BEIJING -?Soot aggregates are the most harmful matter in PM2.5, a group of Chinese scientists revealed.

Of the four main categories of PM2.5, fluffy soot aggregates are highly adhesive and cause the most irritation, making them the most harmful to the human body, experts from the College of Engineering of Peking University (CEPKU), Soochow University and Chinese Center for Disease Control and Prevention found in a recent study.

When soot aggregates come in contact with the human body, their high adhesiveness prolongs contact between skin and pollutants, said Duan Huiling, a dean from CEPKU.

Based on this, scientists came to the conclusion that carbon-rich fluffy soot from incomplete combustion of hydrocarbons produce the most harm, Duan said.

Particulate matter with an aerodynamic diameter of 2.5 micrometers or less, known as PM2.5, has long been a major concern for China in terms of air pollution, especially in metropolises such as Beijing and Shanghai.

Already published in Scientific Reports of the Nature Publishing Group, the research marks the first time the nanoscale characterization of PM2.5 airborne pollutants was revealed.