Formaldehyde emissions from light-duty gasoline vehicles: Emission characteristics and future trends

Formaldehyde (HCHO) is a carcinogenic pollutant that poses serious environmental and health risks. However, the emission characteristics of light-duty gasoline vehicles (LDGVs) and their future trends remain poorly understood. In this study, HCHO emissions from LDGVs were characterized under standard testing cycles using a portable emissions measurement system at a 1 Hz sampling resolution. Results show that HCHO emission factors (EFs) decrease with stricter emission standards, but their distribution across speed-acceleration bins remains consistent. HCHO exhibits distinct emission behavior compared with total VOCs, remaining relatively stable between start-up and running phases rather than peaking sharply during cold start. HCHO EFs are generally highest in low-speed bins across all vehicle groups, and higher-mileage vehicles emit more HCHO, with the impact more pronounced during running than at start-up. Emission projections indicate that Beijing's LDGV HCHO emissions will increase by 30 % from 2025 to 2035, with a 113 % rise during running and a 53 % decrease at start-up. These findings highlight the need for more precise and real-time emission estimation methods that account for driving conditions, and suggest that emission deterioration in high-mileage vehicles will remain a persistent risk, even as advanced control technologies become more widespread.