Max and Jack, Caroline Clayton's sons, are only seven and two, but already they are passionate about cars. "They hurtle around pushing them, they're absolutely fascinated," says their mother.
As cars and their polluting exhaust fumes take up a chapter in Clayton's latest book, she is already agonising over her sons' enthusiasm. "I have to start training them to be responsible car users," she sighs.
So it's a shame that Dirty Planet, published by the Women's Press and commissioned by Friends of the Earth, is targeted solely at teenage girls. After all, it's grown-up boys, with their cars, factories and weapons, who cause many of the Earth's environmental problems. Most of the grim facts in this book are as relevant to boys as to girls.
In fact, the trend that most rattled Clayton when she was writing Dirty Planet was the decline in male fertility. She cites research suggesting that the low sperm counts of men living in the Thames area may be caused by hormone-disrupting chemicals, or "gender benders", in London's water supply. These chemicals are known to make male fish develop female characteristics.
Dirty Planet offers a detailed introduction to such problems and suggests what teenagers can do to help solve them. Chapters, each starting with a handful of facts (did you know that there are oxygen bars in smoggy Beijing?) cover air quality, car pollution, filthy oceans, industrial chemicals, recycling, nuclear power and climate change.
This gloomy description of the planet's state is offset by tips for green action and interviews with teenagers. Clayton steers away from the more extreme activists - the eco-warriors who throw over school to live in a threatened tree. "These are ordinary teenage girls," she says of the young women in her book.
Kruti Parekh, 15, from Maharashtra, western India, fed up with her town's stinking rubbish dumps, set up a "vermiculture project", which uses deep-burrowing earthworms to compost organic waste. In Benoni, South Africa, Theresia van der Merwe, 15, joined an environmental group which persuaded the council to stop dumping rubbish on wetlands near her home. As a result, bullfrogs and flamingos have returned. And in Cornwall, surfer Nicola Bunt joined Surfers against Sewage to campaign against the dumping of sewage at sea.
At the start of the 1990s, Clayton was the editor of Young Telegraph, the Daily Telegraph's youth supplement. Se says most of the letters in her postbag expressed anxieties about the environment. "The letter writers were worried sick. Now young people are even more worried than they were in 1994. Perhaps it's because we're moving into a new millennium. There's no sign of green fatigue."
Friends of the Earth gets 6,000 enquiries a year from young people, teachers and youth workers. Its website includes a Factory Watch, where you can discover which companies are polluting your neighbourhood by typing in your postcode. But until FoE commissioned Clayton to write Dirty Planet, it had little literature aimed specifically at teenagers.
Now Clayton is full of ideas about how the book can be used in secondary schools. Dirty Planet's tips on socially responsible business practices could be used to teach business studies, and the section on how to influence the media could underpin media studies project work. With citizenship studies becoming part of the curriculum from September, one of the book's aims is to help teenagers become active citizens, empowered to seek environmental justice.
The book's flaw is that it expresses only one point of view - that of a campaigning organisation. There are no challenges to FoE's commandments. Recycling is indisputably A Good Thing and GM foods are Bad (even though some argue that the technology has the potential to feed the world's starving masses).
Clayton acknowledges the criticism. "It is a publication for FoE. You could dispute every argument in there, and no doubt car manufacturers would. This book could be used as a starting point, with teachers asking pupils to discuss and do more research to get the bigger picture."
So does she practise what she preaches, forgoing make-up or clothes that need dry-cleaning? "Well, I use terry nappies rather than disposables. It's better to wash nappies than have plastic lying around for 200 years. But you can't expect everyone to do everything advocated. I might be guilty of leaving my television on standby - a terrible thing to do - but I try to look after the planet.
"Teenagers now are encouraged to ask questions, to push the boundaries. They have access to the Internet- a powerful tool to help them find out what is going on. It would be nice if this book helped a generation putthe environment first."And maybe soon there'llbe a Dirty Planet guide for teenage boys?
Dirty Planet: the FoE guide to pollution and what you can do about it will be published by The Women's Press on February 17, priced pound;4.99