TOXNET: The NLM Toxicology Databases

As part of living in the modern world, we are regularly exposed to chemicals. How do we discover more about these chemicals? How can researchers better understand the impact of chemicals on the environment or the interactions of chemicals with the human body? How can industry ensure it’s managing exposure to hazardous substances? How can consumers make informed decisions about what chemicals we bring into our homes or take into our bodies? To help bridge that knowledge gap, the National Library of Medicine developed TOXNET, the Toxicology Data Network.

What is TOXNET and when was it started?

The Toxicology Data Network (TOXNET) was created in 1985 to provide more effective access to the online group of databases developed and managed by the Toxicology and Environmental Health Information Program (TEHIP) in the Division of Specialized Information Services (SIS) of the National Library of Medicine (NLM). Toxicology databases became part of NLM’s online biomedical resources after the 1967 mandate from Congress to establish a computer-based toxicology information program at NLM. TOXNET is among the world’s largest collection of toxicology databases, with all of its databases available online at no cost.

Screenshot of the TOXNET Home Page

Today’s TOXNET provides an easy-to-use interface.

Is TOXNET widely used?

In its early days, TOXNET was popular mostly with scientists and researchers looking for reliable toxicology information. Those groups still use it, but now many users are non-scientists, often homeowners and parents looking for reliable information about the chemicals they encounter in daily life.

“TOXNET databases are accessed 24/7 by many types of users around the world, from scientists to health professionals to members of the general public,” notes Dr. Pertti (Bert) Hakkinen, the acting head of NLM’s Office of Clinical Toxicology, which oversees some of the databases. And those groups use it quite extensively.

“We don’t count users, we count queries,” explains Phillip Lee Thomas of SIS. “A single user might make several queries and then read none, some, or all of the suggested records.”

TOXNET totaled over 3.5 million queries from January through August 2015, a huge increase from the early days. TOXNET averaged between 1,000 and 2,000 queries per month in 1997; that figure is now up to 437,500. SIS Branch Chief Jeanne Goshorn attributes this growth to several factors: free access; the growth of the Internet, which draws users from around the globe; and a redesign of the TOXNET system to provide easier navigation in searching and viewing results.

What was the first database in TOXNET?

The first database added to the network in 1985 was the Hazardous Substances Data Bank (HSDB). Today that database contains almost 6,000 records on chemicals and other substances, with a focus on toxicology information related to human exposure, industrial hygiene, emergency handling procedures, environmental fate, and regulatory requirements.

What is the most recent database added to TOXNET?

The Comparative Toxicogenomics Database (CTD) is the most recent addition, becoming a part of TOXNET in 2011. Useful to medical researchers, scientists, chemists, and others, the CTD describes the relationships between chemicals, genes, and the environment. The site promotes understanding of the effects of environmental chemicals on human health by integrating data from curated scientific literature to describe chemical interactions with genes and proteins and to elucidate associations between diseases and chemicals, and between diseases and genes/proteins. Continually under development and updated several times a year, this resource’s most recent enhancement is a new data set on the exposures associated with specific chemicals.

What are the most popular TOXNET sites?

Here are snapshots of some of the more popular TOXNET sites:

    • The Hazardous Substances Data Bank (HSDB) is the world’s largest database of its kind and a trusted source for toxicologists and emergency responders. Much of HSDB’s information is also available on NLM Wireless Information System for Emergency Responders (WISER), which is offered online and as an app for smartphones and tablets as part of the “what you need, how and when you need it, and where you need it” content for emergency responders who encounter hazardous substances. A scientific peer review panel reviews the information gathered in this resource.
    • The Household Products Database identifies the chemicals used in over 15,000 consumer products available in the US as listed on Safety Data Sheets, product labels, and manufacturers’ Web sites. It provides information on potential health effects associated with chemicals used in these products as noted by the manufacturer, along with first aid measures and other useful content. In addition, because many of the TOXNET databases are linked by CAS Registry numbers, which provide unique identifiers for chemical substances, it is easy for users to move from one of the other TOXNET databases to a more comprehensive one such as HSDB to find more information on the possible effects of chemicals.
    • TOXLINE offers 4 million citations to articles from scientific journals and other authoritative sources about the biochemical, pharmacological, physiological, and toxicological effects of drugs and other chemicals. Some of the information in this database is archival, providing a rich resource for historical explorations of toxicology.
    • The chemical structure for Buckminsterfullerene in 2D and 3D

      ChemIDplus delivers over 400,000 chemical names, synonyms and structures.

    • ChemIDplus offers an online dictionary of chemical substances cited in NLM databases and other Internet resources. It lists over 400,000 chemicals with their common names, synonyms, and structures. It also links out to many resources that include additional information on the chemical in question.
    • LactMed the Drugs and Lactation Database, is for breastfeeding mothers and others seeking information about the safety of drugs, dietary supplements, and other chemicals, including the effects of those agents on nursing infants.

    Is there a listing of all the databanks in the TOXNET database?

    For a complete list of all 16 databanks/databases within TOXNET, see the TOXNET homepage or the Environmental Health & Toxicology portal at SIS.

    How is the content of a database reviewed for accuracy?

    For some databases, experts in the relevant fields rigorously review the scientific content. For example, the HSDB expert panel starts by examining all data from a core set of books, government documents, technical reports, selected primary journal literature, and other online sources of information, with a goal of linking the content to as much publicly available information as possible. The expert review panel then meets to discuss the content of the records and provide additional input. Other TOXNET databases come from authoritative sources, such as collections of peer-reviewed journals or other government agencies.

    How do you decide when to archive a database?

    A database is archived when the funding agency or organization working with NLM decides not to financially support its update and enhancement. However, this does not mean that the particular database is no longer available. Archived databases, though not updated, remain available on TOXNET. Fact sheets about the databases describe their history and scope of coverage.

    What’s new in TOXNET? Future plans?

    Within the HSDB, we’ve added chemical structures; new subfields, such as age groups for human data; more occupational exposure standards; and information on numerous nanomaterials. The Comparative Toxicogenomics Database added its new module on exposures to specific chemicals in 2015.

    Going forward, we plan to expand the breadth and depth of TOXNET and its resources, to provide direct links to even more useful information, and to increase accessibility to users coming in on various devices.

    Specifically, the HSDB site will provide more exposure-related information, such as the uses of a chemical or substance in consumer products; summaries for consumers and others wanting to learn about a chemical or substance; and more visual content, such as images of animals and plants associated with a substance and diagrams of a substance’s metabolic pathway.

    By Tom Conuel, with assistance from SIS’s Jeanne Goshorn, Dr. Bert Hakkinen and George Fonger

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