SENSORY
CHEMICAL PESTICIDE
WARNING SYSTEM
EXPERIMENTAL, SUMMARY
AND RECOMMENDATIONS
JULY 1976
LIBRARY
\L S- ENVIROKMtarAl PROTECTION
0KQN, tt. ). Otttf
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PESTICIDE PROGRAMS
WASHINGTON, D.C. 20460
EPA-540/9-75-029
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This report has been reviewed by the Office of Pesticide
Programs, Criteria and Evaluation Division, EPA, and approved
for publication as received from the contractor without edit-
orial changes. Approval does not signify that the contents
necessarily reflect the views and policies of the Environmen-
tal Protection Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation
for use.
For sale by National Technical Information Service, 5285 Port Royal Road,
Springfield, Virginia 22161
Limited copies are available from EPA Forms and Publications Center,
M-D-41, Research Triangle Park, North Carolina 27711
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EPA-540/9-75-029
SENSORY CHEMICAL PESTICIDE
WARNING SYSTEM
Experimental, Summary
and Recommendations
By Donald E. Johnson,
Leon M. Adams, John D. Millar
EPA Project Officer
Gunter Zweig, Ph.D.
Criteria and Evaluation Division
Office of Pesticide Programs
Final report covering the period
June 1974-July 1975
Prepared under Contract No. 68-01-2480
by
Southwest Research Institute
San Antonio, Texas 78284
U.S. Environmental -Protection Agency
Office of Pesticide Programs
Washington, D.C. 20460
July 1976
LIBRARY
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TABLE OF CONTENTS
Page
List of Tables iv
List of Figures v
I. INTRODUCTION 1
II. SUMMARY, CONCLUSIONS, AND
RECOMMENDATIONS 5
A. Odor Agents 5
B, Visual Agents 7
C. Warning Systems 7
D. Blue-Sky Portion 8
E. Additional Information Derived
from the Program 9
III. LITERATURE SEARCHES 10
IV. SELECTION OF ODOR AGENTS 15
V. SELECTION OF VISUAL AGENTS £2
VI. LABORATORY DISAPPEARANCE TESTS 27
A. Pesticides 27
B. Visual Agents 38
C. Odor Agents 47
VII. OUTDOOR DISAPPEARANCE TESTS 52
A. Methyl Parathion 52
B. Azinphosmethyl (Guthion 2L) 60
C. Carbofuran (Furadan 4 Flowable) 65
D. Limited Field Test 66
E. Other Investigators' Disappearance
Data 76
VIII. BLUE-SKY EFFORT 82
REFERENCES 90
ill
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LIST OF TABLES
Page
IV. 1. Candidate Odor Agents 18
2. Odor Perception Thresholds for
Some Typical Odoriferous Compounds 21
V. 1. Candidate Visual Agents 24
VI. 1. Disappearance of Fluorescing Agents 40
2. Disappearance of Fluorescing Agents 41
3. Disappearance of Fluorescing Agents
Mixed with Guthion 42
4. Quenching Studies of Pesticides in
Toluene 43
5. Disappearance of Fluorescing Agents
with and without Simultaneous
Application of Methyl Parathion E-4 45
6. Candidate Odor Agents Subjected to
Screening Tests 48
7. Odor in Polymers 50
VII. 1. Results of Test 1 55
2a. Results with Methyl Parathion and
Sensory Agents on Plants in Test 2 57
2b. Results with Sensory Agents on Glass
Plates and in Plastic Films in Test 2 58
3. Methyl Parathion Analytical Data
From Field Test (Cotton Plants) 71
4. Observations Made on Sensory Items
During Field Test 73
5. Results of Panel Evaluation of Sensory
Warning Devices 75
6. Disappearance Data for Methyl
Parathion (E-4) 77
7. Disappearance Data for Azinphosmethyl
(Guthion 2L) 79
8. Disappearance Data for Carbofuran
(Furadan 4 Flowable) 80
IV
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LIST OF FIGURES
Page
VI. 1. Disappearance of Methyl Parathion
from Glass Plates 31
2. Disappearance of Furadan from
Glass Plates 32
3. Disappearance of Guthion from Glass
Plates 33
4. The Separation of Methyl Paraoxon
and Methyl Parathion 34
VII. 1. The Disappearance of Methyl
Parathion from Euonymus Plants 59
2. The Disappearance of Guthion from
Euonymus Plants 62
3. The Disappearance of Furadan from
Euonymus Plants 67
4. The Disappearance of Methyl Parathion
from Cotton Leaves and Glass Plates 72
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I. INTRODUCTION
The period qovered by this report is June 13, 1974 through
July 12, 1975.
The main purpose of this program was to develop a warning
system which would alert individuals against premature reentry into
areas treated with organophosphate and carbamate pesticides.
Restrictions on the use of persistent organochlorine insecticides
have led to increased use of organophosphate and carbamate insecticides
as substitutes. Many of these substitutes are highly toxic substances,
manifesting their toxicity through inhibition of cholinesterase which
permits the accumulation of acetylcholine to reach toxic levels. Thus,
the danger in the use of certain organophosphate and carbamate insecticides
is inherent f Conditions for their safe use must be determined, and rules
which assure that safe conditions prevail during use must be implemented.
The segment of the population of the United States which could
conceivably be involved with these pesticides is large. An estimated 4.5
million persons are regularly employed in farm work, but twice that
number may be engaged in some form of agriculture in the course of a
year's time. The states of North Carolina, California, and Texas have
c
great numbers of seasonal workers, many of whom move from field to
field without establishing a permanent home in the areas where they are
likely to be exposed to the pesticides. The three crops which probably use
the largest amounts of these pesticides are cotton, citrus and tobacco.
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Citrus fruit pickers are the highest risk group. Following are tobacco
leaf pickers and handlers and "scouts, " who enter cotton fields counting
insects for the purpose of determining when an application of pesticide is
required. Although no fatal poisonings have resulted from premature
reentry, hundreds of cases varying from severe to slight in degree have
been documented, especially in California. In view of this experience,
minimum field reentry safety intervals have been set by law by the
Environmental Protection Agency. Laws have been enacted in California
which are even more stringent than EPA requirements. Facts indicate
that the proper safe interval in one area or for one crop may not be
suitable in another area or for another crop. Several factors influence
the persistence and the threat of the dislodgeab^e residues. The two
most important probably are quantity of pesticide applied and the
atmospheric conditions prevailing after application. Wet weather tends
to shorten the reentry safety interval, and cold weather tends to lengthen
the interval.
Danger in the use of drganophosphates and carbamates might be
reduced substantially if a warning system were in effect in a treated area
during the time that the pesticide residue remains at a health-threatening
level. The work undertaken was directed toward the development of a
warning system based on the incorporation, or simultaneous but separate
1. "Occupational Exposure to Pesticides, •" Report to the Federal Working
Group on Pest Management from the Task Group on Occupational Exposure
to Pesticides, Washington, D. C. , January, 1974.
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application, with the pesticide spray of chemical agents which were
odoriferous or visible. Ideally, these agents would have volatility
characteristics such that when they were no longer detectable, either
by smell or sight, the level of residual insecticide would be low
enough to permit safe reentry. Other desirable characteristics of the
agents would be low toxicity and low cost. In addition to this approach,
provision was made in the program to consider alternative approaches
in an uninhibited fashion known as a blue-sky effort.
The three insecticides involved in this program were methyl
parathion, carbofuran, and azinphosmethyl. These were chosen because
they are in wide use, are substitute chemicals, representative of their
chemical types, and have vapor pressures which are spread more than
one order of magnitude, thus covering the range of vapor pressures of
many of those pesticides commonly used in the United States.
By mutual agreement between representatives of the Criteria
and Evaluation Division, EPA, and Southwest Research Institute, the first
three months of the program were devoted almost exclusively to searching
of the literature and the generation of experimental approaches, so that
decisions could be made at the end of the first quarter as to the nature
of the experimental program to be pursued in the remainder of the
contract period.
The second, third, and fourth quarters were almost exclusively
devoted to experimental work, although some literature searching and
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studying were required throughout the program for the purposes of
guidance and evaluation.
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II. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
A. Odor Agents
The literature search did not reveal any odoriferous analogs
of the pesticides of interest. By logical reasoning, these compounds, if
they exist, offer the best chances of having physical and chemical
properties similar to the pesticides. Compounds with unusually high
boiling points tend to evoke milder odor responses in humans than many
lower boiling compounds. It was necessary to compromise and trade
off the desired high boiling point for increased odor intensity. In order
to compensate for the too rapid volatilization of the more intensely
odoriferous compounds, a means of retarding the evaporation of the odor
compounds had to be employed. The odor agents chosen for work in
this program finally were skatole, p-phenylethylphenylacetate, and
2 -phenylethanol.
The design of our study was such that the disappearance times
of the pesticides and odor agents (as well as visual agents) were determined
under laboratory climatic conditions and for at least two different
temperatures outdoors. The tests were designed to evaluate different
sensory agents rather than to test one with varying climatic conditions.
Final development of any sensory system for reentry purposes should
be thoroughly tested under a wide variety of climatic situations.
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The disappearance time for methyl parathion was matched quite
well with the proper concentrations of the first two of these substances
and not so well with the latter one. These substances, and probably
most other useful odorant compounds, tend to tail off so that the end
point as determined by human sniffing is not sharply defined. The
disappearance times of Guthion and carbofuran were not well matched,
generally.
Although the quantitative aspects of sensory odor agents are not
as precise as desired, they do have a distinct advantage in that they are
easily recognized by the general population. Even young children can be
instructed to associate smell with danger and that they should avoid the
area if the smell can be discerned. Some thought was given to the
incorporation of odor agents in the insecticide formulation as an aid in
preventing reuse of the formulation containers. This idea probably has
to be rejected because of cost considerations and the difficulties and
cost which might be encountered in getting government approval of adding
a new chemical to the formulation. In this program, attempts were made
to develop sensory agents which would assist in preventing premature
reentry into sprayed fields by farmers and field workers and also less
knowledgeable people such as young children. This program has
clearly demonstrated that for pesticides with vapor pressures similar
to methyl parathion, odor systems are feasible and provide a reasonable
definition of the times when it is safe to reenter sprayed fields. For
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pesticides like carbofuran and Guthion, the development of useful systems
requires more work but it does appear feasible.
B. Visual Agents
The visual agents of importance to the program were polycyclic,
aromatic hydrocarbons which fluoresce under ultraviolet irradiation.
The compounds offering the best potential to this program were anthracene
and phenanthrene. The disappearance of these substances, when used in
properly selected quantities, matched the disappearance of methyl
parathion quite well but not the disappearance times of Guthion and
carbofuran. The end points of the visual agents tend to be sharper and
more easily read than the end points of the odor agents.
The visual agents provide a more accurate end point because
people have less variation in their sense of vision than they do for odors.
These agents must be exposed to UV light in order to reveal their
fluorescence. This requires more knowledge and special equipment
on the part of the user, and, thus, it would be less useful for the
general population. This program has demonstrated that for pesticides
with vapor pressures similar to methyl parathion a relatively accurate
visual system can be perfected. Additional feasibility studies are needed
to evaluate visual agents for pesticides like carbofuran and Guthion.
