High-Level Petroleum Hydrocarbon Vapor Exposures Induce Toxic Encephalopathy
This case study demonstrates how causation can be demonstrated by weight of evidence
(WOE) and how objective investigation of contributing factors can play a pivitol role in
formulating an expert opinion to reasonable toxicological certainty.
A process engineer worked for seven years at a petroleum refinery. After several years
of near-continuous exposure to benzene, hydrofluoric acid, gasoline and other volatile
petroleum hydrocarbon vapors, he began experiencing nocturnal headaches, difficulty
sleeping, situational stress and anxiety. Although he initially attributed his symptoms
to job stress, he began experiencing extreme fatigue, diminished energy, lack of
concentration, body aches, chills, mood swings, confusion, increased somnolence
His physician initially attributed the symptoms to thyroid disease, but this diagnosis
was later ruled out. He transferred to an indoor office in the hope of
improvement, but instead, his symptoms grew worse. He began experiencing intermittent
jerking movements and involuntary muscle twitches. Eventually, he could no longer
perform his job duties. An objective brain scan resulted in a diagnosis of occupational,
exposure-based toxic encephalopathy consistent with exposure to hydrocarbons over
a period of years. Soon the symptoms increased to such an extent that he became
Causation Demonstrated by Weight-of-Evidence
Plaintiff subsequently filed a lawsuit against the company who promptly denied any
wrongdoing. The company attempted to prove in court that plaintiff's injury could
not have been caused by the work environment or by negligence. Dr. Sawyer was retained
to determine whether or not the exposures were responsible. However, such a
determination required compelling, demonstrable weight-of-evidence (WOE) meeting
generally-accepted causation criteria which unequivocally demonstrated and isolated
the factors contributing to the plaintiff's condition.
Upon reviewing the available historical documentation, Dr. Sawyer found that the
refinery had been cited for numerous hazardous violations over the years which put
its workers, including the plaintiff, at risk for toxic exposures. He further discovered
that proper personal protective equipment (PPE) had generally not been provided.
Dr. Sawyer compiled an exhaustive set of industrial hygiene data (all of which had
been created by the company itself) which clearly demonstrated a historical pattern
of violations and repeated overexposures.
Toxic encephalopathy is a type of structural brain damage or brain dysfunction secondary
to an exposure from a chemical causing severe injury and destruction of neurons.
The criteria for toxic encephalopathy induced by long-term occupational exposure
to organic solvents is specific. A toxicological diagnosis of solvent-induced toxic
encephalopathy requires that the following criteria be met:
- Long or intense exposure to solvents approaching or exceeding NIOSH recommended
exposure limits (RELs)
- Relevant symptoms such as increased fatigue, memory impairment, difficulties in
concentration and personality changes such as passivity
- The presence of pathological findings in terms of an objective measurement
- A relation in time between exposure and the development of symptoms and signs
- No other obvious cause of the disease
- Effects on the central nervous system which persist even after exposure had ceased
To evaluate these criteria, Dr. Sawyer produced a toxicological report which detailed
the following evidence supported by numerous peer-reviewed studies:
- Exposure: Plaintiff worked for years in areas of heavy vapor
concentrations (Fluid Catalytic Cracking, Hydroalkylation, etc) at levels near and
sometimes in excess of NIOSH recommended exposure limits (RELs). His family frequently
noted that he came home smelling like gasoline and other chemicals.
- Onset of Symptoms: Plaintiff experienced significant neurological
symptoms beyond work hours including nocturnal headaches, difficulty sleeping,
stress and anxiety, extreme fatigue, diminished energy, lack of concentration, body
aches, chills, mood swings, confusion, increased somnolence, depression, intermittent
jerking movements and muscular twitching. These symptoms were all reasonably attributable
to excessive hydrocarbon exposures. Plaintiff was ultimately diagnosed by a physician
with toxic encephalopathy.
- Sequence of Events: Symptom onset was consistent with plaintiff's
employment history and with numerous peer-reviewed studies and generally-accepted
diagnostic criteria (published in referenced studies) and as defined by the World
Health Organization1 and NIOSH.2
- Lack of Alternate Causation: Plaintiff was a lifetime non-smoker
with no history of substance abuse. His medical records revealed no reasonable alternative
causes. However, substantial evidence existed for over-exposure to neurotoxic hydrocarbons
at the refinery over a period of years.
- History of Safety Violations: The refinery had been cited for
numerous violations that placed its workers (including plaintiff) at risk for toxic
exposures. Records also showed that the company was significantly under-reporting
its leak rates and failing to properly monitor its units for leaks.
