| Chemical Abstract Number (CAS #) |
56382
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| Synonyms | Parathion |
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Parathion-ethyl | Phosphorothioic acid, O,O-diethyl O-(4-nitrophenyl) ester | Diethyl 4-nitrophenylphosphorothioate | DNTP | Niran | Ethyl parathion |
| Analytical Method |
EPA Method 8141A |
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| Molecular Formula | C10H14NO5PS |
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| Use | INSECTICIDE EG, FOR WHEAT & NUTS; ACARICIDE
Parathion controls a variety of insects such as aphids, mites, beetles, Lepidoptera, leaf hoppers,
leafminers, and other pests found on fruits, cotton, vegetables, and forage crops. It also controls
several soil insects such as wireworms, rootworms, and symphilids.
Used for control of nematodes in beet & ornamentals
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| Consumption Patterns | INSECTICIDE FOR WHEAT, 49%; DECIDUOUS FRUITS & NUTS, 14%;
VEGETABLES, 14%; SORGHUM, 11%; COTTON, 4%; CITRUS, 1%; OTHER FIELD
CROPS EG, BARLEY & OATS, 7% (1982 AGRICULTURAL CROP USE)
(1978) 3.27X10 9 G (CONSUMPTION)
(1982) 3.90X10 9 G (CONSUMPTION)
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| Apparent Color | The pure material is a yellowish liquid at temperatures above 6 deg C
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| Odor | Usually has a faint odor ; Garlic like
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| Boiling Point | 375 DEG C AT 760 MM HG
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| Melting Point | 6 DEG C
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| Molecular Weight | 291.27
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| Density | 1.26 AT 25 DEG C/4 DEG C
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| Odor Threshold Concentration | 4.00X10-2 ppm (detection in water; purity not specified)
0.470 mg/cu m
Odor Threshold: 0.476 mg/m (low); 0.4760 mg/m (high).
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| Sensitivity Data | Irr to the eyes.
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| Environmental Impact | Parathion is released to the environment primarily in its use as a broad- spectrum
insecticide in agricultural applications although more localized releases may occur in wastewater
spills, and fugative emissions during its production, transport, storage, and formulation. When
sprayed on a field or orchard it will exist primarily as an aerosol in the source area and as a
combination of vapor and aerosol downwind. The vapor will be rapidly photolyzed (half-life 5 min
in summer sunlight) to paraoxon. The parathion residue on foliage will decay with a half life of 1
day reaching low levels in a week or two. It will bind tightly to soil and decay by biological and
chemical hydrolysis in several weeks forming p-nitrophenol, diethylthiophosphoric acid, and
paraoxon. Accumulation from repeated doses is unlikely. Photolysis may occur on the soil
surface. Degradation in flooded soil is much faster and is probably due to surface catalyzed
hydrolysis; aminoparathion is formed under these low oxygen conditions. Residues will generally
remain in the upper 6 inches of soil so leaching into groundwater is unlikely. While parathion
residues resulting from spills may decrease markedly with time, especially during the first year,
they may persist for many years. Parathion released into surface waters will be removed in
approximately a week. The primary removal mechanism is adsorption to sediment and particulate
matter where biodegradation or chemical hydrolysis will occur. While photooxidation in water
occurs with a <1-10 days half life, the presence of radicals and sensitizers which are found in
eutrophic waters may greatly accelerate this process. Bioconcentration will be low to moderate.
Human exposure will result primarily during field application and formulation of the insecticide.
Exposure will be primarily dermal and inhalation due to exposure to aerosols and vapors and from
contact with sprayed surfaces as well as by inhalation. Exposure to the general public is by
ingestion of produce containin parathion residues and from air in areas where spraying is taking
place.
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| Environmental Fate | AQUATIC FATE: PARATHION SHOWN TO BE 2-3 TIMES MORE
PERSISTENT THAN METHYL PARATHION IN NATURAL WATER SYSTEMS.
TERRESTRIAL FATE: PERSISTENCE OF PARATHION WAS PARTIALLY DEPENDENT
ON SOIL TYPE. IN SOME SOILS DEGRADATION WAS RAPID & PROBABLY
THROUGH COMBINATION OF HYDROLYSIS & STRONG MICROBIAL ACTIVITY. IN
OTHER SOILS LOSS WAS SLOW & ATTRIBUTABLE TO HYDROLYSIS.
