Use of measurement uncertainty in compliance assessment

1. Use of measurement uncertainty in compliance assessment Maria Belli National Environmental Protection Institute (ISPRA)

2. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale ISPRA Since 22 August 2008 APAT, ICRAM and INFS have been joined in a new Institute named Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA)

3. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Commission Directive laying down, pursuant to Directive 2000/60/EC of the European Parliament and of the Council, technical specifications for chemical analysis and monitoring of water status Recalls: EN ISO 17025 for method validation • all methods should meet certain minimum performance criteria, including rules on the uncertainty of measurements and on the limit of quantification of the methods

4. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Commission Directive (measurement uncertainty definition) • 'uncertainty of measurement' means a non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used.

5. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Commission Directive (Minimum performance criteria for methods of analysis) minimum performance criteria for all methods of analysis applied are based on an uncertainty of measurement of 50% or below (k = 2) estimated at the level of relevant environmental quality standards .............

6. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Measurement uncertainty & compliance • Measurement results are mainly used to assess compliance with a regulation • Specifications generally give only an upper limit on the amount of contaminant that is allowed • For measurement results close to the limit • Because MU characterizes the dispersion….It is only possible to give the probability that the amount of contaminant is above or below the limit

7. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Measurement uncertainty & compliance 1 2 3 limit 4 In the cases 2 and 3 it is only possible to establish the probability that the values are above or below the limit. The probability normally chosen to build an acceptance or a rejection zone are 95% or 99%

8. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Measurement uncertainty & compliance. What is needed • A valid result with its uncertainty • A specification of an upper/lower limit • A decision rule describing how the MU is taken into account • A range of results (derived from the decision rule) which leads to the acceptance or the rejection when the results are in the appropriate zone

9. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Measurement uncertainty & compliance. References • Guidelines for Decision Rules: Considering Measurement Uncertainty in Determining Conformance with Specifications ASME (New York) 2001 • EURACHEM/CITAC Guide ‘‘Use of uncertainty information in compliance assessment’’ • ILAC G8:03/2009 “Compliance with Specification”

10. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Measurement uncertainty & compliance COMMISSION REGULATION (EC) No 333/2007 • laying down the methods of sampling and analysis for the official control of the levels of lead, cadmium, mercury, inorganic tin, 3-MCPD and benzo(a)pyrene in foodstuffs Acceptance criteria The lot or sublot is accepted if the analytical result of the laboratory sample does not exceed the respective maximum level as laid down in Regulation (EC) No 1881/2006 taking into account the expanded measurement uncertainty and correction of the result for recovery if an extraction step has been applied in the analytical method used

11. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Measurement uncertainty & compliance COMMISSION REGULATION (EC) No 1883/2006 laying down methods of sampling and analysis for the official control of levels of dioxins and dioxin-like PCBs in certain foodstuffs Acceptance criteria • by calculating the expanded uncertainty, using a coverage factor of 2 which gives a level of confidence of approximately 95 %. A lot or sublot is non-compliant if the measured value minus U is above the established permitted level. In case of a separate determination of dioxins and dioxin-like-PCBs the sum of the estimated expanded uncertainty of the separate analytical results of dioxins and dioxin-like PCBs has to be used for the sum of dioxins and dioxin-like PCBs, • by establishing the decision limit (CCα) according to the provisions of Commission Decision 2002/657/EC of 12 August 2002 implementing Council Directive 96/23/EC concerning the performance of analytical methods and the interpretation of results (4) (point 3.1.2.5 of the Annex the case of substances with established permitted level) a lot or sublot is non-compliant if the measured value is equal to or above the CCα.

12. ISPRA - Istituto Superiore per la Protezione e la Ricerca Ambientale Proposal for the 2010-2012 program of CMA To establish a working group to elaborate a document on the decision rules that should be applied in the frame of WFD

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