A staple of weird history sites, the Poison Squad were a self-selected group of healthy young men who willingly ingested food laced with untested food additives including formaldehyde and Borax. From their brave efforts come the foundations of the US FDA.
Stuff You Missed In History Class have an episode about them, usual provisos about excessive advertising applies.
Atlas Obscura have a very informative article with some good original pictures.
Science History have a general biography of Harvey Wiley.
….and here’s a short video for anyone who doesn’t have enough patience for those.