Pesticides

1. General Information: The US EPA defines a pesticide to be any substance that is intended to prevent, destroy, repel, or mitigate any pest (Ecobichon, 1991). This includes insecticides, herbicides, fungicides, fumigants, algaecides and other substances. Herbicides which are pesticides used to kill vegetation are the most widely used, sampled for, and detected in ground water of all the pesticides (Barbash, 1996). Herbicides account for 75% of the pesticide use in U.S. agriculture (Wauchope et al., 1994).

2. Numerical Categories: See individual herbicides below.
   
   Most criteria do not take into account that fact that several pesticides, mixtures, or degraded products could be present. If there is no numerical criteria listed for a herbicide below then there is not nationally recommended water quality criteria.
   
   
3. Health Effects: See individual herbicides below.
   
   
4. Environmental Effects: See individual herbicides below.
   
   Pesticides are more frequently found and are at higher concentrations in streams or surface water than in ground water (USGS, 1998).
   
   
5. Sources:
   a. Nonpoint source: Pesticides can enter water bodies as the result of accidental drift during spray application, storage of pesticide containers where flooding or accidental releases of the compound occur, surface runoff from land or dry waterways where pesticides have been applied, and leaching through soil.
   
   b. Point source: Point sources include direct application of pesticides, release of pesticide-containing effluent from pesticide manufacturing plants, and spills during mixing, loading, or transport.
   
   

6. Mode of Transport: Pesticides are transported to aquatic systems via 1) direct fallout from spraying of nearby fields, 2) adsorption of the compound onto soil or organic particles that are then eroded and carried to the water body, 3) the compound is carried by overland and/or subsurface flow, and 4) dry or wet atmospheric deposition.
   
   The degree and ease of pesticide transport depends on five main factors (Wauchope et al., 1994):
   
   a. Application factors. Application factors include the time, frequency, site and amount of pesticide applied, the formulation type (granules, powder or liquid), and application method (surface, incorporated, or in-furrow).
   
   b. Pesticide persistence and mobility. The properties of the chemical compounds used in each pesticide determine the mobility and rate of degradation in the environment. Some pesticides form a strong bond to soil particles and are not mobile. Here, transportation only occurs when the soil is moved (eroded). Mobile pesticides do not bind strongly to soil particles and are more likely to leach. If a pesticide is too rapidly leached to the subsurface or carried in runoff to a water system, contamination of a water supply may occur.
   
   c. Soil composition. The tendency for pesticides to leach or be removed in surface runoff is also a function of the soil composition. Sandy soils drain rapidly and thus are susceptible to leaching problems. Clayey soil is less porous, so water will pool at the soil surface and run off instead of infiltrating. Soils with a high organic matter content will better adsorb pesticides.
   
   d. Topography of application site. The slope and drainage patterns of an area will affect the amount of pesticide removed from the site of application. Water will run off a highly sloped area more quickly than off a flatter area that allows ponding and infiltration. Additionally, the presence of a watercourse adjacent to the application site increases the probability of pesticide contamination.
   
   e. Climate. The climate of the area usually determines the crops grown and the types of pests present. The temperature and the intensity of the sun often determine the persistence of pesticide compounds. The frequency and duration of rainstorms may influence the degree to which pesticides are transported away from site of application. Pesticides will degrade faster under warm, moist conditions.
   
   Individual Herbicides (10 frequently used and detected in water):
   Atrazine,
   Metolachlor,
   Alachlor,
   2,4-D,
   Trifluralin,
   Glyphosate,
   Dicamba,
   Cyanazine,
   Simazine, and
   2,4,5-T.

Atrazine

Synonyms: Aatrex, Aktikon, Aktinit, Argezin, Atazinax, Atranex, Atrasine, Atratol A, Atred, Candex, Cekuzina, Crisatrina, Cyazin, Farmco atrazine, Fenamin,, Fenatrol, Geigy 30027, Gesaprim, Griffex, Hungazin, Inakor, Oleogesaprim, Primatol, Primaze, Radazin, Strazine, Triazine, Vectal, Weedex A, Wonuk, Zeazin, Zeazine (Montgomery,1997).

1. General Information: Atrazine is a member of the s-triazine herbicides. Weed growth is controlled by inhibition of photosynthetic electron transport and disruption of light reactions (Ecobichon, 1991).

