මෙය අසත්යයක් නොවේ. අද අප “පිරිසිදුවට” යැයි සිතා නිවසේ පිළියෙල කර ගන්නා ආහාර පවා නොයෙකුත් රසායනිකයන්ගෙන් අපවිත්රව පවතී. පළිබෝධනාශක, බැර ලෝහ, ආහාර රසකාරක මින් ප්රධාන වේ. ඇතැම් රටවල මෙම තත්වයන් බොහෝ දුරට නීතිමය වශයෙන් පාලනය කර තිබුනද ශ්රී ලංකාවේ තත්වය එතරම් සතුටුදායක නැත. යම් පළිබෝධනාශක වර්ගයක් තහනම් බවට ප්රසිද්ධ කල විගස එය වෙනත් නමකින් නොමැතිනම් ලේබලය රහිතව වෙළඳපොලේ විකුණනු ලබයි. ඇතැම් රසකාරක “දරුවන්ගේ හැසිරීම කෙරෙහි අහිතකර ලෙස බලපායි” යනුවෙන් යුරෝපීය වෙළඳපොළට නිකුත් කරන නිශ්පාදකයින් එවන් කිසිදු දැන්වීමකින් තොරව එම ආහාරයම ශ්රී ලංකාවේ විකුණනු ලබයි. ආහාර වල අඩංගු විය හැකි බැරලෝහ වර්ග සහ ප්රමාණ හුදෙක් පර්යේෂණ මාතෘකා පමණි. KEEP READING “පරිසරයෙන් පිඟානට එන රසායනික දූෂක! (Pollutants served from environment to your plate)”
Going through old newspapers gives a pleasure of sinking yourself in the news of old times. It is a surprise sometimes to see that the old time discoveries have not brought the change where necessary.
In October 2009, a reporter quotes a statement from Former Prime Minister Ratnasiri Wickramanayaka on using sugar cane to produce ethanol and electricity. Citing the use of ethanol in powering vehicles in Brazil he had drawn the need of research to be done on finding the ability of sugar canes in producing ethanol. Also on using the dry pulpy residue left over in sugar production to generate electricity.
Later in 2010, Dr. P.G. Rthnasri, of the Department of Chemical and process Engineering, University of Moratuwa has announced the successful results in testing bio-methane
as a fuel on three-wheelers, made out of bio-degradable resources. It was said that they used the waste generated in students’ canteens and water hyacinth from Bolgoda Lake to form the gas which was then purified to remove CO2 and then stored the compressed gas. However, a similar system is now being used in household cooking purpose.
May 2010, Dr. Sandya Gunawardena, of the Department of Chemical and process Engineering, University of Moratuwa has announced the successful completion of the study on using bio-diesel produced from rubber seed oil by using a three wheeler on test drive. It was said that this oil can be used in any diesel engine to a proportion. Furthermore, the research team have tested using waste cooking oil into bio-diesel which was a pilot project by that time.
In March 2010, it was a full page advertisement, the discovery of petrol made out of waste plastic and polythene by Mr. Ananda Withanage.
It was the plan at that time to provide 43 000 three wheelers with petrol made out of polythene and plastic to run 150 km per day. May be, it would have been the emissions that stopped the implementation of this project.
However, it all definitely brings the question on “why the alternative bio-fuel is not in use?”, which is a topic that worth bringing back on stage….
ඇස්බැස්ටස් යනු ස්වභාවිකව පරිසරයේ, කෙදි මිටි වශයෙන් පවතින තනි කෙදි බවට පත් කල හැකි ඛණිජයකි.මෙම කෙදි තාපයට, ගින්දරට හා රසායනික ද්රව්ය වලට ඔරොත්තු දෙන අතර තාප පරිවාරක වේ. මේ හේතුවෙන් ඇස්බැස්ටස් බොහෝ කර්මාන්ත සදහා යොදා ගනී.
ප්රධාන වශයෙන් ඇස්බැස්ටස් කාණ්ඩ දෙකකි. සර්පන්ටයින් ඇස්බැස්ටස් සහ ඇම්ෆිබෝල් ඇස්බැස්ටස්. කාර්මිකව බොහෝ විට යොදාගනු ලබන්නේ සර්පන්ටයින් ඇස්බැස්ටස් කාණ්ඩයට අයත් ක්රිසොටයිල් ඇස්බැස්ටස්ය.
ක්රිසොටයිල් ඇස්බැස්ටස් හෙවත් සුදු ඇස්බැස්ටස්:
රැලි සහිත කෙදි වේ. මෙය බොහෝ රටවල තහනම් කර ඇති අතර ඇමෙරිකාව හා යුරෝපයේ පමණක් සීමිත අවශ්යතා සදහා යොදා ගනී. බහුල යොදාගැනීම් වන්නේ, පීලි සහිත වහල තහඩු, සිවිලිම් සදහා යොදා ගන්නා පැතලි තහඩු, තිරිංග ආස්තර, පයිප්ප පරිවරණ සහ පොළවට අතුරණ පිගන්ගඩොල් නිශ්පාදනය සදහාය.
ඇමොසයිට් හෙවත් දුඹුරු ඇස්බැස්ටස්
තාප පරිවාරක නිශ්පාදන වල ගිනි මන්දකයක් ලෙස සහ සිවිලිම් තහඩු සදහා යොදාගනු ලබයි.
ක්රොසිඩොලයිට් හෙවත් නිල් ඇස්බැස්ටස්
ඇස්බැස්ටස් බිත්ති තහඩු, ඇස්බැස්ටස් සිදුරු ඇහිරීම සදහා, තාප පරිවාරක ලෙස, මීල් බෝඞ් සදහා යොදාගනු ලැබූ අතර මේ වන විට සම්පුර්නයෙන්ම පාහේ භාවිතයෙන් ඉවත්කර ඇත.
වෙනත් ඇස්බැස්ටස් වර්ග
නීතියෙන් සීමා කරන ලද වෙනත් ඇස්බැස්ටස් වර්ග වන්නේ, ටේරමොලයිට්, ඇක්ටිනොලයිට් සහ ඇන්තොෆිලයිට් ඇස්බැස්ටස් ය. මේවා සීමිත වශයෙන් ගොඩනැගිලි ද්රව්ය වල සහ තාප පරිවාරක ද්රව්ය තුල හමුවේ.
