Is vehicle pollution still a problem? Yes, here’s why it still harms health and climate

Did you know that lead – now known to be a toxic metal – was added to the gasoline used in cars from the 1920s to 1970s? As these vehicles roamed our neighborhoods and cities, both children and adults were exposed to dangerously high levels of lead from tailpipe emissions. 

Lead exposure shrank as countries across the world phased out its use in gasoline starting in the 1970s, with Algeria being the final country to ban leaded gasoline in 2021. 

But the battle against vehicle pollution is far from over. 

While these bans were helpful to reduce lead pollution and its negative impacts to humans and natural environments – other harmful pollutants are still emitted today through the tailpipes of internal combustion vehicles (those powered by gasoline or diesel). 

Despite clear evidence for the negative impacts of these emissions to human health and Earth’s climate, claims to the contrary still circulate online. Some of the claims are more absurd than others: on 2 April 2025, avid climate misinformer, Steve Milloy, incorrectly claimed that “From leaded gasoline to carbon monoxide to carbon dioxide and beyond, no credible evidence ever showed that any sort of auto emissions to the environment have ever harmed anyone’s health.” 

Below we will investigate the impacts of vehicle emissions on human health and the environment, and explore some possible solutions. 

Vehicle pollution harms health and the environment, but regulations are making a difference

It’s estimated that there are over 1.3 billion road vehicles* in the world – that’s one car for every 8 people on Earth. With approximately 40 million of these vehicles being electric, the remainder consists of hundreds of millions of internal combustion engine vehicles that run on fuel like gasoline or diesel, producing exhaust with varying levels of pollutants, including planet-warming CO₂. 

The main pollutants emitted from internal combustion passenger vehicles (cars, minivans, sports utility vehicles, etc.) include nitrogen oxides (NO and NO2, together called NOx), particulate matter (PM), volatile organic compounds (VOCs), carbon monoxide (CO) and sulfur oxides (SOx). Aside from pollutants, vehicles also emit CO₂ – a gas which is the primary driver of recent global warming^[1] through the greenhouse effect, as we’ve covered in the past. So what are emissions currently like?

First, the good news: pollutant emissions per individual vehicle have been greatly reduced over the last 30 to 40 years thanks to more stringent regulatory standards and advancements in technology used for post-combustion exhaust treatment (like catalytic converters)^[2] (Figure 1). 

In the U.S., for example, common pollutants have been reduced by up to 99% per vehicle since 1970 following decades of regulations^[3]. However, older vehicles don’t just disappear – many are still in use around the world. 

A 2020 report from the United Nations Environment Programme (UNEP) found that the European Union (EU), Japan, and the U.S. are the major exporters of used light-duty vehicles and that 70% of these vehicles get exported to developing countries – many of which have poor emissions standards or none at all. 

The UNEP report also notes that by 2050, the global fleet of light duty vehicles (LDVs) is expected to at least double, with major growth happening in countries who are major importers of used vehicles. Lax emissions standards in those countries are not the only problem; before the vehicles are imported, key emission-reduction equipment is sometimes removed or not working. 

However, even with advanced pollution-reduction technology in place, not everything is filtered. In fact, catalytic converters do not capture CO₂ at all and actually create it as a byproduct. Although pollution from individual vehicles has been reduced, the total amount of pollutants from exhaust still adds up given the hundreds of millions of internal combustion vehicles still operating today. As explained in 2019 paper published in Environmental Research Letters:

“despite recent adoption of more stringent vehicle emission regulations in many countries, the transportation sector remains a major contributor to the air pollution disease burden globally”^[4]

These pollutants find their way into our bodies and the natural world with a number of negative consequences. Let’s first take a look at how it affects our climate. 

As shown above in Figure 1, CO₂ – the primary driver of recent global warming^[1] – is still a byproduct of internal combustion vehicles even with the pollution-reduction technologies in place. 

Based on data from 2018, transport accounts for one fifth of global CO2 emissions. The majority of those transport emissions come from road transport, with passenger vehicles alone accounting for roughly 45% of that portion (Figure 2).

From a big picture, CO₂ emissions negatively impact humans by driving further global warming, making conditions on Earth harsher – for example, through an increased frequency and intensity of extreme heat (like heat waves)^[1]. However, it is the other pollutants (NOX, fine particulate matter, etc.) that have a more direct impact on human health^[5,6]. 

Studies have found that exposure to air pollution from vehicles can have health effects including respiratory and cardiovascular diseases – like asthma and heart disease – and even an increased risk of cancer^[5,6]. For example, a 2015 study explains:

“polycyclic aromatic hydrocarbons (PAHs), a major component of fine particulate matter from combustion sources, is also associated with onset of asthma, and increasing asthmatic symptoms.”^[6]

Humans can be exposed to these pollutants by being inside or outside of vehicles. For example, the California Air Resources Board explains that children are exposed to pollutants from buses both by waiting outside of buses or by sitting inside of them. 

