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.
Workers may be exposed to a combination of cancer-causing chemicals (carcinogens), which increases their cancer risk. The risk of lung cancer in asbestos workers who also smoke cigarettes is at least 50 times higher than the risk in nonsmoking asbestos workers.orkers may be exposed to a combination of cancer-causing chemicals (carcinogens), which increases their cancer risk. The risk of lung cancer in asbestos workers who also smoke cigarettes is at least 50 times higher than the risk in nonsmoking asbestos workers.