STF - Audiência Pública do Amianto - 31/08/2012 - Supremo Tribunal Federal

D AVID M. BERNSTEIN, C ONSULTANT IN T OXICOLOGY, 1208 GENEVA, SWITZERLAND, davidb@itox.ch

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David Bernstein © copyright 2012 1


David M. Bernstein, Ph.D.

FEDERAL SUPREME COURT OF BRAZIL
STF PUBLIC HEARING – ASBESTOS
31 August 2012



David Bernstein © copyright 2012
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 Very frequently, amphibole asbestos (amosite,
crocidolite) was mixed with the chrysotile.
 There was little or no attempt to differentiate
exposure to these two very different minerals.



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 Chrysotile is a rolled sheet material like mica.
 The sheet is about 8 angstroms (0.8 nanometers) thick
and,
 because of molecular constraints, is rolled into
cylindrical form.
 The cylinders are chrysotile fibrils which bunch
together to form a chrysotile fiber.
 The chrysotile fiber is acid soluble (Pundsack, 1955).
.


Chrysotile

8 angstroms (0.8 nanometers)

Decomposes in acid



 In acid the rolled sheet of the chrysotile fiber
breaks apart into small pieces.
 This is important:
 In the lung – the cell which clears fibers &
particles from the lung – the macrophage –
creates an acid environment.
 In the gut (acid environment) .



 The amphibole asbestos class of fibers are formed
as solid rods/fibers (Skinner et al., 1988).
 The structure of an amphibole makes it very strong
and durable.
 The external surface of the crystal structures of
the amphiboles is quartz‐like, and has the chemical
resistance of quartz.
 Amphibole fibers, therefore, have negligible
solubility at any pH that might be encountered in
an organism (Speil and Leineweber, 1969).



or neutral pH
Not soluble in acid

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 Fiber dimensions (length and diameter)
 Fiber biosolublity (durability)
 Fiber dose



pH 7.4

Macrophage

pH 4

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pH 7.4

pH 4

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pH 7.4

pH 4

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Chrysotile

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 The more recent toxicology studies demonstrate
that:
 Brazilian chrysotile asbestos has a relatively short
biopersistence and
 does not result in pathological response even in a
sub‐chronic inhalation toxicology study at an
exposure concentration 5,000 times greater than
the US Threshold Limit Value of 0.1 f(WHO)/cm3.



 Following such exposures, chrysotile asbestos
produces neither
 a pathological response in the lung
 nor in the pleural cavity.
 In addition, the chrysotile fibers clear rapidly from
the lung and
 are not observed at the visceral pleural surface, in
the pleura nor on the parietal pleural surface.



 In the lung, immediately following a 5 day
exposure, the amphibole fibers have been shown
to produce extensive inflammation with
pathological lesions.
 Within 28 days after the 5 day exposure,
interstitial fibrosis was observed in the lung.
 The amphibole fibers are poorly cleared from the
lung with the longervfibers longer persisting
through the life‐time of the rats.



 Within 2 weeks after the 5 day exposure,
amphibole fibers were:
 observed penetrating through the visceral pleural
surface and
 were associated with extensive inflammation and
fibrotic development in the pleura.
 These pathological changes parallel closely those in
humans who develop mesothelioma.



 The early case‐control studies of mesothelioma
provided relationships of occupational exposure to
asbestos.
 However, due to the state of occupational hygiene
measurements at the time, none of the studies were
able to use exposure measurements which included
asbestos specific fiber number or fiber type.
 That is, the attribution of fiber specific effect was
performed based upon hypothetical exposures rather
than real data.



 The associations to disease were attributed to the
fiber most used without consideration of the
toxicological criteria that have been understood
more recently to determine fiber potency:
 fiber composition,
 biopersistence and
 fiber length.
 The inhalation toxicology studies have shown that
even a small exposure to long fiber amphibole
asbestos is pathogenic.


 The authors of very few of the epidemiology
studies on asbestos were able to state that there
was no amphibole exposure present in the cohort.
 One of the most comprehensive reviews of these
studies by Hodgson and Darnton (2000) considered
as “chrysotile only”, studies actually characterized
as predominately chrysotile exposure,
 and stated that small quantities of amphibole fiber
were ignored as being important to the findings in
some cohorts.


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Some of the factors not considered by the authors:

• Proximity to other industrial sources including a major
amphibole asbestos source.
• Use of local death rates which were 3 times the
national rates used by Dement.
• Occurrence of concurrent or prior exposures as
indicated by the obituaries.
• Use of national smoking rates.


 Weill et al. (1979):
 “No excess mortality was observed following exposure for 20
years to chrysotile asbestos at exposure levels   equal   to  or
less  than 100 MPPCF.years (corresponding  to  approximately
15 fibers/cm3 x years)”.

 Thomas et al. (1982)
 "Thus the general results of this mortality survey suggest that
the population of the chrysotile asbestos‐cement factory
studied are not at any excess risk in terms of total mortality, all
cancer mortality, cancers of the lung and bronchus, or
gastrointestinal cancers".



 Gardner MJ et al. (1986) :
 No excess of lung cancers or other asbestos‐related excess death
was reported, at mean fiber concentrations below 1 fiber/cm3,
although higher levels had probably occurred in certain areas
of the asbestos‐cement factory.

 Ohlson & Hogstedt (1985) :
 No excess work related mortality was observed at cumulative
exposures estimated at about 10‐20 fibers/cm3.years.



 Carel et al. (2006):
 study led by the International Agency for Research on Cancer
(IARC),
 The OR for asbestos exposure was 0.92 (95% confidence interval
(CI) 0.73‐1.15) in Central and Eastern Europe
 No effect
 Schneider et al. (2010):
 reported that the fibrosis scores of the asbestosis cases
correlated best with the number of uncoated commercial
amphibole fibers.



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What were the results?
D AVID M. B ERNSTEIN , C ONSULTANT IN T OXICOLOGY, 1208 G ENEVA, S WITZERLAND , davidb@itox.ch

The 3 main areas evaluated for each fiber type were:

 Epidemiology
 Toxicology
 Biopersistence



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 The Report of the World Health Organization
workshop on chrysotile asbestos substitutes,
has clearly reported that there is very little
scientific basis for the evaluation of the proposed
substitutes for chrysotile.

 For many of the fiber types, the limited data
available would suggest that they should be of
considerably greater concern than chrysotile.



 The scientific evidence recently published, as
shown by
 cohorts studies;
 epidemiological reviews and
 inhalation toxicology studies,
 provides strong support that chrysotile is
significantly less hazardous than the amphibole
forms of asbestos (e.g. crocidolite and amosite).



 The toxicology studies clearly demonstrate the
importance even of short term exposures to
amphibole asbestos in the causation of disease.
 In the earlier epidemiology studies, there was little
means available to quantify whether the workers
were exposed to amphibole asbestos.



 The Report of the World Health Organization
workshop on chrysotile asbestos substitutes, has
clearly reported that there is very little scientific
basis for the evaluation of the proposed substitutes
for chrysotile.

 For many of the fiber types, the limited data
available would suggest that they should be of
considerably greater concern than chrysotile.



 With proper control and use, chrysotile asbestos in
its modern day high‐density cement applications
does not present an excess risk of either:
 lung cancer or
 mesothelioma
 of any significance to public and/or worker health.



 I would be pleased to provide copies of all
supporting scientific publications to the Supreme
Court.


STF - Audiência Pública do Amianto - 31/08/2012 - Supremo Tribunal Federal

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STF - Audiência Pública do Amianto - 31/08/2012 - Supremo Tribunal Federal