Vol. 15—1961 - NorthEastern Weed Science Society

D. TASTEAND ODORSTUDIES
Taste and odor threshold studies have been conducted on
the herbicide formulations as such. These studies show that the
ester, acid and amine formulations have higher odor and taste
thresholds than the corresponding free phenol counterparts.
However, since it already has been shown that free phenols are
not the end breakdown products of formulations after exposure to
bacterial action, additional studies were conducted on the component
parts of these formulations.
The odor threshold of Esteron* 245 O.S. herbicide is about
0.3 ppb and the taste threshold is about 1.3 ppb. These figures
are very low, but are not due to the 2,4,5-T ester but rather to
the oil used in formulation. This oil is typical of that used
commonly in agricultural sprays and is believed to be readily
oxidized (decomposed) by soil bacteria, as we shall see later.
Further, the odor threshold of the 2,4,5-T propylene glycol
butyl ether ester (PGBE) is about 0.4 ppm. In other words,
about 1,300 times more of the ester is required to cause odor
than the oil alone. A similar figure gives as great a margin
of safety for taste threshold for 2,4,5-T PGBEester.
E. INFLUENCEOF OIL COMPONENTS
Since analysis of the components of various phenoxy ester
formulations has shown that the oil fractions can cause offtaste
and odor, what factors can minimize possible watershed
contamination? First of all, oils can be altered naturally in
many ways. Bacterial action is known to act rapidly on aromatic
oils (13). Ludzack and Kinkead (6) reported biochemical oxidation
of motor oils by organisms found abundantly in nature and
they showed that the principal end product of oil oxidation is
C02. This conclusion had also been reached earlier by Ruchhoft
and associate workers (10). To substantiate this fact, oil
components of the herbicide formulations were also run through
the laboratory apparatus in experiments similar to those described
above. Bacterial decomposition readily and completely
oxidized the aromatic oils to C02.
Volatilization of aromatic oils is well known (7).
Undoubtedly, adsorption to and chemical reaction with soil
particles does occur and would further enhance rapid breakdown
of oil constituents.
Another aid. in decreasing the possibility of watershed
contamination by oils would be by the use of herbicide formulations
that do not contain oils. Amine salt formulations do not
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* Trademark of The Dow Chemical Company.