C. Warning Systems
No distinct preference between the visual sensory item and the
unpleasant sensory item was established by the opinion survey.
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Similarly, no distinct preference for one of these two systems was
established experimentally in tests involving methyl parathion. Only
through additional experience could, perhaps, a distinct preference
for either device become apparent.
Warning systems, both visual and odor, can probably be
developed successfully for methyl parathion. With respect to the
conceptualized methods for warning systems given in Part 2, Method 1
(skatole incorporated into methyl parathion formulation) is unacceptably
expensive. Method 2 (skatole in perimeter signs) is less costly than
Method 3 (anthracene or phenanthrene in perimeter signs). However,
the deciding factor on which of these methods is best for general use is
probably not a cost factor but, rather, which system evokes human
response in the most effective and reliable manner. Both methods,
from a cost standpoint, are acceptable for use in the cotton-growing
regions where cost of application of methyl parathion is in the lower
part of the range given. Probably neither would be acceptable in the
higher part of the cost range given. (For cost analysis, see Part 2
of this report. )
D. Blue-Sky Portion
Ideas generated in this effort were not examined experimentally,
except for a few which were tested to a minor extent. Although some
of the proposed concepts were technically possible, none were sufficiently
promising to warrant additional experimentation.
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E. Additional Information Derived from the Program
The program developed some valuable adjunct information,
especially disappearance times for all 3 pesticides in the laboratory
and the field. The disappearance data for methyl parathion are within
the span of data of other investigators. The disappearance times found
in this program for Guthion and carbofuran are substantially longer
than those found by other investigators.
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III. LITERATURE SEARCHES
The literature search conducted in the first quarter of the
program was initiated with the foremost objective being to ascertain
whether or not odoriferous compounds were known among the analogs
and derivatives of the pesticides of interest. Logical reasoning
suggested that the best chances for finding compounds having physical
and chemical properties similar to the pesticides lay in searching
closely related families. Such compounds were especially attractive
because they might have disappearance rates close to those of the
pesticides. Computerized searches for these compounds were made
through the following facilities:
CHEMCON
DOD Technical Searching Facility
NASA Scientific & Technical Information Facility
EPA Abstract Search Center at Research Triangle
The principal key words and the modifiers used in these searches
are as follows:
Name of pesticide/analogs or derivatives-odor
smell, odoriferous;
organophosphates-odor, smell, odoriferous;
pesticides or Insecticides-odor, smell, odoriferous.
Insertion of the modifiers "odor", "smell", or "odoriferous" always
resulted in'zero citations available for printout. These negative results
offer the options for believing that there are no such compounds or, if
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11
such compounds exist, their odoriferous characters are not cited as
key pieces of information.
Extensive manual searching of the literature was carried out
for both odor and visual agents. This search was broadened so as to
no longer exclude any organic chemical family, as was done in the
computerized searching. Chemical Abstracts was the prime search
source. The volumes searched and the major search categories are
shown below. The modifiers used to restrict these major categories
are not shown because they vary with the category and were applied at
the judgment of the index reviewer, keeping in mind the objectives of
the search.
Chemical Abstracts 1947-56
Major search categories:
organic compounds
aroma
odor, odorous substances, olfaction
pesticides
insecticides
luminescent, luminescence
fluorescence, fluorescent substances
phosphorescence
phosphoric acid
thiophosphoric acid
phosphorothioic acid
phosphorodithioc acid
Chemical Abstracts 1957-61
Major search categories:
same as for 1947-56, plus perfumes
and N-methyl, -dimethyl, -ethyl, and -diethyl
carbamic acid
N-methyl, -dimethyl, -ethyl, and -diethyl
dithiocarbamic acid
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12
Chemical Abstracts 1962-73
Major search categories:
organic compounds
odor, odorous substances, olfaction
perfumes
pesticides
insecticides
fluorescence, fluorescent substances
phosphorescence
Starting with the 1962 volume of Chemical Abstracts, the
categories which were omitted from the earlier search lists were
dropped from the search because of the voluminous entries, even when
quite restrictive modifiers were applied, and the doubtful payoff
experienced in searching these categories in the preceding period,
1957-61.
The actual number of abstracts which received cursory review
is unknown. The number of abstracts which were copied and came
under close scrutiny was between 700-800. Of these, approximately 50
of the corresponding primary references were obtained for study.
Approximately 100 abstracts contained useful information on an "as is"
basis. One primary reference is a French patent concerning an
insecticide preparation containing a phosphorescent material •which is
reputedly active so long as an effective amount of insecticide remains
available at the exposure site. The phosphorescent material is not
2. Michel, R. H. R. , No. 1, 441, 972 (Cl.AOln) June 10, 1966.
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identified in the patent. One of the abstracts of interest "as is" dealt
with a Russian report of unsuccessful attempts to mark seed disinfectants
(3)
with a strong and long-lasting odor material or with permanent dyes.
In addition, a variety of reference works and books in the library
of Southwest Research Institute were searched.
Contact with the Institute of Gas Technology (IGT) in Chicago
resulted in the information that the gas trade currently uses dimethyl-
sulfide, C, and C> mercaptans, and tetrahydrothiophene as odorants.
Cc mercaptan has been used in the past but has caused problems by
condensing in transmission lines and fell into disfavor. IGT forwarded
a private research report containing some information about their search
for non-sulfur-containing compounds which they have considered as
alternative odorants for natural gas. This report contained a variety
of compounds and their odor thresholds, but most of the information had
already been obtained from other sources.
During the program, questions were raised regarding the possible
carcinogenic activity of the polynuclear hydrocarbons being used as
fluorescing agents. Although such activity appears to be nil for the two
(4)(5)
compounds of most interest ultimately, the desirability of having
acceptable substitute agents from chemical families beyond any shadow
3. Chemical Abstracts, 72, 89170n (1970) Kulikov, A.I. , et al, Byull,
Vses. Nauch. -Issled. Inst. Zashch. Rast. , 1969 (3) 15-17.
4. Steiner, P. E. , Cancer Research, 15, 632-635 (1955).
5. Salaman, M. H. and Roe, R. J. C., Brit. J. Cancer, 10, 363-378 (1956).
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14
of suspicion is obvious. Toward this end, another effort was made to
find such compounds in the literature. However, it appears that the
most effective fluorescing agents are in the polynuclear hydrocarbon
groups.
The only other organized search effort was for the purpose of
accumulating data of other investigators relative to the disappearance of
the pesticides of interest after field application. These data are used
in a subsequent report section in comparison with the disappearance
data generated in this program.
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IV. SELECTION OF ODOR AGENTS
Selection of candidate odor materials involved the factual and
theoretical considerations mentioned in the following paragraphs.
The volatilities of the pesticides, as shown below, were thought
to be of first importance:
Vapor Pressure, Concentration in
20°C, Saturated Vapor,
Pesticide mm Hg ZO°C, ppb
5(6)
Methyl parathion 0.97x10 ^ 12.8
Carbofuran 0.46 x 10'^ 10.
Guthion 2. 2 x 10"7 0. 03
Note: #Extrapolated value vased on vapor
pressure data at higher temperatures
supplied by manufacturer.
Requirements for ideal odorants were envisioned as follows:
1. Vapor pressures of the odorous substances should be
close to the vapor pressures shown above for the three pesticides.
2. Molecular weights should not exceed 300 and, preferably,
should be below 250. This requirement is based on the observation
by Stolr that no odorous substance is known with a molecular
weight above 300 and that the limit of perception, for many
people, begins around 250.
3. Odor perception thresholds should be below the
saturated vapor concentrations shown above for the three
6. Melnikov, N. N. , "Residue Reviews, " _3_6, Gunther & Gunther, Eds.,
Springer-Verlag, N. Y. (1971).
7. Stoll, M. , "Molecular Structure and Organoleptic Quality," Soc. of
Chem. Ind. Monograph No. 1, The Macmillan Co. , N. Y. (1957).
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16
pesticides. Preferably, the thresholds should be much below
these values since the atmosphere sniffed in actual field conditions
would never be saturated.
4. Chemical characteristics should be similar to the
three pesticides since the rate of disappearance is thought
to be the sum of losses from evaporation, hydrolysis, water
solubility, photolysis, absorption, microbiological action,
oxidation, isomerization, and other. Evaporation from surface
deposits is thought to be a major route of disappearance for
. . , (8)
many pesticides.
5. The materials should be relatively nontoxic originally
and after they degrade.
6. Odors of the agents should evoke a sharp human response.
7. The agents should not leave toxic residues.
The literature search did not reveal any candidate odor compounds
from the same chemical families as the pesticides. Although the
pesticides of interest were noted to have appreciable odors themselves,
discussions with representatives of the manufacturers (Monsanto Company,
Chemagro Division of Baychem Corporation, and the Agri-Chem Division
of the FMC Corporation) disclosed that the odors present were probably
from low molecular weight, volatile compounds present as impurities.
8. Spencer, W. F. , .eta.1, Pesticide Volatilization, "Residue Reviews,"
49, Gunther & Gunther, Eds. , Springer-Verlag, N. Y. (1973).
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In the case of methyl parathion, methyl mercaptan is released by
hydrolysis of the thioester isomer which forms from the parent
compound at a slow rate at room conditions. Attempts to take advantage
of this phenomenon to attain the objectives of this program are
described elsewhere in this report.
At this point in the selection process, with the theoretically most
promising chemical categories having been eliminated, attention was
turned toward compiling a list of odoriferous compounds, with emphasis
on those boiling above 275 °C and having, or estimated as having, low
odor thresholds. The compounds are given in Table IV-1. During the
time that Table IV-1 was being compiled, the following firms were
contacted for suggestions for compounds to be included in. the list of
candidates:
International Flavors and Fragrances, Inc. (U.S.)
Givaudan Corporation
S. B. Penick and Company
Chemessence, Inc.
J. Manheimer, Inc.
Evans Chemetics, Inc.
Fritzsche, Dodge & Olcott, Inc.
Petro-Tex Chemical Corp.
None of the contacted firms could suggest any outstandingly odoriferous
compounds boiling above 300 °C, except in the musk family. Four of the
companies expressed an interest in the problem and sent samples for
evaluation.
While a number of very odoriferous substances are listed in
Table IV-1, only some members of the musk family, benzyl salicylate,
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TABLE IV-1. CANDIDATE ODOR AGENTS
18
Boiling
Compound
artificial musk, 1-tertbutyl-
3-methyl-2, 4, 6-trinitrobenzene
typical synthetic macrocyclic
musk, 1 1-oxahexadecanolide
musk ambiette
musk xylene
musk ketone
mu scone-active principle in
natural musk, 3-methylcyclo-
pentadecanone
civetone, 9-cycloheptadecen-l-
one
2-hexyl-3-methoxypyrazine
2-isopropyl-3-methoxypyrazine
2-isobutyl-3-methoxypyrazine
2-propyl- 3-methoxypyrazine
alpha-ionone, beta-ionone
vanillin
ethyl vanillin
deca-trans, trans-2, 4-dienal
2-methox ynaphthalene
coumarin
methyl coumarin
methyl anthranilate
1, 7, 7-trimethylbicyclo [4.4.0]-
decan-3-one
1,7, 7-trimethylbicyclo [4.4.0]-
decan-3-formate
decan-3-acetate
decan-3-propionate
decan-3-butyrate
decan-3-acrylate
Mol.
