A   serious pesticide pollution has hit the upper River Kennet this week   resulting in an almost total wipe out of the aquatic invertebrates in much of   a 15 km stretch downstream from Marlborough to Hungerford.

As yet fish   populations remain unscathed but there are concerns that there may be   residual effects that are still to come. Much of this stretch of famous chalk   river, renowned for its trout fishing, is situated within a SSSI.

The   Environment Agency has identified the pollutant as chlorpyrifos, an   organophosphate that is highly toxic to insect life. The source is as yet   unknown but it entered the river by passing through the Marlborough Sewage   Treatment Works. No damage appears to have been done to the works themselves.   A team of specialists from both Thames Water and the EA are working together   on trying to track down the cause and origins of the pollution.

Chlorpyrifos   is used on lawns and golf courses and to tackle insects on crops and some   soft fruits. It is the same pollutant that wiped out a large section of the   River Wey in 2003 and led to a significant fish kill on the Sussex Ouse in   2001. It was banned in Singapore in 2009 for use in termite control in soil   and the United States phased out chlorpyrifos for use in buildings and residential   homes and pre-construction sites from 2001 due to public health and   environmental concerns. The US Environmental Protection Agency (EPA) has   moved to limit the use of the chemical near salmon rivers because of possible   damage to fish and has been petitioned to introduce a total ban following   reports that it can cause damage to human health.

The   pollution was discovered on Monday by volunteer riverfly monitors working for   Action for the River Kennet (ARK).   In their statement ARK said:  "The Environment Agency were immediately alerted, as well as the   downstream river keepers. By this morning the pollution had spread from the   Elcot Lane area to beyond Ramsbury, but the river upstream of Elcot was   healthy.

The   Environment Agency are currently investigating the extent and cause of the   incident. Although few fish appear to have been killed the absence of   invertebrates means that both fish and other wildlife have nothing to eat,   which will have a serious impact on the river's ecology. ARK have a team of   over 50 volunteer riverfly monitors who monitor over 20 sites on the Kennet   every month."

The Angling   Trust have been involved throughout and have been liaising with both Thames   Water and the EA. Their Campaigns Coordinator Martin Salter will be attending   the forthcoming meeting organised by the EA to discuss the incident with   river keepers and fishery interests.

Mark   Owen, Freshwater and Environment Campaigns Manager for the Angling Trust said:  "This is a truly appalling pollution which seems to have been caused by   a small amount of lethal pesticide which entered the sewerage system in the   Marlborough area. We very much support the work to track down both the source   and those responsible for the pollution and our colleagues at Fish Legal are   ready to take action on behalf of our member clubs.

Even if   fish stocks remain untouched there is now precious little left for the fish   or other wildlife to eat which is why the Angling Trust is calling for   measures to try and recolonise the affected stretches with invertebrates as   quickly as possible.

We will   support any measures the EA recommend to restore invertebrate communities in   a sustainable manner."

Martin   Salter added:  "The Angling Trust wants to know why on earth a lethal chemical like   chlorpyriphos is allowed to be used anywhere near a river or watercourse.   Apparently the 15 kms wipeout of invertebrates between Marlborough and   Hungerford may have been caused by as little as a couple of spoonfuls of the   stuff. If this is the case then the sooner we follow the lead of Singapore   and America and ban it the better.

We shall be   asking the Environment Agency to immediately add this chemical to their Watch   List of Priority Hazardous Substances to ensure all water bodies are   monitored for the presence or absence of this chemical in our rivers."