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Bibliometric Analysis of Papers on Topics Related to Safe Pesticides/Safe Products
November 15, 2006

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 safe pesticides/safe products (SP/SP). For this analysis, 261 papers published from 1998 to 2005 were reviewed. These publications were cited 2,491 times in the journals covered by Thomson’s Web of Science.1 Of these 261 publications, 216 (83%) have been cited at least once in a journal.

Searches of Thomson’s Web of Science and Scopus2 were conducted to obtain times cited data for the safe pesticides/safe products journal publications. 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. For influence and impact measures, ESI employs both total citation counts by field and cites per paper scores. The former reveals gross influence while the latter shows weighted influence, also called impact. JCR is a recognized authority for evaluating journals. It 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. The two key measures used in this analysis to assess the journals in which the EPA safe pesticides/safe products papers are published are the Immediacy Index and the Impact Factor. The Immediacy Index is a measure of how quickly the “average article” in a journal is cited. This index indicates how often articles published in a journal are cited within the same year and it is useful in comparing how quickly journals are cited. The Impact Factor 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 other journals in the same field.

SUMMARY OF RESULTS
  1. Nearly one-quarter of the safe pesticides/safe products publications are highly cited papers. A review of the citations indicates that 58 (22.2%) of the safe pesticides/safe products papers qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications. This is more than 2 times the number expected. Six (2.3%) of the safe pesticides/safe products papers qualify as highly cited when using the criteria for the top 1%, which is more than 2 times the number expected. None of the papers meet the ESI threshold for very highly cited (in the top 0.1%) or the highest ESI threshold (in the top 0.01%), which is consistent with the expected number of papers for these two categories (i.e., 0.26 and 0.026, respectively).
  2. The safe pesticides/safe products papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, in 12 of the 16 fields in which the EPA safe pesticides/safe products papers are published, the ratio of actual to expected cites is greater than 1, indicating that the safe pesticides/safe products papers are more highly cited than the average papers in those fields. For all 16 fields combined, the ratio of total number of cites to the total number of expected cites (2491 to 1813.07) is 1.37, indicating that the safe pesticides/safe products papers are more highly cited than the average paper.
  3. More than one-third of the safe pesticides/safe products papers are published in very high impact journals. Ninety-two (92) of the 261 papers were published in the top 10% of journals ranked by JCR Impact Factor, representing 35% of EPAs safe pesticides/safe products papers. This number is 3.5 times higher than expected. Sixty-five (65) of the 261 papers appear in the top 10% of journals ranked by JCR Immediacy Factor, representing 25% of EPAs safe pesticides/ safe products papers. This number is 2.5 times higher than expected.
  4. Three of the safe pesticides/safe products papers qualify as hot papers. Using the hot paper thresholds established by ESI as a benchmark, 3 hot papers, representing 1.2% of the safe pesticides/safe products papers, were identified in the analysis. Hot papers are papers that are highly cited shortly after they are published. The number of safe pesticides/safe products hot papers is 12 times higher than expected.
  5. The authors of the safe pesticides/safe products papers cite themselves much less than the average author. One-hundred fifty-eight (158) of the 2,491 cites are author self-cites. This 6.3% author self-citation rate is well below the accepted range of 10-30% author self-citation rate.
  6. Seven of the authors of the safe pesticides/safe products papers are included in ISIHighlyCited.com, which is a database of the worlds most influential researchers who have made key contributions to science and technology during the period from 1981 to 1999.

Highly Cited Safe Pesticides/Safe Products Publications

The 261 safe pesticides/safe products papers reviewed for this analysis covered 16 of the 22 ESI fields. The distribution of the papers among these 16 fields and the number of citations by field are presented in Table 1.

Table 1. Safe Pesticides/Safe Products Papers by ESI Fields

No. of Citations

ESI Field

No. of EPA SP/SP Papers

Average Cites/Paper

977

Environment/Ecology

98

9.97

565

Pharmacology & Toxicology

74

7.64

170

Biology & Biochemistry

10

17.00

168

Microbiology

7

24.00

136

Molecular Biology & Genetics

16

8.50

114

Computer Science

6

19.00

97

Neuroscience & Behavior

8

12.12

76

Plant & Animal Science

9

8.44

58

Engineering

10

5.80

51

Chemistry

10

5.10

28

Economics & Business

1

28.00

17

Immunology

1

17.00

15

Agricultural Sciences

4

3.75

11

Multidisciplinary

2

5.50

4

Clinical Medicine

2

2.00

4

Physics

3

1.33

Total = 2,491

 

