Cheaper cars pollute way more than expensive ones

Scientists have found that cheaper passenger cars often release more toxic exhaust than pricier models. That finding links personal budgets to local air quality in a direct and uneasy way.

Using data from more than 50,000 on-road measurements, the team tracked how much pollution each passing car released in real traffic. The result is a sharp picture of how money and emissions move together on busy city streets.

Price links to pollution

The work was led by Dr. Omid Ghaffarpasand, an impact research fellow in vehicle pollutant emissions at the University of Birmingham (UB). His research focuses on how traffic technologies and policies change the air people breathe in growing cities.

A new study from his team linked those Birmingham measurements to the current market value of each vehicle. By comparing exhaust levels across that price range, the researchers saw how pollution shifted between the least and most expensive cars.

The team used remote sensing, a way to measure exhaust from passing cars without touching the vehicles. A laser-based device sat above the road and recorded gases in each plume of exhaust as thousands of cars drove underneath.

Each car was tagged with its Euro emission standard, a European rule that sets legal pollution limits for new vehicles.

Across diesel models, cars in the higher price bracket emitted about 40 percent less nitrogen pollution per unit of fuel than the cheapest group.

Cars that still pollute

Among diesel cars, the cheapest group released roughly 50 percent more nitrogen pollution per unit of fuel than mid range models. That difference appears even when cheaper and pricier vehicles carry the same official emissions label.

Petrol cars also tended to pollute less as price rose, but the change across the price range was much smaller. For tiny particles, petrol models showed almost no consistent shift with price.

The sensors tracked gases such as nitrogen dioxide, a toxic gas formed in engine exhaust that can inflame human lungs. These pollutants are tightly linked to asthma attacks, heart problems, and shortened lives in polluted cities.

They also tracked particulate matter, tiny solid and liquid particles that can reach deep into the lungs. Hybrid cars fell between petrol and diesel for nitrogen pollution, and fewer hybrids passed the sensor, so their price pattern is uncertain.

Unequal impacts of car pollution

Lower income drivers are more likely to buy older and cheaper cars because those are the vehicles they can realistically afford.

The Birmingham team found that these same budget constrained choices tend to put the highest polluting models on the streets in their own neighborhoods.

Professor Pope, an air quality researcher, said there is clear evidence to support vehicle price being a reliable indicator of emission performance. “Individuals from lower-income households may be more likely to own older, cheaper, and higher-emitting vehicles.”

According to Dr. Ghaffarpasand, the findings highlight the need for targeted policy interventions to address environmental injustice.

He noted that communities with fewer resources often live with higher pollution levels because cleaner cars remain out of reach.

Policy must consider cost

Because of the strong price pattern, rules that use only official emissions labels or age limits can overlook some very dirty vehicles.

Two cars that meet the same standard can pollute very differently when one is a much cheaper model in the used market.

The Birmingham team argue for tax systems that nudge buyers toward cleaner models without trapping low income drivers in older high emitting vehicles.

The researchers also point to scrappage payments, repair support, and stricter inspections for older cars as ways to cut emissions while keeping transport affordable.

Reducing exposure gaps

In many countries, lower income neighborhoods face higher exposure to nitrogen dioxide and particle pollution from traffic.

Across the United States, an analysis found that major fine particle sources often hit people of color and low income residents hardest.

Work on targeted emission strategies suggests that cutting pollution in the most affected neighborhoods can shrink exposure gaps with relatively small reductions in emissions.

Combining that approach with information on which price brackets produce the dirtiest exhaust could make clean air policies both more efficient and more fair.

Impact on drivers and cities

For individual drivers, the results are a reminder that the sticker price is only one part of what a car costs society.

A slightly more expensive used car can carry a smaller pollution footprint over its life, especially for diesel models that vary in exhaust performance.

City governments can draw lessons from the remote sensing work behind this analysis about how to monitor vehicles on their streets.

Previous studies using the same EDAR system have shown that roadside measurement can sort cleaner vehicles from heavy polluters in real traffic.

The harsh reality of car pollution

Networks of sensors, combined with ownership and price data, can help officials identify which streets and fleets contribute most to nitrogen oxides and particles.

That information can support clean air zones, bus and taxi upgrades, and transport investments that place more benefits in communities breathing the dirtiest air.

The Birmingham research highlights an uncomfortable point about fairness in the transition to cleaner transport.

People who are least able to afford newer vehicles may be driving the cars that add to the pollution around their homes and schools.

The study is published in the Journal of Cleaner Production.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–