Oryzalin

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

Do not contaminate any body of water by ... disposal of wastes.

Tolerances are established for residues of the herbicide oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) in or on the following raw agricultural commodities: almond, hulls 0.05 ppm; avocados 0.05 ppm; citrus fruits 0.05 ppm; fig 0.05 ppm; kiwifruit 0.05 ppm; nut, tree, group 0.05 ppm; olive 0.05 ppm; pistachio 0.05 ppm; pome fruits 0.05 ppm; pomegranates 0.05 ppm; small fruits 0.05 ppm; and stone fruits 0.05 ppm.

Tolerances with regional registration, as defined in 180.1(n), are established for residues of oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) in or on the following raw agricultural commodities: Guava 0.05 ppm; and Papayas 0.05 ppm.

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

Chemical goggles, coveralls, long-sleeved shirt and impermeable gloves.

LC50 Gammarus fasciatus 0.19 mg/l/96 hr @ 18 °C, mature (95% Confidense limit 0.14-0.26 mg/l) Static bioassay without aeration, pH 7.2-7.5, water hardness 40-50 mg/l as calcium carbonate and alkalinity of 30-35 mg/l.

LD50 Chicken oral >1000 mg/kg

LD50 Bobwhite quail oral >500 mg/kg

LC50 Bluegill sunfish 2.88 mg/l /Conditions of bioassay not specified/

LC50 Goldfish fingerlings >1.4 mg/l/96 hr /Conditions of bioassay not specified/

TERRESTRIAL FATE: Based on a classification scheme(1), a Koc value of 600(2), indicates that oryzalin is expected to have low mobility in soil(SRC). The moderately low to intermediate soil/water partitioning of oryzalin (Kd = 2, 5, 8, and 13; Koc = 600) indicates that substantial fractions of oryzalin could be transported via both dissolution in runoff water and adsorption to eroding soil(9). Volatilization of oryzalin from moist soil surfaces is not expected to be an important fate process given an estimated Henry's Law constant of 1.9X10-9 atm-cu m/mole(SRC), derived from its vapor pressure, 9.75X10-9 mm Hg(3), and water solubility, 2.5 mg/l(4). Oryzalin is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(3). Microbial degradation and photodecomposition contribute to the degradation of oryzalin in soil(5). The results of one biological screening study, which demonstrates the role of microorganisms, have shown that oryzalin degrades much slower in sterilized soil as compared to nonsterile soil(5). In laboratory studies using Weld loam soil, oryzalin degradation under aerobic conditions was slower, half-lives of 1.4 and 4.35 months, than under anaerobic conditions, half-life of 0.34 months(6). Sunlight exposure studies have shown that oryzalin photodecomposes when oryzalin (applied to soil surfaces) is exposed to sunlight(7,8), a 7 day loss of 26.2% being reported(9).

AQUATIC FATE: Based on a classification scheme(1), a Koc value of 600(2), indicates that oryzalin is expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3), based upon an estimated Henry's Law constant of 1.9X10-9 atm-cu m/mole(SRC), derived from its vapor pressure, 9.75X10-9 mm Hg(4), and water solubility, 2.5 mg/l(5). According to a classification scheme(6), a range of BCFs from 32-328(7,8), suggests the potential for bioconcentration in aquatic organisms is moderate-to-high(SRC). Using 14C-labeled oryzalin and a terrestrial aquatic laboratory model ecosystem, oryzalin BCF values of 50 and 328 were determined for fish (Gambusia affinis)and snails, respectively(8). The susceptibility of oryzalin to direct photolysis in water (half-life = 1.4 hours) should limit its persistence in clear shallow waters with low light attenuation(8). However, its resistance to abiotic hydrolysis coupled with only a moderate susceptibility to aerobic and anaerobic biodegradation indicate that it will be somewhat more persistent in receiving surface waters that are deeper, have high light attenuation, low microbiological activities and long hydrological resident times(8).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), oryzalin, which has a vapor pressure of 9.75X10-9 mm Hg at 25 °C, is expected to exist solely in the particulate phase in the ambient atmosphere. Particulate-phase oryzalin may be removed from the air by wet and dry deposition(SRC). Oryzalin absorbs light in the environmental UV spectrum, and has the potential for direct photolysis in the atmosphere(2).

Oryzalin

Endocrine

5 x 10 ^-2 mg/kg-day

The avg Koc value is 600, with ranges from 93 to 2700(1). According to a classification scheme(2), the avg Koc value suggests that oryzalin is expected to have low mobility in soil. Results of field, greenhouse and laboratory studies have shown that oryzalin does not leach appreciably in soil(3,4). In several tests, surface applied oryzalin typically remained in the upper 7.5 cm soil profile with only minor amounts reaching the 15 cm depth(3,4). Soil movement appears to decrease with decreases in the moisture content(3).

Harmful if swallowed, inhaled, or absorbed through the skin.