නිවසේ ඇස්බැස්ටස් හමුවිය හැකි ස්ථාන
1. වහල තහඩු
2. අට්ටාලයේ පරිවරණය
3. අසව් සහ ධ්වනි කපරාරු
4. උදුන් පරිවාරක
5. දර ලිප්
6. පොළවට අතුරණ පිගන්ගඩොල්
8. නල පරිවාරක
9. බොයිලේරු පරිවාරක
ඇස්බැස්ටස් හානිකර වන්නේ ඇයි?
ඇස්බැස්ටස් හි හානිකරත්වය සදහා මූලිකව බලපානු ලබන්නේ ආශ්වාස කරන මුළු කෙදි ප්රමානයයි. හානි වන ලද හෝ තුවාල වන ලද ඇස්බැස්ටස් අඩංගු නිශ්පාදන මත හෝ අසල ගැවසීම හේතුවෙන් පරිසරයේ පවතින ඇස්බැස්ටස් කෙදි ප්රමාණයට වඩා සිය ගුණයකින් කෙදි ශරීර ගත විය හැක. මේ නිසාම මෙවන් පුද්ගලයන්ගේ ඇස්බැස්ටස් ආශ්රිත රෝග වැළදීමේ සම්භාවිතාවය ද ඉහලයයි.
ඇස්බැස්ටස් සිරුරට ඇතුලු වන්නේ කෙසේද?
ඇස්බැස්ටස් කෙදිති මගින් අපවිත්රනය වූ වාතය ආඝ්රාණය මගින් සිරුර තුලට ඇස්බැස්ටස් කෙදිති ඇතුලු වේ. විශාල ප්රමාණයේ කෙදිති සිරුරෙන් ඉවත් වුවද ඉතා කුඩා කෙදිති සිරුර තුල රැදෙමින් රෝග ඇතිකරයි.
ආහාර මාර්ගය හරහා ඇතුලු වන ඇස්බැස්ටස් කෙදිති ස්වාභාවිකවම සිරුර තුලින් ඉවත් වන අතරම සම හරහා ඇස්බැස්ටස් කෙදිති අවශෝෂණයක් සිදු නොවේ.
ඇස්බැස්ටෝස් කෙදි ආඝා්රණය නිසා පහත සදහන් මරණීය රෝග ඇතිවිය හැක.
1) පෙනහළු පිලිකා
බොහෝවිට ඇස්බැස්ටස් නිසා ඇතිවන මෙවන් රෝග අවුරුදු 15ත් – 60ත් අතර පුද්ගලයන්ගෙන් ප්රදර්ශනය වන අතර එවැනි රෝග ඇතිවීමේ ප්රවණතාවය,
1)නිරාවරණය වු ඇස්බැස්ටස් කෙදි වර්ගය
2)ආග්රහණය වූ කෙදිති ප්රමාණය
3)නිරාවරණය වූ වාර ගණන
මත තීරණය වේ.
දුම්බීම හා ඇස්බැස්ටස් නිසා ඇතිවන රෝග අතර සම්බන්ධය
අධික ලෙස දුම්පානය කරන පුද්ගලයන්ට ඇස්බැස්ටස්වලට නිරාවරණය වීම නිසා පෙනහළු ආශ්රිත පිලිකා ඇතිවීමේ ප්රවණතාවය ඉහල බව බොහෝ විද්යාත්මක අධ්යනයන්ගෙන් සොයාගෙන ඇත. දුම්බීම සිදුකරන ඇස්බැස්ටස් සේවකයන්ට සාපේක්ෂව දුම්බීම අත් හල ඇස්බැස්ටස් සේවකයන්ට පෙනහළු පිලිකා ඇතිවීමේ ප්රවණතාවය අවම බවට පැහැදිලි සාක්ෂි පවතී.
ඇස්බැස්ටස් තහඩුවලින් රසායනික අපවිත්රනය සිදුවන්නේ ඵහි කෙඳි ගැලවීයාමේදී ය. එය අවශ්ය ප්රමාණය ලබා ගැනීම සඳහා කැපීමේදී, පාසි හා දිය සෙවෙල් ඉවත් කිරීම සඳහා සීරීමේදී, ඇස්බැස්ටස් අඩංගු උපකරණ දිරාපත් වීමේදී, එවන් කසල ගොඩවල් මත සතුන්ගේ ලොම් හා පාද හරහා මෙන්ම දිරා පත්වන ඇස්බැස්ටස් කොටස් තැන තැන දැමීමේදී ගෘහාශ්රිත පරිසරයට ඇස්බැස්ටස් කෙඳි එක් වේ. මේවා ඉතා පහසුවෙන් ආඝ්රාණය විය හැක. තරමක් විශාල කෙඳිති ශ්වසනාලයේ රැඳී ශ්ලේශ්මල සමඟ ඉවත් විය හැකි වුවත් තුනී කෙඳිති පෙනහැල්ලේ තැම්පත් වේ. පර්යේෂණන්ට අනුව මිසොතෙලියොමා රෝගයට හේතු කාරක වන්නේ මයික්රො මීටර 0.1 – 5.0 දක්වා අතර වන ඇස්බැස්ටස් කෙඳිතිය.
- ඇස්බැස්ටස් තහඩු කැපීමේදී ජලයෙන් පොඟවා කපන්නේ නම් නිකුත් වන දූවිලි ප්රමාණය අවම වන අතර ඒවා අශ්වාස වීමද අවම වේ.
- පිරිසිදු කිරීමේදී, සිරීම් නොකල යුතු අතර අව්වෙන් වැස්සෙන් වන ඛාදනය වැළැක්වීමට, තීන්ත තට්ටුවක් ආලේප කළ හැක.
- නිවස/ පාසල ඇතුලතදී නිරාවරණය වීම අවම කිරීමට සිවිලිමක් යෙදීම හෝ තීන්ත ආලේප කිරීම සිදුකළ හැක.
- ඇස්බැස්ටස් තහඩු බැහැර කිරීමේදී, ජාතික මට්ටමේ නිසි ක්රමවේදයක් සැකසෙන තුරු, ඒවා වළ දැමීම වඩා යෝග්ය ක්රමවේදය වේ.
