Exposure to heavily polluted air is already associated with liver disorders but a team from University of Technology Sydney has found that long-term exposure to low-level traffic pollution can also affect liver health.
Mice were exposed to 10μg of traffic-derived PM2.5 particles (roughly what humans are exposed to in Sydney) and the effects of this on their liver health was measured at four, eight and 12 weeks.
Specifically the team were looking for signs of inflammation or scarring (fibrosis), as well as changes to liver sugars and fats.
First author Dr Min Feng, a medical doctor and PhD candidate in the UTS Faculty of Science added: ‘The effect was cumulative. At four weeks we didn’t see much change, but by eight weeks there was disruption to the normal metabolic function of the liver and by 12 weeks we could see significant changes.’
The researchers noted changes in 64 specific functional proteins in the liver, many linked to conditions like fatty liver disease, the most common liver disease worldwide, occuring when excess fat builds up in liver cells. It can lead to inflammation, scarring (cirrhosis) and an increased risk of cancer and liver failure.
Lead author Professor Hui Chen from UTS said: ‘We think of air pollution as being harmful to people’s lungs, but it has a broader impact on health including on the liver.
‘The liver is critical for metabolism. It clears toxins, regulates blood sugar, and produces essential vitamins and proteins, among many other functions. If the liver isn’t functioning properly, it can leave people feeling tired and unwell due to disrupted metabolism.
‘When we inhale air pollution, the very tiny particles known as PM2.5 enter the bloodstream through the lungs. The liver, which filters toxins from the blood, then accumulates these substances, which can include heavy metals such as arsenic, lead, nickel and zinc.’
World-leading liver specialist Professor Jacob George, Director of the Storr Liver Centre at The Westmead Institute for Medical Research and a co-author on the study said: ‘Around one in three Australian adults has fatty liver disease, and it is more common in those who are overweight or have diabetes.
‘Lifestyle factors such as a bad diet, lack of exercise and excessive alcohol contribute to the development of fatty liver, however this research suggests that your environment, particularly exposure to traffic air pollution, may also be a contributing factor.’
Professor Chen concluded: ‘This study reveals even low levels can cause harm. It suggests there is no safe level of exposure to traffic-derived air pollution.’
The full research can be read here.
Photo: Jason Leung