ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF ENFORCEMENT
EPA-330/2-76-038
PESTICIDE USE OBSERVATIONS
LEFLORE COUNTY, MISSISSIPPI
(JULY 25-AUGUST 1, 1976]
ENFORCEMENT INVESTIGATIONS CENTER
DENVER, COLORADO
DECEMBER 1976
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Environmental Protection Agency
Office of Enforcement
• EPA-330/2-76-038
PESTICIDE USE OBSERVATIONS
LEFLORE COUNTY, MISSISSIPPI
(July 25-August 7, 1976)
December 1976
National Enforcement Investigations-Center
Denver, Colorado
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CONTENTS
I INTRODUCTION . .' 1
II SUMMARY AND CONCLUSIONS 3
General Conclusions 3
Specific Conclusions 4
c
III DESCRIPTION OF THE STUDY AREA . 6
IV RESULTS AND DISCUSSION 10
Insect Infestation Assessment ....... 10
Environmental Assessment ......... 10
First Application 13
Second Application 21
V EVALUATION 24
REFERENCES 26
APPENDIX
DESCRIPTION OF SAMPLING TECHNIQUES
AND METHODS 27
TABLES
1 Samples Collected from a Cotton Field ... 8
2 Water, Soil, Vegetation and Air
Analytical Results . . . . 11
3 Impingement of Droplets on Magnesium
Oxide Slides and Kromecote Cards .... 20
o
FIGURES
1 Description of study area 7
2 Mobile meteorological laboratory with air
sampling impinger system . 9
3 Mylar sheet, Kromecote card, and
magnesium-oxide-coated slides . . . . . . 12
4 Inspectors collect formulation samples . . 15
5 Rinsing pesticide mixing vat after
pesticide application 18
6 Landfill disposal site for empty
pesticide containers 18
7 Pesticide residue is dumped from plane
hopper into a portable vat 1?8
8 Cleanup of pesticide spray boom 1.8
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I.
INTRODUCTION
Throughout the cotton belt of the United States, there are one or
more major insect pests that must be controlled annually if cotton is to
be grown profitably. Contemporary cotton production requires the use of
more insecticides than any other single crop.l This intense and widespread
use of insecticides on cotton could create environmental and human
health problems that may be more devastating than the pest damage
itself. For these reasons, it is essential that a monitoring program be
adopted by pesticide regulatory agencies to observe and enforce good
pest control practices by cotton growers.
With this background, EPA Region IV and the National Enforcement
Investigations Center (NEIC) conducted the second in the series of
National Pesticide Use Observation studies in the cotton belt of
Mississippi. Study objectives were:
1.
Observe and evaluate pesticide handling, application and
disposal practices at a Mississippi Delta cotton farm.
2.
Ascertain whether pesticide use is consistent with instructions
on the label.
3.
Develop methods, transfer technology and
needed to document environmental hazards
pesticides.
establish criteria
and the proper use of
. 4.
Determine appropriate Agency actions needed
occupational health risks and environmental
pesticide use.
to minimi ze
damage caused by
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2
A study site in Leflore County, Mississippi was selected by EPA
Region IV and State officials. The site is near Morgan City, about 46
km (25 mi) southwest of Greenwood. Traditionally, Leflore County has
had the highest production of cotton in the state of Mississippi. In
1976, more than 102,000 acres in this County were planted in cotton.2
Pesticides were applied by aircraft to the study site on July 29
and August 4, 1976, respectively. During both applications, a mixture
of the insecticides methyl parathion and ga1ecron was sprayed. Pre-
application, application and post-application activities were evaluated
by a team of EPA observers from NEIC, Region IV and the Pesticide and
Toxic Substances Enforcement Division. Use practices, environmental
impact, and monitoring technology are described in this report.
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II.
SUMMARY AND CONCLUSIONS
In July and August 1976, the second study of the National Pesticide
Use Observation Program was conducted by NEIC at a cotton farm in Leflore
County, Mississippi. During the 12-day s,tudy, an EPA observation team
evaluated activities associated with two commercial aerial app1ication~
of methyl parathion and ga1ecron on cotton to control an infestation of
bollworms and boll weevils.
GENERAL CONCLUSIONS
The use observation study in Mississippi revealed exemplary clean-
up and disposal practices; however, deficiencies were documented in
handling and application of the insecticides.
