Best Dx/Best Rx: Occupational Medicine

Occupational Medicine

Tee L. Guidotti, MD, MPH, FACP, DABT, QEP (Air Quality), FRCPC, FCBOM, FFOM
University of Alberta, Edmonton, AB

Definition/Key Clinical Features
Differential Diagnosis (Causes of Dyslipidemia)
Best Tests
Best Therapy
Best References

Definition/Key Clinical Features

Most occupational disorders are pathologically indistinguishable from disorders with more familiar causes
It is often difficult to differentiate occupational diseases from their nonoccupational counterparts and the key to doing so is usually an assessment of exposure to hazards
The likelihood that workplace hazards will produce effects, which effects are observed, and the severity of those effects are determined by the exposure
Host factors may modify temporal and exposure-response correlations
Many workplace hazards and toxins interact with one another and with nonoccupational factors in the induction of disease
Prevention of impairment is a major therapeutic goal for all conditions, and as part of this goal "early and safe return to work" is the short-term objective whenever possible
The assessment of work capacity (fitness for duty) is a serious medical function with consequences for the patient, whether in the form of "a note from the doctor" to certify sickness absence, preplacement evaluation (initial hire), periodic evaluation, or impairment assessment for workers' compensation or other insurance

Differential Diagnosis

Common Occupational Disorders (Examples of Causal Factors)

Respiratory tract
- Pneumoconiosis (coal, silica, asbestos, beryllium, "hard metal")
- Asthma (latex, polyurethane, isocyanates)
- Hypersensitivity pneumonitis (allergic alveolitis) (vegetable matter, machining fluids)
- Metal fume fever (metal fumes)
Skin
- Contact dermatitis, may be allergic or irritant (oils, rubber, metals)
- Acne (herbicides, oils, friction)
- Urticaria (latex, formaldehyde, nickel)
Urinary tract
- Glomerular disease (organic solvents, mercury)
- Tubulointerstitial disease (cadmium, lead)
Liver
- Hepatoportal sclerosis (vinyl chloride, arsenic, thorium)
- Acute or subacute necrosis (organic solvents, TNT, 2-nitropropane)
- Cholestatic hepatitis (methylene dianiline)
- Acute and chronic hepatitis (viruses [hepatitis B, C])
- Granulomatous hepatitis (beryllium, copper)
- Steatosis (organic solvents)
- Hepatocellular injury (lead, arsenic, phosphorus, dioxin)
Musculoskeletal
- Carpal tunnel syndrome (repetitive trauma)
- Repetitive strain disorders (other)
- Raynaud phenomenon (vibrations transmitted to hand and arms, vinyl chloride)
- Rheumatological disorders, including systemic sclerosis (silica)
Nervous system
- Acute loss of consciousness, or "knockdown" (hydrogen sulfide)
- Anesthesia effect (organic solvents)
- Parkinsonism (manganese)
- Peripheral neuropathy (solvents, lead, acrylamide, arsenic, organophosphates)
- Acute encephalopathy (organic solvents, asphyxiants)
- Acute or subacute cholinergic crisis (organophosphate and carbamate pesticides)
- Subacute encephalopathy (mercury, lead, arsenic, manganese, carbon disulfide)
- Subacute peripheral neuropathy (organophosphates)
- Chronic basal gangliar disorder (manganese, carbon monoxide [postrecover])
- Chronic encephalopathy (recurrent exposures to organic solvents)
Hematologic conditions
- Hemolysis (lead, organic nitrites)
- Acute hemolysis (nitro and amine compounds, arsine)
- Subacute hemolysis (lead)
Disorders of oxygen transport and utilization
- Methemoglobinemia (nitro and amine compounds)
- Carboxyhemoglobinemia (carbon monoxide)
- Cyanide (cellular anoxia)
- Inadequate oxygen (low oxygen atmosphere, asphyxiation by gases that displace oxygen)
Disorders of red cell production
- Hyperplastic anemia (lead)
- Aplastic anemia, hypoplastic anemia (ethylene glycol ethers, benzene, arsenic, ionizing radiation, lindane)
- Myelodysplasia (benzene, ionizing radiation)
- Polycythemia (cobalt, carbon monoxide)
Infectious
- Hepatitis B, C (health care work)
- Influenza A (e.g., H5N1) (poultry work)
- H1N1 influenza, SARS (health care work)
- Anthrax, brucellosis, Q fever (handling of animals)
- Tuberculosis
Endocrine and reproductive
- Hypogonadism (lead)
- Azoospermia, oligospermia (DBCP [pesticide], ionizing radiation)
- Teratogenesis (organic mercury, PCBs)

Established and Probable Occupational Carcinogens (Examples of Sources of Exposure)

