3.2 4d 2.3 D 3

Equally of 2011, NPIC stopped creating technical pesticide fact sheets. The old drove of technical fact sheets will remain available in this annal, only they may contain out-of-date material. NPIC no longer has the capacity to consistently update them. To visit our full general fact sheets, click hither. For upwardly-to-date technical fact sheets, please visit the Environmental Protection Agency'due south webpage.

• Chemical Grade and Type
• Physical / Chemical Properties
• Uses
• Way of Activity
• Toxicity Nomenclature
• Astute Toxicity
• Chronic Toxicity
• Endocrine Disruption
• Carcinogenicity
• Reproductive and Teratogenic Effects
• Fate in the Body
• Medical Tests and Monitoring
• Ecology Fate
• Ecotoxicity Studies
• Regulatory Guidelines

Molecular Structure - two,4-D

Laboratory Testing: Before pesticides are registered by the U.South. EPA, they must undergo laboratory testing for short-term (acute) and long-term (chronic) health effects. Laboratory animals are purposely given high plenty doses to cause toxic effects. These tests help scientists estimate how these chemicals might affect humans, domestic animals, and wild fauna in cases of overexposure.

Chemical Class and Blazon:

• 2,four-D is an herbicide and secondarily a plant growth regulator.¹ Formulations include esters, acids, and several salts, which vary in their chemic properties, environmental behavior, and to a bottom extent, toxicity.^two,3 The salt and ester forms are derivatives of the parent acid.² Unless otherwise stated, the discussion in this fact sheet will refer to the acrid form.
• The International Union of Pure and Practical Chemical science (IUPAC) chemical name for the acrid form is 2,4-dichlorophenoxyacetic acid, its Chemic Abstracts Service (CAS) registry number is 94-75-vii, and the chemical family is the phenoxyacetic acid compounds.³
• The dimethyl-amine salt (DMA) and 2-ethylhexyl ester (EHE) forms account for approximately 90-95% of the total global use.⁴ The acid form is low in solubility and herbicide formulations consist of more than soluble forms of the chemical.ⁱⁱ Products containing ii,4-D oft incorporate other herbicides as well.^v
• Amanuensis Orange, the herbicide widely used during the Vietnam state of war, independent 2,4-D. However, the controversy regarding health effects centered effectually the 2,4,v-T component of the herbicide and its contaminant, dioxin.^six,seven
• 2,four-D has been used in the United states since the 1940s, and it was evaluated for re-registration in 2005 past the United States Environmental Protection Bureau (U.S. EPA).³ The U.S. EPA determined that two,4-D was eligible for re-registration, just required sure changes to labeled uses to mitigate chance.ⁱⁱⁱ See the text box on Laboratory Testing.

Concrete / Chemical Properties:

ii,4-D and associated forms8,9
Active Ingredient	CASRN	Form	Vapor pressurea	Henry's constant	Molecular weight	Solubility in water (mg/L)b	Log Kow	Moc
two,iv-D acrid	94-75-seven	White to brown crystalline solid	1.9 x 10-5 Pa 1.four x 10-seven mmHg	viii.6 10 10-6 atm·m3/mol	221	pH 5: 29,934 ± 2957b pH 7: 44,558 ± 674 pH 9: 43,134 ± 336	0.001 Thou sol'n pH 5: 2.xiv pH seven: 0.177 pH nine: 0.102	xx-136
2,4-D table salt	2702-72-nine	White pulverisation	Salt dissociates to acid in water		243.03	45,000 mg/L	Salt dissociates to acid in h2o
2,4-D-diethanolamine salt (DEA)	5742-19-viii	Cream colored powder	9.98 10 ten-8 mmHg		326.18	806,000 mg/Fifty	2.24 10 10-2 -1.65
2,four-D dimethyl amine salt (DMA)	2008-39-1	Bister aqueous liquid	1.33 10 10-five Pa i x 10-vii mmHg	1.iv x 10-16 atm·mthree/mol	266.13	pH 5: 320,632 ± 3645 pH 7: 729,397 ± 86,400 pH nine: 663,755 ± 94,647	See values for 2,4-D acid above	72-136
2,iv-D -isopropylamine (IPA) common salt	5742-17-half dozen	Amber aqueous liquid	Salt dissociates to acrid in h2o		280.04	pH 5: 174,000 mg/L pH 7: 436,000 mg/L pH 9: 331,000 mg/L	Salt dissociates to acid in water
2,4-D tri-isopropanolamine (TIPA) salt	32341-80-3	Bister aqueous liquid	Salt dissociates to acid in water		412.31	pH 5: 461,000 mg/L pH 7: 461,000 mg/Fifty pH ix: 104,000 mg/L	Table salt dissociates to acid in water
2,4-D BEE	1929-73-three	Dark amber liquid	3.2 ten 10-4 Pa 2.iv x 10-6 mmHg		321.2	Practically insoluble in water	4.1
2,4-D two-ethylhexyl ester (EHE)	1928-43-4	Dark amber liquid	4.viii 10 10-iv Pa iii.half-dozen x x-vi mmHg		333.27	0.0867 mg/L	5.78
2,iv-D -isopropyl ester (IPE)	94-11-one	Pale amber liquid	1.87 Pa 5.three 10 10-half-dozen mbar	2.2 x x-half-dozen atm·m3/mol	263.12	Practically insoluble in water	253.8 ± 44.4	600
aVapor pressure measured at 25 °C				bSolubility in water given for unbuffered solution

