The toxic trade-off of stricter car emission standards (airqualitynews.com)

Stricter vehicle emissions standards are dramatically reducing the overall amount of volatile organic compounds (VOCs) released by petrol cars, but new research suggests that the pollution left behind may be more chemically harmful than previously thought. A study published in Environmental Science and Ecotechnology found that as vehicle standards became tighter, oxygenated volatile organic compounds (OVOCs), a group of chemicals that contribute to air pollution and pose health risks, accounted for a growing share of exhaust emissions. Researchers from the Chinese Research Academy of Environmental Sciences, the Chongqing Academy of Ecology and Environmental Sciences and Peking University tested seven petrol vehicles, including six conventional cars and one non-plug-in hybrid. The vehicles were tested on a dynamometer under different starting and driving conditions, with researchers analysing individual chemicals in the exhaust. The results showed that total VOC emissions from conventional vehicles during low-speed cold starts fell by about 75%, from 287.8 milligrams per kilometre (mg/km) for China IV vehicles to 71.8 mg/km for China VI models. However, OVOCs increased from around 20–22% of total VOCs to about 35%. The hybrid vehicle produced particularly notable results under certain conditions. During low-speed hot starts, it emitted 25.4 mg/km, compared with 13.3 mg/km from...