Is there an exclusion exempting from federal taxation the first $X,000.00 paid to U.S. federal contract workers for overseas relief work?

You may be referring to the exemption from taxable income of up to $120,000 in 2023 for income earned while working in a foreign country. In general, to qualify you must be a citizen or resident of the foreign country you are working in or be physically present there for 330 days out of a consecutive 12 month period of time. You can learn more here:  Foreign earned income exclusion