Respiratory sensitization to konjac flour in guinea pigs

Medical reports linking asthma and occupational exposure to airborne powder produced during the manufacture of konjac flour have been reported in the literature. This study was conducted to investigate whether exposure to food grade konjac flour, which is the end product of the manufacturing process, could produce respiratory hypersensitivity using an animal bioassay developed by Karol et al. (Karol, Y., Ioset, H.H., Riley, E.J., Alarie, Y.C., 1978. Am. Ind. Hyg. Assoc. J. 39, 546-556). Groups of guinea pigs were randomly assigned to a negative control, a konjac flour exposure group, or a positive control group exposed to trimellitic anhydride (TMA). The study design included five consecutive days of inhalation induction exposures followed by three inhalation challenge exposures on days 19, 26 and 40. Positive control guinea pigs were exposed to 98 mg/m3 TMA during the induction exposures and 57-67 mg/m3 TMA during the challenge exposures. The mean (+/-S.D.) konjac flour concentration during the induction exposures was 111+/-8.3 mg/m3 and the exposure concentrations of konjac flour during the challenge exposures ranged from 50 to 68 mg/m3. The criteria used to define respiratory tract sensitization (an increase in respiratory rate of 36% and a change in the respiratory waveform) were met by 25% of the animals at each challenge in the konjac flour group. In addition, a few animals responded with slightly lower increases in respiratory frequency and a change in waveform suggestive of a slight pulmonary hypersensitivity response. Guinea pigs that responded during the first challenge also responded during subsequent challenges. No changes in respiratory rate or waveform were noted in animals assigned to the negative control group when challenged with konjac flour. The results of this study indicate that respiratory hypersensitivity to food grade konjac flour can be induced in guinea pigs following repeated inhalation exposure. Therefore, proper engineering controls or personal protection equipment should be utilized to prevent respiratory sensitization in those who may be occupationally exposed to food grade konjac flour.