Total = 261

9.54

There are 58 (22.2% of the papers analyzed) highly cited EPA safe pesticides/safe products papers in 12 of the 16 fields—Environment/Ecology, Pharmacology & Toxicology, Microbiology, Computer Science, Biology & Biochemistry, Plant & Animal Science, Engineering, Neuroscience & Behavior, Economics & Business, Chemistry, Multidisciplinary, and Agricultural Sciences—when using the ESI criteria for the top 10% of papers. Table 2 shows the number of EPA papers in those 12 fields that meet the top 10% threshold in ESI. Six (2.3%) of the papers analyzed qualify as highly cited when using the ESI criteria for the top 1% of papers. These papers cover two fields—Environment/ Ecology and Computer Science. Table 3 shows the 6 papers by field that meet the top 1% threshold in ESI, and the citations for these papers are provided in Tables 4 and 5. There were no papers that meet the top 0.1% threshold or the top 0.01% threshold in ESI.

Table 2. Number of Highly Cited Safe Pesticides/Safe Products Papers by Field (top 10%)

Citations

ESI Field

No. of Papers

Average Cites/Paper

% of EPA Papers in Field

570

Environment/Ecology

27

21.11

27.55%

139

Pharmacology & Toxicology

9

15.44

12.16%

111

Microbiology

2

55.50

28.57%

109

Computer Science

4

27.25

66.67%

76

Biology & Biochemistry

1

76.00

10.00%

74

Plant & Animal Science

5

14.80

55.56%

68

Engineering

4

17.00

40.00%

67

Neuroscience & Behavior

2

33.50

25.00%

28

Economics & Business

1

28.00

100.00%

24

Chemistry

1

24.00

10.00%

11

Multidisciplinary

1

11.00

50.00%

1

Agricultural Sciences

1

1.00

25.00%

Total = 1,278

 

Total = 58

22.03

22.22%

Table 3. Number of Highly Cited Safe Pesticides/Safe Products Papers by Field (top 1%)

Citations

ESI Field

No. of Papers

Average Cites/Paper

% of EPA Papers in Field

126

Environment/Ecology

5

25.20

5.10%

85

Computer Science

1

85.00

16.67%

Total = 211

 

Total = 6

35.17

2.30%

Table 4. Highly Cited Safe Pesticides/Safe Products Papers in the Field of Environment/Ecology (top 1%)

No. of Cites

First Author

Paper

70

Ankley GT

Description and evaluation of a short-term reproduction test with the fathead minnow (Pimephales promelas). Environmental Toxicology and Chemistry 2001;20(6):1276-1290.

32

Alavanja MCR

Use of agricultural pesticides and prostate cancer risk in the agricultural health study cohort. American Journal of Epidemiology 2003;157(9):800-814.

15

Tabb MM

Highly chlorinated PCBs inhibit the human xenobiotic response mediated by the steroid and xenobiotic receptor (SXR). Environmental Health Perspectives 2004;112(2):163-169.

5

Shafer TJ

Developmental neurotoxicity of pyrethroid insecticides: critical review and future research needs. Environmental Health Perspectives 2005;113(2):123-136.

4

Tietge JE

Metamorphic inhibition of Xenopus laevis by sodium perchlorate: effects on development and thyroid histology. Environmental Toxicology and Chemistry 2005;24(4):926-933.

Table 5. Highly Cited Safe Pesticides/Safe Products Paper in the Field of Computer Science (top 1%)

No. of Cites

First Author

Paper

85

Tong W

Evaluation of quantitative structure-activity relationship methods for large-scale prediction of chemicals binding to the estrogen receptor. Journal of Chemical Information and Computer Sciences 1998;38(4):669-677.

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 12 of the 16 fields in which the EPA safe pesticides/safe products papers were published, the ratio of actual to expected cites is greater than 1, indicating that the safe pesticides/safe products papers are more highly cited than the average papers in those fields (see Table 6).

