Monday, January 17, 2005

Something in the air?

'Child cancer "link to pollution"', says BBC News today, reporting new research that suggests that women exposed to air pollution during pregnancy are more likely to have children that develop cancer in childhood. Professor George Knox of Birmingham University compared data on child cancer deaths between 1966 and 1980 with pollution records from 2001, and found that women living within one kilometre of a pollution source were between two and four times more likely to have children with cancer.

The immediate problem with this study is that the cancer data is at least 20 years older than the pollution data. Many older pollution sources will have disappeared or been diminished, as a result of changing regulations and the decline of UK manufacturing.

But even if the two sets of data referred to the same time period, this would still not provide an accurate measure of the exposure of women to these pollutants. Even when a pollution source is close by, the place someone lives does not necessarily best reflect their exposure. Surely some account would need to be taken of where they worked, too? Different weather conditions and housing might also have an effect.

In any event, international comparisons of childhood cancers suggest that environmental hazards are unlikely to be to blame. Dr Anthony Michalski from the Institute of Child Health told the BBC: 'The rates of most paediatric tumours are relatively similar in industrialised and non-industrialised countries and that would not be expected if this hypothesis was correct.'

Even Knox accepts that this research should not be of much concern to the general public. 'The risk of a random child having a cancer is about one in 1000. In the hotspots it is two to four in 1000 so it's still a low risk.' Yet, on the basis of this study, he believes that there should be a substantial shift in research into the causes of childhood cancer. The real problem is the publicity given to studies such as this, which tell us little about the true causes of childhood cancer, and can only serve to alarm parents.

Child cancer 'link to pollution', BBC News, 17 January 2005