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Bibliometrics
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Supplement to Bibliometric Analysis for Papers on Topics Related to Particulate Matter (PM)
November 15, 2006
This is a supplement to the Bibliometric Analysis for Papers on Topics Related to Particulate Matter (PM) that was prepared for the Board of Scientific Counselors (BOSC) review of the PM Research Program in March 2005. This supplement presents the data by year for PM papers published from 1998 to 2004. The data are presented by year in Table 1, which includes eight key bibliometric parameters. The analysis of each of these parameters precedes the table. The Bibliometric Analysis for Papers on Topics Related to Particulate Matter (PM) that was submitted for the BOSC review is appended to this supplement.
The analysis was completed using Thomson’s Essential Science Indicators (ESI) and Journal Citation Reports (JCR) as benchmarks. ESI provides access to a unique and comprehensive compilation of essential science performance statistics and science trends data derived from Thomson’s databases. The chief indicators of output, or productivity, are journal article publication counts. For influence and impact measures, ESI employs both total citation counts and cites per paper scores. The former reveals gross influence while the latter shows weighted influence, also called impact. JCR presents quantifiable statistical data that provide a systematic, objective way to evaluate the world’s leading journals and their impact and influence in the global research community.
- No. of PM Papers Analyzed–The number of PM publications has been increasing over the period analyzed (i.e., 1998 to 2004).
- Total No. of Highly Cited Publications–ESI identifies four thresholds of highly cited papers–those in the top 10%, top 1%, top 0.1%, and top 0.0.1%. It is extraordinary for a publication to meet the threshold for the top 0.01%; these publications are rare and should not be expected in each year of a program. Using the ESI thresholds, more than one-third of the PM publications are highly cited papers. From 1998 to 2004, approximately one-third of the PM papers qualified as highly cited when using the ESI criteria for the top 10% of highly cited publications. There is a definite recent increase in the number of PM papers that qualified as very highly cited when using the ESI criteria for the top 1%, 0.1%, and 0.01%. For example, in 2004, 0.2% of the PM papers met the highest criteria for the top 0.01% of highly cited papers. This is 20 times higher than would be expected for the average program for which only 0.01% of the publications would meet the highest criteria. Similarly, 3.5% of the PM papers published in 2004 met the criteria for the top 0.1%, which is 35 times higher than would be expected.
- Ratio of Actual to Expected Cites–The PM papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, the ratio of actual to expected cites is greater than 1 for every year analyzed. This indicates that the PM papers are more highly cited than the average papers published.
- No. of Papers in High Impact Journals by Impact Factor–More than one-quarter of the PM papers are published in high impact journals as determined by the JCR Impact Factor of the journals in which the papers were published. The Impact Factor is a well known metric in citation analysis. It is a measure of the frequency with which the average article in a journal has been cited in a particular year. The Impact Factor helps evaluate a journal’s relative importance, especially when compared to others in the same field. The Impact Factor is calculated by dividing the number of citations in the current year to articles published in the 2 previous years by the total number of articles published in the 2 previous years. More than one-quarter (25%) of the PM papers appeared in the top 10% of high impact journals, which is substantially higher than the expected 10% of papers that would appear in the top 10% of high impact journals.
- No. of Papers in High Impact Journals by Immediacy Index–Nearly one-third of the PM papers are published in high impact journals as determined by the JCR Immediacy Index of the journals in which the papers were published. The journal Immediacy Index is a measure of how quickly the average article in a journal is cited. It indicates how often articles published in a journal are cited within the year they are published. The Immediacy Index is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year. More than one-third (33%) of the PM papers appeared in the top 10% of high impact journals as determined by the immediacy index, which is substantially higher than the expected 10% of papers that would appear in the top 10% of high impact journals.
- Total No. of Publications Cited One or More Times–The percentage of publications cited one or more times is fairly consistent from 1998 to 2002. The number declines as expected in the more recent years (i.e., 2003 and 2004) because most publications are not cited until a year or longer after they are published.
- Total No. of Author Self Cites–The authors of the PM papers cite themselves less than the average self-citation rate. The author self-citation rates in Table 1 are well below the accepted range of 10-30% author self-citation rate.
- No. of Hot Papers–Using the hot paper thresholds established by ESI as a benchmark, the number of hot papers each year has been fairly consistent. The decline in the percentage of hot papers in 2004 is expected, and it is attributed to the fact that the period during which the cites analyzed for determining hot paper status was incomplete. ESI establishes citation thresholds for hot papers, which are selected from the highly cited papers in different fields, but the time frame for citing and cited papers is much shorter–papers must be cited within 2 years of publication and the citations must occur in a 2-month time period. Papers are assigned to 2-month periods and thresholds are set for each period and field to select 0.1% of papers. For papers published in 2004, the 2-year period of consideration would not conclude until 2006. This analysis was completed in March 2005; therefore, the number of hot papers among those published in 2004 would be expected to be lower than if the analysis was completed in January 2007.
