certain substances can cause specific target organ toxicity at <1% concentration when other ingredients in the mixture are known to potentiate its toxic effect. A.10 Aspiration Hazard 
A.10.1 Definitions and General 
Considerations 
A.10.1.1 Aspiration hazard refers to 
severe acute effects such as chemical 
pneumonia, pulmonary injury or death occurring after aspiration of a substance or mixture. 
A.10.1.2 Aspiration means the entry of a 
liquid or solid chemical directly through the oral or nasal cavity, or indirectly from vomiting, into the trachea and lower respiratory system. 
A.10.1.3 Aspiration is initiated at the 
moment of inspiration, in the time required to take one breath, as the causative material 
lodges at the crossroad of the upper respiratory and digestive tracts in the 
laryngopharyngeal region. 
A.10.1.4 Aspiration of a substance or 
mixture can occur as it is vomited following ingestion. This may have consequences for labeling, particularly where, due to acute toxicity, a recommendation may be 
considered to induce vomiting after ingestion. However, if the substance/mixture also presents an aspiration toxicity hazard, the recommendation to induce vomiting may need to be modified. 
A.10.1.5 Specific Considerations 
A.10.1.5.1 The classification criteria refer 
to kinematic viscosity. The following 
provides the conversion between dynamic and kinematic viscosity: 
A.10.1.5.2 Although the definition of 
aspiration in A.10.1.1 includes the entry of 
solids into the respiratory system, classification according to (b) in table A.10.1 for Category 1 is intended to apply to liquid substances and mixtures only. 
A.10.1.5.3 Classification of aerosol/mist 
products Aerosol and mist products are usually 
dispensed in containers such as self- pressurized containers, trigger and pump sprayers. Classification for these products shall be considered if their use may form a pool of product in the mouth, which then may be aspirated. If the mist or aerosol from a pressurized container is fine, a pool may not be formed. On the other hand, if a 
pressurized container dispenses product in a 
stream, a pool may be formed that may then be aspirated. Usually, the mist produced by trigger and pump sprayers is coarse and therefore, a pool may be formed that then may be aspirated. When the pump mechanism may be removed and contents are 
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available to be swallowed then the classification of the products should be 
considered. A.10.2 Classification Criteria for Substances 
TABLE A.10.1—C RITERIA FOR ASPIRATION TOXICITY  
Category Criteria 
Category 1: Chemicals known to cause human aspiration 
toxicity hazards or to be regarded as if they cause 
human aspiration toxicity hazard.A substance shall be classified in Category 1: 
(a) If reliable and good quality human evidence indicates that it causes aspira-
tion toxicity (See note); or 
(b) If it is a hydrocarbon and has a kinematic viscosity ≤20.5 mm 2/s, measured 
at 40 °C. 
Note: Examples of substances included in Category 1 are certain hydrocarbons, turpentine and pine oil. 
A.10.3 Classification Criteria for Mixtures 
A.10.3.1 Classification When Data Are 
Available for the Complete Mixture 
A mixture shall be classified in Category 1 
based on reliable and good quality human 
evidence. 
A.10.3.2 Classification of Mixtures When 
Data Are Not Available for the Complete Mixture: Bridging Principles 
A.10.3.2.1 Where the mixture itself has 
not been tested to determine its aspiration toxicity, but there are sufficient data on both the individual ingredients and similar tested mixtures to adequately characterize the hazard of the mixture, these data shall be used in accordance with the following bridging principles as found in paragraph A.0.5 of this Appendix: Dilution; Batching; Concentration of mixtures; Interpolation within one hazard category; and Substantially similar mixtures. For application of the dilution bridging principle, the concentration of aspiration toxicants shall not be less than 10%. 
A.10.3.3 Classification of Mixtures When 
Data Are Available for All Ingredients or Only for Some Ingredients of the Mixture 
A.10.3.3.1 The ‘‘relevant ingredients’’ of a 
mixture are those which are present in concentrations ≥1%. 
A.10.3.3.2 Category 1 
A.10.3.3.2.1 A mixture is classified as 
Category 1 when the sum of the concentrations of Category 1 ingredients is ≥10%, and the mixture has a kinematic viscosity of ≤20.5 mm
2/s, measured at 40 °C. 
A.10.3.3.2.2 In the case of a mixture 
which separates into two or more distinct layers, the entire mixture is classified as Category 1 if in any distinct layer the sum of the concentrations of Category 1 ingredients is ≥10%, and it has a kinematic viscosity of 
≤20.5 mm
2/s, measured at 40 °C. 
Appendix B to § 1910.1200—Physical 
Hazard Criteria (Mandatory) 
B.1 Explosives 
B.1.1 Definitions and General 
Considerations 
B.1.1.1 An explosive chemical is a solid 
or liquid chemical which is in itself capable by chemical reaction of producing gas at such a temperature and pressure and at such a speed as to cause damage to the surroundings. Pyrotechnic chemicals are included even when they do not evolve gases. A pyrotechnic chemical is a chemical 
designed to produce an effect by heat, light, 
sound, gas or smoke or a combination of these as the result of non-detonative self- sustaining exothermic chemical reactions. 
An explosive item is an item containing 
one or more explosive chemicals. 
A pyrotechnic item is an item containing 
one or more pyrotechnic chemicals. 
An unstable explosive is an explosive 
which is thermally unstable and/or too 
sensitive for normal handling, transport, or use. 
An intentional explosive is a chemical or 
item which is manufactured with a view to produce a practical explosive or pyrotechnic effect. 
B.1.1.2 The class of explosives comprises: (a) Explosive chemicals; (b) Explosive items, except devices 
containing explosive chemicals in such quantity or of such a character that their inadvertent or accidental ignition or initiation shall not cause any effect external to the device either by projection, fire, smoke, heat or loud noise; and 
(c) Chemicals and items not included 
under (a) and (b) of this section which are manufactured with the view to producing a practical explosive or pyrotechnic effect. 
B.1.2 Classification Criteria 
Chemicals and items of this class shall be 
classified as unstable explosives or shall be 
assigned to one of the following six divisions depending on the type of hazard they present: 
(a) Division 1.1—Chemicals and items 
which have a mass explosion hazard (a mass explosion is one which affects almost the entire quantity present virtually instantaneously); 
(b) Division 1.2—Chemicals and items 
which have a projection hazard but not a mass explosion hazard; 
(c) Division 1.3—Chemicals and items 
which have a fire hazard and either a minor blast hazard or a minor projection hazard or both, but not a mass explosion hazard: 
(i) Combustion of which gives rise to 
considerable radiant heat; or 
(ii) Which burn one after another, 
producing minor blast or projection effects or both; 
(d) Division 1.4—Chemicals and items 
which present no significant hazard: chemicals and items which present only a small hazard in the event of ignition or initiation. The effects are largely confined to the package and no projection of fragments of appreciable size or range is to be expected. An external fire shall not cause virtually 
instantaneous explosion of almost the entire contents of the package; 
(e) Division 1.5—Very insensitive 
chemicals which have a mass explosion hazard: chemicals which have a mass explosion hazard but are so insensitive that there is very little probability of initiation or of transition from burning to detonation under normal conditions; 
(f) Division 1.6—Extremely insensitive 
items which do not have a mass explosion hazard: items which predominantly contain 
extremely insensitive detonating chemicals 
and which demonstrate a negligible probability of accidental initiation or propagation. 
B.1.3 Additional Classification 
Considerations 
B.1.3.1 Explosives shall be classified as 
unstable explosives or shall be assigned to 
one of the six divisions identified in B.1.2 in accordance with the three step procedure in Part I of UN ST/SG/AC.10 (incorporated by reference, see § 1910.6). The first step is to ascertain whether the substance or mixture has explosive effects (Test Series 1). The second step is the acceptance procedure (Test Series 2 to 4) and the third step is the assignment to a hazard division (Test Series 5 to 7). The assessment whether a candidate for ‘‘ammonium nitrate emulsion or suspension or gel, intermediate for blasting explosives (ANE)’’ is insensitive enough for inclusion as an oxidizing liquid ( see B.13 of 
this appendix) or an oxidizing solid (see B.14 
of this appendix) is determined by Test Series 8 tests of UN ST/SG/AC.10/. 
Note 1: Classification of solid chemicals 
shall be based on tests performed on the chemical as presented. If, for example, for the purposes of supply or transport, the same chemical is to be presented in a physical form different from that which was tested and which is considered likely to materially alter its performance in a classification test, classification must be based on testing of the chemical in the new form. 
Note 2: Some explosive chemicals are 
wetted with water or alcohols, diluted with other substances or dissolved or suspended in water or other liquid substances to suppress or reduce their explosive properties or sensitivity. 
These chemicals shall be classified as 
desensitized explosives (see Chapter B.17). 
Note 3: Chemicals with a positive result in 
Test Series 2 in Part I, Section 12 of UN ST/ SG/AC.10/11/Rev.6 (incorporated by 
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reference; see § 1910.6) which are exempted 
from classification as explosives (based on a negative result in Test Series 6 in Part I, Section 16 of UN ST/SG/AC.10/11/Rev.6 (incorporated by reference; see § 1910.6)), still have explosive properties. The explosive properties of the chemical shall be communicated in Section 2 (Hazard identification) and Section 9 (Physical and chemical properties) of the Safety Data Sheet, as appropriate. 
B.1.3.2 Explosive properties are 
associated with the presence of certain chemical groups in a molecule which can react to produce very rapid increases in temperature or pressure. The screening procedure in B.1.3.1 is aimed at identifying the presence of such reactive groups and the potential for rapid energy release. If the screening procedure identifies the chemical as a potential explosive, the acceptance procedure (see section 10.3 of the UN ST/SG/ 
AC.10 (incorporated by reference; see § 1910.6)) is necessary for classification. 
