https://oehha.ca.gov/media/download...//p65122917.pdf

Mercury makes the proposition 65 list of possibly harmful chemicals, with "developmental" effects as the given reason, birth defects and reproductive harm could come under that heading. So maybe it's just about mercury, and it's just now made it to the label. Nothing new, excess mercury from higher tuna intake has been a risk for a long time.

This putting every possible chemical contaminant in one bucket and having a single warning that doesn't specify what the contaminant is in a particular product seems stupid.