Environmental risks - Groundwater

Table of contents
Introduction Australia Canada China EU USA Can the legislative criteria be applied in other countries?	Legislation Groundwater risks Surface water risks Risks for bees Risks for soil organisms Terminology reference

Table of contents

Introduction

The risk assessment relating to groundwater is directed at the role of ground water as a source of drinking water. The focus is therefore on the exposure assessment.

The risk relating to groundwater are generally assessed using a tiered approach. An initial (screening) level risk assessment is based on models using default assumptions and conservative scenarios. A series of scenarios may be used to take into account variation in geographic and climatic conditions. When acceptable risk cannot be determined at the initial (screening ) level then more refined higher tier risk assessments are undertaken and/or risk mitigation measures applied.

Different regulatory frameworks use different approaches to characterising the risks relating to groundwater.

Note: where surface water is a source of drinking water exposure from surface water is also considered.

What this page contains

This table summarises the principles applied during the risk assessment to determine whether the environmental risks in relation to groundwater are acceptable. The focus is on the screening level assessment. The screening level assessment identifies those pesticides and uses where no further testing or analysis is required. Where available, links to documents that describe the more complex higher tier assessment in more detail are provided.

Summary analysis

The risk assessment relating to ground water is focussed on the role of ground water as a source of drinking water. The reader needs to be aware that regulatory approaches relating to drinking water differ internationally. The focus may be on the contribution of drinking water to the dietary risk assessment or the focus may be on the prevention of contamination of ground water per se. The ability to ‘translate’ international approaches to a particular country will depend on the way that drinking water is regulated in that country.

Australia

Aspect	Description
Links to risk assessment guidelines, manuals and science policy documents	Environmental Risk Assessment Guidance Manual Agricultural and veterinary chemicals, February 2009 Further information can be found at: Drinking water guidelines - pesticides The establishment of drinking water guidelines and/or standards is not the responsibility of the pesticide regulatory agency.
Hazard assessment and end-point selection	n.a.
Setting of toxicological reference values and the use of assessment factors	n.a.
Exposure assessment	Groundwater concentration is considered on a case-by-case basis. It may be calculated for determining indirect exposure of humans through drinking water. The methodology to predict groundwater concentration uses the concentration in porewater of agricultural soils as an indication for potential groundwater levels. It is a worst-case assumption that neglects transformation and dilution in deeper soaked layers.
Risk assessment and acceptability criteria	n.a.

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Canada

Aspect	Description
Links to risk assessment guidelines, manuals and science policy documents	Science Policy Note: technical Paper - A decision Framework for Risk Assessment and Risk Management in the Pest Management Regulatory Agency, December 2000 Science Policy Notice SPN2004-01; Estimating the Water Component of a Dietary Exposure Assessment, April 2004 Health-based guideline values for pesticides in Canadian drinking water are established by Health Canada in collaboration with the Federal-Provincial-Territorial Committee on Drinking Water.
Hazard assessment and end-point selection	n.a.
Setting of toxicological reference values and the use of assessment factors	n.a.
Exposure assessment	Pesticide concentrations in drinking water are estimated using the Pesticide in Water Calculator (PWC). PWC simulates pesticide movement and transformation, both through a soil profile and into shallow groundwater, and via runoff and spray drift into a drinking water reservoir.
Risk assessment and acceptability criteria	The estimates of the pesticide concentration in drinking water (the EECs) are included directly in the dietary exposure assessment with all the foods to determine the overall dietary risks compared with the Drinking Water Level of Concern (DWLOC). If the EECs are less that the DWLOC it is concluded that residues of pesticide in drinking water are below a risk level of concern. The EEC may also be incorporated into the dietary risk assessment.

