4
Levels of two major air pollutants have been drastically reduced since lockdowns began in response to the COVID-19 pandemic, but a secondary pollutant — ground-level ozone — has increased in China, according to new research.
Levels of two major air pollutants have been drastically reduced since lockdowns began in response to the COVID-19 pandemic, but a secondary pollutant — ground-level ozone — has increased in China, according to new research.