Toxicology of Parathion


upon cholinesterase levels of the body is due to the fact that a
person ordinarily will not show symptoms of poisoning until the
cholinesterase levels have been markedly reduced. However,
there was some evidence during the 1950 spray season, when
studies of cholinesterase were made on a number of poisoned
individuals, to indicate that there is not always a severe lowering
of the blood levels of cholinesterase before symptoms occur (25).


A Canopy for a Tractor


 Fig. 4.-A removable canopy will minimize the spray drift hazard. This can
be used in most groves. (See Prosser et al., A Protective Canopy for Tractor
Drivers, Fla. Ag. Expt. Sta. Cir. S-29.)

 Cholinesterase is normally present in both red blood cells and
the plasma or the fluid fraction of the blood. Experimental work
has indicated that the amount of cholinesterase in the red blood
cells is relatively commensurate with that in other tissues in the
body (6, 11). Thus, if the amount of cholinesterase in the red
blood cells is decreased due to parathion absorption, it may be
assumed that cholinesterase has been lowered in other tissues in
the body, but this effect will vary somewhat from one tissue to
another.