Evaluation of the Patient with Occupational Chemical Exposure
This chapter highlights common toxicologic problems in the workplace. Occupationally related disease is seen commonly in the outpatient setting. Estimates of the proportion of occupationally related medical problems in primary care practices range up to 15–20%, although this includes many patients with musculoskeletal complaints. However, approximately 5% of all symptomatic poison control center consultations are occupational in nature, suggesting a large number of chemical exposures. Specialists in emergency medicine are the largest single referring group for these calls.
General considerations
Occupational illness is rarely pathognomonic. The connection between illness and workplace factors is typically obscure unless a specific effort is made to link exposure to disease.
Massive or catastrophic events leading to the acute onset of symptoms, such as release of an irritant gas, are relatively uncommon.
For most workplace exposures, symptom onset is more often insidious, following a subacute or chronic pattern, as in heavy metal (eg, lead) poisoning.
Long latency, often years, between exposure and disease makes linking cause and effect even more difficult—for example, in chronic lung disease or occupationally related cancer.
Occupational evaluation frequently includes legal and administrative components.
Occupational illness, even if suspected but not established, may be a reportable illness in certain states (eg, in California through the Doctor’s First Report system).
Establishing quantifiable documentation of adverse effects at the time of exposure may be critical to future attribution of impairment (eg, spirometric evaluation soon after an irritant inhalant exposure).
Although workers’ compensation is in theory a straightforward “no-fault” insurance system, in practice it is often arcane and adversarial. It is important to remember that the person being treated is the patient, not the employer or a referring attorney.
Components of the occupational exposure history
Job and job process
Ask specifics about the job. Do not rely on descriptions limited to a general occupation or trade, such as “machinist,” “painter,” “electronics worker,” or “farmer.”
Describe the industrial process and equipment used on the job. If power equipment is used, ascertain how it is powered to assess carbon monoxide exposure risk.
Determine whether the work process uses a closed (eg, a sealed reaction vat) system or an open system and what other processes or workstations are nearby. Work under a laboratory hood may be an effectively “closed” system, but not if the window is raised too far or if the airflow is not calibrated.
Find out who does maintenance and how often it is done.
Level of exposure
Ask whether dust, fumes, or mist can be seen in the air at the work site. If so, question whether co-workers or nearby objects can be seen clearly (very high levels actually obscure sight). A history of dust-laden sputum or nasal discharge at the end of the work shift is also a marker of heavy exposure.
Ask whether work surfaces are dusty or damp and whether the paint at the work site is peeling or discolored (eg, from a corrosive atmosphere).
Determine whether strong smells or tastes are present and, if so, whether they diminish over time, suggesting olfactory fatigue.
Find out whether there is any special ventilation system and where the fresh air intake is located (toxins actually can be entrained and recirculated by a poorly placed air intake system).
Establish whether the person has direct skin contact with the materials worked with, especially solvents or other liquid chemicals.
Work in a confined space can be especially hazardous. Examples of such spaces include ship holds, storage tanks, and underground vaults.
Personal protective gear (See Personal protective equipment). Respiratory system and skin protection may be essential for certain workplace exposures. Just as important as the availability of equipment are its proper selection, fit assessment, and use.
Respiratory protection. A disposable paper-type mask is inadequate for most exposures. A screw-in cartridge-type mask whose cartridges are rarely changed is also unlikely to be effective. For an air-supplied respirator with an air supply hose, ascertain the location of the air intake.
Skin protection. Gloves and other skin protection should be impervious to the chemical(s) used.
Temporal aspects of exposure
The most important question is whether there have been any changes in work processes, products used, or job duties that could be temporally associated with the onset of symptoms.
Patterns of recurring symptoms linked to the work schedule can be important—for example, if symptoms are different on the first day of the workweek, at the end of the first shift of the week, at the end of the workweek, or on days off or vacation days.
Other aspects of exposure
It is critical to assess whether anyone else from the workplace is also symptomatic and, if so, to identify that person’s precise job duties.
Eating in work areas can result in exposure through ingestion; smoking on the job can lead to inhalation of native materials or toxic pyrolysis products.
Determine whether a uniform is provided and who launders it. For example, family lead poisoning can occur through work clothes brought home for laundering. After certain types of contamination (eg, with pesticides), a uniform should be destroyed, not laundered and reused.
Find out how large the work site is because small operations are often the most poorly maintained. An active work safety and health committee suggests that better general protection is in place.
Common toxic materials of frequent concern that are commonly addressed in the occupational exposure history
Two-part glues, paints, or coatings that must be mixed just before use, or one-part variants of these, such as urethanes and epoxides. These reactive polymers are often irritants or sensitizers.
Solvents or degreasers, especially if the level of exposure by inhalation or through skin contact is high enough to cause dizziness, nausea, headache, or a sense of intoxication.
Respirable dusts, including friable insulation or heat-resistant materials, and sand or quartz dust, especially from grinding or blasting.
Combustion products or fumes from fires, flame cutting, welding, and other high-temperature processes.
Identifying the specific chemical exposures involved may be difficult because the worker may not know or may not have been precisely informed about them. Even the manufacturer may be uncertain because components of the chemical mixture were obtained elsewhere or because exposure is due to undetermined process by-products. Finally, the exposure may have occurred long before. Aids to exposure identification include the following:
Product labels. Obtain product labels as a first step. However, the label alone is unlikely to provide detailed information.
