ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF ENFORCEMENT
EPA-330/2-76-032
Pesticide Use Observations
Kent County, Delaware
June 2-7, 1976
ENFORCEMENT INVESTIGATIONS CENTER
DENVER, COLORADO
OCTOBER 1976
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Environmental Protection Agency
Office of Enforcement
PESTICIDE USE OBSERVATIONS
IN
KENT COUNTY, DELAWARE
June 2-7, 1976
October 1976
National Enforcement Investigations Center
Denver, Colorado
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CONTENTS
I INTRODUCTION. . . . . . . . .
. . . . .
. . . . . .
II SUMMARY AND CONCLUSIONS. . . . . . . . . . . . . . .
General Conclusions. . . . . . . . . . . . . . . . .
Specific Conclusions. . . . . . . . . . . . . . . .
III DESCRIPTION OF STUDY AREA.
. . . . . . .
. . . . . .
IV USE OBSERVATIONS. . . . . . . . . . . . . . . . . .
Pre-Application. . . . . . . . . . . . . . . . . .
Application. . . . . . . . . . . . . . . . . . . .
Post-Application. . . . . . . . . . . . . . . . . .
EVALUATION OF OBSERVATION METHODS. . . . . . . . . . 34
REFERENCES
. . . . . . . . . . .
. . . .
. . . . . .
APPENDIX: SAMPLING DEVICES AND METHODS.
. . . .
TABLES
1
Impinger, Personnel Monitor, Water and Sediment
Analytical Data (Guthion) ............
2 Results of Magnesium Oxide Slides
. . . .
. . . . .
3 Dye Analysis of Mylar Sheets and Cascade Impactors
FIGURES
1 Location of potato field study site. . . . . . . .
2 Mixing pesticide materials prior to application. . .
3 Safety clothing worn by EPA personnel. . . . . . . .
4 Sampling locations. . . . . . . . . . . . . . . . .
5 Air sampling device, Greenburg-Smith impinger '.' . .
6 High-volume air sampling device. . . . . . . . . . .
7 Spray drift evaluated by Kromecote cards, glass
slides, and mylar sheet. . . . . . . . . . . . . .
8 Grumman airplane applying pesticides. . . . . . . .
9 Streamer marking spray pass. . . . . . . . . . . . .
10 Aerial pesticide application. . . . . . . . . . . .
11 Used pesticide containers found on dump site. . . .
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1.
INTRODUCTION
The Environmental Protection Agency (EPA) is involved in the development
and implementation of a national pesticdes use observation program. The
initial site selected for study was in the northeastern United States
(EPA Region III), a potato field near Magnolia, Delaware. The study
site consisted of 16 hectares (39.6 acres) bordered by soybeans, barley,
woodlands and human habitations. Scientists from the National Enforcement
Investigations Center (NEIC) conducted on-site audits of pre-application,
application, and post-application operations. The audits were conducted
with the following objectives:
1.
Thoroughly investigate storage, handling, application and
disposal of pesticides by observing operations on a typical
Delaware potato-producing farm.
2.
Assess methods and transfer technology and establish criteria
needed to scientifically document environmental hazards associated
with the use of pesticides.
3.
Determine the most appropriate type of Agency action which
should be initiated to minimize risks to. human health and the
environment.
A six-day pesticide observation study began June 2, 1976 and the
potato field pesticide application began on June 4, 1976. . The study
included sampling of air, water, sediment, soil and biota, which were
analyzed in the event of a major misuse condition. A dye tracer technique
along with spray droplet impaction devices were used to determine the
drift characteristics of the aerially applied pesticide. In addition,
observations were conducted on-site to determine if the pesticide users
read and understood the labels on the products; followed the directions
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2
and precautions on the label; properly cleaned the application and
protective equipment and maintained it in good working order; properly
stored pesticides; and properly disposed of excess pesticides and
containers so as to create minimal impact on the environment.
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. I I.
SUMMARY AND CONCLUSIONS
In June 1976, University of Delaware entomologists recommended
aerial application of Dithane (M-45@)* to prevent blight, and Guthion
2-S** to control a Colorado potato beetle infestation in a potato field
in Kent County, Delaware.
A field investigation was conducted June 2-7, 1976 to evaluate the
operations and methods of an aerial applicator prior to, during, and
after treatment of a Delaware potato field with guthion and dithane for
control of the Colorado potato beetle and prevention of blight, respectively.
GENERAL CONCLUSIONS
1.
The use observation study in Delaware revealed exemplary pesticide
storage and application practices. It also revealed operational
deficiencies during the handling and disposal of pesticides.
2.
Of the twelve sampling and observational techniques used to document
environmental effects caused by pesticide use, the most valuable
were: on-site observations by trained observers, tracer dye studies,
and droplet-size characterization.
3.
Study results indicated an immediate need for the EPA and State
officials to:
* Rohm and Haas, EPA Reg. No. 707-78-AA.
** Chemagro, EPA Reg. Ho. 3125-123-ZA.
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4
(a)
enforce the use of protective equipment and apparel during all
pesticide handling and use operations, and
(b)
establish environmentally safe dump sites
proper disposal of highly toxic compounds
containers.
designed for the
and used chemical
SPECIFIC CONCLUSIONS
1.
An observation tour of the applicator's premises showed that pesticides
were properly and securely stored and spraying equipment was in
excellent maintenance.