Table 6. Ratio of Average Cites to Expected Cites for Safe Pesticides/Safe Products Papers by Field

ESI Field

Total Cites

Expected Cite Rate

Ratio

Agricultural Sciences

15

13.74

1.09

Biology & Biochemistry

170

137.21

1.24

Chemistry

51

43.48

1.17

Clinical Medicine

4

5.94

0.67

Computer Science

114

12.54

9.09

Economics & Business

28

4.4

6.36

Engineering

58

15.45

3.75

Environment/Ecology

977

523.95

1.86

Immunology

17

19.25

0.88

Microbiology

168

93.17

1.80

Molecular Biology & Genetics

136

313.83

0.43

Multidisciplinary

11

4.25

2.59

Neuroscience & Behavior

97

66.84

1.45

Pharmacology & Toxicology

565

503.19

1.12

Physics

4

15.19

0.26

Plant & Animal Science

76

40.64

1.87

JCR Benchmarks

Impact Factor. The JCR 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 7 indicates the number of safe pesticides/safe products papers published in the top 10% of journals, based on the JCR Impact Factor. Ninety-two (92) of 261 papers are published in the top 10% of journals, representing 35% of EPA’s safe pesticides/safe products papers. This indicates that more than one-third of the safe pesticides/safe products papers are published in the highest quality journals as determined by the JCR impact factor, which is 3.5 times the expected percentage.

Table 7. Safe Pesticides/Safe Products Papers in Top 10% of Journals by JCR Impact Factor

EPA SP/SP Papers in that Journal

Journal

Impact Factor
(IF)

JCR IF Rank

24

Toxicological Sciences

3.391

591

14

Environmental Health Perspectives

3.929

439

10

Environmental Science & Technology

3.557

540

5

Journal of Chemical Information and Computer Sciences

2.810

846

3

Applied and Environmental Microbiology

3.810

470

2

American Journal of Epidemiology

4.933

290

2

Molecular Ecology

4.375

351

2

Mutation Research-Reviews in Mutation Research

3.667

506

2

Journal of Chromatography A

3.359

602

2

Ecological Applications

3.287

623

2

Chemical Research in Toxicology

2.797

854

1

Science

31.853

10

1

JAMA-Journal of the American Medical Association

24.831

15

1

Proceedings of the National Academy of Sciences of the United States of America

10.452

88

1

Molecular & Cellular Proteomics

9.624

100

1

Progress in Nuclear Magnetic Resonance Spectroscopy

6.885

175

1

Human Mutation

6.845

176

1

Journal of Immunology

6.486

187

1

Molecular Biology and Evolution

6.355

193

1

Bioinformatics

5.742

224

1

Analytical Chemistry

5.450

243

1

Endocrinology

5.151

274

1

Cancer Epidemiology Biomarkers & Prevention

4.500

331

1

Global Change Biology

4.333

358

1

Ecology

4.104

394

1

Physiological Genomics

3.855

455

1

Drug Metabolism and Disposition

3.836

461

1

Mutation Research-Fundamental and Molecular Mechanisms of Mutagenesis

3.730

486

1

Conservation Biology

3.672

504

1

Biochimica et Biophysica Acta-Bioenergetics

3.503

556

1

New Phytologist

3.355

603

1

Journal of Applied Ecology

3.266

629

1

Journal of Molecular Graphics & Modelling

3.036

732

1

Lung Cancer-J IASLC

2.914

789

1

Rapid Communications in Mass Spectrometry

2.750

866

Total = 92

Immediacy Index. The JCR 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 8 indicates the number of safe pesticides/safe products papers published in the top 10% of journals, based on the JCR Immediacy Index. Sixty-five (65) of the 261 papers appear in the top 10% of journals, representing 25% of the safe pesticides/safe products papers. This indicates that one-quarter of the safe pesticides/safe products papers are published in the highest quality journals as determined by the JCR immediacy index, which is 2.5 times higher than the expected percentage.

Table 8. Safe Pesticides/Safe Products Papers in Top 10% of Journals by JCR Immediacy Index

EPA SP/SP Papers in that Journal

Journal

Immediacy Index
(II)

