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.