"First ever" has been used very leniently here. Maybe it's the first ever for any state in America but the rest of the world definitely already has limits on it.
The EU limits are 500 ng/L for the sum of all PFAS in drinking water. Canada has an "objective" of 30 ng/L but I don't know how well it's enforced. The US proposal is for 4 ng/L for each PFAS but I'm not sure how they calculate the combined amounts. If it's simple addition, then it's 38 ng/L according to the article.
Can be read as "U.S. imposes its first-ever national drinking water limits" or "U.S. imposes world's first-ever national drinking water limits". There's a missing word and it's not clear from context what it's meant to be.
Using emphasis doesn't help bring clarity since the problem is the headline has multiple valid interpretations regardless if said words are emphasized or not. Adding something like "imposes its" helps highlight the intended interpretation.
The EU limits are 500 ng/L for the sum of all PFAS in drinking water. Canada has an "objective" of 30 ng/L but I don't know how well it's enforced. The US proposal is for 4 ng/L for each PFAS but I'm not sure how they calculate the combined amounts. If it's simple addition, then it's 38 ng/L according to the article.