Gathered by: Chalani Rubesinghe
- The heavy metal contamination and their consequences in brief
- Situation in the Negombo lagoon, Sri Lanka
- The requirement of a policy
Heavy metals by definition are the metals that have a density of more than 5g/cm3. There are about 60 heavy metals discovered so far. In trace levels, while some of them have a nutritional value such as Copper, Zinc, Manganese, Nickel, Chromium and Iron. The same can turn toxic in higher concentrations (eg. Copper, Zinc, Manganese) 5, 13. Some like lead, cadmium and mercury can course toxicity even in trace levels of contamination.5
Literature reveals number of studies that have been carried out in Sri Lanka with regard to the heavy metal contamination7-9, 12-14, 16-20. The review on environmental pollution in Sri Lanka summarizes the different paths of heavy metal contamination and their effects on human with reference to several research studies16. The water quality analysis of Sri Lanka revealed the state of pollution in twelve selected water bodies including Kelani River, Kelani estuary, Negombo lagoon, Bolgoda Lake, Koggala lagoon, Kotmale reservoir, Kala wewa and Rajangana tank, Kandy Lake, Meda ela, Hamilton canal and Hikkaduwa marine sanctuary20.
Although studies reveal of certain adverse situations and possibilities of growing such a threat in the Negombo lagoon, there has never been a follow-up on the matter. In 1991, Mercury has been detected in water samples of the lagoon in a level of 20. In 2008 this level of mercury detected in sediments collected from Negombo lagoon was between 0.6- 0.75ppm12. It shows a large increase in the level with respect to only mercury. Therefore the best will be to pay attention on this matter before it reaches the toxic levels to human and create another case like “Minamata disease” in Japan. This report thereby will be an effort on dragging the attention of relevant parties on one of the largest water bodies in Sri Lanka with a threat of human contamination through fish consumption.
The heavy metal contamination and their consequences in brief
The heavy metal contamination has been a problem for human since the time of civilization; history suggests that lead poisoning must have affected the collision of the Rome Empire1. The case of Minamata disease in Japan which produced nearly 10 000 victims of mercury poisoning2, the incident of Love canal in America3 and furthermore Bhopal: the Union Carbide gas leak, Chernobyl: Russian nuclear power plant explosion, Seveso: Italian dioxin crisis. The 1952 London smog disaster, Major oil spills of the 20th and 21st century, The Baia Mare cyanide spill, The European BSE crisis, Spanish waste water spill and The Three Mile Island near nuclear disaster are famous cases of tragic ends of heavy metal contamination coursed by anthropogenic environmental pollution3.
In talking about the disasters, it will be worth to aware on effects of heavy metals on human body. The table 1 indicates the toxicity of few heavy metals and their consequences with the level of exposure.
In addition various small-scale studies are continuously monitoring the heavy metal contamination in water bodies, soil and sediments6, air and food items.
Table 1: Most Commonly Encountered Metals and Their Toxicity4
cancer: lung, bladder, skin, encephalopathy
≥50 µg/L urine, or
100 µg/g creatinine
|Bismuth||Renal failure; acute tubular necrosis||Diffuse myoclonic encephalopathy||No clear reference standard|
|Cadmium||Pneumonitis (oxide fumes)||Proteinuria, lung cancer, osteomalacia||Proteinuria and/or ≥15 µg/ g creatinine|
|Chromium||GI hemorrhage, hemolysis, acute renal failure (Cr6+ ingestion)||Pulmonary fibrosis, lung cancer (inhalation)||No clear reference standard|
|Cobalt||Beer drinker’s (dilated) cardiomyopathy||Pneumoconiosis (inhaled); goiter||Normal excretion:
0.1-1.2 µg/L (serum)
|Copper||Blue vomitus, GI irritation/ hemorrhage, hemolysis, MODS (ingested); MFF (inhaled)||vineyard sprayer’s lung (inhaled); Wilson disease (hepatic and basal ganglia degeneration)||Normal excretion:
25 µg/24 h (urine)
|Iron||Vomiting, GI hemorrhage, cardiac depression, metabolic acidosis||Hepatic cirrhosis||Nontoxic: < 300 µg/dL Severe: >500 µg/dL|
|Lead||Nausea, vomiting, encephalopathy (headache, seizures, ataxia, obtundation)||Encephalopathy, anemia, abdominal pain, nephropathy, foot-drop/ wrist-drop||Pediatric: symptoms or [Pb] ≥45 µ/dL (blood); Adult: symptoms or [Pb] ≥70 µ/dL|
|Manganese||MFF (inhaled)||Parkinson-like syndrome,
|No clear reference standard|
|Mercury||Elemental (inhaled): fever, vomiting, diarrhea, ALI;
Inorganic salts (ingestion): caustic gastroenteritis
|Nausea, metallic taste, gingivo-stomatitis, tremor, neurasthenia, nephrotic syndrome; hypersensitivity (Pink disease)||Background exposure “normal” limits:
10 µg/L (whole blood); 20 µg/L (24-h urine)
|Nickel||Dermatitis; nickel carbonyl: myocarditis, ALI, encephalopathy||Occupational (inhaled): pulmonary fibrosis, reduced sperm count, nasopharyngeal tumors||Excessive exposure:
≥8 µg/L (blood)
≥500 µg/L (8-h urine)
|Selenium||Caustic burns, pneumonitis, hypotension||Brittle hair and nails, red skin, paresthesia, hemiplegia||Mild toxicity: [Se] >1mg/L (serum); Serious: >2 mg/L|
|Silver||Very high doses: hemorrhage, bone marrow suppression, pulmonary edema, hepatorenal necrosis||Argyria: blue-grey discoloration of skin, nails, mucosae||Asymptomatic workers have meant [Ag] of 11 µg/L (serum) and 2.6 µg/L (spot urine)|
|Thallium||Early: Vomiting, diarrhea, painful neuropathy, coma, autonomic instability, MODS||Late findings: Alopecia, Mees lines, residual neurologic symptoms||Toxic: >3 µg/L (blood)|
|Zinc||MFF (oxide fumes); vomiting, diarrhea, abdominal pain (ingestion)||Copper deficiency: anemia, neurologic degeneration, osteoporosis||Normal range:
0.6-1.1 mg/L (plasma)
10-14 mg/L (red cells)
Situation in the Negombo lagoon, Sri Lanka
Negombo lagoon is one of the largest lagoon environment located in the western Sri Lanka. With an area nearly 3 164 ha (31.64 km²) this lagoon supports vast number of fishing families20.
The literature reveals on the contamination with regard to several heavy metals in the area. Being the receiver of several freshwater bodies that pass through the industrial zones like Dandugam oya, Ja-Ela, Hamilton canal and the Dutch canal, this lagoon collects a large sum of pollutants.
