[The actual state of occupational exposure to chlorpyrifos of termite control workers]

Chlorpyrifos, an organophosphorus insecticide, has been used as a termite control agent since regulatory measures against the use of chlordane were taken in September, 1986. In this study the actual state of occupational exposure to chlorpyrifos of termite control workers was investigated. The findings obtained were as follows. The concentration of chlorpyrifos in the air (near the mouth) was about 10 times higher (1.7-2.3 mg/m3) under the floor than the threshold-limit value (0.2 mg/m3) proposed by the ACGIH and rose close to the threshold-limit value even above the floor. Regarding the performance of the absorption can of the mask, generally satisfactory results were obtained. The adhesion of this compound to the work outfit was conspicuous during the spraying work under the floor, and it was often noted on the right forearm (12 micrograms/cm2), on the left knee (10 micrograms/cm2), on the right knee (9 micrograms/cm2) and on the face (5 micrograms/cm2). The rate of this compound penetrating through the work outfit amounted to an average of 40 percent, making it clear that a considerable amount of the compound penetrated the work outfit. Furthermore, direct adhesion of the compound to the neck was considered. These results suggested the dermal-exposure to chlorpyrifos of termite control workers. This compound was detected, though the quantity was very small, in blood after work, which was definitely indicative of exposure at the time of termite control work. The plasma cholinesterase activity in the termite control workers was within the normal range before the busy termite control season but fell off markedly when the full-scale termite control season set in. It is suggested that a decrease in plasma cholinesterase activity occurs due to chlorpyrifos exposure.