Guidance

Monitoring discharges to water: CEN and ISO monitoring methods

Formerly part of M18, index of CEN and ISO monitoring methods for monitoring discharges to water.

• From: Environment Agency
• Published: 11 June 2020
• Last updated: 17 September 2026
  Show all updates

  1. 17 September 2026

     Updated the entry for 'Perfluoroalkyl and polyfluoroalkyl substances (PFAS)' in line with BS ISO 21675.

  2. 8 September 2026

     A standard for polyfluoroalkyl substances (PFAS) has been added in place of the standard for Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA)

  3. 18 January 2023

     New standards added for biochemical oxygen demand (BOD), cyanide, nitrogen (total), total organic carbon, organochlorine pesticides, polycyclic aromatic hydrocarbons, short-chain polychlorinated alkanes, and volatile organic carbons. Those for BOD and nitrogen (total) supersede previous versions.

  4. 11 June 2020

     First published.

Applies to England

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Monitoring discharges to water: CEN and ISO monitoring methods

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The methods in this document are international standards recommended by regulation.