Atrazine is one of the two most frequently used pesticides in agriculture in the United States and is the most commonly detected in ground and surface water due to its wide use, its ability to persist in soil and move in water (US EPA, 2001c).

Atrazine is produced as a colorless powder or white crystalline solid. Atrazine is a preemergence or postemergence herbicide used to control some broadleaf weeds and some annual grasses in crops of corn, soybeans, and sorghum; and on fallow land, rangeland, certain tropical plantations, evergreen nurseries, fruit crops, and lawns (Montgomery,1997).

2. Numerical Categories:

3. Health Effects: Exposure to high levels of atrazine may cause dermatitis, and severe irritation of the eyes, nose, and throat (Montgomery,1997). Consumption of high levels of atrazine may lead to tremors, organ weight changes, and liver and heart damage(Kubek et al., 1990). The US EPA has categorized atrazine as a possible human carcinogen, group C (AWWA, 1990).
   
   

4. Environmental Effects: Research has shown atrazine to have low toxicity to mammals, birds, and fishes. However, many aquatic organisms are susceptible at levels < 10 ppm. Freshwater clams suffered a 7/8 reduction in population with a dosage of 0.5 to 2.0 ppm atrazine. Aquatic microorganisms are more susceptible to atrazine than are soil microorganisms (Sassman et al., 1984).
   
   Atrazine has a slight tendency to bioaccumulate. Usually atrazine is rapidly transformed to non-toxic metabolites that are excreted.
   
   

5. Sources: Agricultural fields and treated landscapes.
   
   

6. Analytical Techniques: Atrazine (APHA, 1992; Thurman et al., 1990; Stoddard, 1990)
   

7. Environmental Fate/Mode of Transport: Atrazine is moderately persistent in soil (3 to 12 months) and moderately to highly mobile.Atrazine is stable at ambient pH and does not readily adsorb to soil or organic matter. It resists aqueous photolysis, and is not expected to volatilize rapidly (US EPA, 2001c). Atrazine is moderately soluble in water. Chemical hydrolysis and biodegradation are responsible for the majority of atrazine decomposition both in soil and water, occurring more rapidly in acidic or basic conditions (Extoxnet, 1996b).

Metolachlor

Synonyms: Bicep, CGA 24705, Codal, Cotoran multi, Dual, Dual 8E, Metelilachlor, Milocep, Ontrack 8E, Pennant 5G, Primagram, Primextra (Montgomery,1997).

1. General Information: Metolachlor is a member of the Chloroacetamide herbicides. These herbicides perturb protein synthesis (Ecobichon, 1991).
   
   Metolachlor is a colorless to tan, odorless liquid applied as an emulsion on crops. Metolachlor is a preemergence (applied before crop sprout) herbicide that controls most annual grasses and many weeds in beans, chickpeas, corn, cotton, milo, okra, peanuts, peas, potatoes, safflower, sorghum, soybeans, sunflowers, and some ornamental trees (Montgomery, 1997). Metolachlor is one of the top 5 pesticides detected in surface waters in the corn belt (US EPA, 1995b).
   
   

2. Numerical Categories:

3. Health Effects: Metolachlor is a possible carcinogen (group C) according to the US EPA. Contact with the compound may irritate eyes and skin (Montgomery,1997). Symptoms of intoxication include cramps, nausea, anemia, ataxia, methemoglobenemia, collapse, convulsions, sweating, and shock (APHA, 1992). Metolachlor is considerably more toxic when inhaled than when ingested (USDA, 1993).
   
   

4. Environmental Effects: Metolachlor is moderately toxic to both cold and warm water fish (USDA, 1993). It has no tendency to bioaccumulate (US EPA, 1995b).
   
   

5. Sources: Agricultural fields and treated landscapes.
   
   

6. Analytical Techniques: Metolachlor (APHA, 1992; Feng et al., 1990)

7. Environmental Fate/Mode of Transport: Metolachlor ranges from moderately to highly mobile depending on the type of soil. It can be persistent in soils, with a half-life of 7 to 292 days in the 6-12 inch soil layer (US EPA, 1995b). Adsorption to soil is facilitated by increases in clay and organic matter content. Metolachlor is highly persistent in water over a range of pH (half life >200 days in highly acidic water, 97 days in highly alkaline waters). Extensive leaching is seen especially in low organic matter soils (Extoxnet,1996c). Little metolachlor is thought to be lost to volatilization or photodegradation. The dominant degradation pathway is via microbial decomposition (Buttle, 1990). Metolachlor is completely degraded within 2 - 20 months (Connell et al., 1984).

