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OCR for page 228
Chapter 9
TRIFLURALIN AND ORYZALIN
NO2
~ /CH2 CH2 CH3
F3C - / \ - N
\=< \CH2—CH2—CH3
NO2
NO2
,: CH2—CH2—CH3
// \\ /
NH2.O2 S - ( IN
CH2—CH2—CH3
NO2
Trifluralin (a, a, ~-trifluoro-2 ,6-dinitro-N,N-dipropyl-~
toluidine; also known as Treflan) and oryzalin (3, 5-dinitro-N4,
N4-dipropylsulfanilamide) are both members of a class of compounds
known as dinitroanilines. Trifluralin is an orange crystalline solid
that melts at 49°C. It has a low solubility in water (0 .3 ppm) and a
low vapor pressure (2 x 10 4 mm Hg at 30°C). Oryzalin is a
yellow-orange crystalline solid that melts at 141°C. It has a much
lower vapor pressure (less than 10 7 mm Hg at 30°C) than
trifluralin, but is slightly more soluble in water (2.5 ppm at 25°C).
Trifluralin is produced via a ser ies of reactions beginning with
the reaction of hydrogen fluoride with E~chlorotoluene to produce
4-trifluoromethylchlorobenzene. The latter compound is then nitrated
followed by reaction with di-N-propylamine, which replaces tbe
chlorine to form trifluralin. me production of oryzalin begins with
the nitration of E:chlorobenzenesulfonic acid, followed by the
addition of chlorine to form 2,6-dinitro-E~chlorobenzenesulfonyl
chlor ice, followed by the addition of ammonia and di-N-propylamine to
yield oryzal in .
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PRODUCTION
Eli I`illy and Co. {Elanco Products Division) is the sole U. S .
producer of tr if luralin (Stanford Research Institute International,
1979 U.S. International Trade Commission, 1978~. The plant at
Lafayette, End., has an estimated 23,000-metric ton capacity for
production of trifluralin.
Lilly owns the patent rights for oryzalin, but has contracted
production to various other firms since receiving approval of
oryzalin use in 1975. GAF Corporation made oryzalin for Lilly at
Rensselaer, N.Y., from January 1975 to June 1976 (Chemical Week,
1979~. Proctor Chemical at Salisbury, N.C., produced oryzalin from
January 1975 to January 1976. The U. S. International Trade
Commission listed the Sodyeco Division of Martin Mar ietta
Corporation, Sodyeco, N.C., as a producer of oryzalin in 1977 and
1978. Other processors and formulators of oryzalin for Lilly have
included Bold Chemical of Tifton, Gal, Central Chemical of
Hagerstown, Ark., and Helena Chemical of Helena, Ark. (Chemical Week,
1979~. Although no estimates of production capacity are available
for these plants, the production of trifluralin in 1975 and 1978 is
estimated at 12, 000 and 16, 000 metr ic tons, active ingredient,
respectively. Oryzalin production in 1975 is estimated at 45 mete ic
tons, active ingredient; 1978 production is estimated at 450 metric
tons of active ingredient.
229
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U_
Trifluralin and oryzalin are both used almost exclusively as
herbicides. Consumption estimates for each in 1978 are shown in
Table 9-1.
The Environmental Protection Agency {EPA} teas approved both
trifluralin and oryzalin for use as herbicides; however, both
compounds have been challenged on several occasions. Trifluralin was
challenged on the grounds that it contained nitrosamine contaminants
and that its use therefore posed an unacceptable carcinogenic risk.
Risk-benefit studies initiated by EPA concluded that benefits of
trifluralin outweigh any risks if nitrosamine contamination is kept
below 1 ppm (Chemical Marketing Reporter, 19791. Subsequently, Lilly
has produced trifluralin with a nitrosamine content of less than 1
ppm, and has continued to receive approval for its use as an
herbicide.
Oryzalin has been suspected of causing heart-related birth
defects among children fathered by workers involved in its
manufacture and of causing skin rashes in workers. However, EPA
investigations did not disclose any adverse effects, and no
regulatory action is planned (Chemical Marketing Reporter, 1980~.
Nonetheless, Lilly is required to maintain ongoing teratological
studies to support the continued registration of oryzalin (Pesticide
and Tbxic Chemical News, 1980~.
230
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Table 9-1
Consumption of Trifluralin and Oryzalin
Percent of
Product Conta in ing compound
Tr if luralin
103 Metric Ton. of
Active Ingredient
Cotton 21. 2 . 7
Deciduous fruits/nuts 1 0 .05
Peanuts 1 0.1
Soybeans 7 4 9 · 7
Sugar beets 1 0.05
Vegetables 2 0.3
Other f ield crops 1 0 .14
Industr ial/co~ercia 1
0.1
Total 100 13.1
OrYzalin
Cotton 10 0.05
Deciduous fruits/nuts ~ 10 0.05
Soybeans 60 0.27
Industrial/commercial 20 0. 09
Total 100 0 .45
Stanford Research institute, 1979
231
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EXPOSURE
The principal routes of exposure to trifluralin and oryzalin are
the following: workers are exposed dur ing n~anufactur ing process ;
agricultural workers are exposed while applying~the substances to
crops; and the general public is exposed through releases of the
compounds into air and water during manufacturing processes, through
drift, volatilization, and runoff as a result of application, and via
contaminated food crops. Because more trifluralin is used than
oryzalin, and because much more data about trifluralin exist, this
chapter focuses on exposure to trifluralin.
