Here's the "obviously, everyone knows that" response, but for posterity:
In my experience, it really depends upon which specific sub-field you're interested in. For ambient air pollution, it's Harvard, hands down. For climate and air pollution, it's Berkeley. For climate and allergens, it's Columbia. For water, probably JHSPH. This way of thinknig is especially relevant for doctoral studies.
Butttt, generally for MPH studies
The generally best 5 (well, 8... this is hard) overall EHS programs in my experience are, in alphabetical order:
Berkeley
Columbia
Harvard
JHSPH
Michigan
UCLA
UNC
UW
Don't get me wrong, Yale has a phenomenal Environmental Health scene, but it's primarily because of the awesome Epi offerings at YSPH and the everything-else-environment offered at Yale Forestry. You can take advantage of that combo if you really want it... but I wouldn't say the combo epitomizes the YSPH or the Enviro Health experience...so Yale, in my opinion, is a borderline top EHS MPH school.