APPENDIX 3
Fact sheets on pesticides

Aldrin

Common formulation

C₁₂H₈Cl₆

CAS registry number

309-00-2

Use

As an insecticide against soil and cotton insects,
turf pests, white grubs and corn root worms.

ALDRIN IN THE ENVIRONMENT

• Mobility

Aldrin is thought to adsorb moderately to soil.

• Degradation

Aldrin residues in soil and plants volatilize from soil surfaces or are slowly transformed into dieldrin in soil. Biodegradation is thought to be slow, and aldrin is thought not to leach. Aldrin is classified as moderately persistent, meaning its half-life in soil ranges from 20–100 days. Photo-oxidization of aldrin is thought to be significant. Photolysis has been observed in water, although the absorption characteristics of aldrin indicate that it should not directly photolyse in the environment to any significant extent.

• Degradation products

The main product of aldrin degradation is dieldrin.

• Volatilization/evaporation

Aldrin residues in water and soil volatilize from the surface. Vapourphase aldrin residues in the atmosphere are thought to react with photochemically generated hydroxyl radicals, with an estimated halflife of 35 minutes.

• Bioaccumulation

Bioaccumulation of aldrin is significant.

• Phytotoxicity

Aldrin is phytotoxic to tomatoes and cucumbers only at application rates many times greater than those recommended. Cabbage is the crop most sensitive to aldrin.

* Most information in Appendix 3 was obtained from the following sources: U.S. National Library of Medicine, Hazardous Substances Databank, 1995; Oregon State University, Extension Toxicology Network (database), 1995; and British Crop Protection Council. The Pesticide Manual, various editions. Other sources can be found in Appendix 9.

PROPERTIES

Aldrin ranges in colour from colourless to dark brown and is a liquid or solid. It is resistant to organic and inorganic bases and to the action of hydrated metal chlorides and mild acids. It is stable up to 200°C and in the pH range 4–8.

TABLE A

Parameters

Atrazine

Active ingredient

Trazine

Common formulation

C₈H₁₄CIN₅

CAS registry number

1912–24–9

Use

As an herbicide to control annual weeds in asparagus fields,
forests, grasslands, grass, crops, maize, etc.

ATRAZINE IN THE ENVIRONMENT

• Mobility

Atrazine is thought to maintain high to medium mobility in soil, and should not adsorb readily to sediment. Atrazine adsorbs more readily to muck or clay soils than to soils of a low clay or organic matter content.

• Degradation

Most triazines are very stable in soil and dissipate slowly through degradation by soil microorganisms. Although the half-life of 50 days was reported for laboratory conditions, in practice atrazine persisted in soil for more than four months.

The rate of chemical degradation of atrazine depends strongly on environmental acidity and the presence of catalytic substances. Atrazine may hydrolyse fairly rapidly in either acidic or alkaline environments, yet is strongly resistant to hydrolysis in neutral environments (pH 7). In a neutral environment and at 25°C the half-life of atrazine was calculated to be 1 800 years. In extreme environments, atrazine was completely hydrolysed within three to four days. Hydrolysis in alkaline environments proceeds twice as rapidly as it does in acidic environments.

The rate of hydrolysis is increased drastically by the addition of humic materials. The acidic functional groups of humic materials (in particular hydrogen ions) work as catalytic agents. For example, the half-life of atrazine at pH 4 was 244 days without an additive and 1.73 days in the presence of humic acid.

• Degradation products

The major product of atrazine degradation is 2-chloro-4 amino-6-isopropyloamino-s-trazine.

• Volatilization/evaporation

Atrazine is thought not to volatilize.

• Bioaccumulation

On the base of log K_ow atrazine is thought to accumulate moderately in organisms. No bioconcentration was observed after exposing fish to various concentrations of atrazine. None of the fish species bioconcentrates atrazine from water (residue concentration below detectable limits).

• Phytotoxicity

Experiments with applying atrazine to susceptible crops have demonstrated that residual concentrations of less than 0.7 mg/kg in plants do not cause serious damage to the crop.

PROPERTIES

Atrazine is a colourless powder. In its original packing, it is stable for several years, with a slight sensitivity to natural light. It must be kept away from heat, flames and sparks. It is unstable in an acidic or alkaline environment. Spillages can be removed using 10 v/w percent of a NaOH solution.

TABLE B

Parameters

Captafol

Common formulation

C₁₀H₉C₁₄NO₂S

CAS registry number

2425–06–1

Use

As a broad-spectrum protective contact fungicide. It is effective for the control of fungal diseases of plants (except powdery mildews) and is widely used to control foliage and fruit diseases on apples, citrus fruits, potatoes, coffee, etc.
It is also used to reduce losses from wood rot fungi in logs and wood products.

CAPTAFOL IN THE ENVIRONMENT

• Mobility

The values of the adsorption coefficient indicate that captafol is slightly mobile in most soils.

• Degradation

Both biodegradation and hydrolysis may be the major processes causing the loss of captafol from most soils. The experimental estimated half-life of captafol in three soils was estimated to be in the range of 23–55 days. Half-lives of less than three, five and eight days have been reported for nonsterile organic, sandy and clay loam soils, respectively. Captafol does not leach from alkaline soils. The estimated half-life of captafol in a river is 0.3 of a day, primarily due to biodegradation.

• Degradation products

No data available.

• Volatilization/evaporation

Because of captafol's low vapour pressure, its volatilization from dry and moist soil should be negligible.

• Bioaccumulation

The bioaccumulation of captafol in aquatic organisms is not important.

• Phytotoxicity

The half-life of captafol sprayed on most crops was less than five days. Residues were below the tolerance limits at the time of harvest. The roots and shoots of plants absorb Captafol and its metabolites. Captafol is also translocated in plant tissue as a result of seed treatment, soil treatment and foliar application. Grapes, apples and citrus fruits have been injured by phytotoxicity under certain weather conditions. Roses have shown injury at high rates of application.

PROPERTIES

Captafol forms colourless to yellow crystals. It hydrolyses in aqueous emulsions or suspensions. It hydrolyses rapidly in acidic and alkaline media.

TABLE C

Parameters

Carbaryl

Common formulation

C₁₂H₁₁NO₂

CAS registry number

63–25–2

Use

As an insecticide to control insects on citrus fruits, fruit, cotton, forests, lawns, shade trees and other crops.

CARBARYL IN THE ENVIRONMENT

• Mobility

Based on its moderate soil sorption coefficient, carbaryl exhibits moderate mobility.

• Degradation

Carbaryl has low persistence in soil. Its degradation is mostly due to sunlight and bacterial action. The rate of photolysis at the soil surface depends on the soil water content. Carbaryl has a half-life of 7–14 days in sandy loam soil, and 14–28 days in clay loam soil. It hydrolyses relatively rapidly in moist alkaline soil, but only slowly in acidic soil.

Release to soil results in rapid hydrolysis at pH values of seven and above (half-life 10.5 days, 1.8 days and 2.5 hours at a pH of seven, eight and nine, respectively). In surface water, carbaryl may degrade due to bacteria and through hydrolysis. The half-life varies greatly depending on water acidity. Hydrolysis in acidic water is slow (halflife 1 500 days at pH 5).

• Degradation products

The major degradation products are 3-hydroxycarbofuran. 3-ketocarbofuran and carbofuran phenol.