Lung
- Asbestos (insulation, textiles)
- Ionizing radiation (uranium mining)
- Arsenic (refining)
- Polyaromatic hydrocarbons (coke ovens)
- Nickel (nickel refining)
- Chromium (tanning, pigments)
- Alkylating agents (chemical industry)
- Silica (sandblasting, mining, stonecutting)
- Synthetic vitreous fibers (insulation)
- Formaldehyde (chemicals, plastics)
- Beryllium (nuclear weapons, aerospace industry)
- Cadmium (batteries)
- Environmental tobacco smoke
- Acrylonitrile (plastics)
- 1,3-Butadiene (rubber, plastics)
Pleura and peritoneum
- Asbestos (construction materials)
Upper respiratory tract
- Wood dust (cabinetmaking)
- Nickel (refining)
- Cutting oils (machinists)
- Chromium (plating)
- Asbestos (friction products)
- Formaldehyde (chemicals, plastics)
Urinary bladder
- Benzidine and related amines (dyes, chemicals)
- Arsenic (pesticides)
- Coal tars (roofing)
- Polyaromatic hydrocarbons (aluminum production)
Liver
- Vinyl chloride monomer (plastics)
- Arsenic (pesticides)
Colorectal
- Asbestos (shipbuilding)
- Wood dust (furniture)
- Rubber (rubber manufacturing)
Hematologic system
- Benzene (chemicals, rubber)
- Ionizing radiation (defense industry, health care work)
- Ethylene oxide (chemicals, sterilizers)
Soft tissue
- Dioxin (multiple sources including chemical industry)
- Phenoxyacetic acid pesticides (agriculture)
Brain
- Vinyl chloride (chemical industry)
- Formaldehyde (chemical industry)

Best Tests

Ask the following questions:
- Is the clinical illness, including the history, physical examination, and laboratory findings, consistent with outcomes known for this exposure?
- Is the timing between exposure and clinical onset compatible with the known biologic facts about the hazard?
- Is the exposure within the range of concentrations or doses believed to cause such effects?
- Are there special attributes of the particular patient that make it more or less likely that he or she would be so affected (e.g. atopy)?
- Are there alternative ways of constructing the case that better fit the available facts?
- If there remains significant uncertainty about the cause, how important is it to be certain?
Every patient should be questioned regarding their current occupation. Patients with possible occupational disorders should have an occupational history taken in detail appropriate to the case, including current and past workplaces, job duties, and materials used
Tests for exposure are often used to monitor levels of exposure in workers who are not suspected of having an occupational disorder
Is there functional impairment associated with this condition and is it unlikely to change (i.e. "at permanence") so that permanent impairment can be determined?

Common Occupational Hazards for Which There Are Widely Available Biologic Tests of Exposure

Metals
- Arsenic
  - Transient in urine
  - Hair sampling can detect past exposures
- Cadmium
  - Detectable in urine for many years if there is renal injury
  - Half-life in blood, 100 days
- Fluorides
  - Transient in urine
- Lead
  - Half-life in blood, 40 days
  - Half-life in bone, years (measured by x-ray fluorescence)
- Mercury
  - Detectable in urine for days to weeks
- Carbon monoxide
  - Half-life in blood, 4 hr
- Organophosphate (pesticide)
  - Detectable indirectly by measurement of plasma or red cell cholinesterase (plasma cholinesterase responds and recovers more quickly, red cell cholinesterase may be depressed for days to months)
- Organic solvents
  - Benzene and toluene
    - Metabolites transiently in urine
  - Trichloroethylene and perchloroethlylene
    - In blood and metabolites in urine
  - Other solvents
    - Expired air breath analysis
- Antigens: IgE antibodies measurable by radioallergosorbent test (RAST)
- PCBs: persists in blood

Best Therapy

Therapy depends on specific disorder
Remove patient from exposure to causal hazard

Best References

American College of Occupational and Environmental Medicine. Occupational Medicine Practice Guidelines. Chicago, ACOEM, updated. Available at www.acoem.org

Greenberg M, Hamilton RJ, Phillips SD, et al: Occupational, industrial, and environmental medicine. 3rd ed. Lippincott Williams and Wilkins, Philadelphia, 2003

Guidotti T: The Praeger Handbook of Occupational and Environmental Medicine. Greenwood/Praeger, Santa Barbara CA, 2009

Pascarelli EF, et al: J Occup Rehabil 11:1, 2001 [PMID 11706773]

Rabatin JT, et al: Mayo Clin Proc 76:633, 2001 [PMID 11393503]

Environmental and occupational medicine, 4th ed. Rom WN, Ed. Lippincott Williams and Wilkins, Philadelphia, 2007

Rutchik JS, et al: Clin Occup Environ Med 4:621, 2004 [PMID 15465472]

Textbook of Clinical Occupational and Environmental Medicine, 2nd ed. Rosenstock L, et al, Eds. Elsevier Saunders Co, London, 2005

January 2010