A paper published in Environment International in 2022 summarizes how traffic-related air pollution can cause adverse health effects, based on a review of 353 scientific studies (Figure 3). In this paper, the authors explain:

“The findings from the systematic review, meta-analyses, and evaluation of the quality of the studies and potential biases provided an overall high or moderate-to-high level of confidence in an association between long-term exposure to TRAP [traffic-related air pollution] and the adverse health outcomes all-cause, circulatory, ischemic heart disease and lung cancer mortality, asthma onset in children and adults, and acute lower respiratory infections in children”^[7]

Air pollution may seem like a benign issue after big improvements in recent decades, but based on data from 2021, it is still one of the world’s leading risk factors for death – higher than smoking, and second only to high blood pressure (Figure 4). 

But what about the pollution from vehicle emissions specifically? 

In a 2019 Environmental Research Letters paper, researchers estimated how many premature deaths were associated with tailpipe emissions in the world and found an increase from 361,000 deaths in 2010 to 385,000 deaths in 2015^[4]. The associated health conditions considered in this paper were ischemic heart disease, stroke, COPD, lung cancer, lower respiratory infections, and diabetes. Between 2010 and 2015, some regions saw improvements, while others got worse, as explained in the paper:

“From 2010 to 2015, transportation-attributable deaths declined in the United States, the EU, and Japan in response to tightening environmental standards; in contrast, impacts increased in China, India, and other regions where growth in transportation activity outpaced environmental standards”^[4]

This disparity in trends in different countries highlights the importance of environmental standards and emission regulations to reduce negative health impacts. 

In summary, contrary to misinformation from Steve Milloy and others, the evidence is clear: pollution from vehicle emissions is an ongoing issue with real-world consequences including planetary warming and numerous health impacts that can lead to diseases and, in some cases, premature death. 

Note:

*This figure only includes light-duty vehicles such as passenger cars and light commercial vehicles (e.g., pick-ups and delivery vans), and is therefore an underestimate of the total vehicles on the road today. 

You can lower your vehicle pollution by using sustainable transport options and driving more efficiently

With clear connections between vehicle-emission pollution and negative impacts to human health and Earth’s climate, you may be wondering: can anything be done that is in our control? After all, many of us live in car-dependent societies and may not be able to afford certain options like electric vehicles. Luckily, there are several decisions you can make that can help reduce vehicle emissions. 

The U.S. Environmental Protection Agency outlines several options that can help reduce vehicle pollution:

• Drive less: the less that a vehicle operates, the less it will emit pollutants. Although many people need to drive in a car-dependent society, there are other options that can sometimes be used, such:
  • Ride sharing
  • Public transportation
  • Walking
  • Riding a bike, etc. 
• Drive wisely: this means ‘going easy’ on the gas and brakes by not rapidly accelerating or braking (when possible), going for regular tune ups, and getting the manufacturer-recommended oil. 
• Choose fuel efficient vehicles (when possible): although vehicle choices are highly personal and not everyone has the same needs, there are some vehicles that are more fuel and energy efficient than others – for example:
  • Electric vehicles
  • Plug-in hybrid vehicles
  • Cleaner-burning gasoline vehicles
  • Hydrogen fuel cell vehicles
• Don’t let your vehicle idle: when vehicles idle (stay on while not driving), they are polluting the air and wasting fuel. Turning off one’s vehicle while not driving can help reduce this pollution and waste. 

References:

• 1 – IPCC (2021) Sixth Assessment Report.
• 2 – Winkler et al. (2018) Vehicle criteria pollutant (PM, NOx, CO, HCs) emissions: how low should we go?. Nature Partner Journals (npj) Climate and Atmospheric Science.
• 3 – Choma et al. (2021) Health benefits of decreases in on-road transportation emissions in the United States from 2008 to 2017. Proceedings of the National Academy of Sciences (PNAS). 
• 4 – Anenberg et al. (2021) The global burden of transportation tailpipe emissions on air pollution-related mortality in 2010 and 2015. Environmental Research Letters. 
• 5 – Moorthy et al. (2015) Polycyclic Aromatic Hydrocarbons: From Metabolism to Lung Cancer. Toxicological Sciences. 
• 6 – Karimi et al. (2015) Polycyclic aromatic hydrocarbons and childhood asthma. European Journal of Epidemiology.
• 7 – Boogaard et al. (2022) Long-term exposure to traffic-related air pollution and selected health outcomes: A systematic review and meta-analysis. Environment International.