• Volatilization/evaporation

Evaporation of the compound is very slow.

• Bioaccumulation

Bioaccumulation is thought to be not significant.

• Phytotoxicity

Degradation of carbaryl in crops occurs by hydrolysis inside the plants. It has a short residual life of less than two weeks.

PROPERTIES

Carbaryl forms colourless to light tan crystals. It is stable in the presence of heat, light and acids. It is subject to hydrolysis.

TABLE D

Parameters

Carbofuran

Common formulation

C₁₂H₁₅NO₃

CAS registry number

1563–66–2

Use

As a broad-spectrum carbamate pesticide. It is used against the soil and foliar pests of fields, fruits, vegetables and forest crops.

CARBOFURAN IN THE ENVIRONMENT

• Mobility

Carbofuran has high to very high mobility in soil.

• Degradation

There are reported half-lives for carbofuran disappearance from soil of 2–86 days for flooded soils and 26–110 days for field soil. Chemical hydrolysis and microbial degradation appear to be important degradation processes for this compound in both soil and aquatic systems. Chemical hydrolysis of carbofuran is thought to occur more rapidly in alkaline than in acidic or neutral environments. Carbofuran exhibits enhanced biodegradation in soils previously treated with this pesticide. Direct photolysis and photo-oxidation (via hydroxyl radicals) may contribute to carbofuran's removal from natural water. Half-lives for the degradation of carbofuran in river, lake, and sea water samples that were irradiated with sunlight were approximately 2, 6 and 12 hours, respectively. The rate of degradation of carbofuran increases as the application rate decreases, the clay and organic matter content of the soil decreases, the pH increases, and the moisture content of the soil increases.

• Degradation products

The major metabolites of carbofuran degradation in soil are 3-hydroxycarbofuran, 3-ketocarbofuran and carbofuran phenol.

• Volatilization/evaporation

Volatilization from soil surfaces is thought to be not significant. If released into the atmosphere, carbofuran should exist in both the vapour and particulate phases in the ambient atmosphere based on a measured vapour pressure of 4.85 × 10-6 mm Hg at 19°C. Vapourphase carbofuran is degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals, with a half-life of about 13 hours. Particulate phase carbofuran may be physically removed from the air by wet and dry deposition. Direct photolysis may be an important removal process for carbofuran in the atmosphere.

• Bioaccumulation

Bioaccumulation of carbofuran in aquatic organisms is not important.

• Phytotoxicity

The half-life of carbofuran on crops is about four days when applied to roots, and longer than four days if applied to the leaves.

PROPERTIES

Carbofuran is a crystalline solid. It is stable under neutral or acidic conditions, but unstable in alkaline media.

TABLE E

Parameters

Chlordane

Common formulation

C₁₀H₆Cl₈

CAS registry number

57-74-9

Use

As a persistent insecticide for underground termite control, for homes, gardens and for the control of corn, citrus fruits, vegetables and other crops.

CHLORDANE IN THE ENVIRONMENT

• Mobility

Based on field tests, chlordane is thought to be generally immobile or only slightly mobile.

• Degradation

Chlordane is highly persistent in soils, with a half-life of about four years. Several studies have found chlordane residues in excess of 10 percent of the initially applied amount ten years or more after application. Sunlight may break down a small amount of the chlordane exposed to light. Chlordane does not chemically degrade and is not subject to biodegradation in soils. Chlordane molecules usually remain adsorbed to clay particles or to soil organic matter in the topsoil layers and slowly volatilize into the atmosphere. Extremely low levels of chlordane, however (0.01 to 0.001 μg/L), have been detected in both ground and surface waters in areas where chlordane was heavily used. Sandy soils allow the passage of chlordane to groundwater.

Chlordane does not degrade rapidly in water. It can exit aquatic systems by adsorbing to sediments or by volatilization.

• Degradation products

The photoisomers of chlordane appear to occur under natural conditions. All of these photoisomers are of special significance because to certain animals they are much more toxic than chlordane. Photo-cis-chlordane, which is more biodegradable than cis-chlordane, showed higher bioaccumulation values and therefore may have more significant effects on food chains.

• Volatilization/evaporation

Evaporation is the major route of removal from soils. The volatilization half-life of chlordane in lakes and ponds is estimated to be less than ten days. However, adsorption to sediment significantly attenuates the importance of volatilization. Chlordane reacts in the vapour phase with photochemically produced hydroxyl radicals at an estimated half-life rate of six hours, suggesting that this reaction is the dominant chemical removal process.

• Bioaccumulation

Chlordane is thought to have a high accumulation in aquatic organisms.

• Phytotoxicity

No data are currently available.

PROPERTIES

Technical chlordane is a mixture of at least 23 different components, including chlordane isomers. It is a viscous, colourless or amber liquid. It decomposes in weak alkalis.

TABLE F

Parameters

Chlordimeform

Common formulation

C₁₀H₁₃CIN₂

CAS registry number

6164-98-3

Use

As an acaricide and insecticide. It is also effective in controlling lepidoptera and is used to control eggs and larvae on cotton.

CHLORDIMEFORM IN THE ENVIRONMENT

• Mobility

An estimated K_OC value of 890 suggests that chlordimeform has moderate mobility in soil.

• Degradation

Chlordimeform biodegrades. Biodegradation under anaerobic conditions is slow.

The residue of chlordimeform decreased rapidly after soluble powder or emulsifiable concentrate formulations of the pesticide were applied, but 10 percent remained detectable after 500 days.

• Degradation products

The major degradation products are N-dimethylchlordimeform, chloro-o-formotoluidide and chloro-acetotoluide.

• Volatilization/evaporation

Based on a measured vapour pressure of 3.6 × 10-4 mm Hg at 25°C, volatilization from soil is not expected. Chlordimeform in vapour phase is degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals with a half-life of about 0.2 of a day.

• Bioaccumulation

The bioaccumulation in aquatic organisms should be moderate based on an estimated value of K_ow = 0.11.

• Phytotoxicity

Not applicable.

PROPERTIES

Chlordimeform forms colourless crystals. It hydrolyses in neutral and acidic aquatic media.

TABLE G

Parameters

Chlorfenvinphos (Birlane)

Common formulation

C₁₂H₁₄Cl₃O₄P

CAS registry number

470-90-6

Use

As an insecticide to control ticks, files and mites on cattle. Also used to control root files and rootworms and as a foliage insecticide to control the Colorado beetle on potatoes and leafhoppers on rice.

CHLORFENVINPHOS IN THE ENVIRONMENT

• Mobility

According to a suggested classification, the log K_oc value of 2.47 indicates that chlorfenvinphos has medium mobility in soil.

• Degradation

If released into soil or water, chlorfenvinphos degrades through biodegradation. The importance of microbial degradation has been demonstrated by various persistence studies that compared degradation rates in sterile versus non-sterile soil. In these studies, the degradation of chlorfenvinphos was much faster in non-sterile than in sterile soil. In one 90-day field study, chlorfenvinphos did not leach in a sandy loam soil. Typical soil half-lives range roughly from 10 to 45 days.

The aqueous hydrolysis half-life of chlorfenvinphos has been determined to be four days at pH 6. The rate of hydrolysis depends on the acidity of the environment. The hydrolysis half-life at pH 6–8 and at 20°C is approximately 388–483 days.

