Forty million British people are living in cities and towns with illegally high air pollution levels. This alarming statistic is in part due to diesel exhaust, which according to new research can directly affect our lungs and make respiratory conditions worse.
An international team of scientists led by Imperial College London’s National Heart and Lung Institute recently found that diesel fumes directly stimulate nerves in our lungs leading to reflex actions like wheezing and coughing. This is bad news for sufferers of respiratory disorders like asthma as inhaling diesel exhaust could make these conditions more extreme.
The new study is the first to demonstrate exactly how particles from diesel exhaust affect the lungs by triggering nerve cells. When diesel is burnt it releases tiny nanoparticles called polycyclic aromatic hydrocarbons (PAHs), which easily enter our airways.
“It’s essentially because of their small size that they can be inhaled,” explains Lareb Dean, a PhD researcher from Imperial’s National Heart and Lung Institute. “Inhalation is our primary interest as respiratory scientists – clearance mechanisms exist in the upper airways but because of their small size, density and shape, nanoparticles are able to go through the lungs and reach peripheral areas like the alveoli. Then we have these questions of whether they are able to translocate to other areas of the body.”
Exactly how nanoparticles like PAHs behave in the human body is of growing concern to scientists. “With things like asbestos we found out too late what the effect was,” says Dean, “we need to do studies to carry out risk assessment for the potential effects of chronic exposure to other nanoparticles.”
The new finding emphasises the need to address the worrying levels of air pollution in big cities in order to protect public health. “People with pre-existing lung disorders are most at risk,” says Dean, “particularly people with asthma and COPD (chronic obstructive pulmonary disease), as well as people that are occupationally exposed to diesel fumes, like lorry drivers.”
Lucy Gumbiti-Zimuto, a medical student at the University of Cambridge, has been suffering from asthma for the past 12 years. “I’ve had asthma since I was 10,” she says, “I have noticed that when I come to London, or I’ve been in London for a few days especially, I get more asthmatic, develop a slight cough and have to use my inhaler more often.” UK air quality is currently very poor; in fact pollution levels in cities like London and Birmingham are technically illegal according to standards set out by the EU. The government recently published new plans to tackle air pollution but these have been criticised for being too weak.
“I am concerned about high pollution as my asthma isn’t that bad so people who have it worse must get really bad symptoms,” says Gumbiti-Zimuto, “it worries me not only for my health but for everyone else’s – it might cause increases in things like lung cancer.”
“It concerns me,” adds Dean, “because my research, as well as the body of literature out there, has shown that increases in particulate matter like diesel exhaust leads to an increase in mortality risk. The epidemiological evidence is really robust.”
As well as exacerbating conditions like asthma, PAHs are known to cause cancer. So why is diesel still being burnt? The government is under pressure to implement charges on diesel cars entering cities but is reluctant to do so having previously encouraged drivers to purchase them due to lower carbon dioxide emissions. To combat the issue, legal activist group ClientEarth will take the government to court to challenge its failure to effectively address the UK’s air pollution crisis so far.