Uses:

• 2,iv-D is used for broadleaf weed control in agricultural and nonagricultural settings, and it is registered for use in both terrestrial and aquatic environments. Major sites include pasture and rangeland, residential lawns, roadways, and cropland. Crops treated with two,4-D include field corn, soybeans, spring wheat, hazelnuts, sugarcane, and barley.³ Uses for products containing 2,4-D vary widely. Always read and follow the label when applying pesticide products.
• Approximately 46 million pounds are used each year in the United States, based on data from 1992-2000.^three
• Signal words for products containing 2,4-D may range from Caution to Danger.¹⁰ The signal word reflects the combined toxicity of the active ingredient and other ingredients in the product. See the pesticide label on the product and refer to the NPIC fact sheets on Point Words and Inert or "Other" Ingredients.
• To find a list of products containing 2,4-D which are registered in your country, visit the website http://npic.orst.edu/reg/state_agencies.html select your state then click on the link for "State Products."

Fashion of Action:

Target Organisms

• 2,4-D is used on a wide variety of terrestrial and aquatic broadleaf weeds. Information technology has little effect on grasses.¹² Information technology appears to work by causing uncontrolled cell segmentation in vascular tissue.¹² Abnormal increases in cell wall plasticity, biosynthesis of proteins, and production of ethylene occur in found tissues following exposure, and these processes are responsible for uncontrolled cell segmentation.^iii,12
• The ester forms of 2,4-D penetrate leafage, whereas constitute roots absorb the salt forms.¹² two,four-D appears to exist similar in activity to other auxin-type herbicides.¹²

Non-target Organisms

• The modes of toxicity to animals from the acrid, ester and salt forms of 2,4-D are like. The chief exception is that the salt and acid forms tin be farthermost heart irritants.^three ii,iv-D is actively secreted by the proximal tubules of the kidney, and toxicity appears to result when renal clearance capacity is exceeded.³ Dose-dependent toxic effects include damage to the eye, thyroid, kidney, adrenals, and ovaries or testes.³ In addition, researchers have observed neurotoxicity, reproductive toxicity, and developmental toxicity.³ Chlorophenoxy herbicides exhibit a variety of mechanisms of toxicity, including dose-dependent cell membrane damage leading to fundamental nervous system toxicity,xiii interference with cellular metabolism involving acetyl-coenzyme A (CoA),¹³ and uncoupling of oxidative phosphorylation due to either the disrupted CoA activity or cellular membrane harm.¹³

Acute Toxicity:

Oral

• LD_fifty values range from 639 mg/kg to 1646 mg/kg in rats depending on the chemical grade of 2,4-D utilized in the study.³ Researchers found that 2,4-D was more than toxic for mice, reporting an LD_l of 138 mg/kg.^ane All chemic forms for two,iv-D are considered low in toxicity¹¹ for acute oral exposure based on tests with rats.³ See the text boxes on Toxicity Nomenclature and LD₅₀/LC₅₀ .

LD_l/LC₅₀: A common measure of astute toxicity is the lethal dose (LD₅₀) or lethal concentration (LC₅₀) that causes death (resulting from a unmarried or limited exposure) in 50 percentage of the treated animals. LD₅₀ is more often than not expressed equally the dose in milligrams (mg) of chemical per kilogram (kg) of torso weight. LC_fifty is oft expressed as mg of chemic per volume (e.g., liter (L)) of medium (i.e., air or water) the organism is exposed to. Chemicals are considered highly toxic when the LD₅₀/LC_fifty is modest and practically non-toxic when the value is large. However, the LD₅₀/LC₅₀ does not reflect whatever effects from long-term exposure (i.due east., cancer, birth defects or reproductive toxicity) that may occur at levels below those that cause decease.

Dermal

• Acute dermal LD₅₀s ranged from 1829 mg/kg to greater than 2000 mg/kg in rabbits depending on the chemical form of ii,four-D. All chemical forms of 2,4-D are considered depression in toxicity for acute dermal exposure based on studies using rabbits.³
• The acid and salt forms of ii,4-D are highly toxic to eye tissue, causing astringent centre irritation. This is reflected in the signal word of the formulated product. The ester forms are not considered eye irritants, and have Iow to very low ocular toxicity.³
• The ester and table salt forms of 2,4-D are considered slight pare irritants.ⁱⁱⁱ

Inhalation

• All chemical forms of 2,4-D are of low to very low toxicity via inhalation based on studies using rats. Acute inhalation LC₅₀south for rats ranged from 0.78 mg/L to greater than 5.4 mg/L depending on the chemic form.³ About forms of 2,four-D are very low in toxicity, and the parent acrid and TIPA salt forms are low in toxicity.ⁱⁱⁱ