Note: Neither a Series 1 type (a) 
propagation of detonation test nor a Series 2 
type (a) test of sensitivity to detonative shock is necessary if the exothermic decomposition energy of organic materials is less than 800 J/g. B.1.3.3 If a mixture contains any known 
explosives, the acceptance procedure is necessary for classification. 
B.1.3.4 A chemical is not classified as 
explosive if: 
(a) There are no chemical groups 
associated with explosive properties present in the molecule. Examples of groups which may indicate explosive properties are given in Table A6.1 in Appendix 6 of the UN ST/ SG/AC.10 (incorporated by reference; See § 1910.6); or 
(b) The substance contains chemical 
groups associated with explosive properties which include oxygen and the calculated oxygen balance is less than ¥200. 
The oxygen balance is calculated for the 
chemical reaction: 
CxHyOz + [x + (y/4)¥(z/2)] O2 → x. CO
2+ 
(y/2) H 2O 
using the formula: oxygen balance = ¥1600 
[2x + (y/2)¥z]/molecular weight; or 
(c) The organic substance or a homogenous 
mixture of organic substances contains 
chemical groups associated with explosive 
properties but the exothermic decomposition energy is less than 500 J/g and the onset of exothermic decomposition is below 500 °C 
(932 °F). The exothermic decomposition energy may be determined using a suitable 
calorimetric technique; or 
(d) For mixtures of inorganic oxidizing 
substances with organic material(s), the concentration of the inorganic oxidizing 
substance is: 
(i) less than 15%, by mass, if the oxidizing 
substance is assigned to Category 1 or 2; 
(ii) less than 30%, by mass, if the oxidizing 
substance is assigned to Category 3. 
B.2 Flammable Gases B.2.1 Definition 
Flammable gas means a gas having a 
flammable range with air at 20 °C (68 °F) and 
a standard pressure of 101.3 kPa (14.7 psi). 
A pyrophoric gas means a flammable gas 
that is liable to ignite spontaneously in air at 
a temperature of 54 °C (130 °F) or below. 
A chemically unstable gas means a 
flammable gas that is able to react explosively even in the absence of air or oxygen. 
B.2.2 Classification Criteria 
B.2.2.1 A flammable gas shall be 
classified in Category 1A, 1B, or 2 in 
accordance with Table B.2.1: 
TABLE B.2.1—C RITERIA FOR FLAMMABLE GASES  
Category Criteria 
1A .............. Flammable gas ............... Gases, which at 20 °C (68 °F) and a standard pressure of 101.3 kPa (14.7 psi): 
(a) are ignitable when in a mixture of 13% or less by volume in air; or 
(b) have a flammable range with air of at least 12 percentage points regardless of the lower flam-
mability limit, 
unless data show they meet the criteria for Category 1B. 
Pyrophoric gas ................ Flammable gases that ignite spontaneously in air at a temperature of 54 °C (130 °F) or below. 
Chemically unstable gas: 
A .............................. Flammable gases which are chemically unstable at 20 °C (68 °F) and a standard pressure of 101.3 
kPa (14.7 psi). 
B .............................. Flammable gases which are chemically unstable at a temperature greater than 20 °C (68 °F) and/or a 
pressure greater than 101.3 kPa (14.7 psi). 
1B .............. Flammable gas ............... Gases which meet the flammability criteria for Category 1A, but which are not pyrophoric, nor chemi-
cally unstable, and which have at least either: 
(a) a lower flammability limit of more than 6% by volume in air; or (b) a fundamental burning velocity of less than 10 cm/s. 
2 ................ Flammable gas ............... Gases, other than those of Category 1A or 1B, which, at 20 °C (68 °F) and a standard pressure of 
101.3 kPa (14.7 psi), have a flammable range while mixed in air. 
Note 1: Aerosols should not be classified 
as flammable gases. See B.3. 
Note 2: In the absence of data allowing 
classification into Category 1B, a flammable 
gas that meets the criteria for Category 1A shall be classified by default in Category 1A. 
Note 3: Spontaneous ignition for 
pyrophoric gases is not always immediate, and there may be a delay. 
Note 4: In the absence of data on its 
pyrophoricity, a flammable gas mixture shall 
be classified as a pyrophoric gas if it contains more than 1% (by volume) of pyrophoric component(s). 
B.2.3 Additional Classification 
Considerations 
B.2.3.1 Flammability shall be determined 
by tests or by calculation in accordance with ISO 10156:1996 or ISO 10156:2017 (incorporated by reference; see § 1910.6) and, 
if using fundamental burning velocity for Category 1B, use Annex C: Method of test for burning velocity measurement of flammable gases of ISO 817:2014(E) (incorporated by reference; see § 1910.6). Where insufficient data are available to use this method, equivalent validated methods may be used. 
B.2.3.2 Pyrophoricity shall be determined 
at 130 °F (54 °C) in accordance with either 
IEC 60079–20–1 or DIN 51794:2003 (incorporated by reference; see § 1910.6). 
B.2.3.3 The classification procedure for 
pyrophoric gases need not be applied when 
experience in production or handling shows that the substance does not ignite spontaneously on coming into contact with air at a temperature of 130 °F (54 °C) or 
below. Flammable gas mixtures, which have not been tested for pyrophoricity and which contain more than one percent pyrophoric components shall be classified as a 
pyrophoric gas. Expert judgement on the properties and physical hazards of pyrophoric gases and their mixtures should be used in assessing the need for classification of flammable gas mixtures containing one percent or less pyrophoric components. In this case, testing need only be considered if expert judgement indicates 
a need for additional data to support the classification process. 
B.2.3.4 Chemical instability shall be 
determined in accordance with the method described in Part III of the UN ST/SG/AC.10/ 11/Rev.6 (incorporated by reference; see § 1910.6). If the calculations performed in accordance with ISO 10156:1996 or ISO 10156:2017 (incorporated by reference; see § 1910.6) show that a gas mixture is not flammable, no additional testing is required 
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for determining chemical instability for 
classification purposes. 
B.3 Aerosols and Chemicals Under 
Pressure 
B.3.1 Aerosols 
B.3.1.1 Definition 
Aerosol means any non-refillable 
receptacle containing a gas compressed, 
liquefied or dissolved under pressure, and fitted with a release device allowing the 
contents to be ejected as particles in suspension in a gas, or as a foam, paste, powder, liquid or gas. 
B.3.1.2 Classification Criteria 
B.3.1.2.1 Aerosols are classified in one of 
three categories, depending on their 
flammable properties and their heat of combustion. Aerosols shall be considered for classification in Categories 1 or 2 if they contain more than 1% components (by mass) 
which are classified as flammable in accordance with this Appendix B, i.e.: 
Flammable gases (see B.2); 
Flammable liquids (see B.6) 
Flammable solids (see B.7) 
or if their heat of combustion is at least 20 
kJ/g. 
B.3.1.2.2 An aerosol shall be classified in 
one of the three categories for this class in accordance with Table B.3.1. 
TABLE B.3.1—C RITERIA FOR AEROSOLS  
Category Criteria 
1 .............................. Contains ≥85% flammable components and the chemical heat of combustion is ≥30 kJ/g; or 
(a) For spray aerosols, in the ignition distance test, ignition occurs at a distance ≥75 cm (29.5 in), or 
(b) For foam aerosols, in the aerosol foam flammability test. 
(i) The flame height is ≥20 cm (7.87 in) and the flame duration ≥2 s; or 
(ii) The flame height is ≥4 cm (1.57 in) and the flame duration ≥7 s. 
2 .............................. Contains >1% flammable components, or the heat of combustion is ≥20 kJ/g; and 
(a) for spray aerosols, in the ignition distance test, ignition occurs at a distance ≥15 cm (5.9 in), or 
in the enclosed space ignition test, the 
(i) Time equivalent is ≤300 s/m3; or 
(ii) Deflagration density is ≤300 g/m3 
(b) For foam aerosols, in the aerosol foam flammability test, the flame height is ≥4 cm and the flame duration is ≥2 s 
and it does not meet the criteria for Category 1. 
3 .............................. (1) The chemical does not meet the criteria for Categories 1 and 2. 
(2) The chemical contains ≤1% flammable components (by mass) and has a heat of combustion <20 kJ/g. 
Note 1: Flammable components do not 
include pyrophoric, self-heating or water- 
reactive chemicals. 
Note 2: Aerosols do not fall additionally 
within the scope of flammable gases, gases under pressure, flammable liquids, or flammable solids. However, depending on their contents, aerosols may fall within the scope of other hazard classes. 
Note 3: Aerosols containing more than 1% 
flammable components or with a heat of combustion of at least 20 kJ/g, which are not submitted to the flammability classification procedures in this Appendix shall be 
classified as Category 1. B.3.2 Chemicals Under Pressure 
B.3.2.1 Definition 
Chemicals under pressure are liquids or 
solids (e.g., pastes or powders), pressurized 
with a gas at a pressure of 200 kPa (gauge) 
or more at 20 °C in pressure receptacles other 
than aerosol dispensers and which are not classified as gases under pressure. 
Note: Chemicals under pressure typically 
contain 50% or more by mass of liquids or solids whereas mixtures containing more than 50% gases are typically considered as gases under pressure. B.3.2.2 Classification Criteria 
B.3.2.2.1 Chemicals under pressure are 
classified in one of three categories of this hazard class, in accordance with Table B.3.2, depending on their content of flammable components and their heat of combustion 
B.3.2.2.2 Flammable components are 
components which are classified as flammable in accordance with the GHS criteria, i.e.: 
—Flammable gases (see B..2 of this section); 
—Flammable liquids (see B.6 of this section); 
—Flammable solids (see B.7 of this section). 
