Breathing polluted air for even 2 hours can increase blood pressure, potentially raising the risk of cardiovascular disease in those exposed to smog.

In susceptible patients this small increase may actually be able to trigger a heart attack or stroke. In a study, which appeared in the journal Hypertension, researchers tested 83 people as they breathed levels of air pollution similar to those in an urban city near a roadway. The air pollution caused diastolic pressure (lower number in a blood pressure reading) to rise within 2 hours. Blood vessels were impaired for as long as 24 hours. Tests showed that microscopic particles in the air, rather than ozone gases, caused the rise in blood pressure and impaired blood vessel function. If air pollution levels are forecasted to be high, those with heart disease, diabetes or lung disease should avoid unnecessary outdoor activity.

Blood vessels were impaired for as long as 24 hours. Tests showed that microscopic particles in the air, rather than ozone gases, caused the rise in blood pressure and impaired blood vessel function. If air pollution levels are forecasted to be high, those with heart disease, diabetes or lung disease should avoid unnecessary outdoor activity.