Table 2: Metal levels recorded by Indrajith et al., 2008 and GCEC ,1991 for Negombo lagoon
The people living around the lagoon are mostly fishermen and their families, which are engaged in fishing activities. It was found that their unawareness on hazardous chemicals expose them to various harmful chemicals. The best example was that they throw used CFL and fluorescent bulbs in to the lagoon. On one hand this is dangerous for fishermen who operate brush piles that often walk in the lagoon and also are harmful in the sense of mercury contamination.
It was revealed that often fishermen find fish from large to small-sized, with melting muscles. Some dead and some alive. Sometimes the cooked fish smells crude oil and the curry appears with oil layer on top, even when they were cooked without gills or gut content. According to the explanation of Dr. Krishnarajah, a senior lecturer in zoology, Open University of Sri Lanka, this is due to accumulation of sulfur in the adipose tissues of fish. A simple solution can be engaged such as, first boil the fish, throw out that water and then cook the meat. Still this may not remove the heavy metals accumulated in the fish. Therefore these issues should be given attention before the fish from Negombo lagoon being rejected.
For these people have been associated with lagoon fishery and eating fish for years they may not change the habit of eating fish. Thus the best solution lies in the site recovery. Either scientific research should focus on removal of heavy metals in water bodies including sediments or on proper mechanism of removing heavy metals from fish muscles as parts like liver and gills are often removed when cooked. The science community should get together in bringing out and implementation of solutions. Purification mechanisms, possible cleaning techniques for surrounding pollutant sources, promoting natural cleaners will be the best solutions to save people from the possible threats of not only mercury but also other pollution sources as well.
Figure 1: Levels of selected heavy metals detected in Etroplus suratensis
According to table 2, it is seen that even though the levels of metals are significantly law in water, the detected levels in fish (Figure 1) are higher. This is due to the bio accumulation. The metals are gradually deposited in body tissues of fish. Further it shows that fish liver accumulates the highest amount of metals than gills or muscles. Similar situation can be observed in Ambassis commersoni (Katilla) in figure 2. All these metals are transferred to the predator fish and accumulated in higher amounts. The human being at the top of the food chain accumulates and suffocates from all these chemicals.
Figure 2: Levels of selected heavy metals detected in Ambassis commersoni
Experiments of all kind prove that lagoon is contaminated. It was recorded That Koraliya or Etroplus suratensis in Negombo lagoon can contain 0.1 mgkg-1 of fish consumed only the muscle part12. In 2000, the US National Research council established a “reference doses of 1000 micro grams per kilogram of hair”21. Families of the fishermen are the regular consumers of fish. Often they consume all three meals throughout the week except on Sundays. Unlike the people around the country, who consumes mostly marine or lake fish from different parts of the country, these families consume fish that are seasonally abundant in the lagoon that caught by the fishermen. For a person who consumes all meals of fish supposing he consumes only Korali even if he eats 100g per meal he consumes nearly 2kg per week thus ingest nearly 0.2mg/kg-1 of Hg. This way it will not take 5 weeks for a person to ingest 1.0mg/kg-1 of mercury into his body. Even if we consider the meals of consumption to half the value per week, it will only take 2.5 months for a person to ingest this amount of mercury which has no value as nutrition inside the body. Yet harms the nerves system of the fetus in a pregnant women and an ordinary human21.
While one part of the country is being attacked by heavy metal contamination (probably due to pesticide contamination) the others can be affected from fish contamination. This raises the question whether we are waiting till we recover another critical situation like CKDue (Chronicle Kidney Disease due to unknown ethical) to take an action on fish in the Negombo lagoon.
In addition to the pollution of water bodies by pesticides, it was found that broken pesticides bottles are used in bakery fireplaces which are a possible method of contamination of bakery items with vaporizing chemicals.
Once released to the environment, not only the water but also the sediments can be contaminated. This sediment then passes through the fish to human mostly initiating from grazers and bottom feeders. Human consumption of these fish ingests a certain amount and consumption of predatory fish multiplies the amount of any heavy metal or pollutant contaminated on these fish.
In Sri Lanka, though there are studies carried out by various scientists on heavy metal contamination and their consequences, they do not communicate to the general public. Thus the people around lagoon are unaware of the threat they are vulnerable to.
CEJ (Center for Environmental Justice) in their conversations with general public in the area has found that the community around the lagoon is totally unaware of heavy metal contamination.
“I am the first fishermen in this area; I see that the lagoon is now polluted by the effluents from garments and hotels but we cannot change the habit of eating fish” Juwan seeya of Thalahena, Negombo.
“I have often observed fish with melting muscles, they are small to large fish floating dead and sometimes it’s a pain to see them swimming with a side of the fish being melted” Berty Perera of Pitipana, Negombo.
“All the gutters are opened to the lagoon, even when government supplies the septic tanks, people do not bother to fix them. All the factories that repair engines release effluent water to the lagoon” Marcus Anthony, Pitipana south, Negombo.
Though they know the lagoon is polluted by effluents of garments, factories and the boats operated in the lagoon, it is not enough knowledge for them to take any action on that. Though they are aware of that oil has been washed to the lagoon thus cooked fish taste oil, the bulbs been thrown away could cause damage to fishermen, they are not bothered to act on these matters. According to all the research data, these people are exposed to the heavy metal contamination through fish and all its consequences.
The requirement of a policy
In the words of a Negombo lagoon vicinity resident, Ramesh Keerithisinghe of Dalupotha, Negombo;
“As I believe the rules and regulations have not been complied by any of the fishing boats that go to catch fish. In fact they dispose all their oily residues plus plastic and other garbage directly over the side. This consequently pollutes the water in the lagoon and the fish get poisoned. Other than the prescribed scenario, lot of untreated gutters have been directed to the lagoon as anybody who walks pass can witness all of them goes into the water. So my suggestions are to;
- Implement the current rules to practice, which would avoid the damage made by the fishing boats, trawlers etc.
- The gutters must be reroute through treatment plants prior to discharge into the water, so authorities should wake up and take strict action against those who violate the rules.
If above two points will be addressed most of the detriment and future disaster could be avoided”.
Thus, in order to prevent possibilities of a future tragedy the policy level attention is required in the fields of;
- Monitoring the standards of fishing vassals operated and it’s effluents to the lagoon.
- Pre-treatment to oil contaminated water/ ballast water should made compulsory.
- All the effluent systems to the canals should be monitored and shall fined
- Authorities shall be forced to take immediate actions on cleaning up the lagoon and implementing a proper and practical waste management system in the lagoon area.
- Lead poisoning and Rome, [Online] Available from: http://penelope.uchicago.edu/~grout/encyclopaedia_romana/wine/leadpoisoning.html [Accessed: 13.05.2012]
- Allchin, D. ‘The Poisoning of Minamata’.[Online] Available from: http://www1.umn.edu/ships/ethics/minamata.htm [Accessed: 13.05.2012]
- Enzler, S.M., Environmental disasters, 2006. [Online]Available from: http://www.lenntech.com/environmental-disasters.htm#6._The_Love_Canal_chemical_waste_dump [Accessed: 13.05.2012]
- Soghoian, S. and Sinert, R.H., Heavy metal toxicity. [Online] Available from: http://emedicine.medscape.com/article/814960-overview [Accessed: 13.05.2012]
- Heavy metals, 1996.[Online] Available from: http://www.caobisco.com/doc_uploads/nutritional_factsheets/metals.pdf [Accessed: 13.05.2012]
- Obasohan, E.E. ‘Heavy metals in the sediments of Ibekuma stream in Ekpoma, Edo state, Nigeria’. African journal of general agriculture, 4, (2), 2008, pp. 107-112.
- Ratnayaka, I. et al. ‘Tolerance level of heavy metals by gram positive soil bacteria’. World academy of science, engineering and technology,53, 2009, pp. 1185-1189.
- Premarathna, H M P L, Indraratne, S P & Hettiarachchi, G ‘Heavy metal concentration in crops and soils collected from intensively cultivated areas of Sri Lanka’. Proceedings of the world congress of soil science, soil solutionsfor a changing world. 19th, 2010, pp. 122-124.
- Senarathne, P & Pathiratne K A S, ‘Accumulation of heavy metals in a food fish, Mystus gulio inhabiting Bolgoda Lake, Sri Lanka’, Sri Lanka J. Aquat. Sci. 12, 2007, pp. 61-75.
- Environmental health impacts from exposure to metals, Repoprt of a joint interregional workshop, 2005, pp. 6-32.
- Järup L, ‘Hazards of heavy metal contamination’. Br Med Bull, 68, 2003, pp. 167-82 [Online] Available from http://www.ncbi.nlm.nih.gov/pubmed/14757716 [Accessed: 11.05.2012]
- Indrajith, H A P, Pathiratne K A S & Pathirathne A, ‘Heavy metal levels in two selected fish species from Negombo estuary, Sri Lanka: relationship with body size’. Sri Lanka J. Aquat. Sci. 13, 2008, pp. 63-81.
- Silva E I L & Shimizu, A, ‘Concentrations of trace metals in the flesh of nine fish species found in a hydropower reservoir in Sri Lanka’. Asian fisheries science, 17, 2004, pp. 377-384.
- The study of the management of ground water resources of Sri Lanka: Sustainable groundwater management in Asian cities. [Online] Available from: http://enviroscope.iges.or.jp/modules/envirolib/upload/981/attach/08_chapter3-5srilanka.pdf [Accessed: 11.05.2012]
- O’Rourke, D and Connolly, S ‘Just oil? The distribution of environmental and social impacts of oil production and consumption’. rev. Environ. Resource., 28, 2003, pp. 587-617 [Online] Available from: http://enviroscope.iges.or.jp/modules/envirolib/upload/981/attach/08_chapter3-5srilanka.pdf [Accessed: 11.05.2012]
- Illepperuma, O ‘Environmental pollution in Sri Lanka: a review’. J. Natn. Sci. foundation Sri Lanka, 28, (4), 2000, pp. 301-325.
- Jinadasa, B et al. ‘Determination of mercury, cadmium and Lead levels of selected fish species in the local market, Sri Lanka’. Proceeding of the SLAFAR annual scientific session, 2010, pp. 17.
- Mercury levels in Sperm whale (Physeter macrocephalus) skin biopsis collected from around the globe during the voyage of the Odysse. Available at: http://www.oceanalliance.org/dfss/sermwhale_research.pdf [Accessed: 19.04.2012]
- Senarathne, A and Dissanayake, C ‘The geochemistry of mercury in some coastal sediments from Sri Lanka’. Chemical geology, 75, (3), 1989, pp. 183-190.
- Silva, E I L Water quality of Sri Lanka: a review on twelve water bodies. Dehiwala: A.J. Prints, 1996, pp. 205-242.
Author: Chalani Rubesinghe.
The toxicity of asbestos is well-known, and as such its use has been banned in more than 40 countries. Yet Sri Lanka is behind in this process.
Asbestos is still used in many construction materials and automobiles. People exposed include workers who are engaged in asbestos related industries or in its transportation or its handling at sales outlets and the many citizens who spend the entirety or just part of their lives under asbestos roofs. Health threats from exposure to asbestos include mesothelioma, asbestosis, lung cancer, gastrointestinal tract cancers, diffuse pleural thickening and warts or corns in the skin. Health effects generally appear after 15 years or more from the first exposure and interestingly, keep progressing even when exposure is stopped.
Although Sri Lanka has the legal backing to ban the use of asbestos, more policy actions are necessary for its proper management and for banning or phasing out its use. It should not be difficult to find asbestos alternatives and treating mechanisms. Indeed, examples of these are already available from many parts of the globe.
- Applications of asbestos
- Contamination Situation in Sri Lanka
- Exposure studies from other countries
- Health effects
- Reducing the threat of Asbestos
- Getting tested
- Status of asbestos use, in Sri Lanka
- Legal status of Asbestos in Sri Lanka
- Issues to be addressed immediately
- Policy recommendations
In Sri Lanka, asbestos has only recently been recognized as a toxic substance to which the general public are exposed. Yet its hazardousness has remains the same for humans throughout the world.
The dangers of Asbestos came to the fore following the discovery of its link to mesothelioma, a type of cancer, in persons exposed to asbestos over an extensive period of time. Since then more than 40 countries, including all member states of the European Union, have banned or phased out the use of all forms of asbestos. Yet in Sri Lanka this is a hidden toxin which rarely gets the attention it requires.
Asbestos is a mineral that occurs naturally and has several forms, namely; chrysotite, Amosite, Crocidolite, tremolite asbestos, actinolite asbestos, and anthophyllite asbestos. It is the strength, heat and chemical resistivity of asbestos fibers make it appear to be an ideal material for use in number of products.
Applications of asbestos
Asbestos is generally found in: asbestos gaskets, cigarette filters, fire proofing & prevention materials, plastics, vinyl products, asbestos sheets, electrical cloth & electrical panel partition, fume hoods & laboratory hoods, textile cloths & garments, construction products, adhesives and Gold Bond adhesives, ductwork connectors & flexible duct connectors, insulation, construction mastic & gunning mix, floor backing, drywall taping compounds and zonolite insulation
Contamination- Situation in Sri Lanka
Contamination of Asbestos mainly occurs through inhalation and ingestion.
In Sri Lanka, asbestos is mainly used in roofing and ceilings. An asbestos sheet is not a harmful material as long as it remains on a roof in a good condition. However, it is common practice among carpenters in Sri Lanka to cut the asbestos sheets to the required size. During this process, massive amounts of asbestos dust are generated. It is this dust which can then cause serious health problems.
Once released, the dust is inhaled in large quantities by workers without protective gear. In addition, through their clothes and on other equipment, they become carriers of this toxic dust. Where they transport it to their homes, their children and other family members are then also exposed.
The release of asbestos ‘fibres’ does not just occur during cutting; dust is also released when mosses are scraped from roofing sheets and during the natural decay of asbestos, in sheets or in asbestos containing materials, which are often carelessly dumped.
Careless dumping and transport are major contamination pathways. Even among the factory workers, the majority do not wear any protective gear during their work. It is quite surprising that they do not get traced of being one amongst majority recorded with the cancer diseases.
From childhood to adulthood, most of Sri Lankans spend the time beneath asbestos roofs; most of the schools use asbestos roofing sheets or have asbestos ceilings. These could be damaged and decaying which expose fibers to the environment. Yet there is no measure to see the exposure levels.
Since children enjoy playing in the dirt, they are more vulnerable to asbestos exposure, if the dirt they are playing contains asbestos, they inhale the dust and may also ingest while taking food with their dirty hands. In the Sri Lankan situation, especially as asbestos sheets are freely dumped in the backyard and children like to observe their world around.
House trained cats and dogs can also bring asbestos into the home by carrying dust or dirt on their fur or feet if they spend time in places that have high levels of asbestos in the soil.
There are no proper records on cancer patients in Sri Lanka, which is a major missing in proving the threat of these contaminants in the environment. Information on health effects of Asbestos given by Agency for Toxic Substances and Disease Registry (ASTDR) concludes that there’s a strong relationship between respiratory cancers (cancers of the lung and mesothelioma) and exposure to asbestos in human. Whereas the Statistics available in Sri Lanka (in 2007) points out that, out of 10725 new patients registered during the year 2007, 7200 patients were identified as malignant. Among whom the top three malignancies in males (3204 patients) were carcinoma of bronchus, lung, oesophagus and prostate. It’s only having not tested whether this is exactly due to asbestos, which has no meaning when it gets to the malignant stage.
Since asbestos are mainly used in building components, carpenters, building maintenance, repair and demolition workers are mostly exposed to high levels of asbestos fibers. In Sri Lanka people engaged in solid waste removal and management and workers engaged in Asbestos transportation and handling at sales outlets are also exposed to asbestos dust.
According to the European Directive of the EC 2003/18, permissible limits are 0.1 [f/mL] for all types of asbestos, based on an 8-hour time-weighted average (8h-TWA). The same limit is in force in most Canadian provinces (Alberta, British Columbia, Manitoba, Ontario, Newfoundland and Labrador, Prince Edward Island, New Brunswick and Nova Scotia); New Zealand; Norway; and, the USA. Other countries have permissible limits of up to 2 fibres/cm3.
For some luck, Sri Lanka does not have asbestos mines. All the manufactures use asbestos imported from other countries. That reduces the sources of exposure to asbestos products and their dumping sites.
Exposure studies from other countries
A study conducted by Agency for Toxic Substances and Disease Registry (ATSDR, 2000), shows that the measured asbestos concentration in indoor air of homes, schools and other buildings ranged between 30- 6000 fibers/ m3. This variation depended on whether the asbestos-containing material is in good condition or deteriorating and the type of application such as insulation, ceiling and floor tiles.
Despite the total ban of asbestos, about 1500 workers (mainly construction workers and auto mechanics) were reported as having exposure to asbestos on the Finnish Register of Workers exposed to Carcinogens (ASA Register) in 2006.
In 2004, approximately 61000 workers performing demolition and reconstruction work in Germany were registered in the Central Registration Agency for Employees Exposed to Asbestos Dust.
According to a study on Swedish asbestos cement workers, the highest exposure levels of asbestos concentrations were identified in the milling and grinding operations.
A Finnish study shows that during break repair of trucks or buses, the estimated 8-hour time-weighted average exposure to asbestos was 0.1–0.2 [f/mL], while high levels of exposure (range, 0.3–125 [f/mL]; mean, 56 [f/mL]) were observed during brake maintenance if local exhaust ventilation was not used. Other operations such as cleaning of brakes with a brush, wet cloth or compressed air jet without local exhaust, the concentration exceeded 1 [f/mL] .
In United Kingdom, the high risk jobs on Asbestos contamination has included school teachers. According to the health statistics published by the HSE (Health and Safety Executive, UK), deaths from mesothelioma, continue to increase in the UK (from 153 in 1968 to 2,347 in 2010).
The study carried out by Michael Lee, one of the founder members of the Asbestos in Schools Group (AiS), showed that the numbers of school teachers dying of mesothelioma is on the increase. In figures, 17 school teachers and 3 teaching and educational support assistants died of mesothelioma in 2011. This compares with an average of 13 school teachers a year between 2001 and 2005, and 15 between 2006 and 2010. Researchers in the US points out that for every death of a teacher from asbestos related diseases, 9 children will die. In June 2013 the Government’s advisory committee on cancer concluded that children are more at risk from exposure to asbestos than adults, being more vulnerable because they have longer than adults to develop work related diseases related to the material.
According to the World Health Organization, about 125 million people in the world exposed to asbestos at the workplace. Global estimates show that at least 90 000 people die each year from Asbestos related lung cancer, mesothelioma and asbestosis resulting from occupational exposure.
Asbestos fibers enter the body when a person breathes in. The body can get rid of the large fibers but microscopic fibers can pass in to the lungs causing diseases. The body can naturally get rid of any asbestos fibers entering through the mouth and asbestos fibers cannot be absorbed through the skin.
