Chlorinated Paraffins in Global Air: First Results from the GAPS and GAPS-Megacities Networks

This study presents the first global data set of measured chlorinated paraffins (CPs), including short-chain (SCCPs), medium-chain (MCCPs), and long-chain chlorinated paraffins (LCCPs) in ambient air, derived from a single coordinated sampling network, i.e., the Global Atmospheric Passive Sampling (GAPS) network, using a passive sampling approach. Concentrations exhibited pronounced regional disparities, with the combined levels in two megacities─Lagos, Nigeria (512,000 pg/m³) and Beijing, China (258,000 pg/m³) exceeding by more than 1.5-fold the combined total levels observed across the rest of the world (∼459,000 pg/m³). Evidence of long-range atmospheric transport was observed at remote sites in western Canada (Little Fox Lake and Whistler), influenced by trans-Pacific air trajectories during the sampling period. These findings underscore the substantial global heterogeneity in the spatial distribution of CPs and the heavily disproportionate contributions of a few regions. Notably, the major producers/emitters, such as China, had several years of delay in ratifying the SCCP listing under the Stockholm Convention (Annex A, elimination since 2017 for congeners with > 48% chlorine content), and some countries have yet to ratify. Without the timely implementation of regulatory measures in these jurisdictions, global concentrations are expected to remain stagnant or even increase if emissions persist at current levels. These results further suggest that substantial time lags are likely before measurable declines in SCCP concentrations, and potentially in recently listed MCCPs, are observed even in regions where control measures are already in place. Hence, this global data set serves as a baseline for future assessments of temporal and spatial trends.