Study Finds Ozone Concentrations at Current Clean Air Standards Levels Can Impair Even Healthy Lungs
25 July 2009
Exposure to ozone at levels currently deemed safe by the NAAQS clean air standards can have a significant and negative effect on lung function, according to researchers at the University of California, Davis. The results are published in the 1 August issue of the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine.
In March 2008, the US Environmental Protection Agency (EPA) established a new primary 8-hour standard for ozone of 0.075 parts per million (ppm), and a new secondary standard set at a form and level identical to the new primary standard. The previous primary and secondary standards were identical 8-hour standards, set at 0.08 ppm. (Earlier post.)
The new standard was at the higher end of options proposed by EPA staff scientists in a paper submitted in 2007 (earlier post), and fell above the standard recommended by scientific and medical groups, including the Clean Air Scientific Advisory Committee (CASAC) which assists the Administrator of the EPA.
Ground-level ozone (O3) is created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOCs)—as well as gaseous HCl, as determined recently (earlier post)—in the presence of sunlight. Motor vehicle exhaust and industrial emissions, gasoline vapors, and chemical solvents as well as natural sources emit NOx and VOCs that help form ozone.
Our research indicates that the threshold for decrements in ozone-induced lung function in healthy young subjects is below this standard. Specifically, we found that 6.6 hours exposure to mean ozone concentrations as low as 70 parts per billion have a significant negative effect on lung function, even though the current NAAQS standards allow ozone concentrations to be up to 75 parts per billion (ppb) over an eight-hour period.
—Dr. Edward Schelegle, University of California, Davis
To test whether mean ozone concentrations above and below the new standard induce lung function decrements and to further study the time-course of these decrements, Schelegle and colleagues recruited 31 healthy non-smoking individuals to participate in 6.6-hour sessions during which they were exposed to ozone at 60, 70, 80 or 87 ppb or filtered air while undergoing six 50-minute bouts of moderate exercise followed by 10-minute breaks. A 35-minute lunch break separated the third and fourth bouts of exercise.
Lung function for each subject was assessed before, during and after exposure, and each individual answered a questionnaire evaluating their subjective symptoms. Of the four levels of ozone concentration tested, Dr. Schelegle and colleagues found significant decrements in both lung function and subjective respiratory symptoms at 70 ppb and above, beginning at 5.6 hours after exposure.
These data tells us that even at levels currently below the air quality standard, healthy people may experience decreased lung function after just a few hours of moderate to light exercise such as bicycling or walking. While these changes were fully reversible within several hours, these findings highlight the need to study susceptible individuals, such as asthmatics, at similar ozone concentrations and durations of exposure. These studies are needed to better understand the acute rise in hospitalizations that often occur in conjunction with high-ozone periods.
—Edward Schelegle
The study also supports the previously reported smooth dose-response curve associated with ozone. That is, the higher the level of ozone, the greater the decrease in lung function. However, the healthy subjects in the study showed a marked individual variability in their responses to ozone, with a few exhibiting strong sensitivity to ozone concentrations. What causes some individuals to respond strongly while others do not is still unknown.
In an accompanying editorial in the journal, James S. Brown of the US Environmental Protection Agency notes that Schelegle and his colleagues do not, nor did they seek to, explain the determinants of susceptibility in young, healthy adults. “Only with continued research efforts will we be able to better characterize the susceptibility in some healthy individuals, to the effects of short-term ozone exposures.”
Dr. Schelegle also notes the need for further research to further elucidate the precise mechanisms that determine an individual’s ozone responsiveness in both healthy and susceptible populations.
Understanding how these mechanisms change with repeated daily exposures is critical, especially as ambient ozone levels are often elevated several days in a row.
—Edward Schelegle
Resources
Edward S. Schelegle, Christopher A. Morales, William F. Walby, Susan Marion, and Roblee P. Allen (2009) 6.6-Hour Inhalation of Ozone Concentrations from 60 to 87 Parts per Billion in Healthy Humans. Am. J. Respir. Crit. Care Med. 180: 265-272. doi: 10.1164/rccm.200809-1484OC
James S. Brown (2009) Acute Effects of Exposure to Ozone in Humans: How Low Can Levels Be and Still Produce Effects? Am. J. Respir. Crit. Care Med. 180: 200-201
EPA Ground-Level Ozone website
Fortunately in the virtual future, we will not have to worry about naturally occurring ozone as simulators are incapable of recreating thunderstorms. But there is the pesky problem of all those EVs we will soon be making. Electrical motors, ozone generators (for health!) and upper atmosphere UV/O2 are all sources of ozone.
