NIAB - National Institute of Agricultural Botany

Orson's Oracle

...and then came the rules

Posted on 10/01/2012 by Jim Orson


I was listening to one of my favourite tracks on my Christmas present over the holiday period. The song describes the opening-up of the US prairies and has a line; ‘First came the churches, then came the schools, then came the lawyers and then came the rules’. Does anyone know which song it is?

We may choose a different set of institutions that influence current developments in society, but the end point is the same. There would have to be, at least, an indirect reference to laboratories - if they can measure it, we get a rule. Mycotoxins in cereals and pesticides in water are cases in point.

Perhaps the most extreme example of this is the Environmental Quality Standard (EQS) for cypermethrin in water bodies - rivers and lakes - at 0.1 parts per trillion (0.0000000000001 by weight). I’ve long known that this pesticide could be a threat to aquatic life, but I didn’t know it was that risky! And yes, the chemists claim that they can accurately measure this concentration in water.

EQSs are set for all chemicals, not just pesticides, which may be deemed to be a threat to the ecological status of water bodies. In 2011 nine widely used pesticides were listed by the EU as being a particular threat. Of those, only chlorpyrifos still remains on the UK market, and then only by a thread.

Gone are trifluralin, isoproturon, simazine, atrazine, alachlor, diuron, chlorfenviphos and endosulfan. All but one of this group failed to get approval in the EU during the re-registration process, although the threat to water may not have been the main reason why some of these failed to get approval.


Isoproturon was the other active ingredient that achieved EU approval. However, UK authorisation was not granted for products delivering 1,500 g ai/ha. I’ve assumed that this was because of the threat to water ecosystems and nobody seems to say anything different. In the case of isoproturon, the EQS is well above the drinking water standard of 0.1 parts per billion (0.0000000001 by weight), but obviously not high enough to allow us to use 1,500 g ai/ha.

Not to be outdone by the EU, the UK also had its own list of chemicals deemed to be a threat to water. This list has had a better survival rate through the re-registration system, with only diazinon failing to get EU approval.

Now, with renewed zeal, the EU and the UK are preparing new lists of chemicals that pose a threat to the ecological status of water. There are a few pesticides on the draft EU list, and the only one of any significance in UK arable farming is bifenox (Fox). However, the draft UK list includes methiocarb (Draza), chlorothalonil (Bravo) and...wait for it...glyphosate.

Should they be on the final agreed list, their EQS’s will be established and their presence will be monitored in water bodies. Fortunately, with the possible exception of chlorothalonil, these pesticides are not liable to significant movement through the soil to land drains, which means that the main source in water is likely to be from point sources such as spray fill areas. Hence, their appearance in water is largely under the control of users.

Compared to isoproturon, chlorothalonil is less prone to move through the soil, is used at a lower dose, and is typically used at a time of year when drains are not running. But, it is being detected in water courses in France.

Should chlorothalonil get on the finally agreed UK list, its EQS will be critically important to its future. Let us hope that this valuable pesticide does not fall foul of the analytical chemists and become another victim of the rules.

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