Signs of Toxicity - Animals

• Dogs fed 2,4-D exhibited myotonia, airsickness, and weakness; dogs are more sensitive to chlorophenoxy acid herbicides than other animals.¹⁴ In add-on, dogs and cats have displayed inappetance, anorexia, ataxia, salivation, diarrhea, lethargy, and convulsions following exposure to 2,4-D, which may include eating treated grass¹⁵ although the potential for this is unclear.^xvi Rats demonstrated incoordination, central nervous system depression and muscular weakness post-obit acute oral dosing.^3,17 Biochemical analysis of rat tissues suggested hepatic and muscle damage post-obit acute, subchronic, and chronic oral exposures.¹⁷

Signs of Toxicity - Humans

• No occupational studies were establish reporting signs or symptoms following exposure to 2,4-D nether normal usage.
• Symptoms of acute oral exposure to 2,iv-D include vomiting, diarrhea, headache, confusion, ambitious or baroque behavior. A peculiar scent is sometimes noted on the jiff. Skeletal musculus injury and renal failure may too occur.^xviii Systemic toxicity is mainly associated with suicide attempts.¹⁸
• Symptoms following dermal exposure may include irritation, and inhalation exposure may lead to cough and burning sensations in the upper respiratory tract and chest.¹⁸ Prolonged exposure may effect in dizziness.^xviii Chlorophenoxy compounds such equally ii,four-D are quickly absorbed when swallowed, simply absorption from dermal or inhalation exposure is low.^13,xviii
• Case reports and observational studies provide the majority of information regarding the toxicological effects of 2,4-D in incidents involving human being poisonings. Researchers compiled the medical cases of 69 people who ingested two,iv-D and other chlorophenoxy herbicides; 23 of these patients died.¹³ Ingestion led to vomiting, abdominal pain, diarrhea, and evolution of hypotension.^xiii Peripheral neuromuscular effects including musculus twitching, weakness, and loss of tendon reflexes have been reported.¹³ Neuromuscular effects have lasted several weeks to months and accept been permanent in some cases.^xiii
• Always follow label instructions and take steps to minimize exposure. If whatever exposure occurs, be sure to follow the Offset Assistance instructions on the product characterization carefully. For additional treatment communication, contact the Poison Control Eye at ane-800- 222-1222. If you wish to talk over an incident with the National Pesticide Information Centre, please call 1-800-858-7378.

TOXICITY CLASSIFICATION - ii,iv-D
	High Toxicity	Moderate Toxicity	Depression Toxicity	Very Low Toxicity
Acute Oral LDl	Up to and including 50 mg/kg (≤ 50 mg/kg)	Greater than l through 500 mg/kg (>50-500 mg/kg)	Greater than 500 through 5000 mg/kg (>500-5000 mg/kg)	Greater than 5000 mg/kg (>5000 mg/kg)
Inhalation LCfifty	Up to and including 0.05 mg/L (≤0.05 mg/50)	Greater than 0.05 through 0.5 mg/L (>0.05-0.5 mg/L)	Greater than 0.5 through 2.0 mg/L (>0.5-two.0 mg/L)	Greater than 2.0 mg/Fifty (>2.0 mg/Fifty)
Dermal LD50	Upward to and including 200 mg/kg (≤200 mg/kg)	Greater than 200 through 2000 mg/kg (>200-2000 mg/kg)	Greater than 2000 through 5000 mg/kg (>2000-5000 mg/kg)	Greater than 5000 mg/kg (>5000 mg/kg)
Primary Heart Irritation	Corrosive (irreversible destruction of ocular tissue) or corneal interest or irritation persisting for more than 21 days (Acid, Ester)	Corneal involvement or other heart irritation clearing in 8 - 21 days	Corneal interest or other centre irritation clearing in 7 days or less (Ester)	Minimal effects immigration in less than 24 hours (Ester)
Primary Skin Irritation	Corrosive (tissue destruction into the dermis and/or scarring)	Severe irritation at 72 hours (severe erythema or edema)	Moderate irritation at 72 hours (moderate erythema)	Balmy or slight irritation at 72 hours (no irritation or erythema) (Ester, Salt)
The highlighted boxes reverberate the values in the "Acute Toxicity" section of this fact sheet. Modeled later the U.S. Environmental Protection Agency, Part of Pesticide Programs, Label Review Manual, Chapter 7: Precautionary Labeling. https://www.epa.gov/sites/default/files/2018-04/documents/chap-07-mar-2018.pdf

NOAEL: No Observable Adverse Effect Level

NOEL: No Observed Effect Level

LOAEL: Lowest Observable Agin Event Level

LOEL: Lowest Observed Issue Level

Chronic Toxicity:

