Science

Fine Particulate Pollution and Human Health

In the last two decades, the impact on human health from exposure to fine particulate matter (“PM”) pollution has become increasingly well documented in the scientific literature. According to a principal researcher in the field, that body of work has established “reasonably compelling evidence that ambient particulate matter air pollution contributes to cardiopulmonary morbidity and mortality.” See overview of research here.

Twice in the last decade the American Heart Association has convened expert panels to analyze this “growing body of epidemiological and clinical evidence” to provide healthcare professionals and regulatory agencies alike “with a comprehensive review of the literature,” and to inform public health and regulatory policies.

In 2004, an AHA expert panel drew on the available scientific evidence to conclude that, “at the very least, short-term exposure to elevated PM significantly contributes to increased acute cardiovascular mortality, particularly in certain at-risk subsets of the population. Hospital admissions for several cardiovascular and pulmonary diseases acutely increase in response to higher ambient PM concentrations. The evidence further implicates prolonged exposure to elevated levels of PM in reducing overall life expectancy on the order of a few years.” See AHA panel report here.

A wealth of post-2004 investigations have come to a similar conclusion: air pollution, including fine particulate air pollution stemming from agricultural and other biomass burning, harms human health by compromising respiratory or cardiovascular functioning, among other critical aspects of well-being, with especially severe impacts among children, the elderly, and persons with existing pulmonary or cardio-vascular disease. Correlatively, more recent studies on the impact of eliminating or reducing exposure report a range of positive health outcomes. One such recent study in the New England Journal of Medicine found a measurable increase in life expectancy following a reduction in fine particulate pollution. Access studies by the following researchers: Arbex (2004), Dominici (2006), Miller (2007), Peters (2001), Pope (2002), Pope (2004), Pope (2006), Pope (2009).

In order to summarize and evaluate the post-2004 studies, the AHA again convened a panel of experts. The panel’s update was published in mid-2010, and it served to reinforce the 2004 conclusion that air pollution laden with fine particulates imposes untenable risks of illness and death to exposed populations. In addition, several new conclusions were reached, including the following:

  • Even short-term exposure to PM2.5 “can trigger cardiovascular disease-related mortality and nonfatal events, including myocardial ischemia and MIs, heart failure, arrhythmias, and strokes.”
  • Certain population subsets may be especially vulnerable to PM2.5-associated cardiovascular morbidity and mortality, including the elderly, persons with preexisting coronary artery disease, persons with diabetes, women, and persons who are obese.
  • There does not appear to be a discernibly “safe” threshold for PM2.5 exposure.

In addition, the 2010 AHA panel summarized the evidence identifying biological mechanisms by which particulate pollution exposure likely exacerbates existing cardiovascular disease, triggers acute cardiovascular events, or instigates or accelerates chronic disease. The panel found that there is strong evidence for the proposition that such pollution “[augments] the development and progression of atherosclerosis” and “some support for a potential effect on several other CVDs [cardiovascular diseases], including hypertension, heart failure, and diabetes.” See the AHA panel’s 2010 update here.

In the last two years, research into the public health impacts of particulate pollution has continued at a furious pace. Scientists and medical researchers probe both the biological and physiological mechanisms by which this type of pollution impairs human health and attempt to evaluate the fuller measure of impacts on human populations.

One recent study in the latter category raises especially significant concern. In a study of the Canadian population, a group of 15 scientists found associations between PM2.5 pollution and ischemic heart disease even with “exposure to concentrations of PM2.5 as low as only a few micrograms per cubic meter.” The group, as well, found a near linear increase in mortality from cardiovascular disease as the ambient concentration of PM2.5 increased. See the study of the Canadian population here.

In sum, the scientific and medical literature establishes that particulate pollution, such as that generated in the burning of Maui’s sugar cane fields or from its other industrial operations, presents significant to highly serious risks to persons downwind of the emissions. The severity of these health risks depends on a number of factors, including the concentration of particulates in the pollution airstream, the length of exposure, and the medical condition and health of persons forced to inhale the cane soot. There is no evidence found so far that any amount of smoke (particulates) are “safe”.