Air Pollution

Reducing Particulate Matter Air Pollution to Prevent and Treat Hypertension

AUTHOR:
Michael J. Bloch, MD
Associate Professor, University of Nevada School of Medicine
Medical Director, Renown Vascular Care, Renown Institute for Heart and Vascular Health
President, Blue Spruce Medical Consultants, PLLC

CITATION:
Bloch M. Reducing particulate matter air pollution to prevent and treat hypertension. Consultant360. Published online March 29, 2021.

 

Development of hypertension is usually due to a combination of underlying genetic predisposition combined with environmental factors. The most commonly cited environmental factors are sedentary lifestyle, increased weight, increased sodium intake, consumption of unhealthy diet, or use of interfering substances like anti-inflammatory drugs, diet pills, or other stimulants. Although there is certainly some degree of inequity in access to a healthy diet, in general these are all essentially lifestyle choices that individuals make. Less commonly appreciated are environmental factors that occur on a larger geographical scale and that individuals have much less control of, including exposure to particulate matter air pollution.

As highlighted in a recent Scientific Statement from the American Heart Association (AHA), there is “unequivocal evidence of the causal role of fine particulate matter (<2.5 microgram in diameter)” in cardiovascular disease progression generally and in hypertension specifically.1 Exposure to particulate matter air pollution, particularly from automobile traffic, contributes to endothelial dysfunction and decreased arterial compliance, as well as other factors that increase atherosclerosis risk and lead to plaque instability. Previous observational studies have confirmed that people living in areas with high-traffic pollution have a higher incidence of hypertension and that blood pressure (BP) tends to be higher on days when pollution is higher. But these studies have been limited by their observational nature.

A recent compelling analysis by Hudda and colleagues carefully examined the effect of increasing or decreasing indoor traffic-related air pollution (TRAP) in a novel crossover design.2 They found that systolic BP increased with increasing magnitude and duration of exposure to TRAP. Increases in BP occurred within 10 min, and at 20 min, the difference in systolic BP between high and low TRAP levels was approximately 2 mmHg. Although the magnitude of effect in this study was relatively small, continual exposure likely has cumulative effects. Over time, even modest increases in BP can have a significant impact on cardiovascular risk, especially since exposure to TRAP increases cardiovascular risk through other nonhemodynamic physiologic effects as well. In fact, the 2015 Global Burden of Disease Study suggests that ambient air pollution is responsible for 4.2 million premature deaths per year, at least half of these attributable to cardiovascular disease.3

Unfortunately, exposure to ambient air pollution is yet another example of health care inequity, since minority populations and those with lower income and wealth are more likely to live proximate to high-traffic congestion. Certainly, decreasing ambient air pollution is a complex problem that requires significant investment of public health and governmental resources. Yet, even in the absence of these large-scale initiatives, the AHA Scientific Statement1 provides interventions that individuals can take on their own to reduce their exposure. These “personal exposure mitigation strategies include use of portable air cleaners, face masks and respirators, high-efficiency HVAC filter systems, and behavior modifications including staying indoors and closing windows during times of heavy traffic and moving outdoor exercise away from heavy traffic areas.”1

To do our part in raising awareness of this underappreciated risk factor, clinicians need to start informing patients of the cardiovascular risk of exposure to ambient air pollution and begin to have more conversations about mitigating exposure to reduce blood pressure and cardiovascular risk.

References

  1. Rajagopalan S, Brauer M, Bhatnagar A, et al. Personal-level protective actions against particulate matter air pollution exposure: a scientific statement from the American Heart Association. Circulation. 2020;142(23):e411-e431. https://doi.org/10.1161/cir.0000000000000931
  2. Hudda N, Eliasziw M, Hersey SO, et al. Effect of reducing ambient traffic-related air pollution on blood pressure: a randomized crossover trial. Hypertension. 2021;77(3):823-832. https://doi.org/10.1161/hypertensionaha.120.15580
  3. Cohen AJ, Brauer M, Burnett R, et al. Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study 2015. Lancet. 2017;389(10082):1907-1918. https://doi.org/10.1016/s0140-6736(17)30505-6