2.
During pre-application pesticide handling activities, a human
health hazard was observed because safety apparel was not worn by
all personnel. Specifically, non-Company personnel were allowed in
the mixing area without protective clothing.
3.
Weather instruments were not available to assist the applicator in
determining local micrometeorological conditions before insecticide
application. Ideally, wind speed and direction and temperature
should be measured near the target field. However, this may create
certain logistical problems for the applicator.
4. .
Observations and dye tracer studies conducted by the EPA during the
aerial applications indicated that no pesticide misuse or environmental
harm occurred. Pesticide drift off the target field was the result
of occasional overspraying and atmospheric transport of minute
spray particles. Dye tracer studies indicated that most of the
drifting spray settled within 40 feet on adjacent fields.
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5
5.
Good weather conditions, the use of relatively large spray droplets
(up to 335 ~m), and excellent pilot judgment during the aerial
application were major factors in minimizing pesticide drift.
6.
Although the applicator followed all precautions for the proper
disposal of used pesticide containers, accumulations of used
containers were observed on the study farm. This haphazard
disposal practice by unknown persons constituted a hazard to
environmental quality and human health. Furthermore, such disposal
is a violation of EPA Regulations (Federal Register Vol. 39, No.
85, May 1,1974), a condition augmented by the fact that the State'
of Delaware has no Class I dump sites.
7.
Personnel monitors and Greenburg-Smith impinger devices were used
to semi-quantitatively monitor the atmospheric transport of
guthion. Their value in documenting specific amounts of airborne
pesticides was limited because of variable temperatures, vapor
pressures, pesticide concentrations, air movements, and other
factors which may have caused erratic trapping efficiency in these
sampling devices.
8.
A fluorescent dye was added to the guthion and dithane mixture in
an attempt to determine pesticide drift patterns. Greenburg-Smith
impingers, high-volume air samplers, and mylar sheets were used to
collect air samples. Fluorescent analysis of the collected samples
showed the dye concentrations used were often undetectable because
of trapping inefficiency in the impingers or excess dirt (dust) in
the impactors~ The mylar sheet technique was successful in collecting
measurable amounts of dye used to trace the pesticide drift.
9.
Tracing pesticide drift patterns by visible spot deposits on oi1-
sensitive photographic papers (Kromecote cards) placed in and
around the potato field was unsuccessful. Subsequent evaluation of
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6
this technique indicated two possible reasons for the lack of
success: (l) cards were underexposed to ultraviolet light, thus
preventing development of the visible spots, and {2} spray droplets
contained insufficient oil-based ingredients to chemically react
with the photographic paper.
10.
Drift patterns were documented by examining particles impinged upon
glass slides coated with magnesium oxide. Droplet sizes, derived
from microscopic examination of the slides, ranged from 126 to
289 ~m for a drift potential of 5 to 11.5 meters. Although complete
drift control is not achievable, it is concluded that the 07-45
nozzle used would produce droplets greater than approximately
125 ~m and minimize potential drift.
11.
Efficacy of the guthion treatment,
average kill, was considered to be
area studied.
88.5% as determined by the
about the average for the geographic
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III.
DESCRIPTION OF STUDY AREA
Field studies were conducted on a potato-producing farm near Magnolia,
Delaware. The cooperating farmer was engaged in general farming practices
with principal crops being potatoes and soybeans.
/'
'-... '
The study site'was a 34.6 hectare (85.5 acre) field in which 16
hectares (39.6 acres) were planted in potatoes and the remaining acreage
in soybeans. Private residences, county roads, an unoccupied migrant
labor camp, a commercial chicken farm, grainfields, woodlands and a
small unnamed creek bordered the study site [Fig. lJ.
Twenty-three sampling stations were established for the study:
nine stations on the potato field; twelve stations off the field and two
stations in the creek. Samples of air were collected from the potato
field and surrounding land for pesticide drift analyses. Additionally,
water and sediment were collected from the two creek stations for pesticide
residue analyses.
The pesticide was applied by a local aerial applicator. The flying
service facility, about a half mile east of the study farm [Fig. lJ,
included a warehouse for pesticide storage, a mixing and loading area,
an aircraft maintenance area and hangar space for three Grumman Ag-Cat
aircraft. Immediately behind the warehouse was a fenced enclosure where
used pesticide containers were stored. Corporate offices were located
near the hangar.
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Figure 1.
Location of Potato Field Study Site, Kent County, Delaware
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IV.
USE OBSERVATIONS
PRE-APPLICATION
Insect Infestation Assessment
Prior to pesticide treatment of a crop it is necessary to:
(1) identify the pest or disease, (2) determine the extent of the
infestation, and (3) select the appropriate control methods or materials.
On June 1, 1976, University of Delaware entomologists examined the
potato field. In their survey, a random sampling of four areas within
the field, they walked fifty paces along a plant row into the field,
made insect counts on 10 plants, then walked across 12 to 13 rows and
counted insects on an additional 10 plants. Finally, they walked back
to the field border and made insect counts on 10 plants at the edge of
the field.