Alachlor

Synonyms: Alanex, Alochlor, Bronco, Bullet, Cannon, 2-Chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide, 2-Chloro-2,3-diethyl-N-(methoxymethyl)acetanilide, CP 50144, Lariat, Lasso, LassoII, Lasso EC, Lazo, Metalachlor, Methachlor, Pillarzo (Montgomery,1997).

1. General Information: Alachlor is a member of the Chloroacetamide herbicides. These herbicides perturb protein synthesis (Ecobichon, 1991) and interfere with root elongation (USDA, 1993).
   
   Alachlor is a preemergence, early postemergence, or soil-incorporated herbicide used to control most grasses and many broadleaf weeds in crops of beans, corn, cotton, milo, peanuts, peas, soybeans, sunflower, and some ornamental trees. Alachlor is an odorless, cream-colored solid or crystals (Montgomery,1997).
   
   Alachlor is a Restricted Use Pesticide (RUP) due to possible groundwater contamination. It can only be used by or with the supervision of a certified pesticide applicator (US EPA, 1998).
   
   

2. Numerical Categories:

3. Health Effects: Alachlor is a likely carcinogen at high doses and not a likely carcinogen at low doses (US EPA, 1998). Alachlor has a low acute oral toxicity. Studies indicate chronic effects including hepatotoxicity and eye degeneration with secondary cataract formation. Studies on rodents indicate tumor formation in lungs, stomach, thyroid, and nasal passages (AWWA, 1990).
   
   

4. Environmental Effects: Alachlor is slightly to nontoxic to birds and mammals. For freshwater fish on a chronic basis alachlor is highly to moderately toxic but only slightly to moderately toxic on an acute basis. It is moderately toxic to saltwater fish, and highly toxic to aquatic plants (US EPA, 1998). Alachlor does not have a tendency to bioaccumulate in aquatic organisms(Extoxnet, 1996d).
   
   

5. Sources: Agricultural fields and treated landscapes.
   
   

6. Analytical Techniques: Alachlor (APHA, 1992; USDA, 1993)

7. Environmental Fate/Mode of Transport: Alachlor has moderate mobility in sands and silty soils and is expected to leach to ground water (Kubek et al., 1990).
   
   Alachlor does not readily adsorb to soils and thus tends to be highly mobile. It is moderately persistent with a half-life of 2-3 weeks, broken down principally by aerobic soil microbial activity. Alachlor is also highly mobile and moderately persistent in water(US EPA,1998).

2,4-D

Synonyms: Agrotect, Agroxone, Amidox, Amoxone, Aqua-kleen, Brush-rhap, B-Selektonon, Chipco Turf herbicide 'D', Chloroxone, Crop Rider, Crotolin, D 50, Dacamine, Ded-weed, Desormone, Envert 171, Esteron, Farmco, Fernesta, Ferxone, Hedonal, Herbidal, Ipaner, Lawn-keep, Macondray, Miracle, Monosan, Moxone, Pennamine, Phenox, Pielik, Planotox, Plantguard, Tributon, Trinoxol, U 46, Vergemaster, Verton D, Visko-rhap, Weedar, Weddatul, Weed-b-gone, Weedeez, Weedone, Weedtrol (Montgomery, 1997).

1. General Information: 2,4-D is a member of the Chlorophenoxyacetic acid herbicides. By-products of 2,4-D include salts, amines, and esters. These mobile herbicides chemically stimulate plant growth hormones (auxin), causing uncontrolled cell proliferation (Connell et al., 1984). Because these compounds contain chlorine, they pose a risk for dioxin formation (Connell et al., 1984).
   
   2,4-D comes in emulsion form, in aqueous solution, and crystals (Extoxnet, 1996e). The crystals are prismatic, white to pale yellow in color, and have a phenolic-like odor. 2,4-D is a postemergence herbicide that controls annual and perennial broadleaf weeds in fruits, vegetables, turfs, and ornamentals (Montgomery, 1997). 2,4-D also serves as a plant growth regulator and may be applied to crops to induce rooting and blossom set, to control ripening of bananas and citrus fruits, and to prolong fruit life on the tree (Sassman et al., 1984).
   
