Rising population The main reason for pressure on housing in Edinburgh and the Lothians has been the rapidly rising population, driven by large-scale immigration, which has been actively encouraged by politicians and business leaders in their desperate search for cheap labour.

Immigration and population control are green issues and our environment and wildlife will pay the price for this failure to control human numbers. The choice is stark: we cannot have a good environment and a rapidly rising population.

We shall have to choose whether we value quality of life and a healthy environment or continue to follow the south-east of England in covering our land in roads, houses and urban sprawl. Scotland must adopt a population policy which places sustainability at its heart, and to do this we must stabilise the numbers of people, and then implement a managed reduction in population which will free up more houses, while safeguarding our natural heritage.

Awaab Raja, 108 Easter Road, Edinburgh. No radiation link to childhood leukaemia It was good to see the letter from Yvonne White which challenged the assertions in the article of July 19 about childhood leukaemia being in some way due to radiation from nuclear sites. May I add two further points?

First, the radiation dose which can be attributed to nuclear sites (0.3 microsieverts as correctly stated in her letter) represents just 1% of the dose which everyone in this country receives from natural background radiation.

Secondly, the accepted view of those who have studied the possible contribution of radiation to cases of leukaemia is that the minimum dose to cause leukaemia is at least one sievert. And this dose must be received in a short time - not over a period of years.

So, whatever is the cause of childhood leukaemia, it is not radiation and most certainly not radiation from nuclear sites.

If requested, I can easily supply references from the scientific literature for the points I have made.

Ian Crawford, 10 Gailes Park, Bothwell, Glasgow. Case in point Crossing London last week, I (an elderly white male) was accosted three times down in the Tube stations by young persons of non-white appearance. On each occasion I gratefully accepted their offer to carry my heavy suitcase up the stairs.

John Rankin, 12 Hamilton Place, Perth.