Rethinking environmental boundaries for contaminants of emerging concern

The global proliferation of synthetic chemicals has led to the widespread and continuous release of Contaminants of Emerging Concern (CECs) into the environment. CECs include pharmaceuticals, pesticides, personal care products and other industrial chemicals that pose a significant risk to both ecosystems and human health. Regulatory frameworks have predominantly targeted aquatic systems; however, mounting evidence reveals the capacity of many CECs to volatilise, aerosolise and undergo atmospheric transport. This perspective highlights the overlooked atmospheric dimension of CECs and analyses the key physicochemical parameters governing their transfer to the atmospheric domain. The results indicate that many CECs can mobilise from water or soil and undergo atmospheric transport in both the gas- and particle-phase, crossing between several environmental continua as a result. While intrinsic properties such as vapour pressure and partitioning coefficients are central to this analysis, environmental factors such as temperature, humidity, solar radiation, and transformation reactions further modulate the environmental fate and impact of CECs. We emphasise the need for environmental monitoring and regulatory frameworks to incorporate air as a critical vector for CEC dispersion and exposure. Key research priorities identified measurements of CECs in the atmosphere, further development of predictive models, and toxicity evaluation of airborne CECs to better inform policy for protecting public and environmental health.