   
2. Numerical Categories:

3. Health Effects: 2,4-D Exposure occurs by contact with skin, inhalation, or ingestion of contaminated food or water. Dermal absorption poses the greatest risk (Kubek et al., 1990). Exposure produces a weak stupor, hyporflexia, muscle twitch, convulsions, and dermatitis (Montgomery, 1997). Prolonged exposure may reduce nerve conduction (Kubek et al., 1990). There is inadequate information regarding 2,4-D as a carcinogen; therefore, it is unclassified according to the US EPA.
   
   
4. Environmental Effects: Most formulations of 2,4-D are mildly toxic to animals and birds. Based on acute and chronic studies, 2,4-D has caused gastrointestinal disorders, weight loss, muscle weakness, and a lack of coordination (Sassman et al., 1984). 2,4-D is teratogenic at high doses (Extoxnet, 1996e). 2,4-D is readily excreted in the urine of animals and does not bioaccumulate (Sassman et al., 1984; Kubek et al., 1990). 2-4D may be toxic to aquatic organisms, depending on the species of the test organism, the formulation of the chemical, and the surface water system parameters such as pH, temperature, and water chemistry. Most ester formulations of 2,4-D are more toxic to fishes and aquatic invertebrates than the salt and acid formulations. At low level exposure fishes may suffer sublethal effects such as impaired swimming and physiological stress responses (Sassman et al., 1984).
   
   
5. Sources: Agricultural fields and treated landscapes.
   
   
6. Analytical Techniques: 2,4-D (APHA, 1992; Stoddard, 1990)

7. Environmental Fate/Mode of Transport: 2,4-D is a highly mobile compound that may readily disperse (Gu et al., 1992). Biodegradation is the primary route of loss from water and soil, with additional losses from photodegradation. The final product after degradation is CO2. 2,4-D is completely degraded within 1 - 5 months by dealkylation, ring hydroxylation, or -hydroxylation (Connell et al., 1984).

a. Air: 2,4-D in air is in the form of volatile esters, with greatest concentrations occurring after spraying. Airborne 2,4-D will photodegrade either directly or by reacting with hydroxyl radicals (Kubek et al., 1990).

b. Water: 2,4-D will quickly be broken down in surface water by microbial degradation (Sassman et al., 1984). The rate of decomposition increases as nutrient, sediment and organic carbon levels increase under aerobic conditions (half-life of 1 to several weeks) (Extoxnet, 1996e). Rapid degradation also occurs in the mud and sediment of surface water systems. 2,4-D in water will not readily sorb to sediment, will not vaporize, and will not hydrolyze (Kubek et al., 1990).

c. Soil: 2,4-D has low persistence in soil with a half-life of less than 7 days (Extoxnet, 1996e). The mineral composition and texture of soil determines the toxicity of 2,4-D. Because of rapid microbial degradation, lower toxicity occurs in aerobic soil with high organic matter, pH, and temperature. 2,4-D will not readily sorb to soil. Little evaporation or hydrolysis is expected. Some photodegradation may occur on the soil surface. 2,4-D has been detected in ground and surface water in spite of its short half-life (Extoxnet, 1996e).

Trifluralin

Synonyms: Agriflan 24, Agreflan, Crisalin, Digerman, Elancolan, Lilly 36352, Nitran, Olitref, Trefanocide, Treficon, Treflan, Trifluoraline, Triflurex, Trikepin, Trim (Montgomery, 1997).

1. General Information: Trifluralin is a member of the Dinitroaniline herbicides, which inhibit cell and nuclear division (Ecobichon, 1991). It inhibits formation of microtubule, via enzyme inhibition, causing strange growth patterns. The enzymatic process that is disrupted in plants is different enough from that of humans and animals that the latter experience no effects from the chemicals (Connell et al., 1984).
   
   Trifluralin is produced as yellow to orange crystals (Montgomery,1997). It can be obtained as a liquid, emulsifiable concentrate, granules, flowable concentrate, soluble concentrate/liquid, soluble concentrate/solid, and water dispersible granules (US EPA, 1996).
   
   Trifluralin is a selective preemergence herbicide for controlling many annual grasses and broadleaf weeds in a variety of tree fruit, nuts, vegetables and grain crops such as soybeans, alfalfa, and cotton. It should be mechanically incorporated into the soil within 24 hours of application (Extoxnet, 1996a). Trifluralin is also registered for residential site use (US EPA, 1996).
   