• Degradation products

The degradation products of chlorfenvinphos are dichlorophenacyl chloride, dichloroacetophenone, alpha-chromethyl-2.4-dichlorobenzyl alcohol, 2-hydroxy-4-chlorbenzoic acid and 2.4-dihydrobenzoic acid.

• Volatilization/evaporation

Based on vapour pressure and water solubility, chlorfenvinphos is essentially non-volatile in water. If released into the atmosphere, it degrades rapidly in the vapour phase by reaction with photochemically produced hydroxyl radicals (half-life about seven hours). Particulate phase chlorfenvinphos and aerosols released into the air during spray applications of chlorfenvinphos insecticides are removed from the air physically by dry and wet deposition.

• Bioaccumulation

Chlorfenvinphos is thought to accumulate moderately in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Chlorfenvinphos is a colourless liquid. It is unstable in alkali at 20°C (half-life 1.28 at pH 13). It slowly hydrolyses in water or acid.

TABLE H

Parameters

Chlorobenzilate

Common formulation

C₁₆H₁₄Cl₂O₃

CAS registry number

510-15-6

Use

To control mites on citrus crops and in beehives. It has a narrow insecticidal use, killing only ticks and mites.

CHLOROBENZILATE IN THE ENVIRONMENT

• Mobility

Since chlorobenzilate is practically insoluble in water and adsorbs strongly to soil particles in the upper soil layers, it is thought to exhibit low mobility in soils, and is therefore unlikely to leach into groundwater.

• Degradation

Chlorobenzilate has a low persistence in soils. Its half-life in fine sandy soils is 10–35 days after application of 0.5–1.0 ppm. The removal is probably due to microbial degradation. Following a fiveday application of chlorobenzilate to several different citrus groves employing various tillage treatments, the pesticide was not found in subsurface drainage waters, or in surface runoff waters. Chlorobenzilate adsorbs to sediment and suspended particulate material in water. It is thought not to volatilize in water but may be subject to biodegradation.

• Degradation products

The product of chlorobenzilate degradation is 4,4 -dichlorobenzophenone.

• Volatilization/evaporation

Due to its strong adsorption to soil particles and low vapour pressure, chlorobenzilate is thought not to volatilize from soil and water surfaces.

• Bioaccumulation

Chlorobenzilate should not bioconcentrate in aquatic organisms.

• Phytotoxicity

Chlorobenzilate is fairly persistent on plant foliage and may be phytotoxic (poisonous) to some plants. It is not absorbed or transported throughout a plant. Chlorobenzilate residues have been found in the peel of citrus fruit. Its half-life in lemon and orange peels ranges from 60 to more than 160 days.

PROPERTIES

Chlorobenzilate is a colourless solid. It has a shelf-life of at least three to five years when stored in a dry place and at minimum storage temperatures.

TABLE I

Parameters

DDT

Common formulation

C₁₄H₉Cl₅

CAS registry number

50-29-3

Use

As a non-systemic stomach and contact insecticide.

DDT IN THE ENVIRONMENT

• Mobility

DDT is not mobile. It adsorbs to soil strongly and should not leach into groundwater.

• Degradation

In the soil, DDT is biologically degradable with a half-life of 2 to more than 15 years. Biodegradation is faster in flooded soils and under anaerobic conditions. It is reported to disappear (75 percent to 100 percent) from soil in 4–30 years. DDT hardly hydrolyses: according to reports, its hydrolysis half-life is 12 years.

In water it is subjected to evaporation with an estimated half-life for evaporation of from several to 50 hours. The direct breakdown of a compound by light in an aqueous solution occurs very slowly, with a half-life exceeding 150 years. Indirect photolysis processes (initiated by natural substances) may be an important step in DDT transformations; its half-life then is a few days. Biodegradation in water is generally poor.

• Degradation products

Typical metabolic or chemical reduction products are DDE under aerobic conditions, and DDD to DDA under anaerobic conditions.

• Volatilization/evaporation

Not relevant.

• Bioaccumulation

If DDT is released into water it adsorbs strongly to sediments and significantly bioconcentrates in fish.

• Phytotoxicity

Not applicable.

PROPERTIES

DDT forms colourless crystals. It is resistant to destruction by light and oxidation. Dehydrochlorination may occur above 50°C.

TABLE J

Parameters

Diazinon

Common formulation

C₁₂H₂₁N₂O₃PS

CAS registry number

333-41-5

Use

As an insecticide, mainly applied to fruit trees, horticultural crops, rice, sugar cane, etc.

DIAZINON IN THE ENVIRONMENT

• Mobility

Diazinon does not bind strongly to soil. It shows moderate mobility.

• Degradation

The values of DT₅₀ in Table K are average values from several DT₅₀ values reported in the field.

Diazinon does not persist in soil. Most of the diazinon applied is lost from soil through chemical and biological degradation within about two months of application. Hydrolysis has been reported to be slow at pH greater than 6, but may be significant in some soils.

Biodegradation is thought to be a major fate process in soils with reported half-lives of more than 1.2 to 5 weeks in non-sterile soils, as compared with half-lives of 6.5 to 12.5 weeks in sterile soils.

The rate of chemical degradation of diazinon strongly depends on environmental acidity. Diazinon is more stable in alkaline environments than at a neutral or an acidic pH value. Hydrolysis halflives are of 32 days (pH 5), 185 days (pH 7.4) and 136 days (pH 9) at 20°C.

• Degradation products

No data available.

• Volatilization/evaporation

Evaporation from the surface of soil is thought not to be an important transport process. Evaporation from a river may be significant, with a half-life of 46 days.

• Bioaccumulation

Diazinon is thought to sorb moderately to sediments but does not bioaccumulate in aquatic organisms.

• Phytotoxicity

About 50 percent of the diazinon was lost from treated rice plants within nine days through volatilization from the paddy water and transpiration from the leaves. Less than 10 percent of the radioactivity remains in plants and parent compounds.

PROPERTIES

Diazinon is a colourless liquid. It is more stable in alkaline environments than at a neutral or an acid pH. It has a shelf-life of at least three to five years when stored in a dry place and at minimum storage temperature.

TABLE K

Parameters

Dieldrin

Common formulation

C₁₂H₈CI₆O

CAS registry number

60-57-1

Use

This stereoisomer of endrin is used mainly to protect wood and wooden structures against attack by insects and termites, and by industry to protect against textile pests.

DIELDRIN IN THE ENVIRONMENT

• Mobility

If released into the soil, dieldrin binds strongly to it. It shows low mobility and remains immobile (Rf = 0.00), even at high temperatures and with prolonged leaching.

• Degradation

Dieldrin released into the soil persists for an extremely long time (more than seven years). However, it is lost from the soil very rapidly in tropical areas, with up to 90 percent disappearing within one month. Its low water solubility and strong adsorption to soil make leaching unlikely.

When released into the water system it does not undergo hydrolysis or biodegradation. It is subject to photolysis with a half-life of approximately four months, or somewhat faster in waters containing a photosensitizer.

• Degradation products

There is some evidence that microorganisms can form photodieldrin from dieldrin.

• Volatilization/evaporation

Small quantities of dieldrin may volatilize from the soil or be carried into the atmosphere on dust particles. Evaporation from water may be an important process (half-life of hours to months).

• Bioaccumulation

In water, dieldrin is thought to adsorb to sediments and to bioaccumulate in aquatic organisms.

