The cartilage rings are C-shaped because the back of the trachea presses against the esophagus. The cartilage opens at the esophagus and is replaced by connective tissue and muscle. This gives the esophagus space to allow food to be swallowed easily. The rings of the trachea are stacked one on top of the other, with a small space between them.
In 2014, a survey of the Australian working population revealed that the most common carcinogenic exposures in the workplace were solar ultraviolet radiation, diesel engine exhaust, environmental tobacco (second-hand) smoke, benzene, lead and silica.
When all these risks are considered together, the role of chemical exposures in causing cancer is small and, as of now, not very clear. Scientists know very little about how contact with most chemicals causes cancer. Substances known to cause cancer are called carcinogens.ollution & Exposure to Chemicals Exposure to some chemicals and hazardous substances can increase the risk of cancer. A few well-known carcinogens are asbestos, nickel, cadmium, radon, vinyl chloride, benzidene, and benzene. These carcinogens may act alone or with another carcinogen to increase your risk.