   
2. Numerical Categories:

3. Health Effects: Irritates eyes and may cause skin sensation in some individuals (Montgomery, 1997). Symptoms of ingestion include abdominal cramps, nausea, diarrhea, headache, and respiratory difficulty (APHA, 1992). Trifluralin is a group C, possible carcinogen according to the US EPA.
   
   
4. Environmental Effects: On an acute basis trifluralin is basically non-toxic to birds and mammals. For fish and aquatic invertebrates trifluralin is considered moderately to highly toxic. Toxicity depends on temperature, pH, and life stage or size of the organism (Extoxnet, 1996a). It has a moderate propensity to bioaccumulate (US EPA, 1996).
   
   
5. Sources: Agricultural fields and treated landscapes.
   
   
6. Analytical Techniques: Trifluralin (APHA, 1992; Stoddard, 1990)

7. Environmental Fate/Mode of Transport: Trifluralin is moderately to highly persistent according to soil conditions. It is prone to decomposition by soil microorganisms. Reported half lives range from 45-60 days to 6-8 months. Soil adsorption increases with increasing organic matter or clay content, and the adsorbed herbicide is ineffective. Trifluralin on the soil surface may volatize or decompose by ultraviolet light. It is nearly insoluble in water but adsorbs to soil sediments and particulates in the water (Extoxnet, 1996a).

Glyphosate

Synonyms: Roundup, Rodeo (Montgomery, 1997).

1. General Information: Glyphosate is a member of the Organophosphate herbicides. These are non-nitrogen based herbicides that inhibit synthesis of essential amino acids and promote destruction of photosynthetic pigments in foliage (Connell et al., 1984; Sassman et al., 1984)
   
   Glyphosate is a colorless to white, odorless crystal or powdery solid that is applied from the air or ground (Sassman et al., 1984). Glyphosate is a non-selective, postemergence, broad spectrum herbicide used to control annual and perennial grasses, sedges, broadleaf, and emergent aquatic weeds (Montgomery, 1997). It is used on non-cropland in addition to use on a large variety of crops (Extoxnet, 1996f). Glyphosate is among the most abundantly used pesticides by volume (US EPA, 1993d).
   
   
2. Numerical Categories:

3. Health Effects: When ingested, glyphosate is eliminated in the feces (Kubek et al., 1990). Some formulations may cause skin or eye irritation but for the majority, glyphosate is not irritating to skin (Extoxnet, 1996f). Glyphosate is probably not a carcinogen, group E (US EPA, 1993d).
   
   
4. Environmental Effects: Generally not toxic to most organisms, including birds, fish, and mammals. Invertebrates and microorganisms exhibit a wide range of tolerances. Soil microflora is generally not affected. Because glyphosate is not lipophilic, it will not bioaccumulate. Any residues in the organism will be rapidly excreted (Sassman et al., 1984). There is a possibility for toxicity when glyphosate is applied to aquatic environments (US EPA, 1993d).
   
   
5. Sources: Agricultural fields and treated landscapes.
   
   
6. Analytical Techniques: Glyphosate (APHA, 1992; Stoddard, 1990)

7. Environmental Fate/Mode of Transport: Glyphosate is moderately persistent in soil with an average half-life of 47 days. It strongly adsorbs to soil and is highly soluble in water (Extoxnet, 1996f). Aerobic and anaerobic microbial decomposition are the primary processes by which glyphosate is removed from the soil and water. Photodecomposition plays a minor role in removal (Kubek et al., 1990). The half life in water is slower because there are fewer microbes present. Glyphosate in water will rapidly adsorb to organic matter and sediment in the water column. Surface water contamination is possible through erosion (adsorbed to sediment suspended in water) and when applied to aquatic environments (US EPA, 1993d).

Dicamba

Synonyms: Banex, Banvel, Banvel CST, Banvel D, Brush Buster,Dianate, Dicambe, Velsicol compound 'R,' (Montgomery, 1997).

1. General Information: Dicamba is a member of the Benzoic acid and analogue herbicides. These mimic plant growth-regulating hormones (auxin) that interfere with plants' normal functions (Ecobichon, 1991). Dicamba crystals are odorless and colorless to pale buff.
   
   Dicamba is a preemergence and postemergence herbicide that controls both annual and perennial broadleaf weeds, chickweed, mayweed, and bindweed in cereals and other related crops (Montgomery, 1997). Dicamba is applied to the leaves or to the soil (Extoxnet, 1996g).
   