The monograph published by the International Agency for Research on Cancer (IARC), gives important information on relationship of asbestos on cancer. Breathing Asbestos fibers can lead people to develop;
- Asbestosis – an irreversible scarring of the lungs that causes a decrease in elasticity. An industrial disease that was associated with past high levels of exposure of all types of asbestos.
- Lung cancer – increased incidence in those working with chrysotile, amosite, anthophyllite, and with mixed fibers containing crocidolite, and tremolite.
- Mesothelioma – cancer of the lining of the chest or abdominal wall. Pleural and peritoneal mesotheliomas were reported to be associated with occupational exposures to crocidolite, amosite, and chrysotile. mesothelioma may also occur among individuals living in neighborhoods of asbestos factories and crocidolite mines, and in persons living with asbestos workers.
- Diffuse pleural thickening – a non-malignant disease affecting the lung lining
- Gastrointestinal tract cancers these were reported to have been demonstrated in groups occupational exposed to amosite, chrysotile or mixed fibres containing chrysotile.
Long and thin fibers retain in the lung longer. They are comparatively more toxic than short and wide fibers as these fibers reach the lung and pleura. Fibers of amphibole asbestos such as tremolite asbestos, actinolite asbestos, and crocidolite asbestos are retained longer in the lower respiratory tract than chrysotile fibers of similar dimension.
Information on the health effects of asbestos in people comes mostly from studies of people who were exposed in the past, to levels of asbestos fibers (greater than or equal to 5 μm in length) in workplace air that were as high as 5 million fibers/m3 (5 fibers/mL). The effects of asbestos in workers generally show after 15 years or more after the first exposure to asbestos.
The effect or the disease can increase with factors such as;
- The type of the asbestos fibers that they are exposed to
- The amount of fibers they inhale
- The number of times they are exposed
- The duration of time they exposed to
Health effects of asbestos in contact with skin reveal the formation of small “warts” or corns. The example comes from a group of workers installing amosite insulation in ships; nearly 60% of the people had one or more of these lesions, mostly on the hands (Alden and Howell 1944).
Reducing the threat of Asbestos
- Be aware of the source of exposure
- Regular hand and face washing to remove asbestos-containing dusts and soil, especially before meals, can lower the possibility of asbestos fibers on the skin being accidentally swallowed while eating.
- Door mats can help lower the amount of soil that is tracked into the home; removing your shoes before entering will also help.
- Planting grass and shrubs over bare soil areas in the yard can lower the contact that children and pets may have with soil and reduce the tracking of soil into the home.
- If you are working related to any of the activities that are likely to contaminate your cloths with asbestos fibers, such as carpentry, demolition or maintenance of asbestos containing buildings, automobile repair and servicing, etc. showering or changing cloths before leaving work helps preventing toxic dust contamination in
As long as consumers are considered, any person who has any other material than asbestos, on their roof is strictly advised not to change. Those who have asbestos on their roofing, are advised not to scratch or cut dry asbestos sheets and have a coating paint on top of the Asbestos sheet and a ceiling of any other material to prevent exposure.
- A Chest x-ray.
The x-ray can detect early signs of lung disease caused by asbestos. While other substances besides asbestos can sometimes produce similar changes in the lungs, this test is usually reliable for detecting asbestos-related effects produced by long-term exposures at relatively high concentrations of asbestos fibers.
- Gallium-67 lung scanning – to detect changes in the lung
- High-resolution computed tomography- detects changes in the lungs.
- Detection of microscopic asbestos fibers in pieces of lung tissue removed by surgery.
- Asbestos fibers detected in material rinsed out of the lung, mucus (sputum), urine, or feces. – but these tests are not reliable to estimate how much asbestos a person have been exposed to or to predict whether a person is likely to suffer any health effects.
Status of asbestos use, in Sri Lanka
Sri Lanka does not mine asbestos. 100% of asbestos are imported from different countries. They are used in roofing sheets, chemical insulation, Asbestos containing materials in machinery and in automobile components such as; break shoes, brake pads and clutch pads.
The safety measures and practices among workers engaged in manufacturing, transportation, building constructions, demolition and discarding are almost none. Asbestos are commonly found discarded in backyards and also used in simple garden decorations open for degradation.
Legal status of Asbestos in Sri Lanka
Sri Lanka ratified the Rotterdam convention since 19th January 2006, The Ministry of Agriculture being the national focal point and the Central Environmental Authority being the competent Authority in managing industrial chemicals. Main objective of this convention is to protect human health and the environment by sharing information on certain hazardous chemicals among parties and prior informed consent in international trade of chemicals (PIC).
Blue asbestos was banned in Sri Lanka since 1987, under the gazette Extraordinary No. 452/4, published on 6th May 1987 and only Chrysotile is used.
According to the Central Environmental Authority, a situation report and a policy recommendation report has been prepared while the preparation of a National Policy on usage of Asbestos related products is in process. In addition, several discussions have been carried out with all the stakeholders regarding the elimination of Asbestos related diseases in Sri Lanka.
After a meeting of Technical advisory committee for the management of Industrial Chemicals (TACMIC) in 2012, decisions were made to find out the possibilities of granting tax concessions for health and environment friendly non Asbestos products, awareness raising among public on health impacts of Asbestos products and also on the available alternatives including ceiling sheets and to restrict the approval for new Asbestos related industries and expansion for such existing industries.
Following, the Ministry of Environment and the Ministry of Health has submitted a joint cabinet paper to the cabinet and was granted the approval on 5th July 2012. The cabinet decisions included;
- To update the national database on Chemicals
- To identify priorities in management of carcinogenic chemicals in factories with the help of World Health Organization
- To minimize the effects of the carcinogenic chemicals in factories and
- To carry out a national program on carcinogenic chemicals.
Importation of asbestos:
Interestingly, the records of importation extracted from “External trade statistics” by Sri Lanka Customs shows the imported amounts of asbestos including blue asbestos. (Table 1) thus it is seen that regulations on paper does not ensure the safety in practical situation.
Table 1: Importation details from 2005 to 2008 for asbestos coming under the HS Code 2524….
|In year 2005|
|25240009 – Other|
|In year 2006|
|25240009 – Other|
|In year 2007|
|25240001 – Blue Asbestos|
|25240009 – Other|
|252410 – Crocidolite|
|252490 – Other|
|In year 2008|
Issues to be addressed immediately
Since the effects of asbestos contamination remains similar throughout the world, immediate steps should be taken to protect workers from extensive exposure while introducing a proper mechanism for disposal of Asbestos discarded from households, maintenance, production and demolition activities.
