Increased formaldehyde in jet engine exhaust with changes to JP-8, lower temperature, and lower humidity irritates eyes and respiratory tract

Background: Formaldehyde (FA) in exhaust from F-4 aircraft with low smoke c ombustor(LSC)J79 engines has been reported to be of sufficient concentratio n to Cause irritation. It has also been noted that eve and respiratory irri tation became more frequent and severe after the fuel was changed from JP-4 to JP-8. The present study investigated the effect of jet fuel and power s etting on formaldehyde concentrations in the exhaust. We also investigated the exposure to formaldehyde among pilots and flight line personnel. Method s: The exhaust from LSC J79 engines using different types of fuel (JP-8 and JP-4) was sampled 50 m behind the engine at different power settings in Ju ly (summer season in Japan) and February (winter season ). It was also samp led at 75% power settings using JP-8 in July. Results: At an idle power set ting, the FA concentration was higher in the exhaust of engines using JP-8 (1.31 ppm in July and 2.78 ppm in February) than in engines using JP-4(0.95 ppm in July and 1.84 ppm in February). The FA concentration increased as b oth ambient temperature and relative humidity decreased in the sampling atm osphere. The FA concentration of JF-8 fuel at an idle power setting 65% was higher than that at a 71.5% power setting (1.32 ppm and 0.86 ppm, respecti vely). Conclusions: The FA concentrations in LSCJ79 engine exhaust varies d epending on the type of fuel, engine power settings, and ambient air condit ions. A high FA concentration at ground level due to a change in the fuel t ype, low temperature, and humidity, causes frequent severe eye and respirat ory irritation.