The Heart / Lung Arrangement

Areas of the Lung Susceptible

to Radon Induced Lung Cancer

pulmonary / gas exchange region -

secondary cancer risk

mouth & nasal

passages -

negligible risk

stem cells of

bronchial

lining - primary

cancer risk

The Major Bronchi and the Trachea

The stem cells of the bronchial lining, or epithelium, are a common site of primary malignant disease or lung cancer. The pulmonary / gas exchange region consisting of the smaller bronchi and bronchioles is a secondary cancer risk.

The Smaller Bronchi and Bronchioles

Not all of the lung is effective in the respiration process. There are some spaces which are effectively dead air. It is these areas which can be the site of dust disposition in particular occupations. In a radon environment, the dust may include radioactive particles.

The Alveolar Ducts and Alveoli

Because the barrier between the interior surface and capillary network is so thin, direct irradiation of the blood may occur from alpha emissions of airborne radioactive particles carried into this region.

Because they are exposed to the environment, have a large capillary network through which the entire output of the heart has to flow every minute and may suffer from sensitivity or allergy, the lungs can be host to a range of disorders. They can be affected by dust and fumes, and any allergy they may develop can have serious effects on the body’s operation. Also there are a mass of tiny blood vessels present, and any diseases that might affect these will affect the lung’s ability to function. The lung is a sensitive but vital organ.

It takes hundreds of thousands of years to produce radon from the radioactive decay of uranium 238. To complete the process to lead 206 takes around 23 years and for five of these steps only a few days.

The principle health hazard from radon results from breathing radon 222 contaminated air. The radioactive daughter particles may become entrapped in the lungs and because of their very short half lives may decay into other radioactive particles before being expelled.

It is the ionising radiation given off as the particles change that can damage the lung tissue. The radiation may not kill cells directly but only damage or alter them. If the DNA is altered, the cell may still be able to replicate but in a mutated form which may be cancerous. The number of cells altered increases with the amount of radon and the time exposed.

The nature of irradiation is such that the development of cancers in susceptible people may not become apparent for several years. In studies of uranium miners, the time taken to develop a cancer was between 10 and 20 years. When the cancer was diagnosed however, death was usually in about 8 months.