• Phytotoxicity

The toxicity of dieldrin for higher plants is low.

PROPERTIES

Dieldrin forms tan flakes. It is stable in the presence of light, moisture, alkalis and mild acids but is sensitive to concentrated mineral acids, acid catalysts, acid oxidizing agents and active metals.

TABLE L

Parameters

Dimethoate

Common formulation

C₅H₁₂NO₃PS₂

CAS registry number

60-51-5

Use

As an insecticide.

DIMETHOATE IN THE ENVIRONMENT

• Mobility

Highly soluble in water and adsorbing to soil, dimethoate may leach considerably.

• Degradation

Dimethoate does not persist. Soil half-lives of 4 to 16 days and as high as 122 days have been reported. Half-lives between 2.5 and 4 days were reported during drought and moderate rainfall conditions. Dimethoate breaks down faster in moist soils and is rapidly broken down by most soil microorganisms.

It is subject to significant hydrolysis, especially in alkaline waters. Hydrolysis half-lives of 3.7 and 118 days at pH 9 and pH 7 respectively have been estimated.

• Degradation products

No data available.

• Volatilization/evaporation

Evaporation from open waters is not believed to be significant.

• Bioaccumulation

It is thought not to bioaccumulate in aquatic organisms.

• Phytotoxicity

Dimethoate is not toxic to plants.

PROPERTIES

Dimethoate is a colourless solid. It undergoes rapid degradation in the environment and in sewage treatment plants.

TABLE M

Parameters

Dinoseb

Common formulation

C₁₀H₁₂N₂O₅

CAS registry number

88-85-7

Use

As a phenolic herbicide applied to soybeans, vegetables, fruits, nuts, citrus fruits and other field crops. It is also used as an insecticide for grapes and as a seed crop drying agent.

DINOSEB IN THE ENVIRONMENT

• Mobility

The phenolic form of dinoseb is slightly soluble in water and moderately sorbed by most soils. Studies have shown soil sorption capacity to be much greater at lower pH values. Thus, it should present only a moderate risk to groundwater. On the other hand, the ammonium and amine salt forms of dinoseb are much more watersoluble and much less strongly bound to soils. These may pose a significant risk to groundwater.

• Degradation

Dinoseb is of low persistence regardless of its form (phenolic or salt). Reported field half-life of both types of dinoseb range from 5 to 31 days. An overall representative value is estimated to be 20–30 days in most circumstances, although persistence may be much longer in the vadose zone. Photodegradation and microbial breakdown may play roles in the breakdown of dinoseb in the soil environment.

Photodegradation may occur in surface waters, but hydrolysis is essentially negligible.

• Degradation products

No data available.

• Volatilization/evaporation

Volatilization from water is thought not to be an important removal process. Vapour-phase dinoseb is degraded photochemically, with a half-life of 14 days.

• Bioaccumulation

Dinoseb is thought not to bioaccumulate in aquatic organisms.

• Phytotoxicity

Dinoseb persists on treated crop soils for two to four weeks under average conditions of use.

PROPERTIES

Dinoseb is a reddish-brown liquid or dark brown solid. The ester is slowly hydrolysed in the presence of water and is sensitive to acid or alkali. The shelf-life is a minimum of two years.

TABLE N

Parameters

Endosulfan

Common formulation

C₉H₆Cl₆O₃S

CAS registry number

115-29-7

Use

As an insecticide for vegetable crops.

ENDOSULFAN IN THE ENVIRONMENT

• Mobility

Endosulfan is relatively immobile in soil. It adsorbs to soil strongly.

• Degradation

Endosulfan is biodegradable. The beta isomer is more stable. Reports mention soil half-lives of 60 days for alpha-endosulfan and 800 days for beta-endosulfan. Endosulfan may be subject to hydrolysis. Hydrolysis half-lives of 35.4 (alpha-endosulfan) and 37.5 days (betaendosulfan) have been determined at a pH of 7. At a pH of 5.5 the halflife may be as high as 187.3 for beta-endosulfan. The hydrolysis of endosulfan occurs faster in the presence of ferric hydroxide.

Its half-life in streams, rivers and lakes was estimated at 5.7, 7.2 and 304 days, respectively.

• Degradation products

The major degradation product is endosulfan sulphate.

• Volatilization/evaporation

Expectations are that endosulfan isomers exhibit only a minimum of volatilization and leaching into groundwater.

• Bioaccumulation

In water, endosulfan is thought to bioaccumulate in aquatic organisms.

• Phytotoxicity

In most fruits and vegetables, 50 percent of the residue is lost in three to seven days.

PROPERTIES

Endosulfan is a brown crystalline solid. It is composed of alphaendosulfan and beta-endosulfan. Endosulfan is stable in sunlight but unstable in alkaline media. It is subject to slow hydrolysis, and to oxidation in the presence of growing vegetation.

TABLE O

Parameters

Endrin

Common formulation

C₁₂H₈Cl₆O

CAS registry number

72-20-8

Use

It is used as insecticide on field crops such as cotton and grains.

ENDRIN IN THE ENVIRONMENT

• Mobility

Its low water solubility and strong adsorption to soil makes leaching into groundwater unlikely. Endrin is thought to maintain slight mobility in soil.

• Degradation

Endrin appears to be resistant to biodegradation in natural waters and most soils. Released to soils, it will persist for extremely long periods of time. Soil biodegradation half-lives of approximately 4–14 years or more have been reported. Biodegradation may be enhanced somewhat in flooded soils or under anaerobic conditions.

Endrin released to water systems will not hydrolyse. It will be subject to photodegradation to ketoendrin.

• Volatilization/evaporation

Small amounts of endrin may volatilize from soil or be carried by dust particles into the air. Evaporation from water will not be significant.

• Bioaccumulation

On the base of log K_ow endrin is thought to significantly accumulate in aquatic organisms.

• Phytotoxicity

It is not phytotoxic.

PROPERTIES

Endrin is a colourless to tan crystalline solid.

TABLE P

Parameters

Fenitrothion

Common formulation

C₉H₁₂NO₅PS

CAS registry number

122-14-5

Use

As a contact insecticide; it is effective against a wide range of pests, e.g. penetrating, chewing and sucking insects.

FENITROTHION IN THE ENVIRONMENT

• Mobility

Fenitrothion shows medium to low mobility in soil.

• Degradation

Fenitrothion is biodegraded in soil by co-metabolism. Biodegradation occurs more rapidly under anaerobic conditions than under aerobic conditions. The biodegradation half-life of fenitrothion ranges from 4.4 to 53.7 days in non-flooded soils, and from 3.9 to 10.9 days in flooded soils.

At neutral pH values, the abiotic hydrolysis of fenitrothion in soil is not important. It increases, however, in alkaline environments. A halflife of 4.4 years was estimated for soil samples at pH 7.2. On the soil surface, fenitrothion is subject to photolysis, a process that may occur very rapidly. Photolysis half-life has been estimated at one day. For comparison, the volatilization half-life was found to be more than 12 days.

• Degradation products

The products of degradation are aminonitrophenol and demethyl aminofenitrothion.

• Volatilization/evaporation

According to estimates, the maximum volatilization half-life in an acid environment is 180 days. The volatilization half-life of fenitrothion in lake and brook water was estimated at 21 and 5 days, respectively.

