ATTACHMENT B
LINE-BY-LINE COMMENTS
PREFACE
Page iii, line 11: The author must mean “location” of exposure. The “route” of exposure is known (inhalation).
Page iii, footnote 1: It should be “NARSTO is.”
EXECUTIVE SUMMARY
Page ES-2, lines 20–21: The wording needs editing. “Hypothesis” does not “interact” with the body to “provide causal explanations.”
Page ES-5, line 16: Insert “and” before NOx.
Page ES-5, line 19: The wording needs editing. The committee does not think you are really talking about “interactions between PM and issues.”
Page ES-8, lines 15–24: Should this paragraph also mention Mexico City?
Page ES-9, lines 1–2: Because many readers will read only the executive summary, you should spell out all abbreviations or otherwise explain what they mean.
Page ES-9, lines 8–9: “1 in 6 days or more frequently” would be more explicit than “1 in 6 days or better.”
Page ES-12, line 6: Although much more rare, regulations can also address nonanthropogenic PM emissions, such as pollutants.
Page ES-12, line 16: Why not use “EC” as the preferred term, and not “black carbon”?
Page ES-12, lines 22–23: Evaporative emissions (from vehicles, paints, solvents, and so on) are also substantial sources of organic carbon.
Page ES-12, lines 33–34: It is stated that transport of Asian PM to North America happens a few times per decade. How often is African PM transported to North America?
Page ES-15, bullet 1: These tools can be used to work on solutions, but they are more typically used for detecting problems.
Page ES-15, bullet 2, fifth point: Edit “Reduction in sulfate reduction.”
Page ES-18, bullet 1, last line: The last phrase of this sentence is vague.
Page ES-22, line 9: Edit “Other pollution issues other than.”
Pages ES-25 and ES-27: These figures are of limited use and are not cited in the text.
Page ES-28, line 32: “is required” should be “was required.”
Page ES-29, Table PQ7: It is not clear how “science assessments” and “state-of-knowledge assessments” differ.
Page ES-30, line 30: “Data is available” should be “Data are available.”
Page ES-32, line 7: “lease understood” should probably be “least understood.”
Page ES-32, line 20: “between pollutants” should be “among pollutants.”
Page ES-33, line 17: “data is” should be “data are.”
Page ES-34, line 15: Earlier, you describe “ultrafines” as 20 nm, but here you seem to be describing them as 1 nm.
Page ES-34, line 31: “data is” should be “data are.”
Page ES-35, line 22: Are you certain that you mean “prospective” here?
Page ES-35, line 25: It should read “studies including data.”
Page ES-36, lines 11–12: How about vapors? There is increasing evidence of the importance of organic vapors (semivolatile organic compounds), and they are not generally included in lists of “gases.”
Page ES-37, line 24: “characteristics in” should be “characteristics of.”
Page ES-38, line 22: Off-road mobile sources should be mentioned; they are not generally included with “transportation.”
Page ES-39, line 22: What does “open” sources mean?
Page ES-39, line 27: “insure” should be “ensure.”
Page ES-41, line 26: The committee believes that it should read “20% of the organic mass of particles” rather than “20% of organics in particulate matter.” Because we cannot speciate it, we do not know what portion of the organic species we can measure. We know that only we cannot speciate more of the organic mass.
Page ES-41, line 31: It should read “operate than filter.”
Page ES-43, line 4: It should read “and have been well defined.”
Page ES-45, line 33: What are the units for “500”? Miles? Kilometers?
Page ES-47, lines 9 and 34: “CTM” is defined differently in these two lines.
Page ES-47, line 21: It should be “If an emissions tracer….”
Page ES-47, line 27: It should be “…program have cost….”
Page ES-49, line 25: These measures are not “surrogates for PM health effects,” nor is it clear how they could be.
Page ES-51, lines 18 and 22: There is nothing wrong with the term “broaching” itself, but this is the first such usage the committee has seen. One usually speaks in terms of “exceeding” standards.
Page ES-52, line 30: Does one ordinarily think of models in terms of having “skills”?
Page ES-53, line 22: It should read “programs comparable with that of the United States.”
CHAPTER 1
Page 1–3, Box 1: Although emissions of semivolatile gases contribute to PM, it seems incongruous to include them as “primary PM” emissions. They are not PM when emitted.
Page 1–3, line 4: Elemental carbon is called “black carbon” elsewhere. The terminology should be consistent.
Page 1–3, lines 4–6: Although it is true that the bulk of coarse PM mass comprises crustal materials, it is worth noting that it also contains PM that is not of crustal origin, such as road-surface wear particles, tire and brake wear particles, and vegetation detritus. Indeed, much of urban “road dust” is not crustal in origin.
Page 1–4, Box 2, paragraph 1: What are “black organic liquids”? Is this term explained elsewhere? If it is commonly used, the committee has never seen it.
Page 1–4, Box 2, last paragraph: The issue of adjusting the organic carbon value on the basis of “molecular form” is not presented clearly here. It is an important issue if one wants to understand the present state of science in this field. A reader who does not already understand this issue could not understand it from this description.
Page 1–5, line 9: The statement here is true, but ultrafine PM also results from combustion that is not anthropogenic and from noncombustion sources. Ultrafine PM is not well understood by the health-research community and is even less understood by the lay public. It is worth clarifying the nature and sources of ultrafine PM in this assessment.
Page 1–7, Table 1.2: Should include forest fires and biomass burning in the general source types. They are discussed on lines 11–18 of page 1–7.
Page 1–8, line 10: Delete “daily.”
Page 1–8, line 10: The daily mortality and morbidity are important, but long-term effects on disease and survival are also important. Indeed, many now believe that the long-term effects of PM constitute a more serious public-health burden than the short-term effects.
Page 1–10, line 1: Change “equivocally” to “unequivocally.”
Page 1–11, Table 1.3, second box down in right column: Many particles are nonspherical, but many are spherical. Third box down in right column: It is true that most ultrafine PM is “transient in character”; i.e., they don’t last long in that mode. That’s important in considering the relationship between health effects and proximity to fresh combustion emissions. However, a more important issue for health is whether ultrafine PM exists where people breathe, not how old the PM is. Most people live and work in areas where there is
always considerable ultrafine PM. Last box down in right column: Why say “in most places”? Is there any common site where there are not variable mixtures of many pollutants? This wording denies the true predominance of the issue.
