Washington Administrative Code › Title 296 - Labor and Industries, Department of › Chapter 296-62 - General occupational health standards › Part G - CARCINOGENS (SPECIFIC) › Section 296-62-07449 - Appendix E - Cadmium in workplace atmospheres

Current through Register Vol. 24-14, July 15, 2024
Method number: ID-189 (OSHA); (ICP/MS) 0009 (WISHA)
Matrix: Air
WISHA permissible exposure limits: 5
				  µg/m3 (TWA), 2.5
				  µg/m3 (action level TWA)
Collection procedure: A known volume of air is drawn through
				  a 37-mm diameter filter cassette containing a 0.8 µm mixed cellulose
				  ester membrane filter (MCEF).
Recommended air volume: 960 L
Recommended sampling rate: 2.0 L/min
Analytical procedure: Air filter samples are digested with
				  nitric acid. After digestion, a small amount of hydrochloric acid is added. The
				  samples are then diluted to volume with deionized water and analyzed by either
				  flame atomic absorption spectroscopy (AAS) or flameless atomic absorption
				  spectroscopy using a heated graphite furnace atomizer (AAS-HGA).
Detection limits:
Qualitative: 0.2 µg/m3 for a
				  200 L sample by Flame AAS, 0.007 µg/m3 for a
				  60 L sample by AAS-HGA
Quantitative: 0.70 µg/m3 for
				  a 200 L sample by Flame AAS, 0.025 µg/m3 for a
				  60 L sample by AAS-HGA
Precision and accuracy: (Flame AAS Analysis and AAS-HGA
				  Analysis):
Validation level: 2.5 to 10
				  µg/m3 for a 400 L air vol, 1.25 to 5.0
				  µg/m3 for a 60 L air vol CV1 (pooled): 0.010,
				  0.043
Analytical bias: +4.0%, -5.8%
Overall analytical error: ±6.0%, ±14.2%
Method classification: Validated Date: June, 1992
Inorganic Service Branch II, OSHA Salt Lake Technical Center,
				  Salt Lake City, Utah Commercial manufacturers and products mentioned in this
				  method are for descriptive use only and do not constitute endorsements by
				  USDOL-OSHA. Similar products from other sources can be substituted.
(1) Introduction.
(a) Scope.
This method describes the collection of airborne elemental
				  cadmium and cadmium compounds on 0.8 µm mixed cellulose ester membrane
				  filters and their subsequent analysis by either flame atomic absorption
				  spectroscopy (AAS) or flameless atomic absorption spectroscopy using a heated
				  graphite furnace atomizer (AAS-HGA). It is applicable for both TWA and action
				  level TWA permissible exposure level (PEL) measurements. The two atomic
				  absorption analytical techniques included in the method do not differentiate
				  between cadmium fume and cadmium dust samples. They also do not differentiate
				  between elemental cadmium and its compounds.
(b) Principle.
Airborne elemental cadmium and cadmium compounds are
				  collected on a 0.8 µm mixed cellulose ester membrane filter (MCEF). The
				  air filter samples are digested with concentrated nitric acid to destroy the
				  organic matrix and dissolve the cadmium analytes. After digestion, a small
				  amount of concentrated hydrochloric acid is added to help dissolve other metals
				  which may be present. The samples are diluted to volume with deionized water
				  and then aspirated into the oxidizing air/acetylene flame of an atomic
				  absorption spectrophotometer for analysis of elemental cadmium. If the
				  concentration of cadmium in a sample solution is too low for quantitation by
				  this flame AAS analytical technique, and the sample is to be averaged with
				  other samples for TWA calculations, aliquots of the sample and a matrix
				  modifier are later injected onto a L'vov platform in a pyrolytically-coated
				  graphite tube of a Zeeman atomic absorption spectrophotometer/graphite furnace
				  assembly for analysis of elemental cadmium. The matrix modifier is added to
				  stabilize the cadmium metal and minimize sodium chloride as an interference
				  during the high temperature charring step of the analysis subsection (5)(a) and
				  (b) of this section.
(c)
				History.
Previously, two OSHA sampling and analytical methods for
				  cadmium were used concurrently WAC
				  296-62-07449(5)(c) and
				  (d). Both of these methods also required 0.8
				  µm mixed cellulose ester membrane filters for the collection of air
				  samples. These cadmium air filter samples were analyzed by either flame atomic
				  absorption spectroscopy (subsection (5)(c) of this section) or inductively
				  coupled plasma/atomic emission spectroscopy (ICP-AES) (subsection (5)(d) of
				  this section). Neither of these two analytical methods have adequate
				  sensitivity for measuring workplace exposure to airborne cadmium at the new
				  lower TWA and action level TWA PEL levels when consecutive samples are taken on
				  one employee and the sample results need to be averaged with other samples to
				  determine a single TWA. The inclusion of two atomic absorption analytical
				  techniques in the new sampling and analysis method for airborne cadmium permits
				  quantitation of sample results over a broad range of exposure levels and
				  sampling periods. The flame AAS analytical technique included in this method is
				  similar to the previous procedure given in the General Metals Method ID-121
				  (subsection (5)(c) of this section) with some modifications. The sensitivity of
				  the AAS-HGA analytical technique included in this method is adequate to measure
				  exposure levels at 1/10 the action level TWA, or lower, when less than
				  full-shift samples need to be averaged together.
(d) Properties (subsection (5)(e) of this
				section).