• Bioaccumulation

Expectations are that in water, fenitrothion adsorbs moderately to strongly to suspended particles and sediments, and that it accumulates moderately in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Fenitrothion is a yellow liquid. It is not stable in an alkaline environment.

TABLE Q

Parameters

Fenthion

Common formulation

C₁₀H₁₅O₃PS₂

CAS registry number

55-38-9

Use

As an insecticide against many biting pests, fruit flies, mosquitoes, etc.

FENTHION IN THE ENVIRONMENT

• Mobility

Fenthion adsorbs fairly strongly to soil particles and is thought to have very low mobility. It is thought not to move (or leach) throught soil.

• Degradation

When released into soil or water, fenthion degrades through photodegradation and biodegradation. It has moderate persistence in soil, with an average field half-life of 34 days under most conditions. In soil, residues of fenthion may persist for approximately four to six weeks. In one study of its persistence in water, 50 percent of applied fenthion remained in river water for two weeks, while 10 percent remained after four weeks. It is more rapidly degraded under alkaline conditions. The persistence half-life of fenthion in water under field conditions is reported to range from 3 to 21 days for various oceans, rivers and swamps. However, it may be more persistent in some environments, such as salt marsh sediments, where light and oxygen are limited.

• Degradation products

No data available.

• Volatilization/evaporation

Fenthion is thought not to volatilize.

• Bioaccumulation

Based on the value of K_ow (= 25) fenthion accumulates slightly in aquatic organisms.

• Phytotoxicity

Fenthion is phytotoxic (harmful to plants) to American linden, hawthorn and sugar maple trees, and to certain rose varieties. It is not considered phytotoxic when used at recommended rates, although injury has occurred in certain varieties of apples and cotton. Only about 10 percent of applied fenthion remained on rice plants after six hours. Almost half of the activity was found in the rice bran, 6.5 percent was in the husk, and 14.7 percent was in polished rice. Watersoluble metabolites were found 14 days after fenthion application to rice plants.

PROPERTIES

Pure fenthion is a colourless liquid. Fenthion is stable in the presence of light but may be subject to hydrolysis.

TABLE Q

Parameters

Fluoroacetamide

Common formulation

C₂H₄FNO

CAS registry number

640-19-7

Use

Formerly, as an insecticide on fruits to control insects, aphids and mites.

FLUOROACETAMIDE IN THE ENVIRONMENT

• Mobility

The low value of K_oc indicates a very high mobility for fluoroacetamide.

• Degradation

The primary decomposition process of fluoroacetamide in soil and water may be microbial degradation. Persistence (as determined by aphid toxicity) lasted for three weeks or less in soils at a concentration of 10 ppm during the test, and from 9 to 11 weeks at a concentration of 50 ppm. Aqueous hydrolysis is very slow (half-life of 2.4 years at pH 7).

• Degradation products

No data available.

• Volatilization/evaporation

Not applicable.

• Bioaccumulation

Bioaccumulation is thought not to be important in aquatic environments.

• Phytotoxicity

Not applicable.

PROPERTIES

Fluoroacetamide is a colourless crystalline powder. It sublimes on heating.

TABLE S

Parameters

HCH (mixed isomers)

Active ingredient

γ-hexachlorocyclohexane (lindane)

Common formulation

C₆H₆Cl₆

CAS registry number

α- hexachlorocyclohexane 319-84-6

β- hexachlorocyclohexane 319-85-7

γ- hexachlorocyclohexane (lindane) 58-89-9

δ- hexachlorocyclohexane 319-86-8

Use

Hexachlorocyclohexane is mainly used as insecticide and as an agent against ecoparasites in veterinary and pharmaceutical products.

HCH (MIXED ISOMERS) IN THE ENVIRONMENT

• Mobility

Generally, the adsorption of HCH-isomers is rather strong. Less than 1 percent of the load reaches the groundwater. Based on the solubility of the different HCH isomers (0.2–9 mg/l) it can be expected that diffusion of HCH in the soil by leaching and subsequent percolation is possible.

• Degradation

HCH isomers were long considered to be persistent in aerobic environments, but they readily undergo biodegradation in predominantly anaerobic ecosystems such as flooded soils and lake sediments. Results of field studies showed that the relative rates of bioconversion of HCH isomers appeared to be γ-HCH > α-HCH > β-HCH » δ-HCH. In soils, average half-lives of 20–50 days for g-HCH and about 20 weeks for α-HCH were observed.

Breakdown of HCH in surface water takes place by both biological and chemical degradation.

• Degradation products

The most important metabolites of HCH isomers are γ-pentachlorocyclohexene, chlorobenzenes (tri-hexa) and chlorophenoles. It is not known to which level these metabolites can threaten the soil. It is known, however, that in aerobic conditions, chlorobenzenes are very persistent.

• Volatilization/evaporation

Because of the low vapour pressure and the high adsorption. HCH will evaporate slowly from the soil and the water.

• Bioaccumulation

Hexachlorocyclohexanes are thought to bioaccumulate in aquatic organisms.

• Phytotoxicity

Not applicable.

TABLE T

Parameters

Heptachlor

Common formulation

C₁₀H₅Cl₇

CAS registry number

76-44-8

Use

Primarily as an insecticide against termites, ants, soil insects in seed grains and on crops.

HEPTACHLOR IN THE ENVIRONMENT

• Mobility

Heptachlor and its epoxide bind moderately to soils and should not be highly mobile.

• Degradation

Heptachlor and heptachlor epoxide are highly persistent in soils, with a reported representative field half-life of 250 days. Data collected in Mississippi, New Jersey and Maryland showed a soil half-life for heptachlor of 0.4 to 0.8 years. The mean disappearance rates of heptachlor from soil ranged from 5.25 to 79.5 percent per year. depending on the soil type and mode of application. The highest rates of degradation were observed in sandy soils following an application of a granular formulation. Soil incorporation also led to rapid disappearance rates in all soil types. This compound has sometimes been detected in trace amounts in soil 14 to 16 years after application. Because of their long residence times, even low mobility may result in appreciable movement; thus heptachlor and its metabolite (heptachlor epoxide) may be considered to pose the risk of groundwater contamination over time. Very low levels of heptachlor have been found in well water. Heptachlor epoxide is not very susceptible to biodegradation, photolysis, oxidation or hydrolysis in the environment.

Heptachlor is almost insoluble in water, and enters surface waters primarily though drift and surface runoff. In water, heptachlor readily undergoes hydrolysis to a compound that is then readily processed (preferentially under anaerobic conditions) by micro-organisms into heptachlor epoxide. After hydrolysis, volatilization, adsorption to sediments, and photodegradation may be significant routes for the disappearance of heptachlor from aquatic environments.

• Degradation products

The degradation products of heptachlor are hydroxychlordane and 1-hydroxy-2,3-epoxychlordene.

• Volatilization/evaporation

Volatilization from soil surfaces, especially wet ones, is the major route of loss of heptachlor.

• Bioaccumulation

Heptachlor exhibits a high tendency for bioaccumulation in aquatic organisms.

• Phytotoxicity

In plants, the major breakdown product of heptachlor is the epoxide. Heptachlor is non-phytotoxic when used as directed.

PROPERTIES

Heptachlor is either a white wettable powder or a concentrate. It is stable in the presence of light, air, moisture and moderate heat (up to 160°C).

