Toxicology - In-depth Research Guide
This guide is designed to assist patrons who need to do an in-depth search of the detailed toxicology of a particular substance or make an extensive review of a topic related to toxicology such as endocrine disrupters. If a concise overview of the toxic effects of a particular substance or a brief listing of major toxicological databases is needed, please refer to the sources listed on UB University Libraries overview Toxicology Resources by Subject Guide.
- Major Databases
- Government Sources
- Reference Works
- Societies, Academic & Nonprofits
- Special Focus
- Database Search Details
Major Databases - The starting point
Databases are listed in the recommended order for searching. There can be significant overlap of information between databases. Hence, the researcher must determine the point of diminishing returns where the retrieval of already discovered information overwhelms the amount of new information found in each additional database they searched.
Toxicology can be literally a matter of life and death, so researchers are urged to consult both current and older literature (often not accessible via electronic means) to make certain key information is not missed. A tragic death of a healthy volunteer occurred at John Hopkins University in June 2001 because researchers missed toxicity information published in the 1950's on a particular compound since they searched only the current MEDLINE file that began with 1966 references. [Information Today, 8/7/2001]. Although the databases listed below provide excellent overall coverage, it is essential to use carefully constructed and multiple search strategies to minimize the chances of missing key references. If in doubt, please consult with the toxicology subject specialist librarian or the subject specialist librarian for your department.
The first database that should be searched is TOXLINE , if this has not already been done. This extensive National Library of Medicine database is a wide-ranging composite of citations and abstracts from many other databases including essentially all toxicology-oriented records from MEDLINE . Note that TOXLINE is also listed on our overview Toxicology Resources by Subject Guide .
TOXLINE is searchable by keywords, CAS registry numbers , subject headings including MeSH headings , and authors. Since all the records in this database are related to toxicology, no special strategy is required to limit search results to toxicology. Citations go back as far as 1910, though coverage before 1966 is very selective.
Common compounds will have thousands of hits. It will be important to limit such search results to some specific aspect of toxicology such as chromosome damage or a particular species. Again, if only summary information on common substances is required, the sources on our overview Toxicology Resources by Subject Guide are much more suitable.
Given its broad scope, large size, and ease of use, SciFinder is the database that should be searched next. SciFinder Web provides simultaneous access to the main Chemical Abstracts Service (CAS) literature database of over 38 million references (CAPLUS) since 1900 and the complete National Library of Medicine's MEDLINE database of over 23 million references since 1946. Also included in this system are:
- Substance database of over 156 million registered substances including over 65 million biosequences (REGISTRY),
- Regulatory chemicals database compiled from an extensive group of state, national, and international regulatory lists and inventories. (CHEMLIST)
- CASREACT database: providing access to over 76 million reactions,
See SciFinder Search Details for detailed information on searching toxicological information. SciFinder Web has many more features beyond the scope of this brief guide. Please see the SciFinder Product Description Page for links to additional documentation.
Note that SciFinder requires individual registration with one's UB email address. UB patrons must register for an individual SciFinder user i.d.
3) BIOSIS Previews (Web of Science Platform)
NOTE: This database will be cancelled effective 1/1/2016.
BIOSIS Previews, an enhanced version of Biological Abstracts, is a comprehensive life sciences database covering journal literature, conference papers, U.S. patents, and books. BIOSIS Previews covers the fields of agriculture, biochemistry, bioinformatics, biomedicine, biotechnology, botany, genetics, and much more. Note that UB's subscription to this electronic database goes back only to 1990. If desired, one can simultaneously search MEDLINE and BIOSIS Previews simultaneously in one pass on the Web of Science platform. Note that certain special fields and features of each database are not available when searching the databases together.
Prior to 1990, the print equivalent, Biological Abstracts, can be consulted back to 1927 in the Lockwood Periodcials Collection under call number PER QH301.B37. Note that other electronic databases described in this section, notably SciFinder Web, go back much farther in time and can be consulted for pre-1990 information.
Often simple keyword searching can retrieve many useful toxicological references. However, because of the database size and wide range of topics, searching specific fields for controlled index terms and classification codes is frequently required to create a more complete and, at the same time, focused set of results. Please see BIOSIS Previews Search Details for detailed information on searching toxicological information in this database.
