CAS No. 27314-13-2

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Adverse Effects
US Food Tolerances

ACTIVITY: Herbicide (pyridazinone)

Note: Two breakdown products: Demethylnorflurazon (CAS No. 112748-69-3) and Desmethylnorflurazon (CAS No. 23576-24-1)

CAS Name: 4-chloro-5-(methylamino)-2-[3-(trifluoromethyl)phenyl]-3(2H)-pyridazinone


Adverse Effects:

Body Weight Decrease
Cancer: Possible Human Carcinogen - LIVER
Endocrine: Ovary
Endocrine: Thyroid
Endocrine: Uterus

Environmental Effects:

Groundwater Contaminant

Regulatory Information
(only comprehensive for the US)
US EPA Registered: Yes 
US EPA PC Code: 105801 
California Chemical Code 2019  
US Tolerances: CFR 180.356 
FDA LMS Code: 596 
US EPA Permit Date
and Registrant:
1974, Sandoz
European Commission: Not allowed to be used as an active ingredient after July 25, 2003. 
Registered use in
(includes only a limited list of countries)

Australia, New Zealand, South Africa, US


US Maximum Residue Levels permitted in food commodities
Permitted in or on 59 food commodities, including:
Alfalfa, Almond, Apple,
Apricot, Asparagus, Avocado, Blackberry, Blueberry, Cattle, Cherry, Citrus Fruit, , Cotton, Filbert, Goat, Grape, Grass,
Hog, Hop (fresh), Horse, Milk, Nectarine, Peach, Peanut, Pear, Pecan, Plum, Poultry, Raspberry, Sheep, Soybean, Walnut
Other Information
Molecular Formula: C12H9Cl F3 N3O 
Entry Year: 1971 
Inventing Company: Sandoz 
Manufacturers: Syngenta, (Sandoz), Novartis 
Other Names: Evital, Monometflurazone,
SAN 9789, Solicam, Zorial
Manufacture site: US:
Clariant Corp., Charlotte, North Carolina 28266
Of special interest:
PAN BAD ACTOR - Ground Water Contaminant  
Material Safety Data Sheets & Labels
Jan 23, 2006: Conservation Group Moves for Court Order Restricting Use of 66 Pesticides in Core Red-Legged Frog Habitat.
San Francisco, Calif. – The Center for Biological Diversity (CBD) in a legal motion today asked a U.S. District Court to protect the threatened California red-legged frog (Rana aurora draytonii) from 66 of the most toxic and persistent pesticides authorized for use in California, by creating pesticide-free buffer zones around the frog’s core habitat and by requiring consumer hazard warnings so that all Californians may learn how to protect frogs. [Norflurazon was one of the 66 pesticides.]
In response to a lawsuit filed by CBD against the U.S. Environmental Protection Agency (EPA) in April of 2002, the District Court found in September of 2005 that the EPA violated the Endangered Species Act (ESA) by registering pesticides for use without considering how they might impact the continued existence of the red-legged frog. The motion for “injunctive relief” delivered today asks the court to protect the frog from pesticides in or adjacent to aquatic frog habitat designated as core recovery areas, until the EPA completes a formal consultation with the U.S. Fish and Wildlife Service (USFWS) on the impacts of the pesticides on red-legged frogs, as required under the ESA... CBD is asking the Court to impose a three-year schedule for the EPA to determine whether the 66 pesticides may affect the red-legged frog and to complete formal consultations with USFWS to ensure the pesticides are not jeopardizing the frog or contributing to its decline. To minimize harm to frogs during the consultation process, the motion asks for an injunction on use of the pesticides around aquatic features and upland habitats within the frog’s core recovery areas, as designated by USFWS in the agency’s Recovery Plan for the California Red-legged Frog. This injunction would also apply buffer areas for terrestrial and aerial pesticide applications, affecting approximately 7 percent of the current range of the frog and less than 1 percent of the area of California. CBD is also requesting that the EPA conduct monitoring for pesticides in three of the recovery areas to determine whether the buffers are effectively protecting the frog, inform pesticide users about the injunction, and post point-of-sale notifications warning consumers about harmful effects these pesticides may have on the frog...