Table 1. Key Bibliometric Parameters for PM Papers Published From 1998 to 2004
ANALYSIS PARAMETERS |
1998 |
1999 |
2000 |
2001 |
2002 |
2003 |
2004 |
1. No. of PM Papers Analyzed1 |
44 |
87 |
145 |
144 |
159 |
146 |
170 |
2. No. of Highly Cited Publications That Met the Top 10% Threshold |
21 (47.7%) |
41 (47.1%) |
60 (41.4%) |
49 (34.0%) |
60 (37.7%) |
43 (29.4%) |
47 (27.6%) |
No. of Highly Cited Publications That Met the Top 1% Threshold |
2 (4.6%) |
7 (8.0%) |
13 (9.0%) |
15 (10.4%) |
12 (7.6%) |
11 (7.5%) |
14 (8.2%) |
No. of Highly Cited Publications That Met the Top 0.1% Threshold |
0 |
0 |
1 |
2 (1.4%) |
2 |
2 (1.4%) |
6 (3.5%) |
No. of Highly Cited Publications That Met the Top 0.01% Threshold |
0 |
0 |
0 |
0 |
0 |
0 |
2 (0.2%) |
3. Expected No. of Citations Calculated Using the Average Citation Rate |
573.64 |
869.89 |
1101.23 |
734.57 |
596.02 |
281.76 |
43.69 |
Total No. of Times Cited for All Publications |
1,111 |
2,118 |
2,412 |
1,675 |
1,535 |
587 |
136 |
Ratio of Actual Cites to Expected Cites |
1.94 |
2.43 |
2.19 |
2.28 |
2.58 |
2.08 |
3.11 |
4. No. of Papers in High Impact Journals by Impact Factor |
16 (36.4%) |
26 (26.8%) |
39 (26.9%) |
47 (32.6%) |
44 (27.7%) |
39 (26.7%) |
41 (24.1%) |
| 5. No. of Papers in High Impact Journals by Immediacy Index (Percentage) |
21 (47.7%) |
28 |
35 |
40 |
52 |
50 |
40 |
6. No. of Publications Cited One or More Times |
42 (95.4%) |
87 (100%) |
138 |
137 (95.1%) |
148 (93.1%) |
118 (80.8%) |
63 (37.1%) |
7. Total No. of Author Self Cites |
61 |
104 (4.9%) |
141 (5.8%) |
105 (6.3%) |
81 (5.3%) |
36 (3.1%) |
9 (6.6%) |
8. No. of Hot Papers |
1 (2.3%) |
1 (1.0%) |
9 |
2 (1.4%) |
4 |
4 (2.7%) |
2 (1.2%) |
APPENDIX:
Bibliometric Analysis for Papers on Topics Related to Particulate Matter (PM)
This is a bibliometric analysis of the papers prepared by intramural and extramural researchers of the U.S. Environmental Protection Agency (EPA) on topics related to particulate matter (PM). For this analysis, 904 papers were reviewed. These 904 papers, published from 1998 to 2005, were cited 9,578 times in the journals covered by Thomson’s Web of Science.2 Of these 904 papers, 734 (81%) have been cited at least once in a journal.
The analysis was completed using Thomson’s Essential Science Indicators (ESI) and Journal Citation Reports (JCR) as benchmarks. ESI provides access to a unique and comprehensive compilation of essential science performance statistics and science trends data derived from Thomson’s databases. The chief indicators of output, or productivity, are journal article publication counts. For influence and impact measures, ESI employs both total citation counts and cites per paper scores. The former reveals gross influence while the latter shows weighted influence, also called impact. JCR presents quantifiable statistical data that provide a systematic, objective way to evaluate the world’s leading journals and their impact and influence in the global research community.
Summary of Analysis
More than one-third of the PM publications are highly cited papers. A review of the citations indicates that 321 (35.5%) of the PM papers qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications. Seventy-four (8.2%) of the PM papers qualify as highly cited when using the criteria for the top 1%. Thirteen (1.4%) of these papers qualify as very highly cited (in the top 0.1%), and two papers actually meet the top 0.01% threshold.
The PM papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, in 10 of the 12 fields in which the EPA PM papers were published, the ratio of actual to expected cites is greater than 1, indicating that the PM papers are more highly cited than the average papers in those fields.
Nearly one-third of the PM papers are published in very high impact journals. Two-hundred fifty-four (254) of 904 papers were published in the top 10% of journals ranked by JCR Impact Factor, representing 28% of EPA’s PM papers. Nearly one-third of the PM papers are published in the top 10% of journals ranked by JCR Immediacy Factor. Two-hundred sixty-seven (267) of the 904 papers appear in the top 10% of journals, representing 29.5% of EPA’s PM papers.
Twenty-three of the PM papers qualify as hot papers. Using the hot paper thresholds established by ESI as a benchmark, 23 hot papers, representing 2.5% of the PM papers, were identified in the analysis.
The author self-citation rate is below average. Five hundred thirty-seven (537) of the 9,578 cites are author self-cites. This 5.6% author self-citation rate is below the accepted range of 10-30% author self-citation rate.
Highly Cited PM Publications
The 904 PM papers reviewed for this analysis covered 12 of the 22 ESI fields. The distribution of the papers among these 12 fields and the number of citations by field are presented in Table 1.
