This mandatory appendix specifies the procedure for analyzing
air samples for asbestos, tremolite, anthophyllite, and actinolite and
specifies quality control procedures that must be implemented by laboratories
performing the analysis. The sampling and analytical methods described below
represent the elements of the available monitoring methods (such as Appendix B
to this section, the most current version of the WISHA method ID-60, or the
most current version of the NIOSH 7400 method) which WISHA considers to be
essential to achieve adequate employee exposure monitoring while allowing
employers to use methods that are already established within their
organizations. All employers who are required to conduct air monitoring under
WAC
296-62-07709
are required to utilize analytical laboratories that use this procedure, or an
equivalent method, for collecting and analyzing samples.
(1) Sampling and analytical procedure.
(a) The sampling medium for air samples must
be mixed cellulose ester filter membranes. These must be designated by the
manufacturer as suitable for asbestos, tremolite, anthophyllite, and actinolite
counting. See below for rejection of blanks.
(b)
The preferred collection device is the 25-mm diameter cassette
with an open-faced 50-mm electrically conductive extension cowl. The 37-mm
cassette may be used if necessary but only if written justification for the
need to use the 37-mm filter cassette accompanies the sample results in the
employee's exposure monitoring record. Do not reuse or reload cassettes for
asbestos sample collection.
(c) An
air flow rate between 0.5 liter/min and 4.0 liters/min must be selected for the
25-mm cassette. If the 37mm cassette is used, an air flow rate between 1
liter/min and 4.0 liters/min must be selected.
(d) Where possible, a sufficient air volume
for each air sample must be collected to yield between one hundred and one
thousand three hundred fibers per square millimeter on the membrane filter. If
a filter darkens in appearance or if loose dust is seen on the filter, a second
sample must be started.
(e) Ship
the samples in a rigid container with sufficient packing material to prevent
dislodging the collected fibers. Packing material that has a high electrostatic
charge on its surface (e.g., expanded polystyrene) cannot be used because such
material can cause loss of fibers to the sides of the cassette.
(f) Calibrate each personal sampling pump
before and after use with a representative filter cassette installed between
the pump and the calibration devices.
(g)
Personal samples must be taken in the "breathing zone" of the
employee (i.e., attached to or near the collar or lapel near the worker's
face).
(h) Fiber counts must be
made by positive phase contrast using a microscope with an 8 to 10 X eyepiece
and a 40 to 45 X objective for a total magnification of approximately 400 X and
a numerical aperture of 0.65 to 0.75. The microscope must also be fitted with a
green or blue filter.
(i) The
microscope must be fitted with a Walton-Beckett eyepiece graticule calibrated
for a field diameter of one hundred micrometers (+/-2 micrometers).
(j) The phase-shift detection limit of the
microscope must be about 3 degrees measured using the HSE phase shift test
slide as outlined below.
(i) Place the test
slide on the microscope stage and center it under the phase
objective.
(ii) Bring the blocks
of grooved lines into focus.
| Note: |
The slide consists of seven sets of grooved lines (ca.
20 grooves to each block) in descending order of visibility from sets one to
seven, seven being the least visible. The requirements for asbestos, tremolite,
anthophyllite, and actinolite counting are that the microscope optics must
resolve the grooved lines in set three completely, although they may appear
somewhat faint, and that the grooved lines in sets six and seven must be
invisible. Sets four and five must be at least partially visible but may vary
slightly in visibility between microscopes. A microscope that fails to meet
these requirements has either too low or too high a resolution to be used for
asbestos, tremolite, anthophyllite, and actinolite counting. |
(iii)
If the image deteriorates, clean and adjust the microscope
optics. If the problem persists, consult the microscope manufacturer.
(k) Each set of samples taken
will include ten percent blanks or a minimum of two blanks. These blanks must
come from the same lot as the filters used for sample collection. The field
blank results must be averaged and subtracted from the analytical results
before reporting. Any samples represented by a blank having a fiber count in
excess of the detection limit of the method being used must be
rejected.
(l) The samples must be
mounted by the acetone/triacetin method or a method with an equivalent index of
refraction and similar clarity.
(m)
Observe the following counting rules.
(i)
Count only fibers equal to or longer than five micrometers.
Measure the length of curved fibers along the curve.
(ii) Count all particles as asbestos,
tremolite, anthophyllite, and actinolite that have a length-to-width ratio
(aspect ratio) of three to one or greater.
(iii)
Fibers lying entirely within the boundary of the Walton-Beckett
graticule field must receive a count of one. Fibers crossing the boundary once,
having one end within the circle, must receive the count of one-half. Do not
count any fiber that crosses the graticule boundary more than once. Reject and
do not count any other fibers even though they may be visible outside the
graticule area.
(iv) Count bundles
of fibers as one fiber unless individual fibers can be identified by observing
both ends of an individual fiber.
(v)
Count enough graticule fields to yield 100 fibers. Count a
minimum of 20 fields; stop counting at 100 fields regardless of fiber
count.
(n) Blind
recounts must be conducted at the rate of ten percent.
(2) Quality control procedures.
(a) Intralaboratory program. Each laboratory
and/or each company with more than one microscopist counting slides must
establish a statistically designed quality assurance program involving blind
recounts and comparisons between microscopists to monitor the variability of
counting by each microscopist and between microscopists. In a company with more
than one laboratory, the program must include all laboratories and must also
evaluate the laboratory-to-laboratory variability.
(b) Interlaboratory program.
(i) Each laboratory analyzing asbestos,
tremolite, anthophyllite, and actinolite samples for compliance determination
must implement an interlaboratory quality assurance program that as a minimum
includes participation of at least two other independent laboratories. Each
laboratory must participate in round robin testing at least once every six
months with at least all the other laboratories in its interlaboratory quality
assurance group. Each laboratory must submit slides typical of its own work
load for use in this program. The round robin must be designed and results
analyzed using appropriate statistical methodology.
(ii) All laboratories should participate in
a national sample testing scheme such as the Proficiency Analytical Testing
Program (PAT), the Asbestos Registry sponsored by the American Industrial
Hygiene Association (AIHA).
(c)
All individuals performing asbestos, tremolite, anthophyllite,
and actinolite analysis must have taken the NIOSH course for sampling and
evaluating airborne asbestos, tremolite, anthophyllite, and actinolite dust or
an equivalent course, recognized by the department.
(d) When the use of different microscopes
contributes to differences between counters and laboratories, the effect of the
different microscope must be evaluated and the microscope must be replaced, as
necessary.
(e) Current results of
these quality assurance programs must be posted in each laboratory to keep the
microscopists informed.