Trifluralin is produced at a single site in Lafayette, Ind.
(population, 45,000~; thus, exposure of the public to trifluralin
during its manufacture is of only local importance. Although no data
are available on trifluralin plant discharges, small quantities are
known to be discharged into the Wabash River as waste from the
manufacturing processes. m e treatment procedure involves activated
sludge, followed by settling, and then filtration through activated
carbon (Specie and Hamelink, 19791.
Parts per trillion (ppt) concentrations of trifluralin have been
measured in the water downstream from the plant. However, the
tissues of fish captured in these waters contain concentrations of
trifluralin several thousand times greater than those in the water
(Specie and Hamelink, 1979~.
232
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The most likely source from which the general public is exposed
to trifluralin is the herbicide's application to soils to control
grass and broadleaf weeds. This is practiced primarily in the North
Central and South Central States, especially in Illinois, Iowa, and
Mississippi (Helling, 1976~. ~
Trifluralin is not an especially persistent chemical. m ere have
been some studies of the persistence of trifluralin in soil under
actual field conditions (Golab et al., 1979; Golab and Amundsen,
1975; Probst et al., 1967) These studies show that trifluralin
concentrations decreased from 10% to 15t of their original value 1
year after application. Trifluralin is lost through volatilization
as well as through degradation. At this rate of loss, trifluralin
does not tend to accumulate in soils receiving repeated applications.
Although the rate of volatilization of trifluralin depends to a
great extent on the method of its application, such dissipation
provides a signif icant potential exposure route for persons living
downwind of treated f ields . If trifluralin is applied to the soil
surface, up to 90% of the compound may be volatilized within 2-3 days
of application . If it is incorporated into the soil, volatilization
losses can be as little as 3% or 4% in 90 days (Taylor, 1978~. In an
experiment in which trifluralin was sprayed onto soil and then tilled
into the soil, White et al. t1977} measured ~ maximum concentration of
16.5 Ug/m 3 20 cm above the soil during application. The maximum
concentration was 3.4 ~g/m 3 20 cm above the soil on the second day
233
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after the compound was tilled into the soil, decreasing to 100
ng/m 3 after the 35th day. They estimated total volatilization
losses to be at 22.41 during the growing season (120 days) and vapor
losses during spraying to be at 3.58.
Exposure of persons living downwind of sprayed fields is somewhat
reduced because trifluralin is subject to fairly rapid photochemical
decomposition. Measurements of trifluralin degradation in air
indicate a balf-life of 20 minutes under midday summer sunlight
conditions. Woodrow et al. {1978} observed that the half-life
increased to 193 minutes in the fall. Trifluralin is stable in the
dark.
Although relatively immobile in soil, trifluralin may be
transported long distances from its initial source of application via
runoff into streams and rivers. Indeed, trifluralin has been detected
at levels of up to 0.2 ~g/1 in the Cape Fear River, N.C.
Trifluralin concentrations tended to correlate with periods of
greatest runoff and soil erosion on agricultural lands adjacent to
tributaries of that waterway {Horder, 19771. Although there is
probably minimal direct exposure.of humans via this route, the
tendency of trifluralin to accumulate in fish must not be overlooked
(Specie and Hamelink, 19791.
Humans may also be exposed to trifluralin through food crops
treated with the herbicide. However, analyses of residues in a wide
variety of tolerant crops indicate that trifluralin is not
234
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incorporated into the leaves, seeds, or fruits (measurement
sensitivity, 5-10 ppb). In treated root crops, such as onions and
garlic, trifluralin residues are found only in the outer shell, which
is usually discarded before consumption. me exception is carrots
~ :
31% of the total residue of 0.65 ppm was found~in the interior of the
carrot proper--69% was concentrated in the peel (Protest et al., 1967)
235
.
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ANALYTIC METHODS
Methods to analyze trifluralin in a variety of vegetables, plant
tissues, soil, water, oily crops, wheat grain and straw, and mint and
mint hay are described in the Pesticide Analytical Manual of the Food
and Drug Administration (1973~. Trifluralin is extracted from crops
by blending it with methanol and subsequent extraction from the
solvent into dichloromethane. After evaporation of the
dichloromethane, the extract is dissolved in hexane, cleaned up on a
column of Florisil, and analyzed by electron-capture gas
chromatography (EC-GC). GC columns (1.83 m) packed with 3% XE-60 or
5t SE-30 on Chromosorb W are used at approximately 180°C with the
carrier gas flowing at 90 ml/minute. The retention time (tR, for
trifluralin is 3 to 4 minutes. The analytic procedure is modified as
required for aqueous or oily samples. Recoveries of approximately
80% or more can be expected, and the sensitivity ranges from 5 to 10
ppb. Samples containing residues of benzene hexachloride, ethion,
and/or zineb require additional cleaning. The interfering compounds
are separated by thin-layer chromatography (TEC). Ihe trifluralin- is
then scraped from the plate, elated, and assayed by EC-GC.
