---

The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

---

E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Ethion

Trade and Other Names: Trade names include Acithion, Aqua Ethion, Ethanox, Ethiol, Hylmox, Nialate, Rhodiacide, Rhodocide, RP-Thion, Tafethion, Vegfru Fosmite.

Regulatory Status: Ethion is a highly to moderately toxic compound in EPA toxicity class II - moderately toxic. Products containing this compound are General Use Pesticides (GUP), and labels for these products must bear the Signal Word WARNING.

Chemical Class: organophosphate

Introduction: Ethion is an organophosphate pesticide used to kill aphids, mites, scales, thrips, leafhoppers, maggots, and foliar feeding larvae. It may be used on a wide variety of food, fiber, and ornamental crops, including greenhouse crops, lawns, and turf. Ethion is often used on citrus and apples. It is mixed with oil and sprayed on dormant trees to kill eggs and scales. Ethion may also be used on cattle. It is available in dust, emulsifiable concentrate, emulsifiable solution, granular, and wettable powder formulations.

Formulation: It is available in dust, emulsifiable concentrate, emulsifiable solution, granular, and wettable powder formulations.

Toxicological Effects:

• Acute toxicity: Ethion is highly to moderately toxic by the oral route with reported oral LD50 values for pure ethion in rats of 208 mg/kg, and for technical ethion of 21 to 191 mg/kg [8,13]. Other reported oral LD50 values (for the technical product) are 40 mg/kg in mice and guinea pigs [13]. Ethion is moderately toxic via inhalation, with a reported 4-hour LC50 in rats of 0.864 mg/L [8]. It is highly to moderately toxic via the dermal route as well with a reported dermal LD50 of 62 mg/kg in rats (13) 915 mg/kg in guinea pigs, and 890 mg/kg in rabbits [62]. Acute effects are typical of organophosphate exposure and will vary according to the degree of exposure. Effects could include nausea, cramps, diarrhea, excessive salivation, blurred vision, headache, fatigue, tightness in chest, abnormal heart beat and breathing, loss of coordination, convulsions, coma, and death. Skin exposure may cause contact burns. Persons with respiratory ailments, recent exposure to cholinesterase inhibitors, impaired cholinesterase production, or with liver malfunction may be at increased risk from exposure to ethion. High environmental temperatures or exposure of ethion to visible or UV light may enhance its toxicity [2,8].
• Chronic toxicity: In a chronic toxicity study with rats fed 0.1, 0.2 or 2 mg/kg/day for 18 months, decreased cholinesterase levels occurred in the high-dose group. No other toxic effects were observed [62]. Repeated or prolonged exposure to organophosphates may result in the same effects as acute exposure, including the delayed symptoms. Other effects reported in workers repeatedly exposed include impaired memory and concentration, disorientation, severe depression, irritability, confusion, headache, speech difficulties, delayed reaction times, nightmares, sleepwalking, and drowsiness or insomnia. An influenza-like condition with headache, nausea, weakness, loss of appetite, and malaise has also been reported [2,8].
• Reproductive effects: A three-generation reproduction study with rats given dietary doses as high as 1.25 mg/kg/day did not show any ethion related reproductive effects [62,63]. This suggests that ethion does not cause reproductive effects.
• Teratogenic effects: When rats were given doses of 0.2, 0.6 or 2.5 mg/kg/day on days 6 to 15 of pregnancy, developmental effects were seen only in the highest dose tested. In fetuses of the high dose group, there was an increased incidence of delayed ossification of the pubic bones. When rabbits were given doses of 0.6, 2.4 or 9.6 mg/kg/day on days 6 to 18 of pregnancy, fetuses from the highest dose group exhibited an increased incidence of fused sternal bones [62]. Teratogenic effects observed in lab animals are not likely in humans under normal circumstances.
• Mutagenic effects: Assays on gene mutation, structural chromosomal aberration, and unscheduled DNA synthesis indicate that ethion is not mutagenic [62,63].
• Carcinogenic effects: Ethion was not carcinogenic in rats and mice [7]. There was no increase in the incidence of tumors in rats fed dietary doses as high as 2 mg/kg/day for 18 months. No evidence of carcinogenicity was observed in mice fed dietary doses of up to 1.2 mg/kg/day for 2 years [62].
• Organ toxicity: Ethion primarily affects the nervous system through cholinesterase inhibition, the blockage of an enzyme required for proper nerve functioning.

