Health: Cancer threats all around us: Celia Hall looks at two reports highlighting the risks of sunlight and other carcinogens

WITH SO much emphasis placed on the difficulties of finding effective treatments for cancer, it is disquieting to learn that the incidence of cancer overall seems to be increasing, according to two reports published last week.

This makes preventing cancers even more imperative. One study, from Sweden, published in the current edition of the Lancet, says that cancer- causing agents in the environment, whether natural or man- made, must play a significant part in this worrying increase.

In the light of this study, avoiding sunburn seems a small act of self-preservation in the face of evidence of an increase in melanoma, the skin cancer of the affluent in the Western world. Yet, just as with smoking, the message is taking a long time to sink in. Meanwhile, the latest report from the Office of Population Censuses and Surveys, (Cancer Statistics: registrations of cancer diagnosed in 1987, (HMSO, pounds 16.40)), shows that malignant melanoma has shown an overall increase of 50 per cent over the period from 1979 to 1987.

'It is almost certain that recreational exposure to sunlight is important,' the report says. 'There is a strong social class gradient in risk, with higher rates among professional and non-manual workers.' In other words, those who can afford to take sunshine holidays in faraway places are putting themselves at risk.

More prevalent among fair-skinned northern European types who live in hot countries, malignant melanoma is one of the few cancers, excluding those of the reproductive organs, that is more common in women than men. The 1987 OPCS statistics for England and Wales show there were 2,006 female melanoma registrations, compared with 1,133 for men.

It is unusual in another respect, with a sizeable proportion of cases occurring among young people. 'Melanoma is extremely rare in childhood, but nearly 20 per cent of cases occurred in young adults (20-39 years),' the report states. In other forms of cancer, taken as a whole, only 4 per cent will occur in this age group, most being diagnosed later in life. However, the OPCS report says increases in melanoma risk have affected both sexes and people in all age groups.

In England and Wales, overall cancer registrations followed a pattern of small but steady increases of about 0.5 per cent a year. Three sites in the body, for both men and women, continued to account for half of all cancers registered. In men these are lung, bowel and prostate; in women, breast, bowel and lung.

Lung cancer decreased in men by about 15 per cent, during 1979-1987 - reflecting the greater numbers of men who stopped smoking - but increased in women by more than 20 per cent.

The Swedish study says that even the sharp rise in smoking-related cancers this century cannot account for the upward trend the researchers found.

The survey is based on the very reliable data from Sweden's Cancer Registry set up in 1958. It has found an increase in cancer rates of between a half and a third in all age groups, among both sexes, in a study of nearly 850,000 cases registered for all of Sweden between 1958 and 1987.

Even though smoking related cancers (lung and throat) increased greatly, they only account for part of the increase which, says the study, is particularly worrying in the groups of people born most recently.

The Swedish researchers say that the most likely reasons for the increase are environmental factors - cancer-causing agents, some perhaps yet to be identified. 'Our data strongly suggest increased population exposure to carcinogens,' they add.