Jet Fuel Does Not Directly Cause Hypothyroidism Through Any Established Mechanism
There is no documented causal pathway by which jet fuel exposure leads to hypothyroidism. The available evidence shows jet fuel exposure is associated with neurologic, cognitive, respiratory, and possibly cancer outcomes, but thyroid dysfunction is not among the established health effects 1, 2.
What the Evidence Actually Shows About Jet Fuel Exposure
Documented Health Effects from Jet Fuel
- Epidemiologic studies demonstrate slight evidence of associations between jet fuel exposure and neurologic, cognitive/behavioral, respiratory, and cancer outcomes, but thyroid effects are notably absent from this list 2.
- Over 2 million military and civilian personnel are occupationally exposed to kerosene-based jet fuels annually, with JP-8 representing the largest single chemical exposure in the U.S. military 3.
- Airport personnel in ground-support functions show biomarkers of exposure and effect, with proximity to running jet engines associated with increased disease risk and hospital admissions 4.
Composition and Exposure Routes
- Jet fuels are complex mixtures of up to 260+ aliphatic and aromatic hydrocarbon compounds (C6-C17+), including potential toxicants such as benzene, n-hexane, toluene, xylenes, and polycyclic aromatic hydrocarbons 3.
- Exposure occurs through dermal absorption, pulmonary inhalation, or oral ingestion of raw fuel, vapor phase, aerosol phase, or fuel combustion exhaust 3.
- Personal exposure measurements demonstrate demonstrable JP-8 exposure for all subjects tested, ranging from slight elevations to >100 times control values 5.
Why Hypothyroidism Is Not Linked to Jet Fuel
Absence of Thyroid-Specific Evidence
- The systematic review of epidemiologic literature on jet fuel health effects found indeterminate evidence for most health outcomes, with no mention of thyroid dysfunction as an outcome of interest 2.
- Human epidemiology studies show weak and inconsistent effects without identification of specific causative chemicals for various health outcomes, but thyroid-specific outcomes were not prominently featured 1.
- The available epidemiologic data is sparse with low consistency in methods, limiting definitive conclusions about any thyroid-specific effects 1.
Established Causes of Hypothyroidism
- Hashimoto thyroiditis (autoimmune disease) causes primary hypothyroidism in up to 85% of patients in areas with adequate iodine 6.
- Risk factors for hypothyroidism include genetic factors, iodine deficiency, neck surgery/radiation, pregnancy with underlying autoimmune thyroid disease, and certain medications (immune checkpoint inhibitors, amiodarone) 6.
- Environmental toxicants like uranium have been weakly associated with thyroid cancer in geographic proximity studies, but this represents a different exposure and outcome than jet fuel and hypothyroidism 7.
Critical Distinction: Correlation vs. Causation
If a military service member or airport worker develops hypothyroidism, this represents coincidental occurrence of a common condition (prevalence 0.3%-12% worldwide) in a population with occupational jet fuel exposure, not a causal relationship 6. The temporal association does not establish causation, and no biological mechanism has been identified linking hydrocarbon fuel exposure to thyroid hormone deficiency.
Common Pitfall to Avoid
- Do not attribute every health condition that develops in jet fuel-exposed workers to the exposure itself, as hypothyroidism has well-established causes (primarily autoimmune) that are unrelated to hydrocarbon exposure 6.
- The lack of thyroid-specific findings in comprehensive systematic reviews of jet fuel health effects strongly suggests no causal relationship exists 2, 1.