Material safety data sheets. Contact the manufacturer directly for a material safety data sheet (MSDS). These must be provided upon a physician’s request in cases of suspected illness. Do not take no for an answer. You may need to supplement the MSDS information through direct discussion with a technical person working for the supplier because key information may not be provided (eg, an ingredient may not be specified because it is a small percentage of the product or treated as a “trade secret”).
Computerized databases. Consult computerized databases, such as Poisindex, HSDB (Hazardous Substances Data Bank), Toxnet, TOMES (Toxicology Occupational Medicines and Environmental Sciences), NIOSHTIC (NIOSH Technical Information Center), and others, for further information. Regional poison control centers (1-800-222-1222) can be extremely useful.
Department of Transportation identification placards. In cases of transportation release, DOT identification placards may be available (See Figure IV–3).
Industrial exposure data. Rarely, detailed industrial hygiene data may be available to delineate specific exposures and exposure levels in cases of ongoing, chronic exposure.
Existing process exposure data. Often, exposure is assumed on the basis of known specific exposures linked to certain work processes. Selected types of exposure are listed in Table IV–1.
Table IV-1 Selected Job Processes at High Risk for Specific Toxic Exposures
Table IV-1 Selected Job Processes at High Risk for Specific Toxic Exposures
Job Process
Exposure
Aerospace and other specialty metal work
Beryllium
Artificial nail application
Methacrylate
Artificial nail removal
Acetonitrile, nitroethane
Artificial leather making, fabric coating
Dimethylformamide
Auto body painting
Isocyanates
Battery recycling
Lead and cadmium fumes and dust
Carburetor cleaning (car repair)
Methylene chloride
Cement manufacture
Sulfur dioxide
Commercial refrigeration
Ammonia, sulfur dioxide
Concrete application
Chromic acid
Custodial work
Chlorine (hypochlorite + acid mixes)
Dry cleaning
Chlorinated hydrocarbon solvents
Epoxy glue and coatings use
Trimellitic anhydride
Explosives work
Nitrate oxidants
Fermentation operation
Carbon dioxide
Fire fighting
Carbon monoxide, cyanide, acrolein
Fumigation
Methyl bromide, methyl iodide, Vikane (sulfuryl fluoride), phosphine
Furniture stripping
Methylene chloride
Furniture and wood floor finishing
Isocyanates
Gas-shielded welding
Nitrogen dioxide
Gold refining
Mercury vapor
Hospital sterilizer work
Ethylene oxide, glutaraldehyde
Indoor forklift or compressor operation
Carbon monoxide
Manure pit operation
Hydrogen sulfide
Metal blade specialty cutting
Tungsten carbide-cobalt
Metal degreasing
Chlorinated hydrocarbon solvents
Metal plating
Cyanide, acid mists
Microelectronics chip etching
Hydrofluoric acid
Microelectronic chip doping
Arsine gas, diborane gas
Paper pulp work
Chlorine, chlorine dioxide, ozone
Pool and hot tub disinfection
Chlorine, bromine
Pottery glazing and glassmaking
Lead dust
Radiator repair
Lead fumes
Rayon manufacturing
Carbon disulfide
Rubber cement glue use
n-Hexane, other solvents
Rocket and jet fuel work
Hydrazine, monomethylhydrazine
Sandblasting, concrete finishing
Silica dust
Sewage work
Hydrogen sulfide
Silo work with fresh silage
Nitrogen dioxide
Sheet metal flame cutting or brazing
Cadmium fumes
Structural paint refurbishing
Lead fumes and dust
Tobacco harvesting
Nicotine
Water treatment or purification
Chlorine, ozone
Welding galvanized steel
Zinc oxide fumes
Welding solvent-contaminated metal
Phosgene
Organ-specific occupational toxidromes. A list of the 10 leading work-related diseases and injuries has been developed by the National Institute for Occupational Safety and Health (NIOSH). This list, organized generally by organ system, is included in Table IV–2, along with additional disorders not on the original NIOSH list.
Table IV-2 Leading Work-Related Diseases and Injuries and Their Relevance to Clinical Toxicology
Table IV-2 Leading Work-Related Diseases and Injuries and Their Relevance to Clinical Toxicology
Work-Related Conditions
NIOSHa
Relevance
Examples of Relevant Conditions
Occupational lung disease
Yes
High
Irritant inhalation
Musculoskeletal
Yes
Low
Chemical-related Raynaud syndrome
Cancer
Yes
Moderate
Acute leukemia
Trauma
Yes
Low
High-pressure paint gun injury
Cardiovascular disease
Yes
Moderate
Carbon monoxide ischemia
Disorders of reproduction
Yes
Low
Spontaneous abortion
Neurotoxic disorders
Yes
High
Acetylcholinesterase inhibition
Noise-induced hearing loss
Yes
Low
Potential drug interactions
Dermatologic conditions
Yes
Moderate
Hydrofluoric acid burns
Psychological disorders
Yes
Moderate
Postexposure stress disorder
Hepatic injury
No
High
Chemical hepatitis
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