4) AGRICOLA (Agricultural Online Access)
This US National Agricultural Library (NAL) database contains citations and abstracts of journal articles, reports, patents, and other sources of information back to 1970. AGRICOLA contains significant information on the toxicological and environmental aspects of pesticides and other agricultural chemicals, food, animal feed products, and veterinary medicines. Strong coverage of the impact and fate of toxic chemicals in ecological systems and on individual plant and animal species is provided.
Simple keyword searching will usually produce acceptable results, provided some thought is given to what keywords in the title, abstract, and indexing will best describe a particular topic. However, both the NAL Agricultural Thesaurus of Subject Headings and the AGRICOLA Subject Category Codes can be used to enhance both the relevance and scope of the results. .
5) MEDLINE (OVID Interface)
MEDLINE is the US National Library of Medicine's (NLM) premier bibliographic database covering the fields of medicine, nursing, dentistry, veterinary medicine, and the preclinical sciences. MEDLINE contains references and abstracts from more than 4,600 biomedical journals published in the United States and 70 other countries back to 1966. The print equivalent of MEDLINE, called Index Medicus, can be searched back to 1879 in the Health Sciences Library 's Index Collection.
If desired, one can simultaneously search MEDLINE and BIOSIS Previews simultaneously in one pass on the Web of Science platform. Note that certain special fields and features of each database are not available when searching the databases together.
MEDLINE records related to toxicology can readily be searched in either SciFinder or TOXLINE databases described above as well as the publicly available PUBMED interface. However, those who wish to create extensive combinations of search terms (sets) using Boolean logic or take full advantage of the detailed, hierarchical MeSH subject headings should become familiar with with Ovid interface to MEDLINE.
Often simple keyword searching can retrieve many useful toxicological references. However, because of the database size and wide range of topics, searching the MeSH subject heading field is required to create a more complete and, at the same time, focused set of results. Please see MEDLINE Search Details for detailed information on searching toxicological information in this database.
Note: The only way to automatically eliminate duplicate citations from the various databases containing MEDLINE records is to download the search results into a bibliographic citation management software package such as EndNote. The University Libraries provides a UB-wide license to the EndNote product.
Despite the title of this series, these monographs cover far more than carcinogenic risks. Each volume provides an extensive review of the occupational exposure, use, environmental distribution and fate, as well as details of the toxic, carcinogenic, and teratological effects on animals and humans. The series is produced by the authoritative International Agency for Research on Cancer (IARC), part of the World Health Organization .
The University at Buffalo has a standing order for the entire series. Older volumes up through Vol. 35 (1985) are available via Delivery+ from our Library Annex. From Vol. 36 (1985) forward, they are shelved in the Lockwood circulating book collection under the call number RC268.6.I28. Each volume is cataloged separately under its unique title in the Classic Catalog . To review the entire series, simply search by keyword for 'iarc and monographs' or search the call number.
ATSDR is the lead federal public health agency for response to releases of hazardous substances into the environment and participates in policy development for environmental health-related issues. Among the resources they maintain on their web site are Toxicological Profiles for over 285 chemicals, ToxFAQs summaries, and the CERCLA Priority List of Hazardous Substances.
MEDLINEplus from the National Library of Medicine contains extensive topical guides on poisoning, toxicology, and environmental health. Topics include asbestos, biodefense and bioterrorism, anthrax, indoor air pollution, ozone, lead poisoning, and pesticides.
4) RTECS (Registry of Toxic Effects of Chemical Substances)
RTECS, previously a free database from NIOSH, is now only available as a subscription database from a number of vendors including STN International (File RTECS) and Dialog (File 336). It contains toxicological information with citations on over 150,000 chemical substances. A comprehensive record for each substance provides all published toxicology data such as LD50 and LC50 values, international workplace exposure limits, references to US standards and regulations, analytical methods, and exposure and hazard survey data. Note that the toxicology values are taken directly from the published literature with no further evaluation or quality review. Although the UB University Libraries do not maintain a flat-rate, university-wide subscription, the Science and Engineering Information Center staff can provide limited access this database on Dialog or STN International on a pay-as-you-go basis
5) TSCATS (Toxic Substance Control Act Test Submission Database) *Searchable via TOXLINE*
TSCATS is a central system for the collection, maintenance, and dissemination of information on unpublished technical reports submitted by industry to EPA under the Toxic Substances Control Act (TSCA). Studies on over 8,000 chemicals are categorized into three broad subject areas (health effects, environmental effects, and environmental fate). Searches can be conducted using these subject areas plus additional indexing terms from the controlled vocabulary of testing protocol describing observations (e.g., species, duration of study, etc.).