Elemental cadmium is a silver-white, blue-tinged, lustrous
				  metal which is easily cut with a knife. It is slowly oxidized by moist air to
				  form cadmium oxide. It is insoluble in water, but reacts readily with dilute
				  nitric acid. Some of the physical properties and other descriptive information
				  of elemental cadmium are given below:
CAS No . . . . . . . . . . . .
7440-43-9
Atomic Number . . . . . . . . . . . .
48
Atomic Symbol . . . . . . . . . . . .
Cd
Atomic Weight . . . . . . . . . . . .
112.41
Melting Point . . . . . . . . . . . .
321°C
Boiling Point . . . . . . . . . . . .
765°C
Density . . . . . . . . . . . .
8.65 g/mL (25°C)
The properties of specific cadmium compounds are described in
				  reference subsection (5)(e) of this section.
(e) Method performance.
A synopsis of method performance is presented below. Further
				  information can be found in subsection (4) of this section.
(i) The qualitative and quantitative
				detection limits for the flame AAS analytical technique are 0.04 µg
				(0.004 µg/mL) and 0.14 µg (0.014 µg/mL) cadmium,
				respectively, for a 10 mL solution volume. These correspond, respectively, to
				0.2 µg/m3 and 0.70
				µg/m3 for a 200 L air volume.
(ii) The qualitative and quantitative
				detection limits for the AAS-HGA analytical technique are 0.44 ng (0.044 ng/mL)
				and 1.5 ng (0.15 ng/mL) cadmium, respectively, for a 10 mL solution volume.
				These correspond, respectively, to 0.007 µg/m3
				and 0.025 µg/m3 for a 60 L air
				volume.
(iii) The average recovery
				by the flame AAS analytical technique of 17 spiked MCEF samples containing
				cadmium in the range of 0.5 to 2.0 times the TWA target concentration of 5
				µg/m3 (assuming a 400 L air volume) was 104.0%
				with a pooled coefficient of variation (CV1) of
				0.010. The flame analytical technique exhibited a positive bias of +4.0% for
				the validated concentration range. The overall analytical error (OAE) for the
				flame AAS analytical technique was ±6.0%.
(iv) The average recovery by the AAS-HGA
				analytical technique of 18 spiked MCEF samples containing cadmium in the range
				of 0.5 to 2.0 times the action level TWA target concentration of 2.5
				µg/m3 (assuming a 60 L air volume) was 94.2%
				with a pooled coefficient of variation (CV1) of
				0.043. The AAS-HGA analytical technique exhibited a negative bias of -5.8% for
				the validated concentration range. The overall analytical error (OAE) for the
				AAS-HGA analytical technique was ±14.2%.
(v) Sensitivity in flame atomic absorption is
				defined as the characteristic concentration of an element required to produce a
				signal of 1% absorbance (0.0044 absorbance units). Sensitivity values are
				listed for each element by the atomic absorption spectrophotometer manufacturer
				and have proved to be a very valuable diagnostic tool to determine if
				instrumental parameters are optimized and if the instrument is performing up to
				specification. The sensitivity of the spectrophotometer used in the validation
				of the flame AAS analytical technique agreed with the manufacturer
				specifications (subsection (5)(f) of this section); the 2 µg/mL cadmium
				standard gave an absorbance reading of 0.350 abs. units.
(vi) Sensitivity in graphite furnace atomic
				absorption is defined in terms of the characteristic mass, the number of
				picograms required to give an integrated absorbance value of 0.0044
				absorbance-second (subsection (5)(g) of this section). Data suggests that under
				stabilized temperature platform furnace (STPF) conditions (see (f)(ii) of this
				subsection), characteristic mass values are transferable between properly
				functioning instruments to an accuracy of about twenty percent (subsection
				(5)(b) of this section). The characteristic mass for STPF analysis of cadmium
				with Zeeman background correction listed by the manufacturer of the instrument
				used in the validation of the AAS-HGA analytical technique was 0.35 pg. The
				experimental characteristic mass value observed during the determination of the
				working range and detection limits of the AAS-HGA analytical technique was 0.41
				pg.
(f) Interferences.
(i) High concentrations of silicate interfere
				in determining cadmium by flame AAS (subsection (5)(f) of this section).
				However, silicates are not significantly soluble in the acid matrix used to
				prepare the samples.
(ii)
				Interferences, such as background absorption, are reduced to a minimum in the
				AAS-HGA analytical technique by taking full advantage of the stabilized
				temperature platform furnace (STPF) concept. STPF includes all of the following
				parameters (subsection (5)(b) of this section):
(A) Integrated absorbance;
(B) Fast instrument electronics and sampling
				frequency;
(C) Background
				correction;
(D) Maximum power
				heating;
(E) Atomization off the
				L'vov platform in a pyrolytically coated graphite tube;
(F) Gas stop during atomization;
(G) Use of matrix modifiers.
(g) Toxicology
				(subsection (5)(n) of this section).
Information listed within this section is synopsis of current
				  knowledge of the physiological effects of cadmium and is not intended to be
				  used as the basis for WISHA policy. IARC classifies cadmium and certain of its
				  compounds as Group 2A carcinogens (probably carcinogenic to humans). Cadmium
				  fume is intensely irritating to the respiratory tract. Workplace exposure to
				  cadmium can cause both chronic and acute effects. Acute effects include
				  tracheobronchitis, pneumonitis, and pulmonary edema. Chronic effects include
				  anemia, rhinitis/anosmia, pulmonary emphysema, proteinuria and lung cancer. The
				  primary target organs for chronic disease are the kidneys (noncarcinogenic) and
				  the lungs (carcinogenic).