What is asbestos? Its properties and the dangers of the brown and blue fibers

Asbestos is a common trade name for natural mineral fibers, possessing irreplaceable characteristics such as good sound absorption, fire resistance and thermal insulation.

In fact, asbestos is divided into two main groups including amphibole and serpentine. With a straight, rough, needle-shaped structure and a slow elimination half-life, amphibole (also known as blue and brown asbestos) can cause tumors which can develop into cancer and lung diseases after 10-20 years of incubation once entering the lung. Therefore, the harmful asbestos group has been banned from using in any form all over the world, including Vietnam. In contrast, the serpentine group, which also known as chrysotile fiber is more friendly to human health. It has become the only type of asbestos to be used.

What is chrysotile? Why should we only use the fiber?

Chrysotile (derived from the Greek, where “chrysos” means gold and “tilos” means yarn, also known as “gold thread”) is a mineral fiber with twisted and soft porous structure, derived from serpentine stones scattered throughout the world. In 1877, the discovery of the largest chrysotile mine in Canada helped the chrysotile mining industry truly develop on a large scale. With outstanding features which can not be replaced by any kind of natural or artificial fibers such as high strength and elasticity, good friction, resistance to fire and alkali environment, insulation, difficult to decompose, ability to prevent bacteria and scattering…, chrysotile is considered as a useful input for more than 3,000 products such as fiber-cement (especially asbestos-cement roofing sheets), electrical and thermal insulation materials, automotive, aerospace, pharmacy, petroleum and nuclear industries, fireproof materials, textile products and a variety of others.

According to scientific studies, after entering the body through the respiratory system, the chrysotile fiber will be eliminated from the lungs in 0.3 to 11 days or decomposed by the acid environment of macrophages. Currently, chrysotile is being used under a safe and controlled manner in many countries around the world. Scientific studies confirm that no evidence of disease caused by chrysotile has been found.

Chrysotile in roofing sheets

In fact, chrysotile is used in many different industries but in Vietnam, 90 percent of the import volume is for the production of asbestos-cement roofing sheets, which are also known as fiber cement roofing sheets (according to the report of the Ministry of Construction). In the production process of AC roof sheet, chrysotile fiber accounts for only a small part of 8-10 percent while the rest is 90 percent of cement. The strong cohesion between chrysotile and cement granules during the manufacturing process makes it difficult for the dispersal of the fiber into the environment, which cause bad affect on human health.

The research result of the Institute for Building Materials – Ministry of Construction named “The production and use of asbestos-cement roofing sheets and dust-generating capacity of roofing sheets” reaffirmed: In AC roof sheets, chrysotile fibers has a close association with the hydrated cement stone. At the same time, the hydrated minerals of cement also encapsulate and penetrate deep into the chrysotile fiber.

Director of Institute of Tropical Building Materials Research and Application – Construction University – Prof. Dr. Bach Dinh Thien pointed out: “Chrysotile has a very special structure; therefore, the mix with cement will make it no longer be the original fiber. Besides, with special sticky texture, they are very difficult to disperse into the air and harm to human health. The evidence is that all countries like Germany and Russia are still using chrysotile-containing domestic water pipes which are not harmful to human health.”

Safe use of chrysotile in the production of AC roof sheets

Since more than 50 years ago, asbestos-cement roof sheets – gray simple corrugated sheets has become familiar to many families in both the countryside and the city. According to the statistics, in order to meet the large needs of people in daily life and production, the whole industry used to have more than 40 fiber cement roofing factories established. By employing a rough “wet-sheet” technique called Hatschek (Hatschek Process) technology invented by Austria, factories almost opened, weighed, and loaded asbestos in mixing tank by hand.

Today, closed automation lines help minimize the risk of asbestosis. Accordingly, the stage of mixing asbestos is automatically quantified and crushed in a closed room, then pumped to the cement mixing department. Modern production lines allow reducing direct exposure of workers because automatic camera systems have been installed at important stages in the production process. Then, staff can control production process anywhere and anytime at the central control room.