Wt.
283
256
268
297
294
238
250
194
152
166
152
192
152
166
152
158
146
161
151
195
224
238
252
266
250
t,°C
m.96-7
m.35
25
25
25
328
130
342
159
-
-
-
-
127
81
250
285
170
25
-
272
298
139
305
135
87
85
90
100
115
86
PI-,
mm Hg
-
-
2.5 X ID'5
1 X 10'5
2.4 X 10-«
760
0.5
742
2
-
-
-
-
12
1
760
atm.
15
1.7 X ID'4
-
atm.
atm.
5
760
15
0.001
0.01
0.01
0.02
0.05
0.01
Odor Thresh.,
ppb (v/v)(l°)
0.001
-
-
-
-
-
o.ooidi)
0.002
0.002
0.006
0.013
0.016
-
0.070(]2)
0.12
0.28
-
0.65
-
-
-
-
-
_
Odor Character
like natural musk
like natural musk
like natural musk
like natural musk
like natural musk
natural musk
disgustingly obnoxious, becoming
pleasant in extreme dilutions
like fresh bell pepper
like fresh bell pepper
like fresh bell pepper
like fresh bell pepper
like cedar wood in strong dilutions
like violets in extreme dilutions.
like vanilla
like vanilla
like fried chicken
like old nerolin
like vanilla
like vanilla
like concord grapes
can be used in perfumes
can be used in perfumes
can be used in perfumes
can be used in perfumes
can be used in perfumes
can be used in perfumes
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TABLE IV-I. CANDIDATE ODOR AGENTS (Cont'd)
Boiling Point^)
Compound
Mol.
Wt.
t,°C
pr.,
mm Hg
Odor Thresh.,
Odor Character
alpha-(2-hydroxycyclohexylmethyl)
butytolactone
alpha-(4-hydroxycyclohexylmethyl)
196
203
butytolactone
l-(phenylethoxy)adamantane
gamma-decalactone
gamma-undecalactone
gamma-dodecalactone
benzophenone
(3-phenylethyl phenylacetate
benzyl cinnamate
hexyl cinnamic aldehyde
benzyl benzoate
benzyl salicylate
o-bromophenol
alpha and beta-santalol
196
256
170
184
198
182
240
238
216
212
228
170
220
203
176
281
286
170
305
324
350
305
323
368
194
302
3
1
atm.
atm.
11
760
760
760
760
760
760
760
760
0.001
like peppermint
like peppermint
can be used in perfumes
like peach
like peach
like peach
rose-hyacinth
sweet odor of balsam
faint, pleasant, aromatic
pleasant
unpleasant
like sandalwood
Note: Compounds for which no odor threshold data are presently available were included in the above list on the basis of actu-
al or estimated high boiling points and indicated odorous character.
9. Appel, L., Am. Perfumer Cosmet., 79, 25-39 (1964).
10. Dravnieks, A., Report No. IITRI-C8140-1, IIT Research Institute Technology Center, Chicago, Illinois, March 10,1969.
11. Seifert, R. M., et al, J. Agr. Food Chem. , 18, 246-249 (1970).
12. Buttery, R. G., et al, J. Agr Food Chem., 17, 1322-1327 (1969).
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and benzyl cinnamate have vapor pressures which approach those of
the pesticides. On this basis alone, these compounds appeared to be
the best candidates for inclusion in the pesticide formulations for
application simultaneously with the pesticides and over the identical
area. If application of the signal odorant were to be in some manner
other than by inclusion in the pesticide formulation and by a means which
retarded its normal evaporation rate, then numerous other odoriferous
compounds, including ones not listed, might be potentially useful.
For example, vanillin, ethyl vanillin, coumarin, methyl coumarin,
and gamma dodecalactone appeared to be in this category.
Odor perception thresholds for some typical odoriferous compounds
are presented in Table IV-2 for the purpose of comparison with those of
the odor agent candidates which are given in Table IV-1.
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TABLE IV-2. ODOR PERCEPTION THRESHOLDS FOR
SOME TYPICAL ODORIFEROUS COMPOUNDS
(for purposes of comparison with odor agent candidates)
Compound Odor Threshold ppb (v/v)
hydrogen sulfide 1 to 5
methyl mercaptan 1 to 8
n-butyl mercaptan 0.5
butyric acid 0.4
crotonaldehyde 34
pyridine 10 to 12
p-toluidine 3.1
eugenol 3.5
methyl salicylate 0.6
skatole 0.3
p-chlorophenol 0.2
-------
22
V. SELECTION OF VISUAL AGENTS
There are many compounds which exhibit some degree of
photoluminescence. The potential use of inorganic phosphors, dyes,
and nonvolatile luminescent substances is treated in the blue-sky section
of this report. This section is concerned with the search for organic
compounds which exhibit some form of photoluminescence and have
normal boiling points similar to those estimated for the pesticides of
interest. Availability of photoactive compounds having normal boiling
points matching those of the pesticides was, of course, no guarantee that
such compounds would have vapor pressures matching the pesticides at
the usual laboratory and field temperatures. However, since vapor
pressure data at ambient temperatures are not available for most of
these materials, most of which are solids at ambient temperatures, no
better criteria for potential usefulness were known than matching the
normal boiling points.
The search for such compounds in the journal literature was
difficult and not as productive as had been hoped for. Journal articles
treating photoluminescent phenomena are not often concerned with the
vapor pressures of the compounds under study. Books, reference works,
and contacts with industrial firms were more helpful sources of information.
The field of fabric brighteners seemed very attractive, initially.
However, as information was obtained, it became apparent that most
of the compounds employed were of exceedingly low volatility or had
-------
23
insufficient stability when subjected to prolonged, intense sunlight.
Companies which were contacted in this regard are:
American Cyanamid Company
CLba-Geigy, Inc.
Crompton and Knowles Corp.
American Hoechst Corp.
United States Radium Corp.
Hercules, Inc.
A few samples were received from these organizations for experimental
evaluation.
Some attention was given to natural substances which fade
or darken under sunlight. An example of this category would be carotene,
which fades. However, such action is a function of time and seems to
be no better than a timepiece.
Table V-l is a listing of candidate visual agents which span the
boiling point range of interest. Most of these were taken from chemistry
handbooks and other books, although one journal article was outstandingly
useful, and at least two more helpful. The compounds selected
for screening first were: trans-stilbene, anthracene, carbazole, tri-
phenylmethane, 2, 5-diphenyloxazole, fluoranthene, 9-phenylanthracene,
o, o1 -quaterphenyl, and 1, 2 , 7-trihydroxyanthraquinone.
The possibility of using the photoluminescent character of the
pesticides themselves was considered but did not appear promising.
Guthion and carbofuran exhibit some phosphorescence, barely in the
13. Furst, M. , et al, J. Chem. Physics, 26, 1321-1332 (1957).
14. Kirkbright, G. F. , et al, Anal. 'Chim. Acta. 5Z_, 237-246 (1970).
15. Williams, R. T. , J. Roy. Inst. Chem.. 83, 611-626(1959).
-------
24
TABLE V-l. CANDID ATE VISUAL AGENTS
Compound Boiling Point, °C
trans-stilbene
anthracene
phenanthrene
acridine
alpha-benzylnaphthalene
para-benzylnaphthalene
1,4-diphenylbutadiene
4-methoxybenzophenone
carbazole
triphenylmethane
2,5 -diphenyloxazole
1,1,2,2-tetraphenylethane
2-hydroxybenzothiazole
diphenylurethane
triphenyl phosphite
quinazolinone
benzimidazole
1,2-benzophenazine
l,l'-binaphthyl
1,3,5-trinitronaphthalene
l-naphthyl-2-tolyl ketone
m-terphenyl
diphenylene disulfide
phenothiazine
thioxanthone
fluoranthene
p-terphenyl
305 (720 mm Hg)
340
340
345-6
350
350
350 (720 mm Hg)
354-5
355
358-9
360
360
360
360
360
360
360
360
360+
364 (explodes)
365
365
366
371
372
375
376
-------
25
TABLE V-l. CANDIDATE VISUAL AGENTS (Cont'd)
Compound Boiling Point, °C
anthraquinone 377
diphenylsulfone 379
melene 380
triphenylmethanol 380
retene 390
pyrene 393
N-benzylsuccinimide 395
4,4'-dibromobenzophenone 395
4,4'-ditolylsulfone 405 (714 mm Hg)
1,2-benzofluorene 413
9-phenylanthracene 417
o,o'-quaterphenyl 420
tetraphenylethylene 420
triphenylene 425
9,10-benzophenanthrene 425
1,2-dihydroxyanthraquinone 430
tetraphenylmethane 431
1,2,-benzanthracene 435
1,8-dinitronaphthalene 445 (decomposes)
chrysene 448
2,2-binaphthyl 452
1,3,5-triphenylbenzene 459 (717 mm Hg)
1,2,6-trihydroxyanthraquinone 459
1,2,7-trihydroxyanthraquinone 462
11,12-benzofluoranthene 480
picene 519
-------
26
visible range, but methyl parathion does not. However, the p-nitrophenol
produced upon hydrolysis of methyl parathion does phosphoresce in the
(16)
visible range, although inadequately for the purpose of this program.
16. Moye, H. A. , and Winefordner, J. D. , J. Agr. Food Chem. , 13,
516-518 (1965).
-------
27
VI. LABORATORY DISAPPEARANCE TESTS
In these tests, the objective was to develop sensory systems (odor
and visual) which would match the disappearance rates of three pesticides.
Ideally these rates would match under variable weather conditions of temp-
erature, wind speed, humidity, and rainfall. The intent of the program is
to provide a sensory system which will indicate when the pesticide is at a
level which will allow safe reentry into the field. Stated in another way,
the systems will warn individuals not to enter as long as the sensory agent
is detectable. The "safe" level of pesticide (on plants) which has been
used for the studies reported herein is when 90% of the original level has
dissipated. This is an arbitrary value used in lieu of more definitive data.
The actual residue levels of different pesticides on plants, soils, etc.
which are considered safe for reentry are being developed under other
EPA programs. The sensory agents developed under this contract should
be sufficiently adaptable so that by minor changes of delivery system they
will meet the safe levels when established.
A. Pesticides
1. From Glass Plates
In order to follow the disappearance of the pesticides, an
analytical capability of adequate sensitivity was established using a gas
chromatograph equipped with a flame ionization detector. No interferences
were experienced in the detection and measurement of the target pesticides
or their degradation products.
