New Study Shows Greater Dependence
On Cars Leads To More Pollution In World's Cities
By Roger-Mark De Souza

December 9, 1999 - People are not willing to give up their cars in order to stop air pollution and potential health hazards, according to a multi-urban study released today on public attitudes toward urban air pollution.  The study, Household Transportation Use and Urban Air Pollution, was prepared by the Population Reference Bureau, funded by the John D. and Catherine T. MacArthur Foundation and the U.S. Agency for International Development, and researched by experts in Bangkok, Mexico City, and Washington.

"The world's cities are clearly on the road to greatly increased car dependence and car pollution," notes Roger-Mark De Souza, the author of the report.  "Cars are becoming cheaper, people richer, and urban populations larger.  In recent years urban design has increasingly favored car use."

The World Health Organization (WHO) estimates that up to 700,000 premature deaths per year worldwide could be prevented in developing countries if three pollutants-suspended particulate matter (SPM), carbon monoxide, and lead-were brought down to safer levels. 

The World Bank estimates the number of motor vehicles worldwide could grow from 580 million in 1990 to 816 million by 2010.  Roughly 90 percent of future world population growth is expected to take place in cities, and cars are concentrated in urban areas.  Mexico City and Bangkok, for example, already hold about 50 percent of their respective nations' automobiles.

The report notes that cars are some of the worst air polluters.  The transportation sector, dominated by motor vehicles, contributes an estimated 30 percent of all greenhouse gas emissions.  When car dependence increases, fuel consumption rises exponentially because of growing road congestion,
fuel-inefficient vehicles, and poor vehicular and road maintenance.

Globally, transportation consumes 20 percent of all energy produced.  Demand is growing in all countries.  Importantly, energy consumption in low- and middle-income countries, now one-third that of the industrialized world, is expected to match demand in rich countries by 2015.

Researchers from the Institute for Population and Social Research at Mahidol University in Thailand, the Center for Demographic and Urban Studies at the Colegio de Mexico in Mexico, and ICF Kaiser International in the United States carried out extensive research and focus-group discussions.  Their findings include:

* In the three polluted capitals, residents "perceived some relationship between health problems and air pollution. Yet all appeared willing to accept this impact in the absence of evidence showing that it is a major threat."

* Educated people tend to be greater polluters than less educated people.

* "Male-headed households engage in more polluting behavior than female-headed households."

* Growing numbers of households in urban areas, changing household structures, and increasing household incomes have all led to the rise in the number of cars on the road.

* In these capitals, many citizens ignore the health hazards and the economic costs of rising energy use. Driving to work is increasingly more difficult. The average car in Bangkok is estimated to spend the equivalent of 44 days a year stuck in traffic. Yet 300 to 400 more cars are being added to Bangkok streets every day.

"Given the choice between carpooling and driving alone," admitted one high-income focus-group participant from Washington, D.C., "I'd rather drive alone and pollute the air."  A middle-income focus-group participant in Bangkok viewed his car use as a drop in the bucket:  "We look for convenience.  So we buy a car.  We know that when our car is added, the traffic will increase...but the traffic would be already congested if our car hadn't been added."

The report makes three policy recommendations:
1) Combine improvements in the public transportation system with regulations and incentives to encourage the use of alternatives such as walking, cycling, and telecommuting.
2) Tailor policies by socioeconomic group and gender to combat specific polluting behavior.
3) Educate the public about the impact of transportation choices, particularly on air pollution, and encourage community involvement in education efforts.

According to the researchers, however, "attitudes of individualism and consumerism constrained action that could reduce urban air pollution."

"Household Transportation Use and Urban Air Pollution," by Roger-Mark De Souza, is available free of charge to writers and members of the press.  For copies, contact PRB by fax (202) 328-3937; phone (202) 483-1100; e-mail: Or go directly to this page to download the pdf file: 

The Population Reference Bureau is the leader in providing timely and objective information on U.S. and international population trends and their implications.  PRB is a nonprofit, nonadvocacy organization, in Washington, D.C.

Roger-Mark De Souza
Coordinator, Population and Environment Programs
Population Reference Bureau
1875 Connecticut Avenue, NW
Suite 520
Washington, DC 20009-5430

Tel: (202) 939-5430
Fax: (202) 328-3937