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Bibliometrics
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Bibliometric Analysis for Papers on Topics Related to Pollution Prevention (P2)
March 29, 2005
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 pollution prevention (P2). For this analysis, 509 papers were reviewed. These 509 papers, published from 1995 to 2005, were cited 8,277 times in the journals covered by Thomson’s Web of Science1. Of these 509 papers, 401 (79%) 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 P2 publications are highly cited papers. A review of the citations indicates that 174 (34.2%) of the P2 papers qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications. Thirty-one (6.1%) of the P2 papers qualify as highly cited when using the criteria for the top 1%. Nine (1.8%) of these papers qualify as very highly cited (in the top 0.1%), and two papers actually meet the top 0.01% threshold.
The P2 papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, in 8 of the 12 fields in which the EPA P2 papers were published, the ratio of actual to expected cites is greater than 1, indicating that the P2 papers are more highly cited than the average papers in those fields.
Nearly one-third of the P2 papers are published in very high impact journals. One-hundred fifty-five (155) of 509 papers were published in the top 10% of journals ranked by JCR Impact Factor, representing 30.4% of EPA’s P2 papers. Nearly one-third of the P2 papers are published in the top 10% of journals ranked by JCR Immediacy Factor. One-hundred fifty-seven (157) of the 509 papers appear in the top 10% of journals, representing 30.8% of EPA’s P2 papers.
Twelve of the P2 papers qualify as hot papers. Using the hot paper thresholds established by ESI as a benchmark, 12 hot papers, representing 2.4% of the P2 papers, were identified in the analysis.
The author self-citation rate is below average. Three-hundred sixty-four (364) of the 8,277 cites are author self-cites. This 4.4% author self-citation rate is below the accepted range of 10-30% author self-citation rate.
Highly Cited P2 Publications
The 509 P2 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. P2 Papers by ESI Fields
No. of Citations |
ESI Field |
No. of EPA P2 Papers |
Average Cites/Paper |
6,099 |
Chemistry |
317 |
19.24 |
1,358 |
Engineering |
92 |
14.76 |
258 |
Biology & Biochemistry |
28 |
9.21 |
215 |
Multidisciplinary |
1 |
215.00 |
102 |
Environment/Ecology |
27 |
3.78 |
83 |
Materials Science |
26 |
3.19 |
80 |
Computer Science |
8 |
10.00 |
40 |
Economics & Business |
2 |
20.00 |
36 |
Physics |
3 |
12.00 |
4 |
Mathematics |
2 |
2.00 |
1 |
Pharmacology & Toxicology |
2 |
0.50 |
1 |
Social Science, general |
1 |
1.00 |
Total = 8,277 |
Total = 509 |
There were 174 (34.2% of the papers analyzed) highly cited EPA P2 papers in 9 of the 12 fields—Chemistry, Engineering, Multidisciplinary, Biology & Biochemistry, Computer Science, Economics & Business, Materials Science, Physics, and Environment/Ecology—when using the ESI criteria for the top 10% of papers. Table 2 shows the number of EPA papers in those 9 fields that met the top 10% threshold in ESI. Thirty-one (6.1%) of the papers analyzed qualified as highly cited when using the ESI criteria for the top 1% of papers. These papers covered three fields—Chemistry, Engineering, and Multidisciplinary. Table 3 shows the 31 papers by field that met the top 1% threshold in ESI. There were nine very highly cited EPA P2 papers in two fields—Chemistry and Engineering. These nine papers met the top 0.1% threshold in ESI (1.8% of the papers analyzed). Two of these nine P2 papers actually met the top 0.01% threshold in ESI (i.e., the papers by Savage and Blanchard).
