Thyroid cancer following scalp irradiation.

A sixfole increase in the risk of thyroid cancer was observed among 10,902 persons irradiated for scalp tinea in childhood as compared to two matched control groups. The dosimetry studies demonstrated that the original mean dose given to the thyroid was less than 9 rads, yielding a risk of 6.3/10(6)/year. This carcinogenic effect of low-level radiation must be considered in the planning of safety measures against potential public health hazards.