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

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Presentation on theme: "IH&S 725 Dr. Myers, C.I.H. Compliance statistics Lecture Notes."— Presentation transcript:

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

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

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

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

5 IH&S 725 Dr. Myers C.I.H. 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/m 3 Would this worker’s exposure be considered to be non-compliant with the OSHA lead standard ?

6 IH&S 725 Dr. Myers C.I.H. 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

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

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

9 IH&S 725 Dr. Myers C.I.H. 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

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

11 IH&S 725 Dr. Myers C.I.H. 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:

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

13 IH&S 725 Dr. Myers C.I.H. 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

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

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

16 IH&S 725 Dr. Myers C.I.H. 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

17 IH&S 725 Dr. Myers C.I.H. 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

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

19 IH&S 725 Dr. Myers C.I.H. 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: X 1 = mg/m 3 ; X 2 = mg/m 3 ; and X 3 =0.049 mg/m 3. You sampling times are: T 1 = 100 minutes; T 2 = 250 minutes; and T 3 = 100 minutes. Is this worker’s exposure in compliance?

20 IH&S 725 Dr. Myers C.I.H. 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

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

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

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

24 IH&S 725 Dr. Myers C.I.H. 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 ManualNIOSH Sampling Strategies Manual

25 IH&S 725 Dr. Myers C.I.H. 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: X 1 = mg/m 3 ; X 2 = mg/m 3 ; and X 3 =0.02 mg/m 3. You sampling times are: T 1 = 90 minutes; T 2 = 240 minutes; and T 3 = 120 minutes. Is this worker’s exposure in compliance?

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

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

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

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

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

31 IH&S 725 Dr. Myers C.I.H. 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

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

33 IH&S 725 Dr. Myers C.I.H. 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: X 1 = 0.11 mg/m 3 ; X 2 = mg/m 3 ; and X 3 =0.087 mg/m 3. You sampling times are: T 1 = 100 minutes; T 2 = 120 minutes; and T 3 = 90 minutes. Is this worker’s exposure in compliance?

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

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

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

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


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