TABLE U

Parameters

Hexachlorobenzene

Common formulation

C₆Cl₆

CAS registry number

118-74-1

Use

In agriculture as a selective fungicide for seed treatment of wheat against bunt.

HEXACHLOROBENZENE IN THE ENVIRONMENT

• Mobility

Hexachlorobenzene adsorbs strongly to soil and is thought not to be mobile in soil. However, it is suggested that it may be transported in low organic carbon soils.

• Degradation

Hexachlorobenzene is a very persistent environmental chemical due to its chemical stability and resistance to biodegradation. Little biodegradation occurs.

• Degradation products

The degradation products of hexachlorobenzene are 1.3-dichlorobenzene and 1,3,5-trichlorobenzene.

• Volatilization/evaporation

The volatilization of the compound from water is rapid (half-life of eight hours), but its strong adsorption to sediment can result in long periods of persistence. If released into the atmosphere, HCB exists primarily in the vapour phase and degradation is extremely slow, with an estimated photodegradation half-life of two years.

• Bioaccumulation

Hexachlorobenzene is strongly accumulated in organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Hexachlorobenzene forms white needles. Hexachlorobenzene is extremely stable even in acid and alkaline environments.

TABLE V

Parameters

Lindane (γ-hexachlorocyclohexane)

Common formulation

C₆H₆CI₆

CAS registry number

58-89-9

Use

As an insecticide and fumigant; applied to a wide range of soil-dwelling and plant-eating insects. Commonly used on a wide variety of crops, in public health to control insect-borne disease, and as a seed treatment.

Warning

In the literature, is not always clear whether measured concentrations refer only to the γ isomer or to the sum of the isomers.

LINDANE IN THE ENVIRONMENT

• Mobility

Lindane exhibits a low affinity for soil binding and may be mobile in soils that have especially low organic matter content.

• Degradation

Lindane is highly persistent in most soils, with a field half-life of approximately 15 months. When sprayed on the surface, its half-life is typically much shorter than when it is incorporated into the soil. It may pose a risk of groundwater contamination.

Lindane is very stable in both fresh- and saltwater environments, and it is resistant to photodegradation. It disappears from the water by secondary mechanisms such as adsorption on sediment, biological breakdown by microflora and fauna, and adsorption by fish through gills, skin and food.

• Degradation products

The main degradation products of lindane are γ-pentachlorocyclohexene, chlorobenzenes (tri-hexa) and chlorophenoles. It is not known to which level these metabolites can threaten the soil. It is known however, that in aerobic conditions chlorobenzenes are very persistent.

• Volatilization/evaporation

Not applicable.

• Bioaccumulation

Lindane moderately accumulates in water organisms.

• Phytotoxicity

Plants may pick up residues not only from direct application, but through the water and vapour phases. Persistence is seen when plants are rich in lipid content, and crops such as cauliflower and spinach build up less residue than crops such as carrots. The metabolism in plants is not well understood, but carrots are estimated to metabolize lindane, with a half-life of just over ten weeks (based on plant uptake) whereas it may have a half-life in lettuce of only three to four days.

PROPERTIES

Lindane is a white to yellow crystalline powder. In its original packing, it is stable for several years, but decomposes in the presence of iron, aluminium and zinc powder and water. Metals corrode if they come into contact with lindane. In alkaline environments, the compound is not stable.

TABLE W

Parameters

Property	Parameter	Unit	Value	Conclusion
Melting point		°C	113
Vapour pressure		mPa	5.6
Density		g/cm	1.85
Degradation	DT50soil	Months	15	Very slightly degradable
Solubility	Solubility (water)	mg/l	7.3	Readily soluble
Mobility	Log Koc		3.04	Moderately mobile
ADI		mg/kg/day	0.008
Permissible Concentrations	Human:
	Direct contact	mg/kg dm soil	4 000
	Consumption of vegetables	mg/kg dm soil	1
	Consumption of drinking-water	μg/l	160

Malathion

Common formulation

C₁₀H₁₉O₆PS₂

CAS registry number

121-75-5

Use

As an insecticide against many insects, including aphids, spider mites and scale insects, as well as large number of other insects which attack fruits, vegetables and stored products.

MALATHION IN THE ENVIRONMENT

• Mobility

Malathion moderately sorbs to the soil and is moderately mobile.

• Degradation

If malathion is released into soil, it is subject to significant biodegradation and hydrolysis. Biodegradation may be an important fate process, especially in soils at pH 7 where the rate of hydrolysis may be slow. Reported biodegradation half-lives in soils range from four to six days.

Malathion in water is subject to hydrolysis with a half-life range of 0.2 weeks at pH 8 to 21 weeks at pH 6.

• Degradation products

The major degradation products are malaothion, malathionbetamonoacid, diethyl malthe and malaoxon.

• Volatilization/evaporation

Expectations are that volatilization is of little importance.

• Bioaccumulation

In water, malathion is thought not to bioaccumulate significantly in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Malathion is a clear amber liquid. It hydrolyses above pH 7 and below pH 5. It is stable in solution buffered to pH 5.26.

TABLE X

Parameters

Mancozeb

Common formulation

[-SCS.NHCH₂CH₂NHCS.S.Mn-]_x (Zn)_y

CAS registry number

8018-01-7

Use

To protect many fruit, vegetable, nut and field crops against a wide range of fungal diseases

MANCOZEB IN THE ENVIRONMENT

• Mobility

Based on the adsorption coefficient, mancozeb is thought to be slightly mobile in soil.

• Degradation

Mancozeb is of low soil persistence, with a reported field half-life of one to seven days. Mancozeb rapidly and spontaneously degrades to ETU in the presence of water and oxygen. ETU may persist for longer, somewhere in the order of five to ten weeks. Because mancozeb is practically insoluble in water, it is unlikely to infiltrate groundwater. Mancozeb degrades in water, with a half-life of one to two days in slightly acidic to slightly alkaline conditions.

• Degradation products

The major mancozeb metabolite of toxicological significance is ethylenethiourena (ETU), with carbon disulfide as a minor metabolite. A metabolite of mancozeb has the potential to be mobile in soils.

• Volatilization/evaporation

Not applicable.

• Bioaccumulation

Because mancozeb hydrolyses rapidly, it does not bioconcentrate in aquatic organisms.

• Phytotoxicity

When used as directed, mancozeb is not poisonous to plants.

PROPERTIES

Mancozeb is a greyish-yellow powder that on heating decomposes at 150°C without melting.

TABLE Y

Parameters

Mercuric chloride

Common formulation

Cl₂Hg

CAS registry number

7487-94-7

Use

To preserve wood and anatomical specimens, as an intensifier in photography and as an insecticide and fungicide in medication (antiseptic, disinfectant).

MERCURIC CHLORIDE IN THE ENVIRONMENT

• Mobility

Not applicable.

• Degradation

Inorganic forms of mercury (Hg) can be converted into organic forms by microbial action in the biosphere.

• Degradation products

The major degradation products are mercuric chloride (I) and organic forms of mercury.

• Volatilization/evaporation

Certain bacteria are capable of transforming mercuric ions into the volatile element mercury. In the volatile phase, it can be transported hundreds of kilometres.

• Bioaccumulation

Many organisms are capable of accumulating mercury from water.

• Phytotoxicity

Not applicable.

PROPERTIES

Mercuric chloride is a colourless crystalline powder. It is slightly volatile at normal temperatures. In sunlight, mercuric chloride may decompose in the presence of organic matter to metallic mercury.

