title: Subchronic JP-8 jet fuel exposure enhances vulnerability to noise-induced hearing loss in rats.
abstract: Both laboratory and epidemiological studies published over the past two decades have identified the risk of excess hearing loss when specific chemical contaminants are present along with noise. The objective of this study was to evaluate the potency of JP-8 jet fuel to enhance noise-induced hearing loss (NIHL) using inhalation exposure to fuel and simultaneous exposure to either continuous or intermittent noise exposure over a 4-wk exposure period using both male and female Fischer 344 rats. In the initial study, male (n = 5) and female (n = 5) rats received inhalation exposure to JP-8 fuel for 6 h/d, 5 d/wk for 4 wk at concentrations of 200, 750, or 1500 mg/m³. Parallel groups of rats also received nondamaging noise (constant octave band noise at 85 dB(lin)) in combination with the fuel, noise alone (75, 85, or 95 dB), or no exposure to fuel or noise. Significant concentration-related impairment of auditory function measured by distortion product otoacoustic emissions (DPOAE) and compound action potential (CAP) threshold was seen in rats exposed to combined JP-8 plus noise exposure when JP-8 levels of 1500 mg/m³ were presented with trends toward impairment seen with 750 mg/m³ JP-8 + noise. JP-8 alone exerted no significant effect on auditory function. In addition, noise was able to disrupt the DPOAE and increase auditory thresholds only when noise exposure was at 95 dB. In a subsequent study, male (n = 5 per group) and female (n = 5 per group) rats received 1000 mg/m³ JP-8 for 6 h/d, 5 d/wk for 4 wk with and without exposure to 102 dB octave band noise that was present for 15 min out of each hour (total noise duration 90 min). Comparisons were made to rats receiving only noise, and thosereceiving no experimental treatment. Significant impairment of auditory thresholds especially for high-frequency tones was identified in the male rats receiving combined treatment. This study provides a basis for estimating excessive hearing loss under conditions of subchronic JP-8 jet fuel exposure.
authors.affiliation: Jerry Pettis Memorial VA Medical Center, Loma Linda, California 92357, USA. larry.fechter@va.gov
authors.forename: L D
authors.initials: LD
authors.lastname: Fechter
authors.forename: J W
authors.initials: JW
authors.lastname: Fisher
authors.forename: G D
authors.initials: GD
authors.lastname: Chapman
authors.forename: V P
authors.initials: VP
authors.lastname: Mokashi
authors.forename: P A
authors.initials: PA
authors.lastname: Ortiz
authors.forename: J E
authors.initials: JE
authors.lastname: Reboulet
authors.forename: J E
authors.initials: JE
authors.lastname: Stubbs
authors.forename: A M
authors.initials: AM
authors.lastname: Lear
authors.forename: S M
authors.initials: SM
authors.lastname: McInturf
authors.forename: S L
authors.initials: SL
authors.lastname: Prues
authors.forename: C A
authors.initials: CA
authors.lastname: Gearhart
authors.forename: S
authors.initials: S
authors.lastname: Fulton
authors.forename: D R
authors.initials: DR
authors.lastname: Mattie
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D000818:Animals; D003051:Cochlea / Q000187:drug effects / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000209:etiology*; D006320:Hearing Tests; D006838:Hydrocarbons / Q000633:toxicity*; D019570:Inhalation Exposure / Q000009:adverse effects*; D008297:Male; D019055:No-Observed-Adverse-Effect Level; D051381:Rats; D011916:Rats, Inbred F344; D059550:Toxicity Tests, Subchronic
chemical_list: D000393:Air Pollutants; D006838:Hydrocarbons; C098607:JP8 aviation fuel