An international research team led by the University of Technology Sydney (UTS) and the Woolcock Institute of Medical Research (WIMR) has found that even a sub-chronic low level exposure to particulate matter can have an adverse effect on lung health.

In a paper in the American Journal of Physiology - Lung Cellular and Molecular Physiology (AJP-Lung), the researchers suggests that their findings should be taken into consideration for the planning of roads and residential buildings.

Air pollution is a ubiquitous problem and comprises gaseous and particulate matter (PM). Epidemiological studies have clearly shown that exposure to PM is associated with impaired lung function and the development of lung diseases such as chronic obstructive pulmonary disease and asthma. To understand the mechanisms involved, animal models are often used. However, the majority of such models represent high levels of exposure and are not representative of the exposure levels in less polluted countries, such as Australia. Therefore, in this study we aimed to determine whether low dose PM₁₀ exposure has any detrimental effect on the lungs.

Mice were intranasally exposed to saline or traffic-related PM₁₀ (1μg or 5μg per day) for three weeks. Bronchoalveolar lavage (BAL) and lung tissue were analysed. PM₁₀ at 1μg did not significantly affect inflammatory and mitochondrial markers. At 5μg, PM₁₀ exposure increased lymphocytes and macrophages in BAL fluid. Increased NACHT, LRR and PYD domains-containing protein 3 (NLRP3) and IL-1β production occurred following PM₁₀ exposure.

PM10 (5μg)exposure reduced mitochondrial antioxidant manganese superoxide (antioxidant defence system) and mitochondrial fusion marker (OPA-1) whilst increased fission marker (Drp-1). Autophagy marker Light chain 3 microtubule-associated protein (LC3)-II and phosphorylated-AMPK were reduced, and apoptosis marker (Caspase-3) was increased. No significant change of remodelling markers was observed.

—Chan et al.

r on the paper, said that low level air pollution was often mistakenly treated as "safe" and not harmful to health.

In Sydney and other Australian capital cities the levels of traffic related air pollution (TRAP) are low by world standards and not often considered a problem in terms of developing chronic lung disease. However almost everyone living in an urban area is exposed to TRAP. Sydney has a lot of new construction taking place, as well as a growing population and increased traffic is inevitable.

—Dr Yik Chan from UTS and WIMR, and co-lead author

Researchers from the Kolling Institute, UNSW, Chinese University of Hong Kong, Chinese Academy of Sciences were also involved in the study that showed that, after three weeks, mice exposed to low levels of traffic related PM10 had an inflammatory response.

These results have important implications for new [building] developments. For example, should schools or day care centres be built next to busy roads?

Our results indicate that PM is a pro-inflammatory molecule, which exerts effects even at low concentrations. In our model we found strong, and statistically significant evidence of, lung inflammation and dysregulated mitochondrial activity. The mitochondria are the powerhouse of the cell, which means that any changes to the mitochondria effects energy production by the cell, and therefore how the cell divides and responds to external stimuli.

—Chief Investigator Associate Professor Brian Oliver

The researchers say that people living alongside major traffic corridors need to be aware of the potential adverse effects on their respiratory health.

Resources

• Yik Lung Chan, Baoming Wang, Hui Chen, Kin Fai Ho, Junji Cao, Guo Hai, Bin Jalaludin, Cristan Herbert, Paul S Thomas, Sonia Saad, and Brian G. Oliver (2019) “Pulmonary inflammation induced by low dose particulate matter exposure in mice” American Journal of Physiology-Lung Cellular and Molecular Physiology doi: 10.1152/ajplung.00232.2019