Tire and brake wear could be the next front of emissions testing, according to Emissions Analytics, an organization that conducts independent emissions tests.

Emissions Analytics found that emissions of particulate matter from tire wear can be 1,000 times worse than from tailpipes.

Particulate matter refers to solid material emitted by vehicles, as opposed to the gases more commonly associated with vehicle exhaust emissions.

Because exhaust emissions are becoming more tightly regulated, and more electric cars are on the road, particulate matter from tire and brake wear now make up a larger share of vehicular emissions, according to Emissions Analytics.

According to a press release from the organization, tests involved a "popular family hatchback" with new, correctly-inflated tires. The hatchback's tires emitted 5.8 grams of particulate matter per kilometer, compared to 4.5 milligrams per kilometer from the exhaust, according to Emissions Analytics.

That means tire-wear particulate emissions were higher than exhaust particulate emissions by a factor of 1,000, the organization noted.

The implication of this test is that electric cars may not be free of particulate emissions after all.

2020 Tesla Model X

Electric cars have an advantage on brake wear. Regenerative braking means drivers don't need to use mechanical brakes as often as they would in gasoline cars.

But battery packs add a lot of weight to electric cars, making them harder on tires, Emissions Analytics noted.

The same goes for increasingly-popular SUVs, the organization said.

Emissions Analytics is a prominent voice for independent emissions testing.

It exposed a majority discrepancy between the real-world emissions of European diesel cars and laboratory tests, and has pushed for more rigorous standards for heavy-duty trucks.

Emissions Analytics is also part of an effort to establish an independent emissions-testing agency, similar to how the Insurance Institute for Highway Safety (IIHS) currently functions for crash tests.

Increased electric-car adoption will gradually decrease "tailpipe" emissions, which could bring emissions from other sources to the fore.

So far, General Motors has expressed interest in using greener tires from a manufacturing standpoint, but no other major automaker has followed its lead.