Results revealed large numbers of Colorado potato beetles
(Leptinotarsa decimlineata [SayJ). The insect counts averaged from 2.1
to 22.8 beetles per potato plant. According to the University of
Delaware entomologists this exceeded the population density of two
insects per linear foot of each planted row, which constitutes a serious
infestation. As a result, chemical control using a mixture of Guthion
2-S and Dithane (M-45) was recommended. The guthion, a non-systemic
organophosphate insecticide, was predicted to kill 80 to 90% of the
potato beetles. The dithane, a fungicide, was recommended to prevent
the development of potato blight.
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Aerial Applicator - Preparation and Evaluation
Prior to the June 4, 1976 application of guthion and dithane to the
study site, NEIC and Region III personnel observed the operational
procedure of the aerial applicator in preparing the pesticide material.
Standard procedure consisted of pre-mixing the pesticides with
water prior to loading them into the aircraft. Pre-mixing was accomplished
by use of a specially designed 1,135.5-liter (300-gallon) circular
fiberglass tank, with a built-in agitation system. Other features
included a bottom draw device with the necessary pumps and hoses for
filling the aircraft, a quick disconnect or shut-off system for the
hose, and exterior markings which graduated the tank into 19-1iter
(5-gallon) segments [Fig. 2].
/
Mixing the material used in this study consisted of putting about
75 liters (20 gallons) of water in the tank and starting the agitator.
After about five minutes, a pre-weighed amount (27 kg) of 80% dithane
and additional water were added to the tank. From rubber buckets,
containing 38 liters (10 gallons) of 22% guthion were added to the tank
and the mixture was diluted with water. Then, empty dithane bags,
~
guthion cans and the rubber buckets were triple rinsed, and the rinse
water was added to the tank. . At this time, the Rhodamine WT dye used
for tracer studies was added. ~
The material was agitated for 15 minutes before pumping it into the
aircraft. After the tank was drained, an additional 75 liters
(20 gallons) of water was added, agitated for five minutes (to wash the
tank of guthion and dithane residues) and pumped into the aircraft. The
final volume was 908 liters (240 gallons) of diluted material.
This mixture provided for an application rate of 22.7 liters/hectare
(6 gallons/acre), with an actual active ingredient of 0.47 liter
(1 pint) of guthion and 0.54 kg (1.2 1b) of dithane per acre as specified
on the product labels.
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Figure 2.
Mixing pesticide materials prior to application.
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Company policy of the aerial applicator dictated that employees
involved in the mixing and loading operations wear safety clothing
consisting of hats, rubber aprons, trousers, boots, gloves, goggles and
canister-type respirators. The mode of dress worn by EPA personnel is
shown in Figure 3. Aircraft pilots were not permitted to participate in
the loading and mixing operation. Company employees did not have routine
acetylcholin-esterase (AChE) evaluations, which would demonstrate damage
to nervous functions induced by organo-phosphate, pesticide exposure.
In view of the fact that many compounds used by this applicator are
AChE-inhibiting agents, such medical checks should be routinely performed.
While not directly related to the mixing operation, observations
were made of the pesticide storage area. Pesticide materials were
arranged acc~rding to basic types of compounds (herbicides, insecticides,
etc.) and further segregated into specific types and brands. Bags, cans
and drums were properly organized, with well-defined passageways available
to provide adequate working -space.
The warehouse was kept under security conditions. All doors were
plaingly marked to indicate the contents, witH abundant signs for "No
Smoking" and "Authorized Personnel Only. II The applicator indicated he
was making every effort to comply with all pertinent Operational Safety
and Health Administration (OSHA) requirements.
During the pre-application phase, only one area of concern was
noted: the applicator allowed non-Company individuals without safety
gear to be present during mixing operations. While. not in violation of
EPA regulations, this practice can lead to exposure of these individuals
to toxic materials.
Prior to pesticide application, water and sediment samples were
collected from two stations in the creek [Fig. 4J, while samples of the
undiluted and diluted pesticides were obtained during the mixing operation.
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Figure 3.
Safety clothing worn by EPA personnel (foot and lower leg covering not
shown).
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To evaluate spray drift characteristics, five types of sampling
gear were placed in and around the field: a device using the Greenburg-
Smith impinger system [Fig. 5J; a high-volume air sampler [Fig. 6J;
mylar sheets, Kromecote cards and glass slides coated with magnesium
oxide [Fig. 7J. Additionally, each member of the EPA team carried a
small, portable, monitoring device designed to determine personal exposure
to airborne pesticides. Each system is described in detail in the
Appendix.
Impinger units were placed at four stations on the field and seven
stations off the field [Fig. 4]. High-volume air samplers shared four
of the off-field locations. Tracer dye sheets of mylar were placed at
all stations except 1,9 and 23. Magnesium oxide slides and Kromecote
cards were placed at 15 stations.
Station selection for assessing spray drift characteristics was
governed by prevailing wind direction and adequate coverage in the event
of variable wind direction.
APPLICATION
Observations
Chemical treatment of the study field occurred during the early
morning hours on June 4 and 5, 1976. The second day of spraying was
required when the wind velocity of June 4 increased to unacceptable
velocities and the pilot discontinued spraying.
Weather conditions were recorded 7.2 kilometers (4.5 miles) from
the study site at Dover Air Force Base. At 6:54 a.m. (EDT) on June 4
the report was: scattered clouds at 7,010 meters (23,000 feet), air
temperature of 13.4°C, dew point 10.5°C, winds at 12.9 km/hr (8 mph)
.from the NNE, barometric pressure 30.23 mm Hg, and a relative humidity
of 83%.
