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Ambient Air Ambient Air Sampling for Particulate MatterSampling for Particulate Matter Robert W. VanderpoolRobert W. Vanderpool Human Exposure and Atmospheric Sciences Human Exposure and Atmospheric Sciences DivisionDivision Office of Research Office of Research and Developmentand Development UUUU..SSSS. Envir. Enviroooonmnmeeeenntatatatal Prl Protectotectotectotectiioooon An Agggegeeenncccycyyy Research Triangle Research Triangle Park, Park, NCNC AgriculturalAgriculturalAgriculturalAgricultural AirAirAirAir QQQualityQualityualityuality TTTaskTaskaskask ForceForceForceForce MeetingMeetingMeetingMeeting September 30, September 30, 20102010 Presentation Outline Background and statement of issues Characteristics of ambient aerosols (sources, size ranges, definitions of MMD, GSD, aerodynamic diameter) SizeSize-selectiveselective mmeasurementeasurement techniquestechniques ((inertialinertial impactorsimpactors aandnd cyclones, definitions of cutpoint and slope) DevelopmentDevelopment ofof healthhealth-basedbased PMPM standardsstandards – physiologicalphysiological basis for PM sampling conventions EPA’s method development for PM and PM 10 2.5 Review of TAMU’s methodology for estimating “True” PM concentrations, and for estimating “oversampling” of EPA reference methods Backgground To protect public health, the EPA has developed national ambient air quality standardsstandards (NAAQS)(NAAQS) forfor airborneairborne particulateparticulate mattermatter (PM)(PM). ComplianceCompliance withwith thethe PM NAAQS must be measured using EPA-approved samplers which were developed to accurately measure PM concentrations independent of wind speed and direction. FRM development was thoroughly peer-reviewed and independent evaluations of FRMs have validated their size-selective performanceperformance. The agricultural industry typically generates airborne PM with much larger mass median diameters (MMDs) than urban dusts, and has expressed the beliefbelief tthathat certaincertain agriculturalagricultural operationsoperations areare bbeingeing overover--regulatedregulated byby EPAEPA duedue to an over-estimation of PM emissions from these operations. In particular, the industry has stated that “…all EPA-approved federal referenreferencece methodmethod (FRM)(FRM) samplerssamplers dodo notnot accuaccuratelratelyy measuremeasure PMPM concentrations in the presence of the large PM that is typical of PM emitted by agricultural operations. The term for this phenomenon is “over-sampling”.” These “over-samppgling” statements are directed towards source samppgling methods (i.e., in-stack) as well as ambient sampling methods. Background (cont) Representatives of the agricultural industry have conducted their own laboratory and field evaluations of EPA’s PM and PM FRM and have stated 2.5 10 thatthat thesethese FRMsFRMs overover-samplsamplee byby aa ffactoractor ofof 1.51.5 ttoo 1100 ((i.e.,i.e., 150%150% toto 1000%1000% overover- sampling). Similar statements have been made regarding sampling of PM aerosols. 2.5 The aggyricultural industry ppostulates that the mechanism for this over-samppgling is the change in the sampler’s size selective performance (i.e., cutpoint and slope) in the presence of large agricultural dusts. EPA has thoroughly examined these statements and does not agree with the ffunddamenttall bbasiis ffor tthhese sttattementts, ththe meththoddollogy upon whihichh ththe statements were based, nor the conclusions drawn from this research. During previous discussions, EPA and agricultural research staff have acknowlacknowledgededged thatthat thesethese areare complexcomplex technicaltechnical issuesissues. EPAEPA researchresearch staffstaff appreciates the critical importance of accurately regulating the agricultural industry, and also for ensuring that public health is protected with an adequate margin of safety.
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