GHS classification for mixtures — what product makers need to know
GHS classification of a mixture is more complex than simply listing the ingredients. The UN GHS and OSHA HazCom apply concentration thresholds and, for acute toxicity, an additivity formula that combines the toxicity contributions of each ingredient based on its concentration and intrinsic hazard.
For example, skin irritation classification (Cat 2) requires the sum of concentrations of all skin irritant ingredients to reach a threshold (typically ≥10% for a Category 2 irritant). An ingredient present at 0.1% may not trigger classification on its own, even if it is classified as a skin irritant in pure form.
SDSDraft uses a simplified approach: it aggregates hazards from all listed ingredients regardless of concentration. This is conservative — the tool will tend to include hazard classifications that a proper concentration-cut-off analysis might exclude. The result is a starting draft that needs professional verification, not a substitute for proper GHS classification.
The key sections where concentration matters most: Section 2 (hazard classification), Section 3 (ingredient disclosure thresholds), and Section 11 (toxicological data). Concentration cut-offs vary by hazard class — some are as low as 0.1% (carcinogens), others as high as 10% or 20% (irritants).
SDSDraft generates a DRAFT safety data sheet from the information you enter. You are solely responsible for verifying the hazard classification and all content with a qualified person before use or distribution. SDSDraft is software, not professional safety, legal, or toxicological advice.
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What to verify in a draft classification
- Review the H-codes assigned to each ingredient at your specific concentration from the supplier SDS.
- Check whether your ingredient's concentration is above or below the GHS classification cut-off for each hazard category.
- For acute toxicity: if multiple toxic ingredients are present, apply the additivity formula (OSHA HazCom Appendix A.1) to determine if the mixture meets the toxicity threshold.
- For corrosives and serious eye damage: these classifications can apply at relatively low concentrations. Verify with your supplier SDS and a professional.
- For carcinogens and reproductive toxins: cut-offs are as low as 0.1%. If any ingredient is classified for these hazards, verify whether your concentration triggers the classification.
- For aquatic hazards: additivity applies across all contributing ingredients. Even low concentrations of highly toxic aquatic hazard ingredients can contribute.
Questions
What are typical concentration cut-offs for GHS mixture classification?
They vary by hazard class. For skin irritation, the cut-off is typically ≥10% sum of irritants. For serious eye damage, ≥10% of Cat 1 eye damage ingredients. For skin sensitisation, ≥0.1% for strong sensitisers (Sub-category 1A), ≥1% for others. For carcinogens, ≥0.1% for Cat 1A/1B, ≥1% for Cat 2. These are the starting generic cut-offs — specific substances may have different cut-offs based on evidence.
Does SDSDraft apply these cut-offs?
No. SDSDraft aggregates hazards from all listed ingredients without applying concentration cut-offs. It is a conservative starting draft. To determine whether your specific formulation triggers each classification at your specific concentrations, you need to apply GHS criteria (OSHA HazCom Appendix A) or engage a professional.
What is the additivity formula for acute toxicity?
The mixture ATE (Acute Toxicity Estimate) is calculated as: 100 / ATE_mixture = sum of (Ci / ATE_i) for each ingredient i, where Ci is the concentration (%) of ingredient i and ATE_i is its ATE. If the resulting ATE_mixture falls within a GHS acute toxicity category range, the mixture is classified. This requires ingredient-level ATE data from supplier SDSs.