ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF ENFORCEMENT
EPA-330/2-77-001
PESTICIDE USE OBSERVATIONS
IMPERIAL VALLEY, CALIFORNIA
(AUGUST 22- 31, 1976)
ENFORCEMENT INVESTIGATIONS CENTER
DENVER, COLORADO
JANUARY 1977
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Environmental Protection Agency
Office of Enforcement
EPA-330/2-77-001
PESTICIDE USE OBSERVATIONS
IMPERIAL VALLEY, CALIFORNIA
August 22-31, 1976
January 1977
National Enforcement Investigations Center
Denver, Colorado
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CONTENTS
I INTRODUCTION.. . . . . . . . .
II SUMMARY AND CONCLUSIONS.
. . . . .
.....
1
3
......
GENERAL CONCLUSIONS. . . . . . . . . . . .. 3
SPECIFIC CONCLUSIONS. . . . . . . . . . .. 4
III BACKGROUND. . . . . . . .
. ... .
.....
7
IV DESCRIPTION OF STUDY AREAS.
. . . . .
. . . 11
V DISCUSSION AND RESULTS. . . . . . . . . . . 17
PRE-APPLICATION FIELD "A". . . . . . . . . . 17.
APPLICATION FIELD "A" ........... 29
POST APPLICATION FIELD "A" . . . . . . . . . 32
PRE..APPLICATION FIELD "B" ........ . 38
APPLICATION FIELD "B". . . . . . . . . . . . 44 .
POST APPLICATION FIELD liB" . . . . . . . . . 48 .
METROPOLITAN DRIFT POTENTIAL. . . . . . . . 57
VI EVALUATION OF METHODS. . . . . .
. . . . . . 61
AIR SAMPLING DEVICES. . . . . . . . . . . . 61
FLUORESCENT TRACER TECHNIQUES. . . . . . . 61
MAGNESIUM-OXIDE-COATED SLIDES. . . . . . . 62
SPRAY DROPLET CARDS. . . . . . . . . . . . 62
ENVIRONMENTAL SAMPLING. . . ... . . . . . . 63
OBSERVATION AND PHOTOGRAPHS. . . . . . .'. . 64
REFERENCES
APPENDIX
.........
. . . . . . . . 65
DESCRIPTION OF SAMPLING DEVICES AND METHODS. 67
iii
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Tables
} Sampling Stations and Devices, Field "A" . .
2 Sampling Stations and Devices, Field "B" . 0'
3 Pesticide Concentrations Applied, Field "A".
4 Spray Droplet Counts, Field "A".. 0'..0.
5 Pesticide Residue Analyses, Field "A" '
6 Spray Droplet Counts, Fiel d "B" .. 0 . 0 0
7 Pesticide Residue Analyses, Field "B"
8 Metropolitan High~Volume Air Samplers
Figures
1 Imperi a 1 Valley 0 . . 0 0 0 . 0 0 0 0 0 0 0
2 Map of Fiel d "A" . 0 0 0 0 . 0 . . 0 0 0 0 0
3 ~'ap of Field "B" . . . . . 0 0 0 . 0 0 0 0 .
4 Pheremone trap. . . . . . 0 . 0 0 . . 0 0 .
5 Evaluating insect infestation. 0 0 0 0 0 0
6 Pesticide storage facility. . . . . 0 0 0 0
7 High Volume Air Sampler with lid raised
showing fiberglass filter 0 . 0 . . . 0 . 0 22
8 Greenburg-Smith air sampler with upper
cover assembly removed to expose impinger
train. . . . . . . ; . . . . . . 0 0 . 0 0 22
9 Pesticide container disposal site. . 0 o. 24
10 Fenced disposal site with perforated
containers awaiting burial. 0 . . . . . 0 0 24
11 Temporary storage and transport vehicle
designed to automatically unload empty
chemical containers. . . 0 0 . . 0 0 0 0 0 26
12 Hiller helicopter equipped with spray
boom. . . . 0 . 0 . 0 0 . 0 0 . . . . 0 o. 26
13 Protected worker examining spray droplet
ca rds . 0 . . . . . 0 . . 0 0 . . . 0 . 0 o. 30
14 Removing equipment from a recently sprayed
cotton field. . . 0 . 0 . 0 . 0 . 0 0 0 000 30
15 Meteorological Laboratory with 10-meter
temperature probe. . . . . . 0 . . 0 00 0 33-
16 ~1eteoro,logical unit with 2-meter
temperature probe, anemometer and
wind directional vane 0 . . . . . . 0 0 . 0 33
17 "Nurse Rig" with open hopper (arrow) and
mixing tank. . . . 0 . . . . . 0 . . 0 0 0 41
18 Close-up view of the open hopper showing
"Jet-Rinse" apparatus (arrow). 0 . . . 0 0 .' 41
19 Leach field for contaminated wash water 0 0 45
20 Temporary storage facility for used
pesticide containers. . . 0 0 . 0 . . 0 0 0 45
21 Visually enhanced droplet impressions on
Linagraph paper (X15). '0 . 0 0 0 0 . 0 0 0 0 51
2~ Visually enhanced pesticide spray droplets
on Linagraph cards (lOX) 0 0 0 . 0 0 0 0 0 0 55
iv
13
16
~7
35
36
49
53
59
8
12
14
18
19
20
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I.
INTRODUCTION
In the past three decades the agricultural industry has grown
increasingly dependent upon the use of chemical pesticides to maintain
and increase crop yields. While the use of these materials increases
annually, the accumulation of information useful for evaluating environmental
hazards resulting from pesticide use has not been extensive. To assess
the environmental hazards associated with pesticide use, the Environmental
Protection Agency (EPA) has initiated monitoring activities in several
parts of the country, the first phase of a National Pesticide Use
Observation Program. The Imperial Valley area of California was selected
to represent the southwestern agricultural region of the United States.
Two cotton fields -- a 5.5 ha (13.5 acre) field near Calipatria, and a
28.4 ha (70 acre) field near Brawley -- were chosen for use observation.
The primary objectives of the investigation were:
1.
Determine if pesticide use is consistent with the label and
other regulations.
2.
Determine if pesticides, when properly used, cause environmental
or health hazards.
3.
Assess the effectiveness of a commercial pest management
advisory program.
4.
Identify use observation techniques of value to EPA and other
pesticide regulatory agencies.
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2
A ten-day use observation study was begun on August 22, 1976.
Aerial application on the first field was made by helicopter on August
27 followed by an application on a second field by a fixed-wing aircraft
on August 29. Pesticide residue analyses of soil, sediment, water,
vegetation, and air were performed on samples gathered from the target
fields and the immediate surrounding areas. Drift characteristics were
defined by use of dye-tracer techniques and a variety of spray droplet
cards and impaction devices. In addition, tests were done to evaluate
the acetylcholinesterase (AChE) inhibition in channel catfish exposed
in-situ in drains, canals, and rivers near the test fields.
Procedures followed by pesticide applicators were observed to
determine if they: read and understood the product labels; followed
directions and precautions on the label; properly cleaned, stored, and
maintained application and safety equipment; and properly disposed of
used pesticide containers.
A joint cooperative effort was made by the National Enforcement
Investigations Center (NEIC) and the Imperial County Agricultural
Commission to assess the pesticide drift from agricultural areas into
the populated residential sectors of the Valley. Staff members of the
Agricultural Commissioner's Office collected three sets of high-volume
air samples within the city limits of Brawley, Ca1exico, and El Centro
during July and August. Chemical analyses of the samples for selected
pesticide residues were performed by NEIC.
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II.
SUMMARY AND CONCLUSIONS
During the summer months, cotton fields in Imperial Valley are
subject to infestations of pest organisms, principally the pink bollworm
(Peatinophora gOhhyp~eiia). Control of this insect requires intense and
repeated applications of various pesticides.
A field study was conducted by the National Enforcement Investigations
Center from August 22 to 31, 1976, to evaluate pesticide handling prior
to, during, and after treatment, and the effects of the treatments on
. the environment. Observations were made on the treatment of two cotton
fields: field IIAII, where the application was by helicopter; and field
11811, where treatment was by a fixed-wing aircraft.
A secondary investigation was conducted to determine if pesticide
drift was entering metropolitan areas of Imperial Valley.
GENERAL CONCLUSIONS
1.
Generally, pesticide use was consistent with label instructions
and other regulations.
2.
Although pesticides were applied properly, environmental and
health hazards occurred.
3.
The pest management program evaluated was beneficial economically
and environmentally.
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4
SPECIFIC CONCLUSIONS
The advisory firm responsible for the maintenance of both study
fields exercised sound judgment in the selection of appropriate pesticides
and application rates necessary for controlling the infestation of pest
organisms. These recommendations were consistent with label instructions
and Federal Regulations. The advisor further demonstrated obvious
concern about possible environmental contamination by delaying the
application of field "A" for 24 hours because of recent irrigation of
this field.
Inconsistencies observed pertaining to label instructions and
Federal Regulations were:
1.
Improper recommendations by the advisory firm of a 36-hour re-
entry time for field "A" (Federal Regulations specify a 48-
hour period for Azodrin@*) and a 3D-day delay period until
harvest for field "B" (the container label for Nudrin(R'i 1.8**
specifies a 4D-day delay period before harvest).
2.
The container label for Ethyl-Methyl Parathion 6-3E recommends
a re-entry time of 24 hours whereas Federal Regulations
require a 48-hour period for parathion.
The advisory firm is also a pesticide distributor and formulator.
Evaluation of this firm's premises showed storage facilities to be
clean, well ventilated, and orderly, with appropriate precautionary
signs visible.
* Azodrin([!)5 - EPA ReR. No. 201-157-AA-SheU Chemical Co.
** Nudrin@ 1. 8 - Reg. ~o. 00201-00347AA-SheU Chemical Co.
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5
Observations and interviews by EPA personnel indicated both applicators
were conscientious and well informed of the proper use of pesticides.
Spraying operations were halted whenever weather conditions deteriorated.
However, despite all efforts, potential environmental hazards occurred.
Substantial spray drift resulting from the application on field IIBII was
shown to intrude onto nearby sensitive crops, a private orchard, and
domestic dwellings. Analyses of ambient air samples of metropolitan
areas of Imperial Valley showed that translocation of pesticide material
I
into these areas does occur. Additional studies are required to assess
the impact of such intrusion.
Fish exposed in-situ in the drainage ditch bordering field IIAII
suffered AChE inhibition resulting from exposure to anti-cholinergic
compounds. Chemical analyses of water and sediment samples indicate
that the contamination probably resulted from surface or tile drainage
runoff, and not directly from pesticide drift.
The commercial pest management program evaluated during this study
proved to be economically and environmentallY beneficial. Crop damage
resulting from pest insects was observed to be minimal. Application
rates in all instances were less than the maximum allowable concentration
recommended by the container label, minimizing intrusion of pesticide
into the environment.
