---

The information in this profile may be out-of-date.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

Napropamide

Trade and Other Names: Trade names for products containing napropamide include Devrinol and R-7465. It may also be found in formulations with other pesticides such as monolinuron, nitralin, simazine, trifluralin, tefurthrin, and tebutam. It is compatible with many other herbicides and fungicides.

Regulatory Status: Napropamide is a slightly toxic compound in EPA toxicity class III. The Signal Word CAUTION is required on the label of products containing the compound. Napropamide is a General Use Pesticide (GUP).

Chemical Class: amide

Introduction: Napropamide is a selective systemic amide herbicide used to control a number of annual grasses and broad-leaved weeds. Napropamide is applied to soils where vegetables, fruit trees and bushes, vines, strawberries, sunflowers, tobacco, olives, and mint or other crops are grown. It is available in emulsifiable concentrate, wettable powder, granules, and suspension concentrates.

Formulation: It is available in emulsifiable concentrate, wettable powder, granules, and suspension concentrates.

Toxicological Effects:

• Acute toxicity: Napropamide is slightly to practically nontoxic by ingestion, with reported oral LD50 values for the technical product of over 5000 mg/kg in male rats and 4680 mg/kg in female rats [1,103]. It is slightly to practically nontoxic by skin exposure, with reported dermal LD50 values of greater than 4640 mg/kg in rabbits, and greater than 2000 mg/kg in guinea pigs. [1,103]. Data on eye and skin irritation are not available. No studies have evaluated the acute toxicity of the technical product (95% napropamide) through inhalation exposure, but several inhalation studies conducted on Devrinol 4F (43.2%napropamide) indicate that the 4-hour inhalation LC50 for this formulation is greater than 0.2 mg/L in rats [13]. This indicates that this formulation may be highly toxic by this route of exposure. Toxic effects from acute exposure in rats included diarrhea, excessive tearing and urination, depression, salivation, rapid weight loss, respiratory changes, decreased blood presure, and fluid in body cavities [13].
• Chronic toxicity: Rats fed napropamide at doses of up to 30 mg/kg/day for 13 weeks showed no significant effects [103]. At doses of 40 mg/kg/day over the same length of time, female rats experienced a reduction in uterine weight [104,105]. In a feeding study in dogs over 13 weeks, males experienced decreased liver weight and body weight, and some changes in blood chemistry at the highest dose tested, 100 mg/kg/day [104,105]. There were no tissue changes in either the rats or dogs at doses of up to 100 mg/kg/day [104,105].
• Reproductive effects: One study conducted over three successive generations of rats showed a decrease in body weight gain in the fetal pups at the 100 mg/kg/day dose [13]. There is not enough evidence to assess the potential of napropamide to cause reproductive effects.
• Teratogenic effects: Three separate tests with rats produced conflicting results, thus making any conclusion difficult to draw. One study indicated that the compound had no effects at doses over 400 mg/kg/day in pregnant rats or in their offspring [30,101]. However, two other studies showed incomplete formation of bone in the rats at doses as low as 25 mg/kg/day administered at critical times of pregnancy (organogenesis) [13].
• Mutagenic effects: Three tests of the mutagenicity of napropamide all produced negative (nonmutagenic) results [30]. These assays were conducted on bacterial cells and in mice. This evidence suggests that napropamide is not mutagenic.
• Carcinogenic effects: Two tests, each conducted over two years, revealed no cancer related changes in either rats or mice. The highest dose of napropamide in both of the studies was 100 mg/kg/day [30]. In both cases the only effects noted were decreases in body weight gains for both species. These data suggest that napropamide is not likely to be carcinogenic.
• Organ toxicity: Though numerous organ-related adverse effects have been noted after acute exposure to napropamide, few have been found after chronic exposure. Only decreases in uterine and liver weights have been observed in test animals.

• Fate in humans and animals: Elimination is very rapid following oral exposure to napropamide [103]. Generally, most (99%) of a single dose is excreted within 4 days [103].

Ecological Effects:

• Effects on birds: Napropamide is practically nontoxic to game birds. The compound has 5-day dietary LC50 values ranging from nearly 7200 ppm in the mallard duck to 5600 ppm in the bobwhite quail [1,104].
• Effects on aquatic organisms: The compound is slightly to moderately toxic to freshwater fish species. The LC50 for the compound ranges from 9 to 16 mg/L in rainbow trout and from 20 to 30 mg/L in bluegill sunfish [1]. The LC50 in goldfish is greater than 10 mg/L [1]. Napropamide appears to be slightly toxic to aquatic invertebrates; the reported 48-hour LC50 for the compound in Daphnia magna is 14.3 mg/L [1]. Tests with marine organisms indicate that the compound is slightly toxic (fiddler crab) to moderately toxic (pink shrimp and eastern oyster) to these species [104]. In one study over a 10-day period napropamide bioaccumulated in the edible portion of the fish to 50 times the water concentration. Most of the accumulation was eliminated within 24 hours in clean water [104]. This indicates that the compound is not likely to accumulate appreciably in the tissue of fish.
• Effects on other organisms: The reported oral LD50 for napropamide in bees is 121 ug/bee, indicating it is not toxic to this species [1].

Environmental Fate:

• Breakdown in soil and groundwater: Napropamide is moderately persistent in the soil environment, with reported field half-lives of 56 to 84 days [11]. A typical value for most situations is estimated to be 70 days [11]. It is rapidly lost by photodegradation near the soil surface after application, and may be slowly degraded by soil fungi and bacteria [8]. Little or no loss due to volatilization has been seen in field studies [8]. It is moderately bound to most soils, and is slightly soluble in water [1,11]. It therefore may pose a slight threat of contamination to groundwater in soils with high water tables, very low organic matter and clay content, high porosity, and high rainfall [48]. As of 1988, napropamide was not found in samples from 172 different wells across the country [8].
• Breakdown in water: In water, the compound is broken down very quickly. The half-life for napropamide may be as rapid as 7 minutes [104]. The breakdown in water is predominantly mediated by the action of sunlight (photolysis) [104].
• Breakdown in vegetation: Napropamide is typically absorbed through the roots and translocated throughout the plant in some species (e.g., tomato) but not others (e.g., corn) [1]. It effectively shuts down growth by inhibiting cell division (mitosis) in the shoot regions (meristems) [1]. Susceptibility is determined by rates of translocation to these regions and by the ability to detoxify the compound. In tolerant species, rapid breakdown to water-soluble compounds occurs [1].

Physical Properties:

• Appearance: Napropamide is a colorless crystal; the technical form is a brown solid [1].
• Chemical Name: (R,S)-N,N-diethyl-2-(1-naphthyloxy)propionamide [1]
• CAS Number: 15299-99-7
• Molecular Weight: 271.36
• Water Solubility: 73 mg/L @ 20 C [1]
• Solubility in Other Solvents: v.s. in acetone, ethanol, xylene, and hexane [1]
• Melting Point: 74.8-75.5 C [1]
• Vapor Pressure: 0.53 mPa @ 25 C [1]
• Partition Coefficient: 3.3617 @ 25 C [1]
• Adsorption Coefficient: 700 [11]

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: 0.1 mg/kg/day [13]
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Zeneca Ag Products
1800 Concord Pike
Wilmington, DE 19897

• Phone: 800-759-4500
• Emergency: 800-759-2500
  

References:

References for the information in this PIP can be found in Reference List Number 10

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.