Presentation is loading. Please wait.

Presentation is loading. Please wait.

RESPIRABLE CRYSTALLINE SILICA

Similar presentations


Presentation on theme: "RESPIRABLE CRYSTALLINE SILICA"— Presentation transcript:

1 RESPIRABLE CRYSTALLINE SILICA
New Considerations for Sampling and Analysis

2 SILICA IS A TOPIC IN THE U.S.
HOT SKC INC. is pleased to share the latest updates.

3 BUT FIRST CONSIDER: SILICA THE COMPUND
Look at chemical formula for silica (SiO2), and consider this: Oxygen is the most abundant element in the Earth’s crust and silicon is the second most abundant. Quartz, the most common form of crystalline silica, is the second most common mineral on the earth’s surface. Amorphous silica such as diatomaceous earth is not particularly toxic to humans unless heated to high temperatures.

4 CRYSTALLINE SILICA: WHERE ITS FOUND
Crystalline silica is naturally occurring in sand, gravel, and mineral ores. Quartz, the most common form, is found in almost every type of rock. Nearly all mining and quarrying activities involve exposures to crystalline silica.

5 CRYSTALLINE SILICA: WHERE ITS USED
Due to its chemical and physical properties, crystalline silica is a prized mineral with a number of industrial applications. Major ingredient in building materials such as concrete, bricks, and stone Used as a molding material for metal casting in foundries. Filler in plastics, rubber, and paint. Raw material for glass manufacture along with porcelain and fine china.

6 APPLICATION IN THE HEADLINES: FRACKING
Silica sand is used to hold open the fissures created by hydraulic fracturing (fracking) so natural gas or oil can flow out of the shale and into the well.

7 CRYSTALLINE SILICA: WORKPLACE EXPOSURES
U.S. OSHA reports that 2.2 million workers are exposed to respirable crystalline silica. The majority (1.85 million) are in the construction industry. Exposures occur when workers cut, grind, crush, or drill silica-containing materials.

8 CRYSTALLINE SILICA: WORKPLACE EXPOSURES
High Risk Jobs: Abrasive blasting Foundry work Stonecutting Rock Drilling Mining Tunneling Hydraulic Fracturing

9 NEW PROPOSED RULE FROM U.S. OSHA
In September 2013, U.S. OSHA published a Notice of Proposed Rulemaking (NPRM) for Occupational Exposure to Respirable Crystalline Silica. This is the first update since the original Permissible Exposure Limit (PEL) was adopted in 1971. See this 757-page document at https://www.osha.gov/silica/nprm.pdf In September 2013, federal OSHA published the long-awaited Notice of Proposed Rulemaking for respirable crystalline silica. You can see this 757-page document at the URL shown on the slide. During the holidays, I did a quick scan of the entire document and picked out THREE key pages that impact sampling. I did a lab mailing and included these 3 pages. Beth has a copy. In general, however, the proposed rulemaking is very good news for SKC.

10 SUMMARY OF ISSUES IN THE NPRM AFFECTING SAMPLING & ANALYSIS
New Permissible Exposure Limit New Specifications for Respirable Dust Samplers Guidance on Sample Times required to exceed limit of quantification at the proposed levels Guidance on Analytical Methods that are sensitive enough to measure silica at proposed levels

11 PERMISSIBLE EXPOSURE LIMIT: EXISTING
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/m3. GENERAL INDUSTRY A formula based on the % silica in the air sample. Example: _____10____ % Quartz + 2 PEL is equivalent to 100 ug/m3 when the material is pure quartz . PEL approaches 5 mg/m3, (the PEL for Particulates Not Otherwise Classified) with a low percentage of quartz in the sample. . So let’s go through the notable changes that will affect exposure assessments. The first notable change is in the Permissible Exposure Limits. The current OSHA PEL for GENERAL INDUSTRY is not just a number. The PEL must be CALCULATED each time based on the % silica in the air sample. Adding to the hassle, there will be a different PEL for each type of silica in the sample such as quartz, cristobalite, and tridymite.

12 PERMISSIBLE EXPOSURE LIMIT: PROPOSED
50 ug/m3 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/m3 action level (same as current TLV) You may be surprised to learn that the federal OSHA PEL for respirable crystalline silica in construction and shipyards industy is DIFFERENT than the PEL for general industry. Amazingly, the PEL for construction and shipyards is based on particle counting in impinger solutions. This is obsolete and few labs offer the analysis. The PEL for these industries is now equivalent to 250 ug/m3, more than twice that of general industry. The new proposed PEL will be the same in all industries.