Animals

• Subchronic oral exposure to two,4-D caused impairment to the eye, thyroid, kidney, adrenals, and the ovaries and testes of laboratory animals.^three,19 A subchronic NOEL was established at 15 mg/kg/twenty-four hours based on studies in rats.¹⁹ Run across the text box on NOAEL, NOEL, LOAEL, and LOEL.
• The chronic toxicity NOEL in rats and mice was adamant to exist five mg/kg/mean solar day in ii-twelvemonth studies.^12,20 The maximum tolerated dose in the ii-year rat written report was 150 mg/kg/mean solar day in male rats and 75 mg/kg/mean solar day in females.^twenty Additional NOEL and NOAEL doses were 15 mg/kg for rats in a 90-day study, and 1 mg/kg for dogs in a 12-month study, respectively.^12,21 Rabbits exhibited toxicity following dosing with either acid, common salt, or ester forms of 2,iv-D at doses of thirty mg/kg/day or greater.⁴ Chronic NOAELs and LOELs in dogs, however, varied for different parameters studied and by chemical course.²¹
• Rats showed no outward signs of toxicity following exposure to 200 mg/L of two,4-D in drinking h2o for 30 and 100 days, but biochemical analysis suggested hepatic and musculus damage.¹⁷
• Researchers fed rats 2,4-D at doses of 1, 15, 100, and 300 mg/kg/twenty-four hour period acrid equivalents (ae). Changes in blood and thyroid parameters, organ weight ratios, and body weight gain were noted at 100 and 300 mg/kg/24-hour interval doses.¹⁹ Chronic toxicity in the eye, kidney, thyroid and liver of the rat were similar to effects found in subchronic studies.²⁰ Center lesions were associated simply with high doses of 150 mg/kg/solar day.^xx

Humans

• No human data were constitute on chronic furnishings of 2,4-D other than epidemiological studies of cancer occurrence. Although pesticide use has been linked to Parkinson'due south disease and to respiratory illness in farmers, 2,4-D was not implicated in whatever relationships between pesticide exposure and subsequent affliction.^22,23 See the Carcinogenicity department below for more information on 2,4-D and cancer in humans. See the text box on Exposure.

Exposure: Furnishings of ii,4-D on human being health and the environment depend on how much 2,4-D is present and the length and frequency of exposure. Effects also depend on the health of a person and/or certain environmental factors.

Endocrine Disruption:

• Because 2,four-D has demonstrated toxic effects on the thyroid and gonads following exposure, in that location is business concern over potential endocrine-disrupting effects.ⁱⁱⁱ two,4-D is included in the U.S. EPA June 2007 Draft List of Chemicals for Tier 1 Screening.²⁴

Carcinogenicity:

Animals

• No oncogenic effects were observed in rats or mice following 2 years of dietary exposure of 2,four-D with concentrations ranging from 5-150 mg/kg/twenty-four hour period or five-300 mg/kg/day, respectively.²⁰ Similarly, researchers did not notice immunotoxic or oncogenic responses in dogs dosed with 1.0-7.5 mg/kg/day for either 13 weeks or i twelvemonth.²¹
• A case-control study in companion dogs ended that there was a "modest association" betwixt cancerous lymphoma in the dogs and the utilize of ii,4-D in their owners' yards after accounting for other dwelling house and yard pesticide utilise.²⁵ Other investigators have questioned the epidemiological clan reported in that written report.^5,26
• Overall, there has been no consistent association between exposure to 2,iv-D and tumor induction in animals.²⁷ More recently, non-cytotoxic concentrations of two,4-D were correlated to Dna damage and contradistinct expression of some genes in hamster embryo cells.²⁸

Humans

• The U.S. EPA evaluated 2,four-D for carcinogenic effects in 1988, 1992, and again in 2004. Each evaluation has concluded that "the data are not sufficient to conclude that there is a cause and effect relationship between exposure to 2,4-D and non- Hodgkin's Lymphoma." ii,4-D was categorized as "Group D - not classifiable equally to man carcinogenicity" in 2004.^three See the text box on Cancer.

  Cancer: Authorities agencies in the United states of america and abroad have adult programs to evaluate the potential for a chemical to crusade cancer. Testing guidelines and classification systems vary. To acquire more than about the meaning of various cancer classification descriptors listed in this fact sail, please visit the advisable reference, or call NPIC.

• The International Agency for Research on Cancer (IARC), had not assigned 2,4-D a cancer rating as of June 2008. However, in 1987, IARC placed the family unit of chlorophenoxy herbicides in Group 2B, possibly carcinogenic to humans.²⁹
• A discussion of the history of classification decisions regarding the carcinogenicity of 2,4-D has been published. A confounding factor in determining the carcinogenicity of 2,4-D is the frequent simultaneous exposure of workers to two,4-D in improver to ii,4,5-T and its contaminant TCDD (dioxin), or to other herbicides. Yet, other work examining incidents of exposure to 2,4-D without simultaneous exposure to 2,4,5-T has establish some clan betwixt 2,iv-D and non-Hodgkin'southward lymphoma.²⁶
• Although the costless acrid form of 2,four-D did non damage chromosomes, there is limited evidence that commercial formulations may have the potential to do so.²⁷ Overall, evidence for mutagenicity has been inconsistent.^26,27,30

Reproductive or Teratogenic Effects:

