Air Toxicity Surveillance across Thirteen Cities Using Rats

Current monitoring methods fail to assess air toxicity in real time, which is yet badly desired to better estimate the health impact. Here, we developed and deployed an automated, low-cost, and time-resolved system for noninvasive monitoring of air toxicity by detecting eight breath-borne biomarkers from rats, including VOCs, CO₂, CO, NO, H₂S, H₂O₂, O₂, and NH₃. Using this system, two large-scale monitoring campaigns were conducted across 13 cities in China during the 2023 winter and 2024 spring continuously on a 24-h-a-day basis. In characterizing overall air pollution health impact, a novel Air Toxic Index (ATI) was developed using the eight breath-borne biomarkers from the rats. Significant differences in diurnal patterns of ATI were observed across 13 cities. Among others, time, city, PM_2.5, and O₃ were identified as the primary influencing factors of ATI, exhibiting complex nonlinear relationships in real-world environments. The unique variation patterns of breath-borne NO and H₂O₂ from rats indicated the time-resolved impacts of ground human activities on weekends and PM components on air toxicity. Histopathologic changes in these deployed rats' lungs further validated the differential health effects of real-world air pollution from different cities as detected by the rat system. Here, we pioneer a new air pollution health effect monitoring system that realizes the in vivo detection of air toxicity in contrast to the traditional protocol of air sampling, exposure, and offline toxicity analysis steps. The system can be deployed easily to any location with minimal support for real-time monitoring of air pollution health impacts.