Emergent properties

Biological research in the United States, since World War II, has been heavily funded by the federal government, mostly through the National Institutes of Health. The Centers for Disease Control and Prevention does fund some public health research, though it's more social science than biology, i.e. evaluating the effect of public health interventions. The Defense Department and VA also fund some biomedical research, as does the more recently established Patient Centered Outcomes Research Institute.  

Most of this is applied, as opposed to basic research. The NIH funds some basic research, and the National Science Foundation exclusively funds basic research. Basic research asks how organisms function, without immediately worrying about what use we might make of that information. Applied research is aimed directly at a useful outcome -- curing or preventing disease, alleviating symptoms. Going back down a level, it's worth noting that the basics of chemistry are now quite well understood, and most chemical research is applied -- creating useful new materials and manufacturing processes. That means industry funds a lot of it because it can lead to patentable products and profits.

In biomedicine, the pharmaceutical and medical device industries fund a lot of applied research, for the same reason. However, their products are much more stringently regulated than those of the chemical industry. Basically, you can sell chemicals until they're proven to be harmful, and even then whether restrictions on their use or outright bans don't necessarily happen right away, if ever. Industries usually try to suppress findings that their products are harmful, and lobby against regulation. 

That's why the entire U.S. population was exposed to the highly dangerous neurotoxin lead for generations, causing all sorts of behavioral problems and probably largely accounting for the crime wave of the late 20th Century. There are still all sorts of food additives and pesticides and emanations from plastic and God knows what else that's harming and killing us. The EPA was way behind on all this and now it's out of business entirely.

This is something of a digression but it's necessary context. I'll put all this context to use next time.