SOURCE OF THE PROBLEM Somerhill Stream north of Tudeley PHOTO: Craig Matthews

TOXIC pesticide is polluting Somerhill Stream and threatening the local wildlife because it is poisoning the insect population. And experts are blaming parasite treatments for household pets.

The river, which runs for five miles from Tonbridge near Tudeley to Southborough, was the third worst affected in the UK according to a study carried out by the Environment Agency.

The tests carried out on 23 sites across the UK have revealed that Somerhill Stream contains ‘chronic’ quantities of neonicotinoid – and even goes beyond that definition. Only the River Waveney, which divides Norfolk and Suffolk, and the River Tame in the West Midlands exceed the levels found here – and the latter’s figures were skewed by a one-off polluting event.

Matt Shardlow, Chief Executive of the conservation group Buglife, stated: “It can be concluded that these rivers will have suffered from significant ecological harm.

“The levels of contamination are sufficient to cause a range of sublethal effects on mayflies, caddisflies, flies and other invertebrates, and to result in steep declines in invertebrate abundance and declines in bird populations.”

The Environment Secretary Michael Gove issued a statement before Christmas calling for tougher restrictions on these pesticides because of growing scientific evidence of harmful effects – especially on bees and other pollinators, some 1,500 of which have a crucial role to play in the food industry.

Buglife produced a report on the Agency’s findings, and say the presence of such insecticides is often a result of agricultural use, mainly in arable farming. It also notes the waste water treatment plant at North Farm.

But Somerhill Stream showed a particularly high amount of one particular toxin, imidacloprid, which accounted for 99.3 per cent of its insecticide content.

‘The levels of contamination are sufficient to result in steep declines in bird populations’

Its contamination of 0.13 microgrammes per litre was far more than any other river in the study. The next worst, the River Ouse in Bedfordshire, showed just a third of that concentration (0.04) but it flows through arable land.

Imidacloprid usually indicates the intense presence of horticulture, notably potted plants in nurseries and other greenhouse businesses.

But because there are no large-scale garden centres in the vicinity, the investigators concluded that the damage in the Tonbridge area may be caused by treatments to kill parasites such as fleas or ticks in cats and dogs.

The report by the invertebrate specialists states: “The four most imidacloprid-polluted sites have significant areas of urban catchment and waste water treatment inflows, and three of these are very predominantly urban.

“This strongly suggests arable land is not the primary source of imidacloprid pollution.

“Two potential alternative sources exist: Treatments on potted plants, in greenhouses, garden centres, amenity areas or gardens, and ectoparasite treatments on pets.

“Veterinary pour-on and collar uses are likely to be the prime source of pollution, and are therefore implicated in three waterbodies – the Tame, Wyke and Somerhill Stream – exceeding their chronic pollution limits.”

Mr Shardlow added: “Invertebrate populations in rivers and other waterbodies -represent an important part of the UK’s biodiversity.

“They provide valuable ecosystem services, recycling organic matter and keeping rivers clean. In addition they provide food for fish and birds.

“Given the impacts caused by pollution at comparable levels in other countries, these results are an alarm bell for the health of our invertebrate, fish and bird populations.

“It is apparent from the data that the use of imidacloprid as a veterinary medicine is a cause of serious concern. Pollution from flea treatments is the most likely source of chronic and harmful pollution.”

Since 2013, the EU has banned the use of three pesticides, including imidacloprid, on crops attractive to bees such as oilseed rape.

But they can be used to treat sugar beet and as seed treatments for winter cereals, and the European Commission wants them only to be used on greenhouse plants.

Elisa Orchard of the Environment Agency told the Times: “We use technology to help us pinpoint the sources of pollution and then use this information to target our work. It’s all about identifying the locations in a catchment where pollution is likely to be worst.

“We’ll work with farmers to alert them to the risk and let them know where they can get advice. We will prosecute serious or persistent offenders.”

Fine for waste treatment

Southern Water was fined £24,000 with costs of £33,218 last year after discharging too much treated sewage into Somerhill Stream from Tunbridge Wells North Waste Water Treatment Works.

An Environment Agency spokesman said the breach caused oxygen levels in the water to drop, which could have damaged plants and fish. Southern Water said it would spend £6million on improvements at the works.