Page 1–15, line 7: Add “Mexico.”
Page 1–17, footnote 5: There is a more specific reference for this document (it has an EPA document number and date).
Page 1–20, Figure 1.7: This figure needs a bit of attention to make it clear (whether or not it is represented exactly as originally published). Not all PM types are not found in the scheme. That is alluded to in the text but not in the figure legend. The tier labeled “BC and OC” shows the OC hierarchy, but not BC. The OC hierarchy is unclear. For example, both primary and secondary OC leads to OC PM, and the “anthropogenic vs biogenic” issue starts at the top, not just at the bottom of the hierarchy. The concepts that this figure is intended to portray are important, but they are not presented well by the figure. The authors would do better to develop a new figure.
Page 1–20, Figure 1.8: The figure legend is misleading. The figure does not illustrate only processes relevant to PM “formation.” For example, deposition is not a “formation” issue.
CHAPTER 2
Page 2–1, lines 23–24: Language is awkward.
Page 2–1, lines 26–28: Sentence implies that ammonium nitrate homogeneously nucleates rather than forming heterogeneously on pre-existing particles; this has not been demonstrated.
Page 2–3, lines 6–7: “water leaves the particle and returns to the vapor phase.”
Page 2–7, line 9: Change “because of” to “against.”
Page 2–8, line 10: At the end of the line, add “However, it has been shown that black carbon and organic aerosol react with OH and other oxidants, making them hydrophilic; hence, the particles absorb water more efficiently as they age (see Bertram, A.K, A.V.Ivanov, M. Hunter, L.T.Molina, and M.J.Molina. The reaction probability of OH on organic surfaces of tropospheric interest. J. Phys. Chem., 105, 9415–9421, 2001).”
Page 2–12, line 12: “lead to the reduction of particulate nitrate and returns nitrogen oxides to the gas phase.”
Page 2–16, line 1: Give references to the studies referred to in this paragraph.
Page 2–16, lines 9–10: Phrasing is awkward phrasing. How about “From Precursor Emissions to Aerosol Component Concentration”?
Page 2–16, lines 26–28: Language is awkward.
Page 2–18, lines 24–25: Refer to table data (in blue). Are the tables going to be in color?
Page 2–19, lines 17–19: There is a minor logical problem. Sulfate reduction does not directly result in “freed” ammonium; without the sulfate, ammonia would not have been in the ammonium form. It does leave more unscavenged gas-phase ammonia to react with nitric acid, as the next sentence states.
Page 2–21, Figure 2.10: This figure is confusing; perhaps it could be improved, although the topic is complicated.
Page 2–24, line 30: There is a minor logical problem in “their activation and the resulting droplet’s subsequent lifetime.”
Page 2–26, line 9: Change “from Asia and” to “Asia to North America and.” Cross check and refer to Appendix D.
Page 2–27, line 3: “to HNO3 which reacts with available ammonia.”
Pages 2–26 and 2–29: Add subheadings to separate the PM-ozone discussion from the PM-haze discussion, if it is desirable to retain the PM to haze discussion.
Page 2–30, line 15: Update the reference “(IPCC, 1995)” to “(IPCC, 2002)” and the corresponding material as needed.
CHAPTER 3
Page 3–1, line 5: There is an extra comma after “PM.”
Page 3–2, line 4: Table 3.1, title “10_m” should be “10 µm.”
Page 3–4, line 6: “green house” should be “greenhouse.”
Page 3–4, line 9: Define “CTMs” because it is used here for the first time.
Page 3–6, line 8: The reference cited under footnote 1 of Table 3.2 should not have “e.g.,” if the reference refers to only one special study.
Page 3–7, line 17: “Molinas et al. (2001)” should be “Molina et al. (2000).” (Perhaps the latest reference, Molina and Molina [2002], should be used.)
Page 3–7, line 24: Delete the gap between “PM” and subscript “10” and between “PM” and subscript “2.5.”
Page 3–8, line 2: Change “are not necessarily relevant to the vapors that are believed to produce secondary organic carbon” to “are unlikely precursors of secondary organic carbon particulate matter.”
Page 3–9, Table 3.3: Check the numbers listed under “Open Sources” and “Fugitive Dust”; footnote 2 indicates that fugitive dust is part of open sources, but the values for fugitive dust under “Primary PM10” and “Primary PM2.5” for the United States and Canada are larger than the values for open sources. The last column, fugitive dust is listed as contributing “4322” to NH3 for the United States? Footnote 1 indicates that bold numbers are emphasized for large contributions; but in the last column, “88” us boldface but not “270.”
Page 3–10, line 11: What is “VOCpart”?
Page 3–11, Table 3.4: The unit for Max PM10 should be µg/m3. Specify the year when the data were reported, such as the population of Mexico City and the peak O3 of 300 ppb. Data on Mexico are suspicious. For example, the GDP is listed as US$ “2400” (what year?) but the value is US$ 7750 in 2000. The committee suggests referring to Table 2.1 (page 22) of Molina and Molina (2002), which also includes other statistics. Footnote 4: What does “nominal value” mean? The total area of the Mexico City metropolitan area is 5300 km2, and of the urbanized area 1500 km2. The committee suggests referring to Table 3.5 (page 74) of Molina and Molina (2002).
Page 3–13, Table 3.5, last column: PM10 includes PM2.5, so the value for Los Angeles “on road” PM2.5 emissions of 9200 is inconsistent with the value of 7800 for PM10. Footnote 3: Check spelling for CAM; it should be “Comisión Ambiental Metropolitana”?
Page 3–14, Table 3.6: The value of the on-road contribution to NOx for Mexico City should be “165,800,” not “65,800.” Footnote 3: Check spelling for CAM; should it be “Comisión Ambiental Metropolitana”?
Page 3–15, line 2: Assuming that the values listed in Table 3.5 were correct, the primary PM10 emission for Mexico City is about one-seventh to one-sixth of Toronto’s or Los Angeles’s emission, so, the phrase “perhaps amounting to only one-third to one-fourth of Toronto’s PM10 emissions, and even less than Los Angeles” is incorrect.
