Don't Hold Your Breath
It's summertime and the usual air pollution warnings are with us again.
The Environmental Defense Fund announced recently that most Americans live in neighborhoods where the additional cancer risk from toxic chemicals in outdoor air is more than 100 times higher than the goal set by Congress in 1990. This means, said EDF, that 360 of every one million Americans will develop cancer from air pollution.
The claim has led to predictable headlines: "Air quality report find cancer risks for most New Englanders," "Smog study points to local cancer risk," and "Pollution study links N.J. air to cancer." Scary stuff.
In reality, though, the EDF study does not say that the air we breathe is getting any dirtier or more dangerous to our health. A closer look shows why.
First, the notion that toxic substances in the air may cause cancer in humans has not gone unnoticed over the years by Congress or the Environmental Protection Agency. The Clean Air Act Amendments of 1977 directed EPA to develop so-called national emissions standards for hazardous air pollutants (NESHAPs). But the law was much easier to enact than it was to implement.
Over the next dozen years, EPA tried to issue the air pollution standards required by the law. But only a dozen or so standards were ever issued. Why? The law required EPA to assess the existence and extent of cancer risks for the pollutants of concern as a prerequisite to regulation. Simply put, EPA could never justify stringent air pollution standards, because the available science failed to indicate that air pollutants caused real and significant risks of cancer at ambient exposure levels. The absence of risk permitted industry to fight successfully standards that would bring little or no benefit at tremendous cost.
But what science could not do, Congress could--and did--for EPA.
As part of the Clean Air Act Amendments of 1990, Congress decided to eliminate science from the process of developing air pollution standards. Rather, Congress simply listed nearly 200 substances for which EPA was required to develop emissions standards--regardless of the existence or extent of the risk posed by those substances.
In effect, Congress declared by fiat that the substances posed significant risks of cancer or other health effects. and then ordered EPA only to determine what the emissions standards should be--not whether the substances needed to be regulated in the first place.
This bring us to the current report. EDF simply has combined Congress' declaration that these substances cause cancer with guess-timates of exposure to produce an alarming report, filled with pseudo-statistics. The study does not represent an accounting--or even a reliable estimate--of human exposure to air pollution or cancer caused by that pollution.
This bring us to a second important fact.
The fundamental premise of the report--that low-level exposures to various air
pollutants cause cancer--is based strictly on assumptions, not scientifically proven facts. The reality is that there is no body of credible scientific research that links U.S. air pollution levels with cancer.
The report assumes that the pollutants in question cause cancer at low levels of exposure. But that assumption is now roundly criticized as being unrealistic. It is based on experiments where laboratory animals, bred to be predisposed to cancer, are given very high doses of chemicals for their entire lifetime. If some of the animals get cancer, then it is assumed the chemical will cause cancer in humans at doses far lower--usually by thousands of times--than doses used in the experiment. Why are such high doses used? Because if actual environmental levels are tested, no cancer will be observed even in laboratory animals bred to be cancer time-bombs.
Twenty-five years ago, little was known about how low levels of chemical exposure affected humans. Yet EPA adopted the "low levels of exposure cause cancer" assumption as a basis for regulating chemicals. The agency's decision was based on the premise that we should be "better safe than sorry." It seemed a sensible decision at the time. But after 25 years, the assumption remains unverified.
The Society of Toxicology--a professional group of scientists whose livelihood in large part depends on this assumption--has recently asked EPA to back off. Even EPA itself has retreated from the EDF report, saying "EPA strongly cautions against using the results of this modeling exercise alone to draw real-world conclusions about current local conditions." EPA's caveat was apparently missed by the headline writers.
What's the bottom line? EPA statistics show that the air we breathe is getting cleaner every year. The risk of cancer may actually be 100 times, or even 1,000 times, less than the goal set by Congress. The fact is that there is no scientific data showing any risk at all.
So the EDF "study" was all smoke and mirrors, you ask? Something like that. So it's okay to breathe again? You bet.
Steven Milloy is a public health specialist at the Cato Institute and publisher of the Junk Science Home Page http://www.junkscience.com.