Direct Toxicity Assessment and Mapping
 of Urban Groundwater Pollution

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Expanding on the Environment Agency’s current plans to regulate surface water toxicity through Direct Toxicity Assessment, this project aims to:

  • evaluate the use of established and novel ecotoxicity test procedures for identifying the sources, pathways and fluxes of pollutants in groundwaters
  • analyse the data from these toxicity tests using statistical techniques novel to the field of ecotoxicology
  • produce a 3-D groundwater pollutant map, based on the chemical and toxicological information, for a conurbation with a highly complex history of contamination sources and types - this will allow the diagnosis and characterisation of problems in relation to natural backgrounds
  • develop Toxicity Identification and Evaluation (TIE) procedures to identify classes of chemicals that pose the greatest ecotoxicological hazard at specific sites
  • develop generic guidance for the use of ecotoxicity testing and TIE techniques in monitoring contaminated groundwaters in the UK and to prescribe appropriate toxicity-based standards.

All data collection will be quality controlled and all aspects of the project will be quality assured within a Quality Management System.




There are three phases to the project. The main objective of Phase 1 is to compile an extensive database on groundwater toxicity in the London Borough of Hounslow. Existing information indicates that groundwater in certain areas contains high concentrations of contaminants, particularly metals and polyaromatic hydrocarbons. However, the toxicological significance of the contaminant mixtures remains unknown. Groundwater samples will be taken from the network of over 600 boreholes which have already be drilled in the Borough and at Heathrow Airport, and from 50 boreholes which will be drilled as part of this project.

In Phase 2, novel sublethal ecotoxicity tests will be used alongside standard suite tests to investigate the effect of groundwater samples on biomakers in Daphnia. This will allow the measurement of much lower levels of toxic effect than possible in Phase 1 and hence, refine the map of the spatial distribution of pollution near hotspots. It will also help to identify some of the major classes of chemicals that may be responsible for this pollution.

Once repeatable measurements of lethal or sublethal toxicity have been found through time at particular sampling sites, chemical fractionation techniques and toxicity testing (known as TIE) will be used in Phase 3 to help identify still further the toxic components of the ground water samples. TIE is a technique only recently introduced in Europe and consists of the manipulation of environmental samples to identify the physical and chemical nature of the substances causing toxic effects.

Start date/duration

October 1998 Three years

Lead Organisations

University of London

University of Reading


The outputs of the project will include user-friendly manuals, generic monitoring strategies and peer-reviewed scientific papers.


Hounslow Borough Council
British Airports Authority
Environment Agency
WS Atkins Environment

Further Details

Further information is available from the following contacts:

Lead Researcher: Prof J Mather
Tel: 01784 443625, Fax: 01784 471780, e-mail:

Research Assistant: Dr R Dewhurst
Tel: 01784 414196, Fax: 01784 471780, e-mail:

URGENT Programme Manager: Graham Leeks
Tel: 01491 692203, Fax: 01491 692313, e-mail: