Asbestos is a natural fibre that was used for decades in insulation, siding, asbestos floor tile, joint compound, asbestos ceiling tile, asbestos roofing and brake pads. Asbestos was commonly used in these products due to its heat resistant characteristics and durability.Asbestos-containing insulation, gaskets and packing have been used in conjunction with high-temperature equipment such as boilers, turbines, steam pipes, pumps, valves and furnaces. Asbestos-containing materials were also commonly used during the construction of houses and offices, as well as on ships and in industrial settings.
Asbestos became increasingly popular among manufacturers and builders due to its sound absorption, tensile strength, resistance to fire, heat, electrical and chemical damage, and affordability. The older generation in Sri Lanka was exposed to woven asbestos at their homes as wicks of lamps and mantles in Patrolmax lamps during kerosene days. Also, asbestos products became popular in Sri Lanka as a substitute building material due to the scarcity of other building materials such as timber and clay tiles.
According to statistics, Sri Lanka has been importing white asbestos from various countries for more than 60 years. Though there are many forms of asbestos, Sri Lanka imports only the white variety of asbestos (Chrysotile) for the production of roofing and ceiling sheets, where asbestos is mixed with cement acting as a binding agent reducing fibre escape. It has already been scientifically proven that blue and brown asbestos fibre can cause cancer, hence it needs to explore the impact of white asbestos fibre on human health.
Asbestos is not a mineral itself. It is a collective term given to a group of minerals whose crystals occur in fibrous forms. The term asbestos was adopted for commercial identification. Asbestos fibres are naturally-occurring minerals found in underground rock formations. It is a combination of six naturally-occurring silicate minerals which have long, thin fibrous crystals. These fibrous materials can be released through abrasion and other processes (King, 2007).
The six minerals commonly referred to as asbestos come from two distinct groups of minerals such as Serpentines and Amphiboles. The Amphiboles group is subdivided into five groups such as Amosite (Brown Asbestos), Crocidolite (Blue Asbestos), Anthophyllite and Tremolite and Actinolite (King, 2007).
Asbestos possesses many unique properties which have led to its application in more than 3,000 products. The main properties are high tensile strength, high resistance to abrasion, resistance to corrosion, resistance to heat, non-combustibility, resistance to alkali attack, durability and toughness, good electrical insulation properties and chemical inertness.
In 2011, the International Programme on Chemical Safety (IPCS) with the World Health Organization (WHO) revealed that all forms of asbestos pose health hazards. According to the WHO, 107,000 people die each year from asbestos-related lung cancer, mesothelioma and asbestosis mainly due to occupational exposures. Asbestos factory workers, carpenters who work on roofing projects, labourers of asbestos store facilities and workers at building demolishing sites are in high-risk categories.
The IPCS 2011, worked with members to strengthen the capacities of the Health Ministries to provide leadership for activities to improve workers’ health, and to formulate and implement policies, action plans and stimulate intercessional collaborations. More than 50 countries have banned the use of asbestos fibre.
According to the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal in 1992, asbestos has been listed in the category of controlled waste. Although the International Labour Organization Convention on Safety in the use of Asbestos was introduced and signed by 162 countries in 1986, it has only been ratified by 36 countries.
The International Agency for Research on Cancer (IARC) classified hazardous substances in 2006. According to the classification, there are five groups of human carcinogens such as, Group 1 – carcinogenic to humans – 108 agents; Group 2A – probably carcinogenic – 63 agents; Group 2B – possibly carcinogenic – 271 agents, Group 3 – not classifiable – 509 agents; and Group 4 – probably not carcinogenic – one agent. Presently, the IRAC has classified asbestos under Group 1.
The concentration of asbestos fibres in the air, duration of exposure, frequency of exposure and the size of asbestos fibres inhaled are some of the factors that contribute to the seriousness of asbestos-related health hazards (Health Ministry, New Zealand, 2014).
In 1997, blue asbestos was banned in Sri Lanka, but white asbestos has been used mainly for the production of roofing sheets.
Sri Lanka ratified the Rotterdam Convention in 2006 and the government officially announced that the import of asbestos fibre would be reduced by 2018 due to health and environmental risks.
Since the use of asbestos roofing and its production process show many health impacts on the people who involve in the production of asbestos and on the users, it is highly justifiable that Sri Lanka should ban the use of this product and should go for an alternative product to safeguard the future of the country.
The use of asbestos has already been controlled by the government since 2018, hence it is high time to find out an alternative and environmental-friendly product which could be a solution for non-asbestos roofing in Sri Lanka.
A recent study was carried out to:
* find an environmental-friendly alternative fibre material instead of asbestos fibres and
* check the feasibility of selected alternative fibre materials for non-asbestos roofing solution in Sri Lanka.
During the study, asbestos fibre was replaced with alternative cellulose fibre materials found in Sri Lanka. Selected fibre materials were rice husk, paper pulp, coir fibre and coconut charcoal.
These materials are found in abundance in Sri Lanka and are thrown to the environment as waste materials. Fly ash was also selected for the study in order to improve the strength while sand was used as a filler material and Ordinary Portland Cement as a binder.
Test results showed that rice husk can be used as an alternative fibre material for asbestos fibre in the production of roofing sheets as per all tested parameters which complied with both International Organization for Standardization ISO 10904: 2011 and Bureau of Indian Standards IS 14871:2000 standards.
The second option is paper pulp as per the test results of all parameters obtained from both ISO 10904: 2011 and IS 14871: 2000 standards compiled except marginal failure of one sample out of five samples of breaking load test.
