Validation of a military burn pit surrogate generator and aerosol exposure system

ABSTRACT The United States deployed ~3 million service members to the Middle East since 2001. Approximately 600,000 Veterans now suffer from “Chronic Multisymptom Illness” (CMI). The “Promise to Address Comprehensive Toxics or PACT Act, signed into law in 2022, now exists to mitigate Veteran suffering associated with military burn pit exposures. The single most common risk factor among these ailing Veterans is inhalation exposure to complex combustion emissions generated by these burn pits. CMI symptoms include: cardiopulmonary morbidity, cognitive impairments, behavioral disorders, fatigue/diminished energetics, compromised immune function and pain. Despite the fact that the number of Veterans suffering from CMI is forecast to surge, two major knowledge gaps exist: 1) the exposure conditions that lead to CMI are poorly characterized, and 2) the mechanism(s) of CMI development cannot currently be studied as a model of exposure does not exist. Neither of these gaps can be properly addressed in the absence of an emission generator capable of mimicking burn pits and their diverse parameters of operation. The objective of this application is to validate our novel generation system and identify the most relevant fuel mixtures that accurately recapitulate military burn pit emissions. This will be achieved in our unique Inhalation Facility located in the WVU Center for Inhalation Toxicology. AIM 1: Determine, optimize and validate the burn pit surrogate emission generator parameters of operation. We have developed an automated combustion chamber with a hopper feed system to operate under a variety of temperatures, feed speeds, and air richness. Combustion is enhanced by a fuel feed system that independently drips jet fuel (the most common accelerant used in burn pits) into the combustion chamber. The goal is to identify the full range of these parameters, and couple them with the resultant emissions delivered to the exposure chamber for real-time aerosol characterization and sampling. AIM 2: Determine the operable proportions of representative mixed fuels that when combusted, produce reliable and repeatable emissions for real-time aerosol characterization and inhalation exposures. We manufacture combustible pellets with a variety of raw materials to feed into our surrogate emission generator. These materials have different combustion temperatures, and varying the mixture and/or amount/pellet produces different emissions. The goal is to identify a range of mixture proportions that combust and smolder over the full operating parameters, that produce reliable and repeatable emissions in the exposure chamber. Upon completion, a novel inhalation exposure instrument will be validated and optimized for subsequent CMI studies. Fuel mixtures and accelerant delivery rates will be established as the standards for these studies. Identification of these parameters is critical for rigor and reproducibility, and will also initiate the foundation for future CMI research that ultimately benefits Veteran health. Added value exists as the surrogate generator is capable of combusting virtually any substance. Therefore, it will also be invaluable in assessing first- responder exposures to diverse conditions such as domestic and wildland urban interface (WUI) fires.