GHS / HazCom term · Glossary
Acute Toxicity
Verified vs OSHA sources · 2026-10-05
A GHS health-hazard class for the harmful effects that follow a single dose, several doses within 24 hours, or a 4-hour inhalation exposure. Chemicals are sorted into categories by route (oral, dermal, inhalation) using LD50/LC50 cut-offs — Category 1 is the most toxic. OSHA's HazCom standard uses Categories 1–4.
Also known as: acute toxicity classification
Acute Toxicity at a glance
- Rated by route — oral, dermal, inhalation — each with its own cut-offs.
- Five GHS categories by toxicity; OSHA's HazCom adopts Categories 1–4 (not 5).
- Categories 1–3 use the skull-and-crossbones (GHS06) + “Danger”; Category 4 uses the exclamation mark (GHS07) + “Warning.”
- Based on LD50 (oral/dermal) and LC50 (inhalation), or an Acute Toxicity Estimate (ATE) for mixtures.
In plain English
How GHS rates a chemical's “how much could kill or seriously harm you quickly” risk. Lower the dose it takes to be lethal (the LD50/LC50), the more toxic — and the lower the category number. Category 1 is the deadliest.
What the source says, in summary
Acute toxicity refers to those adverse effects occurring following oral or dermal administration of a single dose of a substance, or multiple doses given within 24 hours, or an inhalation exposure of 4 hours.
In context
A classification or labeling concept from the UN Globally Harmonized System, adopted into US law through OSHA's Hazard Communication Standard (29 CFR 1910.1200) and its appendices.
Where this is written in OSHA's rules
- 29 CFR 1910.1200 App A.1Read on eCFR / OSHA.gov
Example
A pesticide with an oral LD50 of 30 mg/kg falls in acute-toxicity Category 2 (>5 to ≤50 mg/kg), so its label carries the skull-and-crossbones pictogram (GHS06), the signal word “Danger,” and the hazard statement H300, “Fatal if swallowed.”
Why it matters
Acute-toxicity classification sets the deadliest cues on a label — the skull pictogram and “Fatal if swallowed/in contact with skin/if inhaled.” Getting the category wrong (or omitting GHS06) understates a potentially lethal hazard and is a HazCom classification/labeling violation under 1910.1200.
Acute toxicity vs. chronic / STOT
Acute toxicity is harm from a single or short (≤24 h) exposure — measured by LD50/LC50. Chronic effects (carcinogenicity, STOT-repeated exposure, reproductive toxicity) come from long-term exposure and are separate hazard classes, even though several can apply to the same chemical.
GHS acute toxicity categories (oral LD50)
| Category | Oral LD50 (mg/kg) | Pictogram · signal word |
|---|---|---|
| 1 (most toxic) | ≤ 5 | Skull (GHS06) · Danger |
| 2 | > 5 to ≤ 50 | Skull (GHS06) · Danger |
| 3 | > 50 to ≤ 300 | Skull (GHS06) · Danger |
| 4 | > 300 to ≤ 2000 | Exclamation (GHS07) · Warning |
| 5 (GHS only, not OSHA) | > 2000 to ≤ 5000 | (no pictogram) · Warning |
Acute Toxicity: frequently asked questions
- How many acute toxicity categories are there?
- GHS defines five categories (1 = most toxic, 5 = least). OSHA's Hazard Communication Standard adopts Categories 1–4; Category 5 is not used on US labels.
- What is the difference between acute and chronic toxicity?
- Acute toxicity is harm from a single dose or short (up to 24-hour) exposure, measured by LD50/LC50. Chronic toxicity refers to effects from long-term, repeated exposure — covered by separate hazard classes such as carcinogenicity and STOT.
- Which pictogram is used for acute toxicity?
- Categories 1–3 use the skull-and-crossbones (GHS06) with the signal word “Danger.” Category 4 uses the exclamation mark (GHS07) with “Warning.”
Related terms
Free tools for this
Governing OSHA standards
More GHS terms
A GHS health-hazard class for chemicals that can be fatal if swallowed and then enter the airways — directly or by vomiting — causing chemical pneumonia or lung injury. Thin, low-viscosity hydrocarbons (gasoline, kerosene, lamp oil) are the classic example. It is Category 1, with the health-hazard pictogram (GHS08) and signal word “Danger.”
CarcinogenicityA GHS health-hazard class for chemicals that cause cancer or increase its incidence. GHS (and OSHA's HazCom standard) sorts carcinogens into Category 1A (known human carcinogen), 1B (presumed, from animal evidence), and Category 2 (suspected). Carcinogens carry the health-hazard pictogram (GHS08) and a hazard statement such as H350 (“May cause cancer”).
Chemicals Under PressureA physical-hazard class added by OSHA's 2024 HCS update (aligning with GHS Revision 7) for liquids or solids pressurized with a gas, held in pressure receptacles other than aerosol dispensers and not classified as gases under pressure. It is categorized by the flammability of its contents and always carries the gas-cylinder pictogram (GHS04) for the pressure hazard.
ClassificationThe process of evaluating the available scientific evidence for a chemical against the GHS criteria to decide whether it is hazardous and, if so, the hazard class and category of each effect. Classification is the first step in HazCom — its result determines every label element (pictogram, signal word, hazard and precautionary statements) and SDS content.
Corrosive to MetalsA GHS physical-hazard class for chemicals that, by chemical action, will materially damage or even destroy metals. It is a single category (Category 1), determined by corrosion-rate testing on steel and aluminum, and uses the corrosion pictogram (GHS05) with the hazard statement H290. It is a separate hazard from skin corrosion, even though both use GHS05.
Desensitized ExplosivesA physical-hazard class added by OSHA's 2024 HCS update (GHS Revision 7) for solid or liquid explosives that have been phlegmatized — wetted or diluted — to suppress their explosive properties for safe transport and storage. It has four categories based on the corrected burning rate, and uses the flame pictogram (GHS02), not the exploding-bomb.
Globally Harmonized System (GHS)An internationally agreed framework created by the United Nations (first adopted in 2003) that standardizes how chemical hazards are classified and communicated — using common hazard classes, pictograms, signal words (Danger / Warning), and coded hazard (H) and precautionary (P) statements on labels and safety data sheets. The US adopted GHS into law through OSHA's 2012 Hazard Communication Standard update.
GHS Revision 7The 7th revision of the UN Globally Harmonized System, which OSHA adopted in its 2024 update to the Hazard Communication Standard (with selected elements of Revision 8). It adds new hazard classes — desensitized explosives and chemicals under pressure — folds pyrophoric and chemically unstable gases into flammable gases, and updates label and SDS provisions. The final rule was effective July 19, 2024, with phased compliance dates.
Sources & verification
- 29 CFR 1910.1200 App A.1 (eCFR / OSHA.gov)
- OSHA — Appendix A to §1910.1200: Health Hazard Criteria (Mandatory)
- UNECE GHS — Part 3: Health Hazards
Reviewed by HazComFast against eCFR, OSHA.gov, NIOSH, and the Federal Register. Last reviewed 2026-10-05. This glossary is general information, not legal advice; OSHA State-Plan states (e.g. California, Michigan) may adopt stricter requirements.
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