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acetochlor (Harness) NYSDEC Denial to Register Products 4/97

Mr. Michael S. O'Connor
Acetochlor Registration Partnership
c/o Zeneca Ag Products
1200 South 47th Street
Richmond, CA 94804-0024
Dear Mr. O'Connor:
Re:  Denial of the Applications to Register Pesticide Products Containing
     the New Active Ingredient Acetochlor:
     Harness Herbicide (EPA Reg. No. 524-473)
     Surpass EC Herbicide (EPA Reg. No. 10182-325)
The Department has completed its review of the applications submitted by 
Zeneca, Inc. and Monsanto Co. and the technical data packaae submitted by the 
Acetochlor Registration Partnership in support of the applications to register 
the referenced pesticide products containing the new active ingredient 
acetochlor.
Harness Herbicide (EPA Reg. No. 524-473) is an emulsifiable formulation for
preemergence control of annual grasses, broadleaf weeds and yellow nutsedge in 
field corn, production seed corn, silage corn, and popcorn.  Harness Herbicide 
is labeled for a single or 60/40 split preemergence application at 1.1-3.0 lb. 
active ingredient per acre with total application not to exceed 3.0 lb. active 
ingredient per acre per use season.
Surpass EC Herbicide (EPA Reg. No. 10182-325) is a combination of the
herbicide acetochlor and the antidote or safener dichlormid for preemergence 
control of certain grasses, broadleaf weeds and yellow nutsedge in field corn, 
production seed corn, silage corn, and popcorn.  Surpass EC Herbicide is 
labeled for a single or 67/33 split preemergence application at 1.2-3.0 lb. 
active ingredient per acre with total application not to exceed 3.0 lb. active 
ingredient per acre per use season.
Harness Herbicide and Surpass EC Herbicide product labeling bear the statement 
"Restricted Use Pesticide Due to Oncogenecity."  Acetochlor has the properties
of a compound that may contaminate groundwater and surface water and the 
labels of both Harness and Surpass contain Environmental Hazards statements to 
this effect.  The Use Restrictions section of the labeling prohibits the use 
of these products in certain soils with low organic matter content if the 
depth to groundwater is 30 feet or less.  Numerous other label statements also 
require measures aimed at reducing impacts to surface and groundwater.  The 
Department's review of acetochlor identified oncogenic effects, potential 
groundwater contamination resulting from degradates of acetochlor, and 
toxicity to nontarget aquatic plants due to acetochlor runoff to surface 
water.
Oncogenic effects were reported in chronic feeding studies in rats and mice. 
Male and female rats had a sign)ficant increase in nasal epithelium adenomas 
at the highest dose tested (79.6 mg/kg/day); nasal epithelium carcinomas were 
also reported in three high-dose animals.  A statistically sign)ficant 
positive trend for the incidence of thyroid follicular cell adenomas was 
reported in male and female rats; a pair-wise comparison of the high dose 
incidence with concurrent controls was statistically sign)ficant for this
tumor in female rats.
In addition, two rare tumor types were reported at the high dose in rats, 
benign chondroma of the femur and basal cell tumors of the stomach.  In mice, 
a statistically significant increase in the incidence of pulmonary adenomas in 
males and females, combined pulmonary adenomas/carcinomas in males and 
combined hepatocytic adenomas/carcinomas in males were reported at the highest 
dose tested (about 100 mg/kg/day).  Positive trends for pulmonary adenomas in 
males and combined pulmonary adenomas/carcinomas in males and females were 
also reported.  Acetochlor was positive in several genotoxicity assays and is 
structurally similar to other compounds that have caused tumors in laboratory 
animals (alachlor, butachlor, and metolachlor).  The USEPA classified 
acetochlor a B2 carcinogen (probable human carcinogen based on aufficient
evidence from animal studies and inadequate data from human epidemiologic 
studies) and calculated a cancer potency slope factor (Q1*) of 0.017 
(mg/kg/day)-1.
