Drinking water in Sussex breached European levels for a hazardous pesticide, The Argus has discovered.

Metaldehyde, a pesticide used to control slugs and snails across a range of crops, was found to breach EU guidelines in the River Arun late last year.

Levels of the slug repellent were twice discovered above EU standards in the Arun last year and in treated drinking water.

The chemical is classed as “moderately hazardous” by the World Health Organisation but Southern Water said there was no reason to expect any adverse effect on human health at the levels being detected.

The firm tests for metaldehyde at six locations where it abstracts raw water – water from rivers and reservoirs before it undergoes treatment – and where there is a potential for products to contaminate drinking water.

There were 152 water quality tests carried out on raw water in Sussex in 2011 and 2012.

On two occasions in the winter of 2012 tests showed that metaldehyde levels in the River Arun were recorded at 1.1 microgrammes per litre in October and 0.4 microgrammes per litre in November.

Following treatment, the water tested still exceeded the European standard, which is 0.1 microgrammes per litre.

Slug activity

A spokesman from Southern Water said the tests occurred during one of the wettest years on record where there was a significant increase in slug activity.

He added that there had not been any other occasions since when the levels have exceeded the EU standard.

Water UK, the body which represents water companies, issued a briefing paper on the problem of metaldehyde in drinking water sources in November.

'No threat'

Phill Mills, the director of water services at Water UK, said the situation was serious but that there was no threat to health.

He said: “The issue for water companies is that metaldehyde is particularly difficult to remove from water, even using existing advanced water treatment processes, which can ultimately lead to exceedances of the standard in drinking water supplies.”

Meyrick Gough, Southern Water’s water quality and strategy manager, said: “We have a close focus on this issue and work with the farming community to ensure responsible use of these products to protect the environment and our watercourses.”

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