e-Digest Statistics about: Inland Water Quality and Use
Freshwater quality
Pesticides
Pesticide concentrations exist at much lower levels than the determinands covered in the tables from the Harmonised Monitoring Scheme and are measured in µg/l (i.e. 10-6 grams per litre). The majority of pesticide samples fall below the detection limit of current analytical techniques and hence it is not always appropriate to present annual means for pesticides.
The EU drinking water directive has prescribed norms for pesticides in water intended for human consumption. The EU parametric values for individual pesticides (0.1 µg/) and for total pesticides (0.5 µg/l) are not based on any scientific findings. The Member States of the European Union and the European Commission that adopted the Drinking Water Directive 98/83/EC are of the opinion that pesticides should not be present in drinking water. The value of 0.1 µg/l is a substitute for zero, not present in water or below the detection limit. Total pesticides, being the sum of all pesticides that are present in concentrations above the detection limit (0.1 µg/l), should not exceed 0.5 µg/l. All pesticides that are officially registered for use and are likely to be used in the catchment area need to be monitored, and the total sum is calculated by adding all concentrations that exceed the parametric value/detection limit of 0.1 µg/l.
The Environment Agency (EA) has prepared information covering all pesticides in fresh waters in England and Wales. Table 13 shows summary information for 1995-2004 relating to the pesticides most commonly found in freshwater together with some other selected pesticides. About 100 were detected in rivers in England and Wales during this period, the vast majority of which were found in very small quantities in water, and below any relevant Environmental Quality Standards (EQSs) [10]. Thus it is difficult to illustrate any changes over time in terms of such standards. For this reason, an arbitrary level of 0.1 µg/l has been used, and the proportion of samples above this level has been presented to illustrate both the relative frequencies that these pesticides are found in water, and also any changes in levels over the last five years. The assessment at the 0.1 µg/l level does not relate either to statutory standards or even guidelines. However, it does serve to illustrate the very small quantities involved and that there is a rapid fall-off at levels over 0.1 µg/l.
Two of the pesticides most frequently found in surface waters are isoproturon and mecoprop, both agricultural pesticides. As part of existing controls the herbicides simazine and atrazine have been banned from non-agricultural use (for example, for maintenance of roadside verges and railway embankments) since September 1993. Diuron was possibly used initially as an alternative to atrazine following its ban. For those pesticides classified as List II substances under the EC Dangerous Substances Directive (76/464) the EA employs operational EQSs from which it derives discharge consents and against which it monitors environmental quality.
The European Community (EC) review programme ensures the safety of all pesticides used throughout the EC. It ensures they are evaluated to modern standards. The basis of the EC review programme is set out in Article 8.2 of Council Directive 91/414/EEC. The Directive provides for the establishment of a positive list of active substances (Annex I to Directive 91/414/EEC), that have been shown to be without unacceptable risk to people or the environment. The Pesticides Safety Directorate (PSD) is an Executive Agency of the Department for Environment, Food and Rural Affairs (Defra) and works to ensure the safe use of pesticides for people and the environment. Since 1995 a number of products have been withdrawn as a result of the EC review programme.
More recently the EA has found concentrations of bentazone above 0.1 µg/l in both surface and groundwater. The PSD has recently re-registered bentazone for use in the UK following the EU review. The properties of bentazone would suggest that it can potentially leach into water bodies but the assessment that the PSD conducts for national registration looks at the average concentration over the course of a year, rather than at individual peaks which might potentially exceed this level. Overall, according to the PSD assessment methods, it was determined that use of bentazone was acceptable within the terms of good agricultural practice (GAP).
Table 15 shows summary information relating to the pesticides most commonly found in groundwater presented in a similar format to that for freshwater in Table 13 using the same two arbitrary levels. As with Table 13 the levels of concentration are used for illustration only. In 2005 bentazone was the pesticide most frequently found in groundwater at levels above 100ng/l, followed by atrazine.
In Detail:
- Harmonised Monitoring Scheme
- e-Digest: Coastal and Marine: Pesticide concentrations
Further Information:
Data Tables:
| Table
No. |
Title | Download file type |
| 13 | Pesticides in surface water samples: 1995-2004, England & Wales | |
| 15 | Pesticides in groundwater samples: 1998-2005, England & Wales |
- References, further reading and links to other resources:
- [10] Pesticides in the Aquatic Environment 1995. Environment Agency, Centre for Ecotoxicology and Hazardous Substances, March 1997
- [23] Pesticides Report 2005: Pesticides in rivers, groundwater and pollution incidents. Environment Agency, December 2006
- Internet Links:
- For national and local information see:
- England and Wales: Environment Agency - Pesticides
- Scotland: Scottish Environment Protection Agency - Harmonised Monitoring Data
- Northern Ireland: Environment and Heritage Service
- Department of the Environment in Northern Ireland
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Page last modified: 16 February 2006
Page published: 16 February 2006