When 'vape-free' should mean 'smoke-free': third-hand e-cigarette residues and the developing lung.

E-cigarettes are widely perceived as a safer alternative to tobacco, and that perception often extends to their use around infants and children. Yet exhaled aerosol deposits onto indoor surfaces, leaving a residue, known as third-hand e-cigarette aerosol, that can be re-emitted, ingested, or absorbed through the skin. The developmental consequences of such exposure have been almost entirely unexplored. In this issue of Pediatric Research, Zaman et al. begin to address that gap, exposing neonatal mice to third-hand e-cigarette aerosol-contaminated terrycloth and carpet in early-life. The authors report sex-divergent outcomes: transient neutrophilic inflammation in females, and broader transcriptional disturbance, delayed alveolar maturation, gut microbiome shifts, and persistent adult obstructive lung dysfunction in males, with tobacco flavouring amplifying the male response. This commentary considers the study's strengths, outlines future research priorities, and argues that the findings strengthen the case for extending 'smoke-free' protections to vaping.