May cause skin sensitization reactions in certain individuals /Surflan A.S./

The International Chemical Workers Union requested an evaluation of dermatitis and reproductive system disorders among workers exposed to oryzalin, dichlorobenzidine, and benzidine at the Bofors-Nobel/Lakeway facility, Muskegon, Michigan. Exposure to dichlorobenzidine was measured from two personal breathing samples and the results ranged from not detectable to 6.5 ug/cu m. Area samples for dichlorobenzidine were also taken. Surface contamination samples revealed dichlorobenzidine on the packout locker room surfaces and inside the operator's personal protective equipment. Exposure to airborne oryzalin for six full shift workers ranged from not detectable to 130 ug/cu m, with a mean of 28 ug/cu m. Dinitrochlorobenzene was detected in air at 70 ug/cu m and on surfaces at 6 ug/100 sq cm. Workers exposed to oryzalin reported no adverse reproductive effects. Of 36 workers exposed to dinitrochlorobenzene, 19 had skin problems. Bladder cancer was documented in 10 workers wit a mean time from first exposure to benzidine to diagnosis of 13.3 yr. It was concluded that a potential hazard existed from dichlorobenzidine exposure.

AEROBIC: Microorganisms are believed to play a role in the degradation and disappearance of oryzalin from soil. No specific soil organism has been identified as responsible for the degradation(1). In 6-month incubation studies using a non-sterile and sterile (via propylene oxide treatment) sandy loam soil, oryzalin degraded much faster in non-sterile soil indicating that soil microorganisms actively participate in the degradation(2). In soil, radiolabeled-oryzalin exhibited an ave overall half-life of 2.1 months at 24 °C(3). The major degradate was 4-hydroxy-3,5-dinitro-benzenesulfonamide, which accounted for a maximum of 4.7% of the radioactivity(3). Eight other degradates were isolated, each accounting for < 2.4% of the applied radioactivity(3). The benzenesulfonamide ring remained intact in all of the identified metabolites(3). By the end of the experiment at 6 months, 63% of the applied radioactivity was nonextractable and 6% had been mineralized to carbon dioxide(3).

AEROBIC: In greenhouse studies using Drummer silty clay loam and Cisne silt loam soils, oryzalin was observed to have a persistence half-life ranging from 1.6 to 4.3 months(1). In laboratory studies using Weld loam soil, oryzalin had half-lives of 1.4 and 4.35 months at respective temperatures of 30 and 15 °C under aerobic conditions(2); under anaerobic conditions, the half-life fell to 0.34 months(2). In 1974 and 1975 Wisconsin field studies, oryzalin was observed to have an initial half-life of approximately 15 to 40 days(3). Presumably due to surface photodegradation, delaying the time between soil application and soil incorporation will increase oryzalin's degradation in soil(4); in one test, a 7 day delay reduced the oryzalin concn by nearly 20%(4). The US Dept of Agric's Pesticide Properties Database lists a soil half-life of 20 days for oryzalin(5).

ANAEROBIC: Radiolabeled-oryzalin degraded with a 10 day half-life when anaerobic conditions were established after 23 days of aerobic incubation at 28 °C in sandy loam soil(1). An initial half-life of 1.2 months was calculated for the first 2 months of the study and a 3 month half-life was calculated for the last 4 months of the study(1). The major degradates formed during the anaerobic incubation were several benzeneimidazoles with a reduced nitro group and smaller amounts of benzenesulfonamides with 1 or 2 nitro groups reducing to amines(1). Oryzalin will degrade more rapidly under reducing than under oxidizing conditions(1).

A BCF range of 32-328 has been reported for oryzalin(1,2). According to a classification scheme(3), these BCFs suggests the potential for bioconcentration in aquatic organisms is moderate-to-high(SRC). Using 14C-labeled oryzalin and a terrestrial aquatic laboratory model ecosystem, oryzalin BCF values of 50 and 328 were determined for fish (Gambusia affinis) and snails, respectively(1). Oryzalin was not highly concentrated in bluegill sunfish: having a BCF of 32 in edible tissue, 106 in nonedible tissue, 66 in whole fish(2). Within 24 hrs depuration period for bluegill sunfish, there was 79%, 81% and 81% loss of radioactivity in edible, nonedible and whole fish respectively(2). By day 14, there was a loss of 89%, 95% and 94% in edible, nonedible and whole fish respectively(3).

As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their future use. Under this pesticide reregistration program, EPA examines health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether they are eligible for reregistration. In addition, all pesticides must meet the new safety standard of the Food Quality Protection Act of 1996. Oryzalin is found on List A, which contains most food use pesticides and consists of the 194 chemical cases (or 350 individual active ingredients) for which EPA issued registration standards prior to FIFRA, as amended in 1988. Case No: 0186; Pesticide type: Herbicide; Registration Standard Date: 06/30/87; Case Status: RED Approved 09/94; OPP has made a decision that some/all uses of the pesticide are eligible for reregistration, as reflected in a Reregistration Eligibility Decision (RED) document.; Active ingredient (AI): Oryzalin; Data Call-in (DCI) Date(s): 02/27/91, 01/27/95; AI Status: OPP has completed a Reregistration Eligibility Decision (RED) document for the case/AI.

Tolerances are established for residues of the herbicide oryzalin (3,5-dinitro-N4,N4-dipropylsunfalimide) in or on the following raw agricultural commodities: almond, hulls; avocados; citrus fruits; fig; kiwifruit; nut, tree, group; olive; pistachio; pome fruits; pomegranates; small fruits; and stone fruits.

Tolerances with regional registration, as defined in 180.1(n), are established for residues of oryzalin (3,5-dinitro-N4,N4-dipropylsunfalimide) in or on the following raw agricultural commodities: Guava and Papayas.