Pesticide use was inconsistent with the label instructions.
The most valuable techniques used to document the practices and
environmental effects of the aerial applications were: on-site evaluations
by trained observers; spray droplet cards to determine pesticide drift;
and water quality sampling to determine pesticide translocation by
surface runoff from the target field.
The study indicated a need for the EPA and State officials to:
a) determine and define the protective apparel and equipment essential
for pesticide handling and use operations, and require the use of such
apparel and equipment; b) review and update pesticide labels more
frequently; c) regulate more closely farm residents' activities during
and after pesticide applications; d) continue to study environmental
effects of repeated pesticide applications on non-target organisms.
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4
SPECIFIC CONCLUSIONS
1.
During pre-application, human health
handling and mixing pesticides were
apparel and bystanders were allowed
protective equipment and clothing.
hazards were oDserved. Workers
not wearing complete safety
in the mixing area without
2.
Meteorological instruments were not available to assist the applicator
in determining conditions such as local wind speed and direction,
relative humidity and air temperature. Nevertheless, good weather
conditions prevailed, which proved to be an important factor in
minimizing pesticide drift.
3.
Activities were practiced by the commercial applicator which were
inconsistent with the pesticide label instructions. These included
the aerial application of pesticides 1) at an unapproved dosage
rate, 2) while unprotected persons were in the drift area, and 3)
during irrigation runoff from the target field.
4.
A review of the Stap1cotnGDMethy1 Parathion 4EC label revealed
errors in the recommended waiting periods between application and
re-entry or harvesting as specified by the Code of FederaZ ReguZations,
Part 170, Title 40, July 1975.
5.
Kromecote cards were excellent for immediate detection of methyl
parathion and ga1ecron drift. Vertically placed cards appeared to
be better detectors of drift than horizontal cards, and both were
better than magnesium-oxide-coated microscope slides for evaluating
dri ft.
6.
From analyses of the Kromecote cards and the magnesium-oxide-coated
slides, it was estimated that 25 to 35% of the pesticide drifted off
the target field. During the first aerial application, the pesticide
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5
mixture drifted northeast at least 100 m (330 ft) into a pasture
and into Bear Creek. During the second aerial application, drift
was to be southwest into a soybean field and into Mossy Lake.
7.
A fluorescent dye was added to the methyl parathion and galecron
mixture in an attempt to obtain additional pesticide drift information.
Fluorescent analysis of ambient air samples failed to show any dye
concentrations. The mylar sheet technique also was unsuccessful in
collecting measurable amounts of dye used to trace the pesticide
drift. The reason for failure is believed to be the low concentration
of tracer dye (200 ppb) used.
8.
Post-application environmental sampling revealed measurable amounts
(0.1 to 24.0 ~g/l) of methyl parathion in nearby bodies of water
(Mossy Lake, Bear Creek and drainage ditches). Singly or in
combination, the contamination of these neighboring streams and
lake was believed to be the result of spray drift and irrigation
runoff.
9.
Pesticide contamination appeared to adversely affect the fish
population in drainage ditches. On-site observations revealed that
ditches with water containing up to 0.6 ~g/l methyl parathion had a
thriving population of minnows. In a ditch where the methyl parathion
in water was found to be 24.0 ~g/l, no fish life was observed.
Fish were also examined from the lake into which these ditches
drain. No acute pesticide poisoning symptoms were detected in
these lake fish.
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III.
DESCRIPTION OF THE STUDY AREA
The farm observed in this pesticide use study contained a 63.5
hectare (157 acre) cotton field [Fig. lJ. The target field was bordered
by soybean fields, pasture, a lake, creek, ditches with flowing or
standing water and residences. The southwest corner was separated from
the rest of the field by a small north-south soybean field and an east-
west strip containing farm buildings, a residence and an artesian well.
Forty-two stations were established to monitor pesticide dispersal
and environmental effects [Table lJ. Samples were collected from all
stations except 9, 15 and 21, which were established during the recon-
naissance but were later eliminated. Eleven stations were located on
the target cotton field; eighteen were off the field, two were in Bear
Creek, four in Mossy Lake; and two each in a north-south ditch and an
artesian-fed drainage ditch.
