ANOTHER EDITION OF…. DUSTY DEBBIE blasts particulate matters.
THE EMERGENCE OF NEW DUST SAMPLERS FOR NEW ISSUES SPECIAL FOCUS: 2013 OSHA PROPOSED RULEMAKING ON SILICA
WHY DO WE NEED NEW DUST SAMPLERS? New concerns with traditional samplers New criteria for size-selective sampling New regulations and guidelines New priorities and demands from users
NEW CONCERNS WITH TRADITIONAL SAMPLERS US NIOSH and OSHA scientists have been addressing sample losses with traditional 37-mm filter cassettes. Of particular concern, are sample losses that occur from particles that adhere to the interior cassette walls and are not analyzed.
U.S. OSHA STATEMENT IN HEXAVALENT CHROMIUM METHOD “ Tests showed that Cr (VI) equivalent to 0 to 123% of the amounts found on the PVC filter were present on the interior walls of cassettes used for compliance samples. It is now routine procedure to wipe interior walls of sampling cassettes for all metal samples analyzed.” Source: United States. Occupational Safety and Health Administration. Hexavalent Chromium. 30 Apr 2009
NIOSH STATEMENT IN AIHA JOURNAL ARTICLE Dust deposits on the walls of filter cassettes were 19% of the total sample for lead and 25% of the total sample for copper. Filter cassettes should be rinsed and wiped prior to analysis. Source: Ashley, Kevin, Harper, Martin and Demange, Martine. “Concerning Sampler Wall Deposits in the Chemical Analysis of Airborne Metals.” Journal of Occupational and Environmental Hygiene 4:9 Sept 2007: D81 - D86
ACCU-CAP EMERGES TO ADDRESS CONCERNS Filter insert that is placed into a 2-piece cassette with support pad. Consists of a clear plastic dome heat- sealed to a filter. Dust is collected onto the filter or within the dome for gravimetric analysis. PVC ACCU-CAP FOR GRAVIMETRIC ANALYSIS
A NEW SOLU-CAP EMERGES BASED ON NIOSH RESEARCH Designed for chemical analysis of metals Mixed cellulose ester filter heat sealed to acid digestible cellulose acetate dome Pre-loaded into 2-piece cassettes with support pads Eliminates the need to wipe the inside of the cassette to obtain reliable exposure measurements Source: Ashley, Kevin, Harper, Martin. “Acid-Soluble Internal Capsules for Closed-Face Cassette Elemental Sampling and Analysis of Workplace Air.” Journal of Occupational and Environmental Hygiene 10:6, 297-306, February 25, 2013.
NEW CRITERIA FOR SIZE-SELECTIVE SAMPLING In 1993, ACGIH joined with ISO and CEN in defining particulates in terms of inhalable, thoracic, and respirable particulate mass fractions. See page 80 of the 2013 TLV handbook.
NOTE FOR NEWCOMERS: CURRENT PARTICULATE FRACTIONS Inhalable-particles that are hazardous when deposited anywhere in the respiratory system (including those that enter nose/mouth) Thoracic-particles hazardous when deposited anywhere within the lung airways and gas- exchange region Respirable-particles hazardous when deposited in the alveolar gas-exchange region.
INHALABLE PARTICULATE: A CLOSER LOOK Review of pertinent scientific issues presented at an AIHCE session The impact on dust samplers
HISTORICAL PERSPECTIVE: TERMS AND SPECIFICATIONS Except in cases where diseases are caused by fine respirable dust, it has been common practice to sample so-called total dust. This is in general recognition that all inhaled particles could present either a specific or non-specific risk to health. (Mark and Vincent, Ann. Occup. Hyg.,1986.)
PROBLEMS WITH TOTAL DUST: SPECIFICATIONS Total dust has never been defined by a specific size range and a 50% cut-point (D 50 ) was never established for total dust samplers. Given the vague definition of total dust, a number of personal samplers with various performance characteristics have been used for sampling total dust around the world.
