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.
LEAD EXPOSURE BLOOD TEST. Lead is a toxic metal that is naturally occurring in the earthâs crust. Lead and lead compounds have been used in manufacturing compounds such as paint, fuel, batteries and cosmetics. Some of the most common sources of lead exposure in the United States come from Lead-based paints found in older homes, drinking water and pottery or crystals used for eating. Occupational exposure to lead in the workplace can also occur.