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 the outdoor air is more than 100 times higher than the goal set by Congress in 1990. This means, said the EDF, that 360 of every one million Americans will develop cancer from air pollution.
The claim has led to predictable headlines such as "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, this 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 the 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, the 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 the EPA to assess the existence and extent of cancer risks for the pollutants of concern as a prerequisite to regulation.
Simply put, the 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 the 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 the EPA was required to develop emissions standards -- regardless of the existence or extent of the risk posed.
In effect, Congress declared the substances posed significant risks of cancer or other health effects and ordered the EPA just to determine what the emissions standards should be, not whether they needed to be regulated in the first place.
This bring us to the current report. The 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 and 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 this assumption is now roundly criticized as being unrealistic. It is based on experiments where laboratory animals, bred to be pre-disposed to cancer, are given very high doses of chemicals for their entire life time. 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 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 that are bred to be cancer time-bombs.
Twenty-five years ago when this assumption was made policy by the Environmental Protection Agency, little was known about the effects of low-levels of chemicals on humans. The decision to use the assumption 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 the EPA to back off this assumption. Even the 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." This warning was apparently missed by the headline writers.
What's the bottom line? EPA statistics show that the air we breathe is not getting worse: every year it is getting better. Is the risk of cancer 100 times greater than the goal set by Congress? It may actually be 100 or 1,000 or even more times less. The fact is that there is no scientific data showing any risk at all.
So the EDF "study" was all smoke and mirrors? Something like that. Okay to breathe again? You bet.
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