• Fate in humans and animals: Based on its similarity to other organophosphates, ethion is probably degraded in the same general way as other members of this class. These chemicals are rapidly metabolized and excreted via urine with a biological half-time of 1 or 2 days.

Ecological Effects:

• Effects on birds: Ethion is highly toxic to practically nontoxic to birds, depending on the species. Ethion is highly toxic to songbirds; e.g., LD50 in red-winged blackbirds is 45 mg/kg. It is moderately toxic to medium sized birds such as bobwhite quail (LD50 is 128.8 mg/kg) and starlings (LD50 is greater than 304 mg/kg). Ethion is practically nontoxic to larger upland game birds (ring-necked pheasant) and waterfowl (mallard duck). Ethion is persistent in the environment and may be stored in plant and animal tissues [62].
• Effects on aquatic organisms: Ethion is very highly toxic to freshwater and marine fish, and to freshwater invertebrates [8,63]. The 96-hour LC50 for ethion in rainbow trout is 0.5 mg/L [8]. The acute LC50 is 0.049 mg/L in Atlantic silversides, 0.210 mg/L in bluegill sunfish, and 0.72 mg/L in cutthroat trout and flathead minnows. The LD50 for freshwater invertebrates is 0.056 ug/L to 0.0077 mg/L, depending on the species, and 0.05 to 0.049 mg/L for marine and estuarine invertebrates. Ethion accumulates in the tissues of fish [16,62,63].
• Effects on other organisms: Ethion is practically nontoxic to honeybees. Its LD50 is 20.55 ug per bee [62,63].

Environmental Fate:

• Breakdown in soil and groundwater: Ethion is moderately to highly persistent. Under laboratory conditions, the soil half-life of ethion was 1.3 to 8 weeks, but in a greenhouse with an organic soil, it was more persistent, with half-lives of 16 to 49 weeks, depending on the degree of watering [12,19]. When used repeatedly, ethion residues in soil will increase from one year to the next [13]. Ethion adsorbs strongly to soil particles and it is nearly insoluble in water [12,19]. It is therefore unlikely to leach or contaminate groundwater [12]. In soil, ethion is subject to microbial degradation. It is resistant to hydrolysis, except in alkaline conditions (pH 9 or above) [12].
• Breakdown in water: Ethion is almost insoluble in water [13]. In open waters, it is likely to adsorb to suspended particles and bottom sediments. The persistence half-life of ethion varied from 4 to 22 weeks when tested in three different natural waters under laboratory conditions. It breaks down slowly in irrigation canal water (half-life = 26 days) [12]. Its hydrolysis half-lives at 25 C are 63, 58, 25 and 8.4 weeks at pH 5, 6, 7 and 8, respectively [12]. The half-life was day at pH 10 and 30 C. Microbial degradation of ethion may be insignificant in open waters. Volatilization be important only in shallow, rapidly moving streams. Photooxidation may occur in sunlight [12]. Bioconcentration of ethion may be significant (8).
• Breakdown in vegetation: No data are currently available.

Physical Properties:

• Appearance: Technical ethion is an odorless amber liquid [13].
• Chemical Name: O,O,O',O'-tetraethyl S,S'-methylene bis(phosphorodithioate) [13]
• CAS Number: 563-12-2
• Molecular Weight: 384.48
• Water Solubility: 1.10 mg/L [13]
• Solubility in Other Solvents: Soluble in most organic solvents [13]
• Melting Point: -15 to -12 C [13]
• Vapor Pressure: 0.2 mPa @ 25 C [13]
• Partition Coefficient: 5.073 [8]
• Adsorption Coefficient: 10,000 [19]

Exposure Guidelines:

• ADI: 0.002 mg/kg/day [38]
• MCL: Not Available
• RfD: 0.0005 mg/kg/day [53]
• PEL: Not Available
• HA: Not Available
• TLV: 0.4 mg/m3 (8-hour) (skin) [47]

Basic Manufacturer:

FMC Corporation
Agricultural Chemicals Group
1735 Market Street
Philadelphia, PA 19103

• Phone: 215-299-6661
• Emergency: 800-331-3148
  

References:

References for the information in this PIP can be found in Reference List Number 5

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.