   
2. Numerical Categories:

3. Health Effects: Dicamba is slightly toxic by ingestion, inhalation, or through dermal exposure. Symptoms of poisoning include: loss of appetite, vomiting, muscle weakness, slowed heart rate, shortness of breath, central nervous system effects, incontinence, or cyanosis (Extoxnet, 1996g). Dicamba is a group D, unclassified carcinogen according to the US EPA.
   
   
4. Environmental Effects: Dicamba is generally not toxic to non-target organisms. Dicamba will not bioaccumulate. If ingested, dicamba is rapidly metabolized and excreted in the urine (Sassman et al., 1984).
   
   
5. Sources: Agricultural fields and treated landscapes.
   
   
6. Analytical Techniques: Dicamba (APHA, 1992)

7. Environmental Fate/ Mode of Transport: Dicamba is moderately persistent in soil with a half-life of 1-4 weeks. It does not bind to soil; is highly soluble in water. Thus dicamba is mobile in soil with the possibility of ground water contamination (Extoxnet, 1996g). Losses may occur after application via several pathways. The primary pathway is microbial decomposition. Dicamba will react with alkalies, amines, and alkali metals to form water-soluble salts (Montgomery, 1997), which most likely will rapidly move into the soil, but may also be leached to surface waters (Sassman et al., 1984). Small losses may occur because dicamba is slowly photodegradable in ultraviolet light. Volatilization is not significant (Extoxnet, 1996g).

Cyanazine

Cyanazine registered products were voluntarily cancelled effective 12/31/99. Although no product is available after this date, cyanazine may still be detected in ground and surface water.

Synonyms: Bladex, Bladex 90DF, Bladex 4L, Bladex 80WP, 2-((4-Chloro-6-(ethyl-amino)1,3,5-triazin-2-yl)amino)-2- methylpropanenitrile, DW 3418, Fortrol, Payze, SD 15418, WL 19805 (Montgomery, 1997).

1. General Information: Cyanazine is a member of the s-triazine herbicides. Cyanazine crystals are colorless to white. Formulations include a wettable powder, granules, and a suspension concentrate. Cyanazine is an herbicide used for control of annual grasses and broadleaf weeds in cereals, cotton, maize, onions, peanuts, peas, potatoes, soybeans, sugar cane, and wheat fallow (Montgomery, 1993).
   
   
2. Numerical Categories: Designated Use Limit (APHA, 19921) Human Consumption 0.046 mg/l

3. Health Effects: Cyanazine is moderately toxic to humans (USDA, 1993). It is a US EPA possible carcinogen, group C.
   
   
4. Environmental Effects: Cyanazine is slightly toxic to birds, fishes, and aquatic invertebrates (USDA, 1993). Cyanazine has a tendency to bioaccumulate (Extoxnet, 1996h).
   
   
5. Sources: Agricultural fields and treated landscapes.
   
   
6. Analytical Techniques: Cyanazine (APHA, 1992; Thurman et al., 1990; Stoddard, 1990)

7. Environmental Fate/Mode of Transport: Cyanazine is degraded by hydrolization to carboxylic acid. Laboratory tests show a greater hydrolysis rate under high temperatures and low pH. Accordingly, tests show the half life of cyanazine to be longer in a alkaline soil (pH> 7.5) than in an acidic soil (pH< 5.5). Cyanazine in sandy loam soils generally degrades more quickly (12 - 15 day half life) than in a silty or clayey loam soil (20 to 25 days). Cyanazine may contaminate ground water supplies (USDA, 1993).

Simazine

Synonyms: A 2079, Aktinit S, Aquazine, Aquazine 80W, Batazina, Bitemol, Bitemol S 50, Caliper, Caliper 90, CAT, CDT, Cekusan, Cekuzina-S, Framed, G 27 692, Geigy 27692, Gesaran, Gesatop, Gesatop 50, H 1803, Herbazin, Herbazin 50, Herbex, Herboxy, Hungazin DT, Premazine, Primatol S, Princep, Princep 4G or 4L or 80W, Printop, Radocon, Radokor, Simadex, Simanex, Simazin, Simazine 80W, Sim-trol, Symazine, Tafazine, Taphazine, Triazine, Weedex, Zeapur (Montgomery, 1997).

