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Occupational Medicine

Linda Rosenstock, M.D., M.P.H., F.A.C.P. University of California, Los Angeles, School of Public Health
Mark R. Cullen, M.D. Yale University School of Medicine

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 almost always possible to differentiate occupational diseases from their nonoccupational counterparts
Both the likelihood that workplace hazards will produce effects and the severity of those effects are determined by the dose of exposure
Host factors may modify temporal and dose-response correlations
Many workplace hazards and toxins interact with one another and with nonoccupational factors in the induction of disease

Differential Diagnosis

Common Occupational Disorders (Examples of Causal Factors)

Respiratory tract
- Pneumoconiosis (coal, silica, asbestos)
- Asthma (latex, polyurethane)
- Allergic alveolitis (vegetable matter, machining fluids)
- Metal fume fever (metal fumes)
Skin
- Contact dermatitis (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)
- Raynaud phenomenon (repetitive vibrations, vinyl chloride)
- Scleroderma (coal mining)
Nervous system
- 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 [postasphyxiation])
- Chronic encephalopathy (recurrent exposures to organic solvents)
Hematologic conditions
- Hemolysis (lead, organic nitrites)
- Acute hemolysis (nitro and amine compounds)
- Subacute hemolysis (lead)
Disorders of oxygen transport
- Methemoglobinemia (nitro and amine compounds)
- Carboxyhemoglobinemia (carbon monoxide)
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)
- SARS (health care work)
- Anthrax (handling of animals)
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 mining (stonecutting)
- Ceramic 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 (carpentry)
- 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 (chemical industry)
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 other case descriptions?
- Is the timing between exposure and clinical onset compatible with the known biologic facts about the hazard?
- Is the exposure dose within the range of 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?
- Are there alternative ways of constructing the case that better fit the available facts?
- Where there remains significant uncertainty about the cause, how important is it to be certain?
Every patient should be questioned regarding the essentials of occupation, including current and past workplaces, job type, and materials used
Tests for exposure can be interpreted only in the context of the history and clinical problem

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 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
- 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

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

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

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