The SEVESO Directive

Seveso Directive: Directive 2012/18/EU

Directive 2012/18/EU on the control of major-accident hazards involving dangerous substances, otherwise known as the Seveso Directive was originally introduced in 1982 to prevent major-accident hazards involving dangerous substances, following a chemical accident at an industrial plant in Seveso, Italy in 1976. Significant quantities of dioxin was released as an unwanted by-product from a runaway chemical reaction, causing significant environmental contamination. More than 600 people were evacuated following the incident due to health concerns.


Subsequent amendments to the Directive (largely to broaden the scope) were made in 1987 (87/216/EEC) and in 1988 (88/610/EEC), following further chemical accidents. A tragic chemical incident in Bhopal in 1984 involving methyl isocyanates, is widely reported to have caused the loss of thousands of human lives. A warehouse fire in Basel in 1986 resulted in extensive environmental pollution, when fire-fighting water containing mercury and organophosphate pesticides polluted the River Rhine.


To determine whether in scope, the chemical inventory of an establishment must be checked against the qualifying criteria set out in Parts 1 and Parts 2 of Annex I to the Directive. An organisation is subject to Seveso when substances are present in quantities equal to, or in excess of the qualifying thresholds:


  • Part 1 is a list of generic hazard categories following the classification criteria of the CLP Regulation (see Note 1 below)  e.g. flammable liquids, environmental hazards, oxidising gases.
  • Part 2 is a list of named substances e.g. methanol.

There are two thresholds, lower tier and upper tier, based on two quantity limits defined for each generic category and named substance. Top tier sites are subject to more extensive compliance requirements than lower tier, to reflect greater risk from larger quantities held on site.


An establishment must consider the maximum quantities present, or likely to be present at any one time, including the potential for chemicals to be produced during chemical reaction, whether planned or otherwise. Mixtures must also be counted when classified in one of the generic categories. In the case of substances or mixtures falling within more than one hazard category, the lowest threshold hazard category must be used.


An establishment may still be in scope even if the threshold is not reached for any named substance or individual generic category, due to the requirement to aggregate similar hazard categories. Thus, for example, substances with a physical hazard classification are aggregated using a partial fraction calculation. This is performed by adding together the resultant values obtained from dividing the quantity of each category by the threshold limit for that category. If the aggregate value is greater than 1, the establishment is in scope. 


Provision for information exchange and land use policy/planning was a feature of the 1996 revision (96/82/EC). New rules were introduced to reduce the risk of domino effects between neighbouring sites and effects of a chemical accident on residential and ecological communities, through safety management systems and emergency planning.


The 2012 revision to align the hazard classification criteria to the CLP Regulation, resulted in more organisations falling within scope. For some organisations, this was due to differences in the classification criteria between the CLP Regulation and DSD/DPD (see Note 2 below); for others, it was due to the inclusion of further named substances in Part 2, or broadening in scope of the generic categories in Part 1. Many sites transgressed from lower to upper tier status with the revision.


There has been some criticism of the Directive because it is generally hazard and not risk based legislation, based on exceeding quantity triggers. Many organisations are in scope because they store small pack sizes on site. There is no pack size relaxation in the requirements, as permitted by other regulation e.g. limited quantity derogation within transport regulation. 


Some organisations are in scope due to the presence of classified mixtures on site, but no pure substances and do not conduct any manufacturing or processing activities. Conversely, many organisation are out of scope with significant quantities of a pure substance on site, just below the qualifying threshold.


The lower tier qualifying limit for hazardous to the aquatic environment in category acute 1 or chronic 1 (dangerous to the environment) at 100 tonnes lower tier and 200 tonnes upper tier,  is reported to have brought many sites into scope, and is considered disproportionate to the qualifying thresholds for flammable liquids, 5,000 and 50,000 tonnes respectively. Risk control measures, such as site-bunding to prevent environmental release is not relevant, only quantities on site. 


A European Directive is a guiding legislative instrument that each European Member State must transpose into national legislation (within defined timescales) and can therefore be subject to interpretation and consequently variation across Member States. A regulation does not require transposition into national law and is binding on Member States, resulting in uniform implementation and applicability at the same time.


There is a reported lack of consistency in the way individual Member States interpret Seveso and in turn, the way individual national Competent Authorities enforce the legislation, resulting in major differences in cost and impact to business.




Note 1: The Classification, Labelling and Packaging of substances and mixtures Regulation 1272/2008 (EC)


Note 2: Dangerous Substances Directive (67/548/EEC)/Dangerous Preparations Directive (1999/45/EC)


Page published 14 May 2018