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China

Aspect	Description
Links to risk assessment guidelines, manuals and science policy documents	Guidance on environmental risk assessment for pesticide registration- Part 6: Ground water NY/T 2882.6-2016 (in Chinese)
Hazard assessment and end-point selection	n.a.
Setting of toxicological reference values and the use of assessment factors	The WHO chemical Guideline Value for drinking water is adopted as the Regulatory Accepted Concentration (PNEC) and calculated by using the ADI accord to the recommendations in WHO Guidelines.
Exposure assessment	The China-PEARL model and TOP-RICE model are used to calculate the predicted environmental concentration in groundwater (PECgw) for dry land and paddy field, respectively.
Risk assessment and acceptability criteria	The acceptability criterion is based on the calulation of a risk quotient where RQ=PECgw/PNEC If RQ<= 1, the risk is considered acceptable if RQ

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EU

Aspect	Description
Links to risk assessment guidelines, manuals and science policy documents	FOCUS (FOrum for the coordination of pesticide fate models and their use) 2009. Assessing potential for movement of active substances and their metabolites to ground water in the EU; Report of the FOCUS Ground Water Work Group, EC Document Reference Sanco/13144/2010 FOCUS DG SANTE
Hazard assessment and end-point selection	n.a.
Setting of toxicological reference values and the use of assessment factors	One tenth of the ADI determined as part of the toxicological assessment and dietary risk assessment may be used as a toxicological reference value for groundwater in some circumstances as set out in Commission Regulation (EU) 546/2011.
Exposure assessment	The exposure assessment is based on the FOrum for Co-ordination of pesticide fate models and their USe (FOCUS) methodology. The FOCUS simulation models and scenarios are used to calculate the concentrations of pesticides (PEC) in groundwater.
Risk assessment and acceptability criteria	In accordance with Commission Regulation (EU) 546/2011 no authorisation can be granted if the active substance and significant metabolites and breakdown or reaction products in groundwater exceed: the limits set out in Directive 2006/118/EC; or the limit determined during the evaluation process or, where no such limit has been set, the concentration corresponding to one tenth of the ADI

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USA

Aspect	Description
Links to risk assessment guidelines, manuals and science policy documents	General Principles for Performing Aggregate Exposure and Risks Assessments, November 2001
Hazard assessment and end-point selection	n.a.
Setting of toxicological reference values and the use of assessment factors	The DWLOC is calculated based on the highest concentration of a pesticide in drinking water that would be acceptable taking into account the estimated exposure to that pesticide from other sources (ie food and residential use) and the PAD. That is, the total exposure from drinking water, food and residential use equals the PAD. Separate DWLOCs are calculated for different acute or chronic exposures and population groups where warranted.
Exposure assessment	The Pesticide in Water Calculator (PWC) is a water model used to estimate pesticide concentrations in surface water and ground water bodies that result from pesticide applications to land https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/pesticide-water-calculator-version-150-and-152-user
Risk assessment and acceptability criteria	If the estimated concentrations in ground and surface water are less than DWLOC risks from residues of the pesticide in drinking water are considered acceptable.

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Can the legislative criteria be applied in other countries?

A country’s/region’s source of drinking water is a critical element when assessing risks relating to groundwater. In some countries risks to ground water contamination is therefore only considered on a case-by-case basis.

Exposure assessment generally involve estimating concentrations of pesticide in groundwater using models based on local or regional scenarios. Screening-level/worst case exposure assessments used by some countries/regions may be applicable to other countries. However most regulators use very specific models. It is important that the regulator understands the scope and limitations of models they intend to use. Country/region specific models based on site-specific, local cropping situations, ecosystems, soil characteristics and weather may not readily be applied in other countries.

The estimated exposure from groundwater may aggregated with estimates of food exposure and residential exposure. In this case the trigger (level of concern) is the toxicological reference value used in dietary risk assessment. Other regulators apply legislated maximum allowable concentrations in drinking water sources as trigger values.

Country or regional policy should determine whether they set a trigger value/level of concern for contamination of drinking water or whether they aggregate the groundwater exposure with the dietary risk assessment.