1. Establish That a Medical Problem Exists
a. Qualify and quantify symptoms and dysfunction as well as work limitations.
b. Uncover chronology and past medical, occupational, environmental and family history.
2. Establish a Medical Diagnosis
a. Document neurological examination and results of appropriate confirmatory testing; MRI, EMG, EEG, neuropsychological testing
3. Consider Common Causes of Medical Diagnosis
a. Consider whether medical, family or unrelated historical events could be the more likely or contributing cause of a medical condition.
b. Consider epidemiology of the diagnosis, ie., common idiopathic presentation, age of onset etc.
c. Is post- traumatic stress involved with this clinical syndrome and a result of the exposure rather than a direct toxic effect?
4. Is There Objective Evidence of Exposure
a. Document blood, urine, hair or other measureable biologic exposure indices, ie., testing results if applicable, as well as industrial hygiene data such as breathing zone assessments, dust sample, or quantity in liquid, solid or gas consumed over time, if applicable.
5. Tapping Biological Data to Support Exposure
a. If no data available, use established literature for an occupation to establish a suspected quantity and duration of dose by either a measure of blood or urine, hair or industrial hygiene data, for this similar individual case. Consider avenue of exposure, inhalation, ingestion or dermal contact and percentage absorbed.
6. Regulatory and Organizational Regulations/ Recommendations
a. Consider federal and state government (OSHA, EPA, ATSDR, Cal OSHA, Cal EPA, etc) and regulatory agency (ACGIH, etc.) protective values and their supporting literature to consider whether a method of exposure to a specific agent for a determined short, medium or long term duration may lead to a health effect acutely, subacutely or chronically and what health effect specifically has led to this regulation or recommendation.
b. Familiarize with terms used to describe worker exposures such as PEL, TWA, TLV, REL, STEL, Ceiling levels and Skin notation dose levels, and those aimed at protecting from environmental exposures such RfD and MRL, LOAEL, NOAEL and CEL.
7. How to Apply This Methodology in a Courtroom
a. Is there literature to support that any occupation or industry, measured or proposed dose or BEI can cause any neurological health effect in humans or animals? Does the literature support that this occupational or industry, and/ or dose for this duration of exposure may cause this specific neurological condition in this individual? Has this analysis considered established criteria for causation?
8. Are Follow-up Tests Consistent with the Diagnosis?
a. Does repeat examination and testing continue to be consistent with a neurological disorder secondary to exposure?
b. Has the condition stabilized or progressed and is this explainable?
9. Consider Subclinical Assessment
a. When no clinical findings are present, neurological/ neuropsychological testing may be important in groups to compare endpoints in those with various intensities or durations of exposures, or between those with and without exposures.
b. This may be sufficient to support that health effects may result from specific exposures.
10. Putting it Together
a. Establishing causation requires diligence and a keen familiarity with established literature on neurology, neuroepidemiology, chemical toxicology and industrial hygiene. The algorithm above is a recommended guideline for this process. It may not be possible to accomplish all of the above steps in establishing causation. Lawyers and experts must work together regardless of objective. Epidemiology in neurotoxicology is often difficult to extrapolate to individual cases due to poor and inconsistent data with many agents and frequent confounding variables. A team approach including an occupational environmental neurologist, an industrial hygienist and possibly other professionals in this field such as occupational medicine physicians, toxicologists, risk assessment professionals and epidemiologists makes for a successful approach to a toxic tort case regardless of plaintiff or defense. The multi-skilled OEN expert offers comprehensive medical-legal services.
About the Author
Jonathan S Rutchik, MD, MPH, FACOEM is board certified in both Neurology and Occupational and Environmental Medicine and is Associate Clinical Professor at University of California at San Francisco. He provides clinical evaluations and treatment, including electromyography, of individuals and populations with suspected neurological illness secondary to workplace injuries or chemical exposure. Dr. Rutchik is also a California State Qualified and Agreed Medical Examiner. He can be reached at firstname.lastname@example.org or (415) 381-3133.