Abstract
The acaroid mite, Tyrophagus putrescentiae, is a household insect and commonly seen in Japan. This mite can be controlled using paper sheets which were sewed up to the entire upper and lower surfaces in Tatami-mat impregnated with fenthion. We conducted the safty evaluation on the paper sheets. Animals were maintained on the Tatami-mat or on the paper sheets during period of one, two and three months. The amounts of fenthion applied were 0 (untreated), 0.25,0.7,2.0 and 6.0g per m^2. In the practical amounts of 0.7g per m^2,the result indicated that there was no adverse effect on the general condition and appearance in the mice and rats as compared with untreated group. On the indirect contact test to the Tatami-mat, the inhibition of plasma and erythrocytes cholinesterase activities were observed in the mice after two to three months period. On the other hand, when animals were directly contacted on the paper sheets, the cholinesterase activity of plasma and body weight gain were reduced in the mice, and also, the inhibition of cholinesterase activity was observed in the brain of rats after one month period.
