The success of the stream monitoring program can best be evaluated
by re-addressing the main objectives alluded to earlier. The data
presented indicates that of the eleven streams which were intensively
monitored, nine were found to contain amounts of herbicide ranging from
less than 1.0 ppb to 12.0 ppb of 2,4-D and less than 1.0 ppb to 5.0 ppb
of 2,4,5-TP (Silvex), at some point within a 72-hour period (Table 4).
This seems to clearly indicate t. at if aerial application of herbicides
is to become a common practice, the chances of these herbicides ulti-~

seers or "

mately entering the stream system is approximately 70%. Hopkins and

Se gg ARR sweet tet 4 teem Pati ohm a mae Net

Howard (1971) found that in the aerial application of herbicides, the

loss to the atmosphere ranges from 20 to 80%, and Norris (1967) stated

that 60 to 75% of 2,4,5-T applied as low volatile esters in diesel oi}
in one study never reached the ground. If, as various studies have
sugges ted up to 80% loss of herbicide occurs, then the drift of these
airborne particles away from target areas couTtd lead to direct depo-
sition onto waterbodies. “It seems that from the results given by
various researchers, and from the data collected during the monitoring

program, the potential of nontarget organisms being exposed to aerially

applied chemicals is considerably high. If this is the case and it

Lecomes an accepted "fact of life" in the use of herbicide sprays,
y

then there should at least be some limits established as to how much
herbicide residue can be found in the streams and still be tolerated.
To go a step further, any amounts above these set values should be

justification Tor cancellation of the spray program. In other words,
restrictive regulations should be conscientiously enforced and. should
also be rigid enough to minimize problems which arise as a result of

variabilities encountered in individual jud-ement. Telford (1971) made

12