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Compliance statistics

Compliance statistics. Lecture Notes. Data Interpretation. Statistics for compliance Descriptive statistics. LCL. OEL. UCL. Compliance and Non-compliance. Approaches to the compliance decision. Classical confidence interval approach NIOSH “standardized concentration” approach with CV T

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Compliance statistics

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  1. Compliance statistics Lecture Notes IH&S 725 Dr. Myers, C.I.H.

  2. Data Interpretation • Statistics for compliance • Descriptive statistics IH&S 725 Dr. Myers C.I.H.

  3. LCL OEL UCL Compliance and Non-compliance IH&S 725 Dr. Myers C.I.H.

  4. Approaches to the compliance decision • Classical confidence interval approach • NIOSH “standardized concentration” approach with CVT • OSHA “standardized concentration” approach with SAE – standard analytical errors IH&S 725 Dr. Myers C.I.H.

  5. Full period single sample strategy • Example: An IH collects a lead sample to evaluate the worker’s exposure for compliance purposes. The concentration he measures is 55 ug/m3 • Would this worker’s exposure be considered to be non-compliant with the OSHA lead standard 1910.1025? IH&S 725 Dr. Myers C.I.H.

  6. Classical confidence interval approach • CL step 1: If the “8-hr” TWA value is less then the PEL determine the UCL else determine the LCL IH&S 725 Dr. Myers C.I.H.

  7. Classical confidence interval approach • CI step 2: Determine the relative standard deviation on the sample. IH&S 725 Dr. Myers C.I.H.

  8. Classical confidence interval approach • CI step 3: Determine the one-sided CL we’ll need and calculate IH&S 725 Dr. Myers C.I.H.

  9. Classical confidence interval approach • CI step 4: Compare PEL value and CI to determine compliance decision • Since the 95% LCL is less than the PEL conclude no decision IH&S 725 Dr. Myers C.I.H.

  10. NIOSH “standardization” approach • NIOSH step 1: Calculate a “standardized” concentration x IH&S 725 Dr. Myers C.I.H.

  11. NIOSH “standardization” approach • NIOSH step 2: If x is less than 1 calculate UCL else calculate LCL where the UCL and LCL are defined as: IH&S 725 Dr. Myers C.I.H.

  12. NIOSH “standardization” approach • NIOSH step 3: Calculate the LCL IH&S 725 Dr. Myers C.I.H.

  13. NIOSH “standardization” approach • NIOSH step 4: Compare standardized concentration and CI to determine compliance decision • Since the 95% LCL is less than 1 conclude no decision IH&S 725 Dr. Myers C.I.H.

  14. OSHA “standardized concentration” approach with SAE • OSHA step 1: Calculate a “standardized” concentration Y IH&S 725 Dr. Myers C.I.H.

  15. OSHA “standardized concentration” approach with SAE • OSHA step 2: If Y is less than 1 calculate UCL else calculate LCL IH&S 725 Dr. Myers C.I.H.

  16. OSHA “standardized concentration” approach with SAE • OSHA step 3: find the SAE and calculate the LCL. From OSHA method ID 121 the SAE is given as 0.14 IH&S 725 Dr. Myers C.I.H.

  17. OSHA “standardized concentration” approach with SAE • OSHA step 4: Compare standardized concentration and CI to determine compliance decision • Since the 95% LCL is less than 1 conclude no decision IH&S 725 Dr. Myers C.I.H.

  18. Full period consecutive samples • How do we handle consecutive samples? • Before we can answer the question we need to determine if: IH&S 725 Dr. Myers C.I.H.

  19. Full period equal true average exposures • During the course of an eight hour work shift you collect 3 lead samples. The lab using NIOSH method 7082 reports back to you the following results: X1= 0.055 mg/m3; X2 = 0.064 mg/m3; and X3 =0.049 mg/m3. You sampling times are: T1= 100 minutes; T2= 250 minutes; and T3= 100 minutes. • Is this worker’s exposure in compliance? IH&S 725 Dr. Myers C.I.H.

  20. Full period equal true average exposures • Process steps • Determine the TWA concentration • Calculate the standardized concentration • Calculate the appropriate 95% confidence interval • Make a decision about exposure compliance IH&S 725 Dr. Myers C.I.H.

  21. Full period equal true average exposures • Calculate the TWA and the standardized concentration. IH&S 725 Dr. Myers C.I.H.

  22. Full period equal true average exposures • Calculate the appropriate 95% CI. IH&S 725 Dr. Myers C.I.H.

  23. Full period equal true average exposures • Calculate the appropriate 95% LCL. IH&S 725 Dr. Myers C.I.H.

  24. Full period equal true average exposures • Make our compliance decision • Since the LCL>1 conclude an overexposure condition • How in this case did we reach a decision of “non-compliance” and in the previous example involving a single full period sample we concluded “no decision” • The answer “sample number” • NIOSH Sampling Strategies Manual IH&S 725 Dr. Myers C.I.H.

  25. Full period non-equal true average exposures • During the course of an eight hour work shift you collect 3 lead samples. You know the workers job is highly varied in task activity and duration and production rate. As a result you believe the true average exposures from your three sampling periods are non-uniform. Using NIOSH method 7082 you obtain the following results: X1= 0.015 mg/m3; X2 = 0.045 mg/m3; and X3 =0.02 mg/m3. You sampling times are: T1= 90 minutes; T2= 240 minutes; and T3= 120 minutes. • Is this worker’s exposure in compliance? IH&S 725 Dr. Myers C.I.H.

  26. Full period non-equal true average exposures • Process steps same a before but calculation of the CI more involved IH&S 725 Dr. Myers C.I.H.

  27. Full period non-equal true average exposures • Calculate the TWA and the standardized concentration. IH&S 725 Dr. Myers C.I.H.

  28. Full period non-equal true average exposures • Calculate the appropriate 95% CI. IH&S 725 Dr. Myers C.I.H.

  29. Full period non-equal true average exposures • Calculate the appropriate 95% UCL. IH&S 725 Dr. Myers C.I.H.

  30. Full period non-equal true average exposures • Make our compliance decision • Since the UCL<1 conclude no overexposure condition IH&S 725 Dr. Myers C.I.H.

  31. Partial period consecutive samples • Handled as the full period consecutive sample except that the evaluation point to determine compliance is no longer 1. • The partial period criteria (PPC) is IH&S 725 Dr. Myers C.I.H.

  32. Partial period consecutive samples • Decision criteria – limited to non-compliance only: IH&S 725 Dr. Myers C.I.H.

  33. Partial period consecutive samples example • During the course of an eight hour work shift you collect 3 lead samples. The workers job task activity and duration and production rate are fairly consistent. Using NIOSH method 7082 you obtain the following results: X1= 0.11 mg/m3; X2 = 0.068 mg/m3; and X3 =0.087 mg/m3. You sampling times are: T1= 100 minutes; T2= 120 minutes; and T3= 90 minutes. • Is this worker’s exposure in compliance? IH&S 725 Dr. Myers C.I.H.

  34. Partial period consecutive samples example solution • Determine TWA concentration IH&S 725 Dr. Myers C.I.H.

  35. Partial period consecutive samples example solution • Calculate standardized concentration and the PPC to determine the confidence interval to calculate IH&S 725 Dr. Myers C.I.H.

  36. Partial period consecutive samples example solution • Calculate the appropriate confidence limit IH&S 725 Dr. Myers C.I.H.

  37. Partial period consecutive samples example solution • Since x > PPC and the 95% LCL = 1.65 which is > PPC = 1.54 conclude over exposure IH&S 725 Dr. Myers C.I.H.

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