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Study Indicates That Particles Released By Brake Pads May Be More Dangerous Than Fuel Combustion Gases, Affecting Air Quality And Health.
Air pollution is a global problem, associated with millions of premature deaths each year, according to the World Health Organization (WHO). When we think of pollution in cities, vehicle emissions, especially those from diesel engines, are commonly pointed out as the main culprit. However, a recent study revealed that something even more toxic and overlooked may be harming our health: the dust released from the wear of brake pads.
This dust, part of the so-called “non-exhaust emissions“, includes particles generated by the friction of tires, brakes, and the asphalt itself .
According to researchers, this type of emission has already surpassed exhaust emissions in many European countries. The most alarming fact: the dust from brake pads proved to be more harmful to lung cells than particles from diesel.
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The Laboratory Experiment
To reach this conclusion, scientists cultivated lung cells in the laboratory, simulating the internal lining of human lungs.
These cells were exposed to brake dust and diesel exhaust particles. The result was surprising: the cells exposed to brake dust showed significant damage, with inflammatory responses linked to severe respiratory diseases such as cancer, asthma, and pulmonary fibrosis.
Interestingly, tests showed that the copper present in these particles plays a crucial role in the observed toxicity.
When the dust was treated to neutralize the copper, the harmful impact on lung cells diminished considerably.
Despite this, current regulation in the United Kingdom, for instance, still focuses only on exhaust emissions, completely ignoring this type of pollutant.
Particle and Fibre Toxicology, 2025)
The Toxic Past Of Brake Pads
Brake pads were once produced with asbestos, a material effective at dealing with the heat generated by friction but highly toxic.
Asbestos was banned in the United Kingdom in 1999 due to its link to severe respiratory diseases like asbestosis and lung cancer. With the ban, alternatives emerged, such as asbestos-free organic pads (NAO, in English).
However, the study revealed an ironic piece of data: the dust released by these NAO pads, created to be safer, turned out to be the most toxic among the options tested. It caused more damage to lung cells than diesel exhaust dust, challenging the common perception that brakes would be a secondary issue.
The chemical analysis of these particles revealed high levels of metals, particularly copper. Copper is an essential metal for various biological functions, but when inhaled in high concentrations, it can cause lung inflammation and other damage.
Previous studies have already associated excessive copper in the air with impaired respiratory function and increased mortality.
The Role Of Electric Vehicles
With the growth of the electric vehicle (EV) fleet, many expected a significant reduction in urban pollution. While EVs eliminate exhaust emissions, they do not solve the problem of non-exhaust emissions.
On the contrary, the trend is for this pollution to increase, as EVs, due to their heavy batteries, often have more mass, generating greater wear on tires, brakes, and asphalt.
Although regenerative braking systems—which slow down the vehicle using the electric motor—reduce the use of traditional brakes, EVs still have friction brakes, responsible for emitting these toxic particles. Thus, the label “zero emissions” does not reflect the full environmental reality of these vehicles.
Regulations And Innovations On The Horizon
The introduction of Euro 7 emission standards, expected in November 2026, promises to establish limits for brake dust emissions.
This change may encourage the automotive industry to develop less toxic materials and adopt mechanisms that capture these particles before they disperse into the air.
In the United States, states like California and Washington have already taken the lead by restricting the use of copper in brake pads, mainly due to environmental concerns about water contamination.
These regulations, although motivated by aquatic preservation, may also bring public health benefits by reducing human exposure to this metal.
An Invisible Danger In The Air
It is estimated that non-exhaust emissions account for about 60% of the particles released by vehicles in the United Kingdom.
This percentage is expected to grow with the increase in the electric fleet. These particles, invisible to the naked eye, penetrate deep into the respiratory system and can reach the bloodstream, affecting various organs.
The challenge now is to convince authorities and manufacturers to expand regulations, considering these hidden and dangerous emissions. The reformulation of brake pads, with less harmful materials, emerges as an urgent and viable measure.
The air we breathe in cities is filled with these invisible particles, coming not only from exhausts but also from brakes, tires, and the wear of streets.
Science now makes it clear: ignoring these emissions is neglecting a silent threat to public health. The next step depends on the collective action of governments, industries, and society to tackle this still little-known but profoundly impactful risk.
Study available at particleandfibretoxicology and information from theconversation.
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