It's time someone injected some common sense into the issue of supermarkets attempting to show their concern for the environment by curtailing the use of lightweight plastic carrier bags.

The bags are made largely from recycled plastic (about 80 per cent) and naphtha, a mixture of by-products and waste from oil refining.

So, as long as we use oil, we shall continue to produce naphtha, so why not put it to good use?

Secondly, it is not true that plastic bags are not reusable.

Many of us, after using the bags to carry our purchases, use them as liners for pedal bins in kitchens and bathrooms and disposal of household waste. Thirdly, the bag is lightweight (about 10g), strong, and offers a safe and convenient way of carrying our shopping. Fourthly, most bags are now biodegradable and when they eventually end their days in landfill, they will decompose, leaving water and carbon dioxide, just as many other organic materials do. Even if they are not placed in landfill, they will eventually disintegrate, leaving only a little dust.

Of course, we have all seen the picture of a baby turtle who died after becoming entangled in a plastic bag.

That sort of thing will happen from time to time, as long as people fail to dispose of the bags properly.

But was the death of that turtle any worse than the fate met daily by small mammals and birds on our roads?

No-one seems to want to stop using cars in order to curb that carnage. I'm afraid the concern for plastic bags is largely a myth and is the sort of 'environmental concern' shown by businesses which, in practice, don't care for very much, apart from currying favour with the customer and boosting profits.

Don't be conned by big business or by misguided pressure groups. JOHN SANDALLS (Dr) Environmental scientist Locks Lane Wantage