TABLE B.3.2—C RITERIA FOR CHEMICALS UNDER PRESSURE  
Category Criteria 
1 .............................. Any chemical under pressure that: 
(a) contains ≥85% flammable components (by mass); and 
(b) has a heat of combustion of ≥20 kJ/g. 
2 .............................. Any chemical under pressure that: 
(a) contains >1% flammable components (by mass); and (b) has a heat of combustion <20 kJ/g; 
or that: 
(a) contains <85% flammable components (by mass); and (b) has a heat of combustion ≥20 kJ/g. 
3 .............................. Any chemical under pressure that: 
(a) contains ≤1% flammable components (by mass); and (b) has a heat of combustion of <20 kJ/g. 
Note 1: The flammable components in a 
chemical under pressure do not include 
pyrophoric, self-heating or water-reactive, substances and mixtures because such components are not allowed in chemicals under pressure in accordance with the UN Model Regulations. Note 2: Chemicals under pressure do not 
fall additionally within the scope of section B.3.1 (aerosols), B.2.2 (flammable gases), B.2.5 (gases under pressure), B.2.6 (flammable liquids) and B.2.7 (flammable solids). Depending on their contents, chemicals under pressure may however fall within the scope of other hazard classes, 
including their labelling elements. 
B.3.3 Additional Classification 
Considerations 
B.3.3.1 To classify an aerosol, data on its 
flammable components, on its chemical heat 
of combustion and, if applicable, the results 
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of the aerosol foam flammability test (for 
foam aerosols) and of the ignition distance test and enclosed space test (for spray aerosols) are necessary. 
B.3.3.2 The chemical heat of combustion 
(DHc), in kilojoules per gram (kJ/g), is the product of the theoretical heat of combustion (DHcomb), and a combustion efficiency, usually less than 1.0 (a typical combustion efficiency is 0.95 or 95%). 
For a composite formulation, the chemical 
heat of combustion is the summation of the weighted heats of combustion for the 
individual components, as follows: 
where: 
DH c(product) = specific heat of combustion 
(kJ/g) of the product; 
DH c(i) = specific heat of combustion (kJ/g) of 
component i in the product; 
w(i) = mass fraction of component i in the 
product; 
n = total number of components in the 
product. 
B.3.3.3 The chemical heats of combustion 
shall be found in literature, calculated or 
determined by tests: (see ASTM D240; Sections 86.1 to 86.3 of ISO 13943; and NFPA 30B (incorporated by reference; see § 1910.6)). 
B.3.3.4 The Ignition Distance Test, 
Enclosed Space Ignition Test and Aerosol Foam Flammability Test shall be performed in accordance with sub-sections 31.4, 31.5 and 31.6 of UN ST/SG/AC.10 (incorporated by reference; see § 1910.6). 
B.4 Oxidizing Gases B.4.1 Definition 
Oxidizing gas means any gas which may, 
generally by providing oxygen, cause or contribute to the combustion of other 
material more than air does. 
Note: ‘‘Gases which cause or contribute to 
the combustion of other material more than air does’’ means pure gases or gas mixtures with an oxidizing power greater than 23.5% (as determined by a method specified in ISO 10156:1996, ISO 10156:2017 or 10156–2:2005 (incorporated by reference; see § 1910.6) or an equivalent testing method). 
B.4.2 Classification Criteria 
An oxidizing gas shall be classified in a 
single category for this class in accordance 
with Table B.4.1: 
TABLE B.4.1—C RITERIA FOR OXIDIZING  
GASES  
Category Criteria 
1 ........... Any gas which may, generally by 
providing oxygen, cause or con-
tribute to the combustion of other material more than air does. B.4.3 Additional Classification 
Considerations 
Classification shall be in accordance with 
tests or calculation methods as described in 
ISO 10156:1996, ISO 10156:2017 or 10156– 2:2005 (incorporated by reference; see § 1910.6). 
B.5 Gases Under Pressure B.5.1 Definition 
Gases under pressure are gases which are 
contained in a receptacle at a pressure of 200 
kPa (29 psi) (gauge) or more at 20 °C (68 °F), 
or which are liquefied or liquefied and refrigerated. 
They comprise compressed gases, liquefied 
gases, dissolved gases and refrigerated liquefied gases. 
B.5.2 Classification Criteria 
Gases under pressure shall be classified in 
one of four groups in accordance with Table 
B.5.1: 
TABLE B.5.1—C RITERIA FOR GASES UNDER PRESSURE  
Group Criteria 
Compressed Gas ............................ A gas which when inder pressure is entirely gaseous at ¥50 °C (¥58 °F), including all gases with a critical 
temperature1≤¥50 °C (¥58 °F) 
Liquedfied gas ................................. A gas which when inder pressure, is partially liquid at termperatures above ¥50 °C (¥58 °F) A disinction 
is made between: 
(a) High pressure liquefied gas: a gas with a critical termperature1between ¥50 °C (¥58 °F) and 
+65°C (149 °F); and 
(b) Low pressure liquefied gas: a gas with a critical temperature1above +65 °C (149 °F) 
Refrigerated liquefied gas ............... A gas which is made partially liquid becuase of its low temperature. 
Dissolved gas .................................. A gas which when under pressure is dissolved in a liquid phase solvent. 
1The critical temperature is the temperature above which a pure gas cannot be liquefied, regardless of the degree of compression . 
Note: Aerosols should not be classified as 
gases under pressure. See Appendix B.3 of 
this section. 
B.6 Flammable Liquids 
B.6.1 Definition 
Flammable liquid means a liquid having a 
flash point of not more than 93 °C (199.4 °F). 
Flash point means the minimum 
temperature at which a liquid gives off vapor 
in sufficient concentration to form an 
ignitable mixture with air near the surface of the liquid, as determined by a method identified in Section B.6.3 of this appendix. 
B.6.2 Classification Criteria 
A flammable liquid shall be classified in 
one of four categories in accordance with 
Table B.6.1 of this appendix: TABLE B.6.1—C RITERIA FOR  
FLAMMABLE LIQUIDS  
Category Criteria 
1 ........... Flash point <23 °C (73.4 °F) and 
initial boiling point ≤35 °C 
(95°F). 
2 ........... Flash point <23 °C (73.4 °F) and 
initial boiling point >35 °C 
(95°F). 
3 ........... Flash point ≥23 °C (73.4 °F) and 
≤60°C (140 °F). 
4 ........... Flash point >60 °C (140 °F) and 
≤93°C (199.4 °F). Note: Aerosols should not be classified as 
flammable liquids. See Appendix B.3 of this 
section. 
B.6.3 Additional Classification 
Considerations 
The flash point shall be determined in 
accordance with ASTM D56–05, ASTM 
D3278, ASTM D3828, ASTM D93–08 (incorporated by reference, see § 1910.6), or any method specified in 29 CFR 1910.106(a)(14). It may also be determined by any other method specified in GHS Revision 7, Chapter 2.6. 
The initial boiling point shall be 
determined in accordance with ASTM D86– 
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9To determine the appropriate flammable liquid 
storage container size and type, the boiling point 
shall be determined by § 1910.106(a)(5). In addition, the manufacturer, importer, and distributor shall clearly note in sections 7 and 9 of the SDS if an alternate calculation was used for storage purposes and the classification for storage differs from the classification listed in Section 2 of the SDS. 07a or ASTM D1078 (incorporated by 
reference; see § 1910.6).9 
B.7 Flammable Solids 
B.71 Definitions 
Flammable solid means a solid which is a 
readily combustible solid, or which may 
cause or contribute to fire through friction. 
Readily combustible solids are powdered, 
granular, or pasty chemicals which are 
dangerous if they can be easily ignited by brief contact with an ignition source, such as a burning match, and if the flame spreads rapidly. 
B.7.2 Classification Criteria 
B.7.2.1 Powdered, granular or pasty 
chemicals shall be classified as flammable 
solids when the time of burning of one or more of the test runs, performed in accordance with the test method described in Part III, sub-section 33.2.1 of UN ST/SG/ AC.10 (incorporated by reference; see § 1910.6), is less than 45 s or the rate of burning is more than 2.2 mm/s (0.0866 in/s). 
B.7.2.2 Powders of metals or metal alloys 
shall be classified as flammable solids when they can be ignited and the reaction spreads over the whole length of the sample in 10 min or less. 
B.7.2.3 Solids which may cause fire 
through friction shall be classified in this class by analogy with existing entries ( e.g., 
matches) until definitive criteria are established. 
B.7.2.4 A flammable solid shall be 
classified in one of the two categories for this class using Method N.1 as described in Part III, sub-section 33.2.1 of UN ST/SG/AC.10 (incorporated by reference; see § 1910.6), in accordance with Table B.7.1: 
TABLE B.7.1—C RITERIA FOR  
FLAMMABLE SOLIDS  
Category Criteria 
1 ........... Burning rate test: 
Chemicals other than metal 
powders: 
(a) Wetted zone does not 
stop fire; and 
(b) Burning time <45 s or 
burning rate >2.2 mm/s 
Metal powders: burning time 
≤5 min. 
2 ........... Burning rate test: 
Chemicals other than metal 
powders: 
(a) Wetted zone stops the 
fire for at least 4 min; and 
(b) Burning time <45 s or 
burning rate >2.2 mm/s 
Metal powders: burning time 
>5 min and ≤10 min. Note 1: Classification of solid chemicals 
shall be based on tests performed on the 
chemical as presented. If, for example, for the purposes of supply or transport, the same chemical is to be presented in a physical form different from that which was tested and which is considered likely to materially alter its performance in a classification test, classification must be based on testing of the chemical in the new form. 
