Comment by selcuka
I knew two people (one adult, one child) who lived in the same building and got diagnosed with leukemia (~14 per 100,000) shortly after each other, maybe within a few weeks.
It's anecdotal, of course, but I've always thought that there could have been a connection.
It could be birthday paradox, but it could potentially be enough to get someone to come check for contaminants.
Looks like benzene, some pesticides, and formaldehyde are the common workplace exposures that can trigger leukemia. But some of those can turn up near housing.