13 SPECIFICATIONS FOR SAMPLERS: EXISTING
Existing specs for respirable dust samplers were promulgated in 1971 and are listed in 29 CFR ; Table Z-3 for mineral dusts. A respirable dust sampler with a 50% (median) cut-point of 3.5 um is specified. The Dorr-Oliver (nylon) cyclone is the only sampler used by federal OSHA inspectors to meet the existing specifications. The second notable changes in the silica rule is the specifications for samplers. Based on the 1971 standard published in the Code of Federal Regulations, federal OSHA inspectors can use only the Dorr-Oliver cyclone at 1.7 L/min or an exact equivalent to achieve a collection efficiency curve with a 50% or median cut point of 3.5 um. Now, OSHA has moved away from specifying a sampler by name and has instead moved to a performance based standard.

14 U.S. OSHA IS TRYING TO UPDATE TO CURRENT AEROSOL SCIENCE
Page 539: OSHA acknowledges that the existing collection efficiency specifications for respirable dust samplers (50% cut-point of 3.5 um) 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.

15 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 of 3.5 um. SKC has never mentioned the ISO standard by number in the past. So please be sure you recognize this standard number if customers contact you: ISO 7708. This is what SKC has referred to previously as the ISO/CEN/ACGIH curve. This is the collection efficiency curve followed by most countries in the world and NIOSH in the US. This collection efficiency curve for respirable dust samplers has a 50% cut-point of 4 microns.

16 RESPIRABLE DUST SAMPLERS: TO MEET ISO 7708 SPECIFICATIONS
OPTION #1: TRADITIONAL CYCLONES

17 CYCLONE SAMPLERS: TO MEET SPECS IN ISO 7708
NYLON DORR- OLIVER CYCLONE: Listed in OSHA SILICA NPRM on page 267 Listed in NIOSH respirable dust methods Designated flow rate is 1.7 L/min (same as that used for previous criteria?) On this slide, you can see the cyclones available from our competitors along with government listings of each. Review each

18 DORR-OLIVER CYCLONE ADVANTAGES AND DISADVANTAGES
Advantage: Long history of use in the U.S. by compliance officers. Disadvantage: Nylon construction creates static electricity concerns. Disadvantage: Orientation bias. (AIHA Journal 56, November 1995). Disadvantage: Dust sticks to cassette top with closed-face operation. (ASTM, STP 1565, 2013) A BETTER WAY?

19 CYCLONE SAMPLERS: TO MEET SPECS IN ISO 7708
SKC ALUMINUM CYCLONE: Listed in NIOSH respirable dust methods Published performance (J. Aerosol Science, 29, 1998). Designated flow rate is 2.5 L/min Shown on this slide are the SKC respirable dust cyclones, flowrates, and data sources or listings in government methods and rulemakings. To meet the specifications of ISO 7708 as specified by OSHA, the SKC aluminum cyclone should be operated at 2.5 L/min. SKC has the following evidence that the cyclone meets the requirements: Listed as an option in NIOSH methods. Published journal article. SKC

20 ALUMINUM CYCLONE ADVANTAGES AND DISADVANTAGES
Metal construction eliminates static electricity concerns. Open-face sample collection enhances collection. Calibration adapter offers user convenience. DISADVANTAGE Aluminum can not be used in underground mines due to spark hazard. Users frequently make the mistake of removing the red cap (grit pot) on the cyclone during sampling.

21 CYCLONE SAMPLERS: TO MEET SPECS IN ISO 7708
SKC G(S)-3: Listed in OSHA SILICA NPRM on page 267 Published performance (J. Aerosol Science, 28, 1997). Designated flow rate is 2.75 L/min . SKC

22 GS-3 CYCLONE ADVANTAGES AND DISADVANTAGES
Designed to overcome orientation bias of Dorr-Oliver Conductive plastic construction eliminates static electricity concerns. Not a spark hazard for underground mines. Open-face sample collection enhances collection. DISADVANTAGES No calibration adapter like with aluminum cyclone. Requires calibration jar or the easier jarless calibration methods.

23 CYCLONE SAMPLERS: TO MEET SPECS IN ISO 7708
BGI GK 2.69 Listed in OSHA SILICA NPRM on page 267 Designated flow rate is 4.2 L/min Now available from SKC as or -25 for 25-mm version.