TABLE Z

Parameters

Methamidophos

Common formulation

C₂H₈NO₂PS

CAS registry number

10265-92-6

Use

As an insecticide for control of potatoes, pome fruits, stone fruits, citrus fruits, cotton, maize and other crops.

METHAMIDOPHOS IN THE ENVIRONMENT

• Mobility

Methamidophos is thought to be highly mobile in soil.

• Degradation

Methamidophos readily degrades in soil. Metabolic degradation takes place in sandy soils on a extremely small scale. It is higher in loamy sands and reaches the highest rate in silt loam.

• Degradation products

No data available.

• Volatilization/evaporation

Based on measured vapour pressure, methamidophos slowly volatilizes from dry soil surface and is thought to slowly volatilize from water (with a half-life for a model river of 91 years and for a model lake of 998 years).

• Bioaccumulation

The accumulation of methamidophos in aquatic organisms is not important.

• Phytotoxicity

Not applicable.

PROPERTIES

Methamidophos forms colourless crystals. It is stable at ambient temperatures but 50 percent is decomposed in 140 hours at 40 C. It is stable at pH 3–8, but hydrolysed in acids and alkalis, more rapidly at higher temperatures.

TABLE AA

Parameters

Mirex

Common formulation

C₁₀Cl₁₂

CAS registry number

2385-85-5

Use

As insecticide formerly used to control ants. It was also formerly employed as a fire-retardant additive in thermoplastic, thermosetting, elastomeric resin systems, paper paint, etc.

MIREX IN THE ENVIRONMENT

• Mobility

The K_oc value of mirex indicates that it will be immobile in most soils.

• Degradation

Mirex is a highly stable insecticide. For the most part mirex is resistant to biological and chemical degradation.

• Degradation products

Persistent compounds such as kepone, and monohydro- and dihydroderivatives of mirex have been identified as products of the extremely slow transformation of mirex.

• Volatilization/evaporation

Mirex does not leach into the soil profile and is predicted to volatilize only slowly.

• Bioaccumulation

On the base of log K_ow mirex is thought to accumulate significantly in organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Mirex forms snow-white crystals from benzene. It is a highly stable insecticide. It has also been employed as flame retardant.

TABLE BB

Parameters

Monocrotophos

Common formulation

C₇H₁₄NO₅P

CAS registry number

6923-22-4

Use

As an insecticide and acaricide on cotton, potatoes, peanuts, etc.

MONOCROTOPHOS IN THE ENVIRONMENT

• Mobility

Monocrotophos is thought to have very high mobility in soil.

• Degradation

Degradation of monocrotophos depends strongly on the acidity of the soil. A DT₅₀ of 96 days (pH 5), 66 days (pH 7) and 17 days (pH 9) was calculated.

• Degradation products

No data available.

• Volatilization/evaporation

Monocrotophos is thought not to volatilize from dry soil surface or from water surface.

• Bioaccumulation

In water, monocrotophos is thought not to bioaccumulate in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Pure monocrotophos forms colourless, hygroscopic crystals. It decomposes at a temperature of greater than 38°C.

TABLE CC

Parameters

Paraquat

Common formulation

C₁₂H₁₄N₂

CAS registry number

4685-14-7

Use

As a contact herbicide for weed control in grass seed crops and orchards; as a crop desiccant and defoliant on potato vines and cotton.

PARAQUAT IN THE ENVIRONMENT

• Mobility

The K_oc value for paraquat in soil is in the range 15 473–1 000 000. These high K_oc values indicate that paraquat is strongly bound and almost immobile in soil. Paraquat may also be adsorbed in soil by forming complexes with the humic and fulvic materials present in soil. Therefore, adsorption of paraquat to soil generally increases with an increase in the soil's clay and organic content.

• Degradation

If released into soil, paraquat slowly degrades due to biodegradation. This slow biodegradation is caused by the strong adsorption of paraquat to clay or organic matter in the soil.

Unadsorbed paraquat present in a water solution may biodegrade easily.

Paraquat is completely removed from most surface waters within 8–12 days. Such removal is mainly due to sorbtion to suspended solids and sediment in water.

The hydrolysis of paraquat in the water of soil at neutral pH and acidic pH is not an important loss process.

• Degradation products

The major product of paraquat degradation is paraquat chloride.

• Volatilization/evaporation

Expectations are that volatilization is of little importance.

• Bioaccumulation

In water, paraquat is thought not to bioaccumulate in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Paraquat dichloride forms colourless crystals decomposing at 300°C. Salts are stable in neutral and acid media but are oxidised under alkaline conditions.

TABLE DD

Parameters

Parathion

Common formulation

C₁₀H₁₄NO₅PS

CAS registry number

58-38-2

Use

As an insecticide for wheat and nuts.

PARATHION IN THE ENVIRONMENT.

• Mobility

Parathion strongly adsorbs to soil and exhibits low mobility in soil.

• Degradation

Parathion degrades in soil within several weeks by biological and chemical processes. Degradation is faster in flooded soils. Parathion can be subject to photodegradation. The active metabolite paraxon (which is the product of photodegradation) is more toxic than parathion. The rate of degradation of parathion increases with increasing pH (in alkaline environments).

Adsorption to suspended particles and bottom sediments is the main removal process in open water. Parathion usually disappears within a week. The half-life for photodegradation of parathion in water is one to ten days.

• Degradation products

The degradation products of parathion are p-nitrophenol and diethylthiophosphoric acid.

• Volatilization/evaporation

No data available.

• Bioaccumulation

Not applicable.

• Phytotoxicity

Not applicable.

PROPERTIES

Pure parathion is a pale yellow liquid. It is stable at normal temperatures.

TABLE EE

Parameters

Parathion-methyl

Common formulation

C₈H₁₀NO₅PS

CAS registry number

298-00-0

Use

As an insecticide for rice, fruit and vegetables.

PARATHION-METHYL IN THE ENVIRONMENT

• Mobility

Parathion-methyl is thought to be moderately mobile in soil. Adsorption does not appear to be correlated with the organic content of soil, but the clay content of soil may be important.

• Degradation

Parathion-methyl degrades in soil and water as a result of biological and chemical processes. Loss from soil is primarily due to biodegradation (half-life is ten days to two months). Degradation increases with an increase in temperature and with exposure to sunlight. The major exception is for spills, where degradation occurs only after many years.

The primary process employed to remove the compound from water is biodegradation and photolysis. Within a period of two to four weeks, 100 percent degradation takes place. The hydrolysis occurs (5–11 percent in four days) in rivers and more slowly in marine systems. Parathion-methyl degrades by direct photolysis in natural water (half-life eight days summer, 38 days winter).

• Degradation

No data available.

• Degradation products

No data available.

• Volatilization/evaporation

Volatilization and evaporation are thought not be a significant transport process.

• Bioaccumulation

Based on the octanol-water partition coefficient, parathion-methyl is thought to accumulate moderately in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Parathion-methyl is a white to tan solid. It is not very stable in storage. It undergoes rapid hydrolysis in alkali but hydrolyses slowly in weak acid.

TABLE FF

Parameters

Pentachlorophenol

Common formulation

C₆HCl₅O

CAS registry number

87-86-5

Use

Was used as herbicide, algaecide, defoliant, wood preservative and fungicide.