Page 3–15, line 5: The phrase “along with transportation sources” is inconsistent with the values listed in Table 3.5 and on line 4 of page 16; that is, the contributions from “open sources” are much larger than from “transportation sources.”
Page 3–15, lines 11 and 12: According to Table 3.5, the ratio of PM2.5 to PM10 for Atlanta should be 24%, not 34%. Therefore it is not “about the same as in Los Angeles (36%).” However, note that there is a question about the PM2.5 value for on-road PM2.5 emissions for Los Angeles as commented on above.
Page 3–16, line 2: The assumption that “all of the PM observed in the cities is local in origin” is debatable and inconsistent with line 13.
Page 3–16, line 4: “0.1” should be “0.16” or “0.2” if rounded off to one significant figure. However, see line 5, which uses two significant figures: “0.34 to 0.55.”
Page 3–16, line 5: “0.5” should be “0.8.”
Page 3–16, line 12: Rephrase the first sentence from “Another dimension reflected in the emission inventories is the geographical distribution of pollutants.” to “The geographical distribution of pollutants results from the emissions and dispersions of pollutants.”
Page 3–25, line 3: “ands” should be “and.”
Page 3–25, line 29: “2001” should be “2000.” The committee suggests referring to discussions in Section 4.1 starting on page 164, citing particularly page 167, of Molina and Molina (2002).
Page 3–26, line 14, “(” should go to the next line.
Page 3–29, line 20: Clarify “resolution of definitions.” Does it mean resolution of differences, resolution of uncertainties, or resolution of definitions? If the latter, which definitions?
Page 3–31, lines 6–9: It should be noted that Mexico is using modified MOBILE 5 or MOBILE5a.3MCMA for VOC, NOx, and CO but still uses the U.S. method for PM10. The committee suggests referring to Section 6.3 on page 201 of Molina and Molina (2002) and page 24 of CAM (2001).
Page 3–33, line 22: The source profiles developed in the middle 1970s in Los Angeles should be reviewed; there is a chance that they have seriously shifted in as much as major changes in emission control of vehicles have taken place since that time.
Page 3–38, line 8: The committee suggests checking with the Mexican authorities about Mexican laws concerning disclosure of industrial pollution reported to the government.
Page 3–39, line 18: There are extra spaces before the commas.
Page 3–39, lines 27–28: Concerning the application of the MOBILE model into a GIS positioning system, the committee suggests checking the NRC report (National Research Council. 2000. Modeling Mobile Sources, National Academy Press, page 48) on the limitations of the MOBILE model.
Page 3–40, line 19: Fine particulate matter does not entirely follow population centers except in the broadest sense. For clarity, add the word “sources” after “PM2.5.”
Page 3–41, line 20: What is meant by “traditional”? Man-made or natural? The committee suggests deleting the phrase “along with more traditional sources.”
CHAPTER 4
Page 4–7: The descriptions of the different types of size-selective inlets would benefit from simple diagrams. The descriptions are fine for those who are already familiar with the inlets; for those who are less familiar, the text descriptions do not adequately describe how the inlets work.
Page 4–7, line 34: If these are used in both urban and nonurban areas, what areas are left?
Page 4–9, line 28: Fix “may the altered.”
Page 4–10: Recommendation 2.5 should be recommendation 1.3. Recommendation 1.3 (page 4– 25) should be 1.6.
Page 4–12, line 13: The pressure-drop continuous mass-measurement device is mentioned but not described; some description should be added.
Page 4–28, lines 14–15: What are the problems with current approaches to calibration for O3, NO and NO2? These are not indicated in Table 4.4, nor are they described in the text.
Pages 4–15 and 4–31: Personal monitors can achieve much better accuracy than a factor of 2 for major ionic species relative to ambient measurements (such as of sulfate); in fact, agreement is usually better than for PM mass. There are commonly used photometers that have been used for real-time personal monitoring and these should be mentioned. Also, much of the early personal-monitoring work was done with portable piezobalances.
Page 4–16, lines 14–16: The statement that single-particle measurement methods are “available only as research tools” is outdated and needs to be deleted or changed. Two of the instruments listed in Table B.4 are now commercially available: the ATOFMS from TSI and the AMS from Aerodyne Research, Inc.
Page 4–27, Table 4.3: Should acknowledge the 20% of the organic (speciated) that is known.
CHAPTER 5
Page 5–2, line 13: Fix “Topography, through its influence circulation, strongly affects.”
Page 5–2, line 20: “Prevailing air mass patterns (see Fig. 5.1) make it possible.”
Page 5–4, Table 5.1; “Comment” 2: “Scale of concern for climate change.” Also, spell out or define “PSD”; it is not in the glossary.
Page 5–5, line 19, and page 5–6, line 22: Effects on “Central America and the southeastern United States or U.S. Gulf Coast” are cited twice. This is a trinational report, so we should probably acknowledge that Mexico lies between those two regions and is also affected.
Page 5–7, Section 5.3: This section identifies eight “different” North American regions. Chapter 10, which is the other major chapter with strong policy relevance, identifies nine, separating Los Angeles and the San Joaquin Valley.
Page 5–8, lines 5–6: The “Valle de Mexico” basin is NOT 1300 km2. The “Basin of Mexico” includes most of the Federal District, part of the state of Mexico, and southeast parts of the state of Tlaxcala and southern parts of the state of Hidalgo (Tizayuca and other municipalities). It also includes the main topographic features (volcanoes, mountains, and so on). All this area is about 9560 km2. However, the “Valle de Mexico” (Valley of Mexico or Mexico City metropolitan area) is the nearly flat floor of this basin that occupies a total area of about 5300 km2, of which about 1500 km2 is urbanized.
Page 5–11, Fig 5.4: Data on El Paso/Juarez and labeled as just “El Paso/”.
Page 5–12, lines 12–13: It is not clear that the cited Figure 5.3 supports the point made, because paired urban-nonurban monitoring sites are not identified in the figure.
Page 5–13, Figure 5.5: This has poor contrast and is hard to read.
Page 5–14, Figure 5.6: There are far too many significant figures on the axes.
