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.
Mercury is a neurotoxinneurotoxinA substance that is known or suspected to be poisonous to nerve tissue.. 1  How someone's health may be affected by an exposure to mercury depends on a number of factors: 2  the form of mercury (for example, methylmercury or elemental (metallic) mercury) 3  the amount of mercury in the exposure; the age of the person exposed (the fetus is the most vulnerable) how long the exposure lasts; how the person is exposed -- breathing, eating, skin contact, etc. the health of the person exposed. The effects of mercury exposure can be very severe, subtle, or may not occur at all, depending on the factors above.