Since most of the documents are unpublished, private company reports, they usually can not be found in the other databases listed in this guide. The database was developed by the Syracuse Research Corporation for the US EPA in 1985.
This guide from the National Institute for Occupational Safety and Health (NIOSH) provides many links to useful NIOSH and external databases on toxicology and chemical hazards in the workplace. Occupational exposure information, personal protective equipment, and material safety data sheet resources are provided.
The mission of the National Institute of Environmental Health Sciences (NIEHS) is to reduce human illness and dysfunction from environmental causes. The NIEHS home page provides links to Environmental Health Topics (A-Z), the peer-reviewed journal Environmental Health Perspectives , and the National Toxicology Program .
8) National Institute for Occupational Safety and Health (NIOSH)
Part of the Centers for Disease Control and Prevention (CDC), NIOSH covers all possible workplace hazards including radiation, toxic substances, noise, and indoor air pollution. Links are provided to an impressive array of databases, publications, criteria documents, software, multimedia, and manuals.
This Centers for Disease Control and Prevention (CDC) topical page informs the general public on environmental health issues, linking to guides for key areas such as pesticides, radiation, and carbon monoxide. Links to materials compiled by the CDC and other U.S. government agencies such as fact sheets, news releases, and recent research reports are provided. The A-Z Index toolbar at the top of the web page is especially useful.
This page also links to the National Center for Environmental Health (NCEH) , part of the CDC. The NCEH home page provides significant additional (and some overlapping) information on diseases and deaths caused by people's interaction with their environment. Topics include air pollution, cancer clusters, chemical weapons, and lead poisoning. The electronic full-text of various reports, brochures, and fact sheets are available for free.
10) ACToR EPA
ACToR is EPA's online repository for all publicly available data relating to chemical toxicity, and allows users to search over 500,000 chemicals by name, structure, or CAS number. ACToR pulls data from over 1000 public sources in order to provide information concerning the risks certain chemicals pose to humans and the environment.
Among these sources available in ACToR are a number of other EPA toxicology databases: ToxRefDB - holding over 30 years of animal toxicity studies; ToxCastDB - providing chemical exposure factor data for chemical prioritization; and DSSTox - containing chemical structure information with annotations.
This network has created a standard format for structure-annotated chemical toxicity data files and makes them openly accessible by scholars and the public.
This site provides information for consumers, health providers, and researchers. The information available is clear and concise. Appropriate contacts with the State of New York are provided for those needing more detailed information.
Located in ia, Missouri, this US Geological Survey (USGS) research facility provides scientific data needed to address national and international environmental contaminant issues, especially effects of habitat alterations on aquatic and terrestrial ecosystems. Included are the National Contaminant Biomonitoring Program Database and the Sediment Effect Concentration Database .
The US Chemical Safety Board (CSB) is an independent federal agency whose mission is to prevent industrial chemical accidents and save lives. The CSB investigates chemical incidents and hazards, determines root causes, and issues safety recommendations to government agencies and private organizations. Details of both current and completed investigations as well as some safety publications are available at this web site.
15) ECOTOX (USEPA)
The ECOTOXicology database (ECOTOX) is a source for locating single chemical toxicity data from three U.S. Environmental Protection Agency (U.S. EPA) ecological effects databases; AQUIRE, TERRETOX, and PHYTOTOX. The AQUIRE and TERRETOX databases contain information on lethal, sublethal and residue effects. The AQUIRE database includes toxic effects data on all aquatic species including plants and animals and freshwater and saltwater species. TERRETOX is the terrestrial animal database. It's primary focus is wildlife species but the database does include information on domestic species. PHYTOTOX is a terrestrial plant database that includes lethal and sublethal toxic effects data.
HERO, a new database introduced by the EPA in 2010, is a new database of scientific studies and other references used to develop EPA's risk assessments aimed at understanding the health and environmental effects of pollutants and chemicals. It is developed and managed in EPA's Office of Research and Development (ORD) by the National Center for Environmental Assessment (NCEA). Although much of the database covers standard peer-reviewed journal articles, HERO also covers reports, books, book chapters, conference material, and other miscellaneous reference types, if they were used in the assessment development process. Some of these references provide links to an internet site where the material can be downloaded or purchased. See HERO Basic Information and Frequent Questions for further help.