The NEIC observation team set up a meteorological laboratory on the
west side of the cotton field near station 19 [Fig. 2]. Wind direction
and average velocity, and air temperature at 2.4 m (8 ft) and 9.7 m
(32 ft) (to determine temperature inversion) were monitored. Other
meteorological information was obtained from the Greenwood municipal
airport, located about 46.3 km (25 mi) northeast of the study site.
,
Channel catfish were held in cages in Bear Creek (stations 2 and
3), in an artesian-fed drainage ditch (station 20) and in Mossy Lake
(stations 39, 40, 41 and 42) to monitor biotic effects of pesticide
exposure.
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Figure I. Sampling Sites, Leflore County, Mississippi, July-August 1976
,,f'
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!".,' a ~:.
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D
L.flore County. MI$B15Sippi
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8
Table 1
SAMPLES COLLECTED FROM A COTTON FIELD
LefZore County, Mississippi
Station Air Mylar MgO Kromecote Vegetatic;m Soil Hater Aquatic Sediment Fish
No. Slides Ca~ds Plants
1 I I I I I
2 I
3 I I I
4 I I I / I
5 I
6 I I I I I
7 I I I I I /
8 I
10 I I I I I I
11 I I
12 . I I I I I
13 I I I / /
14 I
16 I
17 I I I I I
18 I / I I I
19 I I I I /
20 I I I I
22 I
23 I I I / I
24 I
25 I / I I
26 I I I / I
27 I
28 I I I
29 I
30 /
31 I I / / I
32 / I I I
33 I
34 I
35 I I / / I
36 I I /
37 / / / / I
38 I
39 / I I
40 / I I
41 / I I
42 / / I
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I.
I
"
;....
",J
- ,- -'-~-
'.'
W'
Figure 2. Mobile meteorological laboratory with
air sampling impinger system in foreground.
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IV.
RESULTS AND DISCUSSION
INSECT INFESTATION ASSESSMENT
On July 25 an agricultural consultant employed by the farmer
examined the cotton field. The terminals and "squares" (future bolls)
on 100 cotton plants were examined. This examination showed an infestation
of boll weevil (Anthonomus.grandis) and bo~lworrn (HeZiothis sp). Tarnished
plant bugs (Lygus ZineoZis) were observed also. The southernmost portion
of the cotton field had the largest insect population. To control the
infestation, the consultant recommended aerial application of a mixture
of Methyl Parathion 4EC* and Galecron 4EC**. The methyl parathion was
suggested to kill the existing insect pests; galecron, an ovicide, was
recommended to prevent hatching of the eggs of these pests.
ENVIRONMENTAL ASSESSMENT
On July 27, 1976, soil, vegetation, and water were collected to
establish background levels prior to the insecticide application [Table 2J.
A few hours before the July 29, 1976 pesticide application, air and
drift sampling devices were placed in and at varying distances from the
target field. \Four types of sampling gear were used: an air sampler,
using the Greenburg-Smith impinger system [Fig. 2]; Kromecote cards, set
horizontally; magnesium-oxide-coated slides, and mylar sheets [Fig. 3].
Each technique is described in detail in the Appendix.
* EPA Registration No. 8648-12
** GaZecron~ trademark of CIBA-GEIGY Corp.; EPA Registration No. 8192-7
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Tahz.e 2
WATER, SOIL, VEGETATION AND AIR
ANALYTICAL RESULTS (METHYL PARATHION) t
Juz.y-August 1976
Station
No.
