If you spend a large proportion of your day struggling through overcrowded streets, breathing in smog and dodging potential muggers, then the chances are that at some point you have dreamed of packing it all in and moving to the country. You're not alone: each year, about 115,000 city dwellers in England make the dream a reality, going rural in search of wide-open spaces, fresh air and a healthy place to raise their kids.

Over the past four years, according to the Countryside Agency, 352,000 more people moved to the countryside than left it. Nearly half of these are aged 25 to 44: many of them, presumably, thinking of raising apple-cheeked country kids, not pale and spectral urban ones. But last Friday the British Medical Association (BMA) raised a huge question mark over the health benefits of country living when it issued a report, Healthcare in a Rural Setting, that said remoteness, lack of public transport and the centralisation of health services mean the countryside may not be such a healthy place to live after all. In recent weeks there have also been reports about cancer-causing fertilisers and the burgeoning rural drugs market. Country living may not, then, be as idyllic as you'd think.

Government health statistics show that you're more likely to be healthier and to live longer in the country than the city, but rural life is not all Range Rovers and Labradors. Dr Vivienne Nathanson, the BMA's head of ethics and science, says: "A major problem is the myth of the 'rural idyll'. Deprivation in rural communities has been ignored for a long time. There is a real case of the haves and the have-nots," with "pockets of deprivation" in the countryside where ill-health is as bad, if not worse than it is in urban areas. (According to the Countryside Agency, the three lowest weekly wage rates in England are in Cornwall, Northumberland and the Isle of Wight).

Recent government figures show that 83% of parishes have no GP based there, and the BMA report says many remoter places, such as deprived South Wales valleys, are now facing a GP recruitment crisis. Country people tend to be more "self-sufficient" and consequently, when they finally do get to a doctor, their condition is often more advanced. Studies show that the further you live from specialist cancer centres, the poorer your chances of survival. People from remote or rural areas may not be diagnosed as quickly as urban cancer patients. The more remote you are, the less likely you are to have your stomach, breast or colorectal cancer diagnosed and the less likely you will be to survive after diagnosis for prostate and lung cancer. To tackle this, the BMA is calling for creative new approaches to rural health care: the expanded use of telemedicine - which involves using technologies such as interactive video, digital imaging and electronic data transmission - to communicate with patients.

You are, of course, still more likely to die - of any cause - if you live in the city (a baby boy born in Manchester has a life expectancy of 71 years, while one born in Rutland can expect to last up to 79.5 years). This is largely linked to poverty. Mortality from cancer, for instance, is 60% higher in Tower Hamlets and Liverpool than it is in East Dorset, and in wealthier rural areas access to healthcare can be excellent: in north-east Oxfordshire, 78% of older people get flu jabs, whereas in Southwark, only 49% do.

Many city dwellers, of course, downshift for the "fresh air" (one recent survey found that almost half of us in the UK fear our health is being harmed by traffic pollution). The National Society for Clean Air says we are right: airborne pollutants such as nitrogen dioxide, sulphur dioxide, carbon monoxide and "volatile organic compounds" released in vehicle exhaust fumes, solvents and motor fuels can cause anything from respiratory disease, eye and throat irritation and leukaemia, to viral and bacterial infections, fetal damage, headaches, fatigue and stress. Friends of the Earth (FOE), in a recent campaign, highlighted areas around airports, in particular Heathrow, Gatwick, Stansted and Birmingham, that are polluted not only by aircraft but also increased road traffic to the terminals.

If you are an asthma sufferer this can be a very real threat. A spokesperson for Asthma UK says that while asthma rates aren't radically different between town and country, "there is enough evidence now that air pollution does play a part in causing asthma. One study found that children living closer to a main road had a higher chance of developing asthma". London does, suspiciously, also have a particularly high rate of mortality from respiratory diseases.