HSL = Health Sciences Library, Abbott Hall, South Campus
1) Handbook of toxicology (CRC) [print only]
Call number: HSL Reference QV 607 H236 2002 Toxicology Section
This CRC handbook provides basic information to design, conduct, and interpret toxicology studies and to perform risk assessments. The most recent edition has expanded coverage of inhalation toxicology, neurotoxicology, histopathology, ecotoxicology, and in vitro toxicology. Updated regulatory chapters deal with pesticides, medical devices, consumer products, and world-wide notification of new chemicals. Physiological and biochemical differences between male adults, female adults, and children are discussed. 700 extensively referenced tables are included.
2) Occupational toxicants : critical data evaluation for MAK values and classification of carcinogens [print only]
Call Number: HSL Reference QZ 202 C934 Toxicology Section.
This monograph series presents over 400 detailed toxicological evaluation documents on important occupational toxicants and carcinogens. They describe the toxicological database which determines MAK values (Maximum Concentrations at the Workplace), used in German and European regulations. Published by VCH, twenty-one volumes have been published through 2005.
3) Patty's Industrial Hygiene, 6th Edition (2011)
This large 4-volume work has been a standard reference in occupational health and safety for over 50 years. Well organized chapters cover the recognition of chemical and physical agents, biohazards, engineering controls, personal protection, laws and regulations, management, and special problems. A print copy of this current edition is available at HSL Reference WA 400 P322 2000 Toxicology Section .
4) Patty's Toxicology, 6th Edition (2012)
This large 8-volume work is a companion set to Patty's Industrial Hygiene described above. Extensive and well documented chapters are organized by chemical and physical agents classes such as glycols, various metals, noise, and lasers. A print copy of this edition is available at HSL Reference WA 400 P3222 2000 Toxicology Section .
5) Sittig's handbook of toxic and hazardous chemicals and carcinogens, 6th Edition (2012)
Available through UB's Knovel subscription, this classic title provides information on about 1,400 of the most heavily used, transported and regulated chemical substances of occupational and environmental concern. Included are exposure limits, first aid, storage, handling, spill clean up, and reference information. The appendices contain lists of oxidizing materials, known and suspected carcinogens, and a glossary of terms used in the publication. A print copy of the current edition is available at HSL Reference WA 39 S623h 2002 Toxicology Section .
6) Toxicological evaluations : potential health hazards of existing chemicals [print only]
Call Number: HSL Reference WA 465 T7549 Toxicology Section .
Produced by Berufsgenossenschaft der Chemischen Industrie and published by Springer-Verlag, HSL currently has 15 volumes, the latest in 1999. Toxicological Evaluations are critically assessed data and recommendations for occupational safety officers, industrial hygienists, and human and animal toxicologists. They are compiled under internationally coordinated programs for establishing the risk potential of existing chemicals.
Societies, Academic, and Nonprofit Organizations
1) Society of Toxicology
The premier professional organization in toxicology devotes much of its web site to career and members-only information. However, some information is available to the public including Academic and Post-Doctoral Toxicology Programs and Web Sites.
2) American Academy of Clinical Toxicology
The Academy promotes the study of health effects of poisons on humans and animals by facilitating information exchange among members. It also coordinates research efforts including new therapies and treatment in clinical toxicology. The web site provides links to the important resources like databases and organizations in chemistry, natural toxicants, industrial hygiene, pharmaceuticals and various governmental and non-governmental databases related to toxicology.
3) American Council on Science and Health
The American Council on Science and Health, Inc. (ACSH) is a consumer education consortium concerned with issues related to food, nutrition, chemicals, pharmaceuticals, lifestyle, the environment and health. It attempts to take positions based on "good" science, rather than environmental alarmism. As with any advocacy organization, each researcher will need to evaluate for themselves what bias, if any, exists for each piece of information. However, this site clearly is helpful as a counterbalance to the many prominent environmental advocacy organizations.
4) Chemical Safety and Information Sources
Chapter 11 of the Chemical Information Sources Wikibook, maintained by chemical academic libraries.