JCR II Rank

14

Environmental Health Perspectives

1.202

202

10

Environmental Science & Technology

0.623

617

5

Journal of Chemical Information and Computer Sciences

0.700

513

2

Ecotoxicology

1.450

151

2

Mutation Research-Reviews in Mutation Research

1.125

224

2

American Journal of Epidemiology

0.842

373

2

Ecological Applications

0.747

466

2

Birth Defects Research Part B-Developmental and Reproductive Toxicology

0.677

539

2

Molecular Ecology

0.674

545

2

Chemical Research in Toxicology

0.535

782

2

Journal of Chromatography A

0.510

835

1

Science

7.379

3

1

JAMA-Journal of the American Medical Association

5.499

9

1

Molecular & Cellular Proteomics

2.021

79

1

Proceedings of the National Academy of Sciences of the United States of America

1.923

89

1

Molecular Biology and Evolution

1.489

146

1

Human Mutation

1.331

173

1

Endocrinology

1.122

227

1

Journal of Immunology

1.096

233

1

Analytical Chemistry

0.885

346

1

New Phytologist

0.876

349

1

Conservation Biology

0.744

468

1

Journal of Experimental Biology

0.741

471

1

Integrative and Comparative Biology

0.727

485

1

Journal of Applied Ecology

0.718

493

1

Bioinformatics

0.715

498

1

Physiological Genomics

0.714

499

1

Progress in Nuclear Magnetic Resonance Spectroscopy

0.667

551

1

Biochimica et Biophysica Acta-Bioenergetics

0.613

635

1

Ecology

0.590

676

1

Drug Metabolism and Disposition

0.590

676

Total = 65

 

 

 

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 2006), but there were a number of hot papers identified from previous periods.

Using the hot paper thresholds established by ESI as a benchmark, 3 hot papers, representing 1.2% of the safe pesticides/safe products papers, were identified in two fields—Environment/Ecology and Engineering. The hot papers are listed in Table 9.

Table 9. Hot Papers Identified Using ESI Thresholds

Field

ESI Hot Papers Threshold

No. of Cites in 2-Month Period

Paper

Environment/ Ecology

4

5 cites in April-May 2004

Schumaker NH, et al. Projecting wildlife responses to alternative future landscapes in Oregon’s Willamette Basin. Ecological Applications 2004;14(2):381-400.

 

4

4 cites in April 2004

Baker JP, et al. Alternative futures for the Willamette River Basin, Oregon. Ecological Applications 2004;14(2):313-324.

Engineering

3

3 cites in November-December 2000

Garrison AW, et al. Phytodegradation of p,p'-DDT and the enantiomers of o,p'-DDT. Environmental Science & Technology 2000;34(9):1663-1670.

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 safe pesticides/safe products papers. Of the 2,491 total cites, 158 are author self-cites—a 6.3% 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. Kovacic and Misak5 recently reported a 20% author self-citation rate for medical literature. Therefore, the 6.3% self-cite rate for the safe pesticides/safe products papers is well below the range for author self-citation.

Highly Cited Researchers

A search of Thomson’s ISIHighlyCited.com revealed that 7 (1.1%) of the 653 authors of the safe pesticides/safe products papers are among the world’s most highly cited researchers. ISIHighlyCited.com is a database of the world’s most influential researchers who have made key contributions to science and technology during the period from 1981 to 1999. The highly cited researchers identified during this analysis of the safe pesticides/safe products publications are presented in Table 10.

Table 10. Highly Cited Researchers Authoring Safe Pesticides/Safe Products Publications

Highly Cited Researcher

Affiliation

ESI Field

Ankley, Gerald T

U.S. EPA

Environment/Ecology

Bollag, Jean-Marc

Pennsylvania State University

Environment/Ecology

Fuchs, Elaine

Rockefeller University

Molecular Biology & Genetics

Ho, Chi-Tang

State University of New Jersey

Agricultural Sciences

Rubin, Gerald M

Howard Hughes Medical Center

Molecular Biology & Genetics

Sumpter, John F

Brunel University

Environment/Ecology

Yang, Chung S

State University of New Jersey

Pharmacology

Total = 7

   

1Thomson’s Web of Science provides access to current and retrospective multidisciplinary information from approximately 8,700 prestigious research journals from around the world. Web of Science also provides cited reference searching and navigates users to electronic full-text journal articles.

2 Scopus is a large abstract and citation database of research literature and quality Web sources designed to support the literature research process. Scopus offers access to 15,000 titles from 4,000 different publishers, more than 12,850 academic journals (including coverage of 535 open access journals, 750 conference proceedings, and 600 trade publications), 27 million abstracts, 245 million references, 200 million scientific Web pages, and 13 million patent records.

3Garfield E, Sher IH. New factors in the evaluation of scientific literature through citation indexing. American Documentation 1963;18(July):195-210.

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.

5 Kavaci N, Misak A. Author self-citation in medical literature. Canadian Medical Association Journal 2004;170(13):1929-1930.

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