Uncovering Global-Scale Risks From the Atmospheric Oxidation of Particle Bound Commercial Chemicals in Air

JOHN LIGGIO, Qifan Liu, Li Li, Tom Harner, Xianming Zhang, Amandeep Saini, Hayley Hung, Wenlong Li, Chunyan Hao, Patrick Lee, Jeremy Wentzell, Shao-Meng Li, Environment and Climate Change Canada

     Abstract Number: 72
     Working Group: Aerosol Sources and Constituents of Emerging Importance and Their Impacts across Spatial Scales

Abstract
Humans and ecosystems are exposed to tens of thousands of airborne chemicals, many of which are present in the particle-phase. However, only a miniscule fraction of these chemicals have been identified, as identifying harmful airborne chemicals, is largely based upon knowledge of parent chemicals in production. However, during their residence time in the atmosphere, emitted parent chemicals of concern are gradually transformed to thousands of products via photooxidation, such that tracking the complex mixture of products is an immense analytical challenge. While several studies have attempted to search through unidentified pollutants utilizing a non-targeted analysis technique (without targeting individual compounds), neither a traditional targeted, nor a non-target analysis approach in isolation are able to differentiate oxidation products from precursors, or determine their parent molecules of origin. Hence, the true environmental impact of a given parent chemical over the full atmospheric lifetime may be underestimated.

In the current work, a series of nine organophosphate flame-retardants (OPFRs) are investigated (as a relevant chemical of emerging concern), in laboratory studies to identify a large number of heterogeneous oxidation products (>190 species). We find that the transformation products identified in laboratory experiments are globally distributed across 18 megacities, representing a previously unrecognized exposure risk for the world’s urban populations. Finally, the full suite of OPFR product structures are used within in-silico models to estimate the persistence, bioaccumulation and toxicity of the products, demonstrating that transformation products can be up to an order of magnitude more persistent, and more toxic than the parent chemicals, such that the overall risks associated with the mixture of transformation products are also higher than the parent flame retardants. Together, this work highlights a strong need to consider atmospheric transformations when assessing the risks of commercial chemicals moving forward, to influence the development of future chemicals management.