Table 1. PM Papers by ESI Fields
No. of Citations |
ESI Field |
No. of EPA PM Papers |
Average Cites/Paper |
2,674 |
Environment/Ecology |
263 |
10.17 |
2,067 |
Engineering |
236 |
8.76 |
1,432 |
Pharmacology & Toxicology |
146 |
9.81 |
872 |
Biology & Biochemistry |
68 |
12.49 |
859 |
Clinical Medicine |
42 |
20.45 |
823 |
Multidisciplinary |
66 |
12.47 |
368 |
Molecular Biology & Genetics |
19 |
19.37 |
295 |
Chemistry |
35 |
8.43 |
144 |
Immunology |
13 |
11.08 |
23 |
Neuroscience & Behavior |
1 |
23.00 |
11 |
Physics |
8 |
1.38 |
10 |
Mathematics |
7 |
1.43 |
Total = 9,578 |
Total = 904 |
|
There were 321 (35.5% of the papers analyzed) highly cited EPA PM papers in 10 of the 12 fields–Environment/Ecology, Engineering, Pharmacology & Toxicology, Clinical Medicine, Multidisciplinary, Biology & Biochemistry, Chemistry, Molecular Biology & Genetics, Immunology, and Mathematics–when using the ESI criteria for the top 10% of papers. Table 2 shows the number of EPA papers in those 10 fields that met the top 10% threshold in ESI. Seventy-four (8.2%) of the papers analyzed qualified as highly cited when using the ESI criteria for the top 1% of papers. These papers covered five fields–Environment/Ecology, Engineering, Clinical Medicine, Biology & Biochemistry, and Multidisciplinary. Table 3 shows the 74 papers by field that met the top 1% threshold in ESI. There were 13 very highly cited EPA PM papers in three fields–Engineering, Environment/Ecology, and Clinical Medicine. These 13 papers met the top 0.1% threshold in ESI (1.4% of the papers analyzed). Two of these 13 PM papers actually met the top 0.01% threshold in ESI (i.e., the two papers by Drewnick).
Table 2. Number of Highly Cited PM Papers by Field (top 10%)
Citations |
ESI Field |
No. of Papers |
Average Cites/Paper |
% of EPA Papers in Field |
2,073 |
Environment/Ecology |
106 |
19.56 |
40.3% |
1,863 |
Engineering |
123 |
15.15 |
52.12% |
873 |
Pharmacology & Toxicology |
30 |
29.10 |
20.55% |
757 |
Clinical Medicine |
14 |
54.07 |
33.33% |
632 |
Multidisciplinary |
23 |
27.48 |
34.85% |
395 |
Biology & Biochemistry |
9 |
43.89 |
13.24% |
182 |
Chemistry |
9 |
20.22 |
25.71% |
134 |
Molecular Biology & Genetics |
2 |
67.00 |
10.53% |
119 |
Immunology |
3 |
39.67 |
23.08% |
5 |
Mathematics |
2 |
2.50 |
28.57% |
Table 3. Number of Highly Cited PM Papers by Field (top 1%)
Citations |
ESI Field |
No. of Papers |
Average Cites/Paper |
% of EPA Papers in Field |
1,206 |
Engineering |
50 |
24.12 |
21.19% |
778 |
Environment/Ecology |
18 |
43.22 |
6.84% |
399 |
Clinical Medicine |
2 |
199.5 |
4.76% |
226 |
Biology & Biochemistry |
3 |
75.33 |
4.35% |
88 |
Multidisciplinary |
1 |
88.00 |
1.52% |
The citations for the highly cited papers in the top 1% are presented in Tables 4 through 8. The citations for the very highly cited papers are listed in Table 9.
Table 4. Highly Cited PM Papers in the Field of Engineering (top 1%)
No. of Cites |
First Author |
Paper |
79 |
Yu JZ |
Identification of products containing -COOH, -OH, and -C=O in atmospheric oxidation of hydrocarbons. Environmental Science & Technology 1998;32(16):2357-2370. |
33 |
Kleeman MJ |
Source contributions to the size and composition distribution of atmospheric particles: Southern California in September1996. Environmental Science & Technology 1999;33(23):4331-4341. |
33 |
Zhang Y |
Simulation of aerosol dynamics: A comparative review of algorithms used in air quality models. Aerosol Science and Technology 1999;31(6):487-514. |
37 |
Hughes LS |
Size and composition distribution of atmospheric particles in southern California. Environmental Science & Technology 1999;33(20):3506-3515. |
25 |
Mallina RV |
High speed particle beam generation: A dynamic focusing mechanism for selecting ultrafine particles, Aerosol Science and Technology 2000;33(1-2):87-104. |
26 |
Christoforou CS |
Trends in fine particle concentration and chemical composition in Southern California. Journal of the Air & Waste Management Association 2000;50(1):43-53. |
29 |
Hughes LS |
Evolution of atmospheric particles along trajectories crossing the Los Angeles basin. Environmental Science & Technology 2000;34(15):3058-3068. |
32 |
Ansari AS |
Water absorption by secondary organic aerosol and its effect an inorganic aerosol behavior. Environmental Science & Technology 2000;34(1):71-77. |
33 |
Tobias HJ |
Thermal desorption mass spectrometric analysis of organic aerosol formed from reactions of 1-tetradecene and O-3 in the presence of alcohols and carboxylic acids. Environmental Science & Technology 2000;34(11):2105-2115. |
37 |
Allen JO |
Particle detection efficiencies of aerosol time of flight mass spectrometers under ambient sampling conditions. Environmental Science & Technology 2000;34(1):211-217. |
40 |
Long CM |
Characterization of indoor particle sources using continuous mass and size monitors. Journal of the Air & Waste Management Association 2000;50(7):1236-1250. |
40 |
Sarnat JA |
Assessing the relationship between personal particulate and gaseous exposures of senior citizens living in Baltimore, MD. Journal of the Air & Waste Management Association 2000;50(7):1184-1198. |
43 |
Stolzenburg MR |