There are no chemical-specific federal or State drinking water/groundwater
standards for acetochlor.  Based on its chemical structure, acetochlor falls 
under the 50 microgram per liter (ug/L) New York State drinking water standard 
for "unspecified organic contaminants" (10 NYCRR Part 5 - Public Water 
Systems).  The conditions of federal registration do not currently require the 
monitoring of water for any acetochlor degradates.
However, the New York State drinking water standard for the sum of 
"unspecifiedorganic contaminants" (UOC's) and "principal organic contaminants" 
(POC's) is 100 ug/L.  Using the U.S.EPA Q1* of 0.017 (mg/kg/day)-1 and 6 NYCRR 
Part 702.4 procedures for deriving ambient water quality standards and 
guidelines based on oncogenic effects, the ambient water quality value 
associated with a one in a million increased lifetime cancer risk is 2.1 ug/L 
for acetochlor.
The Department conducted three leaching simulations using the LEACHM model.
Riverhead sandy loam and Howard gravelly loam soil profiles were modeled. 
Riverhead sandy loam is representative of the soil type found primarily on 
Long Island, although this soil type is also found in some upstate counties. 
Howard gravelly loam is the soil type most representative of upstate New York 
soil conditions.
The first run employed the following input parameters:
Riverhead sandy loam - 1% organic matter
Conventional tillage - 2.2 lb acetochlor/acre
Koc = 100 (reported range of 74-428)
Aerobic half-life = 12 days (reported range 8-12 days)
Acetochlor concentrations in leachate reach a maximum of 0.1 ppb.  The 
combined levels of the three degradates (oxanilic acid, sulfonic acid, and 
thioacetic acid sulfoxide) are modeled as high as 250 ppb.  This value exceeds 
the 100 ppb maximum allowable level for POC's and UOC's combined.
The second run employed the following input parameters:
Riverhead sandy loam - 1% organic matter
No-tillage - 3.0 lb acetochlor/acre
Koc = 100 (reported range of 74-428)
Aerobic half-life = 1Q days (reported range 8-12 days)
Acetochlor concentrations in leachate reach a maximum of 0.1 ppb.  The 
combined levels of the three degradates (oxanilic acid, sulfonic acid, and 
thioacetic acid sulfoxide) are modeled as high as 300 ppb.  This value exceeds 
the 100 ppb maximum allowable level for POC's and UOC's combined.
The third run employed the following input parameters:
Howard gravelly loam soil - 2.5% organic matter
Conventional tillage - 2.2 lb acetochlor/acre
Koc = 130 (reported range of 74-428)
Aerobic half-life = 30 days (reported range 14-36 days)
Acetochlor concentrations in leachate are modeled at less than 0.1 ppt.  The 
combined levels of the three degradates (oxanilic acid, sulfonic acid, and 
thioacetic acid sulfoxide) still exceed 100 ppb.
LEACHM modeling results indicate that the levels of acetochlor in leachate
(groundwater) will likely remain below applicable drinking water standards or 
trigger values. The level of degradates, however, have the potential to pose a 
sign)ficant threat to groundwater resources of New York State.
The ARP study entitled "State Ground Water Monitoring Program for Acetochlor
and Other Corn Herbicides - Part 2. 1995 Progress Report" generally 
corroborates the results of the LEACHM modeling and the assumption made that 
acetochlor should not be expected at levels exceeding the proposed New York 
State drinking water standard of 2.1 ppb.  This monitoring does not, however, 
address degradates.
Initial data from prospective groundwater studies appears to confirm the
LEACHM modeling.  In the two studies reported to the Department, a clay loam 
site in Ohio and a loamy sand site in Wisconsin, there have been no detections 
of acetochlor in groundwater and one isolated trace determination of 
acetochlor at each site.  On the other hand, the acetochlor metabolite, 
oxanilic acid, has been detected at levels up to 3.7 ppb in soil pore water in 
one well cluster at the Ohio site and low levels (<1.0 ppb) of this same 
metabolite were found in shallow lysimeters (three and six feet below ground 
surface) at the Wisconsin site.  Other metabolites/degradates are not included 
in the monitoring protocol.