3 Bear Creek Water N.D. tt 3.1
11 'Ditch 0.3 1.0
20 Artesian-fed ditch N.D. N.D.
28 Artesian-fed ditch 0.3 0.1
36 Ditch 0.5 0.3
39 Mossy Lake N.D. 0.3
40 Mossy Lake N.D. N.D.
41 Mossy Lake N.D. 0.1
42 ~lossy Lake N.D. 0.3
6 Pasture Soil N.D. 0.007
6 Pasture Vegetation, 0.17 0.92
10 Cotton Field Soil N.D. 0.11
10 Cotton Field Vegetation 0.09 1.3
19 Near residence Soi 1 N.D. 0.008
5 Pasture Air 4.4
7 Soybeans 1.6
10 Cotton field 6.2
12 Soybeans 2.4
18 Soybeans 1.2
19 Near Residence 1.6
23 Soybeans 1.2
35 Near Residence 1.2
Location
Type
Sample
1st App1ication
Background Application
July 27 July 29
Residue
July 31
2nd ApD1ication
Application Residue
August 4 August 6
2.6 2.6
N.D. 0.6
0.2
24.0 0.3
8.0
0.2
1.0 N.D.
0.1
0.2
2.1
2.2
0;2
4.9
4.6
1.9
0.4
t Vaz.ues in wate~ exp~eBsed as mg/z.; in Boil. and vegetation as ~g/g; and in ai~ as ~g of methyl.
parathion
tt None deteated
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Figure 3. (Z to r) Mylar sheet, Kromecote card,
and magnesium-oxide-coated slides.
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Impinger units were placed in the Northeast corner of the cotton
field (station 10) and at seven locations bordering the field (stations
5, 7, 12, 18, 19, 23 and 35) [Fig. 1, Table 1]. Spray drift evaluation
stations were selected to monitor potential contamination of the surround-
ing area.
FIRST APPLICATION
Preparation
Before the pesticide was applied to the cotton on July 29, personnel
from NEIC, EPA Region IV, and the State observed the pesticide handling,
mixing and loading by the commercial applicator.
The pesticides were delivered to the applicator's mixing and
site by a distributor shortly before they were used. A pesticide
was obtained by the EPA for later examination.
loading
label
The Stap1cotn
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During pesticide mixing and loading, employees of the aerial
applicator wore a variety of safety clothes. All wore caps, trousers,
shirts and boots. In addition, some wore gloves and canister-type
respirators. The aircraft pilots' protective gear consisted of a crash
helmet and a respirator. Both Company and non-Company individuals were
present without complete safe~y gear during the mixing and loading
operation.
The protective clothing worn by EPA personnel during the mixing and
loading operation consisted of the canister-type respirator, goggles,
disposable cap or hard hat, a full front apron, long-sleeved coverall,
gloves, and boots [Fig. 4].
The mix~ng and loading activities were observed by EPA and recorded
as follows. Seventy-two liters (19 gallons) of methyl parathion (44.4%)
and 18 liters (4.75 gal) of galecron (48.5%) were pumped and poured
simultaneously into a mixing vat which had a capacity of approximately
227 liters (60 gal). A fluorescent tracer dye, Rhodamine WT, was added.
The mixture of the pesticides and dye was pumped into another pre-mix
tank where water was added. Then the mixture was pumped into the
aircraft tank. The final volume of di)uted pesticide (153 gal) was
attained by pumping additional water into the aircraft tank.
This mixture provided an aerial application rate of 1.5 liters/
hectare (1 gal/acre), which is inconsistent with the StaPlcotn@ Methyl
Parathion 4EC label dosage of "2 to 5 gallons of water per acre" when
applied by aircraft. The actual active ingredient of 0.47 liters (1
pint) per acre of methyl parathion was applied as specified on the
label. The application rate of galecron 'was in compliance with its
registered label. .
During the aircraft loading activity, pesticide formulation samples
were collected for comparison with labeling and other applicable regulations
[Fig. 4]. Later analysis of these samples revealed that the formulations
were chemically in compliance with State and Federal regulations.
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. ,,~.,.:.- - ~ "'r:i .-' .,' - - - - r
~~... -.,.'1". . ~:&:4
/' . ~ [
"."''''' ,~'-' ~--' "'"".
.
- . -~ ..::...
, ~-;:'.
Figure 4. Pesticide inspectors from the State
of Mississippi and EPA collect pesticide
formulation samples.
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Application
Observations
The aircraft used for the pesticide application was a Cessna Ag
Wagon equipped with a 22-nozzle spray boom. The nozzle orifice and core
combination was 06 with a 45 spinner. The orifice ~iameter was 0.094
inch. This configuration of aircraft and spray equipment is designed to
apply low volumes of liquid at a high rate of speed.
The first pesticide application began at 8:15 a.m. (COT) and was
completed at 8:57 a.m. on July 29.
On-site air temperatures varied from 25.6 to 26.7°C (78 to 80°F).
