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A range of substances that persist in the environment can accumulate in organisms as they are difficult to metabolise and excrete (bioaccumulation). When these organisms are eaten, the substances increase in concentration as they travel up food chains (biological magnification). These include:

  • Persistent organic pollutants (POPs); chemicals with a particular combination of properties that resist environmental degradation, have low solubility in water, accumulate in the fat or organs of organisms and have a range of toxic effects.
  • Potentially toxic metals (PTMs); such as mercury and lead, bind to proteins and are deposited in the tissues of organisms and may induce toxic effects. PTMs occur naturally in geological deposits, but human activity is responsible for the majority of forms and concentrations that are present in the environment.

A recent assessment of 60 years of EU chemicals legislation has estimated its social and economic benefits at tens of billions of Euros per year, including reductions in healthcare costs and environmental damage. The 2017 Chief Medical Officer’s Report highlighted the adverse effects of chemical pollution on human health. The 2017 Lancet Commission on pollution and health suggested that the effects on human health have been underestimated and more testing of chemicals for health hazards is required. In addition to hazard testing, regulatory chemical risk assessments also consider the likelihood of exposure and the probability of adverse effects occurring. This POSTnote summarises the frameworks under which POPs and PTMs are regulated, assessing the legacy of contamination from historic emissions and emerging challenges for regulators.

Key points in this POSTnote include:

  • Humans benefit from the use of chemicals, but a number of persistent chemicals have accumulated in the environment affecting wildlife and human health.
  • Regulation has reduced levels of some persistent chemicals in the environment, but remaining levels of contamination in soils, sediments and waste may be of concern.
  • Monitoring levels of persistent chemicals in wildlife has been critical in determining the extent of reductions. However, knowledge gaps remain in the understanding of the effects of human and wildlife exposure.
  • After EU withdrawal, the UK will have to decide on approaches to managing risks from newly identified persistent and accumulative substances.


POSTnotes are based on literature reviews and interviews with a range of stakeholders and are externally peer reviewed. POST would like to thank interviewees and peer reviewers for kindly giving up their time during the preparation of this briefing, including:

  • Professor Stuart Harrad, University of Birmingham*
  • Professor Andrew Johnson, Centre for Ecology and Hydrology and Hazardous Substances Advisory Committee*
  • Dr Paul Jepson, Zoological Society London*
  • Dr David Megson, Manchester Metropolitan University*
  • Dr Lisa Yon, University of Nottingham*
  • Dr Rob Sweeney, CL:AIRE*
  • Dr Camilla Alexander-White, Royal Society of Chemistry
  • Dr Michael Warhurst, Chem Trust
  • Professor Susan Owens, University of Cambridge and Hazardous Substances Advisory Committee
  • Professor Michael DePledge CBE, University of Exeter and Hazardous Substances Advisory Committee 
  • Professor Alan Boobis OBE, Imperial College London*
  • Dr David Mortimer, Food Standards Agency
  • Professor Richard Shore, Centre for Ecology and Hydrology
  • Professor Scott Young, University of Nottingham
  • Julie Bygraves, Defra
  • Dr Steve Dungey, Environment Agency*
  • Richard Hawkins, Environment Agency
  • Dr Nick Cartwright. Environment Agency
  • Elen Strale, Defra
  • Silvia Segnia, Chemical Industries Association*
  • Roger Pullin, Chemical Industries Association*
  • Simon Marsh, Chemical Industries Association*
  • Nishma Patel, Chemical Industries Association*
  • Dr Jon Barber, CEFAS
  • Andrew Smith, HSE
  • Dr Steve Morris, Defra

*Denotes people who acted as external reviewers of the briefing. 

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