Page 5–16, Figure 5.7: Data on Mexico City are not included (although they are available and presented in Figure 5.12).
Page 5–20, Figure 5.9: Labels are scrambled.
Page 5–21, Figure 5.10: This is too small.
Page 5–21, line 5: The phrase “but neither are these rare events” is repeated. The committee recommends that these statements be quantified rather than saying only that they are “not rare.” For example, do the events occur 10% of the time or less?
Page 5–23, Figure 5.11: The legend is very unclear, as is the meaning of the graphs. The red circle symbol seems to be entirely missing from the graph. The figure is good, but there are faded overprints, and locating arrows are needed for the bottom three plots.
Page 5–26, Figure 5.12: The outline of Mexico is omitted from the map
Page 5–27, Figure 5.13: Change SO4 to either sulfate or SO42-; be consistent with rest of report.
Page 5–32, Fig 5.15: This is generally illegible. Not enough is legible for reading this graph or even to know what pollutants were measured.
Page 5–34, Figure 5.16: This is too small, and site labels are missing.
Page 5–35, Figure 5.17: This is too small, and site labels are missing.
Page 5–40, Figure 5.18: This is too small.
Page 5–43, line 18 and elsewhere: Hidy 19XX is referenced. Add year of publication.
Page 5–44, Figure 5.20: The scale of the graphs makes it most difficult to evaluate any trends or changes.
Page 5–46, lines 1–5: Needs a reference for the stated trends.
Page 5–46, line 7: How is “improvement in PM exposure” defined and is it true that it has improved? Even though concentrations have gone down, there are larger populations in urban areas, so it might be possible that exposure (total rather than per-person) has gone up. It is also important to mention that in Mexico PM exposure is now worse than it was 50 years ago.
Page 5–47: There is inconsistency between the statement that PM in California “is dominated by ammonium nitrate and carbon compounds” and the earlier statement that the Grand Canyon gets a substantial fraction of its sulfate from California. They cannot both be true unless there is vast SO2 conversion between California and the Grand Canyon.
Pages 5–50 and 5–51, Figures 5.22 and 5.23: Axis labels are skewed.
Page 5–56, line 9: Word choice “principal specific objectives.”
Page 5–56, lines 14–15: “variety of PM carbon.”
CHAPTER 6
Page 6–2, line 1: “at long term to evaluate.”
Page 6–3, line 2: Replace “of insights that are possible are listed” with “of possible insights are listed.”
Page 6–3: In the examples on page 6–3, it would be convenient to comment on how the studies helped to answer policy questions.
Page 6–4: Improve quality of figure. Change legend from “MER Neighborhood-Scle” to “MER Neighborhood-Scale.”
Page 6–6, legend: Omit “just from, and were not.”
Page 6–8, lines 5–22: What can be said about reliability of meteorology data and their influence on the results?
Page 6–9: The description of Figure 6.4 does not refer to part 3.
Page 6–9, Section 6–2: It would be interesting to have an evaluation of the use of the different methods to support decision-making.
Page 6–10, lines 1 and 2: These lines are repeated.
Page 6–10, line 1: “however” is redundant; the cost is the same.
Page 6–10, lines 1–2: “Costs for receptor-oriented studies range from ~$US 50K for a small community with an established air quality network to ~$US 10M for a large region with a”: do you mean source rather than receptor?
Page 6–10, lines 11–12: “are seldom available in retrospect and thus” is awkward and should be reworded.
Page 6–11, table legend: Omit “JEFF state that all methods.”
Page 6–14, lines 1–2: Omit “It is the responsibility of the modeler, not the CMB model, to evaluate” and change the remaining part to “The CMB uncertainties and performance measures and such other data as emission inventories should be evaluated.”
Page 6–18, paragraph 2, line 4: “depending upon size.”
Page 6–19, line 14: Change “than the 10 µm” to “than the original 10 µm emitted size.”
Page 6–20, paragraph 3, line 1: In addition to soil and dust….
Page 6–20, paragraph 4, line 1: Figure 6.5b shows a profile of a coal-fired power station. The profile contains many of the same….
Page 6–22, legend: Change “wood burning from typical of Denver” to “wood burning typical of Denver.”
Page 6–32, line 3: “before, during and after the peak gives.”
Page 6–34, lines 15–16: Change “improved catalyst performance and these were linked, using an aerosol evolution approach, to secondary nitrate and organic aerosol in the ambient PM2.5.” to “improved catalyst performance. These emissions were linked by using an aerosol evolution approach to secondary nitrate and organic aerosol in the ambient PM2.5.”
Page 6–34, line 19: Omit “thus,”.
Page 6–34, line 25: Omit “Even still,”.
Page 6–36, legend: Omit“, given the range of sources assumed to be important,”.
Page 6–37, in table: Change “effected” to “affected.”
Page 6–37, Box: “Responds to decreases” is awkward and unclear; it should be reworded.
Page 6–38, line 3: “bold green box” is missing.
Page 6–40, line 1: Change “markers was found” to “markers were found.”
Page 6–42, Figure 6.10: Specify the type of “particle concentration”; is it PM2.5, PM10, or something else? It is unclear what is meant by “Fractional change of particle plus gas ammonia concentrations.” Is this essentially total ammonia species, that is, particulate ammonium (and ammonia hydrate)+vapor-phase ammonia? If so, please clarify.
This chapter uses “SO4,” “SO4,” and “sulfate” to describe the particulate form of S(VI). The chapter (and the entire report) should be consistent in the use of terminology even though the field as a whole is not. In addition, if the chemical formula approach is used, consistently use the proper form indicating the anionic state, “SO42-” rather than “SO4” and “SO4”.
Page 6–45, Table 6.2: Define “ROME.”
Page 6–45, Table 6.2, second column, 8th box: Unhyphenate “dis-persion.”
Page 6–45, Table 6.2, third column, 2nd box: A space is needed before “at receptors.”
Page 6–46, Figure 6.11: The legend is blank, and symbols are not defined.
Page 6–47, Section 6.5: Is there an example of Mexico?
