Review of the Danish risk assessment methodology for pesticides regarding leaching to groundwater

Transcription

1 Review of the Danish risk assessment methodology for pesticides regarding leaching to groundwater Ton van der Linden, Colin Brown & Jenny Kreuger Danish Crop Conference - Plantekongres 2016 Herning, Denmark Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden

2 Background Protection of groundwater is highly prioritized in Denmark Almost all drinking water comes from untreated groundwater Many Danish soils are relatively vulnerable to leaching The Danish Government s new pesticide strategy included an international review of current approval practices regarding leaching to groundwater The review was initiated in spring 2014 A report was published in April 2015

3 The review was asked to evaluate (in a broad sense) The Danish procedure for risk assessment of pesticide leaching, incl. their metabolites The use of groundwater monitoring programmes within risk assessment Possible management actions (e.g. protection zones)

4 Risk assessment A clear definition of the protection goal of the leaching assessment is the basis for a good and scientifically sound decision scheme A general goal safeguarding the groundwater from being contaminated with pesticides and their metabolites in view of the drinking water function of the groundwater A specific goal stated in quantifiable terms (space and time) is crucial for a good decision scheme

5 Risk assessment (ctd) Denmark uses a definition for relevant metabolites that deviates from the definition at the EU level According to the Danish Framework all metabolites formed are to be assessed against the 0.1 µg/l criteria, regardless of toxicological and/or pesticidal concern of the metabolite, unless the metabolite occurs naturally in the environment (e.g. CO 2, H 2 O, mineral salts) and/or pose a significant risk This means that more metabolites will be subject to the leaching assessment scheme (with the likelihood that the companies need to generate new documentation)

6 Risk assessment (ctd) Another deviation from the standard European practice regards the Danish persistence criterion (which is absent in European regulation) This Danish criterion states that DT 50 must be < 6 months for an approval to be granted Soil persistence (DT 50 ) is often correlated to with soil sorption (K oc ), i.e. high DT 50 correlates with high K oc, which may exclude some compounds that otherwise might have passed the groundwater assessment

7 Risk assessment (ctd) Danish leaching assessment is intrinsically more conservative also in other aspects: Input parameters used are e.g. the 80 th percentile of DT 50 and the 20 th percentile K oc, in contrast to the EU assessment using the geometric means of DT 50 and K oc Modelling results rank annual average concentrations, at 1-m depth, and uses the 19 th value out of 20 (i.e. only 1 year out of 20 may exceed 0.1 µg/l), in contrast to the EU assessment using the 80 th percentile value for comparison to 0.1 µg/l

8 Risk assessment (conclusions) The review concluded that the Danish groundwater modelling assessment is very conservative (more cautious) relative to other protocols operating across the EU This may result in a relatively smaller number of available plant protection products (PPP) in Denmark One particular consequence of this relates to the risk of resistance of pests against PPP

9 Groundwater monitoring Several long-term monitoring programmes running in Denmark Pesticide Leaching Assessment Programme (PLAP, also known at VAP) Grundvandsovervågning (GVO) Gives a wealth of data and enhances the possibility to interpret the actual situation regarding pesticide contamination of groundwater

10 Groundwater monitoring (ctd) The PLAP programme (started in 1999) Pesticide application under controlled conditions at the field scale (5 sites, sand clay, ca 1 2 ha) Function as an early-warning system Do pesticides applied in accordance with current regulation leach in unacceptable concentrations? The programme is now an integral part of the registration process For pesticides already on the market, i.e. postauthorisation

11 Groundwater monitoring (ctd) No clear definition of which pesticides are included in the PLAP programme (mainly those that narrowly pass the modelling assessment) However, this does not apply for pesticides that narrowly fail the modelling assessment No clear statement on how results from the PLAP program feed back into the authorisation process Distinguish between findings originating from drainage water vs from groundwater Distinguish between concentrations exceeding 0.1 µg/l in single samples vs the annual average concentration

12 Groundwater monitoring (ctd) Results from the PLAP programme have direct effect on the authorisation and the review also noted e.g.: Environmental conditions during the experiments are normally not considered in decision making The relative vulnerability of the locations are not (yet) fully estimated (in relation to all Danish arable land)

13 Groundwater monitoring (ctd) Grundvandsovervågning GVO (started in 1989) and assess the overall groundwater situation, i.e. pesticide applications under real-world conditions Include monitoring data from The Groundwater Monitoring Programme (GRUMO) The Waterworks Well Monitoring Programme (WWMP) Data stored in a publically available database (JUPITER)

14 Groundwater monitoring (ctd) The GRUMO program is becoming more targeted towards vulnerable locations over time The WWMP program on the other hand is becoming targeted towards less vulnerable locations (contaminated wells closed down) Strong focus on pesticides now banned and their metabolites

15 Groundwater monitoring (conclusions GVO) Necessary that changes in programmes are communicated effectively, so the implications for the results are clear for end-users and general public Recommended to try to identify the sources of significant positive samples, such that these are not held against agriculture when agriculture is not the source It would be beneficial to further characterise Danish agricultural soils, with respect to their leaching vulnerability of pesticides Helpful for the authorisation procedure/decision making and also for management of groundwater abstraction areas

16 Management There is a potential to take into account pesticide management within borehole vicinity zones Would require mandatory definition of vicinity zones (all or only those defined as vulnerable)

17 Management (ctd) The regulatory process could then be refined to include three options: Authorise without any restrictions (no unacceptable risk for leaching to groundwater) Do not authorise (unacceptable risk for leaching to groundwater) Authorise but with a legal requirement for changes to use under some prescribe conditions e.g. no use in vicinity zones, or restriction on maximum use rate, application timing etc in these areas

18 Conclusions The very conservative authorisation process in Denmark regarding leaching to groundwater may lead to a lower availability of PPP and thereby increase the risk of resistance problems in Danish crop production It might be possible to relieve some of the specific Danish requirements in the authorisation process without impairing the quality of the groundwater in Denmark

19 We wish to thank all persons involved in the review for excellent support with documentation, presentations and discussions