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New “Pine Tar” Scandal: Natural Substances Interact with Engine Emissions to Create Additional Air Pollution Hazard

By Henry Ehrlich

Polluter? The lonesome pine gets lonesomer

In a recent joint post, Drs. Chiaramonte and Ehrlich took Senator Rand Paul to task for claiming that cleaner air has no connection to asthma because asthma rates have risen as “air pollution” has fallen over the last generation.  They have also written individually (here and here) about the role that soot, or “black carbon,” which is often quite local, plays in the epidemic.  The larger point is that air pollution is not one thing.  Reducing the amount of sulfur dioxide has been beneficial.  Reducing soot is a swell idea.  So is reducing mercury.

But the plot continues to thicken.  New science, new complexity.  Felicity Barringer wrote in the New York Times the other day:

“Fine atmospheric particles — smaller than one-thirtieth of the diameter of a human hair — were identified more than 20 years ago as the most lethal of the widely dispersed air pollutants in the United States. Linked to both heart and lung disease, they kill an estimated 50,000 Americans each year. But more recently, scientists have been puzzled to learn that a subset of these particles, called secondary organic aerosols, has a greater total mass, and is thus more dangerous, than previously understood.”

These particles are not a byproduct of power generation but internal combustion.  They “are formed not during combustion but later, in the wake of interactions between pollutants and natural chemical compounds…These gaseous byproducts were thought to incorporate themselves into tiny airborne drops of liquid that would then dissipate quickly as the drops evaporated.

“The new study finds instead that they attach themselves more tightly to airborne organic particles, creating tiny tar balls that evaporate more slowly and persist longer than anyone had thought.”

The article did not specify the source of these natural culprits.  However, an email to reporter Barringer brought this reply.

“The compounds that occur naturally, and [are] used in the authors’ laboratory experiment, are emitted by trees. The one used in the experiment was alpha-pinene… which, as you may guess, comes from pine trees.”

Obviously, our ideas about air chemistry and public health are as elusive and variable as the winds.  What can be done?  We can’t get rid of all the pine trees (and there is doubtless other vegetation involved), and we can’t get rid of internal combustion any time soon.  Maybe we should just stop scientific research.

Photo by Wikipedia.org


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