RJ LeeGroup, Inc.
Naturally Occurring Asbestos:
A Recurring Public Policy Challenge
R. J. Lee, B. R. Strohmeier, K. L.
Bunker, and D. R. Van Orden
RJ Lee Group, Inc.
350 Hochberg Road
Monroeville, PA 15146
www.rjlg.com
Main Points of Presentation
1.
What is Naturally Occurring Asbestos
(NOA) and where is it found?
2.
What are the key scientific and public policy issues
regarding NOA? Example – El Dorado Hills, CA.
3.
Complementary methodologies for properly
characterizing NOA in mixed mineral dust:
•
•
Transmission Electron Microscopy (TEM)
Field Emission Scanning Electron Microscopy (FESEM)
2
www.rjlg.com
Naturally Occurring Asbestos (NOA)
“Asbestos,” in current regulations and analytical methods, is a commercial
term defined as the asbestiform variety of six silicate minerals:
•
Chrysotile - Mg3Si2O5(OH)4
•
Crocidolite (riebeckite asbestos) - Na2Fe2+3,Fe3+2Si8O22(OH)2
•
Amosite (cummingtonite-grunerite asbestos) - (Mg,Fe2+)7Si8O22(OH)2
•
Anthophyllite asbestos - Mg7Si8O22(OH)2
•
Tremolite asbestos - Ca2Mg5Si8O22(OH)2
•
Actinolite asbestos - Ca2(Mg,Fe2+)5Si8O22(OH)2
Chrysotile, Gila County, AZ
Naturally occurring asbestos (NOA) is the general all-encompassing
name given to asbestos minerals found in-place in their natural state.
3
www.rjlg.com
Asbestiform vs. Non-Asbestiform Minerals
4
www.rjlg.com
ASBESTIFORM
As the drawings above illustrate, asbestiform (asbestos-like) minerals
consist of fibers that grow almost exclusively in one dimension, are
easily bent and occur as bundles of smaller fibers, which are called
fibrils. In fact, the bundling effect of asbestiform minerals is a unique
distinguishing feature. Some asbestiform minerals display splayed
ends. Asbestiform minerals also are long and thin, with aspect (lengthto-width) ratios of typically 20:1 to 100:1 or greater. Most asbestiform
fibers are less than 0.1 microns in width, and nearly all are less than 0.5
micron. Individual fibers are only visible with the aid of a microscope.
5
www.rjlg.com
ROCKS
Unlike asbestiform minerals, ordinary rock-forming minerals grow in
several directions at once. Under pressure, unlike asbestiform minerals
which bend, ordinary rock-forming minerals fracture easily into
particles called cleavage fragments. Of those, some are needle-shaped
(acicular), and some show stair-step cleavage patterns. Cleavage
fragments tend to be shorter and thicker than their asbestiform
counterparts; nearly all have widths that exceed 0.5 microns and lengths
below about 10 microns.
6
www.rjlg.com
Occurrences of amphibole minerals (green) and known
asbestos deposits (yellow) in the contiguous United States.
Chrysotile
Eden Mills, VT
Tremolite-Actinolite rock
Libby, MT
Actinolite Asbestos
Fairfax County, VA
California serpentine rock
with veins of chrysotile
NOA has existed in the environment for millions of years. However, asbestos,
whether it exists naturally in the ground or in manufactured products, is still asbestos
and poses a significant potential health hazard if it is released into the air and inhaled.
7
www.rjlg.com
Dust-Creating Human Activities
8
www.rjlg.com
Major Issues Concerning NOA
There is a lack of defined analytical methods that provide cost effective
discrimination between asbestos fibers and rock fragments.
Commercial “asbestos” definitions dictated in regulations are
inconsistent with scientific definitions for fibrous materials developed
by mineralogists.
Do the mineralogical distinctions between NOA and rock fragments
extend to their biological and health effects?
The limitations of the current scientific methods used to estimate the
risk of asbestos exposure.
Lack of uniform policies and different interpretations of regulatory
rules and scientific results have resulted in wide discrepancies in
asbestos assessments and recommended remedial actions in many
areas.
9
www.rjlg.com
Asbestos Identification in the Real World
Current
analytical protocols were
primarily designed to assess
occupational asbestos (chrysotile)
exposure in the workplace.
Asbestos
counting rules often simply specify the size and shape of
“fibers,” i.e., aspect ratio > 3:1, > 5 µm length, parallel sides.
Many
commercial asbestos laboratories are unfamiliar with the
identification and characterization of amphibole asbestos species.
Laboratories
often report any particles meeting the counting rules
as asbestos for simplicity and because of potential liability.
10
www.rjlg.com
Repercussions of NOA Misidentification
Overestimation of environmental asbestos levels and exposure
risk based on incorrect science will mistakenly alarm the public
and divert attention and financial resources from more socially
important endeavors.
Underestimation of environmental asbestos levels and
exposure risk can result in failures to properly protect the
public health.
The ultimate consequence of not correcting the current
controversies surrounding proper NOA identification will be
inaccurate environmental asbestos concentrations and
scientifically inaccurate risk assessments.