The procedures followed for handling, mixing and loading of pesticides
for both applications were adequate. Workers were well informed of
their duties and attired in appropriate safety apparel. All empty
pesticide containers were rinsed at the loading site and contaminated
water was added to the spray mixtures. Disposal of used pesticide
containers was facilitated by county maintenance of four secured and
posted container disposal sites. A similar disposal program should be
initiated in all agricultural areas where intensive pesticide application
is practiced.
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6
Comparative chemical analyses of pesticide mixtures from the mixing
tanks and the spray plane hoppers indicated that a loss of 14 to 25%
active pesticide ingredients occurred during the mixing and loading
operations. No specific cause for this phenomenon was determined.
Additional chemical analyses showed the pesticide mixture applied on
field IIAII to be contaminated with 0.02% of both methyl and ethyl parathion.
Clean-up facilities for applicating equipment ranged from no permanent
facility for the applicator of field IIAII, to a sloped concrete washing
area and a large leach field to contain all contaminated rinse water for
the field IIBII applicator.
I
I
I
Pesticide spray drift from the target area was variable. The
helicopter application on field IIAII resulted in no significant drift
beyond the target field. However, the application of field IIBII by
conventional aircraft resulted in substantial drift onto sensitive crops
and domestic areas. It was further determined that workers employed as
flaggers were exposed to pesticide drift. There is a need for better
definition of adequate safety apparel for these workers by EPA and
appropriate State regulatory agencies.
Immediately following the appl ication of field liB II , an appl ication
was made on the field directly to the west. Neither EPA or the landowner
was aware of this second application. Regulations are needed which
would require oral communication between the advisory firm and landowner
prior to any pesticide application. In the event that this is impossible,
the field should be conspicuously posted and dated indicating a safe re-
entry time.
Of the various techniques employed to detect spray drift, high-
volume air samplers and spray droplet cards were the most effective.
The use of spray droplet cards should be of particular interest to State
and local regulatory agencies because this technique involves little
monetary investment and has minimal manpower requirements.
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III.
BACKGROUND
Imperial County is located in the southwest corner of California
[Fig. 1J encompassing more than 10,800 km2 (4,200 mi2). The climate is
that of a true desert, with an annual rainfall of less than 7 cm (2.75
in). Approximately 182,000 ha (450,000 acres) are under irrigated
cultivation, making this the largest desert irrigation project in the
western hemisphere. Water is supplied entirely by the Colorado River by
way of the All-American Cana1.1,2
Salt accumulation in the soil of Imperial Valley has been a problem
for many years. This has resulted from a gradual increase in salinity
of the Colorado River water due to'sa1t loading and concentrating effects
upstream of Imperial Dam.3 Installation of a tile drainage system was
initiated in the 1920's in order to maintain a proper salt balance in
the soil. The system consists of tile drains 1.8 m (6 ft) beneath the
surface of cultivated fields spaced from 15 to 90 m (50 to'JOO ft)
apart. Approximately 32,000 km (20,000 mi) of such tiles are now installed
in Imperial Valley. When a field is irrigated, 10 to 25% more water is
applied than is required by the plants. This permits the excess fresh
water to pass through the soil to the 1.8 m (6 ft) level leaching out
accumulated salts. The leach water is then collected by more than 2,200
km (1,400 mi) of open ditch drains, and ultimately reaches a catch
basin, the Salton Sea, by way of the New and Alamo Rivers. At no point
in the system is irrigation return water mixed with incoming fresh canal
water. This system has proved successful in controlling the salt balance;
however, it also offers the possibility of concentrating water soluble
pesticides applied to the field.
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MEXICO
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Palo
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* County Maintained Pesticide Disposal Dump
Figure 1. 'mperia' Valley, California
8
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9
For the past two years, Imperial County has generated an annual
agricultural gross income of more than one-half billion dollars, ranking
it among the top five agricultural counties in the United States. As a
result of a twelve-month growing season, agricultural production is
extremely diverse. During any month of the year, all three phases of
agricultural development (planting, cultivation, and harvesting), as
well as cattle feeding operations, can be observed. Extensive use of
crop rotation is practiced so that over a two-year period most. cultivated
land will produce a series of three food and non-food products. As in
most highly developed agricultural areas (especially cotton-growing
areas), pesticide use is greatly relied upon to insure maximum production
from the land.
The majority of the landowners in Imperial Valley employ commercial
agricultural advisors. The advisor has the responsibility of identifying
insect populations, recommending when a pesticide application is required,
choosing the proper pesticide, and indicating the rate of application.
In some instances, the advisor performs these duties and charges the
grower for the service. It is then the responsibility of the landowner
to make arrangements for the purchase and application of the pesticide.
However, in other cases, the advisor performs his field evaluations free
of charge, with the agreement that all pesticides be purchased through
his distributing firm. In the latter case, the advisory firm may even
do a portion of the formulating. Under this program, the advisor makes
all necessary arrangements with the aerial applicator.
Certain aspects of aerial application in Imperial Valley differ
fro"! those observed at other areas of the country. A major portion of
the applications are made at night by aircraft equipped with high intensity
landing lights for illumination. There are two factors that make nighttime
applications desirable: 1) the adult moth of the pink bollworm (Pectinophora
gORsypiella [Saunders]), a principal pest organism of cotton, is nocturnal
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10
and therefore most susceptible to pesticide spray after dark, and
2) apiaries comprise a mil.lion dollar industry in the Valley and daytime
spraying while bees are foraging can be devastating to colonies.
Flight time is a critical factor, because of the large geographical
area encompassed by Imperial Valley and the intensity of aerial application.
To reduce flight time, few of the loading and mixing operations are
performed at a fixed staging area. Numerous small dirt landing strips
are located strategically throughout the valley in areas of the most
intensive spraying. These airstrips are maintained and used by a cooperative
effort of the applicator firms. No permanent facilities are provided at
the airstrip; mixing and loading operations are dependent upon the use
of mobile nurse rigs. . These are specially designed tank-trucks which
.rendezvous with the aircraft at a strip nearest the target field and are
capable of performing a complete mixing and loading operation. Dilution
water is carried aboard the truck and replenished, as required, from the
numerous irrigation canals in the area. .
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IV.
DESCRIPTION OF STUDY AREAS
Field "A" was a 5.5 ha (13.5 acres) rectangular field which was
planted in cotton. The field was surrounded by other cotton fields,
alfalfa, fallow ground, orchards, domestic dwellings, a livestock area,
and county roads [Fig. 2J. A'lateral canal borders the southern and
western portions of the field. A main collection drain runs south of
the field (but does not drain the target field) and empties into the
Alamo River to the west approximately 1.6 km (1 mi).
Twenty-four sampling stations were established in the study area.
One station (36) was located on the target field. Five stations (4, 6,
7,8,.32) were aquatic: two in the collection drain, one in the lateral
canal, and two in the Alamo River. The remaining eighteen sites were
located off the target field in areas likely to receive drift or where
excessive drift would be of concern, such as onto sensitive crops or
residences. The meteorological laboratory was located at station 45
[Fig. 2J.
Air samples were collected by various methods on and surrounding
the target field to determine drift characteristics [Table lJ. Soil,
water, vegetation, and sediment samples were taken at appropriate sites
for residue analysis. In-situ fish exposures were done in the lateral
canal, drainage ditch, and Alamo River and the fish tested for AChE
response.
Field "8" was 28.4 ha
cotton. It was surrounded
[Fig. 3J. A lateral canal
edge of the field.
(70 acres) in area and was also planted in
by cotton, alfalfa, county roads and residences
and small collection drain border the north
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12
COTTON
FALLOW
~
1
------------~------
@
COTTON
@
82
COTTON
:.,wDrain
Residence
45
LATERAL COLLECTION
11111"" ""',11"""'1,,,111,.
.',1 I
"
'ii0"1
41 ORC HA RD 40
;'I!I!III!IIIIJ!!IIIIIjz
SCALE: Icm=48 meters
LEGEND
ROAD
DRAIN
CANAL
III ,,,
----
ORCHARD
D
figure 2. Station locations Field "A"
Imperial Valley, California
August 1976
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14
POWER
FALLOW
~~~
ALFALFA
ALFALFA
FALLOW
COTTON
COTTON
RESIDENCE
SCALE: Icm = 48 meters
LEGEND
ROAD
-
:mz:zz:z:zz:z:
CANAL
DRAIN
----
ORCHARD
Iill!!!J
Figure 3. Station locations Field "8"
Imperial Valley I California
August 1976
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Tabl.e 1
SAMPLING STATIONS AND DEVICES
FIELD "A"
IMPERIAL VALLEY CALIFORNIA
August 1976
Station Number
Air Samplers
Greenburg-Smith High
Impinger Volume
Spray Droplet Card~*
Magnesium
Oxide Slide
Fish
Exposure
4
6
7
8
32
33
34
35
36
37
38
39
40
: 41
42
44
45
46
47
48
49
81
82
83
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
. X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
.X
X
X
X
X
X
X
X
A KI'omeaote, Themofax, Linagraph, MyZar
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15
Twenty-four sampling sites were selected on and surrounding the
field [Fig. 3]. Two stations were aquatic: one in the lateral canal
and one in the collection drain. Air and other environmental samples
were collected at pre-selected locations [Table 2]. Fish exposures were
done in the canal and drainage ditch. The meteorological laboratory was
located at station 88.
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16
Table 2
SAMPLING STATIONS AND DEVICES
FIELD "B,I
IMPERIAL VALLEY CALIFORNIA
August 1976 .
Air Samplers
Station Number. Greenburg-Smith High
Impinger Volume
Spray Droplet Cards*
Magnesium
Oxide Slide
Fish
Exposure
68 X
70 X
86 X X
87 X X
88 . X X
89 X X
90 X X X X
91 X X
92 X X
93 X X X X
94 X X
95 X X
96 X X X X
97 X X
98 X X
99 X X
100 X X
101 X X X X
102 X ..X "
103 X X
104 X X
105 X X 'X X
106 X X
108 X X
Rromeaote, Thermofa:r:, Linagraph, Mylar
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v.
DISCUSSION AND RESULTS
PRE-APPLICATION FIELD "A"
Prior to any pesticide application, it is the responsibility of the
agricultural advisor to identify insect populations, determine that pest
organisms are present in sufficient numbers to require treatment, and
recommend an appropriate pesticide and the application rate.
On August 24, adult moths of the pink bollworm began to appear in
pheromone (insect sexual attractant) traps in field "A" [Fig. 4]. The
advisor conducted a 20-minute evaluation using a sweep net and hand lens
[Fig. 5]. This investigation confirmed the presence of the adult moth
and egg masses clinging to the plant leaves. It also revealed the field
was infested with lygus (Lygus obLineatus [Say]). On the basis of this
evaluation, it was recommended that the field be treated with a mixture
of 1.23 pt/acre (1.44 liters/ha) of Azodrin 5 to control the adult moth
and lygus, and 0.615 pt/acre (0.72 liters/ha) Fundal 4*, an ovicidal
pesticide, to prevent maturation of existing egg masses. An application
rate of 5 gal/acre (46.8 liters/ha) was specified.
The advisor noted that the field had been irrigated recently and
postponed spraying for 24 hours. Application was to be made the night
of August 26. The infestation at that time was not severe enough that a
24-hour delay in treatment would endanger the crop. Prior to spraying,
the advisory firm notified the landowner of the intended application.
* Fundal :.!?) 4 - Reg. No. 2139-100AA-NOR-AM,}i: AgY'i. Products
-------
Figure 4.
pheremone trap.
Figure 5.
Evaluating insect infestation.
0:>
."-
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19
Precautionary requirements were detailed indicating a 36-hour re-
entry time~ no grazing or feeding of plant material to livestock~ and no
harvesting of the crop within 21 days of treatment. Later examination
of the pesticide labels and the Code of Federal Regulations showed the
recommendations were correct with the exception of the re-entry period.
The Code of Federal Regulations (Revised July l~ 1975) lists a re-entry
time for Azodrin of 48 hours~ not the 36-hour period recommended. It
was noted that recommended pesticide concentrations were less than the
maximum concentration permissible by the pesticide label. By using
lesser concentrations~ which experience had shown to be effective~ the
advisor demonstrated good judgment~ which was beneficial both economically
and environmentally.
The advisory firm is also a pesticide dealer and formulator; in
addition to supplying the required pesticides~ this firm made all further
arrangements with the aerial applicator. The application was made by
helicopter because this was an extremely small field~ and maneuverability
is very limited fora fixed-wing aircraft.
Since the advisory firm was also the pesticide dealer~ members of
the NEIC staff~ and an EPA Regional pesticide inspector conducted an on-site
evaluation of the storage facilities and handling procedures. Storage
facilities were found to be excellent [Fig. 6J. The building was modern,
clean and well ventilated. Pesticides were stored in an orderly fashion
and grouped by compound type and brand. Sufficient space was maintained
between each group of compounds to reduce the possibility of accidental
mixing or contamination. Adequate safety equipment~ such as protective
clothing and respirators, was present and appropriate precautionary
signs were posted in a clear and visible manner.
Installation of sampling devices to determine drift characteristics
began on August 25. Air samplers (Greenburg-Smith impingers and
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,
II:
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Figure 6.
Pesticide storage facility.
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,.~;..~~. t~'
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... ' - .II!!'
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21
high-volume samplers) were placed on the target field (station 36) and
along each side of the perimeter, 30 m (100 ft) from the field (stations
33, 37, 38, 39) [Fig. 7 and 8J. . Arrays of spray droplet cards (Kromecote,
Thermofax, Linagraph) mylar sheeting (drafting plastic), and magnesium-
oxide-coated glass slides were placed at 19 stations [Table lJ. Procedures
used to determine drift characteristics are described in further detail
in the Appendix. In-situ exposure of channel catfish was begun at
stations 4,6, 7,8 and 32.
Contact was made with the aerial applicator who indicated field IIAII
would be sprayed at approximately 2300 hours on August 26. However, by
2100 hours that evening a steady south-southeasterly wind gusting from
13 to 22 km/h (8 to 14 mph) had arisen and spraying operations were
postponed. The wind did not subside until approximately 0330 hours
August 27, at which time wind velocities of less than 6.4 km/h (4 mph)
were recorded.
At 0400 hours, the helicopter and nurse rig arrived at the corner
of a vacant field about 2 km north of field IIAII and the loading and
mixing operation began. An assortment of various pesticides for the
night spraying was stored in open compartments on the side of the truck.
The vehicle contained a large-capacity water reservoir and a separate
mixing tank. Only one member of the work crew was in the immediate
vicinity of the truck when mixing operations commenced. This worker was
observed wearing the necessary safety equipment required for a mixing
operation: long-sleeved coveralls of tightly woven fabric, a large
rubberized apron. heavy rubber gloves, boots, hat, protective eye
goggles and a canister-type respirator. The worker first read a copy of
the advisor's recommendations specifying the pesticides to be applied
and the application rate. Containers of Azodrin 5 and Fundal 4 were
removed from the truck and placed on the ground near the mixing hopper.
The containers were intact and appeared to be free from pesticide
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\&
~A-
.-
Figure 7.
High-Volume Air Sampler with lid
raised showing fiberglass filter.
~-
Figure 8.
Greenburg-Smith air sampler with
upper cover assembly removed to
expose impinger train.
22
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23
residue. The EPA inspectors confirmed these were the same compounds as
listed on the recommendation and withdrew samples for later analysis.
The mixing tank was of steel construction with a large hinged access
door on the left side. Mixing was accomplished by a series of paddle-
type rotary agitators. Approximately one-third the volume of water to
be used was first introduced into the mixing hopper. Then 2 gal (7.6
liters) Azodrin 5,1 gal (3.8 liters) Fundal 4, and 1 gal (3.8 liters)
nutrient buffer were added. After the pesticide addition, EPA personnel
added a tracer dye material (Rhodamine WT) to achieve a final dye
concentration of 1,000 ~g/l. Empty pesticide containers were rinsed and
the wash water added to the mix tank. Next, the hopper door was closed
and agitation begun while the volume of the mixture was increased to 65
gal (246 liters). After complete mixing of the material had occurred,
the EPA inspector withdrew a sample from the mixing tank for pesticide
.analysis. The pesticide mixture was then pumped through a heavy-gauge,
flexible hose into the aircraft hopper.
A tight seal was maintained between the hose coupling and the
aircraft throughout the loading operation and no visible leakage occurred.
The pump loading system was a type which, at "the completion of loading,
sucks any remaining material in the delivery hose back into the mixing
tank. When the hose was disconnected from the aircraft, no residual
pesticide mixture was seen to flow onto the ground. A second sample of
spray mixture was collected directly from the aircraft hopper after
loading was complete.
Empty, rinsed containers and refuse (paper cartons, wrappers, etc.)
were placed aboard a separate truck and returned to the applicator's
main property for proper disposal. Disposal of used pesticide containers
does not pose the problem to applicators in Imperial Valley as has been
seen to occur in other areas of the country. Four fenced, posted, and
secured dumps [Figs. 1, 9, 10] are maintained by the County for the specific
-------
110,.
. ~
"'
,.,
--
Figure 9.
Pesticide container disposal
site.
Figure 10.
Fenced disposal site with
perforated containers awaiting
burial.
24
-------
25
purpose of pesticide container disposal.
for proper burial of the containers.
The County assumes responsibility
The procedures followed by the applicator for mixing and loading
were good. The worker involved in mixing and loading appeared conscientious.
familiar with his job. and conducted the operation in a neat and orderly
manner. All proper safety precautions were taken and adequate protective
equipment was used in pesticide handling and mixing.
The applicator's temporary storage facility for used pesticide
containers was good. Rinsed and perforated containers were stored in a
slat-sided. open-topped trailer. A unique feature of this trailer was a
trapdoor arrangement that allowed unloading of the containers at the
dump site without being handled by the worker [Fig. 11]. The location
of the trailer was poor, being in close proximity to livestock pens and
an unprotected haystack. Various unperforated containers littered the
ground near the trailer.
There was no evidence in the area of an adequate facility for
cleaning and rinsing of applicating equipment.
Later analyses of the diluted samples taken from the mixing and
spray tanks confirmed the presence of Azodrin and Fundal. However, a
discrepancy was noted between the concentrations of pesticide in the mix
tank and the spray tank. The total concentration of pesticides was 25%
lower in the spray tank than in the mix tank [Table 3J. Several ex-
planations are possible. but none is conclusive.
1.
It is possible the sample was taken from the tank before total
mixing of the material had occurred. This seems unlikely
because the agitating system in the mix tank seemed efficient.
-------
~
o
Fi gure 11.
Temporary storage and transport
vehicle designed to automatically
unload empty chemical containers.
~. ,.-----
Figure 12.
Hiller helicopter equipped with
spray boom.
26
-------
Table 3
PESTICIDE CONCENTRATIONS APPLIED
IMPERIAL VALLEY, CALIFORNIA
August 1976
Fie ld "A"
Compound Mixing Tank Spray Tank
Azodrin 1. 21 % 0.86%
Fundal 0.24% 0.20%
Methyl Parathion 0.02% O. 02 %
(Contaminant)
Ethyl Para thi on 0.02% 0.02%
(Contaminant)
% Loss
29%
17%
o
o
Weighted average loss of active ingredients - 25%
Field liB II
Lanate (Nudrin) 0.53% 0.45% 15%
Azodrin 0.94% 0'.82% 13%
Methyl Parathion 0.56% 0.48% 14%
Ethyl Parathion 1 . 17% 1 . 02 % 13%
Weighted average loss of active ingredients - 14%
27
-------
~8
2.
Additional dilution water could have been pumped into the mix
tank after the laboratory sample was taken. This was not
observed to have occurred.
3.
Material from an earlier application may have remained in the
spray tank of the aircraft and diluted the new mixture.
However, to cause a 25% dilution this would have required
approximately 75 liters (20 gal) of residual material, which
is unlikely.
A 25% loss of active ingredient is significant because it could
result in reduced efficiency of the pesticide. It would be advisable to
sample additional mixing and spraying tanks to determine whether the
loss of active ingredient is real or artificially induced by sampling
technique.
Analysis of the mix and spray tank material showed the presence of
both ethyl and methyl parathion at concentrations of 0.02% each (200
mg/l each). The appl icator had acknowl edged havi ng sprayed Lana te (B) *,
phosphamidon, and diazinon that evening prior to the application on
field "A". This indicates the residual parathion was persistent in the
mixing tank for a minimum of 24 hours. The contamination of the spray
mixture, in this case, does not constitute an inconsistency with Federal,
Regulations since both contaminants are registered for application on
cotton. However, it does emphasize the need for thorough rinsing of
mixing and spraying. equipment because a violation could have occurred
had the application been on a crop other than cotton. In addition, it
is known that the combination of some pesticides may give rise to poten-
tiation -- an increase in toxicity beyond that expected from a mere
summation of the constituents.4 This could be of obvious benefit to the
* Lanate is a Registered trademark~ DuPont
-------
29
landowner in reducing insect pest populations; however, it could also
produce environmental damage by affecting beneficial organisms known to
be resistant to the intended pesticide application. It should not be
overlooked that this was not the first application made with this
equipment on that evening.. If the contamination was, as it appears, in
the mixing tank, earlier applications may have contained substantially
larger concentrations of ethyl and methyl parathion. Analyses of the
undiluted pesticides used for this application showed all materials to
be formulated properly.
APPLICATION FIELD "A"
The aircraft used for this application was a Hiller helicopter
[Fi g. 12J. The spray boom was equi pped with 46 Tee Jet@ * spray
nozzles, #45 whirl plates and operated at 2/kg/cm2 (30 lb/in2) pressure.
The spray nozzles were not symmetrically arranged on the boom but were
placed at varying angles from each other. This arrangement was intended
to compensate for the vortices produced by the helicopter downdraft, and
I
to insure uniform coverage. The aircraft"sprayed a 12 m (40 ft) swath
at approximately 65 km/h (40 mph).
