Figure 2: Two levels of information in Haz-Map: diseases and chemicals.
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.
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.
The only exceptions to the rule that linkage indicates human disease known to be caused by the agent are the following diseases: Solvents, acute toxic effect (linked to all organic solvents); Encephalopathy, chronic solvent (linked to all organic solvents used in paints or varnishes); Encephalopathy, acute toxic effect (linked to other potential causes of acute encephalopathy excluding solvents, asphyxiants, fumigants, and insecticides); and Pneumonitis, toxic (caused by chemicals corrosive to the skin, eyes, and respiratory tract). The occupational disease "pneumonitis, toxic" is defined as noncardiogenic pulmonary edema induced by acute exposure to metal fumes or toxic gases and vapors after a spill or confined space accident. The "major irritant inhalants" are ammonia, bromine, chlorine, chlorine dioxide, diborane, ethylene oxide, formaldehyde, hydrogen chloride, hydrogen fluoride, methyl isocyanate, nitrogen dioxide, ozone, phosgene, and sulfur dioxide. [LaDou, p. 523] While human cases have been documented for the major irritant inhalants, there are many chemicals with similar properties that can cause acute lung injury. Haz-Map flags 837 chemicals that have the potential to cause toxic pneumonitis as an adverse effect in heavily exposed workers or in animal experiments. Of these 837 chemicals, 192 with the designation of "toxic inhalation hazard" by ERG 2012 are linked to the occupational disease "Pneumonitis, toxic."
V. Limitations of Haz-Map
Epidemiology is the study of the patterns of diseases in populations. It relies on scientific observational studies that reveal associations between diseases and risk factors. Industrial hygiene focuses on chemicals and their potential to cause adverse effects in exposed humans. It is important to keep in mind the two levels of information in the database. Haz-Map was not designed to list every possible disease for each job. For example, logging workers running chain saws are exposed to carbon monoxide, and there is the potential for adverse effects. However, the job task "Operate internal combustion engine with inadequate ventilation" is not linked to logging workers because they work outdoors. In other words, a disease is linked to a job only if one of the high-risk job tasks of that disease is likely to be performed by workers doing that job.
It is also important to remember that Haz-Map is a map. A highway map of the U.S. is useful if it accurately shows the main roads between major cities. It would be less useful if there were too much detail, showing every small town, lake, and dirt road. The goal is not to list every disease that could possibly be work-related, but to focus on established occupational diseases and their causes. 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?
Revised: March 14, 2013
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