No temperature inversion was observed. The wind ranged from 0 to 6.4
km/hr (4 mph) from the SW. The weather report from the Greenwood
Municipal Airport gave temperatures ranging from 24 to 25.6°C (75 to
78°F), wind varying from SSW to WSW, and relative humidity 94 to 100%.
Passes over most of the cotton field were made in a north-south
direction, parallel to the rows of cotton, at about 2 m (7 ft). The
southernmost portion of the field was sprayed in an east-west or west-
east direction. A spray swath about 18 m (60 ft) wide occurred with
about a 3 m (10 ft) overlap on each pass. Before completing the application,
the north and south edges of the field were bordered by east-west and
west-east passes.
A tractor was operated on the field, near station 28, throughout
the entire first application. The tractor operator was without protective
clothing. It is stated on the StaplcotncrpMethy1 Parathion 4EC label:
"Remove unprotected persons and domestic animals from operating and
adjacent areas where insecticide may drift; prohibit re-entry until
drift and vapor dissipate. II Also in the Code of FederaZ ReguZations,
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Part 170, Title 40 (July 1,1975) it is stated that: "When workers are
,~xpected to be working in a field treated or to be treated with a
pesticide, appropriate and timely warning to such worker shall be given.
The warning may be given ora1)y and/or bi posting warning signs at the
usual points of entrance to the field. . .11
Clean-Up Activities
After loading the pesticide into the aircraft, several clean-up
procedures were used by the applicator. Disposable items (paper towels,
gloves, etc.) were burned on-site. The mixing vat was rinsed with clean
water [Fig. 5]. The sprayer was then turned upward to rinse empty
pesticide containers in an inverted position. All rinse water was
pumped into labeled containers and stored until that part~cu1ar solution
is used again. Rinsed five-gallon containers were taken to the city of
Greenwood landfill site to be buried [Fig. 6J. Rinsed 55-gallon drums
were retained for sale to a cooperage company.
After the insecticide application, the plane was washed by first
dumping the pesticide residue from the hopper into a portable vat [Fig.
7J. A hose was attached to the vat and to one end of the spray boom
[Fig. 8] and a fresh water source was coupled to the other end. The
water forced material out of the boom, through the hose, and into the
vat. Next, the spray valve was opened so that the water back-flushed
the strainers, valves and pumps. The hopper was washed and rinsed into
the vat. The pesticides and rinse water 'captured in the vat were pumped
into labeled containers and stored as described previously.
Post-First Application
As during pre-application, environmental samples (soil, veget~tion,
water and sediment) were collected from areas of potential pesticide
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...
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Figure 5.
Rinsing pesticide mixing vat after
pesticide application.
.:-~
--"',t~f"'t,
Fi gure 7.
Pesticide residue is dumped from plane
hopper into a portable vat.
- - -- - --
Figure 6.
Landfi 11 di sposal site for empty
pesticide containers.
t.- --.: . ,... -
~r
- ,
"';IS - ~:':':.-
F~ ,
. .~.
~u.
--
_. '-
. ~
..
-
Fi gure 8.
Cleanup of pesticide spray boom.
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19
'contamination for chemical analysis.
of methyl parathion only.
Analysis was limited to detection
Methyl parathion was found in sev~ral water samples [Table 2J.
This insecticide was not detected in samples collected from Bear Creek
on July 27 before the first application [Table 2J. On July 31, 48 hours
-after the first application, Bear Creek water contained 3.1 pg/l methyl
parathion. Mossy Lake samples ranged from not detectable before to 0.3
pg/l forty-eight hours after application. All the ditches sampled
contained some methyl parathion prior to and after the first application
of pesticides.
Background vegetation samples from the cotton field and a nearby
pasture contained methyl parathion concentrations of 0.09 to 0.17 pgjg.
This indicated drift from other field applications. Following the
application on the target field, vegetation samples at the same sites
ranged from 0.92 to 1.3 pgjg.
No detectable amounts of methyl parathio~ were found in background
soil samples and low concentrations were measured after the first
application (0.007 to 0.11 pg/g).
An air sample collected in ethylene glycol by an impinger system,
operated in the northeast corner of the cotton field (station 10),
contained 6.2 pg of methyl parathion. Air samples collected by impinger
systems situated off the target field, along the east (station 23),
west (station 18) and south (station 35) borders, contained 1.2 pgof
methyl parathion. An air sample from an impinger system located in a
pasture north or downwind from the cotton field, contained 4.4 pg
methyl parathion.
