Automobiles: Pollution & Energy Use


It is possible that no invention has had as profound an effect on society as the passenger automobile. It did not take long after its introduction in the early part of this century for the auto to quickly become the primary means of transportation in the United States, where there are now 752 motor vehicles for every 1,000 people (World Almanac 2011). While no other country can match the excessive automobile use of the U.S., it’s not for lack of trying. Even in China, where the use of bicycles by its citizens is legendary, the number of cars has been doubling every five years for the past 30 years (World Resources Institute, hereafter “WRI” 172).

But reliance on cars is not without its problems – the most obvious being air pollution and energy consumption.

Pollution: General

Pollution by cars causes lung cancer, respiratory problems, urban smog, and acid rain (Brown 25). By 1970, after decades without government regulation, air quality had become a serious problem. The first federal Clean Air Act was passed during the Nixon Administration to curtail the ever-increasing amount of pollution caused by automobiles and industry, and Congress passed an updated version in 1990 (WRI 182). However, the Clean Air Act didn’t prohibit pollution; it simply defined an “acceptable” amount. Further, the legislation addressed only certain airborne contaminants, while ignoring others. Perhaps most significantly, although bad air was outlawed, it still exists. More than half of the people in the U.S. live in areas that failed to meet federal air quality standards at least several days a year (30 Simple Energy Things You Can Do to Save the Earth, hereafter “30 Simple Things,” 11), and around 80 million Americans live in areas that continually fail to meet these standards (WRI 63). Despite the Clean Air Acts, the reality is that air pollution continues to be a major public health problem.

As bad as the air is in the U.S., in other countries which have waited too long to address the pollution caused by cars, it’s worse. Mexico City, São Paulo, New Delhi, and Bangkok are grappling with serious air problems. And much of that pollution is caused by private automobiles (Brown 25).

Pollution: Ground-Level Ozone

One way cars create pollution is by contributing to the amount of ground-level ozone (not to be confused with the atmospheric ozone layer). In the atmosphere, the ozone layer shields the planet from harmful ultraviolet radiation rays. But on the ground, ozone is another matter, causing hazy smog and respiratory problems. Most ozone pollution is caused by motor vehicles, which account for 72% of nitrogen oxides and 52% of reactive hydrocarbons (principal components of smog) (30 Simple Things 11). The seriousness of ground-level ozone should not be underestimated. According to the World Resources Institute:

Ozone pollution has become widespread in cities in Europe, North America, and Japan as auto and industrial emissions have increased. … Breathing ozone concentrations of 0.012 ppm &emdash; levels typical in many cities &emdash; can irritate the respiratory tract and impair lung function, causing coughing, shortness of breath, and chest pain … Evidence also suggests ozone exposure lowers the body’s defenses, increasing susceptibility to respiratory infections (65).

Pollution: Lead

Cars also pollute by emitting lead from leaded gasoline. Although the use of lead in gasoline is banned in the United States, leaded gasoline is common in other countries. In fact, of the countries for which data is available, 43% use nothing but leaded gasoline. Many of the rest use at least some leaded gasoline in their energy mix. This is a definite cause for concern:

One of the oldest metals used by humans, lead is a cumulative neurotoxin that impairs brain development among children and has been connected to elevated blood pressure and resulting hypertension, heart attacks, and premature death in adults. Emissions from vehicles is the largest source of lead exposure in many urban areas (WRI 266-267).

The effects of all this pollution on human health are unsettling. A study of U.S. cities found that mortality rates were 17-26% higher in cities with the dirtiest air compared to those with the cleanest air. Not surprisingly, the study also found correlations between bad air and lung cancer and cardiopulmonary disease. The risks translate roughly to a two-year shorter lifespan for residents of dirty-air cities. On a global basis, estimates of mortality due to outdoor air pollution range from about 0.4-1.1% of total annual deaths (WRI 63-64). In the U.S., 30,000 people die every year from automobile emissions (“Bicycling and Our Environment” 1). [Also see our separate page on lead.]

Pollution: Global Warming

Perhaps even scarier than the direct damage to our bodies from auto pollution is the fact that car emissions are contributing to an overall warming of the entire planet, which could destroy the world’s food chain.

