Delayed health effects can be reversible or permanent. Permanent effects don't go away when the exposure stops. For example, breathing asbestos over a period of time may cause lung disease. Once the lung disease begins, it will continue even if the exposure stops or decreases. Cancer is an example of a delayed health effect.
Cancer is the uncontrolled growth and spread of abnormal cells in the body.
There are many kinds of cancer. Cancer can be caused by a number of things, including exposure to toxic substances, ultraviolet sunlight and ionizing radiation. Exposure to some chemicals, such as benzene and asbestos, can produce cancer in humans. Some chemicals produce cancer in animals, but whether they will in humans is unknown. Because cancer may not appear until 5 to 40 years after exposure, determining the cause of cancer is difficult.