The procedure used at North Carolina State University (T.J.
Sheets, North Carolina State University, personal communication,
1980) to determine trifluralin residues in soils requires a 4-hour
Soxhlet extraction of the oven-dried sample with benzene-isopropyl
alcohol (1:2~. The extract is evaporated just to dryness, dissolved
in hexane, cleaned on a Florisil column and subsequently analyzed
236
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by EC-GC. Glans columns {1.83 m long 0.635 cm outside diameter)
packed with 4% SE-30 plus 61 QF-1 or with 51 Carbowax 20M on Gas
Chrom Q are opera ted at 155°C with a Me flow of 80 to 100
ml/minutes. Under these conditions, the tR for trifluralin is
approximately 2.0 minutes.
Recently reported analytic methods have focused mainly on GC
techniques, coupled with various types of detectors including mass
spectrometers. Payne et al. (1974) developed a procedure to analyze
trifluralin, diphenamid, and paraguat in admixture in soil,
sediment, and water. The procedure permits simultaneous GC assays
of trifluralin and diphenamid, without cleanup, by employing a
Couison electrolytic conductivity detector. Paraquat is determined
calorimetrically. m e 1.83 m long glass GC column (0.635 cm
outside diameter) was packed with 10% DC-200 on Gas Chrom Q.
Recoveries of trifluralin spiked into water at concentrations of
O .05 to 10 ppb were 82% to 91%; those from soil spiked at 0 . OS and
1.0 ppm were 861 and 941.
Smith (1974 ~ used acetonitr ire-water (9 :1) and ultrasonication to
extract residues of four herbicides, including trifluralin, from
three types of soil. ffl e addition of excessive amounts of water and
saturated sodium sulfate solution to the extract facilitated
subsequent partitioning of the herbicide residues into hexane. me
hexane extract was then concentrated and assayed by EC-GC. The GC
system consisted of ~ 1.5 m long glans column (6 ~ outside
diameter), packed with 10% OV-1 on Q~romosorb G-HP operated at
237
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ml/minute, tR's for dichlorobenil, trifluralin, dinitramine, and
triallate were approximately 1.0, 2.9 , 4 . 5 , and 5.0 minutes,
respectively. Recoveries of all four compounds spiked into the
three types of soil at 0.05 and 0.5 ppm levels were 92% or more.
Lawrence (1976) examined the separation characteristics of
Several GC liquid phases (i.e., 31 OV-1, 4% SE-30-6. SP-2401, 10%
DC-200, and 5% DEGS on Chromosorb W HP) for 12 pesticides, including
trifluralin, by using the Coulson detector. Sensitivities (50%
scale) for trifluralin at a tR of approximately 3 minutes on OV-1
at 175°C were reported as 6 ng and 3 ng for the nitrogen and
chlorine modes, respectively. Later, Lawrence et al. (1977)
reported a confirmatory procedure for pesticides that contain
nitrogen dioxide (NOW. ate pesticide residue in ~ m] of benzene
was shaken with 0.5 ml of aqueous chromous chloride to convert the
NO2 groups to NH2. me solution was made basic and the product
extracted with benzene for analysis by GO with a Coulson detector
(nitrogen mode). The products were found to be approximately as
sensitive as the parents and had tR values of 0.4 to 0.9 minutes
relative to the parent compound on the SE-30/SP-2401 column. The
procedure was used to confirm trifluralin residues in extracts of
potato spiked at levels of 0.5 to 1.0 ppm.
Woodrow et al. (1978 ~ used EC-GC to study the behavior of
trifluralin vapors released into the atmosphere as emulsifiable
concentrate sprays. The experiment wan conducted with a 1.8 m long
glass column (3 mm, internal diameter), packed with 3% OV- 17
238
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REFERENCES
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Horden, W. 1977. A Report on the Ose of the Macroreticular Resin
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Wnite, A.W., Jr., L.A. Harper, R.A. Leonard, and J.W. Turnbull.
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Analytic Methods
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Food and Drug Administration. 1973. Pesticide Analytical Manual.
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Separation by sequential high-pressure liquid chromatography and
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of major interest in Canada, with electrolytic conductivity
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85-87.
Lawrence, J.F., D. Lewis, and H.A. McLeod. 1977. Confirmation of
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Payne, W.R. , Jr. , J.D. Pope, Jr. , and J.E. Benner. 1974. An
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266
OCR for page 267
Smith, A.E. 1974. A aulti-residue extraction procedure for the gas
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267
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Health Effects
Andersen, K.J., E.G. Leightly, and H.T. Takahashi. 1972.
Evaluation of herbicides for possible mutagenic properties. J
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Bartels, P.G., and J.L. Hilton. 1973. Comparison of trifluralin,
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Chaisson, C.~. 1978. Summary of evidence on mutagenic potential
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273
.
Representative terms from entire chapter:
formulated trifluralin