Note 2: Aerosols should not be classified 
as flammable solids. See Appendix B.3. 
B.8 Self-Reactive Chemicals 
B.8.1 Definitions 
Self-reactive chemicals are thermally 
unstable liquid or solid chemicals liable to 
undergo a strongly exothermic decomposition even without participation of oxygen (air). This definition excludes chemicals classified under this section as explosives, organic peroxides, oxidizing liquids or oxidizing solids. 
A self-reactive chemical is regarded as 
possessing explosive properties when in laboratory testing the formulation is liable to detonate, to deflagrate rapidly or to show a violent effect when heated under confinement. 
B.8.2 Classification Criteria 
B.8.2.1 A self-reactive chemical shall be 
considered for classification in this class 
unless: 
(a) It is classified as an explosive according 
to B.1 of this appendix; 
(b) It is classified as an oxidizing liquid or 
an oxidizing solid according to B.13 or B.14 of this appendix, except that a mixture of oxidizing substances which contains 5% or 
more of combustible organic substances shall be classified as a self-reactive chemical according to the procedure defined in B.8.2.2; 
(c) It is classified as an organic peroxide 
according to B.15 of this appendix; 
(d) Its heat of decomposition is less than 
300 J/g; or 
(e) Its self-accelerating decomposition 
temperature (SADT) is greater than 75 ° C 
(167 °F) for a 50 kg (110 lb) package. 
B.8.2.2 Mixtures of oxidizing substances, 
meeting the criteria for classification as oxidizing liquids or oxidizing solids, which contain 5% or more of combustible organic substances and which do not meet the criteria mentioned in B.8.2.1(a), (c), (d) or (e), shall be subjected to the self-reactive chemicals classification procedure in B.8.2.3. Such a mixture showing the properties of a self-reactive chemical type B to F shall be classified as a self-reactive chemical. 
B.8.2.3 Self-reactive chemicals shall be 
classified in one of the seven categories of ‘‘types A to G’’ for this class, according to the following principles: 
(a) Any self-reactive chemical which can 
detonate or deflagrate rapidly, as packaged, will be defined as self-reactive chemical TYPE A; 
(b) Any self-reactive chemical possessing 
explosive properties and which, as packaged, neither detonates nor deflagrates rapidly, but is liable to undergo a thermal explosion in that package will be defined as self-reactive chemical TYPE B; (c) Any self-reactive chemical possessing 
explosive properties when the chemical as packaged cannot detonate or deflagrate rapidly or undergo a thermal explosion will be defined as self-reactive chemical TYPE C; 
(d) Any self-reactive chemical which in 
laboratory testing meets the criteria in (d)(i), (ii), or (iii) will be defined as self-reactive chemical TYPE D: 
(i) Detonates partially, does not deflagrate 
rapidly and shows no violent effect when 
heated under confinement; or 
(ii) Does not detonate at all, deflagrates 
slowly and shows no violent effect when heated under confinement; or 
(iii) Does not detonate or deflagrate at all 
and shows a medium effect when heated under confinement; 
(e) Any self-reactive chemical which, in 
laboratory testing, neither detonates nor deflagrates at all and shows low or no effect when heated under confinement will be defined as self-reactive chemical TYPE E; 
(f) Any self-reactive chemical which, in 
laboratory testing, neither detonates in the cavitated state nor deflagrates at all and shows only a low or no effect when heated under confinement as well as low or no explosive power will be defined as self- reactive chemical TYPE F; 
(g) Any self-reactive chemical which, in 
laboratory testing, neither detonates in the cavitated state nor deflagrates at all and shows no effect when heated under confinement nor any explosive power, provided that it is thermally stable (self- accelerating decomposition temperature is 60 °C (140 °F) to 75° C (167 °F) for a 50 kg (110 
lb) package), and, for liquid mixtures, a diluent having a boiling point greater than or equal to 150 °C (302 °F) is used for desensitization will be defined as self- reactive chemical TYPE G. If the mixture is not thermally stable or a diluent having a boiling point less than 150 °C (302 °F) is used for desensitization, the mixture shall be defined as self-reactive chemical TYPE F. 
B.8.3 Additional Classification 
Considerations 
B.8.3.1 For purposes of classification, the 
properties of self-reactive chemicals shall be determined in accordance with test series A to H as described in Part II of UN ST/SG/ AC.10 (incorporated by reference; see § 1910.6). 
B.8.3.2 Self-accelerating decomposition 
temperature (SADT) shall be determined in accordance with Part II, section 28 of UN ST/ SG/AC.10, (incorporated by reference; see § 1910.6). 
B.8.3.3 The classification procedures for 
self-reactive substances and mixtures need not be applied if: 
(a) There are no chemical groups present 
in the molecule associated with explosive or self-reactive properties; examples of such groups are given in Tables A6.1 and A6.2 in the Appendix 6 of UN ST/SG/AC.10 (incorporated by reference; see § 1910.6); or 
(b) For a single organic substance or a 
homogeneous mixture of organic substances, the estimated SADT is greater than 75 °C 
(167 °F) or the exothermic decomposition 
energy is less than 300 J/g. The onset temperature and decomposition energy may 
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be estimated using a suitable calorimetric 
technique (See 20.3.3.3 in Part II of UN ST/ SG/AC.10 (incorporated by reference; see § 1910.6)). B.9 Pyrophoric Liquids 
B.9.1 Definition 
Pyrophoric liquid means a liquid which, 
even in small quantities, is liable to ignite 
within five minutes after coming into contact with air. B.9.2 Classification Criteria 
A pyrophoric liquid shall be classified in 
a single category for this class using test N.3 
in Part III, sub-section 33.3.1.5 of UN ST/SG/ AC.10 (incorporated by reference; see § 1910.6), in accordance with Table B.9.1 of this appendix: 
TABLE B.9.1— C RITERIA FOR PYROPHORIC LIQUIDS  
Category Criteria 
1 .............................. The liquid ignites within 5 min when added to an inert carrier and exposed to air, or it ignites or chars a filter paper on 
contact with air within 5 min. 
B.9.3 Additional Classification 
Considerations 
The classification procedure for pyrophoric 
liquids need not be applied when experience 
in production or handling shows that the chemical does not ignite spontaneously on coming into contact with air at normal temperatures (i.e., the substance is known to be stable at room temperature for prolonged 
periods of time (days)). 
B.10 Pyrophoric Solids B.10.1 Definition 
Pyrophoric solid means a solid which, even 
in small quantities, is liable to ignite within 
five minutes after coming into contact with air. B.10.2 Classification Criteria 
A pyrophoric solid shall be classified in a 
single category for this class using test N.2 in 
Part III, sub-section 33.3.1.4 of UN ST/SG/ AC.10 (incorporated by reference; see § 1910.6), in accordance with Table B.10.1 of this appendix: 
TABLE B.10.1— C RITERIA FOR PYROPHORIC SOLIDS  
Category Criteria 
1 .............................. The solid ignites within 5 min of coming into contact with air. 
Note: Classification of solid chemicals 
shall be based on tests performed on the 
chemical as presented. If, for example, for the purposes of supply or transport, the same chemical is to be presented in a physical form different from that which was tested and which is considered likely to materially alter its performance in a classification test, classification must be based on testing of the chemical in the new form. 
B.10.3 Additional Classification 
Considerations 
The classification procedure for pyrophoric 
solids need not be applied when experience in production or handling shows that the chemical does not ignite spontaneously on coming into contact with air at normal temperatures (i.e., the chemical is known to 
be stable at room temperature for prolonged periods of time (days)). 
B.11—Self-Heating Chemicals B.11.1 Definition 
A self-heating chemical is a solid or liquid 
chemical, other than a pyrophoric liquid or 
solid, which, by reaction with air and without energy supply, is liable to self-heat; this chemical differs from a pyrophoric liquid or solid in that it will ignite only when in large amounts (kilograms) and after long periods of time (hours or days). 
Note: Self-heating of a substance or 
mixture is a process where the gradual reaction of that substance or mixture with oxygen (in air) generates heat. If the rate of heat production exceeds the rate of heat loss, then the temperature of the substance or mixture will rise which, after an induction time, may lead to self-ignition and combustion. 
B.11.2 Classification Criteria 
B.11.2.1 A self-heating chemical shall be 
classified in one of the two categories for this 
class if, in tests performed in accordance with test method N.4 in Part III, sub-section 33.3.1.6 of UN ST/SG/AC.10 (incorporated by reference, see § 1910.6), the result meets the criteria shown in Table B.11.1. 
TABLE B.11.1— C RITERIA FOR SELF- 
HEATING CHEMICALS  
Category Criteria 
1 ........... A positive result is obtained in a 
test using a 25 mm sample cube at 140 ° C (284 ° F). 
2 ........... A negative result is obtained in a 
test using a 25 mm cube sample at 140 ° C (284 ° F), a positive 
result is obtained in a test using a 100 mm sample cube at 140 °C (284 ° F), and: 
(a) The unit volume of the 
chemical is more than 3 m3; or 
(b) A positive result is ob-
tained in a test using a 100 mm cube sample at 120 ° C 
(248 °F) and the unit vol-
ume of the chemical is more than 450 liters; or 
(c) A positive result is ob-
tained in a test using a 100 mm cube sample at 100 ° C 
(212 °F). Note: Classification of solid chemicals 
shall be based on tests performed on the 
chemical as presented. If, for example, for the purposes of supply or transport, the same chemical is to be presented in a physical form different from that which was tested and which is considered likely to materially alter its performance in a classification test, classification must be based on testing of the chemical in the new form. 
