Anglesey has emerged as an area with a high incidence of cancer which could be related to sexual behaviour; more cancers of the cervix, penis and lip have been found. Cervical cancer is associated with viral infection, with starting a sexual life early and with having many sexual partners.
Another key finding is the 40 per cent variation in breast cancer in older women. Rates are high in southern England and very low, by comparison, in the North.
Dr Gordon McVie, scientific director of the Cancer Research Campaign, said yesterday that it was looking as if an affluent lifestyle was implicated. 'The difference is far too big to be explained by genes. We have to take a look at diet, at excess calories. It may be that diet is linked in a very complicated way,' he said.
Dr Anthony Swerdlow, co- author of the Atlas of Cancer Incidence in England and Wales 1968-1985, said that reproductive factors could also be involved, again related to more affluent lifestyles.
'A 40 per cent difference is not so great but breast cancer is very common so it represents a lots of cases. Having babies later and having fewer children are linked with breast cancer,' he said.
For breast cancer in younger, pre-menopausal women, no pattern has emerged.
Dr Swerdlow said they had been surprised by half a dozen areas in which they had found higher than average numbers of cases of different cancers. 'In these areas it does seem to point to the need for more investigation as to what might be going on and for preventive programmes to be set up in the places which are doing worst.'
Strikingly high levels of lip cancer in men can be seen in East Anglia. One hypothesis was the possible popularity of pipe-smoking, a traditional influence from the Netherlands.
Parts of Somerset and Lincolnshire have more cases of cancer of the scrotum, areas not obviously associated with industrial disease, a known cause for this type of cancer. Devon, Durham and Hampshire rank high in the order for male cancer of the pleura, the membrane that lines the outside of the lungs. This cancer has long been associated with asbestos in the shipbuilding industry. A high incidence has also been found in Buckinghamshire, for which there is no clear explanation.
Buckinghamshire is known as a traditional risk area for cancer of nose, ear and sinuses in men, associated with cabinet making. But high levels have now been found in Derbyshire. 'We don't know why. This is another area where it would be worthwhile to go and find out,' Dr Isabel dos Santos Silva, the other author, said.
Dr McVie said that environmental factors which take in smoking, diet, viruses, pollution and radiation probably account for 70 per cent of cancers, while pure genetic factors may only, in the end, account for 10 per cent.
More predictably women in south-west England have more of the skin cancer, melanoma - between 50 and 80 per cent above the rest of the country. Brecon, in Wales, has the lowest numer of female cases.
In addition, the atlas reproduces data from the early part of the century. The cancer- death maps of the epidemiologist, Dr Percy Stocks, show concentrations of lung cancer in men in London and the South-east between 1921 and 1930, but little in the North.
The new maps show a reversal, illustrating the way in which men in the South have stopped smoking sooner than men in the North. Lung cancer in women in the London area is still high, showing how women started smoking 20 years later than men. In women under the age of 44, highest rates are in the northern counties.
Lung cancer in women under 45 was 67 per cent below the rest of the country in Somerset and 74 per cent above the rest of the country in Northumberland. Lung cancer in men under 45 was 63 per cent above average in Lancashire and 47 per cent below the rest of the country in Oxfordshire.
There has been little change in the pattern of stomach cancer since the Twenties. Incidence is still high in Wales, and low on the south coast.
The maps revealed no geographical trends in the incidence of leukaemia associated with the nuclear industry. However, the researchers said their maps were not sufficiently sensitive to detect very small local clusters of cancers.
Dr Swerdlow and Dr Silva, of the Epidemiology Unit at the London School of Hygiene and Tropical Medicine, supported by the Cancer Research Campaign, analysed 3,181,000 cancers in men and women from regional data over 18 years between 1968 and 1985.
Atlas of Cancer Incidence in England and Wales, 1968-1985; Anthony Swerdlow and Isabel dos Santos Silva; Oxford University Press; pounds 170.
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