What lies beneath: Plastics threat to UK beaches

At first glance Porthtowan beach looks like an advert for British Tourism. With white sand and turquoise sea bathed in bright sunshine, it appears to be the best seaside Cornwall has to offer. But just below the surface of this picture-postcard perfection is a darker and, at times, dangerously toxic scene.

Porthtowan is one of many beaches whose hidden filth contributed to the staggering drop in the number of beaches classed as fit for swimming in a recent survey by the Marine Conservation Society. And now campaigners have decided to take matters into their own hands.

Later this month, Surfers Against Sewage (SAS) will launch a grass-roots attempt to improve the state of the nation's beaches. Their beach-cleaning tour, launched to coincide with the start of the summer holidays, will use local volunteers at beaches around the country to collect as much waste as they can in a single day. It is hoped that the tour of England and Wales, which begins in Newquay on 29 July and finishes in Brighton on 3 August, will prompt further marine litter clean-ups around the country.

As the summer holidays approach, the cleanliness of our beaches has never been more important, but as picturesque Porthtowan illustrates, the problems are often hard to see.

This beach is home to more than half of the South-west's sewage-related debris (SRD). In fact, it is largely because of it that the South-west has the highest density of public, fishing and shipping litter, as well as SRD, in England. Despite this, however, Porthtowan continues to hold blue flag status – the hallmark of a supposedly clean and litter-free beach.

A closer inspection of one patch of seaweed along the tide line revealed more than 100 cotton-bud sticks. "This is not a good sign," said SAS campaigns manager Andy Cummins, throwing them into a bin bag. "People often assume our beaches are fine now, because you can't see the problems so easily. Small things like cotton-bud sticks are harder to see, but they're an indication that raw sewage is getting on to the beach, because people flush them down the loo."

Two storm drains, which overflow with sewage after wet weather, run into a river that comes out on the beach. After a rainy period, the spot can be positively toxic.

The latest beach survey by the Marine Conservation Society showed a decline of nearly 17 per cent in the number of beaches fit for swimming – the biggest year-on-year fall in the 22 years the MCS has been producing its annual guide – and the lowest level for seven years. The main problem is seawater contaminated with sewage, which can cause everything from ear, throat, skin and eye infections to gastroenteritis.

But of equal concern to environmentalists is plastics. Microscopic plastic pieces are contaminating our shores: from industrial waste, as well as rubbish dropped by the public.

The worst of these are the raw materials left from injection moulding, dubbed "mermaids' tears". Thousands of these plastic pellets lie hidden in sand on beaches around the UK. They are not picked up in more cosmetic beach inspections, but as with all plastics, they introduce potentially harmful chemicals into the marine food chain – and by extension to humans.

Fishing rope is another offender. In an hour's sweep of Porthtowan beach last week, more than 95 pieces of orange net were uncovered, a third of which were more than half a metre in length. Formerly made of hemp, which biodegrades more quickly, the nets were mended and cared for by fishermen because of the greater expense. Now netting is more commonly made from cheap plastic fibres which, when they break, are often tossed into the sea, where they take hundreds of years to decompose.

Despite the beach having had its daily clean by the council, SAS found 26 crisp and chocolate wrappers, as well as an armful of plastic bottles. All those with labels that can be read will be sent to their companies' headquarters as part of SAS's "return to offender" campaign. Cummins takes a two-litre Coke bottle, puts it in an envelope and takes it to post to Coca-Cola's UK offices in Hammersmith.

"We're aware that it's not the companies themselves that are dropping the litter, but we need to remind them that it's their responsibility to encourage people to dispose of them properly, as well as making them from packaging that breaks down more easily," he explained. "Plastic bottles take 450 years to decompose. Just think about that – it means that if Henry VIII had used plastic bottles at his last wedding party, then they would still be around now."

Return to offender

Surfers Against Sewage sends rubbish back to companies where it originated. Litter, picked up by volunteers and posted back, includes beer cans, sweet wrappers, cartons and bottles. Here are a few of the firms who got some of their own junk back last month: Tesco Stores Ltd; ASDA Stores Ltd; The Coca Cola Company; Innocent Ltd; Walkers Snack Foods Ltd; Nestle UK Ltd; Lidl UK GmbH; Budweiser Stag Brewing Company Ltd; Cadburys Plc; Unilever Plc; Carlsberg Group; and Bavaria Brouweri NV.