The respiratory tract serves as a target organ and portal of entry for pollutants that may cause disease in other organs. For example, changes in the respiratory tract may have a cascading effect on cardiac function.

• In 1994, acute respiratory conditions affected 80% of the population
• Respiratory conditions account for 10% of all hospital discharges, and circulatory system diseases account for 17% of hospital discharges
• The 2 leading causes of death in the U.S. are heart disease & malignant neoplasms; approximately 30% of the deaths caused by malignant neoplasms are due to lung cancer

Most respiratory and heart diseases occur in smokers. PM is thought to alter the prevalence of death due to chronic obstructive pulmonary disease and cardiac disease. Therefore, the effects of PM on these diseases are manifest largely in smokers.

• Typical individual at rest takes about 12-15 breaths per minute, but breathing rate can triple during hard work
• At rest, 500-700 mL of air is inhaled and exhaled with each breath; there is about 1100 mL of reserve air in the lungs that is not exhaled during normal breathing
• Approx. 10-20 cubic meters (12-24 kg) air inhaled per day
• The gas exchange area of the lungs is approximately 30 sq. meters and is perfused with over 2000 km of capillaries

Anatomy of the Respiratory System

Go to Air Quality Table of Contents