Ecology of the cardiovascular system: A focus on air-related environmental factors

Cardiology is a newcomer to environmental sciences. We aim to propose an original review of the scientific evidence regarding the effects of the environment on cardiovascular health. We report first influences of air-related environmental factors. Air temperature has a strong influence on cardiovascular mortality characterized by a V-like relationship confirming that both cold and hot periods have negative cardiovascular impacts. Furthermore, dynamic changes in temperature are likely more important than the absolute air temperature level. Cardiovascular reactions to air temperature are predominantly driven by increase in sympathetic tone. Indoor pollutants are mainly represented by smoke from cooking stoves and environmental tobacco smoke (ETS), and both are associated with increased cardiovascular mortality and morbidity. ETS is characterized by a curvilinear dose-effect relationship, showing already a significant effect even at low level of exposure and no threshold in effect appearance. Underlying ETS pathophysiology involves both effects of nicotinic stimulus on the sympathetic system and vascular oxidative stress. Smoking bans, as mitigation measures, were associated with a decrease in cardiovascular events. Long-term exposure to particulate air pollution was more recently recognized as an independent risk factor of cardiovascular mortality. Short-term increases in air pollution were also associated with an increased risk of myocardial infarction, stroke, and acute heart failure. Numerous experimental studies demonstrated that air pollution promotes a systemic vascular oxidative stress reaction followed by endothelial dysfunction, monocyte activation, and some proatherogenic changes of lipoproteins. Furthermore, air pollution favors thrombus formation as a result of increase in coagulation factors and platelet activation. Further studies are required to confirm that stricter air quality regulation or antioxidant regimen translate into some clinical benefits. In conclusion, ambient air temperature and pollution are major contributors to cardiovascular diseases. Improving air quality is now part of cardiovascular prevention.