LOW PARAQUAT INHALATION EXPOSURE FOR APPLICATORS SPRAYING PROPERLY WITH KNAPSACKS

Four field experiments of knapsack applications with paraquat mixtures , some with oxyfluorfen, in plantain (Musa acuminata x M. balbisiana A AB) were conducted to evaluate paraquat inhalation exposure from mist for applicators, and to reduce the amount of inhalation. The first and second experiments used four adjuvant variables and four nozzle varia bles, respectively, with products which claimed to reduce mist. In all the analyses of applicators' respirators, paraquat was below the limi t of detection (less than 0.018 mg per respirator). As a check on this low level, two more experiments comparing two nozzles to spray paraqu at, plus a standard adjuvant, were conducted under slightly different field conditions. Each applicator wore his respirator to spray three p lots, instead of only one as before, to give a total exposure of 55.5 L per respirator. Analyses again showed paraquat below the detection l imit of 0.025 mi of spray per respirator, thus indicating that less th an 0.018 mg of paraquat ion reached the inhalation zone from nozzles h eld 1 m below. On the basis of less than 0.018 mg of paraquat per resp irator detected in these last two experiments, the inhalation exposure was less than 0.020 mg/m(3). This level of paraquat inhalation exposu re per applicator is well below 0.10 mg/m(3), the listed limit of the National Institute for Occupational Safety and Health (NIOSH). The sta ndard analytical procedure for paraquat di cation was used with a few modifications, the main one was to filter extracts from used respirato rs to remove microparliculates. Background absorbance before color rea gent addition also had to be measured for subtracting from the absorba nce with reagent, thus allowing detection down to 0.018 mg of the para quat di-cation.