Since these items falls under hazardous waste, people should be made aware and effective mechanism should be introduced before these toxics are found in lungs.
- Policy should be brought up to manage the existing asbestos in use and also to introduce and popularize asbestos alternatives, if possible through the existing asbestos producing companies.
- Form regulations to prevent or reduce the exposure to asbestos,
- Form arrangements to deal with accidents, incidents and emergencies,
- Form regulations to prevent or reduce the spread of asbestos and safe removal.
A procedure has been suggested by the EU-Asia Project on sustainable Constructional waste management in Sri Lanka. This indicated procedure for Asbestos removal according to a technology developed by the Technology Regency International Group (UK) on Asbestos conversion. The main process steps of this includes; Loading, Shredding, Chemical bath (de-watering), Furnace (the rest of the moisture removing), Rotary kiln (1200 degrees, one hour), Ejecting and finally sealing.
Methods and mechanism are available in other countries on safe removal of Asbestos according to the contamination levels in the air.
For man has discovered worse chemicals first and the safer ones second, alternatives are now available for asbestos. (Table 2)
Table 2: Alternatives for asbestos products
|Asbestos Product||Substitute Products|
|Fiber-cement roofing using: synthetic fibers (polyvinyl alcohol, polypropylene) and vegetable/cellulose fibers (softwood Kraft pulp, bamboo, sisal, coir, rattan shavings and tobacco stalks, etc.); with optional silica fume, fly ash, or rice husk ash
Micro-concrete (Parry) tiles
Galvanized metal sheets
Vegetable fibers in asphalt
Coated metal tiles (Harveytile)
Aluminum roof tiles (Dekra Tile)
Extruded uPVC roofing sheets
Recycled polypropylene and high-density polyethylene and crushed stone (Worldroof)
Plastic coated aluminum
Plastic coated galvanized steel.
|Asbestos-Cement Flat Sheet (ceilings, facades, partitions)||Fiber-cement using vegetable/cellulose fibers (see above), wastepaper, optionally synthetic fibers
Gypsum ceiling boards (BHP Gypsum)
Polystyrene ceilings, cornices, and partitions
Façade applications in polystyrene structural walls (coated with plaster)
Aluminum cladding (Alucabond)
Galvanized frame with plaster-board or calcium silicate board facing
Softwood frame with plasterboard or calcium silicate board facing.
|Asbestos-Cement Pipe||High Pressure:
Cast iron and ductile iron pipe
High-density polyethylene pipe
Polyvinyl chloride pipe
Steel-reinforced concrete pipe (large sizes)
Glass-reinforced polyester pipeLow Pressure:
Cellulose/PVA fiber-cement pipe
Glass-reinforced polyester pipe
Steel-reinforced concrete pipe (large diameter drainage)
|Asbestos-Cement Water Storage Tanks||Cellulose-cement
|Asbestos-Cement Rainwater Gutters; Open Drains (Mining Industry)||Galvanized iron
There is no debate on the toxicity of Asbestos. May it not been proved for Sri Lankans. It is just few decisions of policy makers that will be required to bring the change, including, replacement of the Asbestos fibers with an alternative. As for the general public the best option is to be aware and take measures at every step to prevent contamination of the toxic material/s.
- http://www.asbestos.com/products/ (Accessed 26 February 2014)
- http://www.atsdr.cdc.gov/asbestos/asbestos/health_effects/, Asbestos, Health Effects, ASTDR. (Accessed 31 January, 2014)
- http://www.ncisl.lk/statistic.php , statistics of National Cancer Institute. (Accessed 31 January, 2014)
- EU (2003). Directive 2003/18/EC of the European Parliament and of the Council of 27 March 2003 amending Council Directive 83/477/EEC on the protection of workers from the risks related to exposure to asbestos at work. Official Journal L 097, 15/04/2003 P.0048 – 0052.
- ACGIH (2007). Documentation of the TLVs and BEIs with Other Worldwide Occupational Exposure Values – 2007, Cincinnati, OH [CD-ROM].
- Saalo A, Länsimäki E, Heikkilä M, Kauppinen T (2006). ASA 2006. Syöpäsairauden vaaraa aiheuttaville aineille ja menetelmille ammatissaan altistuneiksi ilmoitetut Suomessa. (In Finnish)
- Hagemeyer O, Otten H, Kraus T (2006). Asbestos consumption, asbestos exposure and asbestos-related occupational diseases in Germany. Int Arch Occup Environ Health, 79: 613–620. doi:10.1007/s00420-006-0091-x PMID:16523318
- Albin M, Jakobsson K, Attewell R et al. (1990). Mortality and cancer morbidity in cohorts of asbestos cement workers and referents. Br J Ind Med, 47: 602–610. PMID:2207031
- Kauppinen T & Korhonen K (1987). Exposure to asbestos during brake maintenance of automotive vehicles by different methods. Am Ind Hyg Assoc J, 48: 499–504.PMID:3591672
- Elimination of Asbestos related diseases, (2006), World Health Organization.
- http://www.atsdr.cdc.gov/asbestos/asbestos/health_effects/ (Accessed 5 March 2014)
- Alden HS, Howell WM. 1944. The asbestos corn. Archives of Dermatology and Syphilology 49:312-314.
- www.atsdr.cdc.gov/toxprofiles/tp61-p.pdf (Accessed 5 March 2014)
- https://www.safework.sa.gov.au/…/How_to_Safely_Remove_Asbestos.pdf , (December 2011) by Safe Work Australia
- cowam.tec-hh.net/COWAM-presentation-PVC,asbestos.pdf, PVC and Asbestos waste management in Sri Lanka, EU-Asia Project on sustainable Constructional waste management.
- Substitutes for Asbestos-Cement Construction Products, by Barry Castleman Updated October 8, 2009 (Accessed on 20/ 02/ 2014)
- http://info.mayiclaim.co.uk/personal_injury_compensation_claim_news/bid/331511/Children-are-More-at-Risk-from-Asbestos-than-Teachers-in-Schools, “Children are More at Risk from Asbestos than Teachers in Schools” by Tony Wheeler on Thu, Jan 09, 2014.
-  Substitutes for Asbestos-Cement Construction Products, by Barry Castleman Updated October 8, 2009 (Accessed on 20/ 02/ 2014)