The EPA observers were stationed 30 m (100 ft) from the field on
each side of the perimeter. All personnel wore protective clothing
consisting of long-sleeved waterproof coveralls, head and foot covering,
gloves, a canister-type respirator, and protective eye goggles [Figs. 13,
14J. High-volume air samplers and the second impingers of the Greenburg-
Smith units were turned on 45 minutes before spraying.
* Tee Jet is a Registered trademark, Spraying Systems Co.
-------
I.
I
k'\"
I ~-
t
i
"
1i!!!I.,... '
-
I
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I
Till'
, .".
~
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7.
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A
Figure 13.
'.
'-
Protected worker examining spray
droplet cards.
Figure 14.
Removing equipment from a recently
sprayed cotton field.
w
(:)
-------
31
Two workers who served as flaggers arrived ten minutes before the
application and stationed themselves at the north and south ends of the
field. These workers were dressed in closely woven fabric long-sleeved
coveralls and baseball-type caps~ Respirators were not worn. Each
person carried a luminous baton to increase their visibility to the
pilot.
The initial pass by the helicopter was made at 0505 and the entire
spraying operation was completed by 0516. The main application was made
along the north-south axis of the field parallel to the cotton rows and
required fifteen passes by the aircraft. Four additional passes were
made along the east-west axis to trim the north and south edges of the
field. Altitude of the aircraft appeared to be 3 to 4 m above the
cotton. Flaggers remained stationary with their batons held aloft as
the aircraft made its descent onto the field. As the helicopter approached,
the flagger began walking to the next reference point so that the aircraft
never passed directly overhead.
The physical characteristics of the spray droplets and local meteoro-
logical conditions determine the rate of transport of airborne spray
particles from any target area. The larger the spray droplet, the less
potential it has to drift from the area of intended application.5
Meteorological conditions affecting drift are: wind direction and
velocity, turbulence, relative humidity and air temperature and atmospheric
stability. Wind direction and velocity are primarily responsible for
lateral transport of particles, whereas turbulence induces vertical
movements. Relative humidity and air temperature determine the rate of
evaporation and thus influence the size of liquid droplets. Atmospheric
stability characterizes the degree of turbulence associated with certain
meteorological conditions. The most stable atmospheric condition is
known as an inversion, which occurs when the overhead layer of air is
-------
32
warmer than air at ground level. This condition usually occurs between
early evening and early morning and is characterized by low wind velocity
and little vertical turbu1ence.5
During the application an inversion existed and atmospheric conditions
were very stable. Air temperatures at the 2-m height ranged from 24.9
to 25.1°C (76.8 to 77.2°F) while the 10-m readings ranged from 26.4 to
26.8°C (79.6 to 80.2°F) [Figs. 15, 16]. As would be expected under in-
version conditions, no lateral air movement was recorded. Relative
humidity was 47%. In general, atmospheric conditions were adequate for
aerial application with acceptable drift potential.
POST APPLICATION FIELD IIAII
Four hours after the application, all sampling devices with the
exception of the fish exposure cages were removed from the field and
surrounding areas. Samples of soil, water, vegetation and sediment were
taken at this time for pesticide residue analysis.
~\
Air samples from the Greenburg-Smith impingers and high-volume
samplers, as well as residue droplets on the mylar sheets, were analyzed
at the field laboratory for fluorescent dye. None of the air sampling
devices produced consistent results.
Analyses of the spray droplet cards indicated Kromecote was in-
effective for an Azodrin-Fundal spray mixture; however, both Thermofax
and Linagraph cards produced positive droplet impressions. The mag-
nesium-oxide-coating on glass slides was totally destroyed by windborne
dust particle abrasion that occurred prior to the application. This
precluded any estimation of droplet size by the Volume Median Diameter
(VMD) method.
-------
~
~-~-: ".~-
r---
I ~,..
~
I
II
~
r~,,~
r""' ..
. ..~
.' ''4,' JI ~
Figure 15.
-
. .
. .
. -
..L
Meteorological Laboratory with
10-meter temperature probe.
Figure 16.
I
~
,
,
,
~-~--*~~
't\ -t--~
~ . <'~ .-r; - ;t
. '.; ~~ ".-~/. i'J
,," ~"'!
,::, . . .,
'-, J
Meteorological unit with 2-meter
temperature probe, anemometer
and wind directional vane.
w
w
-------
34
Examination of the Thermofax and Linagraph spray droplet cards
indicates the app1icating equipment produced an extremely coarse spray.
Spray cards exposed on the cotton field were badly blurred from the"
excessive moisture of the large droplets but showed good spray coverage.
Droplet counts of the spray cards revealed the applicator had done a
commendable job of confining the spray material to the target field
[Table 4J. Although spray drift was detected at all sampling stations,
the majority of the off-field spray cards contained less than 0.2 drop-
1ets/cm2 and a maximum count of 0.4 drop1ets/cm2. Spray cards on the
target field produced droplet counts in excess of 28 drop1ets/cm2.*
Chemical analyses of the Greenburg-Smith impingers failed to detect
the presence of Azodrin. This probably resulted from the propensity of
Azodrin to hydrolyze. However, ethyl and/or methyl parathion were
captured in all of the impinger units in concentrations ranging from
0.17 to 0.42 ~g [Table 5J.
The high-volume air samplers proved more efficient than the impingers
in capturing pesticide drift, in general, "and Azodrin, in particular.
Ethyl parathion concentrations in the samples ranged from 0.99 to 3.2 ~g,
methyl parathion 0.16 to 0.42 ~g and Azodrin 0.55 to 30 ~g [Table 5J.
The presence of Azodrin in the samples confirmed that the spray drift on
the droplet cards resulted from the observed application.
Residue analyses of soil from the target field showed no trace of
pesticides, indicating the spray was well confined to the foliage.
Residues of methyl parathion and Azodrin (0.002 and 0.20 ~g/g, respectively)
were detected on leaf material of a commercial peach and apricot orchard
about 180 m (600 ft) south of the target field (station 41). At the
time of application, the orchard had already been harvested.-
* Because of extreme running and blurring of this card~ 28 droplets/cm2
is a lo~ count. The actual number of droplets is undoubtedly higher
due to smaller droplet impressions being masked by excessive moisture.
-------
Table 4
SPRAY DROPLET COUNTS*
FIELD "A"
IMPERIAL, VALLEY, CALIFORNIA
August 1976
Station Number
Card Type
Linagraph Thermofax
33 0.01 0
34 0.26 0.02
35 0.13 0.12
36 ** 28.1
37 0.13 0.12
38 0.25 0.12
39 0.09 0.06
40 0.20 0.12
41 0.25 0.13
42 0.23 0.06
44 0.15 0.09
45 0.21 0.14
46 0.05 0.11
47 0.12 0.12
48 0.40 0.05
49 0.40 0.38
81 0.01 0
82 0.01 0
83 0.02 0.02
* Values expressed ers droplet., impressions' per em2.
** Droplet card excessively blurred, precluding a count.
35
-------
Ethyl Parathion Methyl Parathion Azodrin
0.42 0.30 ND*
NO 0.18 NO
0.37 0.25 NO
0.25 0.17 NO
Q.99 0.16 0.55
3.20 0.42 30.0
0.40 0.28 ~B
NO 0.0 5
ND NO NO
NO NO NO
NO 0:002 0.20
Methyl Parathion Azodrin
. O.Ol~g O. hg
O.Olllg O. l11g
0.00211g/g 0.0211g/g
O.l~g/l 50 ~g/l
Table 5
PESTICIDE RESIDUE ANALYSES
Field "A"
IMPERIAL VALLEY~ CALIFORNIA
August 1976
Station No.
Sample type
Greenburg-Smith Impinger (llg)
36
37
38
39
37
39
High Volume Filters (llg)
04
32
36
41
Environmental Samples
Water (llg/l)
Sediment (~9/9)
Water (~g/l)
Soil (\1g/g)
Vegetation (~g/g)
Detection Limits
Greenburg-Smith Impinger
High Volume Filters
Soil & Vegetation
Water .
Ethyl Parathion
O.Olllg
O.Olllg
0.002~g/g
O.l11g/l
* Not Detectable
w
m
-------
37
In-situ fish exposures were terminated on August 30 and the channel
catfish were analyzed at the field laboratory for acetylcholinesterase
activity. The mean AChE activity for the reference group of fish
(station 32) was 1.34 micromo1es ACh (acetylcholine) hydrolyzed per
milligram of brain per hour. An AChE activity 20% less than the reference
group mean activity is considered abnormally low and indicative of the
presence of a cholinesterase-inhibiting compound (organophosphate and
carbamate pesticides). Laboratory tests have shown that some test fish
can survive up to 80% AChE inhibition for short periods of time.
However, even a mild decrease in AChE activity results in a decrease in
the overall endurance of the fish. In a natural environment, this
condition makes fish more susceptible to natural predation. AChE inhibition
occurred at stations 4 and 7, both located in the lateral drainage ditch
[Fig. 2]. AChE activity for fish exposed at these sites averaged 0.88
. .at station 4, and 0.79 at station 7, representing acetylcholinesterase
inhibition of 34 and 41%, respectively. Fish exposed in the Alamo River
upstream and downstream from the mouth of the drainage ditch had AChE
activities averaging 1.26 and 1.17, respectively. These actiVities were
not pathologically lower than the activities of the reference fish.
However, the downstream fish with AChE activities of only 1.'17 were in
I
the low-normal range (an activity of 1.07 would constitute inhibition).
It is likely that an extended exposure at this Alamo River site would
have resulted in AChE inhibition in these test fish.
There is no indication that the AChE inhibition resulted directly
from the pesticide application of field IIAII since the reference group of
fish at station 32 was equally exposed to potential spray drift. It is
also unlikely that drift from other applications in the area was responsible
for the pesticide contamination as the drain and canal flow parallel for
several kilometers. Chemical analyses of the waters in the lateral
canal and drain showed the canal (station 32) to be free of pesticide
residue while the drain (station 4) contained measurable concentrations
-------
'38
of ethyl parathion (0.4 ~g/l)'and methyl parathion (0.2 ~g/l). Only a
trace of methyl parathion (0.005 ~g/g) was found in the sediment of the
drain at station 4, indicating the pesticide residue in the water was
not leaching directly from the sediment bed. This implies that the
pesticide contamination of the water resulted from runoff of surface
water or through the tile drainage system.
The fate of all drainage waters in Imperial Valley is the Salton
Sea by way of the Alamo and New Rivers. If pesticide contamination of
drainage water occurs commonly, the possibility exists that accumulation
of pesticides is occurring in the waters and sediments of the Salton
Sea. Even though most organophosphate pesticides are readily hydrolyzed
some have been shown to be very persistent; for example, methyl parathion,
one of the contaminants identified in the drainage water, can remain
active in water for nearly two years.6 It should be further recognized
that water samples were analyzed only for three organophosphate compounds:
methyl and ethyl parathion, and Azodrin. A multitude of other pesticides
are used commonly in Imperial Valley and could have been present in
measurable quantities. Additional sampling should be done to identify
the full impact of drainage water contamination in this area.