PENTACHLOROPHENOL IN THE ENVIRONMENT

• Mobility

Pentachlorophenol has the tendency to adsorb to soil and is slightly mobile in soil. Adsorption to soil increases with an increase in the environment's acidity.

• Degradation

Pentachlorophenol biodegrades in both aerobic and anaerobic environments. Aerobic degradation was found to be more rapid than anaerobic degradation. Pentachlorophenol does not appear to oxidize or hydrolyse under environmental conditions; however, photolysis of the dissociated form in water may be an important process.

The loss of pentachlorophenol from a water surface depends on the temperature and pH. A half-life of 328 hours and of 32 120 hours has been reported at pH 5 and pH 6, respectively.

• Degradation products

Terachlorphenol is a major metabolite of pentachlorophenol.

• Volatilization/evaporation

Pentachlorophenol is thought not to volatilize from dry soil surfaces, based on a vapour pressure of 1.1 × 10^-4 mmHg.

• Bioaccumulation

Pentachlorophenol is thought to accumulate in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Pentachlorophenol is a colourless to white solid. It is stable at normal temperatures. At temperatures above 200°C it produces traces of octachlorodibenzo-para-dioxin.

TABLE GG

Parameters

Phosphamidon

Common formulation

C₁₀H₁₉Cl NO₅P

CAS registry number

13171-21-6

Use

As an insecticide for citrus and cotton crops, fruit and nut crops, and rice.

PHOSPHAMIDON IN THE ENVIRONMENT

• Mobility

Phosphamidon is thought to have a great mobility in soil.

• Degradation

Phosphamidon biodegrades in soil, with a half-life of several days or several weeks depending on soil characterisation. Phosphamidon is stable in neutral and weakly acid solutions but is rapidly hydrolysed in alkaline solutions.

• Degradation products

The products of phosphamidon degradation are dimethyl phosphate and alpha-chloroacetoacetic acid diethylamide.

• Volatilization/evaporation

Phosphamidon is thought not to volatilize.

• Bioaccumulation

Based on the low octanol-water coefficient, phosphamidon does not accumulate in aquatic organisms. Its bioconcentration is also unlikely because it is rapidly metabolized in animals.

• Phytotoxicity

Not applicable.

PROPERTIES

Pure phosphamidon is a yellow liquid. The mix of phosphamidon isomers is stable in neutral and acid media and is subject to hydrolysis in an alkaline environment. It decomposes above 160°C.

TABLE HH

Parameters

Propoxur

Common formulation

C₁₁H₁₅NO₃

CAS registry number

114-26-1

Use

As an insecticide with rapid knock-down.

PROPOXUR IN THE ENVIRONMENT

• Mobility

Propoxur does not adsorb to the soil strongly.

• Degradation

Propoxur is biodegradable. Biodegradation half-lives of 44–59 days have been reported. The biodegradation rate increases in soils previously exposed to methylcarbonate. The half-life decreases to as little as 19 days under aerobic conditions, following the addition of glucose and peptone. It is subject to hydrolysis, especially in alkaline environments. The hydrolysis half-life at pH 8 has been estimated at 16 days. In sandy soils, 75 percent of the propoxur was degraded within 100 days, while no loss occurred in that same period in muck and silty loam soils. In these soils, the propoxur persisted for more than six months.

Propoxur is readily degradable in water. Particularly in the presence of humic material, it is subject to relatively rapid photolysis (half-life 13–88 hours).

• Degradation products

The main product of propoxur degradation is 2-isopropoxyphenol.

• Volatilization/evaporation

Expectations are that volatilization is of little importance.

• Bioaccumulation

In water, propoxur is thought not to bioaccumulate in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Propoxur forms colourless crystals. It is unstable in highly alkaline media.

TABLE II

Parameters

Toxaphene

Common formulation

C₁₀H₁₀Cl₈

CAS registry number

8001-35-2

Use

As insecticide for crops, fruits and nuts and agricultural premises.

TOXAPHENE IN THE ENVIRONMENT

• Mobility

A reported K_OC of 2.1 × 10+5 indicates that toxaphene will adsorb very strongly to soils and sediments. It is not expected to be mobile.

• Degradation

Toxaphene is extremely persistent. When released to soil, it will persist for long periods (1 to 14 years). Biodegradation may be enhanced by anaerobic conditions. Toxaphene released in water will not appreciably hydrolyse, photolyse, or significantly biodegrade.

• Degradation products

No data available.

• Volatilization/evaporation

Evaporation from soils and surfaces will be a significant process for toxaphene. The half-life of approximately six hours is estimated for the evaporation of toxaphene from rivers. Toxaphene may undergo extremely slow direct photolysis in the atmosphere. It can be transported long distances in the air (1 200 km), probably adsorbed to particular matter.

• Bioaccumulation

Toxaphene will accumulate very strongly in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

Toxaphene is a mixture of chlorinated camphenes that occur as a waxy amber solid. When heated to decomposition, it emits toxic fumes of hydrochloric acid and other chlorinated compounds. Toxaphene is available as wettable powder, emulsifiable concentrate, dust, granule, oil and emulsion.

TABLE JJ

Parameters

2, 4, 5-T

Common formulation

C₈H₅Cl₃O₃

CAS registry number

93-76-5

Use

As a growth regulator to increase the size of citrus fruits and reduce the excessive drop of deciduous fruits.

2, 4, 5-T IN THE ENVIRONMENT

• Mobility

The adsorption coefficient values the indicate that 2, 4, 5-T mobility in soil varies from highly mobile in sandy soil, to moderately mobile in clay and silty loams, to slightly mobile in muck.

• Degradation

The persistence of 2, 4, 5-T in soil is reported to be 14–300 days, but usually does not exceed one full growing season regardless of the application rate. Degradation under anaerobic conditions in flooded soils is much slower than in moist soils. Chemical hydrolysis in moist soils is thought not to be important.

The dominant removal mechanisms of 2, 4, 5-T from water are photodegradation and biodegradation. The half-life of photolysis of the compound from the surface water has been calculated at 15 days.

• Degradation products

The degradation products are trichlorophenol and trichloranisole.

• Volatilization/evaporation

Based on the low vapour-pressure of 2, 4, 5-T, volatilization is thought to be not significant.

• Bioaccumulation

2, 4, 5-T moderately accumulates in aquatic organisms.

• Phytotoxicity

Not applicable.

PROPERTIES

2, 4, 5-T is a colourless to tan solid. It is stable up to its melting point. Temperatures above 158°C may cause sealed metal containers to burst.

TABLE KK

Parameters

Warfarin

Common formulation

C₁₉H₁₆O₄

CAS registry number

81-81-2

Use

To control rats in and around houses, animal and agricultural premises, etc.

WARFARIN IN THE ENVIRONMENT

• Mobility

No experimental data could be found for the adsorption of warfarin to soil. The estimated log K_oc indicates moderate adsorption to soil.

• Degradation

No data available.

• Degradation products

No data available

• Volatilization/evaporation

Volatilization is thought not to be a significant transport process.

• Bioaccumulation

Based on the estimated octanol-water partition coefficient, warfarin is thought to accumulate moderately in aquatic organisms.

• Phytotoxicity Not applicable.

PROPERTIES

Warfarin is a white powder. It is very stable, even in the presence of strong acids.

TABLE LL

Parameters