Smog Exposure Linked to Premature Death

Smog Exposure Linked to Premature Death



April 2008  - Exposures of less than 24 hours to 
current levels of ground-level ozone in many areas are likely to 
contribute to premature deaths, finds a new National Research Council 
report. 
Ozone, a key component of smog, can cause respiratory problems and other 
health effects. In addition, evidence of a relationship between exposures 
of less than 24 hours and mortality has been mounting, but interpretations 
of the evidence have differed, prompting the U.S. Environmental Protection 
Agency, EPA, to request the Research Council report. 
The committee that wrote the report was not asked to consider how evidence 
has been used by the EPA to set ozone standards, including the new public 
health standard set by the agency last month. 
But the evidence is strong enough that the EPA should include 
ozone-related mortality in health-benefit analyses related to future ozone 
standards, says the committee, which is chaired by John C. Bailar III, 
professor emeritus, Department of Health Studies at the University of 
Chicago. 
In addition to scientists specializing in environment, public health, and 
statistics and from across the United States, the committee includes 
scientists from Canada and Spain. 
       
Based on a review of recent research, the committee found that deaths 
related to ozone exposure are more likely among people with pre-existing 
diseases and other factors that could increase their susceptibility. But, 
the committee said, premature deaths are not limited to people who are 
already within a few days of dying. 
The EPA asked the committee to analyze the ozone-mortality link and assess 
methods for assigning a monetary value to lives saved for the 
health-benefits assessments. 
Like other federal agencies, the EPA is required to carry out a 
cost-benefit analysis on mitigation actions that cost more than $100 
million per year. 
The EPA recently used the results of population studies to estimate the 
number of premature deaths that would be avoided by expected ozone 
reductions for different policy choices, and then assigned a monetary 
value to the avoided deaths by using the value of a statistical life, VSL. 

The VSL is derived from studies of adults who indicate the "price" that 
they would be willing to pay - that is, what benefits or conveniences 
someone would be willing to forgo - to change their risk of death in a 
given period by a small amount. 
The monetary value of the improved health outcome, or VSL, is based on the 
value the group places on receiving the health benefit; it is not the 
value selected by policymakers or experts. 
The EPA applies the VSL to all lives saved regardless of the age or health 
status, so a person who is 80 years old in poor health is estimated to 
have the same value of a statistical life as a healthy two-year-old.
To determine if an approach that accounts for differences in remaining 
life expectancy could be supported scientifically, the EPA asked the 
committee to examine the value of extending life. 
For example, EPA could calculate VSL to estimate the value of remaining 
life, so a two-year-old would have a higher VSL than an 80-year-old. 
It is plausible that people with shorter remaining life expectancy would 
be willing to devote fewer resources to reducing their risk of premature 
death than those with longer remaining life expectancy. 
By contrast, if the condition causing the shortened life expectancy could 
be improved and an acceptable quality of life can be preserved or 
restored, people may put a high value on extending life, even if they have 
other health impairments or are elderly. 
The committee concluded that EPA should not adjust the value of a 
statistical life because current evidence is not sufficient to determine 
how the value might change according to differences in remaining life 
expectancy and health status. 
However, the committee did not reject the idea that such adjustments may 
be appropriate in the future. 
The committee examined research based on large population groups to find 
out if there is a threshold - a concentration of ozone below which 
exposure poses no risk of death. The committee concluded that if a 
threshold exists, it is probably at a concentration below the current 
public health standard. 
"Even in many areas EPA currently considers safe, the science clearly 
shows that the air is too often dangerous to breathe, particularly for 
those with lung disease," said American Lung Association Chair Terri 
Weaver last May when releasing the association's annual ranking of air 
pollution in U.S. cities. 
"The good news is that there's less ozone everywhere. Yet, we remain 
concerned because the science shows that millions are still at risk from 
ozone that exceeds acceptable levels," Dr. Weaver said. 
"Breathing ozone smog threatens serious health risks, including new 
evidence that links it to premature death," she said. "We're calling on 
EPA to set new standards for ozone at levels that would protect public 
health as the Clean Air Act requires." 
As people have individual susceptibilities to ozone exposure, not everyone 
may experience an altered risk of death if ozone air concentration 
changes, the committee said in today's report. 
Further research should explore how personal thresholds may vary and the 
extent to which they depend on a person's frailty, the committee said. 
The research on short-term exposure does not account for all ozone-related 
mortality, and the estimated risk of death may be greater than if based 
solely on these studies, the committee noted. 
To better understand all the possible connections between ozone and 
mortality, future research should address whether exposure for more than 
24 hours and long-term exposure - weeks to years - are associated with 
mortality, including how ozone exposure could impact life expectancy. 
For example, deaths related to short-term exposure may not occur until 
several days afterward or may be associated with multiple short-term 
exposures, the committee said. 
The EPA was advised to monitor ozone during the winter months when it is 
low and in communities with warmer and cooler winters to better understand 
seasonal and regional differences in risk. 
The committee said further research also could look at how other 
pollutants, such as airborne particulate matter, may affect ozone and 
mortality risk. 
The report, "Estimating Mortality Risk Reduction and Economic Benefits 
from Controlling Ozone Air Pollution," is available from the National 
Academies Press at: http://www.nap.edu

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