Chrysotile is used in a safe and controlled manner in the production of AC roof sheet.

With the problem of wastewater treatment, the closed production technology allows the system of input water and arising during the production process, industrial wastewater … to be gathered in tanks with standard pH concentration after passing through the automated filtering system. Wastewater will be back to the closed reuse process with the same cycle to help make use of raw materials while ensuring relatively modern water treatment.

Strict management of chrysotile in AC roof industry

Currently, to control the concentration of fiber dust in the air and ensure a safe working environment, every country has established strict management regulations for chrysotile. In Russia, the maximum permitted concentration is 2.0 fibers/ml. The US allows a maximum concentration of 0.1 fibers/ml in a shift while India allows 1.0 fibers/ml. The ASEAN countries also stipulate as follows: Thailand is 5.0 fibers/ml, the Philippines is 2.0 fibers/ml; Indonesia is 1.0 fibers/ml.

Vietnam regulates that the concentration of chrysotile dust in the air in the workplace is 0.1 fibers/ml for an average of 8 hours and not exceeding 0.5 fibers/ml for the average of 1 hour (equivalent to the standard of US). This is also a more stringent level than many countries in the same region and around the world. According to government strict regulations, AC roof sheet enterprises must also organize occupational medical examinations for workers annually, along with monitoring and supervising water and air environment at production facilities every 3 months.

Notably, the authorities such as health environment, environmental inspection, environmental and health monitoring,… also annually and irregularly inspect the environment and health of workers at organizations.

Are AC roof sheets toxic?

Scientists in Switzerland, Germany and the United States in the first studies on the durability of fibers when penetrating into the human body indicated that while 14 days is the period of elimination of chrysotile fiber in Canada, the brown and blue fibers take up to 466 days. Alternative fibers, such as ceramic fibers take 60 days, aramid fibers take 90 days, and cellulose fibers take 1,000 days. On that basis, the researchers confirmed a higher risk of cancer for employees of paper and wood mills than those at factories using chrysotile.

The report of World Health Organization concluded that there is no scientific research demonstrating either an increased risk of cancer related to the digestion of asbestos in drinking water or toxicity from asbestos digestion to human health. Therefore, it is not necessary to set guidelines on asbestos in drinking water.

Ministry-level research project: “Study of asbestos-related diseases in people exposing to the fiber” was conducted in 2009 – 2011 by the Ministry of Health, Labor and Welfare of Japan, through the World Health Organization (WHO) to fund the Health Environment Management Agency – Ministry of Health concluded: Among 447 cases of asbestos-related diseases such as lung cancer, pleural plaque and mesothelioma, only 39 samples was sent to Hiroshima Hospital, Japan for diagnosis. Japanese experts eventually identified only 08 cases of the disease, of which none had a clear history of occupational exposure to asbestos.

In 12 years (2008-2019), the program of occupational disease examination and working environment measurement for workers in the industry of asbestos-cement roofing sheets implemented by the Hospital of Construction – Ministry of Construction with scientific and methodical method annually confirmed: Not detecting typical lesions of pneumonia related to chrysotile.

Prof. Hoang Duc Kiet – Head of Diagnostic Imaging Department of Hanoi Friendship Hospital in a film reading meeting for workers of AC roof industry.

In 2010-2014, the Construction Hospital – Ministry of Construction conducted a survey on the death situation in Tan Trinh commune and other communes in Quang Binh district – Ha Giang province with a total of 1,046 households, and 4,565 people. The percentage of asbestos-cement roofs in Tan Trinh commune and Quang Binh district accounts for about 70%. The survey results show that among the communes of Quang Binh district, Tan Trinh has a lower mortality rate than that of the whole district. The characteristics and mortality rate of cancer in Tan Trinh commune is not the highest but ranks fifth among 13 communes in Quang Binh district (0.858 ‰) but still within normal limits. Analysis of air samples in homes of asbestos-cement roof of local residents did not find any asbestos fibers.