Impact of chemical exposures on human infectious diseases: a scoping review to identify gaps and priorities

Strengthening public health preparedness against emerging and existing threats requires integrating chemical and infectious disease research, consistent with One Health principles. This scoping review systematically maps epidemiological evidence linking chemical exposures to human infectious disease susceptibility or severity. We searched Web of Science and PubMed (1980-August 2023), ultimately synthesizing data from 94 primary analytical studies. Studies are heavily concentrated on metals (Arsenic, Cadmium, Lead) and PFAS (PFOA, PFOS), primarily in relation to respiratory infections across infants and children. The overall evidence trend suggests an increased risk associated with chemical exposure, although the body of evidence is fragmented across many specific chemical-outcome pairings. Key knowledge gaps include under-investigation of adolescents and the elderly, and a lack of consistent mechanistic understanding linking exposure to outcome. The high heterogeneity in study reporting underscores a need for standardized epidemiological methods. This review synthesizes current knowledge of chemical-outcome pairs, identifies gaps to guide research priorities, and discusses perspectives to leverage mechanistic-based frameworks to better inform effective regulatory actions against environmental immunotoxicants, especially for vulnerable populations.