- Inadequate Medical Monitoring: Although the company claimed that
industrial hygiene personnel were monitoring hundreds of workers for toxic exposures,
there were only three such individuals in the facility, none of whom were certified
- Inadequate Medical Testing: Only a single urine phenol sample
(which was deemed unreliable) was collected from plaintiff during seven years of exposure
in a known hazardous atmosphere. This single sample represented less than 0.057%
(1 out of 1,750 days) of his total exposure history. The physician also opined that
plaintiff's symptoms became worse at his office job as he had actually moved closer
to sources of vapor and his exposures now occurred in a confined space.
- Documented Instances of Benzene Emissions: Oily water and sewer
waste had infiltrated the storm sewer system and waste was being vented into the
atmosphere at a rate equal to or exceeding 35 times the permissible exposure limit
under OSHA regulations. The company was also aware of the leakage of hazardous chemicals
under the plant and had been cited for numerous benzene-related safety violations.
- OSHA Non-Compliance (Benzene): The company's inspection record
showed numerous instances of non-compliance with benzene emission levels permitted
by OSHA, particularly in areas in which the plaintiff worked. There was also considerable
evidence in the form of historical documentation that volatile hydrocarbons from
various leaks were measured near valves and fittings in excess of 500 to 1000 PPM,
far in excess of any legally-permissible vapor levels.
- Broad Range of Contaminants: Plaintiff was exposed to benzene,
toluene, ethylbenzene, xylenes (a mixture known as "BTEX"), gasoline, jet fuel and a wide range of aliphatic
hydrocarbons consistent with ongoing refinery operations. These hydrocarbons
have been confirmed in multiple human epidemiological studies to induce toxic encephalopathy
among workers chronically exposed to levels near the OSHA PEL.
- Excessive TPH (Total Petroleum Hydrocarbons): The limited industrial
hygiene surveys conducted at the refinery revealed numerous violations of the OSHA
PEL for benzene. The industrial hygiene data revealed measurements of benzene and
TPH within the refinery at a ratio of 1 part benzene per 97.1 ±15 parts TPH.
Applying this ratio to out-of-compliance benzene readings within various refinery
units revealed TPH levels in the 97.1 PPM to 46,802 PPM range. TPH mixtures composed
of BTEX and aliphatic hydrocarbons have been demonstrated in human epidemiological
studies to induce toxic encephalopathy within that range of exposure.
To visualize this final point, Dr. Sawyer produced a compelling demonstrative for
the judge and jury which characterized benzene air samples taken at the refinery during
plaintiff's period of employment. This demonstrative (below) showed that out of
26 air samples collected over a period of several days, 21 of them failed to meet
OSHA quality standards.
This demonstrative showed not only the degree of fugitive vapors present in the
environment at the time samples were taken, but also portrayed the scope of violations
characterizing the company's inspection record. This damaging piece of evidence
clearly demonstrated that the average airborne concentrations of petroleum hydrocarbon
vapors were far above the Permissible Exposure Limit (PEL) and that such violations
were a frequent and common occurrence at this particular refinery. Dr. Sawyer further
demonstrated that the company was out of compliance with NIOSH-recommended exposure
limits in numerous respects and that such events were consistent over a period of
Dr. Sawyer provided both forensic evidence and causation weight-of-evidence in light
of the available facts and scientific evidence with respect to the induction of
toxic encephalopathy. Extrapolation of the benzene air levels to provide total petroleum
hydrocarbon air levels revealed that exposures within the range consistent with
the induction of toxic encephalopathy occurred with benzene measured at levels
far in excess of the OSHA PEL.
Dr. Sawyer was able to demonstrate to reasonable toxicological certainty that plaintiff's
exposure, symptoms and history were fully consistent with the diagnosis of toxic
encephalopathy resulting from excessive exposures to hydrocarbon leaks, spills and
emissions. The court denied repeated attempts by defendant to challenge and exclude
Dr. Sawyer's report and testimony. The company ultimately settled the case ahead of
a likely verdict in favor of plaintiff.
(Disclaimer: Toxicology case studies are impartial and objective summaries of toxicological
matters in which TCAS was retained for the purpose of assessing health-based
factors which, in some cases, led to a determination of causation. No names or identifying
information have been provided due to privacy and legal considerations. In the above
matter, Dr. Sawyer was retained by plaintiff.)
Notes and References
- WHO, Nordic Council of Ministers. "Organic solvents and the central nervous system," EH5. Copenhagen, Denmark, 1985.
- NIOSH, "Current Intelligence Bulletin 48, Organic Solvent Neurotoxicity," March 31, 1987, US Department of Health and Human Services. Ohio.
- Adapted from photo by Carlos Koblischek
- TCAS report demonstrative (redacted), graphical image © Copyright 2023 TCAS, LLC.