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:
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:
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: