Fuel Type Influences Developmental Toxicity of Burn Pit-related Smoke in Zebrafish
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Exposure to smoke emitted from burn pits in military bases has been linked with adverse health effects among military personnel and civilians. Although previous studies have linked air pollution exposure from other sources to congenital defects, the potential developmental toxicity of burn pit-related emissions remains unclear. The purpose of this study was to assess the developmental toxicity of extractable organic material derived from burn pit-related smoldering smoke condensates from 5 fuels: plywood (representing ammunition boxes), cardboard (representing military spec boxes), plastic (a mixture of low-density polyethylene, high-density polyethylene, polyethylene terephthalate, and polystyrene pellets), mixture (a mixture of plywood, plastic, and cardboard), and mixture plus diesel (the mixture material treated with diesel fuel, which is often used as an accelerant in burn pits), in zebrafish. We hypothesized that developmental toxicity is dependent on fuel type. To test this, zebrafish larvae (n = 8/treatment group) were exposed from 6 hours post fertilization through 4 days post fertilization (dpf) to 0.4% dimethyl sulfoxide vehicle or extractable organic material from burn pit smoke (0.01-40 µg/ml; half-log intervals) from each of the 5 condensates in 96-well plates and assessed by a blinded researcher for malformations at 5 dpf using visual observation with light microscopy, a bioimager, and analysis software. All burn pit condensates caused mortality at the highest concentration and concentration-dependent effects including delayed swim bladder inflation, pericardial edema, scoliosis, tail kinks, and/or craniofacial deformities in the remaining treatment groups. There were generally minimal effects up to a concentration of 1.27 mg/ml. Condensates from plastic and the mixture containing plastic caused a higher rate of deformities than other materials. Taken together, these results indicate that fuel type burned impacts the severity of burn pit smoke-induced developmental toxicity in zebrafish. These effects will be correlated with combustion byproduct chemistry to identify the specific chemical classes most responsible for toxicity (This abstract does not reflect U.S. E.P.A policy).