Not so pristine: airborne benzothiazoles and organophosphate flame retardants in an alpine site under anthropogenic stress

Although mountainous areas are often regarded as pristine environments due to their remote locations, anthropogenic pollutants can still reach through local emissions or regional atmospheric circulation. This study provides the first assessment of background concentrations of benzothiazoles (BTHs) and organophosphate flame retardants (OPFRs) in PM10 at a high-altitude site in the Eastern Italian Alps. Chlorinated OPFRs, particularly TCEP and TCPP, were dominant with concentration levels in the order of ng m−3, comparable to those detected in urban environments and reflecting their increasing application as substitutes for brominated flame retardants. BTH-SO3H was the most abundant benzothiazole derivative, indicating resuspension of particles originating from tyre wear as a major source. Both classes of target compounds exhibited temporal variations driven by thermally induced upslope winds and mixed-layer dynamics. Multivariate statistical analysis revealed a clear separation of BTHs and OPFRs from biogenic and crustal aerosol constituents, confirming a predominantly anthropogenic origin and highlighting their potential as tracers of human impact in mountain environments.