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MCPA, metolachlor, terbuthylazine and 2-4 D

Four other herbicides, regulated as RBSPs, were reported as exceeding their EQS by at least 4 Member States: MCPA, metolachlor, terbuthylazine and 2-4 D.

MCPA is a widely used herbicide, used to control weeds in cereals and other crops. Its main effects in water are upon aquatic plants and algae, inhibiting photosynthesis and carbohydrate production and it can be harmful to fish.

Metolachlor is a pre-emergence herbicide, inhibiting germination of grass species and so allowing crops to grow better. EQS are set to protect algae, as the most sensitive aquatic organisms.

Terbuthylazine is a systemic herbicide, used to control grass and broad-leaved weeds and works as a herbicide by interfering with photosynthesis. The major harmful effect in water is on invertebrates.

2-4 D (2,4-Dichlorophenoxyacetic acid) is a selective herbicide, which effects broad leaved weeds. In water, aquatic plants are the most sensitive organism.

(Lewis et al, 2016; UBA, 2011 and 2016)

MCPA and metolachlor both exceeded national EQS in over 100 surface water bodies. Emissions to water data are not available for these RBSPs.

Outlook for pesticides

EU-wide restrictions on use of pesticides should lead to improvements in surface water chemical status for those substances. That we may be seeing that in the data, with relatively few water bodies failing for pesticides, should be understood with caution.

Most pesticides are not regulated under the WFD and so are not reported upon at the EU level. Whole classes of pesticides – fungicides and bactericides – are missing. Substitution of heavily- restricted pesticides, by others which face less scrutiny in the water legislation, means we miss information on many other substances.