-------
28
Carbofuran was found to chromatograph satisfactorily
on a 20-inch, 1/8-inch diameter SS tube packed with 10% UC-W98
(methyl silicone gum containing 1% vinyl) on Chromosorb WAW-DMCS
(80-100 mesh) at an oven temperature of 150 C. A short column
(20-inch) was used to reduce the times required for analyses and to
minimize the exposure of carbofuran to high temperature. Carbofuran
has been found difficult to chromatograph directly, but the conditions
given in this paragraph produced good, reproducible instrument
response to this pesticide. Other conditions are: carrier gas flow -
30 ml/min. ; H? flow = 30 ml/min. ; CU flow = 240 ml/min. ; injection
port temperature = 200 C, and detector temperature - 200°C. Methyl
parathion was analyzed on the same column at the conditions above
except an oven temperature of 160°C was preferable. Guthion was also
chromatographed on this column but at temperatures of 250°C for the
injection port and detector and 200°C for the oven. Retention times for
the three pesticides are as follows: methyl parathion - 8. 5 min. at 160 ,
12.7 min. at 150°; carbofuran -6.6 min. at 150°; Guthion - 14.7 min.
at 200°.
The first disappearance work encountered the problem of
uneven distribution of the substance under study. A dilute solution of a
substance in a volatile solvent does not deposit the substance uniformly
if permitted to evaporate unmolested on a flat surface. Uneven
distribution, of course, leads to unequal disappearance times for the
-------
29
areas of relatively heavy and light deposits. Miniature spray devices
(e.g. DeVilbiss, No. 15, modified) were found difficult to control when
spraying the small areas needed in the studies, and the stray spray
droplets required safety precautions which were burdensome.
Eventually, a system was developed which visually gave a
fairly uniform distribution of pesticides and sensory agents on glass
plates which were then exposed to controlled conditions in the laboratory.
A four-inch frosted glass square was rotated on a turntable at 175 rpm
while a selected volume of agent or pesticide in solution in toluene was
applied to the center of the plate by means of 100-|oJ syringe. Perfect
reproduction of area covered and perfect uniformity of the deposit
were not achieved, but the system gave fair-to-good reproducibility
and was very useful. When the amount of solution deposited is 50
microliters, the area covered is approximately 30 cm . When all
factors involved except concentration are constant, then the amount of
substance deposited per cm becomes dependent upon the concentration
of substance in the solution.
In order to determine the amount of pesticide present on
the glass plates at the desired intervals after application, a plate was
rinsed with a stream of dichloromethane which was collected, as it
ran from the corner of the plate, in a small glass beaker. The rinse
was evaporated, without heating, under a stream of nitrogen to a
predesignated volume and compared with a standard solution by gas
chromatographic analysis.
-------
30
Working with pesticide formulations commonly used in
field applications, the rate of disappearance was determined for Methyl
Parathion E-4, Furadan 4 Flowable (carbofuran), and Guthion 2L
(azinphosmethyl). Disappearance was studied at a temperature of
23 C (73 F) with an air velocity over the exposed plates of 8 kph
(5 mph). Figures VI-1, VI-2, and VI-3 are plots of the replicate
amounts of pesticide remaining on the plates after the passage of
various intervals of time. Two levels of deposit of each pesticide
were applied in this work, 10 |j.g/cm (0.88 Ib/acre) and 5 |j.g/cm
(0.44 Ib/acre), simulating high and medium applications in the field.
At both levels of application, only about 3% of the methyl parathion
remained on the plate after 24 hours had passed. The high level
of Furadan showed about 20% remaining after 15 days and the medium
level about 3% remaining after 12 days. The high level of Guthion
showed about 60% remaining after 30 days with this dropping to around
12% after 60 days. The medium level of Guthion was not followed
beyond the 28-day mark, at which point about 20% remained.
In order to be certain that the chromatographic peak
representing methyl parathion is truly methyl parathion and not methyl
(17)
paraoxon, the latter was synthesized by the method of Lichtenstein, et alv '
and injected into the chromatograph. Figure VI-4 shows sufficient
separation between the methyl paraoxon and methyl parathion to prevent
17. Lichtenstein, E. P., et al, J. Agr. Food Chem. , 21, 416-424(1973).
-------
31
100
Temperature 23°C
A ir Velocity over Plates. . . 8 km per hr
2 (5 mph)
Methyl Parathion per crn->. -^ M-g
Methyl Parathion per cm .. 5 \±g
24
Time, hours
Figure VI-1. Disappearance of Methyl Parathion
from Glass Plates
-------
Q-
32
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-------
33
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-------
34
Methyl Paraoxon
Methyl ParathLon
Chroma tog raphed
at 150 C
J_
I
0 4 8
Time, minutes
Figure VI-4. The Separation of Methyl Paraoxon
and Methyl Parathion
-------
35
confusion of identities. Although this figure was constructed from
chromatography at 150 C, we have found that at our normal operating
o
temperature of 160 C the differential retention times for paraoxon (6.2
minutes) and parathion (8. 5 minutes) provide adequate resolution. Thus,
it is probable that the disappearance study of methyl parathion dealt
with the parent compound.
Furadan 4 Flowable, as received, is an aqueous suspension
of the pesticide and insoluble, finely divided solid. In order to conduct
the disappearance study mentioned above, it was necessary to extract
the Furadan from the aqueous suspension with toluene so that it could be
applied in the same manner as the Methyl Parathion E-4 and Guthion 2L.
Of course, the extract did not contain the finely divided solid which, if
it served as a good adsorbent, could affect the rate of disappearance of
the Furadan. This effect would likely reduce the rate of disappearance
of the Furadan, resulting in a longer staying time than that determined
in this experiment.
The lack of precision and inconsistencies in the data in
Figure VI-2 and VI-3 require some comment. These imperfections are
thought to be the result of three factors: (1) the difficulty in obtaining
uniform distribution of the pesticide on the plants, as mentioned earlier;
(2) changes in analytical sensitivity which occasionally occurred in an
unpredictable pattern, decreasing precision obtained despite the frequent
-------
36
use of standards. The source of this difficulty was tentatively identified
as resulting from the accumulation of deposits of unknown materials in
the injection port, for example, possibly the emulsifiers in the pesticide
formulation. Cleaning the injection port after every ten injections was found
to lessen the problem; (3) This factor applies to Figure VI-3 only. The
more rapid rate of loss of Guthion in the second 30-day period versus
the first 30-day period could possibly be explained by temperature change
brought on by failure of the laboratory air conditioning system. Repairs
could not be effected until several days had passed. Nevertheless, the
data procured in these tests were sufficiently accurate to allow continuation
of the work of matching pesticide disappearance times with those of odor
and visual agents.
2. From Soil
Two soil types were used: (1) a dark brown silty clay
(Lewisville silty clay) and, (2) a tan sandy loan (Venus clay loam). The
large lumps were crushed, and then the soil was sieved to provide a
fraction with particles ranging from 0. 5 to 2.4 mm. This fraction was
exposed in a 1/4-inch layer to an atmosphere at 50% relative humidity and
o o
a temperature of 24 C (75 F) for a period of 3 days, or more, before use.
Forty grams of soil were placed in petri dish (area = 63. 6 cm),
and 318fjtg of methyl parathion was applied in 2 ml of aqueous spray
emulsion, a volume of just the right amount to wet the surface of the soil
2
sample thoroughly. The application rate of methyl parathion was 5 fjig/cm
(0.44 Ib/acre).
-------
37
Methyl parathion was recovered from the soil
samples by placing the soil on filter paper in a Buchner funnel and
washing 5 times with approximately 30-ml portions of acetone. Suction
was applied briefly to strip the acetone from the soil after each
application of acetone. The filtrate, amounting to about 150 ml, was
evaporated to a known volume of less than 5 ml, placed in a small vial,
and shaken with enough NaCl to cause any water present to separate
from the acetone. The amount of methyl parathion recovered was
estimated from injections into the gas chromatograph of the sample
solution, a standard solution, and a soil blank solution. Average
recovery from the brown silty clay was 75% and from the tan sandy
clay loam was 61.5%. The brown soil was also spiked with methyl
paraoxon, and a recovery of 69.5% was obtained.
The spiked soil samples were placed in a laboratory hood
in an air current of about 8 km/hr (5 mph) and at a temperature of
approximately 23 °C (73° F). Recovery of the methyl parathion was
made periodically. The loss of methyl parathion from the brown soil
amounted to about 25% during the first day of exposure, and the residue
remained essentially unchanged through the next 16 days. The loss of
methyl parathion from the tan soil amounted to about 10% during the first
day of exposure, and the residue remained essentially unchanged through
the next 8 days.
At the end of 30 days, the loss from the tan soil amounted
to 27%. The loss from the brown soil was not determined after the
-------
38
16-day loss point. The chroma tog rams of the spiked samples of both
soils, after 8 days of exposure, showed small peaks which have an
elution time coincident with methyl paraoxon. This peak is about the
same size after 16 days of exposure of the brown soil and, also, after
30 days of exposure of the tan soil.
The leveling off of the loss of methyl parathion may result
from strong adsorption of the layer of molecules resting on the soil and
the diffusion limited access of molecules from the recesses to the outside
layer or surface where evaporation occurs. Perhaps, then, decomposition
of the adsorbed molecules does not occur owing to the low water content
of the soil and a consequent lack of microorganism action.
B. Visual Agents
Of the f luorescing substances named in this portion of the report,
(4)
only chrysene appears to be carcinogenic. Steiner has reported this
substance to be a weak carcinogen. On the basis of this information, no
further work was conducted with chrysene after the screening tests on
glass plates.
1. From Glass Plates
The same technique used to apply the pesticides for
disappearance determinations was used to apply fluorescing chemicals
for disappearance tests. The same conditions of temperature and air
velocity used in the pesticide work prevailed in the fluorescence studies.
The visual agents were detected by 2 or more individuals observing the
plates under short wave (254 nm) ultraviolet light. The objective of the
-------
39
study was to develop agents which were to be detected by sensory means.
All of the laboratory and field tests were conducted using observers
(for both visual and odor agents) rather than using some type of chemical
or instrumental method. Prospective fluorescent agents were first
screened at an application level of 10 |o.g/cm (0.88 Ib/acre) (see Table VI-1),
but an additional two levels were added in an effort to develop information
more quickly relating disappearance time and level of application. This
work is summarized in Table VI-2. The information contained in these
two tables and in Figures VI-1, VI-2, and VI-3 served as the basic data
from which to proceed in matching disappearance times of pesticide and
fluorescing substance.
In the course of the first experiments conducted in which
Guthion was mixed with a fluorescing substance, it was observed that two
out of six of the prospective visual agents were quenched by the
Guthion (see Table VI-3). These observations led to the hope that a
useful system employing the quenching phenomenon could be developed
rather quickly, perhaps. As a result of this thinking, combinations of
the three pesticides and four fluorescing substances were prepared and
applied to glass plates. The results are shown in Table VI-4. The most
consistent observation that was made is that the quenching effect
observed at or near the start of a test never changes, i.e. , the quenching
effect does not diminish appreciably with time and the fluorescent
property of the sensory agent does not return. The basis for this effect
is not understood, but quenching as a mechanism for employing a
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40
TABLE VI-1. DISAPPEARANCE OF FLUORESCING AGENTS
Visual Fluorescing Stiength*
Fluorescing Agent
Carbazole
Triphenylmethane
Trans-Stilbene
6-Methylcoumarin
Fluoranthene
Anthracene
2 ,5-Diphenyloxazole
Chrysene
Pyrene
o-Quaterphenyl
OHr
S
W
S
W-0
S
S
S
S
S
S
24 Hr
S
very W
W-0
0
S
S
S-M
S
S
S
48 Hr
S
0
0
-
W
S-M
W
S
S-M
S
72 Hr
S
-
-
-
W
W
W
S
S-M
S
96 Hr 120Hr 144 Hr
S S S
_
_ _ _
- - -
W 0 -
W W W
W 0
S S S
S-M W-0 0
S-M S-M S-M
*S—strong; M—moderate; W-weak; 0-none.
