How Asbestosis Occur?

Asbestosis is a chronic inflammatory and fibrotic disease of lung (mainly of parenchymal tissues of lung are involved) which occurs due to chronic (rarely may be due to acute inhalation also) inhalation and retention of asbestos. Asbestosis is an occupational lung disease as it occurs commonly among individuals working in factories which produce asbestos products or end users of the asbestos containing products due to exposure to asbestos for long duration.

How asbestosis occurs?

Asbestosis occurs due to inhalation of asbestos fibers into lungs (around terminal bronchioles and alveolar ducts). Asbestos has two types of fibers, first type is called amphibole which is thin and straight and the other type is serpentine (curved). The amphibole is mainly responsible for asbestosis, as they are able to penetrate deep into the lungs. When the amphibole asbestos fibers reach alveoli (air sacs) where oxygen from air is transferred to blood, the local immune system gets activated and inflammatory response is provoked. Inflammatory response is generated by any foreign body (in asbestosis the fibers of asbestos act as foreign body).

The immune inflammatory response is chronic and tries to remove foreign bodies (asbestos fibers) from the body and macrophages ingest and stimulate fibroblasts to deposit connective tissue. Macrophages try to digest asbestos fibers, but unable to do so due to resistance of the fibers. As macrophages can not digest asbestos fibers, they die off and release cytokines, which attract more macrophages and more deposition of connective tissues and result in formation of fibrous connective tissue mass and finally fibrosis of lungs (interstitial fibrosis), occur. Due to fibrosis the alveolar wall becomes thick. Thick alveolar wall reduce elasticity and diffusion of gas (oxygen, carbon dioxide etc.), which reduce oxygen transfer from alveolar air to blood and carbon dioxide transfer from blood to alveolar air for removal from body.

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