Asbestos NIOSH methods

Air drawn through a 0.8 to 1.2 mm cellulose ester membrane filter, asbestos fibers counted by positive phase contrast microscopy technique sample prepared by acetone/triacetin method (NIOSH Method 7400, 1985). 

Alternatively, asbestos fibers collected on the filter counted by TEM, following the modified Jaffe wick technique for sample preparation (NIOSH Method 7402, 1987). 

Percent chrysotile asbestos in bulk samples may be measured by X-ray powder diffraction (NIOSH Method 9000, 1984) sample dust grinded under liquid N2 wet sieved through 10-mm sieve sieved material treated with 2-propanol agitated in an ultrasonic bath filtered on a silver filter measured by XRD, using a Cu target X-ray tube. 

The NIOSH method for the analysis of asbestos (9) states that "The method is intended to give an index of employee exposure to airborne asbestos fibers of specified dimensional characteristics. It is not meant to count all asbestos fibers in all size ranges or to differentiate asbestos from other fibrous particulates". 

The NIOSH method (101 also states, however, "In an atmosphere known to contain asbestos, all particulates with a length to diameter ratio of 3 to 1 or greater, and a length greater than 5 micro meters should in the absence of other information, be considered to be asbestos fibers and counted as such1 (emphasis added). 

Light Microscopic Method. Phase contrast microscopy (PCM) accurately assesses fiber exposure levels for fibers 5 pm in length and >0.25 pm in diameter. Furthermore, PCM cannot differentiate between asbestos and nonasbestos fibers. Currently, the standard method for the determination of airborne asbestos particles in the workplace is NIOSH Method 7400, Asbestos by Phase Contrast Microscopy (NIOSH 1994a). OSHA considers that sampling and analytical procedures contained in OSHA Method ID-160 and NIOSH Method 7400 are essential for obtaining adequate employee exposure monitoring. Therefore, all employers who are required to conduct monitoring are required to use these or equivalent methods to collect and analyze samples (OSHA 1994). In NIOSH Method 7400, asbestos is collected on a 25 mm cellulose ester filter (cassette-equipped with a 50 mm electrically-conductive cowl). The filter is treated to make it... 

NIOSH. 1989b. Asbestos fibers - method 7402. In NIOSH manual of analytical methods. 3rded. Supplement. Cincinnati, OH National Institute for Occupational Safety and Health, 7402-1 - 7402-8. 

Sheehan MJ, Reynolds JW. 1992. Airborne asbestos analysis of low fiber density samples A comparison of the A and B counting rules of the NIOSH method 7400. Applied Occupational Environmental Hygiene 7(1) 38-41. 

Polarized light microscopy is frequently used for determining the asbestos content of bulk samples of insulation or other building materials (see, for example, NIOSH Method 9002 [NIOSH 1989] and OSHA method ID-191 [OSHA 1994]). This method also enables qualitative identification of asbestos types using morphology, color, and refiactive index. 

NIOSH method 7400 for mounting sampling cassette filters on microscope slides used primarily for asbestos sampling work. National Institute for Occupational Safety and Heafth, 1986. Preview free Purchase 80... 

The Occupational Safety and Health Administration (OSHA) standard for exposure to asbestos defines a fiber as one at least 5 p,m long with a length/diameter ratio of at least 3.0. The TLV-TWA is 0.1 fibers/cc of air the excursion limit for a 30-min sampling period is 1.0. The standard, published in 29 CFR 1910.1001 specifies sampling methods and fiequencies as well as the analytical procedure (NIOSH Method 7400). Some countries allow higher concentrations of fiber. In Brazil, Canada, and Mexico, for example, the TLV is 2 fibers/ml. In the European Union, the TLV is 0.6 fibers/ml (0.25 in Germany), with an action level of 0.2. 

National Institute of Occupational Safety and Health, Asbestos and other Fibers by PCM. NIOSH Method 7400, Issue 2, NIOSH Manual of Analytical Methods, 4th edn., DHHS (NIOSH)... 

This paper will not discuss counting rules for asbestos. The phase contrast method is fully described by NIOSH (38). It is... 

