Air Pollution Associated with a Higher Cardiovascular Disease Risk

Written by Jessica Patella, ND. This study found that long-term exposure to outdoor air pollution and traffic pollutants in China, specifically fine particulate matter and nitrogen dioxide, was associated with the development of coronary artery calcification. 

Ambient air pollution has been attributed to 4.5 million deaths in 2015, but limited research has investigated the effects in areas with high air pollution due to industrialization ^1-3.  Cardiovascular disease is the leading cause of death worldwide and has been associated with long-term exposure to air pollution ^1,4.  A recent population-based study found long-term exposure to ambient air pollution was associated with a higher coronary artery calcium score, a key risk factor to atherosclerosis (hardening of the arteries) and heart disease ¹.

The research was conducted in China due to the fact that it is the most populated country in the world and has significant air pollution ^1,2.  The goal of the research was for addressing the public health concern of cardiovascular disease, through early detection.  One method to determine subclinical atherosclerosis, a key factor of heart disease, is by measuring coronary artery calcium (or carotid intima-media thickness) non-invasively ^1,4,5.

The research included 8867 Chinese participants from 25-92 years of age (average age 56.9 years, 53.6% males), that were suspected of having coronary heart disease ¹.  All participants underwent imaging for coronary artery calcium (via computed tomography, lesions defined as >/= 130 Hounsfield units and >/= to 1 mm³).

Estimating exposure to long-term air pollution was developed using an algorithm that accounted for: fine particulate matter (< 2.5 micrometers), nitrogen dioxide, ozone, traffic (tailpipe and non tailpipe emissions), population density and land use ¹.  The annual averages for fine particulate matter, nitrogen dioxide and ozone were 70.1(+/-20.0), 41.4 (+/-14.7) and 93.9 (+/-10.5) respectively ¹.  Air pollution concentrations varied amongst the participants, with highest levels in those in urban areas (Hebei province) and lowest in rural areas (the south of China) ¹.  Of the participants 95% had exposure greater than 35 micrograms/m³ for fine particulate matter and 56% had estimated exposures greater than 40 micrograms/m³ for nitrogen dioxide ¹.

The average coronary artery calcium score was 91.4 (+/- 322.2 Agatston units).  Long-term exposure to fine particulate matter, nitrogen dioxide, ozone and distance to the nearest roadway were all associated with higher coronary artery calcium scores ¹.

When the analysis was with predicted exposure to concentrations below the national standard the following results were observed:  the association between nitrogen dioxide and coronary artery calcium was statistically significant (NO2 per 10 μg/m3: 24.0%; 95%CI, 6.4%to 44.5%). The association with ozone was not significant (O3 per 10 μg/m3: 7.4%; 95%CI, −0.5%to 16.1%).  The association between fine particulate matter and coronary artery calcium was significant only in postmenopausal women (PM2.5 per 10 μg/m3: 34.5%; 95%CI, 5.8% to 70.9%) ¹.

In conclusion, long-term exposure to outdoor air pollution and traffic pollutants in China, specifically fine particulate matter and nitrogen dioxide was associated with the development of coronary artery calcium, an early marker for atherosclerosis and heart disease ¹.  Researchers feel this should be used to inform air-pollution standards worldwide for public health ¹.

Source: Wang, Meng, Zhi-Hui Hou, Hao Xu, Yang Liu, Matthew J. Budoff, Adam A. Szpiro, Joel D. Kaufman, Sverre Vedal, and Bin Lu. “Association of Estimated Long-term Exposure to Air Pollution and Traffic Proximity With a Marker for Coronary Atherosclerosis in a Nationwide Study in China.” JAMA network open 2, no. 6 (2019): e196553-e196553.

Open Access. This is an open access article distributed under the terms of the CC-BY License.

Click here to read the full text study.

Posted August 5, 2019.

Jessica Patella, ND, is a naturopathic physician specializing in nutrition and homeopathic medicine and offers a holistic approach to health. She earned her ND from Southwest College of Naturopathic Medicine in Tempe, AZ, and is a member of the North Carolina Association of Naturopathic Physicians. Visit her website at www.awarenesswellness.com.

References:

1. Wang M, Hou Z-H, Xu H, et al. Association of Estimated Long-term Exposure to Air Pollution and Traffic Proximity With a Marker for Coronary Atherosclerosis in a Nationwide Study in China. JAMA network open. 2019;2(6):e196553-e196553.
2. 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. The Lancet. 2017;389(10082):1907-1918.
3. Pope C, Burnett RT, Krewski D, Jerrett M, Shi Y, Calle EE, et al. Cardiovascular mortality and exposure to airborne fine particulate matter and cigarette smoke: shape of the exposure-response relationship. Circulation. 2009;120:941-948.
4. Gepner AD, Young R, Delaney JA, et al. Comparison of Coronary Artery Calcium Presence, Carotid Plaque Presence, and Carotid Intima-Media Thickness for Cardiovascular Disease Prediction in the Multi-Ethnic Study of AtherosclerosisCLINICAL PERSPECTIVE. Circulation: Cardiovascular Imaging. 2015;8(1):e002262.
5. Diez Roux AV, Auchincloss AH, Franklin TG, et al. Long-term exposure to ambient particulate matter and prevalence of subclinical atherosclerosis in the Multi-Ethnic Study of Atherosclerosis. American journal of epidemiology. 2008;167(6):667-675.