Table 2. Number of Highly Cited P2 Papers by Field (top 10%)
Citations |
ESI Field |
No. of Papers |
Average Cites/Paper |
% of EPA Papers in Field |
4,837 |
Chemistry |
113 |
42.80 |
35.65% |
1,282 |
Engineering |
43 |
29.81 |
46.74% |
215 |
Multidisciplinary |
1 |
215.00 |
100.00% |
102 |
Biology & Biochemistry |
3 |
34.00 |
10.71% |
72 |
Computer Science |
6 |
12.00 |
75.00% |
27 |
Economics & Business |
1 |
27.00 |
50.00% |
26 |
Materials Science |
5 |
5.20 |
19.23% |
19 |
Physics |
1 |
19.00 |
33.33% |
1 |
Environment/Ecology |
1 |
1.00 |
3.70% |
Total = |
174 |
Table 3. Number of Highly Cited P2 Papers by Field (top 1%)
Citations |
ESI Field |
No. of Papers |
Average Cites/Paper |
% of EPA Papers in Field |
2,188 |
Chemistry |
19 |
115.16 |
5.99% |
838 |
Engineering |
11 |
76.18 |
11.96% |
215 |
Multidisciplinary |
1 |
215.00 |
100.00% |
Total = |
31 |
The citations for the highly cited papers in the top 1% are presented in Tables 4 through 6. The citations for the very highly cited papers (top 0.1%) are listed in Table 7.
Table 4. Highly Cited P2 Papers in the Field of Chemistry(top 1%)
No. of Cites |
First Author |
Paper |
296 |
Li CJ |
Aqueous Barbier-Grignard type reaction: scope, mechanism, and synthetic applications. Tetrahedron 1996;52(16):5643-5668. |
83 |
Mesiano AJ |
Supercritical biocatalysis. Chemical Reviews 1999;99(2):623-633. |
119 |
Hudlicky T |
Enzymatic dihydroxylation of aromatics in enantioselective synthesis: expanding asymmetric methodology. Aldrichimica Acta 1999;32(2):35-62. |
152 |
Matyjaszewski K |
Transition metal catalysis in controlled radical polymerization: atom transfer radical polymerization. Chemistry–A European Journal 1999;5(11):3095-3102. |
190 |
Patten TE |
Copper(I)-catalyzed atom transfer radical polymerization. Accounts of Chemical Research 1999;32(10):895-903. |
293 |
Li CJ |
Organic syntheses using indium-mediated and catalyzed reactions in aqueous media. Tetrahedron 1999;55(37):11149-11176. |
380 |
Varma RS |
Solvent-free organic syntheses – using supported reagents and microwave irradiation. Green Chemistry 1999;1(1):43-55. |
42 |
Varma RS |
An expeditious solvent-free route to ionic liquids using microwaves. Chemical Communications 2001;7:643-644. |
66 |
Varma RS |
Solvent-free accelerated organic syntheses using microwaves. Pure and Applied Chemistry 2001;73(1):193-198. |
81 |
Blanchard LA |
High-pressure phase behavior of ionic liquid/CO 2 systems. Journal of Physical Chemistry B 2001;105(12):2437-2444. |
236 |
Huddleston JG |
Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation. Green Chemistry 2001;3(4):156-164. |
31 |
Li CJ |
Quasi-nature catalysis: developing C-C bond formations catalyzed by late transition metals in air and water. Accounts of Chemical Research 2002;35(7):533-538. |
33 |
Li CJ |
Highly efficient Grignard-type imine additions via C-H activation in water and under solvent-free conditions. Chemical Communications 2002;3:268-269. |
51 |
Varma RS |
Clay and clay-supported reagents in organic synthesis. Tetrahedron 2002;58(7):1235-1255. |
57 |
Wei CM |
Enantioselective direct-addition of terminal alkynes to imines catalyzed by copper(I)pybox complex in water and in toluene. Journal of the American Chemical Society 2002;124(20):5638-5639. |
18 |
Holbrey JD |
Crystal polymorphism in 1-butyl-3-methylimidazolium halides: supporting ionic liquid formation by inhibition of crystallization. Chemical Communications 2003;14:1636-1637. |
20 |
Kaar JL |
Impact of ionic liquid physical properties on lipase activity and stability. Journal of the American Chemical Society 2003;125(14):4125-4131. |
32 |
Swatloski RP |
Ionic liquids are not always green: hydrolysis of 1-butyl-3-methylimidazolium hexafluorophosphate. Green Chemistry 2003;5(4):361-363. |
8 |
Li ZG |
Three-component coupling of aldehyde, alkyne, and amine catalyzed by silver in ionic liquid. Tetrahedron Letters 2004;45(11):2443-2446. |
Table 5. Highly Cited P2 Papers in the Field of Engineering (top 1%)
No. of Cites |
First Author |
Paper |
405 |
Savage PE |
Reactions at supercritical conditions – applications and fundamentals. AIChE Journal 1995;41(7):1723-1778. |
45 |
Fan L |
Supercritical-phase alkylation reaction on solid acid catalysts: mechanistic study and catalyst development. Industrial & Engineering Chemistry Research 1997;36(5):1458-1463. |