Country life is thus less likely to aggravate your asthma. If you live on a farm, your child's chances of developing asthma and allergies in the first place could also be lower than if you lived in the city. One 1999 report found that young children in regular contact with farm animals are less likely to develop allergies (they were three times less sensitive to hay fever and nearly four times less likely to suffer from asthma than city kids).

Industrial or urban pollution could also cause more than asthma. FOE has campaigned recently against cancer-causing emissions from factories in areas including Middlesbrough, Cardiff and Southampton. One study linked long-term exposure by workers to diesel exhaust fumes with a higher rate of lung cancer. Another study, last year, of children living very close to petrol stations suggested a link between breathing carbon monoxide and leukaemia. And this month, researchers claimed, controversially, that children born near emissions "hotspots" where industrial and environmental pollutants such as 1,3-butadiene, dioxins and benzopyrene are pumped out, have a higher chance of dying from leukaemia. Dr Lesley Walker, director of cancer information at Cancer Research UK, says this study is far from conclusive and the evidence is "thin... not least because cancers in children are rare and some may have an underlying genetic basis". Emma Knight, also of Cancer Research UK, emphasises that more research is needed, and "the only truly known cause of lung cancer is smoking" - which will damage you whether you live in Cornwall or Croydon.

If you move to the country your children won't, of course, be inhaling 17 cigarettes' worth of exhaust fumes every time they step out the door, but other chemicals may be equally undesirable. Government health advisers this month announced that pesticides may cause prostate cancer (farmers and farm workers have a high rate of prostate cancer) and there is growing evidence of a link between fertilisers and Parkinson's disease. FOE has also noted that while farm workers wear protective gear for crop spraying, people who live near fields being treated, including children, don't.

"There is currently very little evidence to suggest that [pesticides and pollutants] substantially increase our cancer risk in the levels we are exposed to in our daily lives," says Knight. Indeed, she adds, "any cancer risk associated with these factors is likely to pale into insignificance at the side of known causes such as smoking, an unhealthy diet or lack of exercise and sunlight." Still, you have to wonder which is worse: letting your children gambol through fertiliser-drenched fields, or allowing them to fill their lungs with carbon monoxide every day.

When it comes to general pollution, Elizabeth Salter Green, director of the toxics programme for the World Wildlife Fund, says: "Industrial chemicals, such as flame retardants, are a major concern, whether you live in a rural or an urban area." These chemicals may start as gas emissions from factories, which contaminate the rain water then, in turn, contaminate our soil, waterways and hence the entire food chain. Toxic chemicals can also leach into the food chain via landfill sites. "Ninety per cent of human toxicity comes from the food and water you consume", she says - and most of us are consuming food from the same source (Tesco's, largely).

Many families move to the country to be "safer". But will they be? The Health and Safety Executive has described agriculture as the most hazardous industry to work in. Recent government statistics on geographical variations in health show that areas with high mortality rates from accidents are less concentrated in urban areas than for all causes of death. Traffic levels are rising fastest on rural roads, and casualty rates are falling more slowly on rural than on urban roads. And if one of these perils does get you, you may also have to wait longer for your ambulance: in 2002/3, 54% of rural ambulance services responded to "life-threatening" calls within eight minutes, compared with 63% of urban services.

Your injuries are more likely to be self-inflicted if you live in the country. Young rural men have higher suicide rates than their urban peers and, say the Samaritans, between 1991 and 1996 there were 190 farming suicides - one every 11 days. Indeed, farmers and vets are among the six male occupational groups with the highest suicide rates in the UK (and you can forget desperate housewives: farmers' wives have a suicide rate more than 20% above the average.) The BMA report says isolation, lack of anonymity, lack of specialist resources and that "culture of self-sufficiency" are all barriers to adequate mental health provisions in rural areas.