Method for the automated measurement of fine particle nitrate in the atmosphere. Environmental Science & Technology 2000;34(5):907-914. |
75 |
Jayne JT |
Development of an aerosol mass spectrometer for size and composition analysis of submicron particles. Aerosol Science and Technology 2000;33(1-2):49-70. |
19 |
Vette AF |
Characterization of indoor-outdoor aerosol concentration relationships during the Fresno PM exposure studies. Aerosol Science and Technology 2001;34(1):118-126. |
21 |
Mosley RB |
Penetration of ambient fine particles into the indoor environment. Aerosol Science and Technology 2001;34(1):127-136. |
23 |
Tolocka MP |
East versus West in the US: Chemical characteristics of PM2.5 during the winter of 1999. Aerosol Science and Technology 2001;34(1):88-96. |
24 |
Seinfeld JH |
Modeling the formation of secondary organic aerosol (SOA). 2. The predicted effects of relative humidity on aerosol formation in the alpha-pinene-, beta-pinene-, sabinene-, Delta(3)-Carene-, and cyclohexene-ozone systems. Environmental Science & Technology 2001;35(9):1806-1817. |
26 |
Pankow JF |
Modeling the formation of secondary organic aerosol. 1. Application of theoretical principles to measurements obtained in the α-pinene/, β- pinene/, sabinene/, Δ(3)-carene/, and cyclohexene/ozone systems. Environmental Science & Technology 2001;35(6):1164-1172. |
29 |
Fine PM |
Chemical characterization of fine particle emissions from fireplace combustion of woods grown in the northeastern United States. Environmental Science & Technology 2001;35(13):2665-2675. |
31 |
Lewtas J |
Comparison of sampling methods for semi-volatile organic carbon associated with PM2.5. Aerosol Science and Technology 2001;34 (1):9-22. |
31 |
Kamens RM |
Modeling aerosol formation from alpha-pinene plus NOx in the presence of natural sunlight using gas-phase kinetics and gas-particle partitioning theory. Environmental Science & Technology 2001;35 (7):1394-1405. |
33 |
Jang MS |
Atmospheric secondary aerosol formation by heterogeneous reactions of aldehydes in the presence of a sulfuric acid aerosol catalyst. Environmental Science & Technology 2001;35(24):4758-4766. |
34 |
Long CM |
Using time- and size-resolved particulate data to quantify indoor penetration and deposition behavior. Environmental Science & Technology 2001;35(10):2089-2099. |
50 |
Woo KS |
Measurement of Atlanta aerosol size distributions: Observations of ultrafine particle events. Aerosol Science and Technology 2001;34(1):75-87. |
56 |
Weber RJ |
A particle-into-liquid collector for rapid measurement of aerosol bulk chemical composition. Aerosol Science and Technology 2001;35(3):718-727. |
12 |
Hays MD |
Speciation of gas-phase and fine particle emissions from burning of foliar fuels. Environmental Science & Technology 2002;36(11):2281-2295. |
13 |
Frey HC |
Quantification of variability and uncertainty in lawn and garden equipment NOx and total hydrocarbon emission factors. Journal of the Air & Waste Management Association 2002;52(4):435-448. |
13 |
Kim S |
Size distribution and diurnal and seasonal trends of ultrafine particles in source and receptor sites of the Los Angeles basin. Journal of the Air & Waste Management Association 2002;52(3):297-307. |
14 |
Zhang XF |
A numerical characterization of particle beam collimation by an aerodynamic lens-nozzle system: Part I. An individual lens or nozzle. Aerosol Science and Technology 2002;36(5):617-631. |
14 |
Lim HJ |
Origins of primary and secondary organic aerosol in Atlanta: Results' of time-resolved measurements during the Atlanta Supersite experiment. Environmental Science & Technology 2002;36(21):4489-4496. |
15 |
Phares DJ |
Performance of a single ultrafine particle mass spectrometer. Aerosol Science and Technology 2002;36(5):583-592. |
28 |
McMurry PH |
The relationship between mass and mobility for atmospheric particles: A new technique for measuring particle density. Aerosol Science and Technology 2002;36(2):227-238. |
35 |
Zhu YF |
Concentration and size distribution of ultrafine particles near a major highway. Journal of the Air & Waste Management Association 2002;52(9):1032-1042. |
7 |
Maykut NN |
Source apportionment of PM2.5 at an urban IMPROVE site in Seattle, Washington. Environmental Science & Technology 2003;37(22):5135-5142. |
8 |
Lake DA |
Mass spectrometry of individual particles between 50 and 750 nm in diameter at the Baltimore Supersite. Environmental Science & Technology 2003;37(15):3268-3274. |
9 |
Jang MS |
Particle growth by acid-catalyzed heterogeneous reactions of organic carbonyls on preexisting aerosols. |
12 |
Offenberg JH |
Persistent organic pollutants in the dusts that settled across lower Manhattan after September 11, 2001. Environmental Science & Technology 2003;37(3):502-508. |
12 |
Lewis CW |
Source apportionment of phoenix PM2.5 aerosol with the Unmix receptor model. Journal of the Air & Waste Management Association 2003;53(3):325-338. |
20 |
Park K |
Relationship between particle mass and mobility for diesel exhaust particles. Environmental Science & Technology 2003;37(3):577-583. |
3 |
Stanier CO |
A method for the in situ measurement of fine aerosol water content of ambient aerosols: The dry-ambient aerosol size spectrometer (DAASS). Aerosol Science and Technology 2004;38(Suppl 1):215-228. |
