Florida Agricultural Experiment Stations


 A test for the amount of cholinesterase present in the blood
 thus affords a rough means of determining the extent of para-
 thion absorption. The test is not infallible, but it is an excellent
 tool to be used in the diagnosis of parathion poisoning, to be
 used in pre-employment examinations to determine whether a
 man might be particularly susceptible to parathion, or to be used
 to indicate whether a man has recovered from a previous illness
 and is again fit for a job where parathion exposure will be in-
 volved. All of the phosphates which have been investigated do
 not have the same identical effects upon the reduction of blood
 cholinesterase and upon its return to normal levels after exposure
 to the insecticide has been stopped, but the pattern is similar.
 Plasma cholinesterase is rapidly destroyed in the presence of
 a phosphatic insecticide such as parathion, but return to normal
 levels is also rapid. If plasma cholinesterase be reduced 75
 percent it may return to normal within a matter of 7 to 10 days.
 Red blood cell cholinesterase will be destroyed more slowly than
 the plasma fraction and similarly it is replaced more slowly. It
 is replaced at the rate at which new red cells are formed, and
 thus it returns toward normality at the rate of about 1 percent
 per day (6, 9, 10). The cholinesterase of the brain and muscles
 is also replaced slowly and three months may be required after
 inactivation by di-isopropyl fluorophosphate before normal ac-
 tivity returns. This curve of regeneration for these tissues is
 parabolic. Thus, the rate during the first few weeks is rapid,
 but it slows considerably after that time. Generally, there will
 be a 50 percent recovery in the first few weeks (5, 14, 18) and it
 may take six to eight weeks for the other 50 percent.
 Cholinesterase is apparently manufactured by the liver and
the production of plasma cholinesterase is greatly diminished by
liver damage (10, 23). Thus, any disease which results in im-
proper liver function could result in a failure to maintain high
cholinesterase levels. This suggests the rather obvious con-
clusion that a person suffering from liver malfunction should
not be exposed to the hazards of handling parathion or similar
phosphatic materials. At least one case of parathion poisoning
has been reported (25) where the man was suffering with liver
disease.

 Symptoms of Parathion Poisoning
 When parathion poisoning occurs, rather well defined symp-
toms are present. These may be divided into three separate