Review of the Air Quality Criteria Document for Particulate Matter

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Philip Hopke, PhDGuiding PrinciplesThere are two major questions facing EPA with respect to PM standards. First, they cannot haveboth a PM 10 and a PM 2.5 standard. There can be one or the other. Thus, what science isavailable to help make this choice. One suspects that the answer is that there is more scientificsupport for a PM 2.5 standard.This leads to the second issue: Should there be a standard for larger particle sizes? If so, whatshould be the indicator, concentration, averaging times, and statistical form of the standard?Thus, there needs to be a clear summary of the science that is or is not available to answer thesequestionsThe current document is much too diffuse in its focus and fails to provide enough real evaluationto provide clear statements of what is and is not know about the health and welfare effects ofvarious components of the ambient aerosol.Chapter 2Page 2-2, Lines 9-15: Complements on the good definitions.Page 2-13, Line13, Prior to 1987 (not 1997)Page 2-17, lines 2 to 15, There needs to be discussions of the nucleation events that are beingobserved by several groups (O’Dowd; Kulmala) of nucleation events. Most have been reportedfor remote areas like Macehead and Hyytila, but Kulmala has indicated to me that they have seensuch events in Helsinki and it may be that McMurry has also seen them in Atlanta. Thus,homogeneous nucleation can be an important process for new particle formation although thedetails need to be investigated.Page 2-18, lines 1 to 7: Kulmala suggests that ternary nucleation with NH 3 along with sulfuricacid and water is necessary to observe nucleation events. This is mentioned in their Naturearticle from last year. I can provide other references if needed.Page 2-72, lines 7-12: The CASAC Subcommittee on Particle Monitoring has raised questionsabout the process of demonstrating equivalency for continuous monitors and the need to greaterflexibility in bringing new technology into the compliance monitoring program. There needs tobe some recognition of these problems here.Page 2-72, lines 14-23: The 1996 CASAC PM Monitoring Subcommittee recommended aperformance standard rather than a design standard. The fact that EPA made the PM 10 criteriatoo loose does not mean that a performance standard would not work. It would not be as stiflingon technology development.The discussion fails to really highlight the fact that the FRM provides high precisionmeasurements of totally unknown accuracy with respect to airborne particle mass concentration.It is time to face the need to really define what you want to measure and it should not simply beduplicating measurements made with dichotomous samplers that have now been discredited asbeing adequate for measurement of PM 2.5 . The whole FRM program is full of contradictions andfalse assertions.The discussion fails to discuss the need to greater time resolution in mass measurements. Rightnow we have no idea what the proper time interval is for setting a standard. We use 24 hoursbecause that is what has been measured, but this interval has no basis in health effects.A - 1
Page 2-77, line 19-22: Should mention new developments in Synchotron XRF. It appears tohave much higher sensitivity that will permit much higher time resolution.Page 2-81, lines 5 and 6: The uncertainties in the reported slope and intercepts should bereported. There should always be uncertainty estimates with any reported data or data analyses.Page 2-82, line 6: There are a number of references to papers in the PM2000 issue of AerosolSci. Technol. This issue was published in January 2001 and thus, all of these references likeChow et al. need to be updated.Page 2-88, line 20: Same date problem. Also need to point out why we want better time resolveddata. We have been adjusting the time interval of the O 3 standard because we have the data toaggregated the data at various time intervals. We do not have that advantage with PM unless“continuous” monitors are more widely used.Page 2-94, lines 1-10: Fergenson et al. (In press, 2001) have shown that quantitative estimatescan be made of the aerosol composition from the single particle MS data.Page 2-96, lines 1-12: Need to add the Continuous Sulfate Monitors that are now available.There is no discussion of measurement methods for Coarse particles and how you would getsamples that could be used to characterize the particle compositions, do source apportionment,etc.Chapter 3.There needs to be a clearer focus on what is know about the concentrations, sources,distributions, compositions of coarse particles. There is too much emphasis on PM 10 and notenough on coarse. Chapters 4 and 6 single out the effects of coarse. This chapter needs tocoordinate with the background atmospheric behavior so that the context for the subsequentchapters has been created. There is only a short section on Page 3-11. If this is all theinformation that is available, then there has to be a clearer statement that information on PM 10-2.5is limited and that this is all there is that is known regarding its distribution nationwide.Page 3-19, Because of the very large variability in the relative amounts of fine and coarseparticles, it is misleading to provide only a mean PM 2.5 /PM 10 ratio. The only sensible way toprovide such information is with distributions.Page 3-26, lines 4 -10: Need to have the discussion of active homogeneous nucleation in Chapter2 and need a pointer back to that discussion here.Page 3-36, lines 10-21: A major part of secondary particles in the east and maybe elsewhere issecondary organic aerosol. Thus, there needs to be a discussion of the sources of the precursorgases that include both anthropogenic and biogenic sources.Page 3-37, lines 23-31: Should add a discussion of UNMIX. EPA has invested in getting thismodel ready for use and should be included in this discussion.Page 3-42, lines 11-28: This discussion is out of date. More recent data suggests a much moreimportant role for SOA in the eastern US ambient aerosol.Page 3-51, lines 8-11: Agriculture is a major source of ammonia. Take for example the Chinofeedlot. With dairy farming widespread in the NE and North Central US, it could be importantin the eastern US as well.A - 2
Page 5: known, the potential causes deserve
Page 10: SCIENCE ADVISORY BOARD STAFFMr. A.
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Page 17 and 18: mode vs. the other. In fact, such k
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6-243 12 This section (6.4.4.) shou
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Chapter 5. Human Exposure to PM and
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the chapter. Many of the poor quali
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Page 5-17, equation 5-10; the coeff
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illustrated using a figure from Kel
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tied back to the base-line health s
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Page 7-4, Structure of the Respirat
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Günter Oberdörster, PhDChapter 7
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efficiencies as well as the ratio o
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The title of this section is also s
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old and young rats and mice used on
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passive use values as opposed to us
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Specific Comments:Page 5-19, lines
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Chapter 9 - General CommentsThis ch
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George Taylor, PhDAir Quality Crite
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atmospheric stressors associated wi
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“At the surface, a variable fract
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that point from this review! “Vis
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6. P 2-86, section 2.2.5.1 - A shor
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Review of the Air Quality Criteria Document for Particulate Matter

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