PRE-APPLICATION FIELD "S"
The advisory firm that controlled pesticide application on field
"S" was the same firm as was employed for field "A". The use of pheromone
traps and net sweeping for identification of insect pests was identical
to the procedures observed during the investigation of field "A". On
August 26, it was determined that an infestation of bollworm (EeZiothis sp.)
and pink bollworm on field "S" was sufficiently severe to justify
chemical control. It was also noted that numerous salt marsh caterpillars
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39
(Estigmene acraea [Drury]) were present in the field; however, if
bollworm. and pink bollworm had been absent the caterpi llar infestation
by itself would not have posed a threat to the cotton crop serious
enough to justify pesticide application. A recommendation was made that
the field be sprayed with a mixture of 1.02 pt/acre (1.20 liters/ha)
Azodrin 5,0.80 pt/acre (0.941iters/ha) Parathion 6-3E* and 1.94 pt/acre
(2.27 1iters/ha) Nudrin 1.8 at an application rate of 5 gal/acre
(46.8 1iters/ha). Application was to be made the night of August 28.
Precautionary advice on the recommendation indicated the re-entry time
to be 48 hours, a lapse period of 30 days until harvest and that the
foliage was not to be used as animal feed at any future time. Later
examination of the pesticide labels indicated the recommended pesticides
were registered for use on cotton and the application rates were correct
for the target insect pests. The re-entry time of 48 hours for this
, .app1ication is in compliance with the Code of Federal Regulations.
However, the drum label for Ethyl-Methyl Parathion 6-3E (State Reg.
No. 08434-5D043-AA) recommended a re-entry time of 24 hours.
This label should be updated to comply with the Code of Federal Regulations.
The recommendation for a 3D-day delay before harvest is incorrect. The
30-day period recommended is satisfactory for the Azodrin and parathion
components; however, the drum label for Nudrin stipulated application
should not be made within 40 days of harvest.
As in the previous application, arrangements were made with the
aerial applicator by the advisory firm; spraying would be done by a
fixed-wing aircraft.
Sampl ing devices were installed on field 11611 on August 28.
Ai.r
* Parathion 6-JE is a formulation prepared by the advisory firm and
consists of a mixture containing 6 lb ethyl parathion and J lb
me thy l parathion/ ga l. .
-------
40
samplers (Greenburg-Smith impingers, and high-volume air samplers) were
placed on the target field (station 93) and on each side of the perimeter,
30 m (100 ft) from the edge of the field (stations 90, 96, 101, 105).
Three types of spray cards (Kromecote, Thermofax and Linagraph), mylar
sheeting, and magnesium-oxide.:.coated glass slides were placed at 22
stations [Table 2]. Channel catfish were exposed in cages at station 68
and 70.
The mixing and loading operation began at approximately 01 00 August
29 at an air strip 8 km (5 mi) from field "6". Only the pilot, a
worker who mixed the pesticides, and EPA inspectors were present for
this operation. However, the pilot took no active part in the mixing
operation; he remained a safe distance away from the mixing area. The
worker was properly attired in long-sleeved coveralls, a heavy rubber
apron, foot coverings, heavy rubber gloves, hat, eye protectors and a
canister-type respirator. After consulting the advisor's recommendation,
the mixer removed the containers of Azodrin 5, Parathion 6-3E, and
Nudrin 1.8 from a side compartment on the truck and placed them on the
ground beside the mixing hopper. The containers were intact and free
from visible pesticide residue. The EPA inspector confirmed these were
the proper registered pesticides that appeared on the recommendation and
a representative sample was collected of each compound for analyses.
The nurse rig used for this operation was more sophisticated than that
observed on the previous application in that it had the potential for a
nearly completely closed mixing and loading operation [Fig. 17J. There
were two methods by which pesticides could be introduced into the mixing
, ' '
tank. Small containers (1 to 5 gal) could be manually poured into an
open hopper and pumped into the mix tank. For large bulk containers
(30- to 50-gal drums) the truck was equipped with a specially designed
hose and dipstick apparatus. This system could be inserted into the top
bung hole'of the container and meter pumped into the mix tank without
exposing the pesticide to the air. There was no evidence of a rinsing
-------
"',
Figure 17.
"Nurse Rig" with open hopper
(arrow) and mixing tank.
--<
't'
I
..
~. . - .,
Figure 18.
Close-up view of the open hopper
showing "Jet-Rinse" apparatus
(arrow).
41
-------
42
apparatus for the dipstick, hose assembly or bulk container, thus pre-
venting this system from being co~pletelyclosed. Agitation within the
mix tank was accomplished by a high-volume recirculating pump.
The mixing operation began by first pumping approximately 100 gal
(378 liters) of dilution water into the mixing vat. The addition of 9
gal (34 liters) Azodrin 5, 17 gal (64 liters) Nudrin 1.8, and 1 gal (3.8
liters) nutrient buffer was made through the open hopper. A jet spray
rinsing device was incorporated into the hopper. This consisted of a
1.27 cm (1/2 in) metal pipe about 30 cm (12 in) long, over which the
empty container could be placed [Fig. 18]. A high-pressure stre~m of
water was pumped into the empty container, flowed back into the hopper
and was pumped into the mix tank. The rinsed containers were placed in
a separate area on the truck along with miscellaneous paper cartons and
refuse to be returned to the main staging area for later disposal at a
County-maintained dump. The Parathion 6-3E was in a 30 gal plastic bulk
container. The dipstick system was used to add 7 gal (26.5 liters) of
the pesticide to the mixing tank. After all the pesticides had been
added, EPA personnel introduced a fluorescent tracer dye (Rhodamine WI)
into the mixture to achieve a final concentration of 2,000 ~g/l. The
volume of the mixture was then increased to 350 gal (1,325 liters), the
correct volume for an application of field "8" at the rate of 5 gal/acre
(46.8 liters/ha). After the mixture had been agitated for 15 minutes,
EPA inspectors collected a sample for pesticide analysis.
During the fi.nal stage of the mixing operation, a gusting 16 km/h
(10 mph) southeasterly wind arose. The pilot made radio contact with
the flaggers, who had already arrived at the target field, and confirmed
that the same windy conditions existed at the spray site. The worker at
the mixing site was then instructed to hold the pesticide mixture on the
tank truck, under agitation, until atmospheric conditions improved. The
wind continued until about 0245, at which time the pilot.determined
-------
43
conditions had stabilized sufficiently to permit aerial spraying.
Before the loading operation was begun, the pilot again contacted the
field site and learned that stable conditions existed there, also.
Then, 175 gal (662 liters) of pesticide mixture was pumped aboard the
aircraft through a heavy flexible hose. This loading system was a type
similar to the one previously discussed and no pesticide was observed
leaking onto the ground during the loading or uncoupling operation.
After the aircraft was fully loaded, a second mixture sample was collected
by the EPA inspector directly from the aircraft spray hopper.
The entire mixing and loading operation was performed in an ex-
emplary fashion. The worker involved in mixing performed his tasks in a
neat and orderly manner while observing all necessary safety precautions.
The pilot exercised good judgment by postponing the scheduled application
when weather conditions deteriorated, and also by maintaining radio
contact with the field site.
The jet spray rinsing system is an excellent feature which should
be used on other mixing systems whenever possible. The jet spray system
eliminated the problem associated with rinse water disposal and reduced
the hazard of handling and transporting empty containers, particularly
glass. It is apparent that there is a need for more bulk packaging of
pesticide material. Only one of the three pesticides used in this
mixture was provided in a bulk container suitable for full utilization
of the semi-closed mixing operation the nurse rig was capable of performing.
It was also noted that the plastic bulk container was recyclable; the
pesticide industry should be encouraged to use more recyclable containers
to alleviate disposal problems.
An inspection by EPA showed that this applicator managed his premises
in a commendable manner. All spraying equipment was neatly stored,
segregated by specific type, and appeared clean and well maintained.
The washing facility for spray equipment consisted of a large, sloping
-------
44
concrete apron. All contaminated water associated with washing and
rinsing activities was collected from the apron, piped underground, and
emptied into a leach field approximately 90 m (100 yd) away [Fig. 19J.
A facility for temporary storage of rinsed and perforated pesticide
containers was maintained about 90 m (100 yd) from the work area. The
storage area was situated at the lowest section of the property to
prevent contamination of other areas and was secured by a 2-m (6-ft)
chain-link fence and conspicuously posted with appropriate warning signs.
[Fig. 20J.
Chemical analysis of the mix and spray tank samples confirmed the
presence of Azodrin, methyl and ethyl parathion, and Nudrin. However,
pesticide concentrations averaged 14% higher in the mix tank than in the
spray tank [Table 3]. The explanations for this are the same as those
proposed in the pre-appl ication' discussion of"field "A". Analyses of
the undiluted pesticide used for this application showed all materials
to be formulated properly.
APPLICATION. FIELD "B"
The aircraft used for thi s appl ication was a fixed-wing Snow Air
Tractor. The spray boom was equipped with 36 Tee-Jet nozzles and #45
whirl plates arranged at equal intervals along its length. Spraying was
done at an air speed of approximately 160 km/h (100 mph) at a boom,
pressure of 2.8 kg/cm2 (40 psi) which produced a swath width of 18 m (60 '
ft) .
The EPA observers were stationed 30 m (100 ft) from the field on
each side of the perimeter. Protective clothing worn was the same as
during the application on field "A".
-------
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Figure 19.
I!!I!
,""
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.~
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- -, ~ "
, / ---~ "- --....:....
. ~ ~
... -, . "'..
. - ~~ -,-
Leach field for contaminated
wash water.
... -..... '';~", ,,'~. .
I' . 11II!iD.:-~"I"'I~,""~"""-'~ ." ~, "
".., ~,,;f~- ~ ;..! (.' ..f"'''''' ,
.-", "'. '"'' r_Q,.~:\(4!. ~ ~.~ ,-. ";~,,..,(~- _.>
~~~~ ._~ ;.' I~~' ~ ~,'rv'~~. ~ ,..f ~'~J~,~"-"" .~\~
.,' rr'r:.:...rl' ~...::£ ,'(I..:.. . r " - :;.!'. . ,a
..' """t',' '.',,' . "}~~, . ",' " . .'" ' ....,
' l, ;'- ..., '.. ..J.'..
. . .- - r' . "...
._~--- -~ ...-cll- .!..' I.. . .J,--IJ 1
~~~~~~'~, ~~ ~... -~~~ "~-~..~-'.:' ...:..~
~. ~,..;.' ~, '-, ------ " ~,,'-...--""':" _A.-_-, i
- ---.~ ..s.....-~ - - .....~
Figure 20.
Temporary storage facility for
used pesticide containers.
45
-------
46
Two workers assigned as flaggers arrived at the field site approxi-
mately two hours before the application. These workers were in radio
contact with the pilot, keeping him updated on changing wind conditions.
Protective clothing worn by t~e flaggers consisted of tightly woven
fabric long-sleeved coveralls~ baseball~type caps and each had a canister-
type respirator. No gloves, eye protection or special footwear were
observed. Each worker carried a lighted baton.