Page 6–48: Change paragraph 1 of Section 6.5.2 to read “Observational methods and receptor models are necessary but not sufficient for identifying contributing source types and quantifying their contributions to PM. These methods are heavily dependent on the measurements available, and quantitative apportionment is seldom accurate when applied to measurements that have not been taken for this specific purpose. Receptor methods have strengths and weaknesses. Multiple methods help to characterize uncertainties and concurrence of results. Conclusions….”
Page 6–49: Paragraph 3 seems to be a different section, like a suggested method for source apportionment or attribution. In the same paragraph, line 2, “follow” is repeated; change “following” to “next.”
Page 6–49, lines 3–4, last sentence: Change to “Agreement between the receptor and source models increases confidence and represents the optimum ‘weight of evidence’ outcome.”
Page 6–49, lines 9–10: Change “provides clearer focus” to “provides a focus.”
Page 6–49, lines 20–21: Change “identify which factors…are most important and/or most uncertain” to “identify the factors…that are most important or most uncertain.”
Page 6–49, line 24: Change “Receptor models need to know which” to “Receptor models require information on.”
Page 6–49, lines 34–35: Sentence is awkward. Change to “…but these profiles do not necessarily represent those which affect an area where they were not measured.”
Page 6–50, point 8: Change “since no model, source or receptor, is” to “Because no source or receptor model is.”
Page 6–50, point 8: Awkward word choice. Change to “results must be independently challenged.”
Page 6–50, Section 6.6: Sentence starting “Receptor models are useful” is not properly structured and lacks parallelism.
Page 6–50, Section 6.6, line 5: Change “are not usually sufficient, by themselves, to characterize” to “are not usually sufficient to characterize.”
Page 6–50, Section 6.6, lines 7–8: Change “The approach to deal with the uncertainties and to obtain the best understanding” to “Reducing uncertainties and improving our understanding.”
Page 6–50, Section 6.6, line 11: Omit “, which tend to be empirical,”.
Page 6–50, line 13: Change “of the measurements, ambient and source,” to “of ambient and source measurements.”
Page 6–50, line 13: Change “as well as” to “and.”
Page 6–51, paragraph 3, line 9: “Conclusions drawn from this ‘weight of evidence’ approach will be more defensible for decision-making, even when there are disagreements, and agreement between approaches clearly increases confidence” is awkward.
Page 6–52, Section 6.6.1.1, line 1: Omit “This can be done reasonably well.”
Page 6–52, Section 6.6.1.1, line 3: Omit “, rather than absolute,”.
Page 6–52, Section 6.6.1.3, line 2: Replace “inorganic secondary material” with “inorganic primary material”; the inorganic secondary components have been named earlier (sulfate, nitrate, and ammonium).
Page 6–53, Section 6.6.1.4, line 4: Replace “expected to more or less” with “expected to be more or less.”
Page 6–53, Section 6.6.1.4, line 6: Omit “obviously,”.
Page 6–53, Section 6.6.1.4, line 8: Omit “upon.”
CHAPTER 7
Page 7–4, Figure 7.1: This figure is not explained in the text or in the legends. Labels are missing from the arrows.
Page 7–5, line 6: “Since” should be “Because.” The same change should be made on page 7–8, line 23; page 7–11, line 14; page 7–15, lines 9 and 15; page 7–19, line 21; page 7–20, line 21; page 7–21, line 27; page 7–22, line 21; page 7–27, line 14; page 7–42, lines 21 and 24.
Page 7–5, line 24: Rather than “kilometers traveled,” such activity ought to refer to the “kilometer-tons” traveled, that is, the amount of work done. Pollution per vehicle would be put in much better management perspective if pollution were dealt with in terms of the unit
of work vehicles do. With regard to societal benefit, a large truck probably emits less pollution per ton of load moved than an SUV.
Page 7–8: Some mention should be made of on-line models, i.e., those models in which the chemistry, emissions, deposition, and other air quality algorithms are embedded in the meteorology code and thus can make full use of the meteorology at the highest spatial and temporal resolution. Although such models are not yet widely used, they look to be the future of CTM development and therefore warrant at least a brief discussion.
Page 7–8, line 29: Put a comma after “scales.”
Page 7–10, lines 3–5: To many, if not most, readers of this document, the information here would be incomprehensible (for example, “order-1–5 TKE scheme…“).
Page 7–10, line 4: Explain briefly what is the TKE scheme and the order-1 K Theory.
Page 7–10, line 8: The concept might be clearer for most readers if “grid size” were used instead of “grid discretization.” This pertains to later use as well.
Page 7–12, lines 23–24: Not only is this not realistic for fresh emissions, but it is not realistic for any environmental collection of PM. There is always PM that is not “internally mixed.”
Page 7–13, line 20: Add “structures” to “soil and vegetation.” A lot of PM is also deposited on human-made structures of nearly all types.
Page 7–13, lines 23–25: The statement is true, but it is also true that under given circumstances, a model could overestimate or underestimate emissions.
Page 7–14, line 16: The footnote isn’t helpful here. If specific examples are to be given in a footnote, they need to be more understandable to the average reader than the present one.
Page 7–15, line 13: Episodic simulations are not only important for ozone because of the time criteria for the standards; they are also important because many air-quality management districts would like to be able to give advance public-health warnings.
Page 7–15, line 18: What is a “chemical lateral boundary”?
Page 7–19, Section 7.4: Explain how the questions were formulated. This may be explained if at the beginning of the chapter questions 1–4 are answered.
Pages 7–20 and 7–21, Sections 7.4.2 and 7.4.3: The answer is “yes,” but then it is explained how the answer may be “not”. This should be consistent. If “yes,” state what is available and what is needed.
Page 7–23, line 9: The metrics that are mentioned here are not, nor could they be considered, “metrics for PM adverse health effects.” The committee understands the “surrogate metrics” concept being portrayed, but understanding of the relationship between health effects and PM measures is so uncertain (albeit there is confidence that there is one) that one could not use these as surrogate metrics for health effects.
Page 7–24, line 26: To provide a correct definition, it should be “diameter of a spherical particle.”
Page 7–30, Table 7.1: In the next to last line of the title, “between” should be “among.”
Page 7–32, line 16: PM dose also depends on the inspiratory rate (presumably, “mode of breathing” means oral vs nasal) and anatomic differences among the airways of individuals, in addition to particle size and hygroscopicity.
