Dissatisfaction is a common thing among the young and the ambitious.
Like most things, the profession of Environmental Health has both breath and depth. Also please keep it in mind that health issues are not restricted to communicable diseases or diseases caused by biological agents. Health issues can have chemical origins. I assume that you have adequate training in all four environmental compartments, breadth wise, but how about the depth of your knowledge. EHOs in the health authority I am working for have been specialized for many years.