Note: Fluorescing agent applied at rate of 10 jug/cm2.
-------
41
TABLE VI-2. DISAPPEARANCE OF FLUORESCING AGENTS
Fluorescing
Agent
Chrysene
Chrysene
Chrysene
Carbazole
Carbazole
Carbazole
Fluoranthene
Fluoranthene
Fluoranthene
Anthracene
Anthracene
Anthracene
Phenanthrene
Phenanthrene
Phenanthrene
p-Terphenyl
p-Terphenyl
Application Rate,
Atg/cm2
10
1
0.1
10
1
0.1
10
1
0.1
10
1
0.1
10
1
0.1
10
1
0
s
s
M
S
S
M
S
S
VW
S
s
vw
s
M
VW
S
M
16
S
S
M
S
S
M
S
0
0
s
0
0
0
0
0
s
M
Visual Fluorescing Strength at Hours*
24 40 48 64 72 88 96
S S S S S S S
S S S S S S S
M M M - VW VW VW
s - st st st st st
S - 0 - -
Mo
\J
s st st st o
----- - -
----- - -
S S$ SJ SJ 0
----- - -
----- - -
----- - -
----- - -
----- - -
s s s s s s s
M M M M M M M
112 120
S S
S S
vw vw
st st
- -
- -
- -
- -
- -
- -
- -
_ _
- -
- -
- -
s s
w w
*S—strong, M—moderate, W—weak, VW—very weak, 0—none.
t Spotty, some left after 600 hours
tSpotty
-------
42
TABLE VI-3. DISAPPEARANCE OF FLUORESCING AGENTS
MIXED WITH GUTHION
Visual Fluorescing Strength*
Fluorescing Agent
Carbazole (1/2)
Anthracene (1/2)
Chrysene(l/2)
Pyrene (1/2)
Fluoranthene (1)
2,5-Diphenyloxazole (1) q q q q q
*S—strong; M-moderate; W—weak; 0-none; q—quenched.
Note: Fluorescing agent applied at same concentration as insecticide (1) or at half the concentration of the
insecticide (1/2) from solution containing both insecticide and fluorescing agent. Insecticide used was
Guthion 2L sprayable emulsion. Insecticide application rate = 10 ng/ctn2 (0.9 Ib/acre) of active ingredient.
OHr
S
S
S
q
s
24 Hr
S-M
W
S
q
S-M
48 Hr
S-M
very W
S
q
M
72 Hr
M
0
S
q
W
96 Hr
M-W
-
S
q
w
-------
43
TABLE VI-4. QUENCHING STUDIES OF PESTICIDES IN TOLUENE
Visual Appearance at Hours*
Application Rate,
Mg/cm2
Fluorescer
p-Terphenyl
p-Terphenyl
p-Terphenyl
Chrysene
Chrysene
Chrysene
Carbazole
Carbazole
Fluoranthene
Pesticide
E-4 Methyl parathion
Guthion
Furadan
E-4 Methyl parathion
Guthion
Furadan
E-4 Methyl parathion
E4 Methyl parathion
E-4 Methyl parathion
Fluorescer
0.5
0.5
0.5
0.5
0.5
0.5
0.5
5
10
Pesticide
5
5
5
5
5
5
5
5
10
0
q
q
si
si
q
s
q
s
qt
16
q
si
si
M
si
S
q
s
s
24
q
si
si
M
si
S
q
s
s
40
q
si
si
M
si
s
q
s
-
64
q
si
si
M
si
S
q
s
*q—quenched, si—slight, M—moderate, S—strong.
CuQuenched initially but strongly fluorescent in spots within 1 hr and virtually continuously covered with
fluorescence within 16 hrs.
-------
44
fluorescing agent does not appear promising, based on limited
compounds studied.
The possibility of matching disappearance times of
pesticide and fluorescer appeared to be greatest for a system involving
methyl parathion. For this reason, a number of tests were conducted
with methyl parathion and three promising fluorescing substances in
combination. The observations made in these tests are summarized in
Table VI-5. The reproducibility is certainly influenced by the uniformity
of the coating obtained, the texture of the frosted glass plate surface,
and by the size of the crystals formed as the toluene evaporates from the
solution applied to the plate. Also, the presence of methyl parathion on
the same plate as the fluorescer quenches fluoranthene and, in the case
of anthracene and phenanthrene, reduces the length of time of fluorescence
to some extent. This last effect can be offset by adding more fluorescing
substance to the mixture than is required when the fluorescing substance
alone is applied. The three fluorescing substances were judged useful at
the following application rates: anthracene, 2-3 jag/cm^ ; fluoranthene,
2-4 |j,g/cm ; and phenanthrene, 45-50 |j.g/cm . Fluoranthene apparently
cannot be combined with methyl parathion because of the quenching which
occurs at these low levels.
In addition to the above three fluorescing substances,
trans-stilbene was found to fluoresce for about 24 hours when applied at
a coverage of 10 |j,g/cm . This was of interest inasmuch as it also very
nearly matched the disappearance of methyl parathion. However, this
-------
45
TABLE VI-5. DISAPPEARANCE OF FLUORESCING AGENTS WITH AND WITHOUT
SIMULTANEOUS APPLICATION OF METHYL PARATHION E4
Fluorescing
Agent
Phenanthrene
Phenanthrene
Phenanthrene
Phenanthrene
Phenanthrene
Phenanthrene
Phenanthrene
Phenanthrene
Phenanthrene
Phenanthrene
Fluoranthene
Fluoranthene
Fluoranthene
Fluoranthene
Fluoranthene
Anthracene
Anthracene
Anthracene
Anthracene
Anthracene
Anthracene
Application
Rate,
jug/cm2
20.0
20.0
40.0
40.0
40.0
40.0
45.0
45.0
50.0
50.0
2.5
2.5
3.0
5.0
5.0
5.0
5.0
3.0
3.0
'2.0
2.0
Application Rate
of Methyl
Parathion E-4,
Mg/cm2
0
5
0
5
0
5
0
5
0
5
0
5
0
0
5
0
5
0
5
0
5
Visual Fluorescing Strength at Hours*
0
S
S
S
S
S
S
S
S-M
S
S
S
q
s
S
q
s
s
s
M
S
S
16
0
0
M
M
W
0
S
0
_
_
-
-
-
S
barely
visible
S
S
—
—
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-------
46
substance was reported by a manufacturer to be sensitive to UV
radiation, and preliminary tests in which exposure was made outdoors
indicated a much quicker loss of fluorescence than was observed indoors.
This is probably due to isomerization of the "trans" form to the inactive
"cis" form, brought about by the increased intensity of UV radiation
received in the outdoors exposure. It might be possible to increase the
residence time of the trans form to the useful range by increasing the
amount applied per unit area.
2. From Soil
Soil samples, identical with those in VI, A, 2, were sprayed
similarly with aqueous emulsions of anthracene. Compared to the
amounts required for foliage, 10 to 15 times as much anthracene was
required to give a satisfactory visual response, initially. This may be
the result of molecules penetrating the interstices of the soil where they
can neither receive nor emit light. However, the fluroescence lasted
less than 3 days. Amounts up to 50 times that which was effective on
foliage gave fluorescence for only 4 days. A similar observation was
made when carbazole, a long-lasting fluorescing substance in the
laboratory, was applied to the soil samples; the highest concentration
provided a strong to finally weak fluorescence for a 7-day period, and
weak fluorescence continued for an additional 7-day period.
The use of fluorescing agents on soil does not appear
promising because of the large quantities of fluorescing agents required
to give a satisfactory signal for significant periods of time.
-------
47
C. Odor Agents
1. From Glass Plates and Polymer Films
Various odorous substances (see Table VI-6) were applied
to the frosted glass plates by the same technique mentioned earlier to
deposit pesticides and/or fluorescent substances. The agents were
detected by 2 or more individuals sniffing the plates . The odorants
2
were applied at a coverage of 10 |j.g/cm (0.88 Ib/acre) and were exposed
to the same temperature and air velocity given earlier in this report.
None of the odorants tested in this manner gave much of a residual odor
after 24 hours of exposure to the test conditions.
One of the ways to increase residence times of the candidate
odorants is to add more of the substance per unit of area. By doubling
the amount added to 20 fig/cm (1.76 Ib/acre), the residence times of
vanillin and several musks, as examples, were increased to a 1- to 3-day
period.
Another approach to extending the residence time of a
substance is to mix it with a fixative. A variety of substances were mixed
with equal parts of mineral oil or Galaxolide (a synthetic musk by
International Flavors & Fragrances) without any substantial benefit being
realized, however.
A third approach followed to increase residence times was
to mix odorants and polymers in solution and then cast the solution in
thin films.
-------
48
TABLE VI-6.
CANDIDATE ODOR AGENTS SUBJECTED
TO SCREENING TESTS
Benzyl cinnamate
Benzyl salicylate
beta-Phenylethylphenylacetate
Coumarin
Ethyl vanillin
2 - Methoxynapthalene
Santalol
Methyl anthranilate
Ethyl anthranilate
Ethyl salicylate
Eugenol--USP--prime
Sandela
Musk ketone
Musk ambrette
Musk xylol
Heptaldehyde
2 - Phenylethanol
Pentadecanolide
Anisyl acetate
Terpineol
Laurine
Jasmonyl
Methyl eugenol
Geraniol
Anisyl alcohol
Acetanisole
Galaxolide (musk)
6 - Methylcoumarin
gamma-Dodecalactone
Skatole
alpha-choroacetophenone
alpha-bromoacetophenone
Dimethyl sulfide
Several proprietary perfume
oils and odor masking
agents.
-------
49
Some difficulties apparent in the development of an
odorant sensory system are these:
(1) The odor agents investigated thus far tend to
"tail off" in intensity without giving a sharp end point.
(Z) The known compounds of highest boiling points
and lowest odor thresholds tend to be mildly odoriferous
(e.g., the natural and synthetic musks) in character
rather than strongly odoriferous (e.g. hydrogen sulfide
and the mercaptans).
(3) Strongly odoriferous compounds, when applied by
themselves, do not have adequate residence times.
(4) Wide variation in the individual human response.
The best approach appeared to be a compromise in which
the desired high boiling point characteristic is traded off in favor of
increased odor intensity. Some odorants which fit this category and
were investigated are: menthol, eugenol, heptaldehyde, dimethyl
disulfide, skatole, alpha-chloroacetophenone (lachrymator), alpha-
bromoacetophenone (lachrymator), 2-phenylethanol, and some proprietary
perfume oil products. In order to use such substances, which are quite
volatile relative to the pesticides, especially Guthion and carbofuran,
the evaporation must be retarded in some manner such as may be
achieved through incorporation into polymer films (see Table VI-7), or
by some other device, which restricts the treated area being exposed to
evaporation. Mixing with polymers was the route followed with the
-------
50
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51
investigations involving Guthion and carbofuran. With methyl parathion,
adjusting the quantities of odorant applied to glass or paper strips or
incorporated into the spray formulation provided adequate variation in
the residence time.
