R.J.
Environmentally friendly doesn't always (or even often) translate to human friendly. Take fertilizers. Natural fertilizers are chock full of pathogenic bacteria and parsites. Chemical fertilizers aren't as good for the environment... but also don't contain deadly microbes. In fact, many of the reasons that environmentally harmful things were created in the first place was to figure out a way to keep people safe/ healthy.
Absolutely contact your OB... just tell them that you've been exposed to mercury and don't know how much and is there a way for them to test or remediate?