Animals

• Teratogenic effects were non observed in mice, rats, or rabbits unless the excretion capacity of the mother was overwhelmed following oral exposure to two,4-D or its salt and ester forms.^4,26 Reduced fetal viability was observed in hamsters following maternal dosing at forty mg/kg/24-hour interval during pregnancy, although effects did non follow a dose-response relationship.³¹
• Fetal abnormalities were observed in rats following oral doses of xc mg/kg/day or greater get-go at fertilization; these doses were toxic to the mothers likewise.⁴ A NOEL of 25 mg/kg/solar day was derived for fetal rats in one written report, and a NOAEL of 12.5 mg/kg/day for the mothers and a developmental NOAEL of 50 mg/kg/mean solar day for the young were derived in another written report.⁷ The overall maternal NOEL in rats was determined to be eight-17 mg/kg/day and overall developmental NOEL was 30 mg/kg/day ii,4-D acrid equivalents.⁴
• Rabbit fetuses were unaffected at doses below 40 mg/kg/twenty-four hour period administered to the dams although extra ribs were formed at doses above this threshold.^iv In rabbits, the developmental NOEL was thirty mg/kg/day 2,4-D acid equivalents.⁴

Humans

• No experimental information are bachelor regarding the furnishings of 2,4-D exposure on reproduction or development in humans. There are some reports of reproductive effects following occupational exposure to chlorophenoxy herbicides,⁷ including reduced sperm movement and viability following occupational exposure. Although motility and viability recovered over a menstruum of several months, malformations were notwithstanding present.³² Exposure to multiple pesticides in epidemiological studies make inference hard.²⁶

Fate in the Body:

Absorption

• The greatest absorption rates in humans are from oral exposure, with much less absorption occurring post-obit dermal or inhalation exposures.¹⁸ Absorption rates following ingestion are dose-dependent in laboratory animals, with larger doses persisting in the gastrointestinal tract for longer periods of time.⁷ In humans, plasma levels following 5 mg/kg oral ingestion peaked between iv-24 hours post-exposure.^seven
• Dermal exposure is considered the almost likely route of exposure during product utilise.⁷ Absorption of two,4-D across the peel occurs more than slowly and is less complete, and varies by chemical form, product conception, species, and site of application.⁷ Dermal absorption may be increased significantly with application of some sunscreens, insect repellents, or by booze consumption, as demonstrated in laboratory studies using rats and mice.^33,34,35 Hairless mouse skin captivated 39% of a 100 μL dose in 24 hours.³⁴

Distribution

• In laboratory animals, the primary target organs for ii,4-D toxicity were the eye, thyroid, kidney, adrenal glands, and ovaries or testes following subchronic oral exposure at doses above the threshold of saturation for renal clearance.³ Biochemical changes suggested that liver and muscle damage occurred in rats at acute, subchronic, and chronic doses.¹⁷
• In humans, two,4-D has a wide volume of distribution due to its water solubility, but it does not accumulate in any tissue.⁷

Metabolism

• Metabolism of 2,iv-D is minimal in humans, with nearly all of it excreted unchanged as the parent chemical compound.^seven,36 The remainder is excreted as an unspecified ii,4-D cohabit.³⁷
• In animals, niggling 2,4-D is metabolized prior to excretion. Upwards to 3.2% of the applied dose in rats was excreted as an unspecified polar metabolite.²⁶ In sheep and cattle, muscle, liver, kidney, and fat tissue contained the metabolite iv-chlorocatechol. 38 Dogs must metabolize the parent compound prior to excretion, due to their reduced ability to excrete organic acids.³⁹
• No reactive intermediate metabolic products for 2,4-D have been identified in any species.²⁶

Excretion

• In humans, 2,four-D is rapidly excreted from the body, primarily in the urine.⁷ Much of the compound appears to be eliminated unchanged, although some 2,4-D is eliminated from the body as a conjugate.³⁷ The percent of original dose excreted equally a polar, acid-hydrolyzable metabolite was 4.viii-27.0%.²⁶ The elimination half-life from blood plasma in humans orally dosed with five mg/kg of 2,4-D was 11.six hours.³⁷ These human volunteers excreted more than 75% of two,four-D in their urine within 96 hours of oral dosing.³⁶ Concentrations in blood plasma paralleled concentrations excreted in urine.³⁶ Some 2,iv-D may be excreted in perspiration merely this process appears to occur more slowly compared with urinary excretion.⁷
• Excretion of 2,4-D in animals depends on the species, formulation, and dose.⁴⁰ In rats, elimination of orally administered doses of 5 and 50 mg/kg two,4-D took 24 hours, and the urine was composed almost entirely of unmetabolized ii,4-D.³⁹
• Dogs excreted a 5 mg/kg oral dose primarily in their urine with pocket-size amounts detected in feces.³⁹ Dogs dosed with 50 mg/kg excreted equal amounts in urine and feces and excretion was incomplete at 120 hours post-dose.³⁹ Because dogs announced to be deficient in their ability to excrete organic acids, 2,4-D must exist metabolized prior to excretion.³⁹ Dogs orally dosed with 2,iv-D excreted the parent chemical compound, several conjugates and one unidentified compound in their urine.³⁹
• Excretion of 2,4-D in urine is dose-dependent but nonlinear, with percent excreted in urine failing at college doses.⁷ In all of the species of animals studied, two,four-D is excreted quickly and almost entirely in the urine.⁷

Medical Tests and Monitoring:

• Biomarkers of exposure to 2,four-D have been reported in the scientific literature.⁴¹ Scientists used loftier-performance liquid chromatography with tandem mass spectrometry to detect 2,4-D in urine.^41,42
• Laboratory testing for ii,4-D is not widely available to physicians.
• 2,4-D was detected at depression concentrations in urine samples collected from all age groups in a large study of the American public.⁴¹ However, how these residues may affect human health is before long not clear,⁴¹ and the relationship between exposure level and biomarker is unknown.⁴³

The "half-life" is the time required for half of the compound to suspension down in the environment.