TOTAL DUST SAMPLERS USED GLOBALLY Single-hole head 7-hole head 37- or 25- mm filter cassettes
SURPRISING STATISTICS: SAMPLER PERFORMANCE There is very limited data available on how well these samplers actually measure the true dust exposure. Studies show considerable differences in results from these various samplers when sampling the very same dust under the identical environmental conditions. (Mark and Vincent, 1986) ≠≠
SURPRISING STATISTICS: LIMITATIONS OF 37-MM CASSETTES 37-mm Filter Cassettes : Were never designed to represent a physiologically relevant exposure to the respiratory system. Aspiration efficiency is not very similar to the nose and mouth. Are not 100% efficient in collecting all sizes of dust particles. Have a upper size limit (approx. 30 um) where efficiency falls to zero. ( T. Renee Anthony, AIHCE 2011 )
SURPRISING STATISTICS : ERRORS WITH 37-MM CASSETTES Sampling errors with 37-mm cassettes can occur from: Ambient wind velocity effects Orientation effects Dust deposition on walls of cassette
INHALABLE SAMPLERS EMERGE Since occ hygienists are concerned with the health-related dose, new dust samplers have emerged that measure dust concentrations with the same efficiency as we inhale them.
THE IDEAL DUST SAMPLER An inhalable sampler is considered ideal “when a personal sampler mounted on the body gives the same measured dust concentration and aerodynamic size distribution as that inspired by its wearer, regardless of dust source location and wind conditions”. (Mark and Vincent, 1986) Inhalable samplers have a 50% cut-point of 100 microns.
INHALABLE SAMPLERS: FOR THE NEW CRITERIA The first personal sampler specifically designed for inhalable particulate mass was developed by Mark and Vincent in 1986 at the Institute of Occupational Medicine in Scotland and was licensed to SKC Ltd. in the U.K. SKC 225-70A
ADVANTAGES OF THE IOM SAMPLER: TECHNICAL Developed specifically to match the inhalable definition. Precise fit to the inhalable curve at 2 L/min Conductive plastic cassette for gravimetric and stainless steel cassette for chemical analysis. Internal wall deposits are included in the sample analysis. Can be combined with a foam insert to collect the respirable fraction simultaneously.
ADVANTAGES OF THE IOM SAMPLER: CONFORMANCE The IOM is specified by name in many standards/methods including UK HSE Method 14/3; Australian Standard 3640, and NIOSH Method 5700. In response to an SKC inquiry, U.S. OSHA issued a statement indicating the IOM could be used as an equivalent sampler for particulates not otherwise classified. Copies available upon request.
OTHER INHALABLE SAMPLERS: BUTTON SAMPLER Designed for use at 4 L/min to enhance sensitivity Inlet has a stainless steel inlet screen to keep out large, non- inhalable projectiles from impacting or splashing onto the filter. Suitable for area or personal sampling. SKC 225-360
SWEDISH MINI-SAMPLER FOR INHALABLE MANGANESE Enable positioning of the sampler inlet within close proximity of the welder’s nose and mouth even when wearing a face shield. Used with the SKC Face Level Sampling Head Set Mini-Sampler SKC 225-6201 Headset SKC 225-6200 Developed in a research project partly funded by the Swedish Work Environment Authority and carried out at Stockholm University, Sweden.
MINI-SAMPLER COMPONENTS 13-mm Swinnex filter holder modified into an open- face filter holder. Incorporates a specially designed aluminum entry nozzle which protrudes out the front of the holder as the sampler inlet. PTFE-coated O-ring and the retaining ring holds the 13-mm filter in place in the sampler body. Figure 1
MINI-SAMPLER: ADVANTAGES/APPLICATIONS Advantages: The headset mounting arrangement improves personal sampling as it maintains the sampler close to nose/mouth. Applications: Only for inhalable sampling where 90% of the mass size distribution is below 20 um (including manganese).
