Chrysotile vs amphibole

(Vietnamnet) – Although sharing the same commercial term as asbestos, chrysotile differs from amphibole in terms of physical and chemical properties.

The differences between chrysotile and amphibole

Due to its chemical property, after entering human body via inhalation, chrysotile fibre will be disposed from the lung in 0,3 to 11 days or decomposed by the acid environment created by the macrophage.

Whereas, amphibole fibers, which is straight and needle-like and has a long half-life could cause tumors and inflammation symptoms. After 10 to 20 years of incubation, the tumor will develop into cancer and other lung related diseases. Therefore, amphibole has been banned worldwide, whereas, chrysotile is till used in 147 countries. In Vietnam, chrysotile has been the only fibers used since 1963.

chrysotile

At the Conference on the use of chrysotile in Vietnam and in the world on 28 July 2017, Associate.Prof Luong Duc Long – The Director of the Vietnam Institute on Building Materials presented that the main components of chrysotile were silicon and magnesium while amphile were consisted of silicon and iron. Therefore, in material science, they can be considered two different type. Asbestos cememt products only contain a small amount of chrysotile from 8 to 10%, the rest consists of 55% of cement and 35% of natural ash dust.

He added that the chrysotile fibre has hollow structure which allows the adhesive materials (which is cement in the case of A/C roof sheet) to fill in and create a strong, stable and durable connection.

According to PhD Ngo Vinh Bach Duong, in 2015, the Institute of State and Law, carried out a study on chemical safety including a study on the legal framework regarding the safe use of chrysotile in different countries. Based on his research, all countries regulate that it is unnecessary to apply any safety measures if chrysotile is soaked in natural or artificial adhesives. Hence, if chrysotile is pressed in adhesive such as cement or in gearboxes, there is no need to apply safety measures even in disposal. The United States had banned chrysotile in the past, however, the Supreme Court evoked the ban because many studies have demonstrated that products, which do not emit chrysotile fibers, do not cause cancer.

The problem of substitute products

In fact, many projects have been implemented in the seek of an ideal substitute material. In 2014, the Vietnam Institute of Buidling Materials conducted a “Study on testing and assessing the quality of asbestos fibre cement sheets and PVA fibre cement sheets”, the results has demonstrated that the breaking load, fexural strength and breaking force of AC roof sheet were greater than those of PVA one.

Specificially, the flexural strength of AC roof sheet is from 17.6 to 22.7 MPa, and the breaking load is P=453.2N; whereas, theses of PVA one are 11.5Mpa and P=230.5N respectively.

The Ministry of Science and Technology has collaborated with the Vietnam Institute of Building Materials to research on chrysotile alternative materials, the results have shown that the strength of substitute roof sheet is two times less than that of AC roof sheet.

Reportedly, Dong Anh Investment, Construction and Material Joint Stock Company (DOMATCO) has twice tried to produce alternative roof sheet in 2001 and 2004 but failed due to poor quality and high production cost.

Mr. Le Van Nghĩa – The General Director of the company – confirms that the company still stored 2 tons of inventory of alternative roof sheets that cannot be sold. In addition, the company also imported non-chrysotile roof sheet from Thailand for sale, however, the test results indicated that the substitute ons still contained 4% of chrysotile.

In the past, Navifico and Tan Thuan Cuong have invested in alternative technology. Despite of investing VND billions in non-chrysotile technology, Navifico is now shut down; whereas, Tan Thuan Cuong mostly produces AC roof sheets to maintain the operation.

Mr. Ngo Thanh Duong – The Deputy Director of Production – revealed that the company was founded in 2007 with the primary goal of producing non-chrysotile roof sheets. However, the company faced many difficulties trying to sell its products due to the much higher price comparing to AC roof sheets. As a result, non-chrysotile roof sheets only account for 2-3% of its production, the rest is AC roof sheet.

On 1st July 2017, the Office of the Government issued the Document No.7232/VPCP-KGVX which requested the Ministries and Agencies to continue studying on chrysotile substitute material meeting the criteria of quality and price.

Thanh Loan