47 |
Chandler K |
Alkylation reactions in near-critical water in the absence of acid catalysts. Industrial & Engineering Chemistry Research 1997;36(12):5175-5179. |
37 |
Hua JZ |
Enhanced interval analysis for phase stability: Cubic equation of state models. Industrial & Engineering Chemistry Research 1998;37(4):1519-1527. |
47 |
Clancy JL |
UV light inactivation of Cryptosporidium oocysts. Journal American Water Works Association 1998;90(9):92-102. |
55 |
Bukhari Z |
Medium-pressure UV for oocyst inactivation. Journal American Water Works Association 1999;91(3):86-94. |
26 |
Taylor JD |
Experimental measurement of the rate of methyl tert-butyl ether hydrolysis in sub- and supercritical water. Industrial & Engineering Chemistry Research 2001;40(1):67-74. |
121 |
Blanchard LA |
Recovery of organic products from ionic liquids using supercritical carbon dioxide. Industrial & Engineering Chemistry Research 2001;40(1):287-292. |
31 |
Visser AE |
Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg 2+ and Cd 2+: synthesis, characterization, and extraction studies. Environmental Science & Technology 2002;36(11):2523-2529. |
18 |
Abraham MH |
Some novel liquid partitioning systems: water-ionic liquids and aqueous biphasic systems. Industrial & Engineering Chemistry Research 2003;42(3):413-418. |
6 |
Suh S |
System boundary selection in life-cycle inventories using hybrid approaches. Environmental Science & Technology 2004;38(3):657-664. |
Table 6. Highly Cited P2 Papers in the Field of Multidisciplinary (top 1%)
No. of Cites |
First Author |
Paper |
215 |
Blanchard LA |
Green processing using ionic liquids and CO 2. Nature 1999;399(6731):28-29. |
Table 7. Very Highly Cited P2 Papers (Top 0.1%)
Field |
No. of Cites |
First Author |
Paper |
Chemistry |
190 |
Patten TE |
Copper(I)-catalyzed atom transfer radical polymerization. Accounts of Chemical Research 1999;32(10):895-903. |
293 |
Li CJ |
Organic syntheses using indium-mediated and catalyzed reactions in aqueous media. Tetrahedron 1999;55(37):11149-11176. |
|
380 |
Varma RS |
Solvent-free organic syntheses – using supported reagents and microwave irradiation. Green Chemistry 1999;1(1):43-55. |
|
236 |
Huddleston JG |
Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation. Green Chemistry 2001;3(4):156-164. |
|
Engineering |
405 |
Savage PE 2 |
Reactions at supercritical conditions – applications and fundamentals. AIChE Journal 1995;41(7):1723-1778. |
Engineering |
121 |
Blanchard LA2 |
Recovery of organic products from ionic liquids using supercritical carbon dioxide. Industrial & Engineering Chemistry Research 2001;40(1):287-292. |
31 |
Visser AE |
Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg 2+ and Cd 2+: synthesis, characterization, and extraction studies. Environmental Science & Technology 2002;36(11):2523-2529. |
|
18 |
Abraham MH |
Some novel liquid partitioning systems: water-ionic liquids and aqueous biphasic systems. Industrial & Engineering Chemistry Research 2003;42(3):413-418. |
|
6 |
Suh S |
System boundary selection in life-cycle inventories using hybrid approaches. Environmental Science & Technology 2004;38(3):657-664. |
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 8 of the 12 fields in which the EPA P2 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 8).
Table 8. Ratio of Average Cites to Expected Cites for P2 Papers by Field
ESI Field |
Total Cites |
Expected Cite Rate |
Ratio |
Chemistry |
6,099 |
2,023.23 |
3.01 |
Engineering |
1,358 |
220.45 |
6.16 |
Biology & Biochemistry |
258 |
243.53 |
1.06 |
Multidisciplinary |
215 |
4.87 |
44.15 |
Environment/Ecology |
102 |
130.29 |
0.78 |
Materials Science |
83 |
92.2 |
0.90 |
Computer Science |
80 |
20.12 |
3.98 |
Economics & Business |
40 |
11.24 |
3.56 |
Physics |
36 |
20.91 |
1.72 |
Mathematics |
4 |
2.75 |
1.45 |
Pharmacology & Toxicology |
1 |
19.94 |
0.05 |
Social Science, general |
1 |
3.07 |
0.03 |
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 9 indicates the number of P2 papers published in the top 10% of journals, based on the JCR Impact Factor. One-hundred fifty-five (155) of 509 papers were published in the top 10% of journals, representing 30.4% of EPA’s P2 papers.
