Yes, 2,4-D is heavily researched. More is known about 2,4-D and how it works than almost any other crop protection tool.
The toxicology database alone exceeds 4,000 peer-reviewed, published studies, plus hundreds of scientific studies that manufacturers of 2,4-D must provide to regulatory agencies throughout the world so registrations of products containing 2,4-D are kept current. There are now more than 160 peer-reviewed, published epidemiologic (human) studies pertinent to 2,4-D. The industry research Task Force has taken the additional steps of publishing the research data submitted to regulators in peer-reviewed journals.