Fire Codes and the GHS
Part 3: Toxicity – oral and dermal exposure routes
Part 3 in our series is not just a theoretical comparison of hazard classes but a practical guide that provides code users with the necessary tools to confidently apply the 2024 IFC Appendix Table E104.2, IFC and GHS Hazard Definitions Comparison. By highlighting the differences between the IFC toxicity hazard classes and the GHS, we aim to empower you to assign applicable fire code hazard classes when the GHS hazard classes are known.
Background
OSHA’s Hazard Communication (HAZCOM) Standard (29 CFR 1910.1200) prescribes the hazard classification system manufacturers are required to use to classify and label chemicals and communicate the hazards of materials in Safety Data Sheets (SDS). Appendix Table E104.2, introduced in the 2024 IFC, presents IFC hazard classes alongside those found in HAZCOM 2012, based on Revision 3 of the GHS. A much-awaited update to the HAZCOM Standard, based on Rev. 7 (2017) of the GHS, was finalized on May 20, 2024, and takes effect on July 19, 2024.
This article compares IFC toxicity hazard classes for oral and dermal routes of exposure with GHS (Rev. 7) classifications and identifies where HAZCOM (2024) differs.
Before delving straight into the comparison, it can be helpful to review a few fundamental concepts.
Length of exposure
Acute refers to a single, short-term exposure to a substance, while chronic relates to frequent or long-term exposure effects. Fire and building codes intend to prevent and mitigate hazardous materials emergencies, so they only anticipate and address acute exposure.
Route of Exposure
Toxic chemicals typically enter the human body by three routes: contact with skin (dermal), ingestion (oral), and inhalation (inhalation). Breathing or touching a chemical can lead to exposure by one or more routes, so fire and building codes address all three.
Amount of Exposure
Another primary concept is the amount of exposure to a toxic material. In toxicology, the amount of a substance administered or adsorbed internally (orally or dermally) is a dose, and the amount of exposure by inhalation is a concentration.
LD50 values estimate the amount of a chemical that would be toxic to humans over a specified time. Model fire and building codes use LD50s to define when liquid and solid materials are ‘toxic’ or ‘highly toxic.’
LD stands for “Lethal Dose,” which is the amount of material given all at once that causes the death of 50% (one-half) of a group of test animals. Similarly, LC is short for “Lethal Concentration,” which, like the lethal dose, is the amount of material given all at once that causes the death of 50% (one-half) of a group of test animals, but the LC50 measures a material’s acute toxicity via inhalation.
Under the GHS, acute toxicity values are expressed as (approximate) LD50 (oral, dermal) values or as acute toxicity estimates (ATE). Some study methods determine LD50 values directly. Still, newer study methods (e.g., using fewer animals) consider other indicators of acute toxicity, such as significant clinical signs of toxicity in humans.
Since this article only addresses the toxicity for oral and dermal routes of exposure, we’ll discuss LC50s in more detail in our future article on the toxicity of gases, vapors, dust, and mists.
GHS & HAZCOM
You may be surprised to learn that chemicals are not required to be tested to establish applicable health hazards under the GHS or HAZCOM. Existing data and expert judgment can be used, provided the data are derived from scientifically validated test methods. Scientifically validated means the test method’s process, reliability, and relevance are standardized and established for a particular purpose. Hence, the results are reproducible with a given substance. Additionally, data and experience on the effects of chemicals on humans (e.g., occupational data, data from accident databases) must be considered in evaluating a chemical’s human health hazards.
For some chemicals, LD50 data is available to establish toxicity directly. For others, the classification might be determined based on the total weight of evidence using expert judgment. In these cases, an acute toxicity estimate, or ATE, determines how a material is classified. Either is acceptable.
Table 3.1.1 below shows how ATE (LD50) values are categorized based on oral and dermal routes of exposure under the GHS. HAZCOM classifies toxicity similarly, except Category 5 materials are not assigned a hazard class. Instead, they are identified as Hazards Not Otherwise Classified (HNOC) in Section 2.3 of the SDS.
IFC/IBC
The 2024 IFC and prior editions rely on LD50 data to establish whether a material should be classified as toxic or highly toxic. Table 4.1 below identifies how LD50 values are classified based on exposure route.
If the LD50 data for a product is not made available in Section 11 of the SDS, there are other sources of acute toxicity data, mainly for pure materials. Appendix B of Application of Modern Toxicology Approaches for Predicting Acute Toxicity for Chemical Defense1 provides a particularly good summary of available toxicity data and databases.
The Deep Dive
Taking a deep dive and directly comparing the GHS hazard categories and IFC hazard classes for acute toxicity reveals the following:
The tables above illustrate that the IFC and GHS hazard classifications align when comparing acute toxicity by dermal exposure. And any material classified in Section 2.1 of an SDS as Acute toxicity, dermal (Category 1 or 2) will be classified as highly toxic under IFC/IBC. Material classified as Acute toxicity, dermal (Category 3) is Toxic per IFC/IBC. Materials classified as Acute toxicity, dermal (Category 4 or 5) are not regulated as toxic by IFC/IBC. Further, Acute toxicity, dermal Category 5 materials may only appear as Hazards Not Otherwise Classified (HNOC) on an SDS.
On the other hand, when comparing acute toxicity by oral exposure, we find that Acute toxicity, oral (Category 1 and 2) values align perfectly with the IFC’s definition of highly toxic. Category 3 materials fall neatly within the IFC Toxic hazard class. However, Acute toxicity, oral (Category 4) materials can have LD50s or ATEs that fall outside the toxic endpoint for the IFC. Practically, that means that for materials classified as Acute toxicity, oral (Category 4) in Section 2.1 of an SDS, you need the actual LD50 data to determine if the IFC considers the material toxic.
The LD50 data for materials can be found in Section 10 of the SDS supplied by the manufacturer. One core concept often misunderstood is that the LD50 data needed to classify mixtures must reflect the entire mixture. Although there are ways to calculate and estimate LD50s for mixtures using toxicity data for each hazardous component, the LD50 data for the mixture should also be available in the SDS.
IFC Appendix Table E104.2
Referring to the new IFC Appendix Table E104.2, similar Acute toxicity Categories are identified for the IFC Toxic and Highly Toxic hazard classes. Unfortunately, the details we examined for Acute toxicity, oral (Category 4), are not noted in the Appendix Table. This is the most significant limitation of the IFC Appendix Table. While the Table is a valuable resource, the code user must analyze each definition to uncover where inconsistencies exist.
Key Takeaways
- OSHA recently updated its HAZCOM Standard, requiring chemical manufacturers to update the hazard classifications in their Safety Data Sheets (SDSs) to align with GHS Rev. 7 and some Rev. 8 classifications.
- Use 2024 IFC Table E104.2 to help navigate between the GHS/OSHA hazard classifications in Section 2.1 of SDSs and IFC hazard classes. Read closely to find nuances between the IFC hazard class definitions and GHS definitions in the Table. The differences are not red-flagged.
- The comparison table below simplifies the findings from the deep dive above for acute toxicity for oral and dermal routes of exposure. Use it to help decide if a material is toxic or highly toxic under the IFC.
Footnotes:
1 Committee on Predictive-Toxicology Approaches for Military Assessments of Acute Exposures; Committee on Toxicology; Board on Environmental Studies and Toxicology; Board on Life Sciences; Division on Earth and Life Studies; The National Academies of Sciences, Engineering, and Medicine. Washington (DC): National Academies Press (US); 2015 Sep 1.
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