2. From Soil
Soil samples as identified earlier in this report were also
sprayed with skatole emulsions. The quantity of skatole required to
evoke a satisfactory small response after 3 days of exposure is at least
two times that required for foliage. Three and 6 times the amount
required for foliage were found to provide an odor for 10 days and 21 days,
respectively.
The use of skatole on soil does not appear promising
because of the large quantity of the substance required to evoke a
satisfactory response for a significant period of time.
-------
52
VII. OUTDOOR DISAPPEARANCE TESTS
When the laboratory disappearance tests were complete,
disappearance tests were conducted outdoors using a small number of
plants. These tests were conducted to determine if the laboratory
matched sensory agents and pesticides would perform satisfactorily in
a less controlled environment and to investigate possible problems
which might be encountered in a limited field test planned later in the
program.
The plants used were Euonymus japonica (also called Aucuba
japonica, gold spot euonymus, and gold dust plant). This variety of
plant was chosen because it is readily available at the local nurseries,
is hardy, and has large leaves of a shape and texture that permit easy
sampling. The plants were sprayed at recommended coverage rates
given by the pesticide supplier for general use.
A. Methyl Parathion
The plants were sprayed outdoors with a compressed air sprayer
and were kept outdoors for periods of time ranging from 4 to 7 hours per
day. For the rest of the 24-hour period, the plants were placed in a
greenhouse to prevent damage by freezing during the night. Two tests
were conducted, each being of 3 days' duration, each using 3 plants.
Temperature extremes during the outside exposure periods ranged
from 4° to 24°C (40° to 76°F). Every day, except one, was sunny or
-------
53
partly cloudy. The relative humidity was generally low. Winds varied
from calm to 24 kph (15 mph). The greenhouse, where the plants were
kept most of the time, was maintained within the temperature range of
25° to 29° C (78° to 85 °F), with high relative humidity.
The methyl parathion formulation applied was procured from
the Thompson-Hayward Company and is labeled Methyl Parathion E-4
(four pounds per gallon). The directions on the label recommend use
from one-half to one pint per acre (one-quarter to one-half pound per
acre) in most applications. This is within the typical use range given
(6)
by Melnikov. The calculated deposit of methyl parathion applied
would be 5.0 |j.g/cm , assuming uniform coverage (or 0.44 Ib/acre).
However, the values found under our spraying conditions varied
considerably from the calculated value.
The sensory agents were incorporated into the spray, by
dissolving them in the E-4 formulation with additional solvent (toluene)
as required and additional wetting agent (Triton X-45) as required to
produce a satisfactory emulsion for spraying. Anthracene was applied
at 3 jig/cm (0.26 Ib/acre) and phenanthrene at 50 |j.g/cm2 (4.4 Ib/acre).
Skatole was applied at 15 |j,g/cm (1.32 Ib/acre in Test 1 and
10 |j,g/cm2 (0.88 Ib/acre) in Test 2.
The plants were sprayed to run off, and pools of liquid were
dislodged from the leaves by tilting the plants from the vertical position
and shaking gently. When the spray had dried, about 30 minutes later,
the first plant leaf sample was obtained, and this time was designated as
-------
54
zero time. At predesignated subsequent time intervals, leaf samples
were taken.
Leaf samples were analyzed for surface residues of methyl
parathion and visual agent (anthracene or phenanthrene) by rinsing the
leaves thoroughly with dichloromethane, concentrating the rinse under
nitrogen flow, and injecting an aliquot into a gas chromatograph.
Phenanthrene and anthracene chromatograph well under the same
conditions used for methyl parathion (given earlier in this report).
Retention times at 160° are 5.8 min. for phenanthrene and 6.1 min. for
anthracene. The area of the leaf sample was determined by tracing the
outline of the leaf on paper, then measuring the outlined area with a
planimeter. The presence of the visual agent on the plant was also
followed qualitatively by observing the plant, at sampling times, under
ultraviolet light in a darkened room. The presence of the odor agent
was determined by the sense of smell, using 2 to 7 human subjects.
Test 1 involved the E-4 methyl parathion formulation with
incorporated phenanthrene or skatole applied as sprays. The disappearance
times of methyl parathion and phenanthrene matched very well. The
residual odor of skatole was judged to be too strong when the methyl
parathion was essentially gone. The results of Test 1 are given in
Table VII-1.
In test 2, the E-4 methyl parathion formulation with incorporated
anthracene, or two-thirds of the amount of skatole used in Test 1» were
applied as sprays. The disappearance times of methyl parathion and
-------
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anthracene matched very well, and the matching of methyl parathion
with skatole was much better than in Test 1 and was considered
satisfactory.
Also in Test 2, anthracene, phenanthrene, skatole, eugenol,
and a-bromoacetophenone (a lachrymator) were applied to glass plates
which were exposed side by side with the plants. The eugenol and
a-bromoacetophenone were applied to the plates in solutions of
Ethocel (Dow ethylcellulose - 48 to 49.5% ethoxyl content - 10 cps.),
using doctor blade settings of 1 and/or 2 mils. The Ethocel was used
to reduce the volatility of these two odorants. The other agents applied
to the glass plates were in solution in toluene. Fairly good correlation
between the disappearance of the agents on the plates, as determined
by human response, and the disappearance of methyl parathion from the
plant, as determined analytically, was attained.
The results of Test 2 are given in Table VII-Za and 2b.
Figure VII-1 is the disappearance curve of methyl parathion
from the 6 test plants. Each point is based on the average of the amount
of methyl parathion found on one leaf from each of the plants at the times
indicated. The percentage of the initial dosage remaining at 72 hours
is 4.8. Although phenanthrene and anthracene were also determined by
gas chromatography, only one leaf from the sprayed plant was analyzed
at each time point, which was insufficient to give data smooth enough to
plot well owing to the lack of uniformity of the spray application. The
comments in Tables VII-1 and VII-2a and VII-Zb give a better depiction of the eye
response to the fluorescing plants.
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B . Azinphosmethyl (Guthion ZL)
The product used was Guthion 2L Emulsifiable Insecticide from
Chemagro Division, Baychem Corporation. Two plants were sprayed
O
as prescribed by the supplier for a coverage of 10 (jig/cm (0.88 Ib/acre)
and then shaken free of excess spray as in the methyl parathion tests.
The plants were kept outside continuously after spraying, since the
possibility of damage by freezing at night was slight. At night when
rain threatened, the plants were placed under a shelter which consisted
of a protective roof without sides.
Thus, the plants were sheltered from direct rainfall but exposed
to other atmospheric factors. The effect of a large amount of rainfall
directly on the plants was unknown, but it was suspected that it would
remove much of the Guthion. By shielding the plants, the disappearance
time obtained should be at a maximum with respect to the prevailing
other atmospheric factors. The plants were wetted often with condensed
moisture during foggy weather and when the dew point was reached.
During the 55-day test period, the following general statements about
the weather apply:
. Temperature extremes were 0.5° (33°F) and 32°C (90°F).
. Wind speeds were most often 16-40 kph (10-25 mph) with
occasionally gusty periods where the wind speed
reached as high as 75 kph (45 mph).
. The relative humidity was usually moderate; however,
extremes were experienced.
. Cloudy skies prevailed more than 50% of the time.
-------
61
Leaf samples were analyzed for Guthion using the same basic
procedure described in the methyl parathion tests, except that
rectangular leaf samples were cut from the whole leaves with scissors.
This was done so that the area of the sample could be determined by
measurements with a ruler rather than a planimeter,
The amounts of Guthion found on the leaves of the plants is as
follows for the 55 days of the test:
Elapsed time, days Guthion found, avg of 2 detns . ,
|j.g/cm2
0 13.1
1 13.9
5 11.2
12 8.3
19 7.0
28 5.4
35 4.0
55 4.0
These data are presented in graphical form in Figure VII-2,
2
with 13.5 jug/cm taken as the zero time amount. This value is the
average of the values for day 0 and day 1. Between 25 and 30% is
found to remain at the end of the test period.
At the same time that the plants were sprayed, glass plates on
which Ethocel films containing the fluroescing agents anthracene and
phenanthrene or the odor agent skatole had been laid down were exposed
side by side with the plants.
During the first few days of the test, fog and frequent dew point
conditions resulted in condensed water being deposited on the plants and
the plates, despite the use of the sheltering roof mentioned earlier.
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Skatole, being water-soluble, was leached from the plastic films so
that no odor remained after 5 days. The fluorescing agents, being
water insoluble, were not subject to leaching and continued to fluoresce.
However, all films, containing skatole or fluorescing agent, were
loosened from the glass plates, and large pieces of them were blown
away by the wind. This means of exposing the sensory agents for
prolonged periods to the outside environment was, at this point,
obviously unacceptable.
A new means of exposing the sensory agents was developed.
This consisted of dipping strips of filter paper and strips of glass fiber
filter medium in polymer solutions of fluorescing agents or odor agents,
dried to a tack-free state, then sprayed with a water repellent before
exposure alongside the plants under test. The strips were suspended
from wooden rods held by clamps to an ordinary laboratory support
stand. Anthracene and phenanthrene were again the fluorescing agents
tested. Carbazole, which had been found to be a promising long-lasting
fluorescing agent in the laboratory tests conducted earlier in the
program, had since been found to be unsuited for outdoor use.
P -Phenylethylphenylacetate and 2-phenylethanol were substituted for
the odor agent skatole. This was done because it had become increasingly
evident that skatole was not suitable for prolonged exposure outdoors
because of changes occurring in the basic odor or premature loss of
odor entirely, whereas the other two agents were apparently superior
in these respects. In addition to the Ethocel polymer, the copolymer
-------
64
Vinylite VYHH (Union Carbide copolymer of 86% vinyl chloride and
14% vinyl acetate) was put under test. The visual and odor agents
were dissolved in solutions of the two polymeric substances and applied
to the paper and glass substrates as indicated above. In all, 24 paper
strips and 24 glass strips were tested, representing the 4 test
substances at 3 different amounts on the 2 substrates.
Within 5 to 7 days, the anthracene treated strips were quite
yellow (especially the glass fiber ones) and fluoresced with a yellow
color under a UV lamp rather than the original purple-blue color.
Phenanthrene exhibited a similar but not identical change after about
two weeks of exposure. After 3 weeks of exposure, it was necessary to
prepare fresh strips to use as controls to determine whether or not the
exposed strips still fluoresced. It was found that the strips still
fluoresced at this point but with colors different from the original colors
as well as with lessened intensities. The changes in color and intensity
of fluorescence made the state of the strips difficult to assess, even with
the prepared control strips at hand, and the reading of the strips is
complicated to some extent by the inherent fluorescence of the substrate
materials. The test strips were exposed for a total of 40 days, but
there were essentially no changes observed after the 3-week point.
