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.