Sea salt is a combination of 70-80 different minerals and these include some "naturally occuring heavy metals". For the most part if the Sea Salt is from a reliable source with quality controlled areas then these heavy metal levels are negligible and should not be of concern. It's true that heavy metals for industries can get dumped into the sea and over time may accumulate in some areas - himalayan salt is considered to be by many the best salt that does not get exposed to many environmental conditions - you will notice though that this salt still contains naturally occurring "heavy metals" as well (again naturally occurring).
Mike