The odor strips retained their characteristic odors through
the first 3 weeks. At this point, the odor of the strips with the least
amount of odorant became undetectable to about half of the persons
sniffing them. The other strips, with the greater amounts, were
-------
65
regarded to be faint to strong, depending upon the individual sniffer.
The principal problem with this approach is that the end point is not
sharply defined. These strips were kept on test for 40 days also,
with the intensity of the odors weakening slowly. Most of the strips
containing the largest amounts of odorants were weakly odorous at the
end of the 40-day period.
C. Carbofuran (Furadan 4 Flowable)
The product used was Furadan 4 Flowable Insecticide manu-
factured by the Agri-Chem Division, FMC Corporation. Two plants
were sprayed to the dripping-wet state; then the excess was shaken free
as in the methyl parathion test. The intended coverage was 10 (j.g/cm
(0.88 Ib/acre); however, the actual amount found initially was much
higher for reasons unknown. It should be appreciated that large
variations are often encountered in amount deposited per unit area by
.spraying. These plants were exposed alongside of the plants sprayed
with Guthion 2L and the sensory agents described above. Therefore,
the comments made about the weather and the sensory agents apply also
to the test with Furadan 4 Flowable.
The amounts of Furadan found on the leaves of the plants is as
follows for the 55-day test:
-------
66
Elapsed time, days Furadan found, avg. of2detns.,
[j,g I cm ^
0 28.4
1 24.0
5 19.0
12 12.6
19 7.5
28 4.4
35 3.2
55 0.9
These data are presented in graphical form in Figure VII-3.
Between 3 and 4% is found to remain at the end of the test period.
D. Limited Field Test
A limited field test was conducted on a cotton farm near
Batesville, Texas. The cotton plants, in the early blooming stage,
were sprayed by airplane with methyl parathion at an intended dosage
of 17 (Jig/cm^ (1.5 Ib per acre) and Galecron at an intended dosage of
0 . 95 jag/cm (0. 083 Ib per acre). The main purpose of the test was to
follow the disappearances of the methyl parathion from the cotton
leaves and of visual and odor agents placed alongside the field. Leaf
samples were taken at 20 min. , 2, 4, 8, 22.5, and 48 hours after
application. Observations of the sensory agents were made at the 4, 8,
22.5 and 48-hour points.
Spraying was completed at approximately 8 A.M. At that time,
the wind was blowing at an estimated 30-40 kph (18.5 - 25 mph). During
that day and the remainder of the test period, the wind blew steadily
at that velocity, or slightly higher, with frequent gusts to 56 kph (35 mph),
-------
67
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except for the periods near dawn when the velocity dropped to the
8 to 16 kph (5-10 mph) range. The days were sunny with only scattered
light clouds. The temperature span during the test period was from
25.6° to 34.4°C (78° to 94°F). The relative humidity ranged from high
in the mornings to moderately low in the afternoons. No rainfall
occurred during the test period.
Prior to the spraying, a small table was erected approximately
150 meters into the field so that the table top was essentially at cotton
plant height. Twelve glass plates, 5x5 cm square, were fastened to
the table top by placing them on strips of tape having adhesive on both
sides. This was done so that the turbulent air streams from the
spraying airplane could not dislodge the plates from the table top. The
purpose of the plates was to collect spray for analysis and comparison
with leaf samples and the sensory agents on glass plates. After the
first samples were taken, the table top was removed from the supporting
legs and kept in the shade of the cotton plants. It had been found in
earlier preparatory tests that exposure in the shade more closely
matched the disappearance of a substance from a glass plate with the
disappearance of that same substance from a plant in the sun.
At the time that the table with the glass plates was set up,
10 cotton plants surrounding the table (none closer than 3 meters, none
farther away than 20 meters) were tagged with white cloth strips.
This was done so that sample leaves would always be taken from the
tagged plants or the ones on either side of them.
-------
69
After spraying was completed, sampling consisted of removal
of 2 of the glass plates and one canopy leaf from the windward side of
each of the designated plants (or the ones on either side of them). The
upper sides (exposed to the aerial spraying) of the plates were washed
thoroughly with a small stream of dichloromethane (DCM), and the
washings were collected in a single glass bottle for transport to the
laboratory for analysis. The leaves were placed on top of each other,
making a stack 10-high, on a polyethylene-covered board. A No. 15
laboratory cork borer was used to cut through the leaves, giving a
circular sample of each leaf of about 2 cm in diameter. This sample was
ejected from the borer into a glass beaker, and the process was repeated
2 times, with each set of leaf samples being put into a. different beaker.
Each set of 10 circles was washed 3 times with 15 ml of DCM, using a
small stainless steel spatula to make sure that agglomerates of leaf
circles were broken up and each circle contacted by the solvent. The
washings from each set of 10 circles were bottled in glass bottles and
transported to the laboratory for analysis.
At the laboratory, each bottle of DCM washings was reduced to
the'standard volume of 3 ml under a stream of nitrogen without heating.
Two |ol of the concentrate were injected into a gas chromatograph (GC)
equipped with a flame ionization detector and a column consisting of a
20-inch x 1/8-inch SS tube packed with 10% UC-W98 on Chromosorb
WAW-DMCS (80-100 mesh). The GC oven was kept at 160°C. Other
conditions were carrier gas flow, 30 ml/min.; H flow, 30 ml/min.;
-------
70
Op flow, 240 ml/miri. ; injection port temperature, 250°C; and detector
temperature, 250 C. The concentration of methyl parathion in each
sample was calculated from peak height measurements on the chromatograms
of the samples and a standard solution of methyl parathion. This value
was used to determine the amount of methyl parathion present on a
per-square-centimeter basis of upper leaf surface or upper plate
surface. Samples of leaves taken before spraying showed no detectable
interference on the chromatograms at the points of interest.
Results of analyses are shown in Table VII-3 and Figure VII-4.
The 3 values for leaf samples at each sampling time were averaged before
the disappearance curves in Figure VII-4 were constructed. Methyl
parathion disappeared more rapidly from the cotton leaves than from the
glass plates. At 24 and 48 hours, approximately 3% and 1%, respectively,
remained on the leaves, while about 14% and 4% remained on the plates
at those time points.
Just before the spraying commenced, 2 visual agents and 3
odor agents were put under test in a shaded area beside the cotton field.
The visual agents were anthracene and phenathrene. The odor agents
were skatole, 2-phenylethanol, and (3-phenylethylphenylacetate. The
visual agents were applied to frosted glass plates only. The odorant
skatole was applied to a frosted glass plate and to paper strips, also.
The other two odorants were applied only to paper strips. Table VII-4
gives the amounts or concentrations applied and the observations made
during the test by the two men conducting the test. Attempts were made
-------
71
TABLE V1I-3. METHYL PARATHION ANALYTICAL DATA FROM FIELD TEST (Cotton Plants)
Time After
Application
20 min
2hr
4hr
8hr
22.5 hr
48 hr
Sample
Plate No. 1
Leaf la
Ib
Ic
Leaf Avg.
Plate No. 2
Leaf 2a
2b
2c
Leaf Avg.
Plate No. 3
Leaf 3a
3b
3c
Leaf Avg.
Plate No. 4
Leaf 4a
4b
4c
Leaf Avg.
Plate No. 5
Leaf 5a
5b
5c
Leaf Avg.
Plate No. 6
Leaf 6 a
6b
6c
Leaf Avg.
Mg/cm2 *
8.50
7.22
12.74
6.02
8.66
7.93
7.93
5.72
6.72
6.79
3.97
5.52
4.01
5.62
5.05
2.73
1.77
2.38
1.38
1.84
1.20
0.33
0.14
0.29
0.25
0.36
0.05
0.10
0.10
0.08
Percent
Remainingt
97.7
97.3
91.1
76.3
45.6
56.7
31.4
20.7
13.8
2.8
4.1
0.9
*Based on area of one side of leaf sample only.
tBased on zero time amounts (obtained by extrapolation—see Figure VII-4) of 8.70 jig/cm2 for plates and 8.90
jig/cm2 for leaves.
-------
72
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TABLE VIM. OBSERVATIONS MADE ON SENSORY ITEMS
DURING BATESVILLE FIELD TEST
Cone,
jug/cm2
0
4
Time, hr
8 22.5
48
Anthracene
3
5
7.5
10
S
S
S
S
w
S
S
S
E
W E
S I,
S I2
E
E
Phenanthrene
40
50
60
S
S
S
w
w
w
E
E
E
Skatole (on plate)
40
S/W W/E
Cone,
g/e
0
Time, hr
4 8 22.5
48
Skatole (on paper)
6
9
12
24
1
3
6
9
S
S
S
S
S
S
S
S
S/W W/E E
S S/W E
S S W/E
S S M
2-Phenyle thanol
S S/W M
S S M
S S M
S S M
E
VW
VW
M
M
M
fi-Phenyle thy l-Pheny lace tate
1
3
6
9
S
S
S
S
S W/E E
(paper strip lost)
S S M
S S M
M
M
S — strong
M — moderate
W - weak
VW — very weak
E — extinct
Ii — irregular pattern, 90% of material gone
12 — irregular pattern, 75% of material gone
/ — gives individual responses when disagreement of the observers occurred
-------
74
to procure disinterested observers from the population in the vicinity,
but the remoteness of the field made such arrangements unworkable.
As a consequence, the opinions of 5 field workers on the sensory
items were collected at a different site.
The observations made by the two men conducting the test are
given in Table VII-4 in terms of whether or not a definite visual or
odor response was noted and the intensity of that response or signal.
It may be noted that disagreement occurred rather frequently between
the two men with regard to the odor evaluations. This disagreement
is noted in the table by slash lines, with each half showing an individual
response. Whatever time for safe reentry is chosen between the 8-hr
and 48-hr points in Figure VII-4, the time is matched or bracketed by
the anthracene quantities used. The phenanthrene quantities employed
are useful only at the 8-hr point. The skatole on the plate matches the
22.5-hr point fairly well. The concentrations of skatole on paper cover
the time span with about the same options as the anthracene. The
2-phenylethanol concentrations used were too strong and did not match
well. The lowest concentration of (3-phenylethylphenylacetate matches
the 8-hr point fairly well, and the next concentration would probably
have been in the useful range but this remains a speculation since the
test paper was blown away by the strong wind.
The responses received in the opinion survey are given in
Table VII-5. Some of the panel did not detect the fluorescent light
source immediately, and many indicated that the light source was dim
-------
75
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76
and not easily noticed. All recognized the color of the light source.
Most of the panel said that a warning was indicated. Concerning the
unpleasant smelling device (skatole), all of the panel detected a smell,
and most indicated that the smell was strong. All said that the smell
was easily noticed, and most said that a warning was indicated.
Relative to the pleasant smelling device (2-phenylethanol), all of the
panel detected a smell and most indicated the smell was weak. Most
said the smell was not easily noticed and approximately one-half said
that a warning was indicated. Virtually none of the panel preferred the
pleasant smelling device (2-phenylethanol). The panel was evenly
distributed between preferring the unpleasant smelling device (skatole)
and the visual device. All indicated that the unpleasant smelling device
(skatole) would be useful and effective for the protection of children.
