Precautionary Approach to Reduce Occupational Exposures among Airport Apron Workers in the Context of Many Unknowns—A Methodological Position Paper

Airport apron workers are exposed to complex mixtures of volatile and particulate substances generated by jet fuel, exhaust from aircraft main engine and auxiliary power units (APU), and ground-service equipment. Evidence from both commercial and military airport settings indicates potentially serious health risks associated with acute and chronic exposure to these heterogeneous emissions. Emissions include CO, NOx, SO2, PAHs, UFPs, and larger particulates. In addition, there is chronic low-dose exposure to volatile organic compounds (VOCs) and organophosphates (OPs). The limited number of epidemiological studies specifically targeting apron workers report chronic respiratory symptoms. Evidence for cardiovascular effects is inconsistent, and potential neurological impacts are insufficiently explored. Some studies suggest genotoxic effects or elevated cancer risks but are insufficient to support unequivocal conclusions regarding the necessity of stringent risk management measures. Especially combined acute and chronic exposure to the mentioned volatile and airborne substances may represent a substantial but underrecognized risk, particularly with respect to neurotoxic health effects. This emphasizes the need for prospective cohort studies incorporating detailed exposure assessment, biomonitoring critical toxicological endpoints. At the same time, significant uncertainties and the limited availability of up-to-date, well-characterized exposure data, hinder effective risk assessment and management on the apron. This urges for a precautionary approach with priority for kerosene combustion-derived UFPs, due to their potential toxicity at low concentrations and their role as carriers of carcinogenic particle-bound PAHs (pb-PAHs). However, no widely accepted health-based occupational exposure limit (hb-OEL) currently exists for this nanoscale fraction, while UFPs represent a practical indicator for exposure and a useful tool for risk management. Based on existing risk assessment approaches, a combined number-based and mass-based precautionary health-considered OEL for kerosene exhaust emissions (phc-OELKEE) has been proposed. Field measurements indicate that this precautionary threshold is frequently exceeded on the airport apron.