In 2010 Henry Miller and James Enstrom seriously wrote a piece in Forbes Magazine where they completely deny all scientific evidence of adverse health effects ultrafine diesel soot is causing.
So what's the deal: It must be the affiliation with the Hoover Institution, like many so called conservative and libertarian think tanks they just ignore scientific evidence. It's not just the cooked up Tea-Baggers who lack understanding, but quite often we see high profile people who just seem to live in a bubble.
Henry Miller, a physician and molecular biologist, is a fellow at Stanford University's Hoover Institution. James Enstrom is an epidemiologist and physicist at the UCLA Jonsson Comprehensive Cancer Center.
PS. As indicated in the comment below, Engstrom has taken money from Philip Morris in the past, which somehow underlines his credentials...