V. Structure of Haz-Map

Haz-Map is a relational database of hazardous chemicals and occupational diseases. The database currently contains 12,086 chemical and biological agents, 240 diseases, 121 findings (signs & symptoms), 261 jobs, 243 job tasks, 54 industrial processes, 624 industries, and 27 non-occupational activities. The relationships of the tables in the database are shown in Figure 2. When available, standard classification systems were used: Standard Occupational Classification (SOC) system for jobs, the North American Industry Classification System (NAICS) for industries, and the International Classification of Diseases (ICD-9) for diseases.

Diseases  (Toxicity + Exposure)
Chemicals  (Toxicity)

Figure 2: Two levels of information in Haz-Map: diseases and chemicals; The "Toxic Chemicals" table includes biological agents like grain dust and latex rubber.

Notice the bi-directional arrows indicating that users can find all chemicals linked to each disease and all diseases linked to each chemical. Similarly, they can also see all findings of a disease or all diseases with the finding.

Chemical and biological agents in the database are linked to industrial processes and non-occupational activities. Linkage indicates the potential for exposure to the agent. As mentioned earlier, each agent in the database is flagged for adverse effects including asthma, pneumonitis, neuropathy, anemia, hepatotoxicity, and skin sensitization.

Occupational diseases in the database are linked to findings (signs and symptoms of the disease) and hazardous job tasks. Hazardous job tasks increase workers risk for significant exposure and subsequent disease. Linkage between job tasks and jobs or industries indicates an increased likelihood for workers in these jobs or industries to engage in the hazardous job tasks. In this database, chronic occupational diseases are linked to both jobs and industries, while acute diseases and infectious diseases are linked only to jobs. Cancers are not linked to jobs, industries or findings. 

Diseases are also linked to Agents. Linkage between a chemical or biological agent and a disease indicates that sufficient exposure to the agent is associated with increased risk of developing the disease. For chronic diseases, linkage between an agent and a disease means that a causal relationship has been determined based on human case reports or epidemiological studies. Carcinogens are linked only if they have been designated as known human carcinogens by IARC. In some cases, IARC does not list the target organs, but Haz-Map follows the interpretation published in Schottenfeld's Cancer Epidemiology and Prevention, 3rd Ed. [Siemiatycki, p. 326-7]. Acute diseases, for the most part, are also linked to chemicals based on reports of cases in humans.

Diseases are included only if there is sufficiently robust evidence that occupational exposure can cause the diseases, and therefore, that the diseases can be prevented by good occupational hygiene practices. From the point of view of epidemiology and occupational disease surveillance, what are the most common work-related diseases? For each occupational disease, which jobs have the highest risk? Within each job, what are the job tasks or conditions that put the workers at risk?

VI. Updating the Database

Work during the 2007-2015 period was focused on adding chemicals to the database. Haz-Map was updated continuously as new agents were added every day and compared to agents in the database. 2400 chemicals from the HSDB database were added in 2010. Since then, about 5000 chemicals from the SEM database were added. The SEM database contains over 15,000 chemicals/trade names based on records of chemicals used at U.S. federal facilities for nuclear weapons research and development during the Cold War. Many of these chemical are rarely used, and information is scarce. Whenever possible, these chemicals are compared to more well-known chemicals with similar structures. The SEM database also includes many common chemicals of biological origin that were not originally in Haz-Map. It was decided to add rather than ignore these biological agents (monosaccharides, amino acids, proteins, vitamins, etc.) because they demonstrate that all chemicals are toxic at sufficient dose, and their structures can be compared to other chemicals already in the database. Haz-Map does not include drugs unless they cause occupational diseases, e.g., asthma or contact dermatitis. Generally, it does not include alloys or commercial mixtures.

