[Variations in blood cholinesterase activity and exposure to chlorpyrifos in termite-control workers]

Chlorpyrifos, an organophosphate insecticide, has often been used as a termite-control agent since the advent of regulatory measures against the use of chlordanes in September 1986. A current concern is hazards such as organophosphorus poisoning among termite-control workers. In this study, the blood cholinesterase activity, the number of hours engaged in termite-control work, general conditions, and various test values were examined regularly in eight workers at a termite-control office. The results are summarized as follows. 1. The plasma cholinesterase level was within the normal range from October 1986 until April 1987 in all workers, but started decreasing after May following the initiation of the full-scale termite-control season. It remained lower than the normal range (0.6 pH) from June until August in five of the six termite-control workers. The lowest level observed during this period was less than 50% of the mean value for each worker prior to the busy season in the six termite-control workers and was less than 10% of the pre-season values in three of them. In two workers, engaged mainly in sales, the plasma cholinesterase activity remained higher than in termite-control workers throughout the season. The lowest level in this minimally-exposed group during this period was not less than 50% of the mean value for each worker before the busy season. With the arrival of the off season, the level began to recover and returned to normal in all workers in January 1988. 2. The red cell cholinesterase activity remained within the normal range throughout the observation period, but it was generally low during the busy season from June to September and relatively high during the off season from December 1987 to January 1988. On the average, the red cell cholinesterase activity during the season was about 30% lower than that in the off season. 3. No marked subjective or objective abnormalities were seen in the workers. The results of other tests were generally normal, although a slight decrease in the red cell and white cell counts as well as abnormalities in serum lipid and lipase were noted in some workers. Further observations are necessary. 4. A significant negative correlation was noted between the number of hours engaged in termite-control work and variations in the plasma cholinesterase activity.(ABSTRACT TRUNCATED AT 400 WORDS)