Cars emit carbon dioxide (CO2), a heat-trapping gas. In fact, they emit a lot of it: 20 pounds per gallon of gas burned (NRDC 12, Zuckermann 29). Atmospheric concentrations of CO2 have increased by 30% since preindustrial times, and much of that increase is directly related to the burning of fossil fuels. According to the Worldwatch Institute: “CO2 levels are now at their highest point in 160,000 years, and global temperatures at their highest since the Middle Ages” (Brown 26).

The effects of this global warming are frightening: rising sea levels, dying coral reefs, spreading of infectious diseases, and extreme weather conditions, including droughts, rare forest fires, historic floods, and severe storms. Even more frightening, these events are not just predictions – they’re happening right now (Brown 26).

Energy Use

The amount of energy used by automobiles is staggering. Transportation of all types accounts for more than 25% of the world’s commercial energy use, and motor vehicles account for nearly 80% of that (WRI 171). In numerical terms, the figures are hard to comprehend. The world used over a trillion liters of motor gas in 1995. And the U.S. accounted for 46% of that total (WRI 266-267). In fact, America’s gasoline consumption easily outstrips its production. The U.S. currently imports over half its oil (52%) even more than it did before the oil crises of 1973 and 1979. This dependence on foreign oil has significant economic consequences, and many observers feel that protecting “our” right to oil was the real reason for the U.S./Iraq war of 1991.

Americans use large amounts of gasoline not just because they drive so much, but also because they’re extremely wasteful about how they drive. The NRDC notes: “Most cars on the road carry only one person. In fact, we have so much extra room in our 140 million cars that everyone in Western Europe could fit in them with us.” If every commuter car in the U.S. carried just one more person, we’d save eight billion gallons of gas a year. The one-person-per-car scenario also greatly contributes to traffic congestion, which in turn wastes even more energy – about three billion gallons of gas a year (30 Simple Things 52-53).

But changing Americans’ habits doesn’t seem likely any time soon, as the failure of “High-Occupancy Vehicle” (HOV) lanes makes clear. To encourage commuters to carpool, some communities have designated one lane of traffic on certain roadways as HOV lanes. Commuters can drive in this lane only if there are at least two people in the vehicle. The reasoning is that commuters will want to carpool so they can ride in the uncongested HOV lane rather than being stuck in traffic in the normal lane when riding by themselves. But as Michael Bluejay points out, these lanes don’t always succeed in encouraging carpooling.

A friend and I recently had occasion to drive through Dallas during rush hour, and I had my first opportunity to see how an HOV lane worked. Basically, it didn’t. We passed hundreds and hundreds of single-occupant cars in the regular traffic lanes as we zoomed by in the practically-empty HOV lane. It struck me as really crazy: Whenever I try to encourage people to ride bikes more and drive less, they always whine to me about how ‘convenient’ it is to drive. Well, exactly how ‘convenient’ is it to sit in your car at a complete standstill, adding 30-60 minutes to your morning commute? That’s convenience?! The experience demonstrated to me how far people were willing to go to avoid carpooling. They were willing to sit there like morons, stuck hopelessly in traffic, for the ‘luxury’ of being the only person in their vehicle. Although I was disappointed that the HOV lanes didn’t seem to work, I was at least pleased to realize that all those greedy motorists were being punished with even more traffic congestion, since the HOV lane meant that there was one fewer lane to move all those cars.


Automobiles are responsible for a tremendous amount of air pollution and wasted energy. These problems impact people all over the world, both motorists and non-motorists alike, by affecting their health, their economies, and their communities. Legislation to address air pollution has been only partially successful, and air quality continues to be a major concern in countries all over the world. As for energy use, one can only hope that world leaders find a better way to address this problem than fighting wars over an increasingly shrinking supply of oil.

More stats are available in our Car Almanac.

Works Cited

“Bicycling and Our Environment.” Austin Cycling News. Aug. 1998: 1.

Bluejay, Michael. “HOV Lanes.” Bicycling in Austin. Feb. 1998. 22 June 1999.

Brown, Lester R., et al. State of the World: A Worldwatch Institute Report on Progress Towards a Sustainable Future. New York: W. W. Norton and Co., 1999.


World Almanac and Book of Facts. 1996 Mahwah, NJ: World Almanac Books, 1995.

World Resources Institute. 1998-99 World Resources: A Guide to the Global Environment. New York: Oxford University Press, 1998.

Zuckermann, Wolgang. End of the Road. Cambridge: Lutterworth Press, 1991.