6 |
Stanier CO |
Nucleation events during the Pittsburgh air quality study: Description and relation to key meteorological, gas phase, and aerosol parameters. Aerosol Science and Technology 2004;38(Suppl 1):253-264. |
3 |
Huggins FE |
Quantifying hazardous species in particulate matter derived from fossil-fuel. Environmental Science & Technology 2004;38(6):1836-1842. |
3 |
Kim E |
Analysis of ambient particle size distributions using unmix and positive matrix factorization. Environmental Science & Technology 2004;38(1):202-209. |
3 |
Keywood MD |
Secondary organic aerosol formation from cyclohexene ozonolysis: Effect of OH scavenger and the role of radical chemistry. Environmental Science & Technology 2004;38(12):3343-3350. |
7 |
Cho AK |
Determination of four quinones in diesel exhaust particles, SRM 1649a, an atmospheric PM2.5. Aerosol Science and Technology 2004;38(Suppl 1):68-81. |
5 |
Canagaratna MR |
Chase studies of particulate emissions from in-use New York City vehicles. Aerosol Science and Technology 2004;38(6):555-573. |
6 |
Hogrefe O |
Development, operation and applications of an aerosol generation, calibration and research facility. Aerosol Science and Technology 2004;38(Suppl 1):196-214. |
8 |
Drewnick F |
Measurement of ambient aerosol composition during the PMTACS-NY 2001 using an aerosol mass spectrometer. Part II: Chemically speciated mass distributions. Aerosol Science and Technology 2004;38(Suppl 1):104-117. |
11 |
Drewnick F |
Measurement of ambient aerosol composition during the PMTACS-NY 2001 using an aerosol mass spectrometer. Part I: Mass concentrations. Aerosol Science and Technology 2004;38 (Suppl 1):92-103. |
Table 5. Highly Cited PM Papers in the Field of Environment/Ecology (top 1%)
No. of Cites |
First Author |
Paper |
92 |
Simoneit BRT |
Levoglucosan, a tracer for cellulose in biomass burning and atmospheric particles. Atmospheric Environment 1999;33(2):173-182. |
97 |
Yu JZ |
Gas-phase ozone oxidation of monoterpenes: Gaseous and particulate products. Journal of Atmospheric Chemistry 1999;34(2):207-258. |
110 |
Liao DP |
Daily variation of particulate air pollution and poor cardiac autonomic control in the elderly. Environmental Health Perspectives 1999;107(7):521-525. |
74 |
Schwartz J |
Fine particles are more strongly associated than coarse particles with acute respiratory health effects in schoolchildren. Epidemiology 2000;11(1):6-10. |
96 |
Laden F |
Association of fine particulate matter from different sources with daily mortality in six US cities. Environmental Health Perspectives 2000;108(10):941-947. |
43 |
Dockery DW |
Epidemiologic evidence of cardiovascular effects of particulate air pollution. Environmental Health Perspectives 2001;109(Suppl 4):483-486. |
69 |
Oberdorster G |
Pulmonary effects of inhaled ultrafine particles. International Archives of Occupational and Environmental Health 2001;74 (1):1-8. |
26 |
Zanobetti A |
The temporal pattern of mortality responses to air pollution: A multicity assessment of mortality. Epidemiology 2002;13(1):87-93. |
32 |
Zhu YF |
Study of ultrafine particles near a major highway with heavy-duty diesel traffic. Atmospheric Environment 2002;36(27):4323-4335. |
32 |
Lioy PJ |
Characterization of the dust/smoke aerosol that settled east of the World Trade Center (WTC) in Lower Manhattan after the collapse of the WTC 11 September 2001. Environmental Health Perspectives 2002;110(7):703-714. |
11 |
Drewnick F |
Intercomparison and evaluation of four semi-continuous PM2.5 sulfate instruments. Atmospheric Environment 2003;37(24):3335-3350. |
11 |
Jang M |
Organic aerosol growth by acid-catalyzed heterogeneous reactions of octanal in a flow reactor. Atmospheric Environment 2003;37(15):2125-2138. |
11 |
McGee JK |
Chemical analysis of World Trade Center fine particulate matter for use in toxicologic assessment. Environmental Health Perspectives 2003;111(7):972-980. |
21 |
Orsini DA |
Refinements to the particle-into-liquid sampler (PILS) for ground and airborne measurements of water soluble aerosol composition. Atmospheric Environment 2003;37(9-10):1243-1259. |
41 |
Li N |
Ultrafine particulate pollutants induce oxidative stress and mitochondrial damage. Environmental Health Perspectives 2003;111(4):455-460. |
4 |
DeMarini DM |
Bioassay-directed fractionation and Salmonella mutagenicity of automobile and forklift diesel exhaust particles. Environmental Health Perspectives 2004;112(8):814-819. |
4 |
Landrigan PJ |
Health and environmental consequences of the World Trade Center disaster. Environmental Health Perspectives 2004;112(6):731-739. |
4 |
Singh P |
Sample characterization of automobile and forklift diesel exhaust particles and comparative pulmonary toxicity in mice. Environmental Health Perspectives 2004;112(8):820-825. |
Table 6. Highly Cited PM Papers in the Field of Clinical Medicine (top 1%)
No. of Cites |
First Author |
Paper |
124 |
Abbey DE |
Long-term inhalable particles and other air pollutants related to mortality in nonsmokers. American Journal of Respiratory and Critical Care Medicine 1999;159(2):373-382. |
275 |
Pope CA |
Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA-Journal of the American Medical Association 2002;287(9):1132-1141. |
