How is aquatic toxicity classified?

Acute (short-term) aquatic toxicity is classified into Categories 1–3 based on the concentration that is lethal or immobilizing to standard test organisms — fish (96-hour LC50), crustacea such as daphnia (48-hour EC50), and algae or aquatic plants (72/96-hour ErC50). Category 1 is the most toxic (≤ 1 mg/L). Chronic (long-term) aquatic toxicity is classified into Categories 1–4, combining toxicity data with the chemical's degradation (persistence) and bioaccumulation potential.

What is the difference between acute and chronic aquatic toxicity?

Acute aquatic toxicity measures harm to aquatic organisms from short-term exposure and is classified into three categories from lethal-concentration data. Chronic (long-term) aquatic toxicity measures harm across the organism's life cycle and is classified into four categories, additionally accounting for how long the chemical persists in the environment (degradation) and whether it builds up in organisms (bioaccumulation). A substance can be both acutely and chronically toxic to aquatic life.

GHS / HazCom term · Glossary

Hazardous to the Aquatic Environment (Aquatic Toxicity)

Verified vs OSHA sources · 2026-10-05

A GHS environmental hazard class describing a chemical's potential to harm aquatic life. It has two forms: ACUTE (short-term) aquatic toxicity, classified into Categories 1–3 from the concentration lethal or immobilizing to test organisms; and CHRONIC (long-term) aquatic toxicity, classified into Categories 1–4 from toxicity combined with environmental fate (degradation and bioaccumulation). Classification uses fish 96-hour LC50, crustacea 48-hour EC50, and algae 72/96-hour ErC50 data. It uses the GHS09 (environment) pictogram — but OSHA does NOT require environmental hazard classification, because it falls outside OSHA's human-health jurisdiction.

29 CFR 1910.1200

Also known as: aquatic toxicity, environmental hazard, hazardous to aquatic life, GHS09 hazard

Hazardous to the Aquatic Environment (Aquatic Toxicity) at a glance

Two forms: Acute (short-term) aquatic toxicity, Categories 1–3; and Chronic (long-term), Categories 1–4.
Test data: fish 96-hour LC50, crustacea (e.g., daphnia) 48-hour EC50, algae/aquatic plant 72/96-hour ErC50.
Acute Category 1: LC50/EC50/ErC50 ≤ 1 mg/L (most toxic) — GHS09 pictogram + signal word 'Warning.'
Acute Categories 2 (>1–10 mg/L) and 3 (>10–100 mg/L): no pictogram and no signal word.
Chronic classification also weighs degradation (persistence) and bioaccumulation potential.
Pictogram: GHS09 (dead fish and tree) — used only for Acute 1 and Chronic 1/2.
OSHA does NOT require environmental classification; GHS09 is mandatory under EU/GB CLP but voluntary in the US.

In plain English

How dangerous a chemical is to fish and other water life. GHS rates it two ways: short-term (acute) harm in Categories 1–3, and long-term (chronic) harm in Categories 1–4, using standard lab tests on fish, water fleas, and algae. It's shown by the dead-fish-and-tree symbol (GHS09). Important for the US: OSHA does NOT require this environmental class on labels — it's about the environment, not worker health — though many suppliers include it voluntarily.

What the source says, in summary

OSHA's Hazard Communication Standard addresses hazards to workers; classification of environmental (aquatic) hazards and the GHS09 environment pictogram are outside OSHA's jurisdiction and are not required on U.S. HazCom labels, though they may be included voluntarily (and are mandatory in jurisdictions such as the EU under CLP).
29 CFR 1910.1200 — OSHA scope (environmental class not required)Summarized, not quoted: read the source for its operative wording.

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.