B.11.2.2 Chemicals with a temperature of 
spontaneous combustion higher than 50 ° C 
(122 °F) for a volume of 27 m3 shall not be 
classified as self-heating chemicals. 
B.11.2.3 Chemicals with a spontaneous 
ignition temperature higher than 50° C 
(122° F) for a volume of 450 liters shall not 
be classified in Category 1 of this class. 
B.11.3 Additional Classification 
Considerations 
B.11.3.1 The classification procedure for 
self-heating chemicals need not be applied if 
the results of a screening test can be adequately correlated with the classification test and an appropriate safety margin is applied. 
B.11.3.2 Examples of screening tests are: (a) The Grewer Oven test (VDI guideline 
2263, part 1, 1990, Test methods for the Determination of the Safety Characteristics of Dusts) with an onset temperature 80 °K above 
the reference temperature for a volume of 1 l; 
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(b) The Bulk Powder Screening Test 
(Gibson, N. Harper, D. J. Rogers, R. 
Evaluation of the fire and explosion risks in drying powders, Plant Operations Progress, 4 (3), 181–189, 1985) with an onset temperature 60°K above the reference temperature for a volume of 1 l. 
B.12 Chemicals Which, in Contact With 
Water, Emit Flammable Gases 
B.12.1 Definition 
Chemicals which, in contact with water, 
emit flammable gases are solid or liquid 
chemicals which, by interaction with water, are liable to become spontaneously flammable or to give off flammable gases in dangerous quantities. 
B.12.2 Classification Criteria 
B.12.2.1 A chemical which, in contact 
with water, emits flammable gases shall be 
classified in one of the three categories for this class, using test N.5 in Part III, sub- section 33.4.1.4 of UN ST/SG/AC.10 (incorporated by reference, see § 1910.6), in accordance with Table B.12.1 of this appendix: 
TABLE B.12.1— C RITERIA FOR CHEMI-
CALS WHICH, INCONTACT WITH 
WATER , EMITFLAMMABLE GASES  
Category Criteria 
1 ........... Any chemical which, in the 1:1 
mixture, by mass, of chemical and cellulose tested, spontane-ously ignites; or the mean pres-sure rise time of a 1:1 mixture, by mass, of chemical and cel-lulose is less than that of a 1:1 mixture, by mass, of 50% per-chloric acid and cellulose; 
2 ........... Any chemical which, in the 1:1 
mixture, by mass, of chemical and cellulose tested, exhibits a mean pressure rise time less than or equal to the mean pres-sure rise time of a 1:1 mixture, by mass, of 40% aqueous so-dium chlorate solution and cel-lulose; and the criteria for Cat-egory 1 are not met; 
3 ........... Any chemical which, in the 1:1 
mixture, by mass, of chemical and cellulose tested, exhibits a mean pressure rise time less than or equal to the mean pres-sure rise time of a 1:1 mixture, by mass, of 65% aqueous nitric acid and cellulose; and the cri-teria for Categories 1 and 2 are not met. 
Note: Classification of solid chemicals 
shall be based on tests performed on the chemical as presented. If, for example, for the 
purposes of supply or transport, the same chemical is to be presented in a physical form different from that which was tested and which is considered likely to materially alter its performance in a classification test, classification must be based on testing of the chemical in the new form. 
B.12.2.2 A chemical is classified as a 
chemical which, in contact with water, emits 
flammable gases if spontaneous ignition takes place in any step of the test procedure. 
B.12.3 Additional Classification 
Considerations 
The classification procedure for this class 
need not be applied if: 
(a) The chemical structure of the chemical 
does not contain metals or metalloids; 
(b) Experience in production or handling 
shows that the chemical does not react with 
water, (e.g., the chemical is manufactured with water or washed with water); or 
(c) The chemical is known to be soluble in 
water to form a stable mixture. 
B.13 Oxidizing Liquids B.13.1 Definition 
Oxidizing liquid means a liquid which, 
while in itself not necessarily combustible, 
may, generally by yielding oxygen, cause, or contribute to, the combustion of other material. 
B.13.2 Classification Criteria 
An oxidizing liquid shall be classified in 
one of the three categories for this class using 
test O.2 in Part III, sub-section 34.4.2 of UN ST/SG/AC.10 (incorporated by reference, see § 1910.6), in accordance with Table B.13.1: 
TABLE B.13.1— C RITERIA FOR  
OXIDIZING LIQUIDS  
Category Criteria 
1 ........... Any chemical which, in the 1:1 
mixture, by mass, of chemical 
and cellulose tested, spontane-ously ignites; or the mean pres-sure rise time of a 1:1 mixture, by mass, of chemical and cel-lulose is less than that of a 1:1 mixture, by mass, of 50% per-chloric acid and cellulose; 
2 ........... Any chemical which, in the 1:1 
mixture, by mass, of chemical and cellulose tested, exhibits a mean pressure rise time less than or equal to the mean pres-sure rise time of a 1:1 mixture, by mass, of 40% aqueous so-dium chlorate solution and cel-lulose; and the criteria for Cat-egory 1 are not met; TABLE B.13.1— C RITERIA FOR  
OXIDIZING LIQUIDS —Continued 
Category Criteria 
3 ........... Any chemical which, in the 1:1 
mixture, by mass, of chemical and cellulose tested, exhibits a mean pressure rise time less than or equal to the mean pres-sure rise time of a 1:1 mixture, by mass, of 65% aqueous nitric acid and cellulose; and the cri-teria for Categories 1 and 2 are not met. 
B.13.3 Additional Classification Considerations 
B.13.3.1 For organic chemicals, the 
classification procedure for this class shall not be applied if: 
(a) The chemical does not contain oxygen, 
fluorine or chlorine; or 
(b) The chemical contains oxygen, fluorine 
or chlorine and these elements are chemically bonded only to carbon or hydrogen. 
B.13.3.2 For inorganic chemicals, the 
classification procedure for this class shall not be applied if the chemical does not contain oxygen or halogen atoms. 
B.13.3.3 In the event of divergence 
between test results and known experience in the handling and use of chemicals which shows them to be oxidizing, judgments based on known experience shall take precedence over test results. 
B.13.3.4 In cases where chemicals 
generate a pressure rise (too high or too low), caused by chemical reactions not characterizing the oxidizing properties of the chemical, the test described in Part III, sub- section 34.4.2 of UN ST/SG/AC.10 (incorporated by reference, see § 1910.6) shall be repeated with an inert substance ( e.g., 
diatomite (kieselguhr)) in place of the cellulose in order to clarify the nature of the reaction. 
B.14 Oxidizing Solids B.14.1 Definition 
Oxidizing solid means a solid which, while 
in itself is not necessarily combustible, may, 
generally by yielding oxygen, cause, or contribute to, the combustion of other material. 
B.14.2 Classification Criteria 
An oxidizing solid shall be classified in 
one of the three categories for this class using 
test O.1 in Part III, sub-section 34.4.1, of UN ST/SG/AC.10 (incorporated by reference, see § 1910.6) or test O.3 in Part III, sub-section 34.4.3 of UN ST/SG/AC.10/11 (incorporated by reference, see § 1910.6), in accordance with Table B.14.1: 
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TABLE B.14.1—C RITERIA FOR OXIDIZING SOLIDS  
Category Criteria using test O.1 Criteria using test O.3 
1 ....................... Any chemical which, in the 4:1 or 1:1 sample-to-cellulose 
ratio (by mass) tested, exhibits a mean burning time less 
than the mean burning time of a 3:2 mixture, (by mass), of potassium bromate and cellulose.Any chemical which, in the 4:1 or 1:1 sample-to- cellulose 
ratio (by mass) tested, exhibits a mean burning rate greater than the mean burning rate of a 3:1 mixture (by mass) of calcium peroxide and cellulose. 
2 ....................... Any chemical which, in the 4:1 or 1:1 sample-to-cellulose 
ratio (by mass) tested, exhibits a mean burning time equal to or less than the mean burning time of a 2:3 mixture (by mass) of potassium bromate and cellulose and the criteria for Category 1 are not met.Any chemical which, in the 4:1 or 1:1 sample-to- cellulose 
ratio (by mass) tested, exhibits a mean burning rate equal to or greater than the mean burning rate of a 1:1 mixture (by mass) of calcium peroxide and cellulose and the criteria for Category 1 are not met. 
3 ....................... Any chemical which, in the 4:1 or 1:1 sample-to-cellulose 
ratio (by mass) tested, exhibits a mean burning time equal to or less than the mean burning time of a 3:7 mixture (by mass) of potassium bromate and cellulose and the criteria for Categories 1 and 2 are not met.Any chemical which, in the 4:1 or 1:1 sample-to- cellulose 
ratio (by mass) tested, exhibits a mean burning rate equal to or greater than the mean burning rate of a 1:2 mixture (by mass) of calcium peroxide and cellulose and the criteria for Categories 1 and 2 are not met. 
Note 1: Some oxidizing solids may present 
explosion hazards under certain conditions 
(e.g., when stored in large quantities). For example, some types of ammonium nitrate may give rise to an explosion hazard under extreme conditions and the ‘‘Resistance to detonation test’’ (International Maritime Solid Bulk Cargoes Code, IMO (IMSBC), Appendix 2, Section 5) may be used to assess this hazard. When information indicates that an oxidizing solid may present an explosion hazard, it shall be indicated on the Safety Data Sheet. 
Note 2: Classification of solid chemicals 
shall be based on tests performed on the 
chemical as presented. If, for example, for the purposes of supply or transport, the same chemical is to be presented in a physical form different from that which was tested and which is considered likely to materially alter its performance in a classification test, classification must be based on testing of the chemical in the new form. 
