Scientists have found the components of particulate matter (pm)—in addition to its mass concentration—to be the main cause of health risks and advised further investigations into the cellular oxidative potential of pm, which reflects toxicity, for a more precise understanding of the effect of air quality on human health.
A research team from National Taiwan University (NTU) and National Yang Ming Chiao Tung University (NYCU) investigated pm in an urban area and found that its substances including organic aerosols, iron, manganese, and copper, all of which increased cellular oxidative potential. Notably, these metals in the air did not always come from vehicle exhaust emissions and were more likely a result of the abrasion of brake pads; the level of such abrasion was particularly high in traffic jams.
The research team had monitored air quality for one month at a station in NTU near Keelung Road and observed that the largest fraction of pm composition, which are commonly known as secondary inorganic aerosols, comes from photochemical reactions of vehicle exhaust emissions. The pm also contained small amounts of black carbon and metals. Accordingly, congested traffic in the urban area was one of the main causes of reduced ambient air quality. Apart from the commonly known traffic pollutants, namely secondary inorganic aerosols and black carbon, metal particulates produced from frequent braking—nonexhaust emissions—were verified by the research team to have similar adverse effects on human health.
A study from Britain revealed that metal particles from the abrasion of brake pads caused cellular inflammation and increased the risk of respiratory complications just as exhaust gas emitted from engine combustion did.
Ta-Chih Hsiao, the leading researcher of this project and a professor at NTU Graduate Institute of Environmental Engineering, suggested that pm is harmful to the human body because human cells can be damaged when an excessive amount of active oxygen species from such matter accumulates in the cells, which is commonly known as free radical accumulation. According to the research, secondary inorganic aerosols, black carbon, and metals in pm were all possible causes of oxygen oxidative potential increase.
Kai-Hsien Chi, who was responsible for analyzing the components and toxicity of pm in the research and a professor at NYCU Institute of Environmental Health Sciences, pointed out that the measured mass concentration of pm failed to reveal the holistic picture of its risks and that the correlation between the mass concentration and cellular oxidative potential was weak. PM may exhibit the same mass concentration across regions, but the components can vary. A further investigation into the cellular oxidative potential of pm components is required to provide more air quality information.
NTU and NYCU research team will introduce the concept of cellular oxidative potential into the current monitor system and try to establish a next-generation air quality evaluation method which is expected to understand the real air quality for citizens and help the government develop precise and effective pollution control policy.