29 CFR 1910.1200

Where this is written in OSHA's rules

29 CFR 1910.1200Read on eCFR / OSHA.gov

Example

A pesticide active ingredient has a 96-hour LC50 in fish of 0.4 mg/L — below 1 mg/L — so it is classified Acute Category 1 for aquatic toxicity, the most severe short-term band, and (given its persistence and bioaccumulation) Chronic Category 1 as well. In the EU its CLP label must carry the GHS09 environment pictogram and 'Warning.' On a U.S. OSHA HazCom label the same GHS09 pictogram is not required, because OSHA regulates worker health rather than environmental effects — but a responsible supplier often includes it and always reports the aquatic toxicity in SDS Section 12 (Ecological Information).

Why it matters

Aquatic toxicity is the one GHS hazard class that is explicitly outside OSHA's authority, which creates a common compliance trap: U.S. workers and safety managers see the GHS09 environment pictogram (or its absence) and misjudge what OSHA requires. Knowing that GHS09/aquatic classification is voluntary under OSHA — but mandatory under EU/GB CLP and reported in SDS Section 12 — prevents both over-citing a non-OSHA requirement and overlooking genuine environmental and spill-response obligations under EPA/RCRA and state rules.

GHS09 environment pictogram is NOT OSHA-required

This is the single most-cited exception in the OSHA HazCom pictogram set. OSHA requires eight pictograms; the ninth, GHS09 (environment — dead fish and tree), is deliberately NOT required on U.S. HazCom labels because environmental/aquatic hazards fall outside OSHA's worker-health jurisdiction. The same substance sold in the EU or GB must display GHS09 under CLP, where environmental classification is mandatory. So the presence or absence of GHS09 on a label reflects jurisdiction, not the chemical's actual aquatic hazard — which is always reported in SDS Section 12 (Ecological Information) regardless.

GHS Aquatic Toxicity Categories

Class / Category	Basis	Label
Acute 1	96-hr LC50 (fish) ≤ 1 mg/L (most toxic)	GHS09 + 'Warning'
Acute 2	LC50 > 1 to ≤ 10 mg/L	No pictogram / no signal word
Acute 3	LC50 > 10 to ≤ 100 mg/L	No pictogram / no signal word
Chronic 1–4	Toxicity + degradation + bioaccumulation	GHS09 for Chronic 1–2 only

Hazardous to the Aquatic Environment (Aquatic Toxicity): frequently asked questions

Does OSHA require the environmental (GHS09) pictogram?: No. OSHA's Hazard Communication Standard requires eight pictograms; the GHS09 environment pictogram (dead fish and tree) and the underlying aquatic/environmental hazard classification are outside OSHA's jurisdiction and are not required on U.S. HazCom labels. Suppliers may include GHS09 voluntarily, and it IS mandatory in the EU and Great Britain under CLP. Regardless of labeling, aquatic toxicity data are reported in SDS Section 12 (Ecological Information).
How is aquatic toxicity classified?: Acute (short-term) aquatic toxicity is classified into Categories 1–3 based on the concentration that is lethal or immobilizing to standard test organisms — fish (96-hour LC50), crustacea such as daphnia (48-hour EC50), and algae or aquatic plants (72/96-hour ErC50). Category 1 is the most toxic (≤ 1 mg/L). Chronic (long-term) aquatic toxicity is classified into Categories 1–4, combining toxicity data with the chemical's degradation (persistence) and bioaccumulation potential.
What is the difference between acute and chronic aquatic toxicity?: Acute aquatic toxicity measures harm to aquatic organisms from short-term exposure and is classified into three categories from lethal-concentration data. Chronic (long-term) aquatic toxicity measures harm across the organism's life cycle and is classified into four categories, additionally accounting for how long the chemical persists in the environment (degradation) and whether it builds up in organisms (bioaccumulation). A substance can be both acutely and chronically toxic to aquatic life.

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Governing OSHA standards

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More GHS terms

Acute Toxicity

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.

Aspiration Hazard

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.”

Carcinogenicity

A 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 Pressure

A 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.

Classification

The 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 Metals

A 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 Explosives

A 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.

Sources & verification

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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