ACGIH publishes every year Documentation of the Threshold Limit Values, Supplement to the 7th Edition, and changes in these documents are added to the database. See this page for the 2014 changes. IARC published several important monographs in 2012 that were added. See the bottom of this page for details. As mentioned earlier, a review of the literature was completed in 2011, and is described on this page. As a result of that review, the categories "More Research Needed" and "Reproduction and Development" were added to the other ten categories of diseases. Textbook references are reviewed when new textbook editions are published. Several literature reviews of occupational medicine journals have been completed (1998-2002, 2005-2008, 2008-2011, 2011-2015). 284 papers were selected and read in 2008, 256 in 2011, and 297 in 2015. For example, in 2008 the following number of journal articles in specific topics were read: Beryllium (12), Respiratory Diseases (24), Solvents (16), Neurodegenerative Diseases (4), Pesticides (4), Benzene (2), Welding (7), Toxicology (3), Cancer (49), Metals (28), Asthma (30), Pulmonary Function Tests (7), Jobs (15), Farming (13), Silica (21), Hypersensitivity Pneumonitis (9), Coal Workers' Pneumoconiosis (4), and Other (36). These reviews resulted in changes to chemical and disease profiles in Haz-Map, often with hyperlinks to the journal articles.

In October of 2014, the author reviewed the ATSDR Web Page "Camp Lejeune, North Carolina" (http://www.atsdr.cdc.gov/sites/lejeune/tce_pce.html). This web page lists reported health effects of five chemicals (trichloroethylene, perchloroethylene, benzene, and vinyl chloride) and has 36 references. The assignment involved reading the papers and finding eight other papers that were used in the report. As a result of that review, "Angiosarcoma of the liver" as a unique form of occupational liver cancer was added to Haz-Map. Previously, vinyl chloride had been linked to "Liver cancer." After the review, "Vinyl chloride" was linked to "Angiosarcoma of the liver," and "Liver cancer" was linked to "Aflatoxins," "Plutonium," and "Viruses (hepatitis B and hepatitis C)."

VII. The Future 

A relational database like Microsoft Access is a powerful tool for studying hazardous chemicals and occupational diseases. See this page, "Using Two Screens and the Tools in Microsoft Access to Compare Rarely Used Chemicals with Well-Known Chemicals." Today, we can separate chemicals into ones that are well understood and ones that are difficult to classify. Metal compounds are in the first category as they share adverse effects: see "Metals and Occupational Diseases." The adverse effects of many organic compounds can be described because they "inherit" the properties of their classes. Search Haz-Map for classes to see the 48 special classes (in All Caps) that are defined in Haz-Map. These 48 defined classes overlap the other classes in the database--the 287 Minor Categories.

Chemicals that don't inherit the properties of particular metal compounds or known classes of chemicals could be prioritized for study. Possible examples in Haz-Map include chemicals classified in "other" categories like "Other Nitrogen Compounds" or "Aromatic Compounds (Nitrogen)." 

Industrial hygiene has improved greatly in the U.S. in the last 70 years. Before 1947, the recommended benzene standard was 100 ppm. Now it is 0.5 ppm. Hazardous substances banned between 1972 and 1991 include: all agricultural uses of DDT (1972); thallium rodenticides (1972); most uses of aldrin & dieldrin (1974); production of benzidine for commercial sale (1974); asbestos in insulation materials (1975); leaded gasoline in new vehicles (1975); most uses of mirex (1977); production of PCBs (1977); sale of lead-based paint to consumers (1978); most uses of BHC, chlordane and heptachlor (1978); all uses of chlordane (1988); and use of mercury in exterior paints (1991).

Further progress in the future will occur as we continue to improve our knowledge of occupational toxicology. The causes of most occupational diseases like lead poisoning and asbestosis are well-established, and we know how to prevent them. There are still some "More Research Needed" diseases and some cancers with insufficient evidence. The causes of these diseases will be disclosed by the combined forces of toxicology and epidemiology. See Toxicology and epidemiology: improving the science with a framework for combining toxicological and epidemiological evidence to establish causal inference and the beautiful diagrams showing how this will be accomplished.

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