 Complete the following phrase:  While the effects of high and acute doses of ionising radiation are easily observed and understood in humans e.g. Japanese atomic bomb survivors, the effects of low-level radiation are very difficult to observe and highly controversial. This is because the baseline cancer rate is already very high and the risk of developing cancer fluctuates 40 because of individual life style and environmental effects, obscuring the subtle effects of low-level radiation. An acute effective dose of 100 millisieverts may increase cancer risk by 0.8. However, children are particularly sensitive to radioactivity, with childhood leukemias and other cancers increasing even within natural and man-made background radiation levels under 4 mSv cumulative with 1 mSv being an average annual dose from terrestrial and cosmic radiation, excluding radon which primarily doses the lung. There is limited evidence that exposures around this dose level will cause negative subclinical health impacts to neural development. Students born in regions of higher 