There is a graph that's rate of change, as opposed to rate of occurrence.
Rate of change was already climbing through the 80's along with the other age groups, then dipped in the early 90's for about 10 years and then started climbing again for the age range 15-39 while the older age ranges decreased.
That would lead me to believe any environmental cause has been around for a while and it's likely that all the focus has been on screening 40+ and not enough screening for those under 40.
"Cancer is hitting more young people in the U.S. and around the globe, baffling doctors. Diagnosis rates in the U.S. rose in 2019 to 107.8 cases per 100,000 people under 50, up 12.8% from 95.6 in 2000, federal data show."
Rate of change was already climbing through the 80's along with the other age groups, then dipped in the early 90's for about 10 years and then started climbing again for the age range 15-39 while the older age ranges decreased.
That would lead me to believe any environmental cause has been around for a while and it's likely that all the focus has been on screening 40+ and not enough screening for those under 40.