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New Vehicle Air Filters Trap Tiny Troubling Pollution Particles

Air Quality: Researchers show that new vehicle air filters do a better job than conventional ones of trapping potentially harmful vehicle exhaust particles less than 100 nm in diameter

by Puneet Kollipara
February 7, 2014

Credit: Environ. Sci. & Technol.
A scanning electron micrograph shows ultrafine particles (white) from vehicle exhaust trapped on fibers from a new type of vehicle cabin air filter.
Credit: Environ. Sci. & Technol.
A scanning electron micrograph shows ultrafine particles (white) from vehicle exhaust trapped on fibers from a new type of vehicle cabin air filter.

When a driver cranks up her car heater or air conditioner, a cabin air filter blocks dust, pollen, and particulate matter from vehicle exhaust from blowing into the car. But these filters struggle to catch super-tiny exhaust particles that may contribute to lung and heart disease. Now researchers report that a new cabin filter with small fibers can trap large amounts of particulate matter, especially possibly damaging ultrafine particles (Environ. Sci. & Technol. 2014, DOI: 10.1021/es404952q).

Scientists know that micrometer-diameter particulate matter poses cardiovascular and pulmonary health risks. But a growing body of research suggests that smaller particulates from vehicle exhaust can also lodge in people’s lungs, enter the circulatory system, and cause inflammation, which may trigger asthma attacks or worsen heart disease. Ultrafine particles (UFPs), which are less than 100 nm in diameter, can penetrate deeper into the lungs than other particulate matter can. They also dance around the pollution-trapping fibers in current cabin air filters.

Many people may not know that such tiny particles exist, much less that they pose health risks, so automakers may not feel the need to install better filters, says Yifang Zhu of the University of California, Los Angeles. To curb exposure on their own, passengers could turn off the cars’ open-air ventilation and set the cabin air to recirculate. But over time carbon dioxide levels can build up to five or more times the outdoor concentration as passengers exhale. Some research, Zhu says, suggests that CO2 at that level impairs reaction time and decision-making in drivers.

Zhu and UCLA colleague Eon S. Lee sought a way around this CO2-versus-UFP dilemma. They thought the solution could be high efficiency cabin air filters. The researchers obtained two types of custom-made filters from Switzerland-based firm IQAir. Both filters are made from glass and polymer fibers smaller than those in conventional filters. Zhu and Lee figured that the smaller, closer-packed fibers would block more UFPs.

To test that prediction, they put a dozen passenger vehicles through four separate test drives each involving a different filter scenario: They drove the vehicles on local roads and a freeway with the already installed conventional filter, each of the two new IQAir filters, and no filter installed. The researchers monitored in-cabin and outdoor air quality through several standard methods, including condensation particle counters. The new filters far outperformed the manufacturer-installed ones, the researchers found. The custom filter with the smallest fibers kept UFP levels in the cabin 93 to 99% lower than outdoor road levels. Conventional filters achieved just 35 to 70% reductions.

The researchers caution that these tests are short-term ones. They don’t know yet if the new filters can maintain that performance in the long term. Moreover, the custom filters’ smaller and denser fibers cause air to flow into the cabin somewhat more slowly than conventional filters do. Also it’s not yet clear how much these filters would cost to make and install, Zhu says. Still, this proof-of-concept study, she says, shows the filters’ promise at letting drivers keep outside air flowing in, while keeping UFP out.

Doug Brugge, a professor of public health and community medicine at Tufts University, agrees that the study is a good demonstration of the benefits of the new filters. He suggests that the team also study the filters in a more real-world context. For example, some passengers may roll down their windows, hurting the filters’ effectiveness, he says.



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Tina (June 8, 2015 10:55 AM)
Does this also filter cigarette smoke generated by smokers who leave their arm out with cigarettes or who blow their smoke out the window when at red lights?
John R Nelligan (June 30, 2016 11:13 AM)
I am a layman so please forgive My ignorance . Where can I purchase an air filtration system for my apartment that takes out all nano particles. Pollution is bad where I live . Being disabled and on a limited income it makes it hard to move and pollution is bad everywhere . Any advice would be appreciated . Thank you for you time .
Richard James (France) (March 12, 2017 4:51 AM)
There is no doubt dust, etc, passes through a car's ventilation system filter. Dirt, etc, appears on the windscreen.

Faster fan rotates, higher intake of air putting more load on filter.

I drive so I am not up the vehicle in front tail pipe, diesel fumes make me feel sick. No filter would stop that.

Would a different design of hood/bonnet that sweeps the particles upwards help.

Thing is, a finer filter also blocks quicker.
Thomas (May 15, 2017 8:17 AM)
Car drivers pollute then outside for the other to breathe, but the inside must be clean.

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