Emerging contaminants in groundwater - NERC Open Research ...

OR/11/013
Table 4.4 Compounds with a possible risk but no usage data up to 2006
Compound Year Leaching
hazard score
Pyrosulam 2007 4
Aminopyralid 2005 4
Flazasulphuron 1989 3
4.3.3 Corroborating evidence for assessment
Worrall et al. (2000) used a list of 43 pesticides which had been reported in UK groundwater
up to 1993 to assess which were likely to be leachers. Of these, 12 appear in Table 4.3:
bentazone, chlorpyrifos, clopyralid, dicamba, ethofumasate, linuron, oxamyl, pendimethalin,
phenmedipham, propyzamide, triallate and triclopyr. Many other compounds in this survey
are no longer used in the UK, e.g. atrazine.
Gooddy et al. (2005) detected 23 pesticides in groundwater in south Yorkshire. Of these, 11
compounds appear in Table 4.3 and 9 compounds are no longer licensed. Three of the
remainder were assessed as leachers by this method, but excluded due to insufficient national
usage. Methiocarb was assessed as a non-leacher.
4.4 PESTICIDE METABOLITES
A separate assessment of pesticide metabolites needs to be made, as the physicochemical
properties, persistence and toxicity of these compounds may be very different from those of
their parent compounds. They may also be present at concentrations similar to or even
exceeding the parent compound (Box 3).
4.4.1 Existing UK assessments
Sinclair et al. (2010) reported measured concentrations in groundwater of the UK from the
Environment Agency and water companies for a range of compounds. The metabolites
detected were all from compounds no longer licensed in the UK (DDT and heptachlor) and
included op-DDE, pp-DDE, deethylatrazine, deisopropylatrazine, cis-heptachlor epoxide,
trans-heptachlor epoxide, op-TDE and pp-TDE.
Sinclair et al. (2010) then selected 53 pesticide metabolites from a total of 485 from UK
pesticides with available information for a desk study of metabolite impact on UK drinking
water based on their potential to contaminate water (Table A1.1, Appendix 1). This
assessment incorporated parent compound usage, formation rates in soil, persistence and
mobility and estimated toxicity and/or potential to exhibit pesticidal activity. The study
included compounds currently licensed and those which have recently lost approval, e.g.
aldicarb, atrazine and isoproturon. About half of the compounds had been identified during
environmental degradation as well as in mammalian toxicity testing of the parent. The study
included the estimated efficiency of removal during drinking water treatment as well as
during environmental degradation. The maximum predicted concentration in finished water
was for metazachlor sulfonic acid which is not considered to have pesticidal properties.
For five of the metabolites significant concentrations in drinking water were predicted by
their model. These were aldicarb sulphone (aldicarb metabolite), 3-carbamyl-1,2,4,5tetrachlorobenzoic
acid (chlorothalonil metabolite), cyanazine chloroacid (cyanazine
metabolite), desisopropyl atrazine and methomyl (thiodicarb metabolite and also parent
compound).
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