Leidell, N.A., Bayer, S.G., Zumwalde, R.D., and Busch, K.A., NIOSH - A Technical Report "USPHS/NIOSH Membrane Filter Method for Evaluating Airborne Asbestos Fibers". Feb. 1979. DHEW (NIOSH) Publication no. 79-127. U.S. Department of Health, Education and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health. 

Units of Exposure. Consideration and comparison of quantitative data on asbestos inhalation studies are complicated by the fact that a number of different methods have been used to measure asbestos levels in air. Currently, the standard method for measuring asbestos concentrations in workplace air employs phase contrast microscopy (PCM). A particle visible under PCM is counted as a fiber if it is 5 micrometers (pm) long and has a length/thickness ratio of 3 1. However, the method cannot detect fibers thinner than about 0.3 pm and caimot distinguish between asbestos fibers and other fibers (NIOSH 1987). 

The purpose of this chapter is to describe the analytical methods that are available for detecting, measuring, and/or monitoring asbestos, its metabolites, and other biomarkers of exposure and effect to asbestos. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is to identify well-established methods that are used as the standard methods of analysis. Many of the analytical methods used for environmental samples are the methods approved by federal agencies and organizations such as ERA and the National Institute for Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are approved by groups such as the Association of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). Additionally, analytical methods are included that modify previously used methods to obtain lower detection limits and/or to improve accuracy and precision. 

For the analysis of asbestos fibers in air, a sample of air is drawn through a filter by a vacuum pump (usually at a flow-rate of around 1-2 L/minute), and the fibers retained on the filters are examined microscopically. The sensitivity of the methods depends on the volume of air drawn through the filter and the microscopic method employed. In the workplace, where PCM is the standard method, the theoretical detection limit for a short-term sample (15 minutes) is around 0.04 PCM f/mL, but may be reduced to 0.001 f/mL using an 8-hour sample (NIOSH 1976). In practice, such low detection limits are not readily achievable, and measured values below 0.1 PCM 17mL should not usually be considered reliable (ASTM 1988). Sensitivity of TEM methods for ambient or indoor air are usually around 0.1-1 ng/m. ... 

NIOSH. 1994a. Asbestos and other fibres by PCM. In Manual of analytical methods, 4th edition. Cincinnati, OH U.S. Department of Health and Human Services, National Institute for Occupational Safety and Health. 

Asbestos fibers in air may be analyzed by NIOSH (1984) Methods 7402, 7400, and 9000. Method 7402 specifies the analysis using a transmission electron microscope with electron diffraction and energy dispersive x-ray capabilities. Cellulose ester membranes 25 mm in diameter and 0.8-1.2 pm long and a conductive cassette are used to collect the sample. The counting range in the method is 80-100 fibers. Nonasbestiform amphiboles may interfere if the individual particles have the aspect ratio >3 1. This may be eliminated by quantitative zone axis electton diffraction analysis. 

Asbestos must be removed only by fully trained personnel using methods and protective equipment mandated by OSHA (29 CFR 1910.1001). The OSHA asbestos standard should be consulted along with the appropriate NIOSH and EPA publications. Only workers fully trained in asbestos handling should be allowed in areas where asbestos is exposed. OSHA outlines work practices appropriate for handling asbestos in 29 CFR 1910.1001. Healthcare organizations must outUne OSHA requirements in the facility Asbestos Management Policy. 

Cleavage Fragments Mineral particles formed by brane method for counting asbestos fibers in the United comminution of minerals, especially those characterized states. This method was refined by NIOSH and published... 

Guides, or manuals, or standards such as those published by the US NIOSH, UK HSE or Australian Standards respeetively, should be consulted for methods of measuring inspirable dust, respirable dust, asbestos, synthehc mineral fibres, and organic vapours. Inspirable dust measurements are useful for dusts like lead-eontaining dust where dust in the month and nose may be swallowed. 

NIOSH, Asbestos and Other Fibers 7400, in NIOSH Manual of Analytical Methods, U.S. Gov. Printing Office, Washington, DC, 1989. 

---