Drift deposits were collected on. magnesium slides, Kromecote cards,
and mylar sheets [Table 3J. The number of droplets per square centimeter
on the slides ranged from 28 at station 10, located in the northeast
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20
Table J
.IMPINGEMENT OF DROPLETS ON MAGNESIUM OXIDE SLIDES
AND KROMECOTE CARDS
July-August 1976
1st Application 2nd Application
Station (dr6Plets/cm2) 2
No. (droplets/cm )
Slides Kromecote Slides Kromecote
. (Horizontal) (Horizontal)(Vertical)
1 3 4 0
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21
corner of the field, to 3 at station 1, located on the northern bank of
Bear Creek about 100 m (330 ft). Measurements of pesticide spray drops
deposited on the slides, cards and sheets revealed that the average
volume median diameter (VMD)* was 154 ~ on the target field and 53 ~ for
droplets that drifted beyond the field.
To further evaluate drift, Rhodamine WT dye solution added to the
pesticide spray mixture was also monitored with the Greenburg-Smith air
sampler and mylar sheets. No measurable amount of dye was found in the
Greenburg-Smith impingers or on the mylar sheets.
SECOND APPLICATION
Preparation and Application
The pesticides methyl parathion and galecron were applied a second
time, August 4, six days after the first application (July 29, 1976).
Mixing and loading operations were similar to those for the first
application.
During the second application, the wind varied from 0 to 1.6 km/hr
(1 mph) from the NE. The day was cooler -- 22.2 to 23.9°C (72 to 75°F) --
than it was during the first application -- 25.6 to 26.7°C (78 to
80°F). No temperature inversion was observed. At the Greenwood Municipal
Airport, air temperatures ranged from 22.2 to 25.6°C (72 to 78°F) and
relative humidity varied from 72 to 74%.
* VMD is that voZume which divides the distribution of dropZet diameters
into two equal parts about the median .or 50% cumuZative point.
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22
Observations
The flight pattern during the second application was different from
the first in that the entire field including the southernmost portion
(originally applied with east-west and west-east passes), was sprayed
from north-south or south-north passes. The second application was five
minutes shorter than the first; it began at 8:00 a.m. and was completed
37 minutes later at 8:37 a.m.
During the application,' occupied vehicles moved across the field
roads and on adjacent roads.
Environmental Sampling
On August 4, 1976 after the second pesticide application, selected
environmental samples were again analyzed for methyl parathion. Results
revealed 24 ~g/l of methyl parathion in irrigation water draining from
the treated cotton field (station 28). Use of methyl parathion on an
irrigated field is inconsistent with the label requirements which state:
IIkeep out of any body of waterll and lido not apply where runoff is likely
to occur.1I
Station 28 was in an artesian-fed drainage ditch about 300 m (1,000 '
ft) downstream fro~ station 20. The latter station is adjacent to the
north edge of the cotton field and methyl parathion concentrations at
this site ranged from below detectable limits on July 27,to 0.2 ~g/l on
August 6, 1976. Seven observations were 'made at these two sites from
May until August 1976. On all seven occasions, fish ~ere present at
station 20; whereas, downstream at station 28 no fish were present in
the same artesian-fed drainage ditch. In another ditch, east and south
of the cotton field (station 36), the methyl parathion concentration in
the water was 8.0 ~g/l, higher than at any other site on August 6, 1976.
,Station 36 is about 300 m (1,000 ft) from the target field. There was
no flow in this ditch during the application or sampling periods.
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As shown in Table 2, air samples collected from the
" ' .
. contained methyl parathion concentrations in the solvent
0.4 ~g in the. southeast corner of the field (station 35)
of the target field (station 18). '
impinger system
ranging from
to 4.9 ~g west
Drift deposits recorded on magnesium-oxide-coated slides and Kromecote
cards are reported in Table 3. Drift (droplets) was recorded as far
away as 100 m (330 ft) on the downwind side of the target field (SW) at
station 26. Droplets were detected on Kromecote cards set out for the
second application at the water's edge of an artesian-fed drainage ditch
near station 28 and at the shoreline of Mossy Lake near station 40
[Table 2]. The presence of methyl parathion was verified in the analyses
of water collected from both stations 28 and 40 [Table 2]. The VMD for
the second application was calculated to be 123 ~m on the target field
and about 50 ~m for the droplets that drifted beyond the field.
