Fake CDC study full of holes

Published January 1, 2002

Several newspapers and other news sources have recently reported that a study published by the Centers for Disease Control (CDC) has warned about the health dangers of living in the suburbs. Public health officials, the study says, must support smart growth in order to promote a healthy, productive population.

In fact, the study is not a CDC report. It was probably written without the official endorsement or even knowledge of the CDC.

Instead, the report was published by SprawlWatch Clearinghouse, a smart-growth group. The report, “Creating a Healthy Environment: The Impact of the Built Environment on Public Health,” can be downloaded at http://www.sprawlwatch.org/health.pdf.

The report identifies the authors as Dr. Richard Jackson and Chris Kochtitzky, both of whom work for the CDC. The report’s cover prominently displays the words “Centers for Disease Control and Prevention” underneath the author’s names. While this properly indicates their affiliation, many news sources have misconstrued it to mean CDC published the report. The report’s true publisher, SprawlWatch, has done nothing to correct this error and has obviously enjoyed a great media success.

One of the two authors is primarily an urban planner who works for CDC as an associate director for policy and planning. The other is a medical doctor who works for CDC in an administrative capacity.

These two people may have written the report with the best of intentions. But the report is as unscientific as anything ever published by smart-growth groups. It is full of logical fallacies and inconsistencies. Most important, it fails to document any of its claims.

The report’s thesis is that suburbs are a public health menace and that smart-growth is the public health solution. The report’s fundamental fallacy is the old “design myth” held dear by many architects and urban planners: “We shape our cities, and then our cities shape us.” In other words, urban design determines how we live, and better design can make us live better.

Many of the report’s key conclusions are easily refuted.

Sprawl and air pollution

The SprawlWatch report claims suburban sprawl leads to more toxic air pollution. But the authors cite no evidence this is true. In fact, dense, congested cities present more air pollution hazards than do the suburbs.

The health effects of air pollution are a function of how many miles people drive, the congested conditions in which they drive, and the concentration of driving and pollution. The SprawlWatch report points out suburbanites tend to drive more than city dwellers, and so concludes suburbs lead to more toxic air pollution.

In fact, differences in driving between the suburbs and the cities are in large part attributable to differences in family size, income, and other factors. Forcing suburban families to live in smart-growth densities will not necessarily reduce their driving.

More important, the other two factors affecting air pollution–congestion and concentration–are much worse in cities than in suburbs. To minimize the health risks of air pollution, we would be much better off moving the residents of dense cities to low-density suburbs than densifying the suburbs.

In practice, air pollution is declining not because of changes in urban form, but because of improved technology. The best way to reduce air pollution is at the tailpipe, not the ignition key. Although Americans drive three times as much today as they did in 1970, total automotive pollution is roughly two-thirds less than it was in 1970. Further improvements are easily possible at modest cost.

Sprawl and obesity

Jackson and Kochtitzky also claim, without evidence, that sprawl leads to obesity. In fact, rising incomes are what’s responsible for obesity and changing exercise habits.

While the report cites statistics indicating Americans walked or bicycled more in the past than they do today, it fails to show these changes are in any way due to suburban environments.

Increases in auto driving are largely due to increases in incomes. Government policies aimed at increasing poverty in America will do more to increase walking and cycling than policies aimed at reshaping the suburbs.

While few would seriously propose such policies, the reality is that the anti-auto, anti-suburb policies promoted by SprawlWatch will help to impoverish many Americans. Automobiles have given people access to better jobs, and without autos people’s incomes will decline.

Sprawl and pedestrian safety

Suburban sprawl, according to Jackson and Kochtitzky, is dangerous for pedestrians and bicyclists, who account for 13 percent of all traffic fatalities. However, the report makes no attempt to record what share of those fatalities occur in the suburbs vs. in the cities.

The report asserts “strong associations” between “the risk for pedestrian injuries and high traffic volume.” While it is true that many suburban highways have high traffic volume, those roads also tend to have wide lanes and are often paralleled by low-trafficked routes. By comparison, the streets in dense cities tend to have narrow shoulders for bicycles and poor alternate routes. They pose high risks for pedestrians.

