Radon and lung cancer in Finland:: Are there signs of radiation hormesis?

Prolonged exposure to any level of radon in indoor air is generally thought to be hazardous to human health and to give rise to lung cancer. On the other hand, low or moderate levels of radon in indoor air may, according to the radiation hormesis hypothesis, be beneficial to human health and even inhibit the growth of cancerous cells. An attempt is made here to test these contrasting views by comparing mortality rates from lung cancer during the 10-year period 1986-1995 with average indoor radon levels in the 435 communes (municipalities) of Finland (excluding Aland). The results show a very low, statistically non-significant correlation between radon and lung cancer mortality (r = -0.0331), which in turn implies that at least in this case neither the possible beneficial hormetic effect of radon nor its cancer-provoking hazardous effect can make itself apparent against the dominant and masking effect of cigarette smoking, the main cause of lung cancer.