A fantastic thought here!
Environment can both lead to well-being as well as illnesses, and this is exactly what we are trying to capture in the context of environmental health. For instance, what aspects of our environment lead to a better sense of well-being? Which aspects of our environment (built environment, social environment, others) lead to illnesses? In the sense you bring up the role of environment, we can discuss almost any environmental exposure will have the effect of contributing to well-being and illnesses simultaneously. For instance, trekking in high altitudes fosters mental, social (with other trekkers) and to some extent physical well-being, yet, the lack of oxygen can lead to serious illnesses.