Table 7. Highly Cited PM Papers in the Field of Biology & Biochemistry (top 1%)
No. of Cites |
First Author |
Paper |
6 |
Pope CA |
Cardiovascular mortality and long-term exposure to particulate air pollution–epidemiological evidence of general pathophysiological pathways of disease. Circulation 2004;109(1):71-77. |
96 |
Peters A |
Increased particulate air pollution and the triggering of myocardial infarction. Circulation 2001;103(23):2810-2815. |
124 |
Gold DR |
Ambient pollution and heart rate variability. Circulation 2000;101(11):1267-1273. |
Table 8. Highly Cited PM Papers in the Field of Multidisciplinary (top 1%)
No. of Cites |
First Author |
Paper |
88 |
Gard EE |
Direct observation of heterogeneous chemistry in the atmosphere. Science 1998;279(5354):1184-1187. |
Table 9. Very Highly Cited PM Papers (Top 0.1%)
Field |
No. of Cites |
First Author |
Paper |
Clinical Medicine |
275 |
Pope CA |
Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA-Journal of the American Medical Association 2002;287(9):1132-1141. |
Engineering |
75 |
Jayne JT |
Development of an aerosol mass spectrometer for size and composition analysis of submicron particles. Aerosol Science and Technology 2000;33(1-2):49-70. |
50 |
Woo KS |
Measurement of Atlanta aerosol size distributions: Observations of ultrafine particle events. Aerosol Science and Technology 2001;34(1):75-87. |
|
Engineering |
56 |
Weber RJ |
A particle-into-liquid collector for rapid measurement of aerosol bulk chemical composition. Aerosol Science and Technology 2001;35(3):718-727. |
35 |
Zhu YF |
Concentration and size distribution of ultrafine particles near a major highway. Journal of the Air & Waste Management Association 2002;52(9):1032-1042. |
|
20 |
Park K |
Relationship between particle mass and mobility for diesel exhaust particles. Environmental Science & Technology 2003;37(3):577-583. |
|
11 |
Drewnick |
Measurement of ambient aerosol composition during the PMTACS-NY 2001 using an aerosol mass spectrometer. Part I: Mass concentrations. Aerosol Science and Technology 2004;38 (Suppl 1):92-103. |
|
8 |
Drewnick |
Measurement of ambient aerosol composition during the PMTACS-NY 2001 using an aerosol mass spectrometer. Part II: Chemically speciated mass distributions. Aerosol Science and Technology 2004;38(Suppl 1):104-117. |
|
7 |
Cho AK |
Determination of four quinones in diesel exhaust particles, SRM 1649a, an atmospheric PM2.5. Aerosol Science and Technology 2004;38(Suppl 1):68-81. |
|
6 |
Hogrefe O |
Development, operation and applications of an aerosol generation, calibration and research facility. Aerosol Science and Technology 2004;38(Suppl 1):196-214. |
|
6 |
Stanier CO |
Nucleation events during the Pittsburgh air quality study: Description and relation to key meteorological, gas phase, and aerosol parameters. Aerosol Science and Technology 2004;38(Suppl 1):253-264. |
|
5 |
Canagaratna MR |
Chase studies of particulate emissions from in-use New York City vehicles. Aerosol Science and Technology 2004;38(6):555-573. |
|
Environment/ |
41 |
Li N |
Ultrafine particulate pollutants induce oxidative stress and mitochondrial damage. Environmental Health Perspectives 2003;111(4):455-460. |
Ratio of Actual Cites to Expected Citation Rates
The expected citation rate is the average number of cites that a paper published in the same journal in the same year and of the same document type (article, review, editorial, etc.) has received from the year of publication to the present. Using the ESI average citation rates for papers published by field as the benchmark, in 10 of the 12 fields in which the EPA PM papers were published, the ratio of actual to expected cites is greater than 1, indicating that the EPA papers are more highly cited than the average papers in those fields (see Table 10).
Table 10. Ratio of Average Cites to Expected Cites for PM Papers by Field
ESI Field |
Total Cites |
Expected Cite Rate |
Ratio |
Biology & Biochemistry |
872 |
787.66 |
1.11 |
Chemistry |
295 |
211.66 |
1.39 |
Clinical Medicine |
859 |
226.30 |
3.80 |
Engineering |
2,067 |
378.11 |
5.45 |
Environment/Ecology |
2,674 |
966.32 |
2.77 |
Immunology |
144 |
103.38 |
1.39 |
Mathematics |
10 |
6.34 |
1.58 |
Molecular Biology & Genetics |
368 |
374.93 |
0.98 |
Multidisciplinary |
823 |
268.71 |
3.06 |
Neuroscience & Behavior |
23 |
18.39 |
1.25 |
Pharmacology & Toxicology |
1,432 |
841.16 |
1.70 |
Physics |
11 |
37.85 |
0.29 |
JCR Benchmarks
The Impact Factor is a well known metric in citation analysis. It is a measure of the frequency with which the average article in a journal has been cited in a particular year. The Impact Factor helps evaluate a journal’s relative importance, especially when compared to others in the same field. The Impact Factor is calculated by dividing the number of citations in the current year to articles published in the 2 previous years by the total number of articles published in the 2 previous years.
Table 11 indicates the number of PM papers published in the top 10% of journals, based on the JCR Impact Factor. Two-hundred fifty-four (254) of 904 papers were published in the top 10% of journals, representing 28% of EPA’s PM papers.
