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Increases in BP associated with ozone exposure

Researchers discovered possible mechanisms, including platelet activation and BP increases, by which low-level ozone exposure may affect CV health, according to findings published in JAMA Internal Medicine.

“Exposure to ozone has been associated with cardiovascular mortality, but the underlying biological mechanisms are not yet understood,” Drew. B. Day, PhD, from Duke University, and colleagues wrote.

Day and colleagues studied the cardiopulmonary pathophysiologic mechanisms that may be responsible for the association between ozone and CV mortality. They conducted a longitudinal study between Dec. 1, 2014, and Jan. 31, 2015, of 89 healthy adults (28% women; mean age, 31.5 years) living on a work campus in Changsha City, China. The participants spent a majority of their time in controlled indoor environments, which allowed for optimal characterization of the effects of air pollutant exposure, according to the researchers. They monitored participants’ concentrations of indoor and outdoor ozone, copollutants particulate matter, nitrogen dioxide and sulfur dioxide. The researchers estimated 24-hour and 2-week combined indoor and outdoor mean exposure by combining these concentrations with time-activity information and filtration conditions of each residence and office. They used single-pollutant and two-pollutant linear mixed models to assess the associations between each exposure measure and outcome measure. The analysis was controlled for ambient temperature, secondhand smoke exposure and personal-level time-varying covariates.

Data indicated that there was a variation of 24-hour ozone exposure concentrations, ranging from 1.4 to 19.4 parts per billion. In addition, outdoor concentrations ranged from 4.3 to 47.9 parts per billion. A decrease in arterial stiffness marker augmentation index (–9.5%; 95% CI, –17.7 to –1.4), as well as increases in the level of platelet activation marker soluble P-selectin (36.3%; 95% CI, 29.9-43), diastolic BP (2.8%; 95% CI, 0.6-5.1), pulmonary inflammation markers fractional exhaled nitric oxide (18.1%; 95% CI, 4.5-33.5) and exhaled breath condensate nitrite (31%; 95% CI, 0.2-71.1) were linked to a 10 parts-per-billion rise in 24-hour ozone. Increases in soluble P-selectin level (61.1%; 95% CI, 37.8-88.2) and exhaled breath condensate nitrite and nitrate level (126.2%; 95% CI, 12.1-356.2) were associated with a 10 parts-per-billion increase in 2-week ozone. There were no significant associations between other measured biomarkers, such as spirometry, and 24-hour ozone or 2-week ozone exposures.

“This study provides mechanistic support to previously observed associations between low-level [ozone] exposure and cardiovascular disease outcomes,” Day and colleagues concluded. “The findings offer insights into possible underlying biological mechanisms, namely, platelet activation and increases in blood pressure. Given that global tropospheric [ozone] concentration is rising, it is imperative to determine how to minimize its harms on health.” – by Alaina Tedesco

Disclosure: Day and colleagues reported receiving support from the National Natural Science Foundation of China, the National Institute of Environmental Health Sciences and the Doctoral Scholars Program of the Duke Global Health Institute.