1 half-life = l% remaining
2 half-lives = 25% remaining
three half-lives = 12% remaining
four one-half-lives = 6% remaining
5 half-lives = 3% remaining

Half-lives can vary widely based on ecology factors. The amount of chemical remaining after a half-life will always depend on the amount of the chemical originally applied. It should be noted that some chemicals may degrade into compounds of toxicological significance.

Environmental Fate:

Soil

• 2,4-D amine salts and esters are non persistent under near environmental conditions.ⁱⁱⁱ Typically, the ester and amine forms of two,four-D are expected to degrade rapidly to the acrid form.³ Soil half-life values have been estimated at 10 days for the acid, diethylamine salt, and ester forms.⁴⁴ Another written report estimated a soil half-life for the ester form EHE ranging from 1-xiv days with a median half-life of 2.nine days.^three In aerobic mineral soils, a half-life of 6.2 days was estimated.³ A granular formulation of the BEE course was detected in aquatic sediments for 186 days mail-application, perhaps due to either the formulation or irksome de-esterification of the sediment-bound chemic.³ Run across the text box on Half-life.
• Microbial degradation of 2,four-D in soil involves hydroxylation, cleavage of the acid side-chain, decarboxylation, and band opening.¹ The ethyl hexyl form of the chemical compound is rapidly hydrolyzed in soil and water to form the 2,4-D acid.¹ Other comparative studies demonstrated that ester and amine salt forms of 2,4-D have similar soil dissipation rates because they are converted rapidly to the same anionic class.⁴⁵
• ii,4-D has a depression binding affinity in mineral soils and sediment, and in those conditions is considered intermediately to highly mobile.ⁱⁱⁱ In sandy loam, sand, silty clay loam, and loam soil, K_oc values of 70, 76, 59, and 117 mL/grand, respectively, were obtained,^three indicating depression bounden affinity in these soil types. Although two,4-D is highly mobile, rapid mineralization rates may reduce the potential of two,iv-D to affect groundwater.⁴⁶ Microbes may play a major role in deposition.²
• Intermission-down products of 2,iv-D detected in laboratory experiments included 1,ii,4-benzenetriol, 2,4-dichlorophenol (2,4- DCP), 2,4-dichloroanisole (2,4-DCA), iv-chlorphenol, chlorohydroquinone (CHQ), volatile organics, bound residues, and carbon dioxide. These degradates are expected to be of low occurrence in the environment, of low toxicity, or both.³

Water

• The half-life of two,4-D in aerobic aquatic environments was estimated to be 15 days and in anaerobic aquatic laboratory studies, 41-333 days.³ A granular formulation of the BEE course degraded chop-chop in the water cavalcade in alkaline metal conditions but was nowadays in sediments for 186 days.^three
• The ethyl hexyl grade is rapidly hydrolyzed in water to two,4-D acid, with a degradation one-half-life (DT₅₀) of less than i 24-hour interval.¹ Ester forms of 2,4-D hydrolyze at rates that are pH dependent; the hydrolysis half-life of the butoxy ester increased from 9 hours at pH 8 to more one year in more acidic atmospheric condition with a pH of 5.38 The acid class of 2,4-D is very resistant to abiotic hydrolysis.ⁱⁱⁱ
• ii,4-D has been detected in streams and shallow groundwater at depression concentrations, in both rural and urban areas.^3,47,48

Air

• Volatility for about forms of 2,4-D is low (see the table on 2,four-D and associated forms). Yet, the vapor pressure of some ester forms range from i.1 x 10^-3 to 2.three x x^-3 mmHg,^two indicating that these forms readily volatilize. The Henry's Police force Constant for 2,four-D acrid is iii.5 10 10^-4 at pH 7,⁴⁹ indicating low potential for movement from water to air.
• No data were found regarding the degradation of 2,4-D in the atmosphere.

Plants

• The ester forms of 2,4-D penetrate foliage, whereas plant roots absorb the salt forms.¹² Ester forms are converted to the acid within the found, then accumulate in cells due to passive diffusion downwards the concentration gradient.¹² Active transport inside the plant may also occur.¹² Aggregating occurs primarily at the meristem tissue of roots and shoots.¹
• Forest dissipation studies indicated that the ethyl hexyl ester form of ii,4-D degraded slowly on foliage and in leaf litter.³ Residues of an ester form of 2,4-D were detected in samples of dead birch leaves for up to three years mail-awarding.⁵⁰

Indoor

• No data were available on indoor persistence.