Table 11. PM Papers in Top 10% of Journals by JCR Impact Factor
EPA PM Papers in that Journal |
Journal |
Impact Factor |
JCR IF Rank |
64 |
Environmental Health Perspectives |
3.408 |
538 |
62 |
Environmental Science & Technology |
3.592 |
487 |
26 |
American Journal of Physiology-Lung Cellular and Molecular Physiology |
3.735 |
435 |
20 |
Epidemiology |
4.220 |
350 |
17 |
American Journal of Respiratory and Critical Care Medicine |
8.876 |
100 |
17 |
American Journal of Respiratory Cell and Molecular Biology |
4.015 |
380 |
7 |
Analytical Chemistry |
5.250 |
248 |
5 |
Circulation |
11.164 |
72 |
4 |
Journal of Biological Chemistry |
6.482 |
179 |
4 |
Journal of Immunology |
6.702 |
167 |
3 |
Science |
29.781 |
11 |
3 |
Free Radical Biology and Medicine |
5.063 |
260 |
3 |
American Journal of Epidemiology |
4.486 |
310 |
3 |
Thorax |
4.188 |
356 |
2 |
Lancet |
18.316 |
28 |
2 |
Chest |
3.264 |
585 |
2 |
Chemical Research in Toxicology |
3.332 |
555 |
1 |
New England Journal of Medicine |
34.833 |
5 |
1 |
JAMA-Journal of the American Medical Association |
21.455 |
22 |
1 |
Journal of Clinical Investigation |
14.307 |
44 |
1 |
Proceedings of the National Academy of Sciences |
10.272 |
81 |
1 |
Cancer Research |
8.649 |
105 |
1 |
FASEB Journal |
7.172 |
149 |
1 |
Journal of Allergy and Clinical Immunology |
6.831 |
162 |
1 |
Advanced Drug Delivery Reviews |
6.588 |
170 |
1 |
Critical Care Medicine |
4.195 |
353 |
1 |
Journal of Leukocyte Biology |
4.180 |
357 |
Total = 254 |
|
|
|
Immediacy Index
The journal Immediacy Index is a measure of how quickly the average article in a journal is cited. It indicates how often articles published in a journal are cited within the year they are published. The Immediacy Index is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year.
Table 12 indicates the number of EPA papers published in the top 10% of journals, based on the JCR Immediacy Index. Two-hundred sixty-seven (267) of the 904 papers appear in the top 10% of journals, representing 29.5% of EPA’s PM papers.
Table 12. PM Papers in Top 10% of Journals by JCR Immediacy Index
EPA Papers in that Journal |
Journal |
Immediacy Index |
JCR II Rank |
64 |
Environmental Health Perspectives |
0.869 |
304 |
52 |
Journal of Geophysical Research - Atmospheres |
0.827 |
334 |
26 |
American Journal of Physiology-Lung Cellular and Molecular Physiology |
0.654 |
496 |
20 |
Epidemiology |
0.938 |
264 |
19 |
Journal of Aerosol Science |
0.686 |
462 |
17 |
American Journal of Respiratory Cell and Molecular Biology |
0.623 |
546 |
17 |
American Journal of Respiratory and Critical Care Medicine |
2.461 |
56 |
7 |
Analytical Chemistry |
0.657 |
493 |
5 |
Circulation |
1.946 |
82 |
4 |
Journal of Immunology |
0.988 |
239 |
4 |
Philosophical Transactions of the Royal Society of London Series A-Mathematical Physical and Engineering Sciences |
0.867 |
305 |
4 |
Journal of Biological Chemistry |
1.231 |
160 |
3 |
American Journal of Epidemiology |
0.908 |
281 |
3 |
Free Radical Biology and Medicine |
0.712 |
432 |
3 |
Thorax |
1.237 |
158 |
3 |
Science |
5.589 |
12 |
2 |
Biometals |
0.717 |
424 |
2 |
Lancet |
5.826 |
10 |
1 |
Journal of Chemical Physics |
0.661 |
487 |
1 |
Journal of Clinical Investigation |
2.946 |
41 |
1 |
Critical Care Medicine |
1.103 |
192 |
1 |
Journal of Allergy and Clinical Immunology |
1.465 |
123 |
1 |
Journal of Leukocyte Biology |
0.671 |
473 |
1 |
Cancer Research |
0.935 |
268 |
1 |
FASEB Journal |
1.247 |
154 |
1 |
New England Journal of Medicine |
11.719 |
2 |
1 |
Advanced Drug Delivery Reviews |
0.805 |
352 |
1 |
Proceedings of the National Academy of Sciences |
1.935 |
83 |
1 |
American Journal of Industrial Medicine |
0.616 |
552 |
1 |
JAMA-Journal of the American Medical Association |
6.048 |
9 |
Total = 267 |
|
|
Hot Papers
ESI establishes citation thresholds for hot papers, which are selected from the highly cited papers in different fields, but the time frame for citing and cited papers is much shorter–papers must be cited within 2 years of publication and the citations must occur in a 2-month time period. Papers are assigned to 2-month periods and thresholds are set for each period and field to select 0.1% of papers. There were no hot papers identified for the current 2-month period (i.e., January-February 2005), but there were a number of hot papers identified from previous periods.
Using the hot paper thresholds established by ESI as a benchmark, 23 hot papers, representing 2.5% of the PM papers, were identified in four fields–Biology & Biochemistry, Clinical Medicine, Environment/Ecology, and Engineering. The hot papers are listed in Table 13.