Table 9. P2 Papers in Top 10% of Journals by JCR Impact Factor
EPA P2 Papers in that Journal |
Journal |
Impact Factor (IF) |
JCR IF Rank |
25 |
Green Chemistry |
2.820 |
767 |
21 |
Journal of Organic Chemistry |
3.297 |
573 |
19 |
Chemical Communications |
4.031 |
376 |
16 |
Macromolecules |
3.621 |
470 |
12 |
Journal of the American Chemical Society |
6.516 |
174 |
10 |
Environmental Science & Technology |
3.592 |
487 |
7 |
Organic Letters |
4.092 |
368 |
4 |
Journal of Physical Chemistry B |
3.679 |
454 |
4 |
Journal of Catalysis |
3.276 |
581 |
4 |
Applied Catalysis A–General |
2.825 |
764 |
3 |
Journal of Bacteriology |
4.175 |
358 |
3 |
Langmuir |
3.098 |
641 |
2 |
Accounts of Chemical Research |
15.000 |
41 |
2 |
Chemistry of Materials |
4.374 |
329 |
2 |
Chemistry–A European Journal |
4.353 |
332 |
2 |
Applied Catalysis B-Environmental |
3.476 |
523 |
2 |
Biomacromolecules |
2.824 |
765 |
1 |
Nature |
30.979 |
8 |
1 |
Chemical Reviews |
21.036 |
23 |
1 |
Angewandte Chemie-International Edition |
8.427 |
108 |
1 |
Advances in Catalysis |
7.889 |
122 |
1 |
Aldrichimica Acta |
7.077 |
151 |
1 |
Advances in Polymer Science |
6.955 |
157 |
1 |
Analytical Chemistry |
5.250 |
248 |
1 |
Journal of Medicinal Chemistry |
4.820 |
278 |
1 |
International Review of Cytology – A Survey of Cell Biology |
4.286 |
340 |
1 |
Applied and Environmental Microbiology |
3.820 |
418 |
1 |
Advanced Synthesis & Catalysis |
3.783 |
426 |
1 |
Environmental Health Perspectives |
3.408 |
538 |
1 |
Metabolic Engineering |
3.397 |
540 |
1 |
Inorganic Chemistry |
3.389 |
544 |
1 |
Organometallics |
3.375 |
546 |
1 |
Bioscience |
3.266 |
584 |
1 |
Biotechnology Advances |
2.875 |
739 |
Total = 155 |
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 10 indicates the number of EPA papers published in the top 10% of journals, based on the JCR Immediacy Index. One-hundred fifty-seven (157) of the 509 papers appear in the top 10% of journals, representing 30.8% of EPA’s P2 papers.