B.14.3 Additional Classification 
Considerations 
B.14.3.1 For organic chemicals, the 
classification procedure for this class shall not be applied if: (a) The chemical does not contain oxygen, 
fluorine or chlorine; or 
(b) The chemical contains oxygen, fluorine 
or chlorine and these elements are 
chemically bonded only to carbon or 
hydrogen. 
B.14.3.2 For inorganic chemicals, the 
classification procedure for this class shall not be applied if the chemical does not contain oxygen or halogen atoms. 
B.14.3.3 In the event of divergence 
between test results and known experience in the handling and use of chemicals which shows them to be oxidizing, judgements based on known experience shall take procedure over test results. 
B.15 Organic Peroxides B.15.1 Definition 
B.15.1.1 Organic peroxide means a liquid 
or solid organic chemical which contains the 
bivalent -0-0- structure and as such is considered a derivative of hydrogen peroxide, where one or both of the hydrogen atoms have been replaced by organic radicals. The term organic peroxide includes organic peroxide mixtures containing at least one organic peroxide. Organic peroxides are thermally unstable chemicals, which may undergo exothermic self-accelerating 
decomposition. In addition, they may have one or more of the following properties: 
(a) Be liable to explosive decomposition; (b) Burn rapidly; (c) Be sensitive to impact or friction; (d) React dangerously with other 
substances. 
B.15.1.2 An organic peroxide is regarded 
as possessing explosive properties when in laboratory testing the formulation is liable to detonate, to deflagrate rapidly or to show a violent effect when heated under confinement. 
B.15.2 Classification Criteria 
B.15.2.1 Any organic peroxide shall be 
considered for classification in this class, 
unless it contains: 
(a) Not more than 1.0% available oxygen 
from the organic peroxides when containing not more than 1.0% hydrogen peroxide; or 
(b) Not more than 0.5% available oxygen 
from the organic peroxides when containing more than 1.0% but not more than 7.0% hydrogen peroxide. 
Note: The available oxygen content (%) of 
an organic peroxide mixture is given by the 
formula: 
where: 
ni = number of peroxygen groups per 
molecule of organic peroxide i; 
ci = concentration (mass %) of organic 
peroxide i; 
mi = molecular mass of organic peroxide i. 
B.15.2.2 Organic peroxides shall be 
classified in one of the seven categories of 
‘‘Types A to G’’ for this class, according to the following principles: 
(a) Any organic peroxide which, as 
packaged, can detonate or deflagrate rapidly 
shall be defined as organic peroxide TYPE A; 
(b) Any organic peroxide possessing 
explosive properties and which, as packaged, neither detonates nor deflagrates rapidly, but is liable to undergo a thermal explosion in that package shall be defined as organic 
peroxide TYPE B; 
(c) Any organic peroxide possessing 
explosive properties when the chemical as packaged cannot detonate or deflagrate rapidly or undergo a thermal explosion shall be defined as organic peroxide TYPE C; 
(d) Any organic peroxide which in 
laboratory testing meets the criteria in (d)(i), (ii), or (iii) shall be defined as organic peroxide TYPE D: 
(i) Detonates partially, does not deflagrate 
rapidly and shows no violent effect when heated under confinement; or 
(ii) Does not detonate at all, deflagrates 
slowly and shows no violent effect when heated under confinement; or (iii) Does not detonate or deflagrate at all 
and shows a medium effect when heated 
under confinement; 
(e) Any organic peroxide which, in 
laboratory testing, neither detonates nor deflagrates at all and shows low or no effect when heated under confinement shall be defined as organic peroxide TYPE E; 
(f) Any organic peroxide which, in 
laboratory testing, neither detonates in the cavitated state nor deflagrates at all and shows only a low or no effect when heated under confinement as well as low or no explosive power shall be defined as organic peroxide TYPE F; 
(g) Any organic peroxide which, in 
laboratory testing, neither detonates in the cavitated state nor deflagrates at all and shows no effect when heated under 
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10Phlegmatized means that a substance (or 
‘‘phlegmatizer’’) has been added to an explosive to 
enhance its safety in handling and transport. The phlegmatizer renders the explosive insensitive, or less sensitive, to the following actions: heat, shock, impact, percussion or friction. Typical 
phlegmatizing agents include, but are not limited to: wax, paper, water, polymers (such as chlorofluoropolymers), alcohol and oils (such as 
petroleum jelly and paraffin). 
11Unstable explosives as defined in Chapter B.1 
can also be stabilized by desensitization and consequently may be re-classified as desensitized explosives, provided all criteria of Chapter B.17 are met. In this case, the desensitized explosive should be tested according to Test Series 3 (Part I of UN ST/SG/AC.10/11/Rev. 6 (incorporated by reference, see § 1910.6)) because information about its sensitiveness to mechanical stimuli is likely to be important for determining conditions for safe handling and use. The results shall be communicated on the safety data sheet. confinement nor any explosive power, 
provided that it is thermally stable (self- accelerating decomposition temperature is 60 °C (140 ° F) or higher for a 50 kg (110 lb) 
package), and, for liquid mixtures, a diluent having a boiling point of not less than 150 ;°C (302 ° F) is used for desensitization, shall 
be defined as organic peroxide TYPE G. If the organic peroxide is not thermally stable or a diluent having a boiling point less than 150 °C (302° F) is used for desensitization, it shall 
be defined as organic peroxide TYPE F. 
B.15.3 Additional Classification 
Considerations 
B.15.3.1 For purposes of classification, 
the properties of organic peroxides shall be 
determined in accordance with test series A 
to H as described in Part II of UN ST/SG/ AC.10 (incorporated by reference, see § 1910.6). 
B.15.3.2 Self-accelerating decomposition 
temperature (SADT) shall be determined in accordance with UN ST/SG/AC.10 (incorporated by reference, see § 1910.6), Part II, section 28. 
B.15.3.3 Mixtures of organic peroxides 
may be classified as the same type of organic peroxide as that of the most dangerous ingredient. However, as two stable ingredients can form a thermally less stable mixture, the SADT of the mixture shall be determined. 
B.16 Corrosive to Metals B.16.1 Definition 
A chemical which is corrosive to metals 
means a chemical which by chemical action 
will materially damage, or even destroy, metals. 
B.16.2 Classification Criteria 
A chemical which is corrosive to metals 
shall be classified in a single category for this 
class, using the test in Part III, sub-section 37.4 of UN ST/SG/AC.10 (incorporated by reference, see § 1910.6), in accordance with Table B.16.1: TABLE B.16.1—C RITERIA FOR  
CHEMICALS CORROSIVE TO METAL 
Category Criteria 
1 ........... Corrosion rate on either steel or 
aluminum surfaces exceeding 
6.25 mm per year at a test tem-perature of 55 ° C (131 ° F) 
when tested on both materials. 
Note: Where an initial test on either steel 
or aluminium indicates the chemical being 
tested is corrosive the follow-up test on the other metal is not necessary. 
B.16.3 Additional Classification 
Considerations 
The specimen to be used for the test shall 
be made of the following materials: 
(a) For the purposes of testing steel, steel 
types S235JR+CR (1.0037 resp. St 37- 2), 
S275J2G3+CR (1.0144 resp. St 44–3), ISO 3574, Unified Numbering System (UNS) G 10200, or SAE 1020; 
(b) For the purposes of testing aluminium: 
non-clad types 7075–T6 or AZ5GU–T6. 
B.17 Desensitized Explosives B.17.1 Definitions and General 
Considerations 
Desensitized explosives are solid or liquid 
explosive chemicals which are 
phlegmatized
10to suppress their explosive 
properties in such a manner that they do not mass explode and do not burn too rapidly and therefore may be exempted from the hazard class ‘‘Explosives’’ (Chapter B.1; see also Note 2 of paragraph B.1.3).
11 
B.17.1.1 The class of desensitized 
explosives comprises: 
(a) Solid desensitized explosives: explosive 
substances or mixtures which are wetted with water or alcohols or are diluted with other substances, to form a homogeneous solid mixture to suppress their explosive properties. Note: This includes desensitization 
achieved by formation of hydrates of the 
substances. 
(b) Liquid desensitized explosives: 
explosive substances or mixtures which are dissolved or suspended in water or other liquid substances, to form a homogeneous liquid mixture to suppress their explosive properties. 
B.17.2 Classification Criteria 
B.17.2.1 Any explosive which is 
desensitized shall be considered in this class, 
unless: 
(a) It is intended to produce a practical, 
explosive or pyrotechnic effect; or 
It has a mass explosion hazard according 
to test series 6 (a) or 6 (b) or its corrected 
burning rate according to the burning rate test described in part V, subsection 51.4 of UN ST/SG/AC.10/11/Rev.6 (incorporated by reference, see § 1910.6) is greater than 1200 kg/min; or 
(b) Its exothermic decomposition energy is 
less than 300 J/g. 
Note 1: Substances or mixtures which meet 
the criterion (a) or (b) shall be classified as explosives (see Chapter B.1). Substances or mixtures which meet the criterion (c) may fall within the scope of other physical hazard classes. 
Note 2: The exothermic decomposition 
energy may be estimated using a suitable calorimetric technique (see section 20, sub- section 20.3.3.3 in Part II of UN ST/SG/ AC.10/11/Rev.6 (incorporated by reference, see § 1910.6). 
B.17.2.2 Desensitized explosives shall be 
classified in one of the four categories of this class depending on the corrected burning rate (Ac) using the test ‘‘burning rate test (external fire)’’ described in Part V, sub-section 51.4 of UN ST/SG/AC.10/11/Rev.6 (incorporated by reference, see § 1910.6), according to Table B.17.1: 
TABLE B.17.1—C RITERIA FOR DESENSITIZED EXPLOSIVES  
Category Criteria 
1 ........................ Desensitized explosives with a corrected burning rate (AC) equal to or greater than 300 kg/min but not more than 1200 kg/ 
min. 
