2 CFR 1532.995 - Principal (EPA supplement to government-wide definition at 2 CFR 180.995).
In addition to those listed in 2 CFR 180.995, other examples of individuals who are principals in EPA covered transactions include:
(a) Principal investigators;
(b) Technical or management consultants;
(c) Individuals performing chemical or scientific analysis or oversight;
(d) Professional service providers such as doctors, lawyers, accountants, engineers, etc.;
(e) Individuals responsible for the inspection, sale, removal, transportation, storage or disposal of solid or hazardous waste or materials;
(f) Individuals whose duties require special licenses;
(g) Individuals that certify, authenticate or authorize billings; and
(h) Individuals that serve in positions of public trust.