A.L. Bell wrote:
....
Personally, I live in an urban neighborhood a couple miles from some
major interstate highways.

Does anyone know whether the amount of "bad" mercury I'd get from
eating tuna is actually significant compared with the mouth I get from
breathing city air?y

I would worry more about lead. For many decades lead was a routine
additive to gasoline. As a result, all major highways and most other
roads have significantly high (even toxic) levels of lead spread
all around them. Take some soil samples around your property and
test them for lead.

Anthony