“…For example, the latter (i.e., similar other risks) chanced raising perceptions of radon risk by a riskladder effect (Sandman, Weinstein, and, Miller, 1994) in which people interpret vertical position on a graph as relative risk. People consistently underestimate interaction versus separate risks of the two hazards (e.g., Hampson et al, 1998Hampson et al, , 2000Lee et al, 1999;Lichtenstein et al, 2000; for a more positive view, see Dawson, Johnson, and Luke, 2013), although one person asked for information about synergistic risk. Comparing 20 chest x-rays a year to the similar risk of the regular standard for radon in water elicited an expected comment (from just one participant) that it should be dropped because no one gets 20 x-rays a year.…”