Ultralow volume application of organophosphate concentrate in grain terminals: a new occupational health hazard.

The introduction of ultralow volume (ULV) application of the organophosphate pesticide Fenitrothion in grain terminals presents a risk to workers of skin contact with concentrate. Blood testing, by the Ellman method, of a group of five grain terminal workers working on grain treatment showed a lowering of mean red blood cell cholinesterase (RBC ChE) activity to 23 units/gm Hb (normal value 28-40) with a range of 16-29. The probable cause was identified as percutaneous absorption of Fenitrothion concentrate by workers using ungloved hands to clean blocked drip feed nozzles. Modification of work practices was followed by a rise of mean RBC ChE to 33.6 units/gm Hb (range 32-36) during the following grain treatment season. RBC ChE activity measured during the intervening winter season--that is, a non-exposure period--showed a mean of 33.3 units/gm Hb (range 23-40).