Where do they come from, where do they go? Emissions and fate of OPEs in global megacities

Abstract Cities are drivers of the global economy, containing products and industries that emit many chemicals. We used the Multimedia Urban Model (MUM) to estimate atmospheric emissions and fate of organophosphate esters (OPEs) from 19 global “mega or major cities,” finding that they collectively emitted ~ 81,000 kg yr− 1 of ∑10OPEs in 2018. Typically, polar "mobile" compounds tend to partition to and be advected by water, while non-polar "bioaccumulative" chemicals do not. Depending on the built environment and climate of the city considered, the same compound behaved like either a "mobile" or a "bioaccumulative" chemical. Cities with large impervious surface areas, such as Kolkata, mobilized even “bioaccumulative” contaminants to aquatic ecosystems. By contrast, cities with large areas of vegetation fixed and transformed contaminants, reducing loadings to aquatic ecosystems. Our results therefore suggest that urban design choices could support policies aimed at reducing sources of emissions to reduce chemical releases to the broader environment without increasing exposure for urban residents.