Asbestos and its effect on human health

Asbestos and Its Effect on Human Health Ryan Ubelhor February 10, 2006 What is Asbestos? Asbestos is a generic term applied to a variety of naturally formed hydrated silicates containing metal cations such as sodium, magnesium, calcium or iron It is versatile, plentiful and ideal as a fire-proofing and insulation material But it can be harmful as well The three main types of asbestos that have been used commercially are: Crocidolite (blue) Amosite (brown) Chrysotile (white) Common Commercial Uses Brown and blue were used in many products until the early 1980s The use of all types of asbestos in the amphibole group was banned in the mid-1980s These products were mainly asbestos cement sheets and pipes for construction, casing for water and electrical/telecommunication services thermal and chemical insulation (i.e., fire rated doors, and gaskets) In the United States, chrysotile has been the most commonly used type of asbestos It has been used in many materials, including: sheetrock taping, mud and texture coats, vinyl floor tiles, ceiling tiles plasters and stuccos, roofing tars, and shingles fireproofing (including fire blankets), caulks, gaskets brake pads and shoes, clutch plates and even stage curtains Still in use! Differences in the Big Three Different physical and chemical properties Chrysotile asbestos differs considerably from amphibole varieties in both physical and chemical composition Visually, white chrysotile fibres are softer and silkier than amphiboles, which are stiffer and needle-like Most notable is the iron content of amphibole varieties compared to chrysotile This appears to explain the greater durability or biopersistance of amphiboles in living tissue, and thus their higher fibrogenic and carcinogenic potential The Chrysotile Institute, a non profit organization established in 1984, is directed by a Board of directors made up of industry, labor and government representatives (Canada) Canada is a significant (top three) producers of white asbestos and continuously fights to increase its exports of white asbestos fibers and products Mistaken Identity Is vermiculite insulation a problem? – No Vermiculite is an asbestos alternative mineral Prior to its close in 1990, much of the world’s supply of vermiculite came from a mine near Libby, Montana This mine had a natural deposit of asbestos which resulted in the vermiculite being contaminated with asbestos Attic insulation produced using vermiculite ore, particularly ore that originated from the Libby mine, may contain asbestos fibers Today, vermiculite is mined at three U.S facilities and in other countries which have low levels of contamination in the finished material Vermiculite is a Phyllosilicates – Phyllosilicates are sheet silicates, form parallel sheets of silicate tetrahedra with Si2O5 With metal cations What should I if I have vermiculite attic insulation? DO NOT DISTURB IT Any disturbance has the potential to release asbestos fibers into the air Limiting the number of trips you make to your attic and shortening the length of those trips can help limit your potential exposure Proven Health Problems Asbestosis – Asbestosis is a serious, progressive, long-term non-cancer disease of the lungs It is caused by inhaling asbestos fibers that irritate lung tissues and cause the tissues to scar The scarring makes it hard for oxygen to get into the blood There is no effective treatment for asbestosis Generally from high exposure to asbestos Lung Cancer – Lung cancer causes the largest number of deaths related to asbestos exposure People who work in the mining, milling, manufacturing of asbestos, and those who use asbestos and its products are more likely to develop lung cancer than the general population People who have been exposed to asbestos and also are exposed to some other cancer-causing product, such as cigarette smoke, have a greater risk of developing lung cancer than people who have only been exposed to asbestos Mesothelioma – Mesothelioma is a rare form of cancer that is found in the thin lining (membrane) of the lung, chest, abdomen, and heart and almost all cases are linked to exposure to asbestos Other diseases There is evidence of animals fed asbestos developing colon lesions and having a lowered cell regulator defect = Colon Cancer ! Risks of these diseases vary greatly by length/concentration of exposure and fiber size Fibers greater than μm but still able to be inhaled have been branded as the culprits, fibers less than 5μm are considered harmless since they can be removed via macrophages but there are conflicting studies (esp Suzuki (2002)[Mount Sinai School of Medicine] annals of the New York Academy of Sciences, in press) Donham, et al CANCER 1980, 45(5, SUPPL.) 