Mobiles don't cause cancer! This time
Big survey but still flaws
The biggest survey into a possible link between mobile phones and cancer has concluded that there isn't an increased risk of cancer from using mobiles. Media reports seem to be claiming that this has been the conclusion all along.
The survey by the Danish Cancer Society and published yesterday in the US Journal of the National Cancer Institute took a different and wider approach to most reports that have gone before. Rather than going for the suspect approach of sticking a mobile next to a sensor modelling a human head, the Danish crew used records of mobile phone subscriptions and tallied them with results from the national cancer register - a databank of Danish cancer sufferers of the past 50 years.
They found there was no causal link between the two and so have concluded that mobiles don't cause cancer. This is a widely accepted scientific approach and it is certainly far harder to fudge than single experiments, but is still rather flawed in giving us a true image of what mobiles may or may not be doing to our brains.
The fact is that if we assume mobiles can cause tumours, the process is not a fast one. It will take years and years for a tumour to develop in most cases. And since mobiles have only been widely used in the last two, three years, it is hardly surprisingly that the survey hasn't seen a disproportionate increase of cancer in mobile phone users. The report is happy to point this out.
Also, since the Institute was dealing with raw facts, it has very little knowledge of all the factors that may affect conclusions ie. how much the phone is used by an individual, whether they have a high incidence of cancer in their family, environmental factors etc etc.
The value of this report is not in its first publication. The great value of it will be if the same methodology is applied in subsequent years and then the results compared with previous reports. Then it should be possible to build a fairly strong case either way.
Here's the abstract from the report, by the way. The Journal of the National Cancer Institute has really gone overboard on the phone issue in this fortnightly issue - it has written an editorial and three news pieces on the matter as well as the main report. The journal is on the Net, but unfortunately you need a subscription to get access to the full text. Its Web site is here. ®
Cellular Telephones and Cancer: a Nationwide Cohort Study in Denmark
Use of cellular telephones is increasing exponentially and has become part of everyday life. Concerns about possible carcinogenic effects of radiofrequency signals have been raised, although they are based on limited scientific evidence.
A retrospective cohort study of cancer incidence was conducted in Denmark of all users of cellular telephones during the period from 1982 through 1995. Subscriber lists from the two Danish operating companies identified 420,095 cellular telephone users. Cancer incidence was determined by linkage with the Danish Cancer Registry. All statistical tests are two-sided.
Overall, 3391 cancers were observed with 3825 expected, yielding a significantly decreased standardized incidence ratio (SIR) of 0.89 (95% confidence interval [CI] = 0.86 to 0.92). A substantial proportion of this decreased risk was attributed to deficits of lung cancer and other smoking-related cancers. No excesses were observed for cancers of the brain or nervous system (SIR = 0.95; 95% CI = 0.81 to 1.12) or of the salivary gland (SIR = 0.72; 95% CI = 0.29 to 1.49) or for leukaemia (SIR = 0.97; 95% CI = 0.78 to 1.21), cancers of a priori interest. Risk for these cancers also did not vary by duration of cellular telephone use, time since first subscription, age at first subscription, or type of cellular telephone (analogue or digital). Analysis of brain and nervous system tumours showed no statistically significant SIRs for any subtype or anatomic location.
The results of this investigation, the first nation-wide cancer incidence study of cellular phone users, do not support the hypothesis of an association between use of these telephones and tumours of the brain or salivary gland, leukaemia, or other cancers.