Toxic metals leaching out of brake pads in cars might mess with our ability to fight infections: Study
For years, we have known about the dark side of diesel exhaust. Now another pollutant is coming to light: dust from worn-out car brake pads. According to a new study, these dust particles, like diesel exhausts, could mess with our ability to fight infections.
Toxic metal particles from worn-out brake pads are small enough to reach the lungs, according to the researchers attached to the study. These pollutants could be responsible for increasing people's susceptibility to respiratory infections, they add.
However, Little is known about the health impacts of brake pads or non-tailpipe emissions. "I was concerned that politicians and companies were promoting zero-emission vehicles when in reality they were simply ignoring their non-tailpipe emissions. Their basis for doing so was that all the evidence suggested that the tailpipe emissions that were responsible for the majority of the adverse health effects. Certainly, diesel emissions were the first target to tackle, but not the only one," Dr Ian Mudway, who led the research at the MRC Centre for Environment and Health at King's College London, told MEA WorldWide (MEAWW).
Dust from the brake pad makes up for a large portion of inhalable pollutants called particulate matter 2.5 (PM 2.5), constituting 20% of total PM2.5 traffic pollution released into the environment. In comparison, only 7% of PM2.5 pollution comes from tailpipe exhaust fumes at roadside sites, says the study.
Talking about the health impacts of brake pad dust, Dr Mudway says, "Generally speaking healthy individuals are very effective at neutralizing, or eliminating these metals in the short term. But in most cases, notwithstanding the acute effects on immunity that we saw, the effects of metals are likely to be long term and might accumulate within the body."
Dr Mudway and his colleagues decided to investigate brake pads after finding traces of metals such as copper, antimony and barium in pollutants on London's roads. Metals are toxic to the body: past research on welders and foundry workers has shown that tiny particles rich in metal components can reduce the immune system's ability to fight bacterial infections such as pneumonia. And since brake dust also contains a lot of metal particles, the researchers wanted to test if those found in brake dust can have a similar effect.
They designed an experiment in their lab that tested the effects of metals and diesel exhaust on cells that fight infections: macrophages. These cells are our body's most fierce fighters, engulfing and digesting the invading bacteria. They are also present in the lungs.
The researchers saw that the pollutants reduced the macrophages' ability to take up and destroy the Staphylococcus aureus, a bacteria that causes a common infection in the lungs. "Macrophages protect the lung from microbes and infections and regulate inflammation, but we found that when they are exposed to brake dust, they can no longer take up bacteria," says Dr Liza Selley, who conducted the research at the MRC Centre for Environment and Health at King's College London and Imperial College London.
But when the team added particles that block the toxic effects of metals, macrophages bounced back to the earlier fierce state. They also bounced back when they were given a break from exposure to the pollutants.
The team compared results from cells exposed to brake pads and diesel exhaust, both of which contain many metal particles such as arsenic, tin and antimony. But the biggest culprit, according to the team, could be vanadium: as the team increased the dose of both the pollutants, they saw that it was the only metal to be taken up by the cells increasingly.
"There is a historic literature on the toxicity of vanadium in air pollution samples related to emissions from oil-powered power stations in the North-Eastern US in the late 90s to mid-2000s. We would suggest that it would be timely to revisit this," says Dr Mudway.
In the future, the team suggests more focus on pollution from all sources, instead of being overly preoccupied with only a single source. He added, "There needs to be more work into the mechanisms by which air pollution causes harm and to identify the most hazardous components."
The study has been published in the journal, Metallomics.