Masked and Modified Mycotoxins in Indoor Environments: Analytical Implications, Transformation Pathways, and Domain-Aligned Interpretation

Masked and modified mycotoxins represent structurally altered forms of parent fungal secondary metabolites that arise through biological metabolism, environmental transformation, or chemical remediation processes. In indoor environments, these transformation pathways may alter detectability, analytical specificity, and toxicological interpretation without eliminating exposure relevance. This paper synthesizes current understanding of masked and modified mycotoxins within built environments and examines their implications for indoor environmental assessment. Mechanistic pathways of modification are reviewed, including fungal conjugation, environmental degradation, and oxidative or chlorination-mediated remediation chemistry. Analytical detection challenges, including ELISA cross-reactivity and compound-specific LC-MS considerations, are evaluated in the context of exposure-aligned domain interpretation. The framework integrates masked and modified forms into the Exposure-Aligned Analytical Domain Framework (EADF-IM), clarifying evidentiary requirements for claims of mycotoxin transformation, destruction, or detoxification in indoor remediation contexts. Recognition of masked and modified mycotoxins is essential for accurate interpretation of environmental measurements and for avoiding false conclusions of toxin elimination based solely on parent compound reduction.