24 BGI GK 2.69 CYCLONE ADVANTAGES AND DISADVANTAGES
Metal construction eliminates static electricity concerns. Higher flow of 4.2 L/min allows users to sample only 4 hours to collect enough sample for quantitative analysis of even cristobalite at the action level. DISADVANTAGES May not be suitable for use in underground mines. No calibration adapter like with aluminum cyclone.

25 IMPORTANT NOTE ON FLOWRATE
All cyclones are not created equal! Each cyclone has different operating specifications and performance criteria. Be sure you know the flow rate specified to achieve the desired cut-point before using any cyclone.

26 TECH TIP: CASSETTE MATERIAL
In a March 2013 JOEH article by NIOSH, cassette wall losses were noted when using cyclones with typical cassettes made of styrene*. NIOSH recommends the use of 37-mm black conductive cassettes made of polypropylene. *Ashley & Harper (2013) Analytical Performance Issues, Journal of Occupational and Environmental Hygiene, 10:3.

27 RESPIRABLE DUST SAMPLERS: TO MEET ISO 7708 SPECIFICATIONS
NEW OPTIONS

28 NEW SAMPLERS: TO MEET SPECS IN ISO 7708
Page 539 of OSHA SILICA NPRM states: 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. The best news is that the OSHA standard does NOT limit samplers to CYCLONES. Page 539 states… Beth has a copy of page 539 or print one yourself from the link I gave you. I wrote a letter to the OSHA docket for SKC supporting verbiage that allows use of ANY sampler and discouraging the use of only cyclones.

29 NEW SKC SAMPLERS: TO MEET SPECS IN ISO 7708
Impaction based PPI samplers also available for respirable dust. Designed to precisely match the ISO/CEN/ACGIH/NIOSH criteria. Available in reusable or disposable options.

30 SKC RESPIRABLE PPI: FLOWRATE OPTIONS
Single-use, disposable PPI models are available for use at either 2, 4, or 8 L/min. Available empty or pre-loaded with filters. A calibration adapter is available for disposable models. 2 L/min: 8 L/min: 4 L/min:

31 WHY THE HIGHER FLOW RATE RESPIRABLE PPI SAMPLERS?
NIOSH reported that for a working environment with an airborne concentration of respirable silica near the current TLV of 25 ug/m3, the amount of sample collected with current respirable dust samplers (at typical flow rates of 2 L/min ) might not be enough for quantitative analysis. (Harper, et. al. Ann. Occup. Hyg., 2010.) So having solved that problem, let’s move on to the issue of ENHANCED SENSITIVITY for compounds like respirable crystalline silica that have a very low exposure limits or guidelines. .

32 PUMP PARTNERS: HIGH FLOW PPI SAMPLERS
Respirable PPI 4 L/min model can be partnered with SKC XR5000. 8 L/min model can be partnered with the SKC Leland Legacy pump. To solve this problem, a PPI was developed by SKC that matched the respirable convention at 8L/min. Read second bullet.

33 PPI SAMPLER PERFORMANCE COMPARED TO CRITERIA

34 PPI DATA: OSHA DOCKET SKC submitted comments to the OSHA
docket on the silica NPRM with data on the PPI. (Electronic copies are available upon request). 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.) In my submission to the OSHA docket, I also sent data on the PPI documenting the fact that these samplers met the ISO 7708 standard. OSHA would only accept data that was published in a a peer reviewed journal and Saulius had previously done this. The data was published in the Journal of Physics. I have that journal article available electronically upon request. The data on the PPI was “prettier” than that of the Higgins-Dewell cyclone that is listed by name as being acceptable in the OSHA proposal.

35 SAMPLE TIMES REQUIRED FOR QUANTIFICATION BY LAB
4+ HOURS PER OSHA NPRM Using respirable dust samplers at flows of approx. 2-4 L/min in workplace concentrations of quartz down to the proposed action level of 25 ug/m3. (TLV levels) 2+ HOURS PER SKC SCIENTISTS Using respirable dust samplers at flows of 8 L/min at these same workplace concentrations.

36 ANALYTICAL METHODS: SENSITIVITY CONCERNS
U.S. OSHA concluded that both X-Ray diffraction (XRD) and Infrared Spectroscopy (IR) methods are sensitive enough to quantify silica in workplace concentrations at the proposed PEL and action levels. (But precision is lacking at 25 ug/m3) Visible absorption spectrophometry (VIS) methods are NOT sensitive enough.

37 THANK YOU FOR YOUR ATTENTION!


Download ppt "RESPIRABLE CRYSTALLINE SILICA"

Similar presentations


Ads by Google