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UK case study on probabilistic risk assessment for aquatic organisms - PN0933

Pesticide regulatory risk assessments for aquatic organisms are currently derived in the UK and the rest of the EU under Directive 91/414 EEC. This recommends a Toxicity Exposure Ratio (TER) approach in which reasonable worst case toxicity data are compared with reasonable worst case exposure data. This approach wastes much data on the probability distribution of both toxicity and exposure that may be useful in understanding i) the behaviour and effects of the pesticide under normal use conditions, ii) the environmental consequences of particular concentrations of the pesticide, and iii) appropriate measures for managing risks associated with the pesticide. Because of this, probabilistic risk assessments (PRAs) have been recommended for pesticide regulation by several researchers, particularly in North America. PRAs typically compare probability distributions of exposure concentration and toxic effect to arrive at a range of possible pesticide impacts with quantified levels of probability for each possible value. North American regulatory agencies have investigated the usefulness of PRA in assessing pesticides through active involvement in the ECOFRAM initiative and sponsorship of other research initiatives. Pesticide manufacturers have also invested effort in exploring the advantages of probabilistic approaches (e.g., Zeneca Agrochemical's PondFX web pages and active involvement of pesticide companies in ECOFRAM). PRA may enhance certain aspects of the control of pesticides, but it is not a panacea for all the problems faced by pesticide regulators. It may even produce less robust risk assessments than the current deterministic approaches if concepts such as species sensitivity distributions or Monte Carlo simulations of probability distributions are enthusiastically misused. MAFF PSD needs to understand both the advantages and potential disadvantages of a move towards PRA for pesticides. Our proposal outlines a cost-effective and balanced approach to this that emphasises a scientifically rigorous test of available approaches within a UK regulatory context.
This proposal has the following objectives:
1. Selection of two pesticides and risk assessment protection objectives for use in two case studies, after full discussion with PSD
2. To perform a series of probabilistic risk assessments using different combinations of exposure and toxicity input parameters, different assumptions, and different risk assessment models.
3. To perform uncertainty analyses on all outputs, with a particular focus on,
a) the number and types of toxicity data that are required for an effective hazard assessment;
b) the number and types of physical and chemical data that are required for an effective exposure assessment;
c) the influence of default assumptions currently used in pesticide risk assessments in Europe.
4. To review the literature to assess to what extent information on organism life histories and general ecology can be used to predict their exposure to, and recovery from, pesticides.
5. To provide guidance on whether probabilistic risk assessment provides advantages over current approaches used in the EU, and how these advantages can be incorporated into risk assessments under Directive 91/414 EEC. This will include organisation of a one-day workshop for invited participants from the pesticide industry, MAFF, the Environment Agencies, and academia to communicate the results of the project; a final report with recommendations for further research; and two peer-reviewed papers.
Project Documents
• Final Report : UK Case Study on Probabilistic Risk Assessment for Aquatic Organisms   (736k)
Time-Scale and Cost
From: 2001

To: 2002

Cost: £51,000
Contractor / Funded Organisations
University - London - Royal Holloway College
Environmental Protection              
Nature conservation              
Wildlife conservation              
Fields of Study
Pesticide Safety