2 ........................ Desensitized explosives with a corrected burning rate (AC) equal to or greater than 140 kg/min but less than 300 kg/min. 
3 ........................ Desensitized explosives with a corrected burning rate (AC) equal to or greater than 60 kg/min but less than 140 kg/min. 
4 ........................ Desensitized explosives with a corrected burning rate (AC) less than 60 kg/min. 
Note 1: Desensitized explosives shall be 
prepared so that they remain homogeneous 
and do not separate during normal storage 
and handling, particularly if desensitized by wetting. The manufacturer, importer, or distributor shall provide information in Section 10 of the safety data sheet about the shelf-life and instructions on verifying 
desensitization. Under certain conditions the content of desensitizing agent (e.g., 
phlegmatizer, wetting agent or treatment) may decrease during supply and use, and thus, the hazard potential of the desensitized explosive may increase. In addition, Sections 5 and/or 8 of the safety data sheet shall 
include advice on avoiding increased fire, blast or protection hazards when the 
chemical is not sufficiently desensitized. 
Note 2: Explosive properties of 
desensitized explosives shall be determined using data from Test Series 2 of UN ST/SG/ 
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AC.10/11/Rev.6 (incorporated by reference, 
see § 1910.6) and shall be communicated in the safety data sheet. For testing of liquid desensitized explosives, refer to section 32, sub-section 32.3.2 of UN ST/SG/AC.10/11/ Rev.6 (incorporated by reference, see 1910.6). Testing of solid desensitized explosives is addressed in section 33, sub-section 33.2.3 of UN ST/SG/AC.10/11/Rev.6 (incorporated by reference, see § 1910.6). 
Note 3: Desensitized explosives do not fall 
additionally within the scope of chapters B.1 (explosives), B.6 (flammable liquids) and B.7 (flammable solids). 
B.17.3 Additional Classification 
Considerations 
B.17.3.1 The classification procedure for 
desensitized explosives does not apply if: 
(a) The substances or mixtures contain no 
explosives according to the criteria in 
Chapter B.1; or 
(b) The exothermic decomposition energy 
is less than 300 J/g. 
B.17.3.2 The exothermic decomposition 
energy shall be determined using the 
explosive already desensitized (i.e., the 
homogenous solid or liquids mixture formed by the explosive and the substance(s) used to suppress its explosive properties). The exothermic decomposition energy may be estimated using a suitable calorimetric technique (see Section 20, sub-section 
20.3.3.3 in Part II of UN ST/SG/AC.10/11/ Rev. 6 (incorporated by reference, see § 1910.6). Appendix C to § 1910.1200—Allocation of Label Elements 
(Mandatory) 
C.1 The label for each hazardous 
chemical shall include the product identifier 
used on the safety data sheet. 
C.1.1 The labels on shipped containers 
shall also include the name, address, and telephone number of the chemical manufacturer, importer, or responsible party. 
C.2 The label for each hazardous 
chemical that is classified shall include the signal word, hazard statement(s), pictogram(s), and precautionary statement(s) specified in C.4 for each hazard class and associated hazard category, except as provided for in C.2.1 through C.2.4. 
C.2.1 Precedence of Hazard Information 
C.2.1.1 If the signal word ‘‘Danger’’ is 
included, the signal word ‘‘Warning’’ shall 
not appear; 
C.2.1.2 If the skull and crossbones 
pictogram is included, the exclamation mark pictogram shall not appear where it is used for acute toxicity; 
C.2.1.3 If the corrosive pictogram is 
included, the exclamation mark pictogram shall not appear where it is used for skin or 
eye irritation; 
C.2.1.4 If the health hazard pictogram is 
included for respiratory sensitization, the exclamation mark pictogram shall not appear where it is used for skin sensitization or for skin or eye irritation. C.2.2 Hazard Statement Text 
C.2.2.1 The text of all applicable hazard 
statements shall appear on the label, except 
as otherwise specified. The information in italics shall be included as part of the hazard statement as provided. For example: ‘‘causes damage to organs (state all organs affected) through prolonged or repeated exposure (state route of exposure if no other routes of exposure cause the hazard)’’. Hazard statements may be combined where appropriate to reduce the information on the label and improve readability, as long as all of the hazards are conveyed as required. 
C.2.2.2 If the chemical manufacturer, 
importer, or responsible party can demonstrate that all or part of the hazard statement is inappropriate to a specific substance or mixture, the corresponding statement may be omitted from the label. 
C.2.3 Pictograms 
C.2.3.1 Pictograms shall be in the shape 
of a square set at a point and shall include 
a black hazard symbol on a white background with a red frame sufficiently wide to be clearly visible. A square red frame set at a point without a hazard symbol is not a pictogram and is not permitted on the label. 
C.2.3.2 One of eight standard hazard 
symbols shall be used in each pictogram. The eight hazard symbols are depicted in Figure C.1. A pictogram using the exclamation mark symbol is presented in Figure C.2, for the purpose of illustration. 
Figure C.1—Hazard Symbols and Classes 
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Figure C.2—Exclamation Mark Pictogram 
C.2.3.3 The exclamation mark pictogram 
is permitted (but not required) for HNOCs as 
long as the words ‘‘Hazard Not Otherwise Classified’’ or the letters ‘‘HNOC’’ appear below the pictogram. 
C.2.3.4 Pictograms may only appear once 
on a label. If multiple hazards require the use of the same pictogram, it may not appear a second time on the label. 
C.2.4 Precautionary Statement Text 
C.2.4.1 There are four types of 
precautionary statements presented, 
‘‘prevention,’’ ‘‘response,’’ ‘‘storage,’’ and ‘‘disposal.’’ The core part of the precautionary statement is presented in bold print. This is the text, except as otherwise specified, that shall appear on the label. Where additional information is required, it is indicated in plain text. 
C.2.4.2 When a backslash or diagonal 
mark (/) appears in the precautionary statement text, it indicates that a choice has to be made between the separated phrases. In such cases, the chemical manufacturer, importer, or responsible party can choose the most appropriate phrase(s). For example, ‘‘Wear protective gloves/protective clothing/ eye protection/face protection’’ could read ‘‘wear eye protection’’. 
C.2.4.3 When three full stops (. . .) 
appear in the precautionary statement text, they indicate that all applicable conditions are not listed. For example, in ‘‘Use explosion-proof electrical/ventilating/ lighting/. . ./equipment’’, the use of ‘‘. . .’’ indicates that other equipment may need to be specified. In such cases, the chemical manufacturer, importer, or responsible party can choose the other conditions to be specified. 
C.2.4.4 When text in italics is used in a 
precautionary statement, this indicates specific conditions applying to the use or allocation of the precautionary statement. For example, ‘‘Use explosion-proof electrical/ ventilating/lighting/. . ./equipment’’ is only required for flammable solids ‘‘if dust clouds can occur’’. Text in italics is intended to be an explanatory, conditional note and is not intended to appear on the label. 
C.2.4.5 Where square brackets ([ ]) appear 
around text in a precautionary statement, this indicates that the text in square brackets is not appropriate in every case and should be used only in certain circumstances. In these cases, conditions for use explaining when the text should be used are provided. For 
example, one precautionary statement states: ‘‘[In case of inadequate ventilation] wear respiratory protection.’’ This statement is given with the condition for use ‘‘– text in square brackets may be used if additional information is provided with the chemical at the point of use that explains what type of ventilation would be adequate for safe use’’. This means that, if additional information is provided with the chemical explaining what type of ventilation would be adequate for safe use, the text in square brackets should be used and the statement would read: ‘‘In case of inadequate ventilation wear respiratory protection.’’ However, if the chemical is supplied without such ventilation information, the text in square brackets should not be used, and the precautionary statement should read: ‘‘Wear respiratory protection.’’ 
C.2.4.6 Precautionary statements may be 
combined or consolidated to save label space and improve readability. For example, ‘‘Keep away from heat, sparks and open flame,’’ ‘‘Store in a well-ventilated place’’ and ‘‘Keep cool’’ can be combined to read ‘‘Keep away from heat, sparks and open flame and store in a cool, well-ventilated place.’’ 
C.2.4.7 Precautionary statements may 
incorporate minor textual variations from the text prescribed in this Appendix if these variations assist in communicating safety information (e.g., spelling variations, synonyms or other equivalent terms) and the safety advice is not diluted or compromised. Any variations must be used consistently on the label and the safety data sheet. 
C.2.4.8 In most cases, the precautionary 
statements are independent (e.g., the phrases for explosives hazards do not modify those 
related to certain health hazards, and 
products that are classified for both hazard classes shall bear appropriate precautionary 
statements for both). Where a chemical is classified for a number of hazards, and the precautionary statements are similar, the most stringent shall be included on the label (this will be applicable mainly to preventive measures). 
C.2.4.9 If the chemical manufacturer, 
importer, or responsible party can demonstrate that a precautionary statement is inappropriate to a specific substance or mixture, the precautionary statement may be omitted from the label. 
C.2.4.10 Where a substance or mixture is 
classified for a number of health hazards, this may trigger multiple precautionary 
statements relating to medical response, e.g., 
calling a poison center/doctor/. . . and getting medical advice/attention. 
In general, the following principles should 
be applied: 
(a) Where the classification of a substance 
or mixture triggers several different precautionary statements, a system of prioritization should be applied. If the same medical response statement is triggered multiple times, the label need only include one precautionary statement reflecting the response at the highest level with the greatest urgency, which should always be combined with at least one route of exposure or symptom ‘‘IF’’ statement. 