Two 175 gal (662 liter) applications were required to spray the
field. The first application began August 29 at 0317 and ended at 0342
and the second began at 0355 and was terminated at 0425. The application
pattern consisted of first spraying the middle of the field along the
east-west axis parallel to the cotton rows. The flaggers initially were
stationed at the northwest and southeast corners of the field and worked
towards each other as the pilot alternated passes from the north and
south edges of the field inward. The ends of the field were sprayed
along the north-south axis with a similar alternating pattern. It was
noted the flagger at the western edge of the field wore a respirator
during the application. The other worker on the eastern border of the
field, being upwind, did not wear a respirator. Analysis of spray drift
patterns will show that simply being upwind of the target field is no
guarantee of escaping spray drift. During this particular application,
the upwind (eastern) border of the field received substantially more
drift than did the western edges.
,Local atmospheric conditions during the application were stable
with wind velocity less than 1.6 km/h (1 mph). Temperature measurements
at the 2-m level ranged from 28.0 to 28.7°C (82.4 to 83.7°F) and from
29.1 to 29.9°C ~4.4 to 85.0°F) at the 10-m height, with an average
temperature differential of 1.3°C (2.4°F). This constituted an inversion
condition. Relative humidity was measured at 61%. Visibility at ground
level was good; however, it was poor in the warmer overlying air mass
-------
47
approximately 30 m above the ground. .This condition made
difficult. Often the pilot's visibility of the field and
obstructed and many approaches were aborted.
the application
flaggers was
During the interview with EPA inspectors earlier in the evening,
the pilot indicated an awareness of the close proximity of the alfalfa
field bordering the southern edge of field "8". It was noted that
during the application the pilot exercised extreme caution when trimming
this section of the field. No mention was made of the somewhat more
distant alfalfa field bordering half of field "8" to the north. Later
analyses of spray cards showed the southern alfalfa field received
minimal spray drift while the field to the north received substantial
dri ft.
Approximately one hour after the observed application, a pesticide
application was made on the cotton field bordering the western perimeter
of field "8". Neither EPA personnel or the landowner, who'se residence
is at station 87, were aware that this application was scheduled. The
advisory firm responsible for this cotton. field was not the same firm as
was contracted to maintain field "8". Contact was made the following
day with the second advisory firm and it was learned the application had
consisted of 1.053 pt/acre (1.23 1iters/ha) Azodrin and 1.053 pt/acre
(1.23 1iters/ha) Fundal. The advisor informed EPA inspectors that, on
the day prior to the application, he had attempted several times but had
been unable to contact the landowner by telephone to inform him of the
intended. application. The landowner confirmed that he had been absent
from his residence the previous day and had not returned until late
evening on the night of the application. Had the residence not been
close enough to the field for the noise of the spray plane to awaken
him, the landowner would have been totally unaware that his field had
been recently sprayed with pesticide. Conceivab1y~ the landowner or
laborers could have entered the field unprotect~d a few hours after
the pesticide application. The lack of notification to the grower is
.'
(~ .
-------
48
not inconsistent with State pesticide regulations, which only require
that a written notification be mailed prior to the application. However,
it is doubtful that many landowners ever receive this notification prior
to the application because spraying must often be done soon after an
infestation is detected to minimize crop damage. On their own initiative,
advisory firms attempt to inform landowners orally of intended applications.
It would be desirable to enact regulations to make verbal contact
with the landowner or his responsible representative mandatory; in cases
where this is impossible, the target field should be conspicuously
posted and d~ted, specifying a safe re-entry time.
POST APPLICATION FIELD "B"
All sampling devices, except fish exposure cages, were removed from
the target field and surrounding area five hours after the application.
At this time, samples of soil, water and vegetation were taken for
pesticide residue analysis.
Tracer dye (Rhodamine WT) was detected at inconsistent low levels
in samples collected by the Greenburg-Smith impingers, high-volume
filters, and in droplets deposited on mylar sheets. All three types of
spray droplet cards (Kromecote, Linagraph and Thermofax) produced positive
droplet images. Magnesium oxide coatings on glass slides were again
destroyed by wind and dust particle abrasion.
Examination of the spray droplets showed a close correlation of
droplet counts between Thermofax and Linagraph cards. Droplet counts
for Kromecote cards, however, were consistently lower [Table 6]. Laboratory
investigations conducted by NEIC and data obtained from previous studies
indicate Kromecote is only sensitive to the parathion fraction of the
spray mixture used. Except for the directional component, drift
-------
49
Table 6
SPRAY DROPLET COUNTS *
Fie Ui "B"
IMPERIAL VALLEY~ CALIFORNIA
August 1976
Station No. Kromecote Linagraph Thermofax Vertical Kromecote*
86 3.1 17.1 18.8 S-SW
87 12.0 31.0 36.3 . S-SE
88 9.6 30.0 28.4 S-SW
89 45.5 69.4 71.4 S-SW
90 11.2 38.7 38.2 S-SW
91 11.4 31.6 32.6
92 10.3 20.4 20.2
93 64.7 77.8 84.1 S-SE
94 28.6 34.0 39.1
95 19.2 26.4 28.7
96 24.7 38.8 38.5 S-SE
97 0.01 1.0 0.8
98 37.8 68.1 70.0
99 0.02 1.3 . 1.2
100 0 0.08 0.09
101 0.05 0.09 0.02
102 0.02 0.04 .0.03
103 0 0.01 0.02
104 0.01 0.01 0.02
105 5.7 44.3 45.8 S-SE
106 11.4 32.3 33.3
108 22.7 44.8 50.1
* Values expressed as droplet impressions per cm2.
** Indicates approximate wind direction.
-------
50
characterizations discussed elsewhere in this report are based on
Linagraph and Thermofax droplet cards.
The spray droplets resulting from this application were considerably
less coarse than those observed at field "A"; consequently, drift was
more extensive [Fig. 21]. It is emphasized that droplet counts are not
quantitative values and do not represent the actual amount of pesticide
that contacted the droplet card. Spray cards from off the target field
had numerical counts nearly as high as a card from on the field; however,
they were composed of smaller droplet impressions, thus representing
lower pesticide concentrations.
The vertically placed Kromecote cards showed the direction of drift
to be basically to the north, occasionally changing to northeast and
northwest. This correlated well with meteorological data which showed a
prevailing south wind with minor variations from southeast and southwest.
Spray drift occurred in all directions for a distance of at least 30 m
from the target field and was detectable for a distance of 300 m (1,000
ft) to the northwest (station 86).
Drift to the south, over the alfalfa field, was less than in any
other area. This resulted from a combination of pilot awareness of the
alfalfa field and the prevailing southerly winds. Areas that received
substantial spray drift included two domestic dwellings (stations 87 and
108), a private orchard and livestock enclosure (station 94) and a
second alfalfa field directly north of the target field (stations 90,
91, 92).
Spray drift in the northwest section resulted from a combination of
the observed application and the spraying that occurred an hour later on
the cotton field to the west.
-------
Field "A"
~. \.~;~~~r:... ): ~ ~
-.....' . to . ~I
!~. '~,,' .:' ...,; ~,::.
'. - '.. ,-.' ,~ - ~
~'~.. . ~.' ";:'.'. ' '
40" """'1'\ ~ .. ..
'"
.
f1
'"
.
.
.
.
.
. .
.
.
.
-0
. .
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-------
52
Chemical analysis of the Greenburg-Smith impinger samples was
positive for methyl and ethyl parathion at all stations (90, 93, 96,
101, 105)[Tab1e 7J. As previously noted, this sampling method was
ineffective for the detection of Azodrin. At present, there is no
adequate method of analysis for low concentrations of Nudrin.
Total concentration of pesticides (ethyl and methyl parathion) from
the impinger units ranged from 2.4 to 16.9 ~g [Table 7J. The impinger
unit at station 90, north of the target field, entrapped 16.9 ~g total
pesticide compared to 14.1 ~g at station 93, on the target field. There
are two probable explanations for the target field sample being lower in
pesticide concentration: the cotton was in full foliage and more than 1
meter in height, tending to form a protective canopy around the sampling
unit; and, the nature of the sampler is such that air enters the system
through an inverted J-shaped tube. It is likely this sampling device is
selective for finer droplets. Consequently, the larger droplets being
released over the target area would have a greater tendency to impact
quickly and not be drawn into the sampler. The finer droplets tend to
remain suspended for a longer period and 9rift from the target field
with prevailing air currents, subsequently to be drawn into off-site
sampling devices. In general, these results indicate that spray drift
resulting from this application was most intense to the north and east.
In addition, a lesser amount (6.3 ~g) of ethyl and methyl parathion
drifted south into the alfalfa field.
Residue analysis of the high-volume filters revealed the presence
of Azodrin, ethyl and methyl parathion at all stations (90, 96, 101,
105) [Table 7J. Drift was most intense to the north (station 90), east
(station 96), and west (station 105) where total pesticide residues of
\
1,290, 342 and 604 ~g, respectively, were captured. As all other data
have indicated, southern drift (station 101) was strikingly lower by
comparison, having a total pesticide residue of. only 31 ~g.
-------
TabZe 7
PESTICIDE RESIDUE ANALYSES
FieZd "B"
IMPERIAL VALLEY, CALIFORNIA
August 1976
Total Residue Ethyl Parathion Methyl Parathion Azodrin
16.9 12:0 4.9 ND*
14.1 9.3 4.8 ND
9.1 6.4 2.7 ND
6.3 4.0 2.3 ND
2.45 1.7 0.75 ND
1290 360 110 820
342 96 26 220
31 11 4 16
604 110 54 440
3.16 0.56 0.20 2.4
0.22 0.18 0.04 ND
31. 5 16 3.5 12.0
11.4 4.6 1.4 5.4
2.9 1.1 0.2 1.6
0.1 0.09 0.01 ND
0.04 0.04 ND ND
0.03 0.02 0.01 ND
95.0 4.0 1.0 90.0
4.1 1.3 0.36 2.4
0.71 0.6 0.01 0.1
Station No.
Sample Type
Greenburg-Smith Impinger (pg)
90
93
96
101
105
90
96
101 .
105
High-Volume Filter (pg)
Thermofax Droplet Card (pg) .
87
88
93
94
96
99
100
101
105
106
108
Environmental Samples
68
70
93
93
103
101
Water ()Jg/l)
Wa ter ()Jg/l)
Soil ()Jg/g)
Vegetation ()Jg/g)
Vegetation (pg/g)
Vegetation (pg/g)
Detection Limits
Greenburg-Smith Impinger
High-Volume Sampler Filters
Soil & Vegetation .
Water
Thermofax Cards
" Not Detected.