DATA COMPARISON?? TOTAL VS INHALABLE Inhalable particulate mass is typically greater than so-called total particulate mass. How much greater will depend upon the SIZE of the particles. With larger particles, inhalable particulate mass will be much greater than total particulate mass. With smaller particles, inhalable and total particulate mass will be comparable.
A CONVERSION FACTOR?? TOTAL VS INHALABLE So what do you do? Collect side-by-side 37-mm cassette and inhalable samples and determine process-specific conversion factors for YOUR unique application. The AIHCE session made the point that it is really not enough to use a simple conversion factor from total to inhalable as there are too many variables.
2013 INTENDED CHANGES TO TLVs ® ISSUED AS INHALABLE Clopidol 2,4-D Diethylene glycol monobutyl ether Manganese, elemental and inorganic cpds. O-Phthalodinitrile Piperazine and salts 2,4- or 2,6- Toluene diisocyanate Tributyl phosphate For TLVs with IFV notation (Inhalable fraction and vapor) There is no single sampler that can be used. Requires (2) separate samples: one for each contaminant phase.
THORACIC PARTICULATE: A CLOSER LOOK Definitions of size fraction Specifications for samplers Sampler options Applications
THORACIC PARTICULATE DEFINED Thoracic particulate is defined as material hazardous when deposited within the lung airways and down into the gas exchange region. Thoracic samplers have a 50% cut-point of 10 um.
THORACIC SAMPLERS EMERGE The first thoracic sampler was developed by BGI Inc. The BGI GK 2.69 cyclone is used with standard 37-mm cassettes at a flowrate of 1.6 L/min. This sampler is listed in the NIOSH method for metalworking fluids.
THORACIC SAMPLERS: ANOTHER OPTION SKC offers an impaction based sampler for thoracic particulate called the Parallel Particle Impactor or PPI. The thoracic PPI is used with any suitable 37-mm filter at a flowrate of 2.0 L/min. SKC 225-386 U.S. Patent No. 7,073,402 Single-use, disposable model 225-386
PPI OPERATING PRINCIPLE The disposable PPI looks like a traditional 37-mm filter cassette. But the inlet section has 4 internal, pre-oiled impactor plates that scrub out larger particles. The dust size-fraction of interest is collected onto the filter in the outlet section for analysis.
THORACIC SAMPLERS CURRENT APPLICATIONS Thoracic TLVs Sulfuric Acid Cotton Dust NIOSH Methods NIOSH Method 5524, for metalworking fluids specifies a 2-um PTFE filter in a 37-mm filter cassette with an optional thoracic particulate sampler.
RESPIRABLE DUST: THE OSHA SILICA NPRM U.S. OSHA published their Notice of Proposed Rulemaking (NPRM) for Occupational Exposure to Respirable Crystalline Silica in September 2013. See this 757-page document at https://www.osha.gov/silica/nprm.pdfwww.osha.gov/silica/nprm
NOTABLE ISSUE IN THE NPRM: PELs-CURRENT GENERAL INDUSTRY A formula based on the % silica in the air sample. Example: _____10____ % Quartz + 2 PEL is equivalent to 100 ug/m 3 when the material is pure quartz. PEL approaches 5 mg/m 3, (the PEL for Particulates Not Otherwise Classified) with a low percentage of quartz in the sample.. CONSTRUCTION AND SHIPYARDS A formula based on obsolete method of collecting dust into impingers with analysis by particle counting. PEL is approximately equivalent to 250 ug/m 3.