No drift information was obtained from the use of the dye tracer.
Dye was not detected in either the impinger systems or on the mylar
sheets.
After the second appl ication, 'channel catfish which had been
. ,
exposed from May 11 to August 6 were analyzed for acetylcholinesterase
inhibition. There was no change in the acetylcholinesterase activity of
the fish brain, no inhibition, or indication of pesticide poisoning in
Mossy Lake. Unfortunately fish cages at station 20 in the artesian-fed
drainage ditch, and at stations 2 and 3 in Bear Creek, were missing or
destroyed.
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V.
EVALUATION
o
Observations by EPA of the two aerial pesticide applications led to
the conclusions that pesticides were subject to drift from the cotton
"field as a result of: 1) airplane turbul~nce, 2) meteorological conditions,
and 3) droplet size and natur~. Pesticide droplets in the air appeared
to be transported by the combined forces of turbulence, wind speed, and
gravity.
Drift from wind can be minimized by applying pesticides only at
times of low wind velocity. The wind velocity during the first and
second applications varied from 0 to 6.4 km/hr (4 mph), thus minimizing
the drift.
The amount of drift is also related to the size and nature of the
spray droplets.l Droplet data obtained from magnesium oxide slides
revealed that the average droplet size at a station off the field was
nearly 70% smaller than that of droplets falling on the field. The
slides were also useful in determining the true drop "size and the
average volume median diameter (VMD) of ' the sprayed droplets. The VMD
is used in measuring the potential drift of droplets sprayed on the
cotton field, and was calculated to be 154 ~and 123 ~ for the first and
second applications, respectively. It was also estimated that 25 to 35%
of the pesticide drifted off the field to measured distances of 100 m
(330 ft) downwind. "An undetermined amount of the drift was deposited in
Bear Creek and Mossy Lake.
"The combined factors of high humidit~ and moderate air temperature
reduce the evaporation rate of thewater-b~sed pesticide droplets and
thus the drift potential. During the applications, the relative humidity
ranged from 72 to 100% and the air temperatures from 22.2 to 26.7°C
(72 to BO°F).
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25
Some research indicates that the collection efficiency of magnesium-
, oxide-coated slides is low and the data are skewed toward larger sizes,
thus making VMD measurements questionable.3 A current effort is being
made in the Department of Entomology at the University of Georgia to
standardize field methods for determination of insecticide spray droplet
size.
Kromecote cards appear to be superior to magnesium-oxide-coated
slides where quick interpretation and response is required, as in en-
forcement investigations. Based on the number of droplets per square
centimeters, Kromecote cards appeared to be more efficient collecting
devices than magnesium-oxide-coated slides; Kromecote cards were impinged
an average of 3.7/cm2 while magnesium-oxide-coated slides were impinged
2.2/cm2. Vertical Kromecote card droplet counts averaged greater than
either horizontal cards or slides, 5.4, 3.7 and 2.2/cm2, respectively.
Other workers have also observed that fewer droplets are deposited on
cards placed horizontally than those placed vertically above vegetation.4
Horizontal Kromecote cards were better than slides in spite of being
closer to the ground and farther below the height of the cotton plants
[Table 3J.
Rhodamine WT dye used as a tracer in the pesticide mixture at a
concentration of 200 ~g/l was not detected in the impinger systems or on
the mylar sheets. The literature indicates that another dye, Rhodamine
. B, at a concentration of 0.1% is satisfactory.s Lower concentrations of
Rhodamine WT may be satisfactory since it does not degrade as rapidly as
Rhodamine B, which undergoes fading at non-constant rates depending on
the exposure to sunlight. However, the extremely low concentration of
200 ~g/l used in this study was below detectable limits. Further tests
should be made using higher concentrations of Rhodamine WT dye.
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26
REFERENCES
1.
R. von Rumker, G. L. Kelso, F. Horay and K. A. Lawrence, 1975. A
study of the efficiency of the use of pesticides in agriculture.
EPA Report No. EPA-540/9-75-025, 250 p.