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Figure 5.
Air sampling device using
Greenburg-Smith impinger
system.
Figure 6.
High-volume air sampling
device.
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Figure 7.
To evaluate spray drift characteristics, a Kromecote card
is surrounded by magnesium oxide slides and a mylar
sheet is placed on the ground.
-"
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An aircraft equipped with a 36-nozzle spray boom was used to apply
the guthion and dithane mixture on the potato field [Fig. 8]. The cone-
type spray nozzles (07-45; i.e. 7/64-inch orifice diameter and a number
45 whirl-plate) were directed with the air stream. Boom pressure was
set at 4.2 kg/cm2 (60 psi). To treat the 16 hectare (39.6 acre) field,
a total of 908 liters (240 gallons) of the pesticide mixture was pumped
into the spray tank of the aircraft. .
Aerial spraying began at 6:45 a.m. (EDT) on June 4, 1976. The
aircraft approache~ the south edge of the potato field and the pilot
leveled the aircraft so the spray boom height was approximately. 2.4
meters (8 feet) above the field. Passes were made in a west-to-east and
east-to-west direction, parallel to the potato rows. At the completion
of each pass, a tissue paper streamer was released from the aircraft to
visually mark the swath completed. This marker was used by the pilot as
a reference point for the beginning of the next pass [Fig. 9]. During
each pass, pesticide in a swath about 12 meters (40 feet) wide was
sprayed over the potato crop.
The wind velocity noticeably increased about 7 a.m., at which time
the pilot lowered his flight path to a boom height of about 2 meters
~6 feet) above the ground to minimize spray drift. Later, during an
interview with the pilot, the EPA observers learned that the pilot
lowered his flight path in order to spray as much of the field as
possible, with minimum spray drift, before weather conditions forced the
aerial application to be discontinued.
Spraying continued at the 2-meter boom height until 7:05
increasing wind velocities required cessation of operations.
two-thirds of the field had been treated during the 18 passes
before the sprayingoepration was discontinued.
a.m. when
Approximately
made
The application was evaluated by 2-man teams of EPA observers.
teams were situated at the corners of the potato field. Each member
The
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Figure 8.
A Grumman Ag-Cat airplane applying
pesticides at low level for the control of
Colorado potato beetles.
Figure 9.
Streamer used to mark the completion of
one spray pass and the initiation of another.
...
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used an observation checklist to record the spraying activities. Two
teams were equipped with telephoto cameras. Photographs were taken for
subsequent analyses and verificaiton of aircraft flight patterns and a
record of visible spray cloud patterns [Fig. 10].
During this operation three instances of visible drift were observed
by the EPA teams. The first drift was recorded while an east-to-west
pass was flown between stations 10 and 16 [Fig. 4]. The drift cloud was
observed passing into the woods. Observers reported this occurred when
the aircraft was rotated upward at a severe angle to miss the trees.
The second drift occurred at the north end of the field, again as the
aircraft rotated upward at the completion of a pass. A light mist
drifted 3 to 4.5 meters into an adjacent soybean field. The third off-
field drift pattern was at the southeast corner of the field. As the
aircraft swerved to miss a power pole, a light drift cloud crossed the
roadway.
The following day at 6:14 a.m. (EDT) the aerial applicator resumed
spraying the potato field. Weather conditions recorded at the Dover Air
Force Base at 5:55 a.m. (EDT) on June 5 were: clear sky, 16 km (10 mi)
visibility, air temperature 11.6°C, dew point 7.2°C, wind from the N at
8 km/hr (5 mph), barometric pressure 30.34 mm Hg, and a relative humidity
of 74%.
Spray passes were made north-to-south and south-to-north. No
visible drift off the field was observed during the eleven passes made
to treat and trim the remaining two-thirds of the potato field.
Evaluations
Observations by EPA of the 2-day application led to the following
conclusions: pesticides released during aerial application were subject
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Figure 10.
Aerial pesticide application at the 2.5 meter flight level showing the
aircraft wingtip vortices.
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to drift from the potato field as a direct result of aircraft turbulence
(wingtip vortices) and aerial transport by atmospheric movement.
Meteorological conditions which most affect drift are wind direction and
velocity, turbulence, relative humidity, air temperature, and atmospheric
stability. Additionally, the size and nature of spray droplets are
directly related to drift potential. Each of these factors is examined
below.
Wind Direction and Velocity
The direction the wind is blowing determines the direction of
drift. Wind speed varies as atmospheric stability conditions change,
thus causing the lateral movement of spray particles in the air.! In
these studies the low average wind speeds were important in minimizing
drift; however, when the wind speed increased to 12.9 km/hr the morning
of June 4, the potential for drift increased.
Turbulence
Turbulence is a series of horizontal and vertical gusts and lulls,
and random eddy movements of the air. It is dependent upon ground
roughness, mean wind speed, thermal stability of the air, and aircraft
movement.! Turbulence is considered one of the most important factors
affecting drift. Airborne pesticide droplets are reported to be transported
the greatest distances by the combined forces of gravity, wind speed,
and turbulence.
Relative Humidity and Air Temperatures
Relative humidity from 74 to 83% combined with moderate air temperatures'
of 11.6 to 13.4°C were measured during the application. These combined
factors would reduce the evaporation rates of the water-based pesticide
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droplets and the drift potentia1.l The average volume median diameter
(VMD)* of the droplets sprayed on the potato field was 148.2 ~m.
(Drift potential for these droplets will be discussed under Spray Droplet
Characteristics.)
Atmospheric Stability
The morning of June 4, the atmospheric stability** was calculated to
be 0.19 (based on data obtained from the Dover Air Force weather station).
In character the conditions were variable. Initially, winds were of low
velocity, and velocity gradients and vertical turbulence would have been
minimized.l During the spraying, the atmospheric stability changed to a
a lapse or unstable condition. Wind speed increased and the spraying
operation was discontinued.
On June 5, the atmospheric conditions were reported by the Dover
Air Force Base weather bureau to be stable. Atmospheric stability was
calculated to be 0.82. This condition was characterized by low wind
speed, minor changes in the velocity gradient, and mild vertical turbulence.
Spray drift would be minimized by these favorable weather conditions.
Spray Droplet Characteristics
Of greatest importance to controlling drift are the size and nature
of the spray droplet.l The principal factor affecting drift appears to
be the number of drops smaller than 125 ~m (micrometers). If droplets
were restricted to 125 ~m or larger, pesticide applications would be
effective and drift would be minimized. On-site observations and sampling
* VMD is that volume ~hich divides the droplet diameter into ~o equal
parts, one-half above and one-half belo~ the median or 50% cumulative
point. .
** Stability is mathematically given as: very stable >1.2, stable 0.1
to 1.2, neutral -0.1 to 0.1 and unstable less than -0.1.
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revealed that the water-base spray evaporated rapidly, usually within an
hour. Small particles of the spray, consisting of active chemical plus
solvents, emulsifiers and carriers, drifted downwind. The drops below
50 ~m could have been carried for many miles, especially on June 4 when
the brisk air currents began. This was prevented, however, when the
pilot postponed the remainder of the spraying until the next morning.
Because both days of spraying were conducted during good meteorological
conditions, the drifting spray cloud did not appear to dilute vertically.
It remained low and close to the ground, permitting slowly settling
drops to concentrate on the potato crop.
The aircraft's cone-type nozzles (D7-45) produced a medium-to-
coarse spray. The VMD of the droplets produced ranged from 300 to 400
~m. With drops this size, an estimated 70 to 90% of the pesticide
mixture should settle to the ground within a distance of 378 meters
downwind.l Therefore, 10 to 30% of the chemical applied to the downwind
edge of the field theoretically would not deposit within the field, but
would move to nearby fields and to greater distances even under ideal
meteorological conditions. Data generated by this study indicate that
only minor drift passed beyond the field borders.
From this pesticide use observation study and an associated literature
search, it has become evident that complete drift control (no loss beyond
treated field) cannot be achieved with any device, additive or system.
commercially available. However, drift can be minimized by using coarse
sprays. When a fixed wing aircraft uses large orifices, and whirl plate
cone nozzles which are directed with the airstream, coarse sprays can be
achieved. Apparently, maintaining the pesticide application volume at a
minimum of 9.2 liters/hectare (6 gallons/acre) will also reduce drift.
Weather conditions must be considered during spraying operations
when no wind is blowing or when an inversion occurs close to the ground.
Drift is minimized when coarse sprays are applied under mildly ventilating
conditions; calm inversion-type weather will lead to increased drift.l
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POST-APPLICATION
Aerial Applicator - Clean-up and Disposal
Procedures for the clean-up of used containers, as practiced by the
applicator, followed closely the recommended EPA guidelines: all containers
(bags, cans, drums, etc.) were triple-rinsed (with the rinse water being
added to the spray material), punctured, and stored in a fenced, security
area near the warehouse.
Used containers are temporarily stored on-site. When a sufficient
number of containers has been collected to justify the cost, they are
hauled to a local landfill site to be buried. Unused, undiluted material
(e.g., a partially used 5-gallon can of an insecticide) frequently is
recapped and returned to the warehouse for future use.
Disposal of containers and unused, undiluted and diluted pesticides
poses a problem in Delaware. The State does not have a dump site especially
designed for the disposal of highly toxic or environmentally damaging
compounds or containers, referred to as a Class I dump site by other
States. It is recommended that such a site be established.
Container disposal presented a problem for both the applicator and
the cooperating farmer. Numerous empty pesticide containers (cans,
drums and bags) were observed to have been previously disposed of in an
open dump along the creek near the potato field study site [Fig. 11].
Storage and disposal of diluted material by the applicator also
presented a problem. Since weather conditions prevented spraying the
study field in a single day, the applicator returned to the airstrip
with about 378 liters (100 gallons) of material still aboard. To prevent
the mix from settling and possibly clogging the spray nozzles, the
material was pumped from the aircraft back into the mixing tank for
storage. The following day the mixture was reintroduced into the aircraft
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26
Figure 11.
Used pesticide containers found at uncontrolled dump site on study
farm.
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27
to finjsh spraying. However, problems arise when conditions prevent
complete use of the diluted material and the mixing tank is needed to
prepare a different compound.
Pesticide residue in the aircraft spray tank posed another disposal
problem. About 19 liters of material remained in the spray tank, booms
and nozzles. The applicator drained as much as possible from the plane
and added about 76 liters of water to the spray tank, turned on the
spray system, with only enough pressure to force the water through the
. booms and nozzles, and allowed this water to flush and clean the system.