Food Residue

• ii,4-D was not included in the listing of pesticides detectable in regulatory monitoring.⁵¹

  Maximum Contaminant Level (MCL): The MCL is the highest level of contaminant that is legally immune in drinking water. The MCL is enforceable. The MCL is typically measured in milligrams (mg) of contaminant per liter (L) of water.

  U.S. Ecology Protection Agency, National Primary Drinking H2o Regulations. https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations#one

• Traces of two,four-D were detected in 49.3% of finished drinking water samples and 53.seven% of untreated water samples (365 and 367 samples taken, respectively), with detections between one.1 and 2416.0 parts per trillion (ppt). These concentrations are well below the maximum contaminant level (MCL) of lxx,000 ppt set by the U.Southward. EPA for finished drinking h2o.⁵² In bottled water, only ii of 367 samples contained 2,4-D, with residues of iii.2 and 4.2 ppt.⁵² See the text box on Maximum Contaminant Level (MCL).

Ecotoxicity Studies:

Birds

• LD_fifty values range from 472 mg/kg for acute oral exposure in pheasants, to 668 mg/kg in pigeons and Japanese quail, to greater than one thousand mg/kg in wild ducks.^one The acute oral LD₅₀ for the dimethyl amine salt form of the chemical compound was 500 mg/kg for bobwhite quail, and the acute oral LD₅₀ for the ethyl hexyl form was 663 mg/kg in mallard ducks. The acute oral LD₅₀ for wild ducks was in excess of 2025 mg/kg for the sodium table salt form of ii,iv-D.¹ Overall, ii,four-D is moderately toxic to practically non-toxic to birds. There are no pronounced differences in toxicity based on the class of two,4-D.³
• V-twenty-four hour period studies estimated LC₅₀ values for bobwhite quail and mallard ducks at greater than 5620 ppm.¹ Chronic studies take besides demonstrated depression toxicity, with no effects observed below very high exposure levels such equally concentrations in drinking water greater than the solubility of the chemical.² Nether field conditions, eggs of ground-nesting birds could be exposed, only eggshell permeability to 2,iv-D is low and treating eggshells with high concentrations of 2,4-D did not reduce hatchability or crusade chick abnormalities.²

Fish and Aquatic Life

• Toxicity to fish and aquatic invertebrates varies widely depending on chemical course, with esters existence the nearly toxic.^1,2 Acid and amine salt LC_ls range from greater than fourscore to 2244 mg acid equivalents per liter (mg ae/Fifty) whereas the esters range from less than 1.0 to 14.5 mg acid equivalents per liter.³ The greater toxicity generally of the esters in fish is probable due to the greater assimilation rates of the esters through the gills, where they are hydrolyzed to the acrid grade.^two The astute LC₅₀ of the dimethyl amine salt form to rainbow trout was 100 mg/L,^one which is considered slightly toxic.
• The acute LC₅₀ of the ethyl hexyl class to rainbow trout was greater than its solubility in water.¹ The LD_l value for the isoctyl form (CASRN 25168-26-7) in cutthroat trout was 0.5-one.2 mg/L,¹ or moderately to highly toxic. Adult fathead minnows exhibited toxic effects at chronic exposures of the butoxyl ethanol ester form that were 1/10 to ane/45 of the 96-hr LC₅₀ concentrations.² Early on life stages of fish are more than susceptible compared with adult fish or eggs.^two
• Daphnia exposed to the acid grade for 21 days exhibited an LC₅₀ of 235 mg/Fifty when exposed to 2,4-D acid for 21 days, and an LC_fifty of five.two mg/L when exposed to the ethyl hexyl form for 48 hours.^ane Therefore, the acid form is practically non-toxic to Daphnia but the ethyl hexyl form is moderately toxic. As with fish, esters are more toxic than acid or amine table salt forms to freshwater aquatic invertebrates, with LC₅₀ values ranging from 25 to 643 mg ae/50 for the acid and amine common salt forms but 2.2 to 11.viii mg ae/50 for esters.³ The relative toxicities for acids and salts are slightly toxic to practically non-toxic, whereas the esters are moderately to slightly toxic.
• Marine invertebrate sensitivities are similar to aquatic invertebrates, with LC₅₀ values of 50-830 mg ae/L for acid and common salt forms and >0.092 to >66 mg ae/L for ester forms.³ The corresponding relative toxicity values are slightly toxic to practically non-toxic for the salts and acrid but highly toxic to practically non-toxic for the ester forms.
• Researchers have estimated a No Observed Issue Concentration (NOEC) of 16.ane mg ae/50 for the DEA ester and 79.0 mg ae/L for the acid form based on survival and reproduction for DEA and number of young produced for the acid class. The freshwater aquatic invertebrate NOEC for the BEE ester was estimated at 0.ii mg ae/L based on survival and reproduction.³
• two,4-D is marketed for controlling aquatic plants. Therefore, the lethal concentrations are reported as effective concentrations for killing half the target population (EC₅₀). Researchers estimated an EC₅₀ of 0.58 mg/L for duckweed (Lemna gibba). A variety of algal species exhibited LC_l values ranging betwixt 0.23 and greater than 30 mg/L for the ethyl hexyl form.¹ The EC_fifty for the dimethyl amine salt form against Selenastrum capricornutum was estimated at 51.two mg/L.^ane No effects were recorded for 19 genera of algae exposed to 2,4-D at concentrations of up to 222 mg/L.ⁱⁱ However, the ester forms were toxic to some algae at much lower concentrations.ⁱⁱ See the text box on EC_fifty .

