A clear trend with deprivation was evident: the average radon concentration for the most deprived controls being 16.1 Bq m −3 , compared with the least deprived of 27.2 Bq m −3 .
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The United Kingdom Childhood Cancer Study of exposure to domestic sources of ionising radiation: 1: radon gas.
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The sentences
Both sets of radon levels show a negative trend but those with the pre-defined levels are less marked.
These variations are unlikely to explain a positive trend, let alone the negative trend seen in this paper.