Julia Stephenson: The Green Goddess

Algae, swimmers and other varieties of pond life

This idyll was interrupted every week by the lugubrious pool-man bearing vats of chemicals emblazoned with skull-and-crossbones. This chlorine was deemed so poisonous that we children could only swim in the brief moments between chemical dumping.

Maybe this was wise. Chlorine by-products in swimming pools are linked to higher incidences of asthma, skin disease, lung damage, stillbirths, miscarriages and bladder cancer, according to research conducted in the US, Canada, Norway, Australia and Belgium. One researcher noted that 10-year-old children spending an average of 1.8 hours a week in a pool environment suffered lung damage she'd expect in an adult smoker.

Dr K Thickett of the Occupational Lung Diseases Unit at the Birmingham Heartlands Hospital says swimmers are more prone to asthma than other athletes. "Our results show that nitrogen trichloride (produced by chlorine) is a cause of occupational asthma in swimming-pool workers like lifeguards and instructors." When asthma patients stayed away from pools, asthma symptoms were often resolved.

There is a non-chemical alternative. Pond pools, which are homes to aquatic plants, have been popular in Germany for years. Now they're taking off here. Britain's natural-pool pioneer, Michael Littlewood, the author of Natural Swimming Pools, explains that in a pond the water is cleansed naturally using the purifying properties of the plants, with a small filter to extract surface debris and a small pump to keep the water circulating through the planting area. It's a wonderful way to harness nature's intelligence.

Public swimming ponds already exist. In London, there are the Hampstead Heath ponds and the Serpentine pool in Hyde Park. During the hot spell, I stumbled across this delightful paradise, which isn't well known. One can swim "eau naturel" among swans and ducks: the city feels miles away.

The mossy green of natural ponds may take some getting used to. A bit of algae, however, is part of the charm and may even be good for you - Harrods offers an "algae wrap" where a therapist smears you with the stuff, wraps you in foil and leaves you for 40 minutes before relieving you of £150. I get this beauty treatment for the princely sum of £3.50 when I swim at the Serpentine, one of the many examples where going green improves your quality of life and bank balance. To find your nearest pond, visit the excellent website www.river-swimming. co.uk, which lists public swimming ponds nationwide and promotes all open swimming, from tidal pools to the sea.

Despite their benefits, these lovely swimming spots are under constant threat from public-safety busybodies. These non-elected people are trying to close many harmless open-air swimming spaces. Hampstead's pond swimmers have won a famous victory over a proposed ban, but the future of many other ponds is in the balance. Use them or lose them!

j.stephenson@independent.co.uk