|Lung tumours in rats after inhalation of radon|
|Published: Open access to everyone|
|Dr. Michele Morin|
|BIOLOGICAL SAMPLE AVAILABLE|
|Purpose: To determine the risks of lung tumors after radon inhalation.
Status: 1968-1992, terminated; data in ERAD except for groups indicated in red
Treatment: Inhalation of radon (0.1-0.3 μm AMAD, 6.2% unattached)
Dosimetry: Activity inhaled (dose from daughter products deposited 2-3 mGy/WLM)
Endpoints: Life-span study (spontaneous death) with macroscopic/microscopic pathology unless otherwise stated below.
Animal: Male Sprague-Dawley SPF rats of different ages as indicated, controls see under 02.01
Results: The studies on dose-effect relationships of radon can be classified into 4 groups:
Very high doses and dose rates with doses varying from 2000 to 10,000 WLM at concentrations from 2500 to 5000 WL. At doses of more than 4000 WLM, rats do not live long enough to develop cancer and, at the very high concentrations, damage to lung is too severe to allow tumor development.
High doses at high dose rates. In a first study in 1972, the rat received doses from 800 to 4400 WLM at a dose rate of 2500 WL, resulting in a dose-dependent increase in lung cancer incidence from 23 to 67%. In a new study started in 1977, concentration was 1500 WL, and the dose of 3000 WLM was either given over 2 months (23% cancers) or 6 months (80% cancers). In 1985, different doses were delivered at a concentration of 1200 WL resulting in cancer incidences of 14% (200 WLM), 14% (500 WLM), 35% (1000 WLM), 40% (3000 WLM) and 16% (6000 WLM), ie again a reduction of cancer incidence at very high doses.
Low doses at average dose rates. From 1975, the experiments were carried out at dose levels comparable to those uranium miners are exposed. When 300 rats were exposed to 50 WLM radon at 150 WL (1975), 11 lung cancers were found; an exposure to 25 WLM at 150 WL (1978) caused 14 cancers in 500 rats. In 1980, two series of 500 rats received 25 and 50 WLM yielding respectively 11 and 19 lung cancers.
Low doses and low dose rates: In 1989, a study was started with a the very low concentration of 2 WL and a dose of 25 WLM. Only 3 lung cancers (0.6%) ,ie slightly less than in controls, were observed.
In conclusion, the three parameters most important for the causation of lung cancer from radon are: total dose, concentration in the atmosphere and the fractionation of the dose.
|Link to data and details in ERA|
|LINK TO FILE|