The report particularly focuses on the dangers of the suburbs to children, again without citing any data. Local suburban streets tend to be broad and, since most people park in garages or driveways, clear of parked cars. This gives motorists a clear view of children or others in the streets. By contrast, most urban streets are clogged with parked cars, creating a dangerous situation for children who may dash out between parked cars in front of moving vehicles.

“The risk for injury to children living in neighborhoods with the highest traffic volumes was 13 times that of children living in the least-busy areas,” the report says. This clearly argues for more suburban neighborhoods, where traffic volumes are low, rather than for urban neighborhoods. Yet the writers somehow draw the opposite conclusion.

Suburban sprawl and the elderly and disabled

Yet again, Jackson and Kochtitzky assert, but fail to provide evidence, that the mobility problems of elderly and disabled people can be linked to the suburbs.

Elderly and disabled people do suffer from mobility problems. Many of these people choose to live in neighborhoods designed to alleviate those problems.

The report focuses on the fact that some neighborhoods lack curb-cuts for wheelchairs or shelters for bus stops. While some of those barriers can be easily eliminated, there is no reason to think that applying smart growth–high-density housing, mixed-use developments, high-density transit service–throughout the suburbs is either necessary or sufficient to address the mobility problems of the elderly and disabled.

Sprawl and water quality

“Uncontrolled growth” is detrimental to water quality, says the report. “In urbanized areas, rainfall that once filtered slowly downhill becomes surface runoff. It flows across compacted earth and impervious man-made surfaces.” That changes water flows and means pollutants directly enter streams rather than being filtered by the soil.

All of these things are true. Yet once again, the claim that suburbs are the problem is wrong. Cities have a much higher ratio of impervious surface to soil than do the suburbs. The percentage of land covered by streets in auto-oriented suburbs tends to be at least one-third less than the share of cities built before the auto. Suburbs with homes on half-acre lots have much larger areas of pervious grass and soil than urban apartments or homes on one-eighth- or one-sixteenth-acre lots.

As salmon biologists have realized in the Pacific Northwest, the solution to water quality problems is low-density development–“sprawl”–not smart growth. (See Vanishing Automobile update #21.)

Other unsupported claims

The report also briefly mentions other public health problems supposedly caused by the suburbs. In almost every case, the real problem is in dense inner cities, not the suburbs.

  • The report refers to crime in public housing developments that lack surrounding greenspace–a clear argument for suburban housing.
  • The report refers to the urban heat island effect of large expanses of concrete and asphalt–another clear argument for low-density housing.
  • In a particularly specious argument, the report blames the construction of urban schools on former toxic dumps on rich people who have moved to the suburbs, leaving urban school districts too poor to build anywhere else. As Anthony Downs has discovered, however, there is no relation between “sprawl” and the concentration of urban poverty (see Vanishing Automobile, pages 214-216,¬†http://www.fanniemaefoundation.org/programs/hpd/pdf/hpd_1004_downs.pdf).

In short, the report fails to show that any of the problems it attributes to the suburbs are really caused by the suburbs. In most cases, if the problems are caused by urban form at all, they are due more to dense cities than low-density suburbs.

Responding to the report

The report urges public health officials to become active in urban planning and provide planners “with the public health arguments they need to support ‘smart-growth’ designs and initiatives.”

It is one thing for public health officials to encourage people to exercise more. Where evidence shows that sidewalks are safer for pedestrians, it may also make sense for public health officials to encourage sidewalks. But it is quite another thing for public health officials to make a wholesale endorsement of smart growth based on murky and undocumented claims that it is safer than low-density suburban development.

Smart-growth opponents should make certain that local news sources and public health officials understand that:

  • This report is not endorsed by the CDC and is not supported by any scientific evidence.
  • Smart growth creates more air pollution, not less.
  • There is no evidence that smart growth will reduce obesity.
  • There is no evidence that smart growth makes for less dangerous environments for pedestrians, cyclists, the elderly, and the disabled–and some evidence to the contrary.
  • The solution to water quality problems is low-density development, not smart growth.

Randal O’Toole ([email protected]) is senior economist with the Thoreau Institute (www.ti.org ) and author of the recent book, The Vanishing Automobile and Other Urban Myths.