Pesticides and Drinking Water – urgent notice

The Department of Agriculture, Food and the Marine have advised HAI that there have been some recent pesticide-related breaches of drinking water quality in Meath (possibly related to amateur use of dicamba and mecoprop).

The regulatory compliance level for any pesticide in treated drinking water, and also in untreated water bodies used for the supply of drinking water, is 0.1 microgram/L (1 part in 10 billion). This is a blanket cut-off value that applies to all pesticides irrespective of type. Exceedance does not automatically mean a health risk, since the level required to impact on human health would be much higher for nearly every pesticide. However it is a legal value that must be complied with. Compliance is a considerable challenge, since the standard is so low that a single drop of pesticide would be enough to cause an exceedance along 30 km of a typical small stream.

A drinking water sample taken on behalf of Irish Water on 8th June from the Accord Office in Drogheda, served by the Staleen water treatment plant, contained dicamba (0.128 microgram/L) and mecoprop (0.633 microgram/L). The relevant drinking water catchment area where input(s) may have occurred is along the River Boyne, west of Drogheda towards Navan.

A drinking water sample taken on behalf of Irish Water on 6th June from Navan Hire, served by Liscarton water treatment plant, contained dicamba (0.342 microgram/L). The relevant drinking water catchment area where input(s) may have occurred is along the River Blackwater, which is a tributary of the Boyne.

There is a reasonable possibility that the exposure pattern for the sample containing excedances of dicamba and mecoprop resulted from use of products containing both substances.

The following product combinations, containing both dicamba and mecoprop-P, and their uses that are currently authorised are as follows:

• dicamba + mecoprop-P (amateur, amenity grassland, cereals);
• dicamba +MCPA + mecoprop-P (amenity grassland, cereals, grassland-seed crops);
• dicamba + ferrous sulphate + mecoprop-P (amateur) and
• 2,4-D + dicamba + MCPA + mecoprop-P (amateur, amenity grassland).

It seems possible that amateur use in home gardens may have contributed to the observed exposure profile in this case. Relevant amateur use products are as follows:

• dicamba + mecoprop-P (amateur) [Doff Lawn Weedkiller, GreenForce Clover Lawn Weedkiller, GreenForce Dandelion & Daisy Weedkiller, GreenForce Dandelion & Daisy Weedkiller Ready to Use, GreenForce Lawn Weedkiller, GreenForce Lawn Weedkiller Ready to Use, GreenForce Lawn Weedkiller & Feed, Homebase Lawn Weedkiller, Hytrol Lawn Weedkiller, Hytrol Lawn Weedkiller Ready to Use, Hytrol Nettle Killer, Pestshield New Formula Lawn Weedkiller, Resolva Lawn Weedkiller Extra Concentrate, Resolva Lawn Weedkiller Extra Ready to Use]
• dicamba + ferrous sulphate + mecoprop-P (amateur) [Hygeia Lawn Feed, Weed and Mosskiller]
• 2,4-D + dicamba + MCPA + mecoprop-P (amateur) [Dicophar Lawn Weedkiller, Dicophar RTU]

The Department would like to ensure that users purchasing these products in the Meath/Louth area, and indeed users purchasing amateur-use herbicide products anywhere in Ireland, are given some basic information at point of sale on the need to protect drinking water quality when using these products and some basic measures to follow. Amateur users should be aware of what pesticides are, how easily they can end up in water bodies and simple steps that they can take.

Pertinent information to be given to amateur users may include the following:

• Examples of pesticide products include weedkillers, insecticides, fungicides, rodent poisons and slug pellets.
• Pesticides can easily end up in water bodies through careless storage, handling or use. A single drop getting into a small stream would be enough to breach the drinking water quality standard for pesticides for 30 km.
• Only use pesticides if necessary and consider non-chemical methods instead.
• If using pesticides be sure to take note of the location of any nearby water bodies and ALWAYS follow the instructions on the product label.
• NEVER pour unused pesticide, or container washings, down a drain or sink.

Refer to this EPA Pesticide Leaflet for advice to be given to your customers buying pesticides and for further information visit the relevant section of the Department’s website here.