Asbestos Fibers and Other Elongate Mineral Particles: State of the ...

data are needed to more fully assess the particle
characteristics that cause adverse health outcomes
and to develop risk assessments.
Information on occupational exposures to non-
asbestiform EMPs is limited, as is information
on exposure to asbestos fibers and other EMPs
in mixed-dust environments, making it difficult
to assess the range of particle characteristics,
including dimension, in occupational settings
with exposures to nonasbestiform EMPs. The
few studies that have assessed biopersistence or
durability suggest that nonasbestiform EMPs are
not as biopersistent as asbestiform fibers of the
same length, but more information is needed
to systematically assess the ranges and importance
of biopersistence in determining toxicity.
Any assessment of risk needs to address the influence
of EMP dimensions, so studies that systematically
compare, to the extent possible, the
effects of asbestiform and nonasbestiform particles
of similar dimensions and dosimetrics—
such as particle count, disaggregation, and
surface area—from the same mineral (e.g.,
crocidolite and nonasbestiform riebeckite) are
needed for a variety of mineral types. Ultimately,
management of risk needs to be based
on an understanding of the estimated quantitative
risk from exposures to various EMPs and
on an understanding of the concentrations and
particle characteristics of the various EMPs to
NIOSH CIB 62 • Asbestos
which humans are or could be exposed and the
exposures in occupational and other settings.
An important need is to identify and develop
analytical methods that can be used or modified
to quantify occupational exposures to
EMPs of toxicological importance and that are
capable of differentiating EMPs on the basis of
particle characteristics demonstrated to be important
in causing disease. The current PCM
method is inadequate for assessing exposures
to fibers in mixed-dust environments, and
it lacks the capability to measure all the important
physical and chemical parameters of
EMPs thought to be associated with toxicity.
The feasibility of using EM methods will need
to be addressed if they are to replace the PCM
method. Until these issues are addressed, improvements
in PCM methodologies should be
pursued. In epidemiological and toxicological
research, EM methods will need to be used to
carefully characterize the exposure materials.
Also, the results of toxicological and epidemiological
studies may identify additional particle
characteristics that warrant further evaluation
to determine whether they can be incorporated
into sampling and analytical methods used
to assess worker exposures.
Section 3 of this Roadmap presents a framework
for proposed research intended to address
these scientific issues and inform future
public health policies and practices.
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