ND ND ND
ND ND ND
ND ND ND
2.15 0.06 0.09 2.0
0.21 0.003 0.01 0.2
0.18 0.04 0.03 0.11
Ethyl Parathion Methyl Parathion Azodrin U1
O.Ol)Jg O.Ol)Jg O.l)Jg w
O.Ol)Jg O.Ol)Jg O.l)Jg
0.002)Jg/g 0.002)Jg/g 0.02)Jg/g
O. l)Jg/l O.l)Jg/l 50 )Jg/l
O.Ol)Jg O.Olpg O.l)Jg
-------
54
As previously discussed, droplet card counts alone can be misleading
when attempting to quantify relative drift. . In an attempt to use droplet
spray cards for comparative data, the Thermofax papers were extracted
and analyzed for pesticide residue. There are several apparent advantages
. .
in this method of residue detection when compared with vacuum type air
sampling devices (Greenburg-Smith impingers and high-volume filters).
The spray cards are exposed on raised platforms and are afforded.no
protection by the cotton foliage. The spray card is not dependent on an
artificially produced air stream to draw the particles to it and is,
therefore, not selective to a particular size range of spray droplets.
Lastly, vacuum-type air samplers tend to concentrate pesticide residue
whereas spray droplet cards retain only that residue which actually
impacted at a given site. A non-technical aspect to be considered is
that spray cards cost a few pennies each, whereas air samplers cost
several thousand dollars. A disadvantage is the possible degradation of
photosensitive pestic~des if the cards are not retrieved within a few
hours; however, this factor is compensated for because the possibility
of hydrolysis, as occurred in the Greenburg-Smith devices, is reduced.
lhe spray droplet card located on the target field (station 93) had
a total pesticide residue (Azodrin + methyl and ethyl parathion) of 31.5
~g [Table 7]. Station 94 located east of field "B" in a private orchard
and livestock compound had a total pesticide residue of 11.4 pg, inferring
that this off-field site received spray drift amounting to 36% of that
deposited on droplet card in the target field. That this off~field site
. .
received such a large amount of drift is primarily due to the fact that
it is bordered closely on two sides by the cotton field. The intense
drift resulted from the necessity of trimming the target field from two
directions, both bordering the orchard area [Fig. 22J. By comparison,
the spray card at the domestic residence (station 108) approximately 60
m north and 30 m west of the orchard, had a total residue of 0.71 ~g;
only 2.2% of the comparable target field card. Although the total
residue at station 94 was 16 times greater than that of ,station 108, the
droplet count differed by only 22%.
-------
r
'0 D
o
~ --
C)
. ,
~'O' "
, ". '.' .'.
.I,: -:0-..
" '.$' t
o
..
~' tJ
,-
, .
" .: L
,-:, i
":J..
. ' .
.
. ..
. '
.
-0 C)
0° 0
. .
. .
. ()
Q ..
. 0
- 0 '"
Station 93
(Treated Field)
. .
..-
;-~ ,.
'1~~.
~.."'..~--
, "."-
. ::~.
. .
. ,
III
e
o
.
.
.
C)
Station 94
(Private Orchard)
o
.
o
~
II
1-----1
l1li
.
II' ~.
-
G>
o
.
.
Station 98
(Pathway Used by Flagger)
.
. i
t-----4
.
Station 108
(Domestic Residence)
.'
"'" .
Station 90
(Alfalfa Field)
Figure 22.
Visually enhanced pesticide spray
droplets on Linagraph cards (lOX).
I
."'-
55
~ ~.
.'.
III
II
.
.
o
o
.
.
-------
56
Drift to the southt where pesticide residue on the spray cards
averaged 0.06 pg (stations 99t lOOt 101) t was less than in other directions.
The residues at stations 105 and 87 are notable in that they reflect the
effect of the unexpected second application. Of the total pesticide
residuet the Azodrin fractiont accounted for 76 and 97% at stations 87
and 105t respectively. Stations 93t 94t and 96 located at the extreme
eastern area of field IIBllt remote from the second applicationt had
Azodrin residues averaging only 47%. The drift at station 105 was of no
consequence because this station is virtually on the edge of the cotton
field west of field IIBII. Heret drift was simply from one cotton field
to another. Howevert station 87 is a domestic dwelling and received
total pesticide residue equivalent to 10% of the target field sample.
This stationt with a 76% Azodrin fractiont obviously received drift from
both applications.
The pesticide residue values evaluated in this section are only
comparative and do not reflect actual total pesticide residue. These
spray cards were not analyzed for either Nudrin or Fundal t which were
present in the first and second applicationst respectively. If these
compounds were also taken into accountt the actual pesticide residue
would undoubtedly be greater.
Analysis of environmental samples [Table 7J showed no pesticide
residue on the soil of field IIBII (station 93). Cotton leaves from the
field contained pesticide residue at concentrations of 0.06 pg!g ethyl
parathiont 0.09pg!g methyl parathiont and 2.0]Jg!g Azodrin. Alfalfa
foliage at stations 101 and 103 had pesticide residues of ethyl parathion
of 0.04 and 0.003 pg!gt methyl parathion 0.03 and O.01pg!gt and Azodrin
of 0.11 and 0.20 pg!g. These values demonstrate that even when prevailing
air currents were away from the sensitive area and the pilot obviously
attempted to prevent driftt total pesticide residue on the alfalfa
foliage averaged 9% of that which was found on the target cotton plantt
and also that total drift control cannot be achieved.
-------
57
The alfalfa field directly northof field "B" may have received
pesticide drift at levels that may be of concern. Stations 90 and 101
[Fig. 3J are directly opposite each other at the north and south perimeter
of field '"B". At station 101, where alfalfa foliage had pesticide
residue equivalent to 8% of the target cotton plants, total pesticide
residue on the high-volume fi.lter was only 31 jlg. Station 90, within 15
m of the alfalfa field to the north, had a high-volume filter total
pesticide residue of 1,290\1g; approximately 42 times greater than at
station 101. This implies that the alfalfa field to the north, directly
in the path of the prevailing air currents, feceived pesticide residue
greatly in excess of the 9% observed at stations 101 and 103.
The in-situ fish exposures were terminated on August 31. The AChE
activities for fish exposed in the lateral canal (station 70) and drain
(station 68) were 1.44 and 1.40, respectively. No AChE inhibition resulted
from exposure at either site. Both of these exposures were directly in
line with a spray drift much more intense than the exposures at field
"A" with no resulting inhibition. This fact reinforces the hypothesis
that AChE inhibition found during the field "A" exposures resulted from
surface or drain tile runoff, and not spray drift.
METROPOLITAN DRIFT POTENTIAL
A cooperative investigation involving the Imperial County Agricultural
Commission and EPA was undertaken to assess the possibility of pesticide
drifting into the metropolitan areas of Imperial Valley.
Permanently installed high-volume air samplers, maintained by the
Agricultural Commission, were used to obtain 24-hour samples of ambient
air at Brawley, Calexico, and El Centro, California. The air samplers
. .
were located atop the fire stations at Brawley and Calexico, and on the
roof of the County Health Building at El Centro.
-------
58
Three sets of 24-hour samples were
August 28, 1976. The fiberglass sample
residue analysis.
taken on July 20, August 5, and
filters were sent to' NEIC for
Chemical analysis revealed measurable quantities of pesticide
residue at all sampling sites during all sampling periods [Table 8].
Overall pesticide levels were higher at Brawley and Calexico, with
residue concentrations for the three sampling periods averaging 3.48 ~g
(range 1.14 to 5.59 ~g) and 2.88 ~g (range 0.16 to 6.34 ~g), respectively,
as compared to 0.26 ~g (range 0.17 to 0.32 ~g) at £1 Centro. At Brawley
and Calexico, the highest pesticide levels captured (5.50 and 6.34 ~g,
respectively) were on August 5. The El Centro air sampler operated only
six hours during the July 20 period, but produced the highest total
pesticide residue at this station for the three sampling periods. This
indicates that either the spray drift was considerably more intense on
this date or that the major portion of the pesticide residue is present
in ambient air during the morning. Additional sampling should be done
at shorter intervals to determine which of the above hypotheses is
correct.
Since this was a preliminary investigation and consisted of few
samples, only one definitive statement is justified: pesticide spray
drift does enter metropolitan areas of Imperial Valley. Residue analyses
were made for only three specific compounds: methyl and ethyl parathion,
and Azodrin; therefore, these data represent minimum residue levels. In
view of the large variety of pesticides used in Imperial Valley, total
pesticides in the ambient air were, undoubtedly higher.
These data are insufficient to project any possible environmental
hazard which may result from spray drift, nor were the samples numerous
enough to determine if these pesticide levels are representative of
those normally present in the air.
-------
Table 8
METROPOLiTAN HIGH VOLUME AIR SAMPLES
IMPERTAL VAiLEY~ CALIFORNrA
Location
Date
Tota 1
Pesticide Residue Ethyl Parathion Methyl Parathion Azodrin
(].1g) (].1g) (].1g ) (].1g)
3.8 ND* 0.10 3.7
0.16 . NO 0.06 0.1
0.32 NO NO 0.32
5.5.9 NO 0.40 5.5
6.34 5.5 0.28 0.56
0.17 ND ND 0.17
/
1.14 NO 0.20 0.94
2.14 NO 0.14 2.0
0.28 NO ND Q.28
Brawl ey
Calexico
E1 Centro**
20 July 1976
Brawley
Ca1exico
E1 Centro
5 August 1976
Brawl ey
Ca1exico
E1 Centro
28 August 1976
* Not Detected.
Detection Limits: Methyl Parathion O.Ol].1g~ Ethyl Parathion O.Ol].1g~ AzodPin O.10].1g.
** This Sampler operated only six hours~ from 0600-1200~ July 20~ 1976.
(J'I
\.D
-------
60
A realistic assessment of the environmental impact of pesticide
drift into populated areas should be made by instituting a long-range,
intensive sampling program (minimum of 12 months). Twenty-four-hour
sampling periods should be divided into at least six consecutive four-
hour intervals. Pesticide residue analyses would have to be expanded
into a broad spectrum to encompass the entire range of pesticides being
applied during the sampling period.
-------
VI. EVALUATION OF METHODS
AIR SAMPLING DEVICES
Greenburg-Smith impinger units and high-volume air samplers both
proved capable of capturing pesticide drift; however, the high-volume
sampler wa~ considerably more efficient. There are several obvious
advantages in using the high-volume air sampler: movement of air
through the system is at least 40 times greater than in the Greenburg-
Smith impinger; pesticide material is captured on a dry fiberglass
filter, reducing the possibility of hydrolysis of the pesticide; and
residue analyses are simplified when extractions are made from a dry
medium. A disadvantage of the high-volume system is that the rapid
air movement through the filter may tend to evaporate highly volatile
pesticide material, and pesticide vapors may not be captured.
FLUORESCENT TRACER TECHNIQUES
Use of fluorescent tracer material (Rhodamine Wi dye) was not
effective. Analyses of ethylene glycol samples from the Greenburg-
Smith impingers and solution washes of the high volume filters and
mylar sheets produced erratic, low level or non-detectable fluorescent
response. In contrast, pesticide residue analyses of samples .from the
Greenburg-Smith impingers and high-volume air samplers as well as
visible droplet images on the mylar sheets confirmed that the pesticide.
spray mixture was captured by all three sampling devices. It appears
that dye concentration mixtures ranging from 1,000 to 2,000 ~g/l are
not sufficient for accurate fluorescent determinations. It is also
possible that the concentration of dye necessary for accurate detection
may be so great as to prohibit its use in areas where the appearance
-------
62
of visible dye residue on sensitive crops or structures would be unde-
sirable.
