Let the Asthma Blame Games Begin
COST Commentary: Yes, this article is transportation related. Road vehicles are the source of a varying, but significant, percentage of ozone produced in most major cities, including Austin. All these cities have official “Ozone Seasons” which are 6-7 months of the year. During this season, people are regularly reminded of the dangers of ozone and its impact on the breathing of especially young and older people. It is always related to a negative impact on asthma: an inflammatory disorder of the airways, which causes attacks of wheezing, shortness of breath, chest tightness, and coughing.
The EPA has established standards for acceptable ozone levels and a region’s ozone level is a major criterion for the distribution of federal transportation funds and for the consideration of the approval of transportation projects. So, a regions transportation and mobility can be affected by its ozone levels. While Austin has never been non-compliant to EPA ozone standards, the standards for maximum acceptable ozone levels were lowered a couple of years ago and there is consideration of lowering them again this year. This could result in Austin being non-compliant to thses much lower levels.
This article suggests there has not been proven to be a significant association between ozone and the occurrence of asthma. In fact many situations have shown there are fewer asthma cases in some of the higher ozone regions of the world. The bottom line is: the cause of asthma is unknown. This brings into question the validity of using ozone levels and, certainly, the specific established standards, as a criterion for the federal distribution of transportation funds and project approvals. It also raises the question as to the usefulness of spending hundreds of millions, or maybe billions, of dollars on ozone season and mitigation programs throughout the US. In the larger energy picture, it may also influence and tip the discussions regarding such things as coal plants and the effectiveness of urging the use of public transit to improve air quality.
By Harold Brown, published by the Georgia Public Policy Foundation
Earth Day (April 22) has slowly expanded to Earth Week, and this year it brings to Georgia the administrator of the epitome of government mission creep, Lisa Jackson of the U.S. Environmental Protection Agency (EPA). But don’t expect a celebration of this nation’s environmental advances. It’s more likely to be an indictment of industry, power plants and Georgians’ lifestyle choices (driving) for “asthma-causing pollution.”
This criticism happens every year as the May-September “Ozone Season” arrives. Newspapers tie high ozone days to asthma, as they have for nearly 30 years. Headlines such as, “Kids with asthma head indoors during smog season” reinforce the association. Unfortunately, it’s largely a myth, built mainly on statistical associations between high ozone on hot summer days and hospitalizations for asthma. Yet summer is the season of fewest asthma hospitalizations.
Hundreds of experiments show associations between ozone and asthma. Most show weak associations, probably confounded with unknown factors that affect asthma. Some studies of air pollutants showed no associations with asthma. A throw-away phrase in a recent publication by the U.S. Centers for Disease Control and Prevention (CDC) says a lot about the malady: “[T]he etiology of asthma is unknown….” Etiology is the “the set of factors that contributes to the occurrence of a disease.”
Singling ozone out as the cause is nearly impossible, even using complicated statistical models that “control for other factors.” Often, other controlling factors are unknown, especially in the large and diverse populations that are studied.
By far the best association is the change from 1980 to 2009 in U.S. asthma prevalence and the U.S. average peak 8-hour ozone concentration. The statistical correlation is -0.86 (0 equals no association, 1 is perfect.) But this correlation is negative: Even as ozone declined, asthma increased.
The simple interpretation is that cleaner air causes asthma. What it really shows, though, is the fallacy of cavalier interpretations of associations. Interpretations based on associations lead to conflicting facts. Jackson’s EPA estimated that one of the benefits of reduced air pollution under the 1970 Clean Air Act was 850,000 “asthma attacks” avoided annually by 1990. Yet the CDC reports the number of doctor’s office visits for asthma increased by about 3.9 million per year from 1975 to 1990-92. Did reducing pollution decrease or increase asthma? (Unfazed, the EPA last month proposed new power plant mercury and air toxics standards, aimed at “preventing 120,000 cases of childhood asthma symptoms.”)
The weakness of the ozone-asthma connection is shown by other associations. After all, asthma experts consider dozens of “triggers” and “modifiers” for asthma, ranging from dust mites and cockroaches to household income and even violence. The complications make definitive statements about asthma and its causes dicey. And physicians don’t usually tell patients to stay inside. They know that most triggers are indoors, where EPA has concluded air pollution is often much higher than outdoors.
Urban areas are expected to have higher asthma rates because ozone, other air pollutants and traffic are higher there. But a CDC study of 2005 U.S. data concluded that, “Asthma prevalence is as high in rural as in urban areas.”
This is further complicated by low asthma prevalence in some countries with high pollution. East Germany was found, in the early 1990s, to have much lower asthma prevalence than West Germany although its air pollution was at least twice as high. A global report on asthma in 2004 cited prevalence for asthma symptoms for U.S. adults as 10.9 percent, but 2.1 percent for China and 2.2 percent for Russia, countries not known for their clean air.
A 2001-2004 CDC survey showed 14.6 percent of U.S.-born women reported that they had ever had asthma, versus 4 percent of women born in Mexico. For immigrants born elsewhere, it was 6.8 percent. The results were similar for men. The country of birth, and therefore the conditions of birth, was influential.
Associations with asthma are easy to find. Among Georgia counties, for example, it’s hospitalization rates and the percentage of land in cultivated crops. The correlation coefficient is statistically significant (+ 0.59) and as large as most of those for the asthma-ozone association. Yet nobody would conclude that crop cultivation causes asthma.
A further paradox in this paradox-laden condition: Several recent studies, mostly in Europe, show that children born on a farm, and especially those in contact with livestock, are less likely to have asthma, even as adults. The reason is speculated to be their contact with bacteria associated with farm conditions, especially animals.
It may be an example of the “hygiene hypothesis,” which holds that too “clean” conditions prevent childhood development of resistance to disease organisms or allergies and later cause serious problems. This may explain growing asthma rates as Americans moved from the farm and into cleaner houses. Clean houses are supposed to make children healthier, but perhaps that exposure on the farm strengthened earlier generations. It certainly holds more logic than blaming declining ozone and other air pollutants.
University of Georgia Professor Emeritus R. Harold Brown is an Adjunct Scholar with the Georgia Public Policy Foundation and author of “The Greening of Georgia: The Improvement of the Environment in the Twentieth Century.” The Foundation is an independent think tank that proposes practical, market-oriented approaches to public policy to improve the lives of Georgians. Nothing written here is to be construed as necessarily reflecting the views of the Georgia Public Policy Foundation or as an attempt to aid or hinder the passage of any bill before the U.S. Congress or the Georgia Legislature.
© Georgia Public Policy Foundation (April 15, 2011). Permission to reprint in whole or in part is hereby granted, provided the author and his affiliations are cited