Aquatox modeling conducted by the Department predicts estimated environmental
concentrations of acetochlor aufficient to cause toxicity to representative 
aquatic plants.  The model predicts estimated environmental concentrations 
resulting from a 2 cm/hour rain event of one hour duration falling on a ten-
acre treated field, which drains into a one-acre pond.  Based on moderate run 
off potential (Kow = 1001), runoffs of 0.5%, 1.5%, and 3% were estimated and 
environmental concentrations were determined for one-, three-, and six-foot 
ponds.  Runoff from the use of Harness) and Surpass will be toxic to aquatic 
plants at the single and split application rates at all pond depths.  Trigger 
values for Lemna gibba are exceeded by one to two orders of magnitude.  
Acetochlor in runoff water will also be toxic to aquatic invertebrates at all 
pond depths at runoff rates of 1.5% and 3%.  A terrestrial field dissipation 
half-life of 19 days and stability to aquatic hydrolysis and photolysis 
suggest that acetochlor will remain in the water column long enough to harm 
aquatic plants and invertebrates.
Harness and Surpass product labeling bear the statement "Acetochlor has
properties that may result in surface water contamination via dissolved runoff 
and runoff erosion.  Practices should be followed to minimize the potential 
for dissolved runoff and/or runoff erosion."  These statements may not 
adequately protect aquatic plants.  ARP surface drinking water monitoring 
program results for 1995 and 1996 corroborate these concerns.  Approximately 
30% of the samples contained detectable levels of acetochlor.
However, when the data is analyzed on a monthly basis, 34 to 48% of the 
samples taken in May contained detectable levels of acetochlor.  The monthly 
averages of 0.41 ppb and 0.77 ppb are two to three times greater than the 
Lemna gibba LOEL values, and spikes of acetochlor are twice the Lemna gibba 
EC50.  Fifty-four to 58% of the samples taken in June contained detectable 
levels of acetochlor.  The monthly averages of 0.18 ppb and 0.43 ppb are equal 
to or twice the Lemna gibba LOEL values.  Forty-four percent of the samples 
taken in July 1996 contained detectable levels of acetochlor.  The monthly
average of 0.22 ppb equals macrophyte LOEL values, and spikes are three times 
Lemna gibba LOEL values.  Of the samples collected in August 1996, 31% 
contained detectable levels of acetochlor.  Measured spikes of acetochlor are 
twice the Lemna gibba LOEL value.
The federal registration of acetochlor contains many conditions including the
requirement for specific reductions in the combined use of other corn 
herbicides (i.e., alachlor, atrazine, butylate, 2,4-D, EPTC, and metolachlor). 
No data were provided to demonstrate that use of Harness and Surpass will 
reduce the occurrence and concentrations of these com herbicides in drinking 
water, groundwater, and surface water.  A comparison of the toxicological and 
environmental fate properties of acetochlor versus those of the six corn 
herbicides shows that acetochlor has toxicological and environmental fate 
profiles comparable to, and in some cases worse than, those of the other 
compounds.  Acetochlor also has an application rate comparable to or greater 
than some of these compounds, suggesting that its use may not result in 
greatly reduced environmental loading.
Therefore, based on the identified risks and the lack of compelling benefits 
resulting from the proposed use of Harness Herbicide and Surpass EC Herbicide 
in New York State, the Department hereby denies your application to register 
the referenced products in New York State containing the new active ingredient 
acetochlor.
If you have any questions on this matter, please call Maureen Serafini, 
Supervisor of our Pesticide Product Registration Section, at (518) 457-7446.
Norman H. Nosenchuck, P.E.
Director
Division of Solid & Hazardous Materials
cc:  S. Adams - Monsanto Co.
     N. Kim/A. Grey - NYS Dept. Of Health
     N. Rudgers/R. Mungari - NYS Dept. of Ag. & Markets
     D. Rutz/W. Smith - Cornell PMEP