Pollution From Vehicles
How pollution from cars, trucks and buses impacts health and the environment
How do cars pollute the environment?
Most people understand that bad stuff comes out of vehicle tailpipes when the vehicles burn gasoline or diesel.
But not everyone knows that vehicle emissions come in two main flavors: carbon dioxide pollution and air pollution. Read more below.
Carbon dioxide and pollution from vehicles
The first part of this article is about vehicle emissions and carbon dioxide pollution. Carbon dioxide is the principal greenhouse gas, so these emissions are also called “greenhouse gas” emissions, or GHGs. Let’s begin with some basics around carbon dioxide. Carbon dioxide, or CO2, isn’t harmful in and of itself. In fact, it’s necessary for plants and animals to live. We call carbon dioxide emissions that come from burning gasoline and other fossil fuels “pollution” because fossil fuels emit far more carbon dioxide than our land and oceans can absorb. The excess carbon dioxide absorbs energy and prevents the loss of heat to space. It acts like a blanket, trapping heat. And that’s causing our planet to warm to dangerous levels.
Humans started burning fossil fuels (coal, oil/gasoline/diesel, natural gas) around the time of the Industrial Revolution, beginning in the mid 1700s. Ever since then, carbon dioxide emissions have been rising faster than the earth has experienced in millions of years.
As of July 2023, the earth’s atmospheric carbon dioxide was at the highest level since humans have been on the planet.
A carbon dioxide level of 350 parts per million (ppm) is considered safe for humans to thrive on earth. Currently, the level is 422 ppm and rising quickly.
The higher the level of carbon dioxide, the higher the global mean temperature. Up to now the oceans have been absorbing about 90% of the extra heat this carbon dioxide pollution has caused, but they may have hit their limit, as the summer of 2023 saw an unprecedented rise in ocean temperatures.
In general, overloading the earth's atmosphere with carbon dioxide is causing warming land and ocean temperatures resulting in more severe storms, droughts and other weather events. Halfway into 2023, the U.S. had already experienced 12 natural disasters large enough to cost more than $1 billion in damages each. Moving away from gasoline-powered vehicles to cleaner alternatives is critical to cutting emissions.
How does transportation cause carbon dioxide pollution?
Every gallon of gasoline burned sends 20 pounds of carbon dioxide into our atmosphere, where it stays for thousands of years. Burning gasoline and diesel for transportation is the biggest source of carbon emissions in the United States.
How much carbon dioxide pollution typically comes from each car?
The average U.S. driver purchases 522 gallons of gasoline per year, adding 5.22 tons of carbon dioxide to our atmosphere. Gasoline Superusers, defined as U.S. drivers in the top 10% for gasoline consumption, use at least 1,100 gallons of gasoline a year and use on average 1,892 gallons. Superusers are each adding at least 11 tons of carbon dioxide to the atmosphere each year.
How much carbon dioxide pollution comes from transportation?
Collectively, Americans burned about 134 billion gallons of gasoline in 2022. In that year, consumption of gasoline and diesel in the U.S. transportation sector resulted in the emissions of 1,476 MMT (million metric tons) of carbon dioxide.
For a sense of scale, the US uses more gasoline than any other country – more than three times that of the next biggest gasoline user, China:
What percentage of carbon pollution comes from transportation?
Across the US, in 2022 the transportation sector caused about 30% of total U.S. energy-related CO2 emissions. In California, the transportation sector is the biggest source of carbon emissions at 38% of total emissions.
Light duty vehicles like passenger cars, trucks and SUVs make up 57% of transportation carbon emissions in the US – much more than medium and heavy duty trucks and airplanes. In California, cars, trucks and SUVs make up 28% of total greenhouse gas emissions, and 70% of the transportation sector emissions. California is one of many states and countries phasing out gasoline. Learn more about the gas car phaseout in California.
Note that the rise in SUVs has been a big part of the problem. Worldwide, SUVs were the 2nd largest contributor to CO2 increase between 2010 and 2018, surpassed only by power generation.
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Aren’t new gasoline vehicles cleaner than older ones?
Thanks to the US Clean Air Act and other regulations, newer vehicles emit less air pollution than older vehicles. See the section below on Air Pollution from Vehicles for more about that. But in terms of carbon dioxide emissions, every gallon of gasoline still sends about 20 pounds of carbon dioxide into the atmosphere, and that has not really changed over time. To the extent modern vehicles are more fuel efficient thanks to more stringent fuel economy standards, they are emitting less carbon dioxide pollution per mile driven. But plenty of vehicles (think big pickup trucks and SUVs) still get pretty lousy mileage. And on the whole we’ve been driving more miles than ever, and so the amount of gasoline we’re burning has not gone down.
We saw a small decline in gasoline use during COVID, but now people are driving more than ever, so vehicle miles traveled (“VMT”) and gasoline use are at near all-time highs.
Air Pollution from Vehicles
Now let’s turn to the second type of pollution from our cars, trucks and SUVs: air pollution.
When vehicles burn gasoline and diesel, the exhaust from the tailpipe contains toxic pollutants including carbon monoxide, smog-causing volatile organic compounds and nitrogen oxides, sulfur dioxides, formaldehyde and benzene.
How much air pollution comes from vehicles?
Across the U.S., vehicle emissions are the largest source of carbon monoxides (56% nationwide and up to 95% in cities) and nitrogen oxides (45%). California’s transportation sector accounts for nearly 80% of nitrogen oxide pollution and 80% of the pollutants that cause smog.
