Changing majors as a senior?

I don’t think Environmental Engineering is what you want. Here is a program which sounds a lot more like what you are describing:

http://sphhp.buffalo.edu/epidemiology-and-environmental-health/education/environmental-health-mph/requirements-and-curriculum.html

Given that you still have another year, it seems like the pre-reqs are probably doable for you where you are now:

http://sphhp.buffalo.edu/epidemiology-and-environmental-health/education/environmental-health-mph/admissions.html