Overview. If you frequently experience shortness of breath or you hear a whistling or wheezy sound in your chest when you breathe, you may have asthma â a chronic condition that causes inflammation and narrowing of the bronchial tubes, the passageways that allow air to enter and leave the lungs.
1 At 47,958 kilometres (29,800 miles) in total length, the Pan-American Highway is the longest road in the world.  The road starts in Alaska, North America and ends in the lower reaches of South America.
The 0 in its route number indicates that US 20 is a coast-to-coast route. Spanning 3,365 miles (5,415 km), it is the longest road in the United States, and the route roughly parallels that of Interstate 90 (I-90).his is because US 20 was not a planned coast-to-coast route while US 30 was. US 20 originally ended at the eastern entrance of Yellowstone Park; it was extended in 1940. The highway's eastern terminus is in Boston, Massachusetts, at Kenmore Square, where it meets State Route 2.