Oct 5, 2005 - Study finds herbicides from runoff in river. Agriculture largely to blame for carcinogens. By Kevin Lollar. (Florida).
The Caloosahatchee River is receiving an unhealthy dose of herbicides, including potential carcinogens, from upstream, a Naples chemist said Tuesday at Mote Marine Laboratory's fourth Charlotte Harbor Conference... The herbicides atrazine, bromacil, norflurazon and simazine might cause cancer in humans... "These herbicides are showing up in the water year after year," Hushon said. "Farmers use them to kill weeds and kill their crops at the end of the season. It's not a fluke. We see them every year."...

April 22, 2005. Pesticides appearing in Caloosahatchee River samples in Florida. By Eric Staats. Naples Daily News.
... the Conservancy and the Watershed Council cite tests that have detected atrazine, bromacil, metolachlor, norflurazon and simazine...
May 31, 2002 - US EPA TRED document (Tolerance Reassessment Progress and Risk Management Decision)
1996 - US EPA Registration Eligibility Decision (RED)  (201 pages)
1996 - R.E.D. FACTS. US EPA. (16 pages)
TOXNET profile from Hazardous Substances Data Bank 
March 22, 2001 - Summary of Toxicology Data. California EPA.
March 22, 2001 - California prohibits agricultural and outdoor industrial use of Norflurazon in areas that are specifically managed or designed to recharge ground water and inside canal and ditch banks. 
Norflurazon found in 9.5% of California Wells Californians for Alternatives to Toxics
US EPA IRIS for Norflurazon (Integrated Risk Information System). The animal studies used to determine risks were mainly performed in the 1970's. One was performed in 1983.
US Map of Pesticide Use - 1992-1995 
US Toxic Release Inventory: 1995-2001: Brief Summary 
Herbicide products - partial list 
One of 8 fluorinated pesticides used to cultivate grapes in Australia. 
November 26, 2002 - European Commission: Norflurazon is one of 320 pesticides to be withdrawn in July 2003. Some 320 substances used in plant protection products (PPPs) - including insecticides, fungicides and herbicides - are to be withdrawn from the market by 25 July 2003 as part of the European Commission's new approach to the evaluation of active substances in plant protection products. This aims to improve safeguards to ensure that all such products in use are safe for the environment and human health. Users, wholesalers and retailers of plant protection products will need to be aware of whether the products they use or sell are likely to be withdrawn, so as to prevent them being left with stocks of unusable material. Those concerned should contact their national authority to check the authorisation status for any particular product. The Regulation (ní 2076/2002 of 20 November 2002), with the list of the 320 substances, has now been published in the Offical Journal ..." Ref: MIDDAY EXPRESS. News from the Press and Communication Service's midday briefing. 
See also: 3-Trifluoromethyl aniline - used as an intermediate in the production of Norflurazon
October 2001 - Glossary of Pesticide Chemicals. A listing of pesticides subject to analysis of residues in foods and feeds by the US Food and Drug Administration.

Rationale for US EPA to add Norflurazon to the Toxic Release Inventory

Congestion of the liver, hepatocyte swelling and increased liver weights, and increase in colloid vacuole in the thyroid were observed in dogs fed 450 ppm (10.25 mg/kg/day) norflurazon for 6 months. The NOEL was 150 ppm (3.75 mg/kg/day). An oral RfD of 0.04 mg/ kg/day has been determined. Increased relative liver weight and hypertrophy of the thyroid with depletion of colloid were seen in rats fed 2,500 ppm (125 mg/kg/day) norflurazon for 90 days. The NOEL was 500 ppm (25 mg/kg/day). Hepatic hyperplasia and hypertrophy and increased relative liver weight were noted in a 28-day feeding study in rats. The LOEL was 1,000 ppm (50 mg/kg/day) and the NOEL was 500 ppm (25 mg/kg/ day). Increased relative liver weight and diffuse and smooth granular livers were seen in a 28-day feeding study in mice. The LOEL was 2,520 ppm (328 mg/kg/day) and the NOEL was 420 ppm (55 mg/kg/day). EPA believes that there is sufficient evidence for listing norflurazon on EPCRA section 313 pursuant to EPCRA section 313(d)(2)(B) based on the available hepatic and thyroid toxicity data.

