While　vehicle　cabin　environment　significantly　impacts　human　health,　systematic　studies　on　this　important　microenvironment　are　lacking.　Here,　we　conduct　a　12-day　field　observation　of　a　new　car　under　varying　environmental　conditions.　Concentrations　of　20　common　volatile　organic　compounds　are　determined.　Levels　of　formaldehyde　and　acetaldehyde　exceed　the　suggested　limit,　with　34.9%　and　60.5%　over　the　standard　rate,　respectively.　By　combining　an　improved　multi-source　model　with　quantitative　correlations　between　three　key　parameters　of　volatile　compound　emissions　from　various　in-cabin　materials　and　temperatures,　we　predict　formaldehyde　concentrations　at　different　temperatures,　which　are　consistent　with　measurements.　We　find　that　volatile　compound　emission　characteristics　are　dependent　on　material　surface　temperature　rather　than　the　widely　used　metric　of　air　temperature.　This　study　probes　volatile　compound　variability　in　a　realistic　vehicle　cabin　via　observation　and　modeling　and　estimates　in-cabin　incremental　lifetime　cancer　risk　via　three　exposure　routes,　indicating　a　high　health　risk　for　drivers.　©　2023　The　Author(s)