Looking on the Public Health Service website, in order to be an environmental health professional they require (among several options) that you have "A master's degree or doctoral degree with a specialization in environmental health, occupational health, or industrial hygiene from a school of public health accredited by the Council on Education for Public Health (CEPH)." However, "To be a public health officer you must possess a master's degree from a program accredited by the Council on Education for Public Health (CEPH). "
I'm not sure if the specification of school v program is intentional or not, so attending a school v program may very well make a difference when applying for federal employment.