But then if you don't live in a virtual world - what do we do about mother nature's impertinent thunderstorms?
Posted by: Reel$$ | 25 July 2009 at 09:40 AM
There should be no attempts to modify any of the permissible ozone levels by the EPA or any other agency of Federal or State Governments until the US government forbids the commercial growing of tobacco and the commercial manufacturing of tobacco products in the US.
All monies and efforts should be spent to eliminate this greater danger with more financial payoff prior to dealing with a much lessor danger.
The US postal service will be the only entity allowed to sell tobacco products and these at very high prices. They will be imported from foreign countries. ..HG..
Posted by: Henry Gibson | 25 July 2009 at 10:10 AM
What other result can be expected from a California institution. These results may be very true, but no California State institution would dare to publish any other results.
California had and has had the full opportunity to require ZEV vehicles, but was deceived by the oil and gas industry into believing in practical, inexpensive and efficient fuel cells in the immediate future. The oil and gas industry are the major producers of hydrogen.
The production of Hydrogen from natural gas and its storage, transportation and use in fuel cell automobiles releases more CO2 per unit of energy delivered to the wheels than does an optimized diesel. It always will and it will always do it far more expensively.
California is still trying to hide the fact that fuel cells and their use could not and never will be able to compete with ZEVs on efficiency. Co-generation equipment installed at various places get higher fuel efficiency than the best automotive fuel cell and this does not include the losses involved in producing hydrogen by any means.
Electrolysis from wind or solar energy to produce hydrogen for automotive fuel cells loses at least %80 of the electric energy compared to the direct use in battery powered cars.
Lithium battery and other battery storage is always far more efficient than hydrogen production and fuel cell use. It is far less costly.
Electric motors in modern electric cars produce no ozone. AC and DC motors with brushes, commutators and their sparks did produce ozone.
Since TZERO demonstrated a relatively high performance lead battery operated car, there had been no doubt that adequate electric cars could be made and used. The TZERO demonstrated the range extender concept very well with their range extender optimized for high performance. A range extender optimized for low cost would be adequate for most automobile use days where it would get no use.
ZEVs do not produce ozone. Much ozone prodution on the roads would be eliminated with cars that are able to only creep forward slowly in traffic jams on battery power with a stopped engine.
Lane lines prevented the danger of people driving on the wrong side of the road better than all laws ever did. Hybrid and batery cars with range extenders and electric creeping will do this as well for ozone and all other products of an engine. ..HG..
Posted by: Henry Gibson | 25 July 2009 at 11:00 AM
"..chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOCs)..."
Both of these come out of car tail pipes by the ton every day. It used to be if you breathed deeply on a summer day in L.A. your chest hurt. Ever since we have had air quality standards I would say the air quality has gotten better, even though there are more people driving more cars.
We can solve respiratory problems caused by our own actions. It has been done before and it can continue to be done now, we just need more people becoming part of the solution and fewer people spewing opinions.
Posted by: SJC | 27 July 2009 at 09:37 AM
In the late 70s early 80s - there were 60-90 days of regular AQMD alerts in LA. These days they may have one or two a year. A great improvement due to the diligence of AQMD and enviros attacking REAL pollutants.
Posted by: sulleny | 27 July 2009 at 04:07 PM
@Reel$$:
Where there's thunder, there's lightning. Gigavolt atmospheric discharge is beyond the ability of even the most sophisticated computer models. Sims have a long way to go still.
Posted by: sulleny | 27 July 2009 at 04:10 PM
Yep. You're right there. Sims have a LONG way to go!
Posted by: sulleny | 28 July 2009 at 04:45 PM
.
BAN DIHYDROGEN MONOXIDE!!!!
Dihydrogen Monoxide KILLS thousands of people every year. Children come across it and die all of the time. It is a POLLUTANT and MUST be BANNED along with all of these other scary substances!!!
.
Posted by: The Goracle | 09 August 2009 at 01:06 PM