1. General Information: Simazine is a member of the s-triazine herbicides. Simazine is a colorless to white solid. Formulations include an emulsifiable concentrate, granules, suspension concentrate, water-dispersible granules, and wettable powder. Simazine is a selective preemergence systemic herbicide used for control of annual grasses and broadleaf weeds in vegetable crops and deep-rooted fruit trees (Montgomery, 1997). Simazine is also used as a non-selective herbicide for weed control in industrial areas (USDA, 1993).
   
   
2. Numerical Categories: Designated Use Limit (Kubek et al., 1990) Human Consumption 0.004 mg/l

3. Health Effects: Simazine is very toxic if inhaled, moderately toxic if ingested, and slightly toxic upon dermal exposure (USDA, 1993). When dermally exposed, simazine may cause mild to acute dermatitis, as well as irritation to eyes, skin, and mucous membranes (Montgomery, 1997). Toxicity symptoms include impairment of walking, onset of tremors, convulsions, paralysis, cyanosis, slowed respiration, miosis, gastrointestinal pain, diarrhea, and impaired adrenal function (USDA, 1993). It is a group C, possible carcinogen according to the US EPA.
   
   
4. Environmental Effects: Simazine exhibits low toxicity to aquatic life (USDA, 1993). Sheep and cattle that use a simazine-contaminated water supply for drinking are susceptible to toxic effects. Symptoms exhibited by affected sheep include decreased feeding, increased water consumption, decreased coordination, onset of tremors, and weakness in hindquarters (USDA, 1993).
   
   
5. Sources: Agricultural fields and treated landscapes.
   
   
6. Analytical Techniques: Simazine (APHA, 1992; Thurman et al., 1990; Stoddard, 1990)

7. Environmental Fate/Mode of Transport: Simazine has a low water solubility and will adsorb to clay and mucky soils. Simazine has an average half-life of 60 days in soil, and may have residual activity up to 1 year after application in a high pH environment. Simazine has been detected in ground water supplies (Extoxnet, 1996i).
   
   The majority of Simazine is biodegraded, although a small amount may be lost to photodegradation (USDA, 1993). Simazine is also degraded by plant metabolism and dealkylation (Kubek et al., 1990).

2,4,5-T

2,4,5-T is a cancelled pesticide, and no longer registered with the U.S. EPA. Although no product is available, 2,4,5-T may still be detected in ground and surface water.

Synonyms: Amine 2,4,5-T, BCF-bushkiller, Brushoff, Brush-rhap, Brushtox, Dacamine 4 T, Debroussaillant concentre, Decamine, Ded-weed brush killer, Dinoxil, Envert-T, Estercide T-2, Esteron, Esterone, Esteron Brush Killer, Farmco fence rider, Fence Rider, Forron, Forst U 46, Fortex, Fruitone A, Inverton 245, Line Rider, Phortox, RCRA waste number U232, Reddon, Reddox, Spontox, Super D weedone, Tippon, Tormona, Transamine, Tributon, Trinoxol, Trioxon, Trioxone, U 46, Veon, Verton, Visko-rhap low volatile ester, Weddar, Weedone, Weedone 2,4,5-T (Montgomery, 1997).

1. General Information: 2,4,5-T is a member of the chlorinated phenoxyalkanoic acid herbicides. These mobile herbicides chemically stimulate plant growth hormones (auxin), causing uncontrolled cell proliferation (Connell et al., 1984). Because these compounds contain chlorine, they pose a risk for dioxin formation (see dioxin section) (Connell et al., 1984).
   
   2,4,5-T crystals have no odor and are white to pale brown. Formulations include an emulsifiable concentrate and a soluble concentrate. 2,4,5-T is an herbicide used as a defoliant and to control undesirable brush and woody plants (Montgomery, 1997).
   
   
2. Numerical Categories: Designated Use Limit (APHA, 1992) Human Consumption 0.105 mg/l

3. Health Effects: May cause irritation to skin, eyes, nose, and throat (Montgomery, 1997). Other symptoms include chloracne, nausea, headache, fatigue, and muscular pain (APHA, 1992).
   
   
4. Environmental Effects: Ingestion of 2,4,5-T may lead to teratogenic effects in mammals.
   
   
5. Sources: Agricultural fields and treated landscapes.
   
   
6. Analytical Techniques: 2,4,5-T (APHA, 1992)

7. Environmental Fate/ Mode of Transport: 2,4,5-T is degraded primarily by hydrolysis (in soil) and photolysis (in water). The approximate half life in soil is 14 days. Degradation in water is accelerated if fulvic acid is present.

NCSU Water Quality Group

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