Takashi Akiyama

Cumulative toxicity potential of methomyl aerosol by repeated inhalation.

There are few investigations concerning the cumulative toxicity of agricultural chemicals by repeated inhalation. In this study, Wistar male rats were exposed to methomyl powder (mass median aerodynamic diameter, 4.4 microns) for a single 4-hr exposure, or for 4 hr/day, 5 days/week for 3 months. The average exposure concentrations were controlled at 9.9 mg/m3 for the single exposure and at 14.8 mg/m3 for repeated exposures by a dust generator consisting of a continuous fluidized bed with an overflow pipe and a screw feeder. After the repeated exposures, plasma and red cell cholinesterase activities, and lipid concentrations of the rat lungs were measured and histopathological examinations were performed. There was no evidence of cumulative effects on the red cell cholinesterase activity, histopathological changes and lipid concentration in 3-month repeated inhalation.

Pulmonary Deposition of a Coal Fly Ash Aerosol in Rats By Long-Term Inhalation

Fly ash aerosols are carried with the exhaust gases of the coal combustion. The amount of fly ash generated in coal combustion is several hundred times more than that in oil burning. Fly ash is removed by electrostatic precipitators, but some of it escapes these devices and is released into the environment via the smoke stack. The released aerosols contain highly respirable particles and condensed compounds on the surfaces.

Dust Generation Rate from a Fluidized Bed with a Periodic Dust Feed

A theoretical equation is proposed for determining the rate of dust generation from a fluidized bed with a periodic dust feed. The equation is derived from experimental results in a batch fluidized bed in which the dust generation rate decreases exponentially with time. The results obtained using the equation are compared with the experimental results for a fluidized bed with a periodic dust feed and show fairly good agreement.