Particulate Matter and Susceptible
Populations:
We
often hear warnings about ozone action days or warnings for susceptible
segments of the population to stay indoors if the air quality exceeds certain
levels. So, what does it mean to
be “susceptible”, or “at-risk population” or “sensitive population? Who belongs to these groups and why? In a review article entitled
“Particulate Matter – Induced Health Effects: Who is susceptible?” researchers
at the National Center for Environmental Assessment at the EPA located in the
Research Triangle Park in North Carolina examined the epidemiological data
acquired over the past two decades in an effort to explain and quantify
susceptible populations.
In
their review paper, they divided these populations into several distinct
categories:
1.
Life Stage – where, in very general terms persons at the extremes
(children and adults over 75 years of age) are found to be more susceptible to
PM exposures than the rest of the population;
2.
Sex – And although there have been limited studies addressing this category
and no relevant correlations found, it is generally recognized that female
respiratory systems are generally smaller and more reactive, factors that could
place them at increased risk;
3.
Race and Ethnicity – Some recent studies indicate that there may be some
differences but those differences appear to also vary by location and the
findings in one geographical region may not be the same as in another
geographical region;
4.
Genetic Factors – This category is in its infancy in our understanding
of the impact of genetic factors but some genes have already been identified
that can significantly affect antioxidant functions in the lung;
5.
Obesity – While studies have shown that exposure to PM increases heart
rate variability and higher levels of inflammatory markers in obese persons,
some of these results may also be masked by other co-existing and pre-existing
conditions;
6.
Preexisting Diseases – By far, those persons with preexisting
cardiovascular or respiratory disease form the largest segment of at-risk, susceptible
populations. Persons with asthma or COPD exhibit increased adverse reactions to
PM exposures as well as those with congestive heart failure or coronary artery
disease or other cardiovascular diseases.
The
full report can be found at:
http://ehp.niehs.nih.gov/wp-content/uploads/119/4/ehp.1002255.pdf and is well worth reading.
It is also important to understand that our definition of susceptible
populations is dynamic and evolving. And, more importantly, as the authors also
stress, adverse reactions to PM exposure is not relegated to these susceptible
groups. Given certain circumstances
and conditions, even the healthiest of those among us can be affected with the
real message being to minimize PM exposures for a longer, healthier life.
Dave
Litton
Senior
Scientist
Airviz,
Inc.
