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 Permissible Exposure Limits (PELs)  Time Weighted Average (TWA)  American Conference of Governmental Industrial Hygienist (ACGIH)  National Institute.

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Presentation on theme: " Permissible Exposure Limits (PELs)  Time Weighted Average (TWA)  American Conference of Governmental Industrial Hygienist (ACGIH)  National Institute."— Presentation transcript:

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2  Permissible Exposure Limits (PELs)  Time Weighted Average (TWA)  American Conference of Governmental Industrial Hygienist (ACGIH)  National Institute for Occupational Safety and Health (NIOSH)

3  Silicon + Oxygen = SiO 2  One of the most abundant compounds  Two Forms › Crystalline › Non-Crystalline  Found in nature as quartz

4  Non-Crystalline (amorphous)  Crystalline › Quartz › Crystobalite › Tridymite

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7  Glass  Filler for: › Paints › Plastics › Rubber  Fiber Optics

8 GGlass Workers CConstruction Work UUtility Work SSandblasting QQuartz Mining MMasonry Work DDemolition

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10  ~ 2.2 Million workers in the U.S. › 1,850,000 in Construction › 320,000 in General Industry/Maritime

11  Essentially non toxic › LD50 of 5,000 mg/kg  Silica Dust can lead to: › Silicosis › Bronchitis › Cancer

12  Disabling and sometime fatal lung disease with no current cure  Due to inhalation of silica dust  Characterized by: › Shortness of breath › Cough › Fever › Cyanosis (bluish skin) › Scaring in the lungs

13 https://www.youtube.com/watch?v=6FezczBUnI0

14 Typical Healthy Lungs Silica Exposure

15 Typical Healthy Lungs Silica Exposure

16  Acute vs Accelerated vs Chronic  Concentration  Duration  Particle Size

17  Develops after 1 to 3 years of exposure at a very high concentration  Symptoms may show as early as 7 months  Cough, weight loss, and extreme fatigue  Liquid in the alveoli  Fatal with in 2 years

18  Shorter exposure than Chronic, 5-15 years  Higher concentration  Progresses after employee is removed from the exposure source

19  Long term exposure, years, to develop  Dust with 10% or greater silica  Little to no symptoms for the first 20 years  Shortness of Breath, cough, fever  Bluish lips/ear lobes  Chest Pain

20  OSHA current standards adopted in 1971  OSHA had to promulgate PELs › 425 were created  Silica’s PEL was derived from › Walsh-Healy Public Contacts Act › Contract Work Hours & Safety Standard’s Act › ACGIH

21  In 1974 NIOSH recommended that the occupational exposure be controlled so that no worked is exposed to: › TWA greater than 50 µg/m 3  10 hour workday  40 hour work week

22  OSHA’s National Emphasis Program › NEP Launched 1/24/2008 › Included:  Compliance Enforcement  Consolation  Training and Outreach through the OSHA Web- site  Standard Development

23  General Industry › (Ventilation) › Table Z-3 (The Z Table)

24  Shipyard Industry › (Mechanical paint removal) › (The Z Table)

25  Construction Industry (Appendix A Dusts)  (Ventilation)

26  Current exposure limits › Adopted for decades ago  U.S. National Toxicology Program, International Agency for Research on Cancer, and NIOSH have identified respireable crystalline silica as a human carcinogen › PELs are difficult to understand › Based on older sampling methods › Shipyard workers PEL is 2x general industry

27  Two proposed standards: › One for General Industry/Maritime › One for Construction

28  OSHA estimates current lung cancer deaths from exposure to silica over a 45 year working life averages: › Between 13 – 60 General Industry deaths per 1,000 workers  average exposure is estimated to be ~ 100µg/m³ › Between 37 – 635 Construction & Shipyard deaths per 1,000 workers  Average exposure is estimated to be ~ between 250 – 500 µg/m³

29  Supreme Court: “significant risks are present and can be eliminated or lessened by a change in practices” before promulgating any health or safety standard.  After standard implemented: › Estimate between 6 – 26 deaths per 1,000 workers.

30  Current Permissible Exposures Limits (PELs) are formulas that many find hard to understand: › PEL (respirable fraction) = 10 ÷ [% quartz + (% cristobalite × 2) + (% tridymite × 2) + 2] › PEL (total dust) = 30 ÷ [% quartz + (% cristobalite × 2) + (% tridymite × 2) + 2]

31  Constriction/shipyard PELs are obsolete particle count limits  Construction/Shipyard formulas are about 250 µg/m 3  General Industry formula is equal to about 100 µg/m 3

32  Canada › Alberta – 25 µg/m 3 › Nova Scotia – 25 µg/m 3 › Saskatchewan – 50 µg/m 3  Italy 25 - µg/m 3  Ireland – 50 µg/m 3  Netherlands – 75 µg/m 3

33  Establishes new PEL of 50 μg/m3 = 0.05 mg/m³  Includes provisions for:  Measuring worker exposures to silica;  Limiting access to areas where workers could be exposed above the PEL;  Use of dust controls;  Use of respirators when necessary;  Medical exams for highly exposed workers;  Worker training;  Recordkeeping.

34  Conduct an initial exposure assessment › This will determine if:  EE’s are exposed to Silica levels at or above the action level  Whether or not engineering/administrative practices are required to reach the PEL  Determine if periodic or additional monitoring will be needed

35  NIOSH Method 7500  -154/pdfs/7500.pdf

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39  Use engineering controls and work practices to maintain exposure levels at/or below the PEL  If the employer can show that engineering controls are not feasible: › Attempt to reduce the exposure to the lowest achievable level › Supplement with PPE

40  If blasting, use alternative media  Ventilation  Wet Method  PPE

41  What are we doing? › Monitoring the “situation” › Gathering information  Historical Sampling Data  Field Interviews › Preparing for NEAs

42  OSHA › https://www.osha.gov/dsg/topics/silicacryst alline/additional_info_silica.html https://www.osha.gov/dsg/topics/silicacryst alline/additional_info_silica.html  NIOSH › ml ml

43  Thank you for your attention and time.  Jon Nixon  CenterPoint Energy 


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