The water flowed into a grate-covered drain at the loading area which
extends about 91 meters into an unused pasture [Fig. 1], terminating in
a specially prepared limestone-filled leach field. Another technique
occasionally used by the applicator is to put 76 to 95 liters of water in
the tank and spray this solution over the field treated with the parent
mix. However, distance from the airstrip to the field, costs and time,
as well as the possibility of exceeding the recommended treatment level,
often prevents the use of this technique.
EPA Post-Application Sampling
Post-application sampling consisted of obtaining additional soil
and vegetation samples from 21 stations in and around the study field
[Fig. 4J, along with additional samples of fish, water, sediment and
aquatic vegetation from the stations in the creek. These samples were
collected for analyses in the event of an accident, spill, or major
drift losses from the field. Also, at this time, the sampling systems
used to evaluate drift characteristics were removed from their field
locations.
Analyses of drift deposits are presented in Table 1, for water and
sediment samples from the creek, and for air samples collected in the
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28
TabZe 1
IMPINGER~ PERSONNEL MONITOR~ WATER AND SEDIMENT
ANALYTICAL DATA (GUTHION)
. June 1976
Station
Sample Type
Concentration
11g
23
23
Water
Sediment
Ethylene glycol (impinger)
2
3
4
6
7
9
10
18
19
21
22
Tube
No.
1
2
Charcoal tube (Personnel monitor)
3
7
11
12
15
16 .
17
18
15 11g/1
t
N.D.
11g/m1
1.2
1.7
1.5
2.1
2.3
1.5
3.7
1.1
2.3
1.9
1.3
11g
Ftt < 1
Bttt. <1
F <1
B <1
F 1.0
B 2.0
F <1.0
B <1.0
F <1.0
B 1.0
F <1.0
B <1.0
F <1.0
B <1.0
F <1.0
B 1.4
F <1.0
B <1.0
F <1.0
B 2.0
t N.D. = Not detected
tt Front section
ttt Back section
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29
impinger system and the personnel monitors. Table 2 presents data on
the magnesium oxide slides, with Table 3 showing results obtained with
mylar sheets and the high-volume air sampler.
No guthion was found in water or sediment samples from the creek,
indicating that no drift had penetrated the woods that deeply. At on-field
locations the impinger system collected a range of 1.1 ~g guthion/ml of
ethylene glycol at Station 18 to 3.7 ~g guthion/ml of ethylene glycol at
Station 10. Off-field locations were generally lower, with 1.2 ~g
guthion/ml of ethylene glycol at Station 2 and ranged upward to 2.3
~g guthion/ml of ethylene glycol at Station 19. The off-field values
are due primarily to overspray and turbulence. Minor amounts of drift
were observed also.
Personnel monitors worn by the EPA team collected a maximum of 2
~g of guthion and ranged downward to <1 ~g (minimum detection limits).
Highest concentrations were found in the monitors worn by the EPA
Consumer Safety Officer during the mixing operations and by a team
member retrieving sampling equipment from the field two to three hours
after spraying. Other detectable values, 1.0 ~g and 1.4 ~g of guthion,
were recorded eight hours after treatment, again by EPA personnel who
entered the treated field. All EPA personnel who entered the study site
during the first 24 hours after treatment wore complete safety gear,
consisting of hats, respirators, rubber gloves, long-sleeved coveralls
and plastic foot coverings. Label requirements for guthion prohibit re-
entry within 24 hours without safety clothing.
To evaluate drift characteristics, a Rhodamine WT dye solution was
added to the guthion and dithane mix to provide a final dye concentration
of 100 ~g/l. Three types of equipment were used to monitor the dye, the
Greenburg-Smith impinger systems, a high-volume air sampler) and mylar
sheets. The dye was used in a qualitative manner, the interest being
only in the presence or absence of the dye. The numbers used have no
absolute meaning; the differences between numbers are indicative of
greater or lesser amounts of dye at one location as compared to another.
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30
Table 2
RESULTS OF MAGNESIUM OXIDE SLIDES
Kent County~ Delaware
June 1976
Station VMDt Calculated Drift
~m Distancett
m
2 159 7
3 No drops present
4 98 23
5 103 15.5
7 126 11.5
8 No drops present
9 61 43
14 24 305
15 335 4
17 289 5
19 No drops present
20 115 12
21 172 6
22 No drops present
t VMD = volume median diameter: that value ~hich divides the droplet
diameter into t~o equal parts~ one-half above and one-half belo~
the median or 50% cumulative point.
tt Rumker~ et al.~ 1975 (Ref. 1)
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31
Table 3
DYE ANALYSIS OF. MYLAR SHEETS AND CASCADE IMPACTORS
Kent County, Delaware
June 1976
Station
Type
Va 1 ue t
Fluorescent Units
Mylar Sheet
2
3
4
5
6
7
8
10
11
12
13
14
15
16
17
18
19
20
21
22
4
9
19
21
High-volume air sampler
14.5
17.0
14.5
17.5
23.5
17.5
14.0
72.5
20.5
18.0
48.5
19.0
33.0
48.5
32.5
14.0
18.0
16.0
15.0
30.0
68.0
80.5
59.5
56.5
t These values have no absolute meaning, only the
differences between numbers are indicative of
greater or lesser amounts of dye at one location
as compared to another location.
