These are all the relevant papers I found on passive vaping in the first four pages of research paper search. I got access to like ten sites for research and there used to be a grey area site for accessing and downloading research papers (sort of like torrenting) but that site was taken down two or three years ago.
Most studies say that the health effects of passive vaping are insignificant and significant health problems are mostly found with unregulated throwaway THC vapes. Active vaping is another story and vaping PG at overvoltage with sub-ohm coils can produce formaldehyde and some other toxins. However overvolting a rig will also burn your mouth which is why the instance of producing said toxins is uncommon. More likely is that for active vapers the inhaling resistance of PG vapor may have some pulmonary irritations compared to water or glycerine vapor.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4565991/
https://pubs.acs.org/doi/abs/10.1021/acs.est.7b00710
https://scholar.google.de/scholar?start=20&q=passive+vaping+effects&hl=de&as_sdt=0%2C5#d=gs_qabs&t=1750859598694&u=%23p%3DpzVN5DufXgsJ <- This one recommends replacing PG with distilled water and VG to reduce throat irritation in active vapers.
https://link.springer.com/rwe/10.1007/978-981-16-7680-2_7
These are all the relevant papers I found on passive vaping in the first four pages of research paper search. I got access to like ten sites for research and there used to be a grey area site for accessing and downloading research papers (sort of like torrenting) but that site was taken down two or three years ago.
Most studies say that the health effects of passive vaping are insignificant and significant health problems are mostly found with unregulated throwaway THC vapes. Active vaping is another story and vaping PG at overvoltage with sub-ohm coils can produce formaldehyde and some other toxins. However overvolting a rig will also burn your mouth which is why the instance of producing said toxins is uncommon. More likely is that for active vapers the inhaling resistance of PG vapor may have some pulmonary irritations compared to water or glycerine vapor.