5) SETAC: The Society of Environmental Toxicology and Chemistry
The Society of Environmental Toxicology and Chemistry (SETAC) is an independent, nonprofit professional society that promotes research in the field of environmental sciences. Information about the society's mission, meetings, events, membership benefits, and publications can be accessed on the web site The abstracts of the articles are available under the Publications section, though the full-text can be accessed only on subscription.
Over the years, SRC has developed a wealth of environmental, physical, and toxicological data on chemicals. Their Fate Pointers metasearch interface searches chemical structures (~15,000), chemical names (~20,000) and fields indicating if the chemical is in one of 18 different sources including an extensive demo version of their own PHYSPROP database containings structures and physical properties for over 25,000 compounds.
7) TERA Research
Toxicology Excellence for Risk Assessment (TERA) is a nonprofit corporation dedicated to the best use of toxicity data for risk assessment. TERA Research web site outlines the research projects undertaken by the TERA scientists. It also provides links to the full-text of published research papers and a database of international risk assessments drawn from a number of other organizations.
1) EMBASE via Elsevier
A major biomedical and pharmacological database which gives you access to the most up-to-date information about medical and drug-related subjects. It provides comprehensive coverage of drug research, pharmacology, pharmaceutics, pharmacy and toxicology, clinical medicine, public health, occupational health, environmental health rehabilitation and physical therapy, basic biological research relevant to human medicine, alternative medicine; and much more.
2) Pesticide Chemical Search (USEPA)
Performs a search across all conventional, antimicrobial and biopesticide active ingredients registered with the EPA. Included are 20,000+ regulatory documents such as fact sheets, pesticide tolerances in the Code of Federal Regulations, and product labels.
This official web site of the Food and Drug Administration provides a wealth of information of toxicology issues related to food supply and pharmaceuticals.
4) UK Food Standards Agency: Chemicals in food: safety controls
The Food Standards Agency is an independent food safety agency set up by an Act of the British Parliament in 2000 to monitor and protect the public's health and consumer interests in relation to food.
Database Search Details
If MEDLINE information has already been searched via TOXLINE, PubMed, UB's MEDLINE via OVID, or MEDLINE via Web of Science, then the MEDLINE portion of SciFinder can be turned off by clicking on the Preferences Button, then the Databases Tab, and then deselecting MEDLINE. This must be done before starting the search. However, SciFinder's powerful natural language query system may retrieve MEDLINE records missed by the other MEDLINE search interfaces.
Two basic approaches, compound or subject, can be used to find toxicological information in SciFinder Web.
a) Starting with a specific compound
If the user has a particular substance of interest, click on the Locate button, then on the Locate Substances: Substance Identifier button. Enter a CAS registry number or chemical name. A brief record with the chemical structure will display. Click on the Get References button at the bottom of the page. Activate the References Associated With radio button; then check the Adverse Effect, including Toxicology box. Click the OK button to retrieve the references.
All the Chemical Abstracts records are displayed first, then all the MEDLINE records, each group in reverse chronological order. Clicking on the Microscope icon for any record will display the full record including abstract and indexing. Clicking on the Full-text icon (looks like a page of paper) will lead to the full-text of the item.
If another version of MEDLINE has already been searched, MEDLINE citations can be eliminated from retrieved sets by clicking on the Analyze/Refine button, then the Refine button, the Database button, and then checking only the CAPLUS box. MEDLINE records duplicated by CAPlus records can be removed by clicking on the Remove Duplicates button.
It is also possible to retrieve substance records by molecular formula, exact structure, or substructure searching using the Explore option. The process for retrieving the toxicology literature references remains the same regardless of how the substance record(s) are retrieved.
Note that SciFinder Web has an extensive database of regulatory information based on various state, US, and international lists created by various agencies. This information can be accessed by retrieving any substance record and clicking on the small gray icon that looks like a building with 3 columns. See the Regulated Chemicals (CHEMLIST) Database Information Page for further details.
b) Subject/Topic search
From the main search screen, click on the Explore button, and then the Research Topic button. It is important to phrase the search query naturally using prepositions to separate search concepts. For example, the query 'mutations in salmonella by ultraviolet light' would retrieve a group of very relevant citations on that topic. Simply putting in a list of individual words with spaces in between (as in Google) should NOT be done. The system first presents a candidate list of hit sets based on various combinations of the concepts in the query. Choose whatever hit sets are desired based on the description of each and click on the Get References button.