Table 10. P2 Papers in Top 10% of Journals by JCR Immediacy Index
EPA P2 Papers in that Journal |
Journal |
Immediacy Index (II) |
JCR II Rank |
35 |
Tetrahedron Letters |
0.522 |
700 |
21 |
Journal of Organic Chemistry |
0.716 |
425 |
19 |
Chemical Communications |
0.783 |
375 |
16 |
Macromolecules |
0.583 |
594 |
12 |
Journal of the American Chemical Society |
1.212 |
168 |
7 |
Organic Letters |
0.835 |
331 |
5 |
Synlett |
0.607 |
563 |
4 |
Journal of Physical Chemistry B |
0.582 |
595 |
4 |
Journal of Catalysis |
0.514 |
721 |
3 |
Journal of Bacteriology |
0.972 |
245 |
3 |
Current Organic Chemistry |
0.674 |
471 |
3 |
Langmuir |
0.523 |
694 |
2 |
Accounts of Chemical Research |
2.168 |
69 |
2 |
Chemistry–A European Journal |
0.935 |
268 |
2 |
New Journal of Chemistry |
0.670 |
475 |
2 |
Chemistry of Materials |
0.609 |
560 |
2 |
Journal of Chemical Information and Computer Sciences |
0.567 |
612 |
1 |
Nature |
6.679 |
6 |
1 |
Chemical Reviews |
2.955 |
40 |
1 |
Angewandte Chemie-International Edition |
1.655 |
106 |
1 |
Bioscience |
1.205 |
169 |
1 |
Advanced Synthesis & Catalysis |
1.135 |
186 |
1 |
Environmental Health Perspectives |
0.869 |
304 |
1 |
Advances in Polymer Science |
0.857 |
310 |
1 |
Journal of Medicinal Chemistry |
0.817 |
342 |
1 |
Organometallics |
0.716 |
425 |
1 |
Aldrichimica Acta |
0.667 |
478 |
1 |
Annals of Occupational Hygiene |
0.661 |
487 |
1 |
Analytical Chemistry |
0.657 |
493 |
1 |
Inorganic Chemistry |
0.623 |
546 |
1 |
Crystal Growth & Design |
0.532 |
670 |
1 |
European Journal of Organic Chemistry |
0.530 |
677 |
Total = 157 |
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, 12 hot papers, representing 2.4% of the P2 papers, were identified in two fields—Chemistry and Engineering. The hot papers are listed in Table 11.
Table 11. Hot Papers Identified Using ESI Thresholds
Field |
ESI Hot Papers Threshold |
No. of Cites in 2-Month Period |
Paper |
Chemistry |
8 |
11 cites in May-June 2003 |
Huddleston JG, Visser AE, et al. Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation. Green Chemistry 2001;3(4):156-164. |
10 cites in March-April 2001 |
Matyjaszewski K. Transition metal catalysis in controlled radical polymerization: atom transfer radical polymerization. Chemistry–A European Journal 1999;5(11):3095-3102. |
||
10 cites in September-October 2000 |
Li CJ, Chan TH. Organic syntheses using indium-mediated and catalyzed reactions in aqueous media. Tetrahedron 1999;55(37):11149-11176. |
||
10 cites in October-November 2001 |
Patten TE, Matyjaszewski K. Copper(I)-catalyzed atom transfer radical polymerization. Accounts of Chemical Research 1999;32(10):895-903. |
||
9 cites in March-April 2004 |
Wei CM, Li CJ. Enantioselective direct-addition of terminal alkynes to imines catalyzed by copper(I)pybox complex in water and in toluene. Journal of the American Chemical Society 2002;124(20):5638-5639. |
||
9 cites in August-September 2001 |
Hudlicky T, Gonzalez D, et al. Enzymatic dihydroxylation of aromatics in enantioselective synthesis: expanding asymmetric methodology. Aldrichimica Acta 1999;32(2):35-62. |
||
8 cites in July-August 2004 |
Swatloski RP, Holbrey JD, et al. Ionic liquids are not always green: hydrolysis of 1-butyl-3-methylimidazolium hexafluorophosphate. Green Chemistry 2003;5(4):361-363. |
||
8 cites in January-February 2001 |
Varma RS. Solvent-free organic syntheses – using support reagents and microwave irradiation. Green Chemistry 1999;1(1):43-55. |
||
Engineering |
4 |
9 cites in June-July 1996 |
Savage PE, Gopalan S, et al. Reactions at supercritical conditions – applications and fundamentals. AIChE Journal 1995;41(7):1723-1778. |
4 cites in August-September 2004 |
Abraham MH, Zissimos AM, et al. Some novel liquid partitioning systems: water-ionic liquids and aqueous biphasic systems. Industrial & Engineering Chemistry Research 2003;42(3):413-418. |
||
9 cites in May-June 2003 |
Blanchard LA, Brennecke JF. Recovery of organic products from ionic liquids using supercritical carbon dioxide. Industrial & Engineering Chemistry Research 2001;40(1):287-292. |
||
4 cites in July-August 2002 |
Taylor JD, Steinfeld JI, et al. Experimental measurement of the rate of methyl tert-butyl ether hydrolysis in sub- and supercritical water. Industrial & Engineering Chemistry Research 2001;40(1):67-74. |
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 P2 papers. Of the 8,277 total cites, 364 are author self-cites—a 4.4% 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 4.4% self-cite rate for the P2 papers is below the range for author self-citation.
1 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.
2 These papers also met the top 0.01% threshold in ESI.
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.