1073-1084 Inert but size does Matter! Animal studies have indicated that all main types of asbestos produce mesotheliomas in rats after intrapleural inoculation These studies indicate it is primarily the size of the fiber, rather than its chemical composition, which is responsible for the carcinogenic activity of asbestos Source: Wagner et al British Medical Bulletin, Vol 36, No 1, pages 53-56, 37 references, 19801980 Since the carcinogenic potency of asbestos appears to be dependent upon fiber size and shape, a carcinogenic potency estimate for "generic" asbestos is not proposed at this time Environmental chemistry and fate Source: Environmental Protection Agency Vol:EPA/540/1-86/049 (1984) 62 p There is no “average” particle size but >8μm have been deemed the primary danger Current Recommendations Review of report (1992) from Health Effects Institute – Asbestos Research (HEI – AR) HEI-AR paper gives linear risk model Wrong! because, they gave no consideration to different types of asbestos, assumed any particular concentration of environmental asbestos fibers were the same as the next test dose concentration (particle size etc) Only reviewed health data from miners/fabricators – no testing or account for varying health of individual or children/elderly However, due to the relatively low risks proven thus far from environmental fibers to the general public (using asbestos products) the OSHA standard is sufficient People are much more likely to die of breast or prostate cancer (1/7 and 1/6, respectively ACS) Sterling etal Comments on the Health Effects Institute-Asbestos Research (HEI-AR) Report: “Asbestos in Public and Commercial Buildings,” With Emphasis on Risk Assessment Methods Used American Journal of Industrial Medicine 24:767-781(1993) Cited 1988 Animal Research Injections in rats show a very nonlinear risk Similar for all common forms of Asbestos Human Proof, but… HEI-AR estimates 4-40 premature cancer deaths per million people exposed to ambient asbestos However, Joubert et al 1991 observed 43 cancer deaths where 25 were expected in a sample of 115 decedents who had been involuntarily exposed to asbestos Probability of this not being from asbestos alone is less than 0.003 Sample of Relative Risks (via University of Manchester, UK.) D.O.E (U.K.) < 0.0005 fibers ml-1 40 hrs/week for 20 years = attributable Life-time risk of death of ~ = 100,000 (about 1/100 of the death risk fro non-smokers from 2nd hand smoke or ~1/10 from one cigarette/day Ontario Royal Commission assume 0.001 f ml-1 , work exposure for 10 years = attributable risk of death risk 20:1,000,000.* about 1/50 of death risk of 10mile drive/working day for same time ."our best judgement as to the lifetime occupational exposure to asbestos at which the fibrotic process cannot advance to Asbestosis is in the range of 25 f/cc-yrs and below" (Ontario Royal Commission, 1984) OSHA Limit is 0.2 f/mL So, that’s 125 years in the OSHA limit to develop Asbestosis Relative Risk Overview The general public is at little/no risk from using asbestos products Breast cancer risk of death (1/7) Prostate cancer risk of death (1/6) Development of Asbestos at current OSHA limit would take 125 years Tested buildings reveal common risk of 1/100,000 and greater (< OSHA limit) However, risk to manufacturers or others that cause/stir asbestos dusk without proper protection is much higher to themselves and their families as shown by Joubert (Almost twice as many lung cancer deaths as expected) End [...]... little/no risk from using asbestos products Breast cancer risk of death (1/7) Prostate cancer risk of death (1/6) Development of Asbestos at current OSHA limit would take 125 years Tested buildings reveal common risk of 1/100,000 and greater (< OSHA limit) However, risk to manufacturers or others that cause/stir asbestos dusk without proper protection is much higher to themselves and their families as ... were mainly asbestos cement sheets and pipes for construction, casing for water and electrical/telecommunication services thermal and chemical insulation (i.e., fire rated doors, and gaskets)... different types of asbestos, assumed any particular concentration of environmental asbestos fibers were the same as the next test dose concentration (particle size etc) Only reviewed health data from... cancer (1/7 and 1/6, respectively ACS) Sterling etal Comments on the Health Effects Institute -Asbestos Research (HEI-AR) Report: Asbestos in Public and Commercial Buildings,” With Emphasis on Risk