NOTABLE CHANGE IN THE NPRM: PEL-PROPOSED 50 ug/m 3 as an 8-hr TWA for all forms of silica including quartz, cristobalite, and trydymite for all industry sectors covered by the rule. 25 ug/m 3 action level (same as current TLV)
NOTABLE ISSUE IN THE NPRM: SAMPLER SPECS-CURRENT Current specs for respirable dust samplers were promulgated in 1971 and are listed in 29 CFR 1910.1000; Table Z-3 for mineral dusts. Table Z-3 lists the required collection efficiencies of samplers for various particle sizes. Ex. Particles with a diameter of 3.5 um should be collected with 50% efficiency. (50% cut-point) The 25, 75, and 90% cut-points are also listed. The Dorr-Oliver (nylon) cyclone is the only sampler used by federal OSHA inspectors to meet these specs.
NOTABLE CHANGE IN THE NPRM: SAMPLER SPECS-PROPOSED Page 539: OSHA acknowledges that the current collection efficiency specs for samplers are obsolete. Page 542: OSHA states that crystalline silica measurement should be determined by a sampling device designed to meet the characteristics for particle- size-selective samplers specified in ISO 7708:1995 Air Quality-Particle Size Fraction Definitions for Health-Related Sampling.
ISO 7708:1995 This is the standard that ACGIH, NIOSH, CEN, and most countries around the world have already adopted. The collection efficiency curve for respirable dust samplers in this standard includes a 50% (median) cut-point of 4 um which is more conservative than the existing OSHA specification.
TRADITIONAL SAMPLERS: TO MEET SPECS IN ISO 7708 CYCLONES FROM SKC/FLOWRATES Aluminum Cyclone @ 2.5 L/min-Listed in NIOSH method. Published journal article. G(S)-3 Cyclone @ 2.75 L/min-Listed in OSHA NPRM on page 267. Published journal article.
TRADITIONAL SAMPLERS: TO MEET SPECS IN ISO 7708 OTHER CYCLONES /FLOWRATES Dorr-Oliver @ 1.7 L/min Listed in NIOSH method and NPRM Higgins-Dewell @ 2.2 L/min European cyclone; Listed in NIOSH method and NPRM BGI GK 2.69 @ 4.2 L/min Listed in NPRM
NEW SAMPLER OPTIONS Page 539: Adoption of this (ISO) definition by OSHA would allow for workplace sampling to be conducted using ANY particulate sampling device that conforms to the ISO definition i.e. collects dust according to the particle collection efficiency curve specified in the ISO standard.
RESPIRABLE PPI SAMPLERS FROM SKC Specifically designed to precisely match the criteria for respirable samplers specified in the ISO 7708 standard.
SKC RESPIRABLE PPI: FLOWRATE OPTIONS Single-use, disposable PPI models are available for use at either 2, 4, or 8 L/min. This provides flexibility in pump options, sample duration, and concentration. 4 L/min: 225-387 8 L/min: 225-384 2 L/min: 225-385
PPI DATA: OSHA DOCKET SKC submitted comments to the OSHA docket on the silica NPRM with data on the PPI. (Electronic copies are available). The data which was published in the Journal of Physics shows that the collection efficiency of the PPI is a close match to the ISO standard and the bias is more acceptable than the HD cyclone (listed in the NPRM.)
MEETING USER DEMANDS: CONVENIENCE Smaller size-fits under welding helmet or PPE No assembly of impaction substrates Pre-loaded with filters or lab loaded like a traditional cassette No cleaning after sampling
AND FINALLY… Another disposable size-selective sampler for diesel particulate. Particulate emissions from diesel exhaust are VERY small particles that rapidly clump together to form particles that are still submicron in size i.e. less than 1 um in aerodynamic diameter.
DPM SAMPLER EMERGES A single-use, disposable filter cassette for DPM was developed by U.S. NIOSH mining division and the technology was transferred to SKC for commercial production. SKC 225-317
DPM SAMPLING TRAIN Cyclone Removes non-respirable particles that may overload the filter Internal Impactor Plate in Cassette Removes respirable particles greater than 1.0 um in diameter Heat-treated Quartz Filter assembly Collects DPM particles less than 1.0 um in diameter for analysis of elemental carbon (EC).
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