Why physicians who treat hypertension should know more about air pollution.

Exposure to ambient levels of particulate matter (PM) air pollution increases the risk of a host of cardiovascular diseases and events. One potential mechanism explaining this association is that acute exposure to PM at high concentrations is capable of raising blood pressure within hours to days. Epidemiologic studies confirm that even commonly encountered levels of airborne pollutants can result in a prohypertensive response in humans. Several biologic pathways may be involved, including autonomic nervous system imbalance and arterial vascular dysfunction/vasoconstriction due to systemic oxidative stress/inflammation triggered by PM inhalation. The clinical importance of this vasopressor response and its relative role in promoting cardiovascular events associated with PM remain unclear. Because air pollution exposure is ubiquitous throughout the world, however, all health care providers and especially those who treat hypertension should be aware of this emerging and important biologic relationship.