Page 7–32, lines 31–32: The concentrations in motor vehicles will also depend on the number, type, and emission rates of the other vehicles on the road that contribute to the air parcel encountered by the vehicle of concern and to wind direction and speed.
Page 7–44, lines 9–10: The “4-D” concept should be explained; not all readers will understand what is meant.
Page 7–44, line 26: “performance is best for sulfate, and typically more uncertain for nitrate and ammonium.”
Page 7–47, line 21: “Results” should be “Result.”
Page 7–48, line 22: It would be useful to mention the record for accuracy here. If the models have been used to forecast ozone levels, what is their record of accuracy?
CHAPTER 8
Page 8–1, paragraph 3, line 5: “Role” should be “Roles.”
Page 8–2, Table 8.1: The list of chronic effects in the footnote conflicts with the term “acute” in the title.
Page 8–3, line 1: Do hospital discharges include deaths in the hospital?
Page 8–3, paragraph 1: What about lung cancer? There is a statistically significant link between PM and lung cancer in long-term studies, and this issue has recently drawn more attention.
Page 8–3, Table 8.2: What about the Northeast region? It seems odd that this (most populous) region is left out.
Page 8–3, Table 8–2: What is the relevance of presenting regional incidence data only for the United States? Is there supposed to be some inference that these differences are due to PM? In this context, the table might be misleading.
Page 8–4, paragraph 3: What about outdoor exposures to PM originating indoors? Is that “ambient” or “non-ambient”? Although one would not expect indoor-origin PM to be a major source, it is undeniably one of the sources (and one that is virtually never mentioned).
Page 8–4, Section 8.3, line 1: This sentence should be clarified; it is not restricted to personal exposure “in each microenvironment” but to personal exposure itself. “Non-ambient” and “ambient” PM should be described (as in the criteria document and primary literature) as PM of ambient and nonambient ORIGIN. The studies that have evaluated the relative contribution of ambient and non-ambient sources should be summarized (about 50% of total exposure is to PM of ambient origin). Furthermore, the importance (or lack thereof) of the distinction between PM of ambient and nonambient origin with respect to epidemiology should be described; for example, that there are substantial exposures to PM of ambient origin does not mean that ambient-PM epidemiology is invalid.
Page 8–4, last paragraph: Do these statistics refer only to the United States?
Page 8–5, paragraph 1, line 2: “Since” should be “Because.”
Page 8–5, paragraph 1, line 5: “This data” should be “These data.”
Page 8–5, paragraph 3, line 1: “Between” should be “Among.”
Page 8–6, paragraph 3, line 1: What does “relatively” mean here? Relative to what?
Page 8–7, Figure 8.1: If the figures from the Environmental Protection Agency PM CD are taken from some other original source, the original source should be cited, not the CD.
Page 8–8, paragraph 1, last line: See Sarnat at al. (2001), which evaluated the relationship (and its implications for epidemiology) between exposures to multiple gaseous pollutants and PM components: Sarnat, J.A., Schwartz, J.Catalano, P.J., Suh, H.H. 2001. Gaseous pollutants in particulate matter epidemiology: confounders or surrogates? Environ. Health Perspect. 109:1053–1061.
Dosimetry section: Physiologic factors (oral or nasal breathing, disease status, airway size, and so on) are of equal importance as aerodynamic properties of particles in determining deposition.
Page 8–8, paragraph 2, lines 1–2: According to the definition presented here, “dose delivered to” includes consideration of clearance, as well as deposition. Both deposition and clearance act to determine the concentration in the tissue at any given time.
Page 8–8, paragraph 3, line 1: “Airborne inhaled” is redundant, (unless one is drowning).
Page 8–8, paragraph 4, lines 3–5: The statement about growth of hygroscopic PM is correct most of the time but not all the time. If the inhaled air is already saturated at body temperature, hygroscopic PM presumably would not grow after inhalation.
Page 8–8, paragraph 5, line 1: When referring to “large” or “small” particles, give an example as a reference. Otherwise the reader doesn’t know what is meant. Even among knowledgeable researchers, these terms have no standardized meaning.
Page 8–8, paragraph 5, line 2: Is “respired” being distinguished from “inhaled”? If so, what is the point?
Page 8–8, last paragraph: A distinction should be made between “respirable” and “inhalable,” the two seem to be used interchangeably here, but by convention the do not refer to the same thing (occupational exposure limits). The descriptions of the different types of epidemiologic study should focus on the relevant designs in air-pollution epidemiology (or for multifactorial diseases in general). For example, one might not characterize the case-control study as being of highest inferential quality for air-pollution epidemiology.
Page 8–9, Figure 8.2: Cite the original source of the figure.
Page 8–9, paragraph 1: Overall, the discussion of particle size vs deposition is sloppy and needs reworking. The largest particle that can be inhaled is certainly not 10 µm. A 20-µm particle can reach the alveoli—with a low probability. The largest particles that could be inhaled would be of concern for nasal sites. Nasal passages are technically “airways,” but they would not ordinarily be called that without the modifier “nasal,” and most of this document’s audience would not understand that the nose was meant. It would also be useful to mention nose vs mouth breathing. The statement that alveolar deposition is of primary concern for small particles is a half-truth; the highest deposition of the smallest particles is in the nose.
Page 8–10, Figure 8.3: A figure showing deposition curves down to PM below 0.1 µm would be more informative. Overall, this is not a good choice of figures from among the many that have been published.
Page 8–10, paragraph 1: Although aerodynamic size ceases to be important after deposition has occurred, physical size remains important. Physical size of poorly soluble PM can affect its disposition. For example, some researchers are now confident that PM in the 50-nm or
smaller range (perhaps even up to 100 nm) either will not be picked up by macrophages or will be scavenged at very low efficiency.
Page 8–10, paragraph 1, line 3: It is not the “total mass” of PM in the air that is important, but the mass concentration, which is different. The committee has not seen an estimate of the total mass of PM in the air, although it would be interesting for conversational purposes.
Page 8–11, paragraph 1: A seventh mechanism is direct penetration of PM into and through cells, which is known to occur.