Many parents leave the city thinking it will keep their kids away from drugs. But in 2004, the market towns of Spalding and Boston in Lincolnshire clocked up the third-highest proportion of drug-related deaths in England and Wales (higher than Manchester). A report in 2000 revealed that 6% of rural 16- to 29-year-olds said they had used a class-A drug in the previous year, compared with 8% in urban areas. Those picturesque hamlets may not, after all, be quite as wholesome as you'd think.

Local opinion

'I don't let the children outside for too long'

Jude and Rob MacKay live in Greater Manchester with their children Beth, two, and Grace, 11 months. Rob works in IT and Jude looks after the children.

Like many city dwellers, the MacKays moved to Salford four years ago because of their jobs. They then both worked for the Eden project, a Christian initiative that posts volunteers to live and work in rough areas of Manchester on a long-term basis. "It's not the nicest place," admits Jude of their neighbourhood, Seedley. "There aren't many green spaces and there are a lot of boarded-up houses, but things are getting better." She thinks the best thing about inner-city living is the convenience factor. "I've got everything I need within five minutes' walk, including a healthcare clinic," she says. "There are hospitals nearby and it's only 10 minutes into central Manchester on the tram."

Jude does worry about the effects of pollution on the children's health, but accepts it as a fact of life. "We don't have a garden, so I just don't let the children outside for too long," she says, adding that they make an effort to drive to the Lake District or the coast at the weekend. "I've not noticed any health problems in my two as a result of breathing in polluted air," she says.

Seedley has been earmarked by the government as a regeneration zone, which means a lot of money has poured into the district. House prices are cheap: the MacKays' terrace cost just £32,000 a few years ago - and new amenities have popped up everywhere. "There's a swimming pool, shops and good primary schools - everything you need, really," says Jude.

Because the area is disadvantaged, the MacKays are well aware of the problems with drugs and crime, but Jude reckons these issues are not confined to big cities. "It can happen in the country too," she stresses. "And anyway, although I worry about it a bit, we believe that if we bring our children up with morals and an understanding of how to say no, hopefully they'll be OK."

The MacKays think they will stay in the area until the girls start secondary school. "But," says Jude, "I don't ever see us living in the country. I'd miss having everything nearby. Plus I want the children to be independent, and not relying on us for lifts everywhere."

'We rely on the car to get everywhere'

After living in London for 15 years, Emma and Huw Bowles moved to Tormarton in the Cotswolds four months ago with their children James, four, and Oliver, 21 months. Huw is financial director of an organic milk cooperative and Emma stays at home with Oliver.

"We were real Londoners," says Emma Bowles of their past life in Wimbledon, London. "We worked hard, played hard and all that cliched stuff. We both bought properties before getting married in 1999 and loved London life." Huw was working as a chartered accountant, then a consultant and finally as a financial director, while Emma worked in the commercial side of newspapers. "Then we had children," laughs Huw, "and everything changed."

The family spent a year in France before returning to live in a "picture- postcard" village in the Cotswolds in autumn last year. The children were the primary motive for upping sticks, with health benefits high on the list of advantages of rural living. "We were conscious of breathing problems suffered by the children of people we knew in London," says Huw. "James also had an eczema-like skin complaint, which has cleared up noticeably since moving out here."

The pair are aware of the hazards posed by the spraying of pesticides on nearby fields, but as Emma says, "It can't be any worse than pollution we would be subjecting ourselves and the children to in the city."

"The disadvantage of country life is probably the reliance on the car to get everywhere," admits Huw, who adds that they had to buy a second vehicle after the move. "Things take more planning; you can't just pop out for three pints on a whim and catch the tube home." But they say they are not worried about the inaccessibility of healthcare provisions. "Our nearest GP is three just miles away and it's only 15 minutes in the car to the nearest hospital," says Emma. In fact, Oliver was born several weeks early while they were on holiday in the area, and was rushed to hospital in a nearby town with no big difficulties.

They deliberately chose a village with good transport links, with the M4 and Bristol Parkway station a 20-minute drive away. "We didn't want to live anywhere too remote," says Emma.

· Interviews by Helen Pidd