Table 13. Hot Papers Identified Using ESI Thresholds
Field |
ESI Hot Papers Threshold |
No. of Cites in 2-Month Period |
Paper |
Biology & Biochemistry |
10 |
11 cites in July-August 2001 |
Gold DR, et al. Ambient pollution and heart rate variability. Circulation 2000;101(11):1267-1273. |
Clinical Medicine |
12 |
15 cites in November-December 2003 |
Pope CA, et al. Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA–Journal of the American Medical Association 2002;287(9):1132-1141. |
Environment/ Ecology |
8 |
9 cites in May-June 2004 |
Li N, et al. Ultrafine particle pollutants induce oxidative stress and mitochondrial damage. Environmental Health Perspectives 2003;111(4):455-460. |
|
10 cites in June-July 2004 |
Orsini DA, et al. Refinements to the particle-into-liquid sampler (PILS) for ground and airborne measurements of water soluble aerosol composition. Atmospheric Environment 2003;37(9-10):1243-1259. |
|
|
9 cites in April-May 2004 |
Lioy PJ, et al. Characterization of the dust/smoke aerosol that settled east of the World Trade Center (WTC) in Lower Manhattan after the collapse of the WTC 11 September 2001. Environmental Health Perspectives 2002;110(7):703-714. |
|
|
9 cites in September-October 2002 |
Laden F, et al. Association of fine particulate matter from different sources with daily mortality in six US cities. Environmental Health Perspectives 2000;108(10):941-947. |
|
Engineering |
4 |
4 cites in May-June 2002 |
Hughes LS, et al. Evolution of atmospheric particles along trajectories crossing the Los Angeles basin. Environmental Science & Technology 2000;34(15):3058-3068. |
|
4 cites in November-December 2001 |
Ansari AS, Pandis SN. Water absorption by secondary organic aerosol and its effect on inorganic aerosol behavior. Environmental Science & Technology 2000;34(1):71-77. |
|
|
4 cites in July 2002 |
Long CM, et al. Characterization of indoor particle sources using continuous mass and size monitors. Journal of the Air & Waste Management Association 2000;50(7):1236-1250. |
|
|
4 cites in May-June 2002 |
Jayne JT, et al. Development of an aerosol mass spectrometer for size and composition analysis of submicron particles. Aerosol Science & Technology 2000;33(1-2):49-70. |
|
|
4 cites in December 2002-January 2003 |
Fine PM, et al. Chemical characterization of fine particle emissions from fireplace combustion of woods grown in the northeastern United States. Environmental Science & Technology 2001;35(13):2665-2675. |
|
|
5 cites in September-October 2003 |
Jang MS, Kamens RM. Atmospheric secondary aerosol formation by heterogeneous reactions of aldehydes in the presence of a sulfuric acid aerosol catalyst. Environmental Science & Technology 2001;35(24):4758:4766. |
|
Engineering |
4 |
4 cites in June-July 2000 |
Yu JZ, et al. Identification of products containing -COOH, -OH, and -C=O in atmospheric oxidation of hydrocarbons. Environmental Science & Technology 1998;32(16):2357-2370. |
|
5 cites in October-November 2001 |
Kleeman MJ, et al. Source contributions to the size and composition distribution of atmospheric particles: Southern California in September 1996. Environmental Science & Technology 1999;33(23):4331-4341. |
|
|
4 cites in May 2002 |
Mallina RV, et al. High speed particle beam generation: a dynamic focusing mechanism for selecting ultrafine particles. Aerosol Science and Technology 2000;33(1-2):87-104. |
|
|
4 cites in November-December 2001 |
Christoforou CS, et al. Trends in fine particle concentration and chemical composition in Southern California. Journal of the Air & Waste Management Association 2000;50(1):43-53. |
|
|
4 cites in June-July 2002 |
Sarnat JA, et al. Assessing the relationship between personal particulate and gaseous exposures of senior citizens living in Baltimore, MD. Journal of the Air & Waste Management Association 2000;50(7):1184-1198. |
|
|
4 cites in February-March 2003 |
McMurry PH, et al. The relationship between mass and mobility for atmospheric particles: a new technique for measuring particle density. Aerosol Science and Technology 2002;36(2):227-238. |
|
|
6 cites in April-May 2004 |
Zhu YF, et al. Concentration and size distribution of ultrafine particles near a major highway. Journal of the Air & Waste Management Association 2002;52(9):1032-1042. |
|
|
4 cites in April-May 2004 |
Offenberg JH, et al. Persistent organic pollutants in the dusts that settled across lower Manhattan after September 11, 2001. Environmental Science & Technology 2003;37(3):502-508. |
|
|
5 cites in May-June 2004 |
Park K, et al. Relationship between particle mass and mobility for diesel exhaust particles. Environmental Science & Technology 2003;37(3):577-583. |
|
|
4 cites in November 2004 |
Canagaratna MR, et al. Chase studies of particulate emissions from in-use New York City vehicles. Aerosol Science and Technology 2004;38(6):555-573. |
|
Engineering |
4 |
4 cites in November-December 2004 |
Drewnick F, et al. Measurement of ambient aerosol composition during the PMTACS-NY 2001 using an aerosol mass spectrometer, Part I: mass concentrations. Aerosol Science and Technology 2004;38(Suppl 1):92-103. |
Author Self-Citation
Self-citations are journal article references to articles from that same author (i.e., the first author). Because higher author self-citation rates can inflate the number of citations, the author self-citation rate was calculated for the PM papers. Of the 9,578 total cites, 537 are author self-cites–a 5.6% author self-citation rate. Garfield and Sher3 found that authors working in research-based disciplines tend to cite themselves on the average of 20% of the time. MacRoberts and MacRoberts4 claim that approximately 10% to 30% of all the citations listed fall into the category of author self-citation. Therefore, the 5.6% self-cite rate for the PM papers is below the range for author self-citation.
1 The total number of PM papers analyzed in the Bibliometric Analysis for Papers on Topics Related to Particulate Matter (PM) prepared in March 2005 was 904. This supplement provides data for only 895 of those papers because one paper published in 1997 and eight papers published in 2005 were excluded from this supplemental analysis by year.
2 Thomson’s Web of Science provides access to current and retrospective multidisciplinary information from approximately 8,700 of the most prestigious, high impact research journals in the world. Web of Science also provides cited reference searching.
3 Garfield E, Sher IH. New factors in the evaluation of scientific literature through citation indexing. American Documentation 1963;18(July):195-201.
4 MacRoberts MH, MacRoberts BR. Problems of citation analysis: a critical review. Journal of the American Society of Information Science 1989;40(5):342-349.