Crisotila

Asbestos - Fibrous form of mineral silicates belonging to the serpentine family, whose fibrous mineral is the chrysotile (white asbestos).

Asbestosis – A pulmonary disease caused by long-term inhalation of dust containing a high concentration of asbestos fibers. Asbestosis is similar to silicosis, which is caused by exposure to silica. When such fibers reach the alveoli in the lung, where oxygen is transferred into the blood, the foreign bodies cause the activation of the lungs local immune system provoking a defensive inflammatory reaction, which produces a cement-like protein that cause alveolar walls to thicken, reducing oxygen transfer to the blood, as well as the removal of carbon dioxide. The constant repetition of this process throughout many years can cause a drastic reduction in lung function due to the stiffening of the lung, resulting in shortness of breath and respiratory failure. The mean time interval until the disease becomes manifest is 15 years. A person with asbestosis can not, simultaneously, develop silicosis.

Asbestos dust – Designates suspended particles or deposited asbestos particles that can become loose and remain suspended in the work environment.

Sources:
- Manual de normas de conduta para o Uso Controlado do Amianto – UCA;
- Scliar, Cláudio. Amianto, mineral mágico ou maldito? CDI – Centro de Documentação e Informação LTDA, 1998;
- O amianto no Brasil, ABRA – Associação Brasileira do Amianto, 1997 e Instituto de Defesa do Patrimônio Nacional (IDPN).

Biopersistence – It is the time that an inhaled particle remains in the lung before it is eliminated by any of the defense mechanisms of the body. Biopersistence is a recent concept and establishes that, in order to cause pulmonary damage, the fiber must be able to penetrate and remain in the alveoli.

Straight, hard and spiky fibers, like amphiboles fibers, can penetrate more easily into the lung tissue. Chrysotile fibers are curved and not pointed, and can be digested by the lung defense cells. Since they dont have the ability to penetrate the alveoli, they are quickly destroyed by the respiratory system.

Biopersistence of amphiboles: 465 days.
Biopersistence of chrysotile: from 3 to 10 days.
Biopersistence of Brazilian chrysotile: from 1.3 to 2.4 days.

Benign asbestos pleural disease – Exposure to asbestos fibers can cause diffuse pleural thickening, effusions or pleural plaques. These diseases are considered benign because they rarely cause any pulmonary deficiency and are interpreted as being a sign of exposure to asbestos. They are not related to dysfunctions or other pulmonary diseases, such as asbestosis and cancer.

Chrysotile - Known as white asbestos, this mineral belongs the family of serpentine, and has flexible, fine and silky fibers 1 mm to 10 mm in length. Chrysotile fibers are heat resistant and can be easily spun and woven into cloth. At a temperature of more than 800º C chrysotile decomposes and transforms itself into forsterite.

Concentration - A concept that is being used throughout the world is TL - Tolerance Limit. According to the American Conference of Governmental Industrial Hygienists – ACGIH, Tolerance Limit means "the concentration for a 8h/day, 40h/week workload, to which approximately all the workers can be repeatedly exposed to, day after day, without any adverse effects". This is the baseline concept used to establish the currently enforceable limit for asbestos and others substances.

Dose, size and durability (3 Ds) – Studies have shown that the potential for a substance to cause damage, such as fibrosis and cancer, will depend on the following conditions:

quantity of fibers reaching the lung;
biopersistence;
fiber size.
Longer fibers with a small diameter, like amphibole fibers, are more carcinogenic.

Dose-response effect - Paracelsus is credited with the classic toxicology saying, back in the 18th Century, that "All things are poison and nothing is without poison; only the dose [and the route of entry] makes a thing a poison". Water, which is essential to life, can cause drowning, if it penetrates the lung. Similarly, the same medicine that strengthens the heart can be fatal if administered in an excessive dose. Thus, substances will produce certain effects and can cause certain diseases depending on the dose given and time of exposure. In the specific case of chrysotile, it is generally accepted that concentrations below 1 fiber/ml are harmless to humans.

Epidemiological studies - These studies are the most important medical and scientific works aimed at investigating diseases that can affect a large number of people.
The larger the group of people studied, and the longer the observation period, the more solid the results will be. Similar investigations should be carried out by scientists throughout the world. The sum of these findings will lend credibility to their conclusions.

Exposure to Asbestos – This means exposure to suspended respirable fibers in the work environment.

Exposure time – Period in which a person is in contact with asbestos. All the fiber-related diseases are slow onset progressive diseases and they appear after a period that varies from 15 to 40 years after first exposure.

Fiber size – Very small fibers, invisible to the unaided eye, 5 to 200 µm long and with less than 3 µm in diameter, known as "respirable fibers", can be harmful to human health. Because of their size, they are small enough to enter the alveoli and remain there.

Individual sensitivity – A set of factors, largely unknown, which determine the higher or lower susceptibility of certain individuals.

Lung cancer – From the first exposure to asbestos fibers to the appearance of cancer, there is a mean time lapse of 20 years. Studies indicate that the risk for this cancer is higher among smokers and new research shows that it seems to be restricted to workers with radiological evidence of asbestosis.

Mesothelioma – It is a rare form of malignant tumor that develops in the mesothelium, the membrane that involves the lung, the abdomen and its organs. Asbestos is the primary cause of this type of cancer and the relationship with asbestos was observed in 1960, in blue asbestos miners, in South Africa. Often, the cancer does not appear for 30 to 40 or more years, after a person has been exposed to asbestos. This form of cancer is not related to smoking.
The fibers that are more likely to cause this type of cancer are long, thin and highly biopersistent. And these are the characteristic of amphibole fibers. This explains why the vast majority of mesotheliomas observed in the studies is related to exposure to blue or brown asbestos. Mesothelioma cases from exposure to chrysotile asbestos are extremely rare and this type of cancer is not exclusive to people who work in asbestos-related activities.

Powder Removal – A complex set of measures taken to control dust where it is generated. It involves cowls, piping, process damping, ventilators and filters.

Respirable asbestos fiber – They are asbestos particles with the following characteristics:

Length: more than 5 micra
Diameter: less than 3 micra
Length / diameter ratio: equal to or higher than 3:1

Residue – Any material resulting from processing the raw material which is not transformed into a product because of quality problems.