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32
The Greenburg-Smith impingers collected generally higher dye
concentrations at the north end of the field than at the south end.
Values at Stations 2,3 and 4 were 28.5,35.0 and 51.0 fluorescent
units, respectively; Stations 19, 21 and 22 had values of 20.0, 26.5 and
39.0 units, respectively. These differences were due primarily to
sampler placement about the field and reflect the effect of turbulence
more than drift.
The high-volume air sampler proved to be of little value in evaluating
drift of dye, primarily because the instrument is designed to collect
particulate matter (dust, etc.). During this study, the volume of dust
collected masked the identification of the dye residue.
Mylar sheets, placed horizontally on the ground, showed minimal
drift off the field except at two locations [Table 3J. Station 15 had a
.' .
high value (33.0 fluorescent units) because the aircraft spraying system
was not turned off quickly enough at the completion of the pass and the
material drifted into the woods. The higher value at Station 22
(30.0 units) occurred during the field trimming operation and resulted
when the aircraft pulled up at the completion of the pass and the spray
cloud, released at a slightly higher elevation, drifted off the field.
To fully evaluate the drift characteristics in the spray discharge
of the aircraft, it was necessary to sample the airborne drops. Two
sampling devices were used: magnesium oxide (MgO) coated microscope
slides and Kromecote cards.
Four slides, held in vertical positions and facing the four cardinal
. L~
directions [Fig. 71, were placed at ~ stations around the field. The
airborne drops impinged on the MgO coating, leaving a crater after
evaporation of the liquid. In this study, the method devised by Rathburn2
was used to calculate droplet diameters and the volume mean diameter. These
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33
values also served to determine the theoretical distance that spray
droplets measured in this study would drift.l
Ten of the fifteen MgO slide sites had positive hits by spray drops
[Table 2]. The largest drop sizes occurred on the field, with Station
17 showing a VMD of 289 ~m. The smallest drops were recorded at Station
14. For undetermined reasons, the average VMD of the south end of the
field was about 2.3 times that of the north end. The droplets on the
field traveled from 5 meters (VMD of 289 ~m at Station 17) to 11.5
meters (VMD of 126 ~m at Station 7). The smaller droplets falling off-
field (VMD of 24 ~m at Station 14) were estimated to drift a maximum
distance of 305 meters.
These values indicated the nozzles of the applicator's aircraft
were of sufficient size (07-45 nozzles with 7/64-inch orifices) to
prevent major drift, when combined with the weather conditions and
flight characteristics described in this report.
Kromecote cards were placed at all stations, except 1 and 23, with
the intent of catching and retaining spray droplets for later measurement.
However, no drops were observed on the cards after the completion of
spraying operations. Subsequent evaluation indicated two probable
reasons for the lack of success: (1) the cards were underexposed to
ultraviolet light, preventing development of the visible spots, and (2)
spray droplets contained too little oil-based active ingredients to
chemically react with the photographic paper.
Pesticide Efficacy
To determine the efficacy of the guthion treatment, the field was
inspected three days after treatment by a University of Delaware Extension
Service entomologist. The following tabulation of insect counts from
four randomly selected sites illustrates the results.
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34
June 1,1976 June 8, 1976 Kill
Pre-application Post-application %
21 2 91
49 0 100
182 36 81
228 43 82
The average kill was 88.5%, considered by the entomologist to be
about average in that geographic area.
No data were collected on the efficacy of the dithane treatment.
EVALUATION OF OBSERVATION METHODS
An objective of this study was to assess methods to scientifically
document the environmental hazards associated with the use of pesticides.
To achieve that objective, several methods and sampling systems were
tested. Those which proved most useful were: (1) observers equipped
with cameras; (2) mylar sheets to collect tracer dye; and (3) magnesium
oxide slides to determine drift of spray droplets.
The application program was visually observed and areas of concern
were noted. Drift was recorded through the use of dye tracers and spray
droplet size, and hence the drift distances were determined with a
minimum use of time and manpower. Formulation testing was important
because it provided the analysis of the undiluted and diluted material
for comparison with labeling and other applicable regulations.
The impinger devices had limited value. The principal problem was
the variable trapping efficiency. The devices were aslo affected by
temperature and the concentration and partial pressures of the pesticides.
However, impingers are one of the few tools available for semi-quantitative
sampling of airborne pesticides.
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35
The high-volume air samplers were considered a good tool for sampling
airborne particlest but in this study the dust masked the tracer dyet
thus limiting their usefulness. Kromecote cards proved to be unsuitable
under the weather conditions and with the type of pesticides applied
during this study.
Minimal drift observed during this study precluded residue analysis
of the soil and vegetation samples. Howevert if drift was greater or an
accident had occurredt analyses of soil and vegetation samples would
enable the EPA to more effectively assess the environmental effects.
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36
REFERENCES
1.
R. 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, 240 p.
2.
C. B. Rathburn, 1970. Methods of assessing droplet size of in-
secticidal sprays and fogs. Mosquito News, 30(4): 501-513.
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Appendix
Description of Sampling Devices and Methods
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38
DESCRIPTION OF SAMPLING DEVICES AND METHODS
A variety of techniques were used to evaluate spray drift character-
istics during this study. Principai emphasis was placed on the use of
Rhodamine WT dye as a tracer compound, mixed with the sprayed material.