MAGNESIUM-OXIDE-COATED SLIDES
The use of magnesium-oxide-coated glass slides to determine drift
characteristics and spray droplet size was not satisfactory in this
study. However, the failure of this device was due to local environ-
mental conditions, not the insensitivity of the slides to detect drift.
When used in studies in areas where gusting wind and abrasive dust were
not encountered, the method proved to be effective. Because the device
is fragile, future use of magnesium-oxide-coated glass slides must be
considered on a site-specific basis.
SPRAY DROPLET CARDS
All types of spray droplet cards used were effective to varying
degrees in characterizing spray drift. Kromecote cards were the least
effective; they appeared to be sensitive only to a particular pesticide
mixture. Because of this limitation, extensive use of this card in
future studies is not advisable.
Linagraph and Thermofax cards proved equally successful in recording
spray droplet impressions. Acknowledging that these produce similar
droplet counts, Thermofax cards have several characteristics which make
it the more desirable droplet card material. These factQrs. are:
droplet impressions on a Thermofax card are a distinct brownish color
against an off-white background. The color combination in conjunction
with a finer paper texture produce an easily detectable droplet image,
facilitating visual counting. Linagraph cards have a coarset' texture
and droplet impressions appear as dark gray images. The background,
while initially a buff hue, gradually darkens upon exposure to sunlight
to a medium gray color and makes droplet impressions more difficult
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63
to detect visually. Furthermore, residue analysis of Linagraph versus
Thermofax cards indicates laboratory pesticide extraction efficiency
for Thermofax is superior. For this study, results of pesticide residue
, .
on Thermofax paper were used only as comparative, not absolute, values.
Additional studies need to be performed to determine the degree to which
quantitative results can be expected from this method.
It is possible to obtain quantitative data from spray droplet images
. imposed on paper material. However, the specific spread factor (through
blotting action, the degree to which the image of a liquid droplet will
increase in size on a porous medium) for each pesticide mixture and
droplets1ze, range first must be determined. At present, NEIC does
. not have the capability of determining specific spread factors. However,
the EPA has contacted a government-contracted laboratory that currently
has a functional program for the computerized analyses of spray droplet
cards. The technique (QUANTIMET) is quantitative. By incorporating
specific spread factors, it is capable of providing data consisting
of droplet image size for each analysis and selected sub-groups of
analyses: category size, droplet count in each category, droplet
size and mass, cumulative mass percent, total mass, and deposition
densities in mg/cm2 and oz/acre. The cost of this analysis, approxi-
mately $2.50 per card, is moderate in view of the quality ~nd quantity
of data obtained. Use of this technique will be incorporated in any
further use observation studies undertaken by NEIC.
ENVIRONMENTAL SAMPLING
Residue analysis of environmental samples (water, vegetation, soil
and sediment) was useful in substantiating the encroachment of spray
drift into sensitive areas. It has also proved to be an aid in determi-
ning the mode of pesticide material translocation.
The in-situ exposure of live fish, and subsequent analysis for AChE
activity was shown to be a sensitive test for indicating the presence
of organophosphate compounds in the aquatic environment.'
-------
64
Results of these analyses indicate that pesticide residues exist in
sufficient concentrations to have environmental impact.
OBSERVATION AND PHOTOGRAPHS
Observers equipped with cameras proved to be a valuable asset in
this study particularly for recording mixing and loading procedures,
storage, and disposal facilities for pesticides and clean-up operations.
The use of multiple observers to document the application was of little
benefit because all spraying was done at night and visibility was poor.
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65
REFERENCES
1.
Imperial Irrigation District, Ed. The Colorado River and Imperial
Valley Soils. Bulletin No. 1075, 24 p.
2.
Imperial Irrigation District Community and Special Services,
Ed. Imperial Valley California. Bulletin No. 1075, 16 p.
3.
Environmental Protection Agency Regions VIII and IX, 1971. The
Mineral Quality Problem in the Colorado River Basin, Appendix A.
Environmental Protection Agency, 1972. The Effects of Agricultural
Pesticides in the Aquatic Environment, Irrigated Croplands, San
Joaquin Valley. USEPA Report No. TS-00-72-05, 268 p.
4.
5.
Environmental Protection Agency, 1975. A Study of the Efficiency
of the Use of Pesticides in Agriculture. USEPA Report No. 540/9-
75-025, 240 p.
6.
Pest Control: Vol. III Cotton Pest Control, 1975, National Academy
of Sciences. Wash. D. C., 139 p.
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Appendix
Description of Sampling Devices and Methods
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01
DESCRIPTION OF SAMPLING DEVICES AND METHODS
GREENBURG-SMITH IMP INGER
The Greenburg-Smith impinger is a semi-quantitative air sampling
device. The system consists of an air compressor arranged so the intake
manifold draws air through a sampling train, and auxiliary equipment
to control and measure air flow and switch the flow from one impinger
to another after a preset time interval. The sampling train consisted
of 3 glass impingers each containing 100 m1 of ethylene glycol to capture
pesticide material. An absorption tube packed with glass wool prevented
splash-over or water condensation from being drawn into the compressor.
After the air was pulled through an impinger, it passed through a
solenoid valve controlled by a timer, through a control valve by which
the air flow was set at the desired rate as shown on a flowmeter,
through the flowmeter and finally througn the compressor. 'A momentary
contact switch may be closed to switch the air flow to a particular
impinger so that its flow may be adjusted and read at any time.
To avoid contamination, impinger units were filled with 100 ml
of ethylene glycol at an off-field staging area and the intake tubes
sealed with pesticide-free aluminum foil. The timing mechanism was
adjusted to provide three four-hour sampling periods and air flow was
calibrated to 1.0 ft3(.028m3)/min. The first impinger cycle was
activated four hours prior to the intended application. The second
impinger cycle was activated during the loading of the spray plane
and the units were then allowed to cycle automatically through the
four-hour post application interval. At the completion of the cycle,
the ethylene glycol was removed from the impingers and stored in
separate 125 ml glass, screw top bottles. A 25ml aliquot of the
ethylene glycol was removed and analyzed at the field laboratory for
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fluorescence and the reamining sample was returned to the NEIC laboratory
for residue analysis. After each application, all COITtact components
in the sampling train were disassembled, washed with detergent and
thoroughly rinsed with fresh wat~r.
HIGH-VOLUME SAMPLERS
The high-volume air sampler uses a high-speed impeller to draw air
through a 20 x 25.4 cm fiberglass filter on which airborne particles
are trapped. The samplers were activated just prior to the application
and operated for eight hours, drawing air through the filter at a rate
of 35 ft3 (0.98~3) min. Filters were removed, stored in plastic bags
and returned to NEIC for residue analysis.
SPRAY DROPLET CARDS
o
Spray card clusters were constructed-by taping rectangular sheets
of Kromecote, Linagraph, Thermofax and mylar onto a 30 cm (12 in)
square cardboard base. The clusters were mounted with rubber bands
atop a l-m upright wooden platform.
Kromecote cards are a 10 x 12.5 cm finely textured, glossy photo-
graphic paper. They are dependent primarily upon deposition of tracer
dye material to produce a droplet image. However, this and previous
studies have shown Kromecote to be sensitive to parathion compounds.
Linagraph (480) cards are a more coarsely-textured, non-glossy
photographic paper 15 x 25 cm in size. This paper is extremely
sensitive to water droplets and produces a visual image within minutes
of droplet contact.
Thermofax paper (209 copy, type 640) is a medium-textured, temperature
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activated material sensitive to both water and to petroleum-based drop-
lets. Spray droplet cards were cut from large sheets into 10 x 12.5 cm
rectangles. Several hours of exposure to moderate heat are required
to produce a droplet image. Norm~l bright sunlight at Imperial
Valley produced sufficient temperature to develop the cards; however,
cards may be developed by exposure to incandescent lights or a low
temperature drying oven.
Droplet counts were done at NEIC using a 30X binocular dissecting
microscope. Cards with low numbers of droplet images were counted in
entirety; however, for high density images four or more random 2.5 cm2
(1 in2) areas of the card were counted and the average value calculated.
Final counts were expressed as number of droplets/cm2.
Spray droplet cards made of 10 x 30 cm mylar sheets (commercially
available plastic sheeting 5 mils thick commonly used by draftsmen)
were used to collect spray droplets for fluorescence analysis of
tracer dye material (Rhodamine WT).
FLUORESCENCE ANALYSIS
Field laboratory analysis for fluorescent response of dye tracers
was done using a Turner Model 111 fluorometer with a high sensitivity
door. Sample material from the Greenburg-Smith impingers was analyzed
and compared with an ethylene glycol blank. Mylar sheets and high-
volume filters were washed with 100 ml of 95% ethyl alcohol and
fluorescent response compared to an ethyl alcohol blank solution.
MAGNESIUM-OXIDE-COATED SLIDES
Glass microscope slides were coated with magnesium oxide by
burning thin strips of magnesium metal beneath the slide. Upon impact
with the stationary slide, airborne droplets create visible impressions
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in the powder coating leaving a permanent record even after evaporation.
Craters formed by the droplet can be measured to within .5 ~ by use
of a microscope, measuring 200 impressions on each slide. These data
can then be used to compute the volume median diameter of the spray
mixture and estimation of drift potential.
ACETYLCHOLINESTERASE INHIBITION TESTS
Evaluation of AChE inhibition in channel catfish (Ictalurus
punctatus) was accomplished by exposing twelve fish for four- to five-
day intervals at each of seven stations in the river, drains and canals
in the vicinity of the study fields. Fish used in the study were
obtained from the California State Warm Water Fish Hatchery at Niland
and ranged in size from 12 to 15 cm total length. .
After the exposure period, the fish were removed from the cages
and transported live to the field laboratory facility where the brains
were removed for AChE analysis.
The principal equipment used for AChE analyses is a recording
pH-stat. Briefly, the procedure was: brains of 3 fish from the same
exposure site were pooled, wet-weighed, and homogenized in distilled
water. The brei was diluted with distilled water to a final tissue
concentration of 5 mgjml. Four ml of diluted homogenate was then
mixed with 4 ml of acetylcholine iodide (a specific substrate for
the enzyme AChE). The pH-stat was used to titrate the acetic acid
end-product of the anzyme substrate reaction with O.OlM NaOH. The
test was performed at pH 7.0 and 22°C with a nitrogen purge over the
surface of the reaction vessel to prevent absorption of atmospheric
carbon dioxide.
Micromoles of acetylcholine hydrolyzed was calculated from the
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micromoles of NaOH required to neutralize the
The AChE activity was expressed as micromoles
hydrolyzed per hour per mg of brain tissue.
/
free acetic acid.
of acetylcholine
71
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