During the 2008 Beijing Olympics, changes in air pollution were associated with changes in biomarkers of systemic inflammation and thrombosis (formation of blood clot) as well as measures of cardiovascular physiology in healthy young persons, according to a study in the May 16 issue of JAMA, a theme issue on Global Health. 1
“Air pollution is a risk factor for cardiovascular diseases (CVD), but the mechanisms by which air pollution leads to CVD is not well understood. Hypothesized mechanisms with associated biomarkers include systemic inflammation and thrombosis or endothelial [thin layer of cells that line the heart and certain vessels and cavities within the body] dysfunction,” according to background information in the article. “As a condition for hosting the 2008 Olympic Games, the Chinese government agreed to temporarily and substantially improve air quality in Beijing for the Olympics and subsequent Paralympics. This provided a unique opportunity to use a quasi-experimental design in which exposures and biomarkers were measured at baseline (pre-Olympics), following a change in pollution (during-Olympics), and then repeated after an expected return to baseline (post-Olympics).”
David Q. Rich, Sc.D., of the University of Rochester, New York, and colleagues conducted a study to determine whether markers related to CVD pathophysiological pathways (biomarkers for systemic inflammation and thrombosis, heart rate, and blood pressure) are sensitive to changes in air pollution. The researchers measured environmental air pollutants daily and also measured various biomarkers and other measures (heart rate, blood pressure) in 125 healthy young adults before, during, and after the 2008 Olympics (June 2-October 30). The biomarkers measured included those associated with systemic inflammation (fibrinogen, C-reactive protein [CRP], white blood cell [WBC] count) and thrombosis or endothelial dysfunction (platelet activation markers P-selectin [sCD62P] and soluble CD40 ligand [sCD40L] as well as the adhesive endothelial glycoprotein von Willebrand factor).
Concentrations of particulate and gaseous pollutants decreased substantially (-13 percent to -60 percent) from the pre-Olympic period to the during-Olympic period. There were reductions in the average concentration of sulfur dioxide (-60 percent), carbon monoxide (-48 percent), nitrogen dioxide (-43 percent), elemental carbon (-36 percent), PM2.5 (-27 percent), organic carbon (-22 percent), and sulfate (-13 percent) from the pre-Olympic to the during-Olympic period. “In contrast, ozone concentrations increased (24 percent). Pollutant concentrations generally increased substantially from the during- to post-Olympic period for all the pollutants (21 percent to 197 percent) except ozone (-61 percent) and sulfate (-47 percent),” the authors write.
The researchers observed statistically significant improvements in SCD62P levels (by -34.0 percent), and von Willebrand factor (by -13.1 percent). Changes in the other outcomes were not statistically significant after adjustments for multiple comparisons. In the post-Olympic period when pollutant concentrations increased, most outcomes approximated pre-Olympic levels, but only sCD62P and systolic blood pressure were significantly worsened from the during-Olympic period. “The fraction of above-detection-limit values for CRP was reduced from 55 percent in the pre-Olympic period to 46 percent in the during-Olympic period and reduced further to 36 percent in the post-Olympic period. Interquartile range increases in pollutant concentrations were consistently associated with statistically significant increases in fibrinogen, von Willebrand factor, heart rate, sCD62P, and SCD40L concentrations.”
“Although these findings are of uncertain clinical significance, this study provides quasi-experimental, mechanistic data to support the argument that air pollution may be a global risk factor for CVD.”
Francesca Dominici, Ph.D., and Murray A. Mittleman, M.D., Dr.P.H., of the Harvard School of Public Health, Boston, write in an accompanying editorial that “China's dilemma, like many countries with emerging industries, is how to reconcile rapid economic growth with environmental protection.”2
“In recent decades, China has achieved industrialization and urbanization. However, China has been much less successful in maintaining the quality of urban air. Several factors challenge the implementation of air pollution controls in China: heavy reliance on coal as a main heating system, especially in subsidized housing; lack of political incentives for trading slower growth for less pollution; economic factors: most Chinese factories and power plants run on extremely thin margins and fines for polluting are generally lower than the cost of controlling emissions; and economic transformation of the landscape, from ubiquitous construction sites to the rapid expansion of the nation's vehicle fleet. If air pollution in China and other Asian nations cannot be controlled, it could spread to other continents. A recent study by Lin et al provides compelling evidence that Asian emissions may account for as much as 20 percent of ground-level pollution in the United States. Clean air is a shared global resource. It is in the common interest to maintain air quality for the promotion of global health.”
1. (JAMA. 2012;307:2068-2078.
2. (JAMA. 2012;307:2100-2102.