2.
Communication with Charles Hall. U.S. Dept. Agriculture, ASCS
Office, Greenwood, Miss., Aug. 9, 1976.
3.
C. M. Himel, and R. McDaniel, 1975. Standardization of field
methods for determination of insecticide spray droplet size.
Office of Naval Research. Contract lV00014-70-A-0309-003 Task No.
NR136-977/5-9-74 Annual Rpt. No.1, 14 p.
4.
C. B. Rathburn, Jr., A. J. Rogers, A. H. Borke, Jr. and R. M. Lee
1969. Evaluation of the ultra-low volume aerial spray technique by
use of caged adult mosquitoes. Mosquito News, Vol. 29, No.3,
p 376-381.
5.
Proceedings Spray Deposit Assessment Workshop, March 16-18, 1976.
Davis, California. 33 p. Sponsored by U. S. Forest Service, FIDM-
Methods Application Group, U.S.D.A. Expanded Gypsy Moth Program.
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APPENDIX
DESCRIPTION OF SAMPLING TECHNIQUES AND METHODS
A number of techniques were used to determine spray drift. Kromecote
cards (4 x 5 in.) were placed horizontally and vertically on stands in
the fields. The vertical cards were placed higher than both horizontal
cards and the MgO slides. Vertical Kromecote cards were wrapped around
the outside of a plastic cylinder marked and positioned facing the four
cardinal directions. After a pesticide spray application, Kromecote
cards must be exposed to UV light in order to develop visible spots.
Another technique used to sample the drift droplets was the magnesium
oxide coated microscope slide.
A slide is coated by burning a strip of magnesium beneath it. The
impinged spray droplets leave visible crater on the magnesium oxide
coated slide. The droplet-caused craters were measured to the nearest
micron at 100X magnification; up to 200 craters on a slide were measured.
The slide with the most droplets was selected at each site. The data
were used to compute the VMD.
Air samples were collected by using the Greenburg Smith impinger.
.
This system contains a pump that draws the air through an impinger. The
air flow is controlled and measured and after a pre-set time interval
the air flow is switched from one impinger to another. Each unit was
numbered and assigned to a station and was used only at that station.
Air flow rates were set for 1 ft3/min. Pesticide-free aluminum foil was
used to cover the air intake tubes prior to the sample collection. The
air sampling units switched automatically from one impinger to the next
after three hours and off at the end of twelve hours. Each impinger
contained 100 ml of ethylene glycol in which pesticides are trapped.
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A five ml sample from a 25 ml subsample of ethylene glycol, containing
trapped pesticides, was poured into matched cuvettes and fluorescence
was measured. The sample was. then returned to the original container to
make up a 100 ml sample to be taken to Denver NEIC laboratory for pesticide
analysis.
I
Another method used to collect the insecticide and dye mixture was
mylar sheets. These sheets, 10.2 x 30.5 cm x 5 mil thick, were placed
on a stand about 0.5 m above the ground. Dye retained on mylar sheets
would be evidence of spray drift. To determine the presence of dye,
each sheet was washed with 100 ml of 95% ethyl alcohol. In the Mississippi
study, no dye was detected.
Environmental samples (soil, water, etc.) were collected by standard
methods.
DESCRIPTION OF ANALYTICAL METHODS
Water samples were serially extracted using 100 + 50 + 50 ml of
methylene chl.oride. Extracts were combined and passed through a sodium
sulfate column to eliminate free water and concentrated to approximately
6 ml in a Kuderna-Danish evaporative concentrator. The extract was then
exchanged into acetone.
The extracts were cleaned up using a Florisil column eluted with
15% ethyl ether in hexane. Fifty ml fractions were collected and methyl
parathion eluted in fractions 3, 4, 5 and 6. The extracts were concentrated
to 10 ml on a hot plate under a gentle stream of air and analyzed on a
gas chromatograph equipped with an electron-capture detector.
Soil and vegetation samples were extracted twice with 100 ml of
methylene chloride. The extracts were combined, backextracted with 200
ml of water, passed through a sodium sulfate column and concentrated to
approximately 6 ml in a Kuderna-Danis~ evaporative concentrator. The
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extract was then exchanged into acetone.
The cleanup and analysis were identical to those described above
for the, wa ter sample s .
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