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.

Development of pituitary lesions in ND4 Swiss Webster mice when estimating the sensory irritancy of airborne chemicals using ASTM method E981-84.

This study determined the origin of pituitary lesions found in male ND4 Swiss Webster mice following a single head-only exposure to inhaled test materials using ASTM E981-84, standard test method for estimating sensory irritancy of airborne chemicals. Necropsy and histopathology data were evaluated due to the occurrence of unexpected pituitary lesions in sham control and exposure groups. Groups of four mice were restrained in body plethysmographs and exposed for 30 min to increasing dust concentrations of one of three test chemicals to assess the ability to cause sensory irritation. Sham control and test material-exposed mice were sacrificed after a single exposure and subjected to a complete necropsy and microscopic evaluation of the pituitary gland. Control mice remained in the animal room and were not restrained in the plethysmograph. Gross observation at necropsy showed pituitary lesions in one of seven unrestrained control mice (revised to zero of seven after microscopic examination). Seven of seven sham control mice had pituitary lesions, suggesting that the lesions were not related to test material exposure. Each test material-exposed group also had pituitary lesions with high incidence (52/60 for all groups combined), which was not exposure concentration-dependent. Microscopic evaluation of the pituitary glands revealed that darkening of the gland was due to hemorrhage and confirmed that the lesions developed with 100% incidence (19/19) in plethysmograph-housed animals. The rubber neck seal used to restrict animal movement in the plethysmograph appears to have caused an increase in pressure in the blood vessels in the pituitary gland; vessels then ruptured and hemorrhaged. This finding should not adversely affect sensory irritation responses evaluated with this method.

Respiratory peripheral sensory irritation and hypersensitivity studies with glutaraldehyde vapor.

Overexposure to glutaraldehyde (GA) vapor (CAS No. 111-30-8) is known to cause peripheral sensory irritant effects in humans. Respiratory sensory irritation was investigated in male ND4 Swiss Webster mice to quantify the effect, and also as a preliminary to a study of the respiratory sensitizing potential of GA. For the irritation study, groups of four mice were exposed to seven different GA vapor concentrations in the range of 1.6 to 36.7 ppm, while respiratory rate (RR) was measured by plethysmography. Concentration-related decreases in RR were measured, with a maximum decrease at 3 to 20 min, which was sustained, indicating an absence of desensitization. The 50% decrease in RR (RD50) was calculated to be 13.9 ppm, which accords with the known sensory irritancy of GA and other aliphatic aldehydes. In a separate study, the respiratory sensitizing potential of GA vapor was studied in male Hartley guinea pigs, who were exposed for one hour per day for five consecutive days to an inducing GA vapor concentration of 13.9 ppm. Subsequent challenge exposures to 4.4 ppm at 14, 21, and 35 days after the final induction exposure did not produce any evidence of respiratory sensitization. The above findings confirm that GA vapor is a moderately potent peripheral sensory irritant, and does not produce respiratory sensitization in the guinea pig at the concentrations tested.

Particulate inhalation during the removal of amalgam restorations.

An aerosol that contains amalgam particles is created when a high-speed hand-piece is used to remove an existing amalgam restoration. Those particles smaller than 10 microns are considered to be fully respirable. This means that a significant percentage of the particles have the potential to travel to the terminal alveoli, where they may become lodged. Long-term exposure to fully respirable particles may compromise a person's respiratory function. Amalgam restorations were placed in the typodont teeth of a mannequin designed to simulate the head and the respiratory tract of a patient. The amalgam restorations were removed under three experimental conditions: dry cut (control), wet cut (water spray) with high-velocity evacuation, and wet cut with high-velocity evacuation and a rubber dam. Particulate exposure was evaluated in the simulated respiratory tracts of the patient and the dentist that were equipped with ambient particle sizing samplers. Use of water spray and high-velocity evacuation significantly reduced patient exposure to particles. The use of a rubber dam, together with water spray and high-velocity evacuation, was responsible for a further significant reduction of exposure to particles when compared with water spray and high-velocity evacuation alone. The dentist, however, was exposed to moderate levels of fully respirable particles for all conditions tested. It is therefore recommended that all dental personnel wear face masks while removing existing amalgam restorations.

Subacute inhalation toxicity testing with iodoform vapor.

Subacute inhalation experiments were conducted to determine the LC50 value for adult Sprague-Dawley rats exposed to iodoform vapor. Each dose consisted of 5 males and 5 females that were together for a 7-h exposure or sham exposure and then separated for observation over the subsequent 24-h period. The rats were deprived of food and water during actual exposure or sham exposure. Exposures were conducted in a custom-designed 75-l glass chamber. Vapor concentrations were verified in samples taken from the exposure chamber. Under the conditions of the experiments the 7-h LC50 was found to be 183 ppm. The second objective of these experiments was to determine the toxic effect of iodoform vapor on rats exposed for 7 h/d for 7 consecutive days. Three groups of 5 young adult male and 5 female rats were used. One group served as a sham control and the other groups were exposed to 1 and 14 ppm iodoform vapor. No significant differences were noted in food and water intake, urine and feces output, and intestinal transit performance in either exposed group. No remarkable changes were noted in SMA 12/60 blood values for either exposed group. The only histopathological manifestation noted was the presence of mineralized deposits in the medullary renal tubules of some of the rats from the 14-ppm group.