Tosefta su Hagigah 3:9

Said Rabbi Yosei, from where [is it derived that] the consecrated food [of sacrifices] is rendered disqualified through fourth-degree impurity (see Chag. 3:2)? It is a logical deduction: If one who lacks atonement is not disqualified from [partaking of] Terumah [but is disqualified from consecrated food which carries] fourth-degree impurity, [then with respect to] one who is disqualified as to Terumah [which carries only third-level Terumah], is it not logical that he would [also] be disqualified from consecrated foods? We have learned third-degree impurity from what is written [in the Torah], and fourth-degree impurity from a kal v'chomer (a fortiori reasoning).