Ref: USEPA/OPP. Support Document for the Addition of Chemicals from Federal Insecticide, Fungicide, Rodenticide Act (FIFRA) Active Ingredients to EPCRA Section 313. U. S. Environmental Protection Agency, Washington, DC (1993). As cited by US EPA in: Federal Register: January 12, 1994. Part IV. 40 CFR Part 372. Addition of Certain Chemicals; Toxic Chemical Release Reporting; Community Right-to-Know; Proposed Rule.

Norflurazon - which was on a low-priority sampling list in California because it was not anticipated to pollute groundwater - was found in groundwater by Florida which is more vigilant about water quality because the state is experiencing a water pollution crisis. California found norflurazon - the third most popular herbicide used on the state's roadsides - in 9.5% of the wells in 1997, the first time samples were taken.
Ref: Pathways of Exposure. Californians for Alternatives to Toxics.

US Federal Register

•• Note: Due to length, the following is a partial list. Click here to see full list of FR entries.

Published Date Docket Identification Number Details
Feb 10, 2005 OPP-2005-0025 Removal of Expired Time-limited Tolerances for Emergency Exemptions. FINAL RULE.
• 14. Norflurazon. Time-limited tolerances for Bermuda grass hay and forage are being removed from Sec. 180.356 because they expired on November 30, 2002.
July 30, 2003 OPP-2002-0327 US EPA's Pesticide Reregistration Performance Measures and Goals.
Norflurazon was one of 21 TREDS
(Tolerance Reassessment Progress and Interim Risk Management Decisions) completed by US EPA in Fiscal Year 2002.
-- EPA issues Reports on FFDCA Tolerance Reassessment Progress and Interim Risk Management Decisions, known as TREDs, for pesticides that require tolerance reassessment decisions under FFDCA, but do not require a reregistration eligibility decision at present because:
• The pesticide was first registered after November 1984 and is considered a ``new'' active ingredient, not subject to reregistration (e.g., fenarimol and primisulfuron-methyl in FY 2002);
• EPA completed a RED for the pesticide before FQPA was enacted (most FY 2002 TREDs are in this post-RED category); or
• The pesticide is not registered for use in the U.S. but tolerances are established that allow crops treated with the pesticide to be imported from other countries (e.g., mevinphos).
... As with IREDs, EPA will not take final action on pesticides subject to TREDs that are part of a cumulative group until cumulative risks have been considered for the group.
Sept 13, 2002 OPP-2002- 0121 EPA status of reregistration and tolerance reassessment.
June 11, 2002 OPP-2002-0096 Notice of availabilty of TRED document (Tolerance Reassessment Progress and Risk Management Decision).
... EPA did not perform a cumulative risk assessment as part of this reregistration review of norflurazon, because the Agency has not determined if there are any other chemical substances that have a mechanism of toxicity common with that of norflurazon. If EPA identifies other substances that share a common mechanism of toxicity with norflurazon, then a cumulative risk assessment will be conducted that includes norflurazon once the final framework EPA will use for conducting cumulative risk assessments is available. Further, EPA is in the process of developing criteria for characterizing and testing endocrine disrupting chemicals and plans to implement an Endocrine Disruptor Screening Program. Norflurazon will be reevaluated at that time and additional studies may be required.
Jan 30, 2002 OPP-181083 Request for Emergency Exemption from the Alabama Department of Agriculture and Industries. Proposal to make no more than one application of norflurazon manufactured by Syngenta Crop Protection, Inc. as Zorial Rapid 80, EPA Reg. No. 100-848, at a rate of 0.5 - 1.2 lb active ingredient/Acre (.6 - 1.5 lb product/Acre) by ground to 60,000 acres of bermuda grass meadows between February 1 and July 31, 2002.
Nov 14, 2001 OPP-181082

Pesticide Emergency Exemptions. EPA authorized use in:
-- Alabama: on bermudagrass to control annual grassy weeds; March 6, 2001 to July 31, 2001.
Georgia: on bermudagrass to control annual grassy weeds; March 6, 2001 to July 1, 2001.

•• Note: Due to length, the above is a partial list. Click here to see full list of FR entries.

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