Room-temperature release of short- and medium-chain chlorinated paraffins from typical polyvinyl chloride products

Chlorinated paraffins (CPs), among the most largely produced and used persistent organic pollutants (POPs), have drawn significant global attention. Emissions from consumer products are a major source of CPs in the atmosphere. However, limited data exist on their release at ambient temperature due to the challenge of measurement. In this study, we successfully quantified the room-temperature release rates and thoroughly investigated the release kinetics of short- and medium-chain CPs (SCCPs and MCCPs) from four representative polyvinyl chloride (PVC) products. Release rates of ∑SCCPs and ∑MCCPs were determined to be 0.0084-0.74 μg/(m²·min) and 0.003-0.17 μg/(m²·min), respectively. Using a developed congener-specific quantification method and mechanistic emission model, we further investigated the release kinetics of individual CP congeners. Early-stage releases are controlled by surface volatilization, particularly for more volatile CPs, but shifts to internal diffusion over the long-term. Release rate of SCCPs drop rapidly, with time to decrease by half within 0.48-2.2 years, whereas MCCPs exhibit a slow decline, raising about their long-term release from PVC products. The obtained release kinetics enable the derivation of time-variant emission factors, supporting the development of a more realistic CP emission inventory.