The selection of the tracer material was based on the following
desirable characteristics:
1.
2.
High sensitivity, measurements down to 0.01 microgram (~g)
Rapid analysis available
3.
Soluble in spray mixture with minimum physical effect on
atomization and droplet evaporation
4.
Distinctive property to differentiate from background or
naturally occurring substances
5.
Stable or predictable concentration relationships under
environments encountered
6.
7.
Moderate cost
Non-toxic
Rapid analysis of micro-concentrations of fluorescent solutions was
attained with a Turner model 111 fluorometer. This instrument has a
primary filter to select the excitation wavelength from an ultraviolet
lamp source (GE No. F4T4/BL or G4T4/1). The secondary filter and photo-
multiplier tube are mounted at right angles to the primary source. The
secondary filter was selected to absorb any stray ultraviolet light
and, furthermore, to restrict any background fluorescent response that
occurs at a wavelength different from the fluorescent sample. The
photomultiplier tube, type 931A, has an S-4 response which is sensitive
to wavelengths from 300 to 700 ~m (micrometers). All dye study analyses
were performed in a field laboratory.
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39
One system used to collect the insecticide and dye mixture was
mylar sheets (a type of plastic commonly used by draftsmen)~ 4 x 12 in.
x 5 mils thick~ placed horizontally on the ground. The dye retained on
these sheets was evidence of spray drift.
Relatively rapid processing techniques were developed for preparing
the samples for analysis. To wash each mylar samp1e~ 100 ml of 95%
ethyl alcohol was used. Approximately 25 ml of each solution was
subsamp1ed~ and a 5 ml sample was poured into matched cuvettes and in
turn placed in the Turner fluorometer for measuring the fluorescent
response. Previous tests verified that nearly all of the dye was
recovered from the mylar sheets with the above laboratory procedure.
A second system used, the high-volume air sampler, uses a fiberglass
filter, 20 x 25.4 cm, on which airborne particles are trapped. In this
study~ the filters were used to trap the spray droplets, retaining the
dye while the liquid phase evaporated. In use, about 0.99 m3 (35 ft3)/min
of air was pulled through the filter. The system was operated for about
1 hour before spraying to about 4 hours after spraying. A total of
about 297 m3 (10,500 ft3) of air passed through each filter. Processing
of the filters followed the same procedure as the mylar sheets.
The third system used for dye studies~ the Greenburg-Smith impinger,
also served as a means of semi-quantitating pesticide levels in the
drift. This system contains a pump that draws air through a sampling
train and auxiliary equipment to control and measure air flow, switching
the flow from one sampling train to another after a pre-set interval.
(a)
Sampling train - Each sampling train contains an impinger
containing 100 ml of ethylene glycol to trap particulates and
gases and an absorption tube packed with a plug of glass wool
to remove any sp1ashover or water condensation.
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40
(b)
Flow control and pump - After the air has been pulled through
the sampling train, it passes through a solenoid valve controlled
by a timer, through a control valve by which the air flow in
the sampling train may be set at the desired rate as shown on
a flowmeter, through the flowmeter, and finally through the
vacuum pump. A momentary contact switch may be closed to
switch the air flow to a particular sampling train so that its
flow may be adjusted to read any time.
Each unit was given a station number and was used only at that
station. The impingers were filled with approximately 100 ml of ethylene
glycol. Flow rates were set for 0.9 standard ft3/min. Pesticide-free
aluminum foil was used to cover the air intake tubes while transporting
the units to their sampling locations in the fields.
The sampling units shut off automatically after 48 hours. The
units were then transported to the servicing area and disassembled. The
ethylene glycol was removed from the sampling trains and transferred to
250 ml screw-cap glass bottles. Impingers were rinsed with approximately
25 ml ethylene glycol which was added to the samples. The bottles were
appropriately labele~and stored in an ice chest for transportation to
the field laboratory where a 25 ml aliquot was removed and analyzed for
dye concentrations. The remaining sample was shipped to the Denver NEIC
laboratory for further chemical analysis.
The final two devices used, magnesium oxide coated microscope
slides, and Kromecote cards did not sample the dye but rather the
droplet itself.
The slide is prepared by burning strip magnesium beneath the slide .'
to form a white powdery coating, which was slightly deeper than the
largest droplet diameter. Upon impaction with the stationary slide the
airborne droplets make a crater, leaving visible evidence even after
evaporation.
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41
Craters, caused by the droplets, were measured to the nearest
micron by use of a microscope, measuring 200 craters on each slide used.
These data were then used to compute the VMD and allow estimates to be
made of drift distance. 1
Kromecote cards, consisting of a special white oil-sensitive
coating, 4 x 5 in., were used in a manner similar to MgO slides. The
spray droplets impinge on the card, leaving a discolored area approximately
the size of the spray droplet. Had the cards been successful, they too
would have allowed the computation of a VMD to confirm and support data
derived from MgO slides.
Personnel monitors contained
charcoal and lightly capped with
was used to assess the degree of
a glass capsule filled with activated
fiberglass. Analysis of the contents
pesticide exposure to the observers.
Environmental samples (soil, vegetation and aquatic life) were
collected by standard methods.
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