Thousands of doctors' records in North Cumbria are to be examined to discover if there has been any rise in the numbers of patients reporting respiratory illness since the incineration of animals began in the area as a result of foot and mouth disease.

Health concerns have been growing since the public health director of North Cumbria health authority, Dr Peter Tiplady, urged the Ministry of Agriculture to postpone incineration of animal carcasses until the Department of Health issued national safety guidelines.

The guidelines are expected to be published this week and will examine all public health issues surrounding the disposal of carcasses, from burial and incineration to rendering.

Much of the controversy has centred on dioxins - considered among the most poisonous manmade chemicals, which are known to interfere with immune and reproductive systems.

The fires lit during the first six weeks of the foot-and-mouth crisis have so far released 63g of dioxins into the atmosphere - 18 per cent of the UK's average annual emissions.

The DoH has already said it expected to 'step up' the monitoring of public health during the crisis in attempts to see if carcass disposal has impacted on the population. But there have also been concerns from North Cumbria and Devon HAs about possible links with asthma and other respiratory diseases in both districts, which have been among the hardest hit by foot and mouth disease.

A spokesman for North Cumbria said: 'There has been some anecdotal evidence suggesting that more people are going into surgeries with respiratory complaints, but the information is very sketchy at the moment. '

The authority will now trawl doctors' computer records from February to see if there has been a rise in patients reporting illnesses which could be linked to incineration.