Transcript Document

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 do 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 8 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 ~ 1 = 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