Page 8–11, paragraph 2, line 1: PM-derived material, whether soluble or nonsoluble, can also be transferred via lymph and may or may not reach the blood via that pathway.
Page 8–11, paragraph 3, line 8: Figure 8.3 doesn’t indicate the “smallest airways,” as suggested by the text; it aggregates all conducting airways.
Page 8–11, paragraph 3, line 12: “Since” should be “Because.”
Page 8–11, paragraph 4, line 1: It should read “particles inhaled,” not “inhaled particles.”
Page 8–12, paragraph 2, line 9: “Subpopulations” might be a better term for these subdivisions of the general population.
Page 8–13, paragraph 3, line 1: Time-series studies are informative for short-term effects, but other types of studies are more informative for longer-term effects.
Page 8–13, paragraph 4, lines 10–12: It is exposure scientists that (among other things) evaluate the relationship between community estimates and personal exposures. Is this really something in which atmospheric and health scientists need to interact?
Page 8–14: The distinction is not particularly important, but copollutants and meteorologic conditions can be considered both potential confounders and effect modifiers.
What is the relevance of Figures 8.4 and 8.5? Their inclusion may raise more questions than answers.
Page 8–14, paragraph 4: Here, or somewhere in the section on epidemiological evidence, the recently-revealed difficulty with the GAM software should be mentioned. An in-depth discussion is not in order, but rather something that brings the review up to date by making the reader aware of the problem. It would be appropriate to cite the Dominici et al. paper in the American Journal of Epidemiology (156(3):1–11, 2002).
Page 8–15, paragraph 3: The information given here is not sufficient for readers to understand Figure 8.6, unless they are already familiar with this type of data. If the figure is worth showing (and it probably is), give it a bit more explanation.
Page 8–19, paragraph 1, line 10: It can be argued that the “challenge” also includes improved understanding of the relationship between source and ambient concentration.
Page 8–20: There have been some initial, provocative attempts to address the issue of the heterogeneity of effect estimates with PM epidemiologicstudies (Janssen et al. APHEA-II), and these should be discussed:
Janssen, N.A., J.Schwartz, A.Zanobetti, H.H.Suh. 2002 Air conditioning and source-specific particles as modifiers of the effect of PM(10) on hospital admissions for heart and lung disease. Environ. Health Perspect. 110:43–49.
Atkinson, R.W., H.R.Anderson, J.Sunyer, J.Ayres, M.Baccini, J.M.Vonk, A.Boumghar, F. Forastiere, B.Forsberg, G.Touloumi, J.Shwartz, and K.Katsouyanni. 2001. Acute effects of particulate air pollution on respiratory admissions: results from APHEA 2 project. Air Pollution and Health: a European Approach. Am. J. Respir. Crit. CareMed. 15:1860–1866.
Page 8–21, Figure 8.7: The quality of the figure needs to be improved. An explanation of the term “lag” and its implications should be given in the text. Many readers might not be familiar with it, and the concept is very important.
Page 8–22, paragraph 2, lines 1–3: There should be a better explanation of the concept of mortality x monitoring days here. The concept is cited several times later and is important. Make certain that all readers understand it well the first time it is introduced.
Page 8–23, line 1, and elsewhere: Statistical power will affect the size of the confidence intervals but should not a priori affect the magnitude or sign of the effect estimates.
Page 8–27, paragraph 1, line 1: Is there any ambient environment in which people are not exposed to complex mixtures of pollutants? The wording denies reality by suggesting that mixtures might not always be present.
Page 8–27, paragraph 1, line 7: Like other studies that necessarily relied on measurements of NAAQS pollutants, the NMMAP study only looked at a few non-PM pollutants. The statement that it looked at “other” pollutants may be true, but it suggests something much more comprehensive than was actually done. No epidemiologic study to date has included more than a tiny fraction of the pollutants present. This is an important point to make in this chapter.
Page 8–28, last paragraph: If the extended analysis of the AHSMOG cohort, the Peters et al. (1999) study of southern California school children, and the Raizenne et al. (1996) study of 24 Cities in the U.S. and Canada are mentioned, some brief description of their results should be provided.
Page 8–28, paragraph 3, line 1: It is not clear what is meant by “semi-individual.”
Page 8–29, paragraph 1, last sentence: State more clearly what “coordinated efforts” are being talked about here. It is of little use to call for more interactions between atmospheric and health scientists if it is not explained what those interactions should be, no example of the envisioned interaction is given, and what could be achieved by such interactions is not stated.
Page 8–29, paragraph 2, last sentence: It should also be mentioned that children have greater ventilation per unit of body size than adults.
Page 8–30, paragraph 3, lines 10–11: First, explain “spline curves”; most of the readers of this document won’t know what that term means. Second, perhaps it is meant that the slopes increased, rather than that the curves increased.
Page 8–30, paragraph 3, line 14: Explain “Akaike’s Information Criterion” and give a reference. It is not clear that this term or concept is important to the chapter. If something as arcane as this approach is necessary for the reader to understand, it bears explaining.
Page 8–32, paragraph 1, last sentence: The Southern California Children’s Health Study is important for looking at lung-growth effects. This effect and the fundamental findings to date should be discussed.
CHAPTER 9
Page 9–3, line 22–23: This is true, but smokestack plumes can cover broad areas. From low altitudes, one can see a brown cloud layer over a large portion of northwestern New Mexico on many mornings. The wording suggests that non-PM smokestack emissions are only a local problem.
Page 9–8, line 2: It should be “Figure 9.4,” not “Figure 2.4.”
Page 9–13, Figure 9.5: The source of the figure, or the information in the figure is not given in the figure legend.
Page 9–16, line 16: Define “ASOS.” Visibility information is also given by AWOS (automated weather observation system [or service, I don’t remember which]) at airports. Why not cite that as well.
Page 9–16, recommendation box, last sentence: The term “better” isn’t very descriptive. Say “shorter,” “longer,” “more frequently,” or whatever is meant.
