Corporations, especially the huge, sort-of-evil ones
Corporations are constantly complaining about government regulation, and with good reason. Regulation forces them to behave in a manner that is not always conducive to growing the bottom line. Government agencies like the FDA and the EPA insist that companies make industrial and consumer products that are mostly nontoxic and don’t murder everyone, a requirement that makes the manufacture of things like nerve gas and explosives costly and difficult.
One of the ways in which corporations can head off government regulations is to conduct human trials proving, more or less, that poisonous things aren’t that poisonous. The EPA and the FDA receive studies every year from chemical companies, weapons manufacturers, the oil and tobacco industries, and others, all showing that their products aren’t really hideously deadly and that it’s the dead person’s fault he got so exposed to dioxins or radiation or toxic smoke.
Industry watches us very closely, hoping to arrive at alternative conclusions to those reached by real scientists. When you make billions of dollars a year pooping toxic smoke into the air, spending a few thousand dollars conning volunteers into eating poison is a pretty tiny slice off the bottom line.