If the results are unsatisfactory or too small, use the Back button and rephrase the query. If there are a large number of hits, one can rephrase the query or limit the retrieval set by use of the Analyze/Refine button. Refine options include date, document type, language, and availability of full-text. Another option under Refine is Research Topic which permits limiting the query using additional keyword(s). Analyze/Refine options can be used reiteratively as many times as needed to narrow the search results. When doing keyword searches, keep in mind that SciFinder Web covers all aspects of chemistry and chemistry-related topics, not just toxicology.
Chemical Abstracts Service provides a set of excellent downloadable, interactive tutorials for those needing additional help in using the system.
In BIOSIS Previews, a simple keyword search will search all fields containing text including title, abstract, indexing and concept & taxonomic names. The BIOSIS Previews Quick Reference Card outlines search syntax and describes how to search various fields. An in-depth description of the Web of Science search interface is beyond the scope of this guide. Web of Science Quick Reference Guide provides a brief introduction to the search platform.
Searching specific index/code fields can greatly enhance the retrieval or limit a large results list to a much more focused set. Individual fields can be searched by clicking on the drop down menu boxes to the right of the search term boxes on the main search query screen. Search examples below the query term text boxes change to show sample format(s) for the chosen field. For many of the search fields, a magnifying glass icon appears to the right that allows one to browse the field in an alphabetical or hierarchical fashion. A brief review of some of the key index fields follows.
Concept Codes: This field contains five-digit codes representing broad biological concepts mentioned in the document. Codes can be searched at the broader three-digit or the narrower five-digit level. The table below lists key codes for toxicology-related fields.
- Toxicology - 225
- Air, Water, and Soil Pollution - 37015
- Ecology - 075
- Neoplasms and Neoplastic Agents - 240
- Occupational Health - 37013
- Pharmacology - 220
Chemical & Biochemical : This search option searches the chemical and biochemical indexing including chemical names and Chemical Abstracts Service Registry Numbers, which are assigned to chemicals mentioned in the article. The Registry Number defines a unique substance independent of nomenclature. Two hyphens appear in every Registry Number, which separate the number into three parts.
Taxonomic Data: This search option searches taxonomic names & notes, super taxa, organism classifiers & names, and variants.
In MEDLINE, a simple keyword search using the text entry box under Enter Keyword or phrase will search all fields containing text including title, abstract, and subject headings. Be sure to retain the default checkmark in the box Map Term to Subject Heading on the main search page and then click on the Perform Search button. A pick list of subject headings related to the query keyword will be presented. The user can pick as many items as desired to be searched in the database. Clicking on underlined subject headings will display the hierarchical context of that particular term within the overall MeSH thesaurus.
Note the three columns after each term on the pick list. Checking the Explode option will retrieve that subject heading plus all narrower terms as defined by the MeSH thesaurus. Checking the Focus option will retrieve only those records where that particular subject heading is identified as a major concept in the article. The third column, Scope , having icons with the letter I inside a circle provides helpful scope notes about the term. Note the very last item on the pick list will be a simple keyword search in all text fields.
An in-depth description of the Ovid search interface is beyond the scope of this guide. See Ovid's Tutorials & Short Demos to learn more about search syntax and interface features. More extensive information can be reviewed by clicking on the blue Help button in the upper right hand corner of most Ovid web pages.
Searching certain index/subject heading fields can greatly enhance the retrieval and/or limit a large results list to a much more focused set. Individual fields can be searched by clicking on the Search Fields icon at the top of the Ovid search page. A detailed discussion of each search field is provided in Ovid's MEDLINE Database Guide. A brief review of key index fields follows.
Floating Subheadings: The Floating Subheadings ( FS ) field contains standard 2-letter codes used to subdivide MeSH subject headings. Useful subheading codes for toxicology-related areas include TO for toxicity , AE for adverse effects, PO for poisoning, DE for drug effects, ME for metabolism, and PK for pharmacokinetics. To link (relate) a subheading to a particular term or substance, one should search the full MeSH subject heading, if known, in the Subject Heading field ( SH ). If the desired MeSH subject heading is not known, follow the keyword search procedure described in the first two paragraphs of this section.
MeSH Subject Headings: In general, these can be most conveniently searched simply by entering likely keywords in the general keyword search box while making sure to retain the default checkmark in the box Map Term to Subject Heading. This is described in the first two paragraphs of this section. However, if MeSH subject headings are already known, they can be searched directly in the SH field.