TERRESTRIAL FATE: When applied to soil, parathion adsorbs strongly to the soil and degrades
by both biological and soil-catalyzed hydrolysis. On the surface, photolysis may occur. At
ordinary levels of application, either to soil, or to foliage, parathion is degraded within weeks and
accumulation even of repeated doses is unlikely . At very high levels of applications, or in spills,
residues will persist. After topical application of an emulsifiable concentrate (45.6%) to field plots
resulting in initial concentrations of 30,000 to 95,000 ppm, most of the residue was in the upper 6
inches of soil after 6 yr and very little was found below 9 inches . While parathion levels
dropped considerably after the first year, the rate of disappearance declined by the second year,
and appreciable quantities of the pesticide remained in the top 1 inch and 1-3 inch levels at the end
of 5 yr (lowest levels 13,800 ppm or approximately 1.4% of dose in the top 1 inch of soil) . In
another case of a simulated spill, 0.1% remained after 16 yr and little leaching occurred despite 42
inches/yr precipitation . Mean losses/day recorded in a tabulation of 23 laboratory and field
studies of 12-240 day duration range from 0.22 to 6.3% . In a terrestrial ecosystem in which
C-14 labeled parathion was applied 10 days post planting and the different compartments analyzed
10 days later, 44% of the radioactivity was found in the soil and 52% in the air . The
radioactivity in the air was probably a metabolite since little parathion volatilized from soil. After
subsequent flooding of the ecosystems, only 1% of the radioactivity was in the water after 7 days
showing that only small amount of parathion will be desorbed and result in runoff . Although
soils treated with C-14 labeled parathion retained 27% of the radioactivity as unextractable bound
residue after 7 weeks, these residues can be slowly released by microbial action and taken up by
plants .
AQUATIC FATE: If released into water little parathion would be lost through volatilization.
Bioconcentration of parathion in aquatic systems will be moderate to low. Adsorption to sediment
and particulate matter in the water column will be very important. Many different processes
contribute to the degradation of parathion in the water and which of these processes contribute
the most will depend on the particular circumstances. Photolysis would be important in surface
waters. While direct photolysis has a half life of <1 day to 10 days, the presence of
photosensitizers, free radicals, hydrogen peroxide, or algae which are found in eutrophic waters
may accelerate degradation considerably. For example, 20% loss due to photodegradation
occurred in 18 hr and 2 hr in distilled water and Okefenokee Swamp water, respectively. While
hydrolysis would only be a major degradative pathway in the most alkaline enviromental waters at
high temperatures (half life 5 days at pH 9, 40 deg C), the presence of kaolinite and reduced soil
has a pronounced catalytic effect. Biodegradation generally occurs with a half life of several
weeks but in well acclimated water, complete degradation may occur in 2 weeks. When parathion
was applied to a pond, residues of parathion decreased from an initial concentration of 0.4-0.5
ppm to 0.01 ppm within 8 days . While a similar decline of residues occurred in a Utah pond in
7 days, the concentration in the bottom mud increased by a factor of 10 during this time .
Similarly, toxicity persisted in a cranberry bog for only 96 hr . In one slightly acidic lake
sediment, only 26% of added parathion degraded in 92 days while in another calcareous sediment
in a more polluted lake 28-39% degradation occurred within 54 days .
ATMOSPHERIC FATE: When parathion is sprayed on a field, or orchard it will exist primarily as
an aerosol in the source area and as a combination of vapor and aerosol downwind . The field
half life is 5 minutes for conversion to paraoxon in summer sunlight and considerably slower after
sunset . Being reasonably soluble in water (24 ppm ), it should be scavenged by rain.
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| Drinking Water Impact | DRINKING WATER: Not detected in samples of drinking water from 10-13 US cities
collected between Oct 1975 and Mar 1982 for Infant and Toddler Total Diet samples(1-5). Not
detected in beverages (which included drinking water) in the adult Total Diet Studies from Oct
1965 to Mar 1982(6-9). No parathion was detected in 54 monitored wells in selected California
communities(10). The wells selected for monitoring were primarily municipal supply systems near
agricultural areas(10). Contaminated drinking water well in CA contained 4.6 ppb(11).
Unspecified drinking water 30 parts per trillion(12). Not detected in Ottawa tap water (detection
limit <1 parts per trillion)(13).
SURFACE WATER: USGS survey of western streams in which 20 stations were analyzed for
parathion quarterly from Jan to June 1970 and monthly from July 1970 to Sept 1971: Gila River,
AZ 40 ppt (2 samples), Sacramento River at Verna CA, 40 parts per trillion and 160 parts per
trillion in 2 samples number of total samples not given . Non detectable in any water sample in
Little Miami river above and below municipal wastewater outfall, July-Sept 1984 . Survey of
surface waters in Germany 5-65 parts per trillion in 4 of 119 samples of unfiltered water from 28
locations and 0.15-0.4 parts per trillion in suspended solids in 3 of samples from 20 sites . Not
detected in any water or suspended particulate matter samples in Lake Superior, and Lake Huron,
including Georgian Bay at quantitation limits of 5 parts per trillion and 100 pg, respectively .
Highest concentration reported in surface water 0.4 ppb . Erie River Basin - not detected in the
>100 samples tested(6). Parathion was detected at 0.6% of 174 sampling stations of the nation's
rivers(7).
GROUNDWATER: Well water in Florida 125-185 ft depth 1 ppb - agricultural source of
contamination . Parathion was detected in a CA ground water aquifer at concn ranging from 4
to 6 ug/l .
EFFL: Ontario (original soil vegetable growing area) drainage ditch water from soil containing
0.6 and 2 ppm of parathion contained 2 and 4 parts per trillion, respectively . Detected in
lagoon water used to collect irrigation runoff from corn and sorghum fields in Kansas 6.2 ppb,
max .
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