<p>This paper investigates the problem of semantic pollution for modal proof-systems. The author proposes that, when proof-systems are used to build antirealist theories of meaning, the real problems lurking behind semantic pollution are: inferential semantic contamination and realist pollution. The first notion deals with misbehavior of meaning as inferentially conceived, and is grounded on the idea of dependence of meaning between logical terms. The second notion deals with pollution with realist theories of meaning. The paper has two main sections. In the first section it is shown that both traditional proof-systems and labeled proof-systems for modal logics are problematic because of inferential semantic contamination. In the second section it is argued that, even if labeled systems were harmonious and semantically non-contaminated, they could still be polluted with realist meaning.</p>