11
www.rjlg.com
“Asbestos” Reported in El Dorado Hills, CA
EPA Analysis Report, released May 2005
•
•
RJLG conducted peer review of the EPA report
and underlying data, November 2005
•
Series of activity-based air sampling (hiking, biking,
and simulated baseball games) and soil sampling.
Reported “the presence of asbestos at elevated levels in
air at breathing heights for children and adults.”
“Based on mineralogy, 63% of the amphibole particles
identified as asbestos fibers cannot be asbestos.”
U.S. Geological Survey report, late 2006
•
“…if the USEPA study had been conducted as an
enforcement action, it would be difficult to classify the
majority of actinolite-magnesiohornblende of the El
Dorado Hills area as an actionable material because (1)
the majority of the particles are prismatic, not fibrous,
and (2) approximately 40 percent of the particles are
magnesiohornblende.”
Images taken from http://www.epa.gov/region09/toxic/
noa/eldorado/index.html
12
www.rjlg.com
Mitigation Costs in El Dorado Hills, CA
Recent
mitigation efforts over alleged asbestos at Oak
Ridge High School had a cost of over $1.7 million.
Cost
related to mitigation efforts for a new elementary
school has been in excess of $1.8 million.
Data
from the adjoining community of Folsom, CA
indicates that their cost will be in excess of $5 million
to mitigate alleged NOA concerns during the
construction of a new high school.
13
www.rjlg.com
Complementary TEM and SEM Techniques for
the Characterization of Mixed Mineral Environments
TEM
SEM
14
www.rjlg.com
Complementary TEM and SEM Techniques for
the Characterization of Mixed Mineral Environments
SEM
TEM
Technique called-for under
current regulations
FESEM provides comparable
magnifications to TEM
Provides projection image (no
surface details and limited
morphology)
Allows observation of unique
morphological features not
seen in TEM
Provides chemistry (EDS)
Provides chemistry (EDS)
Provides crystallography
(SAED)
Crystallography only with
specialized equipment
15
www.rjlg.com
Complementary TEM and FESEM Characterization
TEM Image
FESEM Image
1 µm
Comparison of TEM and FESEM images for a bundle
of asbestos fibers from a Canadian chrysotile mine
16
www.rjlg.com
Complementary TEM and FESEM Characterization
TEM Image
FESEM Image
1 µm
TEM identified (EDS/SAED) this structure as chrysotile.
FESEM showed that the structure is a bundle of fibers.
17
www.rjlg.com
Complementary TEM and FESEM Characterization
TEM Image
FESEM Image
1 µm
1 µm
TEM identified (EDS/SAED) this El Dorado Hills soil particle as actinolite. The
FESEM image shows that the particle is a non-asbestiform rock fragment.
18
www.rjlg.com
Typical Amphibole Rock Fragment from El Dorado Hills Soil
FESEM Image
Results
indicate that
most elongated
amphibole mineral
particles in El
Dorado Hills soil
are not asbestiform.
This
nonasbestiform
actinolite rock
fragment shows
well-defined
cleavage planes.
1 µm
19
www.rjlg.com
Complementary TEM and FESEM Characterization
TEM Image
FESEM Image
1 µm
2 µm
TEM identified (EDS/SAED) this El Dorado Hills soil particle as actinolite. The
FESEM image shows that the particle is a non-asbestiform rock fragment.
20
www.rjlg.com
Complementary TEM and FESEM Characterization
TEM Image
FESEM Image
2 µm
2 µm
TEM identified (EDS/SAED) this El Dorado Hills soil particle as actinolite. The
FESEM image shows that the particle is a non-asbestiform rock fragment.
21
www.rjlg.com
Dimensions and Morphology of Rock Fragments vs. Asbestos Fibers
FESEM Image – Rock Fragment
FESEM Image – Chrysotile Bundle
2
2.
µm
2.2
µm
2 µm
2 µm
Some researchers contend that rock (cleavage) fragments can have
the same diameter and dimensions as airborne asbestos fibers.
This concept is a myth.
22
www.rjlg.com
Summary
The emerging practice of fully characterizing (chemistry,
crystallography, and morphology) mixed mineral dust on a particle-byparticle basis is possible with a complementary TEM/FESEM
approach.
Accurate characterization of mixed mineral dusts will be important for:
a) the development of accepted analytical protocols for separating
NOA from related rock fragments;
b) correct interpretation of results from risk evaluation and health
studies involving NOA and rock fragments; and
c) the development of effective public policies for managing NOA,
minimizing potential hazards, and protecting the public health.
23
www.rjlg.com
Summary (cont.)
Recommendation – An independent government-funded and peerreviewed panel study on NOA would be the most effective way to:
a) develop reliable national NOA analytical methods that are:
i) reproducible;
ii) follow accepted scientific and laboratory practices; and
iii) result in remediation actions that are conducted only
when they are truly necessary to protect health; and
b) establish a consensus among the medical community
as to the health effects of asbestos and non-asbestiform rock
fragments, particularly in mixed mineral dust environments.
24
www.rjlg.com