What are they?
Substances hazardous to the aquatic environment are substances that may cause harmful effects in organisms living in water. The CLP Regulation establishes specific criteria for classifying substances and mixtures according to their short-term (acute) and long-term (chronic) aquatic hazard.
Aquatic toxicity can affect different organisms, such as fish, crustaceans, algae and other aquatic plants. Properties such as persistence, bioaccumulation and degradability are also taken into account when assessing the hazard. Regulation (EC) No 1272/2008 (CLP), consolidated text – EUR-Lex
The main hazard statements relating to toxicity to the aquatic environment are:
- H400: Very toxic to aquatic life.
- H410: Very toxic to aquatic life with long lasting effects.
- H411: Toxic to aquatic life with long lasting effects.
- H412: Harmful to aquatic life with long lasting effects.
- H413: May cause long lasting harmful effects to aquatic life.
Substances classified as Aquatic Acute 1 carry the hazard statement H400.
The Aquatic Chronic 1, 2, 3 and 4 categories correspond, respectively, to hazard statements H410, H411, H412 and H413.
Hazard to the aquatic environment should not be confused with toxicity to human health. However, chemical pollution of water can also pose a risk to human health where exposure occurs through the aquatic environment. MITECO states that water protection policy against chemical pollution takes into account both risks to the aquatic environment and risks to human health through this medium. Chemical status of surface waters – MITECO
What should be done?
Substances hazardous to the aquatic environment should be prevented from reaching drains, sewerage systems, surface waters, groundwater or any other part of the public water domain.
In the event of an accidental spill:
- Prevent the product from reaching drains or water.
- Contain the spill as soon as possible using suitable means, such as absorbent materials or containment barriers.
- Collect the contaminated material and manage it according to its nature and the procedures established by the company.
- Do not use water to wash the product into drains or the aquatic environment.
- Follow the instructions in the safety data sheet and the emergency procedures established for the product.
- If the spill may reach water or the public water domain, apply the appropriate notification and response procedures.
The Ministry for the Ecological Transition and the Demographic Challenge (MITECO) states that, as a general rule, the direct or indirect discharge of water and waste products liable to contaminate inland waters or any other part of the public water domain is prohibited unless the corresponding authorisation has been granted. Discharge authorisation – MITECO
Prevention should primarily address the source of pollution by reducing emissions, discharges and losses of hazardous substances and preventing them from reaching the aquatic environment. Directive 2000/60/EC – Water Framework Directive – EUR-Lex
Guidance
Chemical status of surface waters – Ministry for the Ecological Transition and the Demographic Challenge (MITECO)
Official information on priority substances and other pollutants, environmental quality standards and the assessment of the chemical status of waters.
Assessment of the status of surface waters – MITECO
Official information on the assessment of the chemical and ecological status of surface water bodies.
Assessment of the status of surface waters – MITECO
Discharge authorisation – MITECO
Official information on requirements applicable to discharges into the public water domain and action to be taken in emergency situations.
Discharge authorisation – MITECO
Substances hazardous to water – Umweltbundesamt (UBA)
Official information from the German Federal Environment Agency on substances and mixtures hazardous to water and their classification according to water hazard classes (WGK).
Substances hazardous to water – Umweltbundesamt
Classification
Hazard to the aquatic environment under the CLP Regulation
The CLP Regulation establishes a specific classification for hazard to the aquatic environment:
- Aquatic Acute 1: H400 – Very toxic to aquatic life.
- Aquatic Chronic 1: H410 – Very toxic to aquatic life with long lasting effects.
- Aquatic Chronic 2: H411 – Toxic to aquatic life with long lasting effects.
- Aquatic Chronic 3: H412 – Harmful to aquatic life with long lasting effects.
- Aquatic Chronic 4: H413 – May cause long lasting harmful effects to aquatic life.
The classification criteria take into account, among other factors, acute or chronic toxicity to aquatic organisms, degradability and bioaccumulation potential.
Priority substances under European Union water policy
Directive 2000/60/EC, known as the Water Framework Directive, establishes the European framework for the protection of surface water and groundwater and provides for measures to progressively reduce pollution from priority substances and to cease or phase out discharges, emissions and losses of priority hazardous substances.
