Understanding the Cardiovascular Risks of Inhaling Particulate Matter: A Study of Air Pollution and Three Occupational Hazards

Abstract

Background: Particulate matter (PM) defines a group of particles that have dimensions measured in micrometers or even smaller units. Until recently, for more than half a century, studies have looked at the respiratory and carcinogenic risks of inhaling PM. Then, newer studies have shown that inhaling these particles can also promote cardiovascular risks, and different pathways by which this may happen have been hypothesized. For example, inhaled particles may not only be able to damage the cardiovascular system, but may also damage the autonomic nervous system (ANS), which regulates the cardiovascular system. The extent of these risks has become increasingly important now that cardiovascular diseases are the number one cause of death in both America and the world. These cardiovascular risks of inhaling PM are exceptionally higher for those living in large urban areas or working in many occupational settings where PM levels are higher.

Methods: First, county-level variations in American mortalities from cardiovascular diseases were studied. Multivariate regressions models were created, and model selection was used to determine which factors were most important in predicting the variation of cardiovascular mortalities. Second, laboratory results were obtained to understand the cardiovascular risks of inhaling three specific examples of PM that millions of American workers are exposed to in occupational settings. The studied occupational hazards were silica dust, multi-walled carbon nanotubes, and crude oil vapors. Measures of not only cardiovascular health, but also the ANS’s normal control of the cardiovascular system, were taken in order to determine the potential risks.

Results: Among all of the generated models, PM was significantly and positively correlated with cardiovascular mortalities. Other controls that were also significantly and positively correlated included mental health, smoking, and obesity levels. From the laboratory exposures, the inhalation of silica dust was not shown to affect the cardiovascular system directly or indirectly through the ANS. On the other hand, the inhalation of multi-walled carbon nanotubes and crude oil vapors were shown to affect the ANS’s control of the cardiovascular system.

Conclusions: Because PM was shown to be greatly associated with increased cardiovascular risks, it is exceptionally important to monitor and limit PM levels especially in large urban areas, developing countries, and occupational settings. Long-term laboratory exposure studies should be conducted to better understand the cardiovascular risks of inhaling silica dust, crude oil vapors, and multi-walled carbon nanotubes. Results from such studies will help governmental organizations in both America and throughout the world to better define satisfactory exposure limits to PM in both public and occupational settings.