  EC₅₀: The median effective concentration (EC₅₀) may exist reported for sublethal or ambiguously lethal effects. This measure is used in tests involving species such as aquatic invertebrates where death may exist difficult to determine. This term is also used if sublethal events are being monitored.

  Newman, M.C.; Unger, K.A. Fundamentals of Ecotoxicology; CRC Press, LLC.: Boca Raton, FL, 2003; p 178.

• A mesocosm report indicated that an unspecified form of 2,4-D practical at 0.117 mL/m² had no negative effects on species richness, biomass, or survival on algae and 25 species of aquatic animals, including frog larvae, salamanders, snails, and a range of other invertebrates.⁵³ Ninety-six-hour LC₅₀ concentrations for several species of amphibian larvae exceeded 100 mg/L for the amine common salt forms.² ii,4-D acrid, ii,four-D EHE, and 2,4-D DMA are considered practically non-toxic to amphibian larvae based on tests with Rana pipiens.³
• Bioavailability and uptake of 2,4-D by organisms are strongly influenced by pH, temperature, and other environmental factors.² The sensitivity of aquatic invertebrates to ii,4-D increases with temperature; concentrations below those associated with short-term toxic effects impaired reproduction when ambient temperature was elevated.² Although some aquatic invertebrates appear to sense and avoid ii,iv-D in the water, others practise not, fifty-fifty when exposed to lethal concentrations.ⁱⁱ Fish announced to avoid 2,iv-D in a dose-dependent manner until the onset of toxic effects.² Toxicity of two,four-D was increased when fish were simultaneously exposed to 2,4-D and carbaryl or picloram.²

Terrestrial Invertebrates

• LC_l values for 24-hour exposures in beloved bees (Apis mellifera) were estimated to exist 104 and 115 μg per bee. Researchers estimated the LD_l at greater than 10 μg/bee, so 2,four-D is considered practically non-toxic.³ Effects on bee longevity varied according to dose and 2,iv-D form.^two
• 2,four-D is not considered hazardous to beneficial insects due to its low insecticidal activity and an adequate rubber margin when products containing 2,4-D are used at recommended levels.^2,iii
• Carabid beetles (Carabidae) exposed to sand dosed with 1 g/grand² exhibited greater than 50% mortality after four days.²
• The calculated 48-hour LC_fifty concentration for earthworms (Lumbricus rubellus) exposed to filter paper treated with 2,4-D was 61.6 μg/cm.²²
• Effects of 2,four-D on soil microorganisms were species-dependent.²

Regulatory Guidelines:

• The reference dose (RfD) for ii,4-D is 0.01 mg/kg/day.⁵⁴ Meet the text box on Reference Dose (RfD).

  Reference Dose (RfD): The RfD is an estimate of the quantity of chemical that a person could exist exposed to every day for the rest of their life with no appreciable take chances of adverse health effects. The reference dose is typically measured in milligrams (mg) of chemical per kilogram (kg) of trunk weight per day.

  U.Southward. Ecology Protection Agency, Integrated Run a risk Information Arrangement, IRIS Glossary, 2009. https://www.epa.gov/iris/iris-glossary#r

• The U.Southward. EPA has classified 2,4-D as "Group D - not classifiable with regard to human carcinogenicity" in 2004.³ IARC had not assigned 2,4-D a cancer rating as of December 2007. However, the chlorophenoxy herbicides every bit a group were classified in Group 2B, meaning that they are considered to be mayhap carcinogenic to humans, by IARC in 1987.²⁹ See the text box on Cancer.
• The threshold limit value, or TLV, for ii,4-D is 10 mg/m³ for an viii-60 minutes fourth dimension weighted average exposure.⁵⁵ This limit is based on results of creature feeding experiments.⁴³ This same dose was selected by the Occupational Safety and Health Administration (OSHA) for the permissible exposure limit (PEL) for an 8-hr time weighted average exposure and past the National Institute for Occupational Safety and Wellness (NIOSH) for the recommended exposure limit (REL) for a 10-60 minutes workday and a 40-hour workweek.⁴³
• The MCL for 2,4-D in drinking water is 0.07 mg/L.⁵⁶ See the text box on Maximum Contaminant Level (MCL).

Appointment Reviewed: November 2008

Delight cite every bit: Gervais, J.; Luukinen, B.; Buhl, K.; Stone, D. 2008. ii,4-D Technical Fact Sheet; National Pesticide Information Middle, Oregon State Academy Extension Services. http://npic.orst.edu/factsheets/archive/2,4-DTech.html.

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Source: http://npic.orst.edu/factsheets/archive/2,4-DTech.html

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