ih&s 725 dr. myers, c.i.h. compliance statistics lecture notes
TRANSCRIPT
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IH&S 725 Dr. Myers, C.I.H.
Compliance statistics
Lecture Notes
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IH&S 725 Dr. Myers C.I.H.
Data Interpretation
Statistics for compliance
Descriptive statistics
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IH&S 725 Dr. Myers C.I.H.
Compliance and Non-compliance
OELLCL
UCL
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IH&S 725 Dr. Myers C.I.H.
Approaches to the compliance decision
Classical confidence interval approach NIOSH “standardized concentration”
approach with CVT OSHA “standardized concentration”
approach with SAE – standard analytical errors
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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/m3
Would this worker’s exposure be considered to be non-compliant with the OSHA lead standard 1910.1025?
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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
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IH&S 725 Dr. Myers C.I.H.
Classical confidence interval approach
CI step 2: Determine the relative standard deviation on the sample.
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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
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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
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IH&S 725 Dr. Myers C.I.H.
NIOSH “standardization” approach
NIOSH step 1: Calculate a “standardized” concentration x
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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:
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IH&S 725 Dr. Myers C.I.H.
NIOSH “standardization” approach
NIOSH step 3: Calculate the LCL
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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
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IH&S 725 Dr. Myers C.I.H.
OSHA “standardized concentration” approach with SAE
OSHA step 1: Calculate a “standardized” concentration Y
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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
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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
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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
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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:
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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: 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?
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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
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IH&S 725 Dr. Myers C.I.H.
Full period equal true average exposures
Calculate the TWA and the standardized concentration.
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IH&S 725 Dr. Myers C.I.H.
Full period equal true average exposures
Calculate the appropriate 95% CI.
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IH&S 725 Dr. Myers C.I.H.
Full period equal true average exposures
Calculate the appropriate 95% LCL.
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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 Manual
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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: 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?
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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
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IH&S 725 Dr. Myers C.I.H.
Full period non-equal true average exposures
Calculate the TWA and the standardized concentration.
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IH&S 725 Dr. Myers C.I.H.
Full period non-equal true average exposures
Calculate the appropriate 95% CI.
2
T21
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22
21
21
T,1CV 1....OEL
....CV CI %95
n
nn
TTT
TXTXTXtx
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IH&S 725 Dr. Myers C.I.H.
Full period non-equal true average exposures
Calculate the appropriate 95% UCL.
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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
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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
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IH&S 725 Dr. Myers C.I.H.
Partial period consecutive samples
Decision criteria – limited to non-compliance only:
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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: 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?
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IH&S 725 Dr. Myers C.I.H.
Partial period consecutive samples example solution
Determine TWA concentration
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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
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IH&S 725 Dr. Myers C.I.H.
Partial period consecutive samples example solution
Calculate the appropriate confidence limit
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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