Page 9–31, lines 19–21: The issue of the humidity effect on the relationship between PM concentration and visibility could be presented more clearly. If PM is measured under standard humidity conditions—that is, if filters are dried to some moisture specification before weighing—many of the particles are larger and their actual mass concentration is greater in the air than is measured. For that reason alone, a given PM concentration would affect visibility more under humid conditions. There may be other factors in the relationship. The present discussion doesn’t present the above issue, nor does it clarify the concept underlying the discussion. A couple of sentences would fix the problem.
CHAPTER 10
Most of the descriptions of PM over Mexico City were taken from white papers prepared by the MIT Integrated Program on Urban, Regional and Global Air Pollution. The two references cited should be corrected as suggested below (the order of the author list was wrong). It should also be pointed out that the white papers have been updated and are included as a chapter in the book edited by Molina and Molina (2002).
Molina, M.J., L.T.Molina, J.West, G.Sosa, and C.Sheinbaum Pardo, F.San Martini, M.A. Zavala and G.McRae (2002) “Air Pollution Science in the MCMA: Understanding Source-Receptor Relationships through Emissions Inventories, Measurements and Modeling,” Chapter 5 in “Air Quality in the Mexico Megacities: An Integrated Assessment,” L.T.Molina and M.J.Molina, eds., Kluwer Academic Publishers, Dordrecht.
Page 10–18, line 5: It is egregious to say “careful coordination.”
Page 10–29, line 11: “West et al. (2000a)” should be changed to “Molina et al. (2000).” See comment on page 10–35, line 31, below.
Page 10–31, line 16: “West et al. (2000b)” should be changed to “Sosa et al. (2000).” See comment on page 10–35, line 34, below
Page 10–35, line 31: The reference should be changed as follows (note the order of authors, and use the full name of the program, not “IPURGAP”):
Molina, M.J., L.T.Molina, J.West, F.San Martini, G.Sosa, and C.Sheinbaum (2000) “Estado Actual del Conocimiento Científico de la Contaminación del Aire en el Valle de México” (or “Current State of Air Pollution Science in the Valley of Mexico.” MIT-Integrated Program on Urban, Regional and Global Air Pollution Report No. 9, 84 pages.
Page 10–35, line 34: The reference should be changed as follows (note the order of authors, and use the full name of the program, not “IPURGAP”):
Sosa, G., J.West, F.San Martini, L.T.Molina and M.J.Molina (2000). Air Quality Modeling and Data Analysis for Ozone and Particulates in Mexico City. MIT- Integrated Program on Urban, Regional and Global Air Pollution Report No. 15, 76 pages.
CHAPTER 11
Page 11–1, line 12: Doesn’t the standardization (or “harmonization”) of CTMs fall under this broad theme?
Page 11–1, line 20: Does “detailed emission models” include better source emission characterization? They are different, but one can’t have a better model without better characterization of source emissions.
Page 11–2, Science need 1.2: Does “carbon content” here mean speciation, quantity, or both? Be more explicit.
Page 11–2, Science need 2.2: Isn’t it also important to assess trends in locations that have different characteristics? The present wording calls for collecting data over a longer time, which is good. Here or under a separate “need,” it should call for developing a database by using comparable techniques in places that have different pollution and meteorologiccharacteristics.
Page 11–2, Science need 2.6: What does “harmonize” mean here? Without explanation, the word is ambiguous and therefore not useful. The same question applies to page 11–7, line 24; page 11–10, lines 12, 18, and 20; and page 11–16, line 20.
Page 11–2: Somewhere under the general heading of recommendation 2, the list of research needs should include better information on the surface chemistry of poorly soluble PM. Unless the PM is soluble, cells do not “care” about bulk chemistry, but about surface chemistry.
Page 11–3, Science need 3.3: It is not clear what is being sought by recommending “centers” or even what “centers” means. This item refers to Chapter 7.10, but the issue is not explained there either. The text on page 11–14 explains the recommendation adequately, but the wording in the table should be more explicit.
Page 11–3, Science need 4.3: It is not clear what “protocols” means. Does “protocols” mean (or include) models?
Page 11–3, Science need 4.9: It is not clear what is meant by “emissions processing interface.”
Page 11–4, Science need 4.10: Why is this numbered “4.10” rather than “4.1”? What is meant by “self-consistent”?
Page 11–4, Science need 5.1: “Data is” should be “Data are.”
Page 11–4, Science need 5.3: “Between” should be “Among.”
Page 11–4, line 4: Change “understanding of properties” to “understanding of chemical and physical properties.”
Page 11–5, line 2: Organic aerosols should be reduced because of their potential health effects and not just because they contribute to some extent to PM mass.
Page 11–6, line 23: A recent laboratory study (Bertram, A.K, A.V.Ivanov, M.Hunter, L.T. Molina and M.J.Molina. The reaction probability of OH on organic surfaces of tropospheric interest. J. Phys. Chem., 105, 9415–9421, 2001) implies that particulate organic compounds become hygroscopic as they age (in any location).
Page 11–6, line 23: It seems unlikely that differences in the hygroscopicity of organic PM are due primarily to location, as the statement implies. It may vary among locations, but isn’t it a function of the PM composition rather than location itself?
Page 11–7, line 6: Delete “and.”
Page 11–7, line 11: Give examples of “artifacts.”
Page 11–7, line 32: It should read “data are.”
Page 11–8, line 3: It should read “are also needed.”
Page 11–10, line 31: It is mentioned that Canada has an AWOS system, but it is not mentioned that the United States has both ASOS and AWOS systems.
Page 11–12, line 9: “then” should be “than.”
Page 11–15, line 10: The committee does not agree that health effects typically depend on PM size. They are associated with PM size because composition is generally correlated with size. There are differences in deposition, and thus in location and dose, due to PM size, but there is so much overlap in size-related dosimetry in the different regions of the respiratory tract that PM composition is undoubtedly a bigger driver of health than PM size (within the respirable size range).
Page 11–21, lines 2, 4, and 6: “Data” is a plural word. It should be “Data are” and “They.”
Page 11–21, line 12: “1000 a,b” should be “2000 a,b.”
Page 11–22, lines 12–14: Certainly future assessments should extend to considerations beyond mass. This one does. Why is this rhetorical question even posed?
APPENDIX A
Page A6, line 6: Suggest reading CAM (2001) and Molina and Molina (2002) on the emission inventory of Mexico.