(b) Routes of exposure, including ‘‘IF 
exposed or concerned,’’ may be combined when triggered with a medical response statement. If the response statement is triggered with three or more routes of exposure, ‘‘IF exposed or concerned’’ may be used. However, relevant ‘‘IF’’ statements describing symptoms must be included in full. If a route of exposure is triggered multiple times, it need only be included once. 
(c) This does not apply to ‘‘Get medical 
advice/attention if you feel unwell’’ or ‘‘Get immediate medical advice/attention’’ when they are combined with an ‘‘If’’ statement and must appear without prioritization. 
C.3 Supplementary Hazard Information 
C.3.1 To ensure that non-standardized 
information does not lead to unnecessarily 
wide variation or undermine the required information, supplementary information on the label is limited to when it provides further detail and does not contradict or cast doubt on the validity of the standardized hazard information. 
C.3.2 Where the chemical manufacturer, 
importer, or distributor chooses to add supplementary information on the label, the placement of supplemental information shall not impede identification of information required by this section. 
C.3.3 Where an ingredient with unknown 
acute toxicity is used in a mixture at a concentration ≥1%, and the mixture is not 
classified based on testing of the mixture as a whole, a statement that X% of the mixture consists of ingredient(s) of unknown acute toxicity (oral/dermal/inhalation) is required on the label and safety data sheet. 
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C.4 Requirements for Signal Words, 
Hazard Statements, Pictograms, and Precautionary Statements 
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Appendix D to § 1910.1200—Safety Data 
Sheets (Mandatory) 
A safety data sheet (SDS) shall include the 
information specified in Table D.1 under the 
section number and heading indicated for sections 1–11 and 16. While each section of 
the SDS must contain all of the specified information, preparers of safety data sheets are not required to present the information in any particular order within each section. If 
no relevant information is found for any given subheading within a section, the SDS 
shall clearly indicate that no applicable information is available. Sections 12–15 may be included in the SDS, but are not mandatory. 
TABLE D.1—M INIMUM INFORMATION FOR AN SDS 
Headings Subheadings 
1. Identification ........................................ (a) Product identifier used on the label; 
(b) Other means of identification; 
(c) Recommended use of the chemical and restrictions on use; 
(d) Name, U.S. address, and U.S. telephone number of the chemical manufacturer, importer, or other 
responsible party; 
(e) Emergency phone number. 
2. Hazard Identification ............................ (a) Classification of the chemical in accordance with paragraph (d)(1)(i) of § 1910.1200; 
(b) Signal word, hazard statement(s), symbol(s) and precautionary statement(s) in accordance with 
paragraph (f) of § 1910.1200. (Hazard symbols may be provided as graphical reproductions in 
black and white or the name of the symbol, e.g., flame, skull and crossbones); 
(c) Hazards classified under paragraph (d)(1)(ii) of § 1910.12000; 
(d) Describe any hazards not otherwise classified that have been identified during the classification 
process; 
(e) Where an ingredient with unknown acute toxicity is used in a mixture at a concentration ≥1% and 
the mixture is not classified based on testing of the mixture as a whole, a statement that X% of the mixture consists of ingredient(s) of unknown acute toxicity is required. 
3. Composition/information on ingredi-
ents.Except as provided for in paragraph (i) of § 1910.1200 on trade secrets: 
For Substances 
(a) Chemical name; 
(b) Common name and synonyms; 
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TABLE D.1—M INIMUM INFORMATION FOR AN SDS—Continued 
Headings Subheadings 
(c) CAS number and other unique identifiers; 
(d) Impurities and stabilizing additives (constituents) which are themselves classified and which con-
tribute to the classification of the substance. 
For Mixtures 
In addition to the information required for substances: 
(a) The chemical name, CAS number or other unique identifier, and concentration (exact percentage) 
or concentration ranges of all ingredients which are classified as health hazards in accordance with 
paragraph (d) of § 1910.1200 and 
(1) are present above their cut-off/concentration limits; or 
(2) present a health risk below the cut-off/concentration limits. 
Note: When CAS number is not available or claimed as a trade secret, the preparer must indicate the 
source of unique identifier. 
(b) The concentration (exact percentage) shall be specified unless a trade secret claim is made in ac-
cordance with paragraph (i) of § 1910.1200, when there is batch-to-batch variability in the produc-tion of a mixture, or for a group of substantially similar mixtures (See A.0.5.1.2) with similar chem-
ical composition. In these cases, concentration ranges may be used. 
For All Chemicals Where a Trade Secret is Claimed Where a trade secret is claimed in accordance with paragraph (i) of § 1910.1200, a statement that 
the specific chemical identity, and/or concentration (exact or range) of the composition has been withheld as a trade secret is required. When the concentration or concentration range is withheld as a trade secret, the prescribed concentration ranges used in § 1910.1200(i)(1)(iv)–(vi) must be used. 
4. First aid measures ............................... (a) Description of necessary measures, subdivided according to the different routes of exposure, i.e., 
inhalation, skin and eye contact, and ingestion; 
(b) Most important symptoms/effects, acute and delayed. 
(c) Indication of immediate medical attention and special treatment needed, if necessary. 
5. Fire-fighting measures ......................... (a) Suitable (and unsuitable) extinguishing media. 
(b) Specific hazards arising from the chemical (e.g., nature of any hazardous combustion products). 
(c) Special protective equipment and precautions for fire-fighters. 
6. Accidental release measures .............. (a) Personal precautions, protective equipment, and emergency procedures. 
(b) Methods and materials for containment and cleaning up. 
7. Handling and storage .......................... (a) Precautions for safe handling. 
(b) Conditions for safe storage, including any incompatibilities. 
8. Exposure controls/personal protection (a) For all ingredients or constituents listed in Section 3, the OSHA permissible expo sure limit (PEL), 
American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV), and any other exposure limit or range used or recommended by the chemical manufacturer, im-porter, or employer preparing the safety data sheet, where available. 
(b) Appropriate engineering controls. 
(c) Individual protection measures, such as personal protective equipment. 
9. Physical and chemical properties † ..... (a) Physical state. 
(b) Color. 
(c) Odor (includes odor threshold). 
(d) Melting point/freezing point. 
(e) Boiling point (or initial boiling point or boiling range). 
(f) Flammability. 
(g) Lower and upper explosion limit/flammability limit. 
(h) Flash point. 
(i) Auto-ignition temperature. 
(j) Decomposition temperature. 
(k) pH. 
(l) Kinematic viscosity. 
(m) Solubility. 
(n) Partition coefficient n-octanol/water (log value). 
(o) Vapor pressure (includes evaporation rate). 
(p) Density and/or relative density. 
(q) Relative vapor density. 
(r) Particle characteristics. 
10. Stability and reactivity.
(a) Reactivity; 
(b) Chemical stability; 
(c) Possibility of hazardous reactions, including those associated with foreseeable emergencies; 
(d) Conditions to avoid (e.g., static discharge, shock, or vibration); 
(e) Incompatible materials; 
(f) Hazardous decomposition products. 
11. Toxicological information ................... Description of the various toxicological (health) effects and the available data used to identify those 
effects, including: 
(a) Information on the likely routes of exposure (inhalation, ingestion, skin, and eye contact); 
(b) Symptoms related to the physical, chemical, and toxicological characteristics; 
(c) Delayed and immediate effects and also chronic effects from short- and long-term exposure; 
(d) Numerical measures of toxicity (such as acute toxicity estimates); 
(e) Interactive effects; information on interactions should be included if relevant and readily available; 
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TABLE D.1—M INIMUM INFORMATION FOR AN SDS—Continued 
Headings Subheadings 
(f) Whether the hazardous chemical is listed in the National Toxicology Program (NTP) Report on 
Carcinogens (latest edition) or has been found to be a potential carcinogen in the International 
Agency for Research on Cancer (IARC) Monographs (latest edition), or by OSHA. 
(g) When specific chemical data or information is not available, the preparer must indicate if alter-
native information is used and the method used to derive the information (e.g., where the preparer 
is using information from a class of chemicals rather than the exact chemical in question and using SAR to derive the toxicological information). 
12. Ecological information (Non-manda-
tory).(a) Ecotoxicity (aquatic and terrestrial, where available); 
(b) Persistence and degradability; 
(c) Bioaccumulative potential; 
(d) Mobility in soil; 
(e) Other adverse effects (such as hazardous to the ozone layer). 
13. Disposal considerations (Non-man-
datory).Description of waste residues and information on their safe handling and methods of disposal, includ-
ing the disposal of any contaminated packaging. 
14. Transport information (Non-manda-
tory).(a) UN number; 
(b) UN proper shipping name; 
(c) Transport hazard class(es); 
(d) Packing group, if applicable; 
(e) Environmental hazards (e.g., Marine pollutant (Yes/No)); 
(f) Transport in bulk (according to IMO instruments 
(g) Special precautions which a user needs to be aware of, or needs to comply with, in connection 
with transport or conveyance either within or outside their premises 
15. Regulatory information (Non-manda-
tory).Safety, health and environmental regulations specific for the product in question. 
16. Other information, including date of 
preparation or last revision.The date of preparation of the SDS or the last change to it. 
†Note: To determine the appropriate flammable liquid storage container size and type, the boiling point shall be determined by methods speci-
fied under § 1910.106(a)(5) and then listed on the SDS. In addition, the manufacturer, importer, and distributor shall clearly note in sections 7 
and 9 of the SDS if an alternate calculation was used for storage purposes and the classification for storage differs from the classification listed 
in section 2 of the SDS. 
[FR Doc. 2024–08568 Filed 5–17–24; 8:45 am] 
BILLING CODE 4510–26–P 
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