Particulate matter collected from London streets caused an inflammatory response in the lungs of mice after a single exposure, a new study reports.
Outdoor air pollution by fine atmospheric particles is recognised as a public health risk that contributes to over 3m deaths annually. It is especially significant in major cities, where it is implicated in respiratory and cardiovascular disease.
The researchers – at the Weizmann Institute of Science and Ben-Gurion University of the Negev in Israel and at the University of Wisconsin-Madison in the US – collected material from the busy Marylebone Road and then dissolved it in water, before putting the solution into the lungs of mice. An inflammatory response was indicated by a significant increase in immune cells and signaling molecules called cytokines. However, adding a metal chelating agent to the solution decreased this response to control levels, suggesting that metals were the most potent components (Environm. Sci. & Technol., doi: 10.1021/acs.est.5b01449).
Metals on roadways come mainly from road dust that contains brake and tyre wear, as well as dust, soil and construction materials, says senior author Yinon Rudich; iron, zinc and arsenic are most responsible for the oxidative stress and inflammation, though chromium, vanadium and nickel may also play a role.
‘When governments and municipalities introduce regulations to control air pollution, they usually control emissions from tailpipes,’ Rudich says. ‘But they do not control these [road dust] sources which can be more harmful, according to our study,’ he adds, pointing out that a move to electric vehicles would not eliminate the problem of particulate matter pollution on roadsides.
On a more positive note, Rudich says the observed stress effects are transient. ‘We show that the effect is very local in the lung, and there is a mechanism to protect the organism from real damage. Since the effect was also confined to the lung, the body could overcome the stress in less than 48 hours.’
He is now studying what happens when mice are exposed to such material over longer periods of time.
‘This study demonstrates how a low particulate matter exposure can elicit a significant lung effect,’ comments Alison Bauer, environmental scientist at the University of Colorado, Denver, US. However, she notes the exposure period was short, that mice may respond differently from people, especially those individuals with asthma or cardiovascular disease.
‘The dose [of particulate solution] applied was quite large,’ comments Roy Harrison, environmental scientist at the University of Birmingham, UK, ‘The exposures in this study are likely to be considerably above those experienced by a human breathing air on Marylebone Road.’