I've heard this claim a few times before (always from people trying to handcuff the EPA rulemaking process, funny enough) and I haven't looked into the specific

I've heard this claim a few times before (always from people trying to handcuff the EPA rulemaking process, funny enough) and I haven't looked into the specifics too closely, but my experience working with and around EPA on regional air quality issues has been that the regulations lag at least 10 to 20 years behind the science.