Directive 2000/60/EC – EUR-Lex
Directive 2008/105/EC establishes environmental quality standards for priority substances and certain other pollutants. This Directive was amended by Directive 2013/39/EU, which expanded and updated the list of priority substances and their environmental quality standards.
Directive 2008/105/EC – consolidated text – EUR-Lex
Directive 2013/39/EU – EUR-Lex
Directive (EU) 2026/805 of 30 March 2026 amends Directives 2000/60/EC, 2006/118/EC and 2008/105/EC and updates the European framework for protecting water against chemical pollution. Directive (EU) 2026/805 is in force at European Union level. Member States must adopt the necessary national provisions for its transposition by 21 December 2027. Directive (EU) 2026/805 – EUR-Lex
Spanish legislation on priority substances and water quality
In Spain, Royal Decree 817/2015 of 11 September establishes the criteria for monitoring and assessing the status of surface waters and environmental quality standards.
The consolidated text available in the BOE records 11 January 2023 as the date of its latest published update.
Royal Decree 817/2015 – consolidated text – BOE
MITECO states that the chemical status of surface waters reflects compliance with environmental quality standards for priority substances and other pollutants. Environmental quality standards establish pollutant concentrations that must not be exceeded in order to protect human health and the environment.
Royal Decree 817/2015 establishes environmental quality standards for priority substances and other pollutants, as well as standards applicable to preferential substances and criteria for basin-specific pollutants.
Hazard to water. Germany
Germany uses a specific classification system for substances and mixtures according to their hazard to water (Wassergefährdungsklassen, WGK), regulated by the AwSV (Verordnung über Anlagen zum Umgang mit wassergefährdenden Stoffen).
The categories are:
- WGK 1: slightly hazardous to water.
- WGK 2: hazardous to water.
- WGK 3: highly hazardous to water.
In addition, certain substances may be classified as nwg (nicht wassergefährdend, not hazardous to water) or considered awg (allgemein wassergefährdend, generally hazardous to water).
AwSV – German legislation on substances hazardous to water
The Umweltbundesamt provides the Rigoletto database, where the WGK classifications of substances can be consulted.
Rigoletto database – Umweltbundesamt
The WGK classification is a system established by German legislation and should not be confused with the aquatic environmental hazard classification under the European Union CLP Regulation.
Information on substances hazardous to water – Umweltbundesamt
Legislation and guidance
- Regulation (EC) No 1272/2008 (CLP) on the classification, labelling and packaging of substances and mixtures.
- EUR-Lex – CLP Regulation
- Directive 2000/60/EC establishing a framework for Community action in the field of water policy.
- EUR-Lex – Directive 2000/60/EC
- Directive 2008/105/EC on environmental quality standards in the field of water policy.
- EUR-Lex – Directive 2008/105/EC
- Directive 2013/39/EU amending Directives 2000/60/EC and 2008/105/EC as regards priority substances in the field of water policy.
- EUR-Lex – Directive 2013/39/EU
- Directive (EU) 2026/805 amending Directives 2000/60/EC, 2006/118/EC and 2008/105/EC.
- EUR-Lex – Directive (EU) 2026/805
- Royal Decree 817/2015 of 11 September, establishing the criteria for monitoring and assessing the status of surface waters and environmental quality standards.
- BOE – Royal Decree 817/2015
- AwSV – Verordnung über Anlagen zum Umgang mit wassergefährdenden Stoffen, German legislation on installations handling substances hazardous to water.
- Gesetze im Internet – AwSV
- Umweltbundesamt – substances hazardous to water and WGK classification.
- Umweltbundesamt – Wassergefährdende Stoffe
- Rigoletto database – Umweltbundesamt.
- Rigoletto / WGK
References
The sources used for this update are official institutional and regulatory sources:
- European Union / EUR-Lex: CLP Regulation, Water Framework Directive, Directive 2008/105/EC, Directive 2013/39/EU and Directive (EU) 2026/805.
- Official State Gazette (BOE): Royal Decree 817/2015.
- Ministry for the Ecological Transition and the Demographic Challenge (MITECO): official information on chemical status and water quality.
- Umweltbundesamt (UBA): official information on substances hazardous to water and WGK classification.
- Gesetze im Internet: official text of the German AwSV legislation.
Last updated: August 2026.