These programs require a great depth of knowledge. These spedcializations are all sub-programs of Environmental Health. It is my humble opinion that there are all kinds of opportunities in Environmental Health and as an EHO, but you must pick a progressive employer to work for. I have qualified as an EHO in the UK in 1997. At the begining I was enthusiastic about a varied work.
Dissatisfaction is a common thing among the young and the ambitious.
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. EHOs in the health authority I am working for have been specialized for many years. Specialized areas include air quality, contaminated sites assessment and human health risk assessment. These programs require a great depth of knowledge.