Nitrogen oxide (NOx) from cars, trucks and buses
Internal combustion engines produce high temperatures that burn nitrogen in the air, forming nitrogen oxide (NO) and nitrogen dioxide (NO2), collectively known as NOx. Diesel vehicles contribute 60% of NOx emissions in U.S. transportation.
NOx causes environmental issues such as acid rain and deteriorated water quality and contributes to acidification of soils and surface waters. It also forms ground-level ozone (smog) and PM2.5, both harmful to health and the environment.
Nitrogen dioxide exposure can worsen asthma and cause serious health problems including premature death, heart issues, impaired lung development particularly in children, breathing difficulties, and intensified allergic reactions.
In May 2023, the Biden administration proposed new standards for cars, SUVs, and light trucks for model years 2027-2032 to help reduce greenhouse gases and pollutants like NOx. These standards aim for pollution levels below 1% of those set in 1970. However, with U.S. annual vehicle mileage tripling to 3.2 TRILLION miles, per-mile pollution reductions have a smaller impact on overall pollution.
Read more about Nitrogen Oxides.
What are the health impacts of vehicle emissions?
Vehicle emissions are a major source of benzene, a carcinogen linked to leukemia, blood disorders and infertility. They increase risks of asthma, heart and lung disease, dementia and cancers – especially in children and for those who live near busy roads or commute long distances. Living near busy roads has been linked to developmental delays in children and disorders in pregnancy. Vehicle emissions have been linked to mental illness, including anxiety and depression, and diesel school bus emissions in particular have been shown to adversely affect academic performance and student health.
In the US, 17,000 to 20,000 people die each year from vehicle pollution, and one in three is exposed to unhealthy air. People of color are disproportionately affected, breathing an average of 66% more air pollution from cars and trucks than white residents in some regions.
Exposure to harmful toxic air pollutants from other vehicles is higher inside vehicles than outside; your car cabin is basically a “box with small holes for gas exchange” and this can lead to unhealthy air pollutants accumulating.
According to the American Lung Association, California continues to have some of the worst air quality in the country. For 2019, 2020 and 2021, of the eleven US counties with the worst combined short-term particle pollution, ozone, and long-term particle pollution levels, ten were in California. Nine in ten Californians live in areas with unhealthy air, much of it caused by the ozone (smog) and particle pollution from vehicle emissions. Los Angeles is the most polluted city in the nation in terms of ozone pollution.
How can we reduce vehicle pollution?
To reduce carbon dioxide pollution and air pollution from vehicles, we need to reduce how much gasoline and diesel we use. For people who use a lot of gasoline, switching to an electric vehicle can be very effective in cutting gasoline use.
EVs are Cleaner than Gas-Powered Cars
Electricity is getting cleaner every year, as more of it comes from clean, renewable sources like sun and wind, and 24/7 power from renewables plus battery storage is becoming cheaper than fossil fuels.
In all 50 states, according to the U.S. Department of Energy, the annual emissions from an electric vehicle are less than those of a gas car. Across the lifetime of the vehicle, total emissions depend on how much the vehicle is driven. For a gas car, the day it leaves the dealership lot is its cleanest day; for an EV, the day it leaves the dealership is its dirtiest day. If the EV is never driven, over its lifetime it will have more total emissions than a gas car, because (currently!) more emissions are involved in the manufacture of an EV and its battery than for a gas car. The more the vehicles are driven, the faster the EV becomes cleaner than the gas car. The typical “crossover” point for EVs is 15,000 to 20,000 miles.
Learn about the life cycle harms of gasoline.
In model year 2023, the highest-rated EPA combined fuel economy for gasoline vehicles was about 60 miles per gallon (MPG), while EVs achieved up to 140 mpg-equivalent (MPGe). (MPGe is an EPA measure of EV fuel economy in a common unit with gas-powered vehicles, where 33.7 kilowatt-hours of electricity are equal to the energy contained in one gallon of gasoline.)
Overall, fossil fuel vehicles make hundreds of times more waste than EVs. Claims to the contrary have been widely debunked. Indeed, in 95% of the world, EVs are cleaner.
Gasoline will always be a polluting fossil fuel that is burned once and gone forever. In contrast, there are reports of electric vehicle batteries lasting over 400,000 miles. New technology promises million-mile batteries. After the batteries can’t be used in vehicles, they have a second life providing battery electric storage for buildings. After that, their raw materials can be almost fully recycled, and recycling efforts are continuing to improve with government incentives.
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We can cut vehicle pollution faster by helping the biggest gasoline users switch to EVs
Prioritizing the drivers in the top 10% for gasoline consumption (“Gasoline Superusers”) for the switch to EVs will reduce vehicle emissions faster and more efficiently. As many Superusers are below the median income, this approach also save money for the lower-income households that are most burdened by gasoline expenditures.
In California, the average Superuser burns 3.5x more gasoline than the average non-Superuser: 1,260 gallons a year vs. 354 gallons for non-Superusers.
Switching all of California’s 5.4 million biggest gasoline users (roughly those in the top 20%) to EVs would cut gasoline use by 43%.
Cutting vehicle emissions by 50% would require 9 million EVs if the biggest gasoline users switched first, but 24 million EVs if the biggest gasoline users switched last.
Currently, EVs are being adopted by lower mileage drivers. The average EV driver only drives about 10,200 miles a year versus superusers who drive on average 24,000 miles a year.
Learn from our free webinar about how the gasoline superuser approach can help reduce car pollution faster and more equitably.
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