E. Other Investigators' Disappearance Data
A literature search was conducted to find outdoor disappearance
data of other investigators for the 3 pesticides of concern in this
program. The information obtained is presented in Tables VII-6, VII-7,
and VII-8. Variations in weather conditions, quantity applied, plant
species involved, length of tests, and analytical procedures make exact
comparisons impossible. For this reason, appropriate information
and data other than disappearance figures have been extracted from the
journal'articles and are included in the tables to help in the evaluation of
-------
77
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the disappearance figures. The length of time after application is given
at the top of each table. This time point was chosen so as to
accommodate the maximum number of references. In this program,
the amount of methyl parathion remaining 3 days after application was
4.8% of the amount applied on the euonymus plants and less than 1% on
the cotton plants. Extremes found in the literature for the same time
period were 23% and 1.1%. In a similar comparison, but for a 4-day
period, 86% of the azinphosmethyl was found on the plants in this
program, whereas the high and low figures from the literature were
46% and 16.7%. For carbofuran, the comparison had to be made after
14 days had passed. In this program, 39% was found to remain. Only
one value could be found in the literature, and it was less than 0.4%.
In this program, azinphosmethyl and carbofuran were found
to disappear much more slowly than other investigators have found.
However, the disappearance rates from plants outdoors were not out
of line with the disappearance rates from glass plates in a laboratory
environment. The disappearance rates of methyl parathion from plants,
as determined in this program, are substantially in the span of the
data -of others.
Since carbofuran has most frequently been applied to soil rather
than to plant foliage, only one reference was found which had data
suitable for comparison with the data generated in this program. Another
interesting reference on ca.rbofuran gives the half-life in soil, under
(29)
field conditions, as ranging from 46 to 117 days.
29. Caro, J.H., et. al. , J. Agr. Food Chem., 21, 1010-1015 (1973).
-------
82
VIII. BLUE-SKY EFFORT
Several meetings were held with groups of Institute personnel
to discuss the problem of time of safe reentry into fields which had
been sprayed with toxic pesticides named in this report. Present in the
various groups were chemists, physicists, plant physiologists, and
engineers. It was explained that, although low cost, simple devices
were desired, the discussions were not to be limited by these factors,
as the ideas were to be screened later. It is possible that, during the
screening process, new and simple practical ideas might be developed
from the more complicated and less practical suggestions. The following
suggestions were made.
1. As the pesticides under consideration are cholinesterase
inhibitors, it should be possible to develop a nonspecific test for the
pesticides which would relate to the actual residual pesticide activity.
An article, entitled "Test for Anticholinesterase Materials in Water",
(30)
published by Ganison, _et al, describes such a test. The test involves
a color development by uninhibited cholinesterase. In the presence of
pesticides, inhibition of the enzyme occurs, and there is no color
development. A rapid and continuous system for monitoring organo-
phosphates in water has been developed by Dr. Louis H. Goodson of
Midwest Research Institute. This system is based upon the determination
of the activity of an immobilized enzyme in an electrochemical cell.
30. Ganison, R.M., et_. al_. , Environ. Sci. Technol.. 7, 1137-1140
(1973).
-------
83
It could possibly be adapted to make a fairly simple piece of inexpensive
test equipment for spot tests.
2. A cursory check of the literature indicates that it may be
possible to develop simple color tests for some of the pesticides.
Further search of the literature and some experimental work may confirm
this.
3. The ability of methyl parathion and parathion to isomerize
to compounds which hydrolyze readily might be used to detect these
compounds. Heating of methyl parathion to 100°C rapidly isomerizes
it to a product which hydrolyzes readily to form methylmercaptan which
could be easily detected by its odor. A similar reaction occurs with
parathion and might occur with Guthion. The equipment required for
such a test would be simple, inexpensive, and readily available. Ae
mercaptans have low odor thresholds, the test should be capable of
detecting small quantities of the pesticides, although the quantities
encountered in use conditions might require concentrating to reach the
level of perception.
4. The use of small retroreflective glass beads offer a.
possibility as an indicator for safe reentry into a sprayed field. The
retroreflective characteristics of these beads are usually very low or
nonexistent when wetted with a liquid. The pesticide might act as such
a material, and the retroreflective characteristics return on loss of the
pesticide. A good flashlight would be the only equipment required.
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5. When dyes are in solution, they frequently exhibit a color
which differs from that of the solid dye. This principle might be used
as an indicator for the presence or absence of the pesticide.
6. The fluorescence and phosphorescence of some materials
can be quenched by the addition of certain materials. If the pesticide
has this quenching property with some light emitting materials, a
system could be devised for indicating the absence of pesticide. It would
be rather simple to experimentally check a number of light emitting
compounds with the pesticides.
7. A chemiluminescent system in which one of the reactants
has the desired rate of disappearance could be used as an indicator for
the disappearance of the pesticide from foliage. This reactant could be
coated on the foliage with or without the pesticide. In determining if
any of the reactant remains, the other component or components of the
system could be sprayed on the foliage periodically. When all of the
indicator reactant has disappeared, a chemiluminescent reaction would
no longer take place, and no light would be emitted.
8. If contaminated air from the sprayed field is passed through
a cage containing insects which are sensitive to the pesticide under
consideration, the death rate or number of insects killed could be used
as an indication of pesticide concentration. Tests such as this are
generally not sufficiently reproducible or sufficiently rapid to be of value.
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9. A test similar to that suggested in 8., but use contaminated
foliage in place of contaminated air.
10. If the fluorescence of the pesticide is sufficiently strong,
this property could be utilized to indicate concentration.
11. A laser could be utilized as a strong, concentrated light
source. Either fluorescence or light absorption could be utilized to
determine presence or absence of pesticide. This type of equipment
would be relatively expensive and complicated.
12. Convert the thio-com pounds to hydrogen sulfide which could
be identified by odor or lead acetate test paper. This conversion would
require equipment considered too complicated and expensive for general
field application.
13. Use insect attractants (bug lights or chemicals) to attract
insects into the area and determine kill. This would be difficult to
reproduce, as it would depend upon the concentration and type of insects
found in the area.
14. React thio-compounds with copper and determine sulfide
formation by reflectance or color change.
15. The pesticide molecules could be activated with a laser beam
and the Raman spectra determined. The Materials Research Center of
the Allied Chemical Corporation has developed such a remote gas analysis
system. Measurements can be made in the kilometer range. However,
this equipment is bulky and expensive.
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16. The laser beam could be used to volatilize the pesticide
from the foliage and the concentration of pesticide measured. Such
a treatment would undoubtedly destroy the foliage and interfere with
the analysis.
17. The conductivity of solutions formed by passing air through
a solvent may be a measure of the pesticide concentration. In a similar
manner, the conductivity of solutions formed by washing the foliage in
a solvent, preferably one with a low solvent power for inorganic
materials could be utilized. Disadvantage of such a test is the presence
of interfering materials in the environment.
18. The adaptation of infrared photography would be useful in
surveying pesticide concentration from an airplane or helicopter.
19. Adaptation of the infrared sniperscope to examine the
sprayed foliage would be useful for determining concentration of pesticide.
20. Same as 19, but use ultraviolet light.
21. A condensation nuclei detector in conjunction with a chromato-
graphic column could be used. This method would be expensive.
22. As the flame photometric detector is selective for sulfur
and phosphorus, it may be possible to adapt it to a device for detecting
pesticides containing these elements without the use of a chromatographic
r
column. The equipment would be expensive and would require a hydrogen
and oxygen source.
23. If enzymes that emit odor from substrates are sensitive to
pesticides, they could be adapted to detection of pesticides.
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24. Changes in conductivity of the surface of semi-conductors
might be useful as this method is capable of detecting extremely small
quantities of material. The disadvantage of this method is its lack of
selectivity.
25. The contaminated foliage could be fed to a rabbit which
would be observed for neurological changes indicating toxicity. Trained
personnel would be required for such a test.
26. Samples could be pyrolyzed and the products analyzed with
a coulometric detector. Equipment would be relatively expensive and
complicated.
27. It was suggested that the action of atropine in the treatment
of phosphate ester poisoning be determined and adapted to pesticide
determination if possible. Information given in a medical book indicates
that this is not possible.
28. As a method of sampling, a nonabsorbent tape would be
stretched across a portion of the field prior to spraying. After spraying,
the tape could be reeled in slowly or periodically for examination by a
suitable detection system.
It was suggested that the first 7 ideas be considered for further
checking for feasibility and the feasible ones be considered for development,
It was the consensus of all personnel questioned that, as there are
too many factors affecting the concentration of pesticide in air and as the
concentration of the pesticide in air is so low, adaptation of the various
ideas to foliage examination would be more practical than air examination.
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A small amount of experimental work was done attempting to
utilize the phenomenon of heat isomerization of methyl parathion to the
thio ester with subsequent hydrolysis to yield methyl mercaptan.
Heating of small quantities of methyl parathion to 160-180°C in an air
atmosphere in a test tube permits oxidation to the oxygen analog, and
no methyl mercaptan is obtained on hydrolysis. If this procedure is to
be successfully applied, relatively sophisticated equipment for heating
and cooling the pesticide in an inert atmosphere would have had to be
developed. Avoidance of sophisticated equipment was one of the objectives
of this program. It was noted that on hydrolysis of either the unheated
or heated and oxidized parathion, the p-nitrophenol formed gives a light
yellow color to the alkaline hydrolysate. On acidification, the yellow
color disappears.
Small amounts of experimental work were also done in other areas.
(31)
Sawicki, et.al. reported 4-(p-nitrobenzyl)-pyridine to be a sensitive
reagent for the determination of alkylating agents. The work done at
SwRI indicates this reagent offers some promise for determining the
presence of residual methyl parathion at levels down to 1 p.g. By using
several leaf washings and concentrating the washings, if necessary, this
test is thought to offer some promise in determining methyl parathion at
the low levels of interest.
Attempts to quench small retroreflective beads with pesticides,
as mentioned in suggestion 4, above, were without success. Similarly,
31. Sawicki, E., et. al., Anal. Chem., 35, 1479-1486 (1963).
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inorganic phosphors, dyes, and other nonvolatile luminescent substances
were not quenched by the pesticides and no useful way to use their
luminescent properties was devised.
(32)
A literature notation that the 3-keto derivative of carbofuran
fluoresced in an intensely blue manner suggested that maybe this compound
could be synthesized by a simple oxidative procedure under field conditions.
However, neither hydrogen peroxide, bis (4-t-butylcyclohexyl)
peroxydicarbonate, diisopropylbenzene hydroperoxide, nor NaOCl produced
positive results. The literature method of producing this compound by
prolonged heating with chromium trioxide in glacial acetic acid was not
effective when the reaction time was reduced to a few minutes.
(33 )
Another reference stated that heating organic compounds in
the presence of ammonium bicarbonate often produced a fluorescent residue.
Methyl parathion was heated with ammonium bicarbonate for one hour at
110°C without success.
32. Metcalf, R.L., et. al., J. Agr. Food Chem., 16, 300-311(1968).
33. Chem. Eng. News, 18-19, November 25, 1974.
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