It’s a heritage of hate.

The biggest issue with the EPA setting limits is finding labs that can measure to those levels with any sort of accuracy or precision. In the article they mention California’s limits are 5 parts per trillion. That’s 10^-12 or 0.000000000005. It’s really hard to find equipment that can measure that low with out some dilution factors. This makes it hard to set standards. If you can’t measure it, you can’t regulate it.