      UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

                                                                        
                                                                        
            OFFICE OF     

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

Date:		10/24/06	

Subject:	Determination of Buffer Zones for AZM Applications 		

 

To:		Katie Hall, Chemical Review Manager

	Special Review and Reregistration Division (7508P)

		

From:		Seyed Tadayon, Chemist

		Health Effects Division

		Reregistration Branch 3 (7508P)

Thru:		Catherin Eiden, Branch Chief

Health Effects Division

		Reregistration Action Branch 3(7508P)

Pc Code:	058001

DP Barcode:	311132

Introduction: Application of pesticides to agricultural crops by a
variety of spraying techniques results in a portion of the material
drifting beyond the intended targeted areas and poses potential human
risk. The purpose of this memo is to estimate safe buffer  zones for
bystanders when applying AZM. 

	 

Background

One way of protecting bystanders from direct exposure to sprays is the
use of no-spray buffer zones. The magnitude of spray drift is largely
controlled by the physics of particle formation and aerosol
movement/deposition. 

HED used the AgDrift model for estimating drift deposition from various
types of equipment used for spraying AZM. A number of agrochemical
registrants (known as the Spray Drift Task Force) have developed the
model AgDrift. EPA has approved the model for determining off-site
movement of chemicals during spraying. The model estimates downwind
deposition following ground, orchard, and aerial applications of
pesticides. The ground and orchard modules are empirical in that they
are based on the results of studies of drift, but the aerial portions,
which are applicable to both agricultural and forestry landscapes, rely
on a theoretical function for particle movement and particle size
distributions for various types of nozzles. 

AZM Buffer Calculation for bystanders

Using the Agdrift model HED calculated the possible buffer zones needed
to protect children bystanders from exposures to AZM through spray
drift.  Children have the highest surface area per unit of body weight
therefore the buffer zone estimates in this assessment are conservative.
 In this assessment HED utilized toxicological endpoints from animal
studies to quantify risk at different buffer zone distances. The
toxicological end points used for this assessment were a NOAEL of 0.56
mg/kg/day for short-term dermal exposure and a NOAEL of 0.15 mg/kg/day
for incidental oral ingestion.  The Toxicological endpoints are
summarized in Table 1.  Inhalation exposure was not assessed because of
the low vapor pressure of AZM combined with the belief that droplets of
AZM are only minimally inhalable.

Table 1.  Toxicity Endpoints Used for Buffer Calculation for AZM
Application



Exposure Route/Scenario	

Study	

NOAEL	

Effect	

UF

Short-Term Dermal	Dermal absorption in rat	0.56 mg/kg/day	RBC ACHE	100

Incidental Oral Ingestion	1-year oral dog feeding study	0.15 mg/kg/day
RBC ACHE	100



Summary of Results

Exposures from aerial application, ground boom application and air-blast
application were assessed by using varying buffer zone distances.  One
clear outcome for aerial application was the relationship between
increased risk and decreased nozzle diameter, ie, the finer the spray
the higher the exposure and risk.  A similar relationship can be seen
with ground boom application, however, the risks are less due to the
fact that the sprays are directed toward the soil rather than into the
air, thereby limiting the higher airborne drift.  With the airblast
application, different risks are based on the density of the foliage,
with higher density foliage blocking the drift, and sparser density
foliage allowing drift to occur.  The MOEs are lower earlier in the
growing season, when foliage is less dense.  Buffer distance and risks
for AZM’s application methods are presented in Table 2. 

Table 2: Buffer Distance and Risk for Various Equipment used Applying
AZM 





	 





	Aerial (1.5 lb ai/A) 



	 





	Apple , Pear Crabapple



	 





	Spray quality (Fine)	Buffer (ft)	Dose 	MOE	Total MOE	 





	Dermal	100	0.11543	5	4	 





	Ingestion	100	0.00444	34

 





	Dermal 	1000	0.01213	46	40	 





	Ingestion	1000	0.00047	319

 





	Spray quality (Medium)	Buffer (ft)	Dose 

	 





	Dermal	100	0.04517	12	11	 





	Ingestion	100	0.00174	86

 





	Dermal 	1000	0.00341	164	144	 





	Ingestion	1000	0.00013	1154

 





	Spray quality (Coarse)	Buffer (ft)	Dose	MOE

 





	Dermal	100	0.00258	217	89	 





	Ingestion	100	0.00099	152

 





	Dermal 	1000	0.0016	350	307	 





	Ingestion	1000	0.00006	2500

 





	Groundboom application (0.75 lb ai/A)	Buffer (ft)	Dose 	MOE

 	Groundboom application (1.0 lb ai/A)	Buffer (ft)	Dose	MOE	Total MOE

Blueberry, Brussel sprouts, Parsley



	 	Nursery Syock





Spray quality (high/fine)



	 	Spray quality (high/fine)





Dermal	60	0.00869	64	56	 	Dermal	60	0.01159	48	42

Ingestion	60	0.00033	455

 	Ingestion	60	0.00045	333

	Dermal 	100	0.00584	96	84	 	Dermal 	100	0.00779	72	63

Ingestion	100	0.00022	682

 	Ingestion	100	0.0003	500

	Dermal	150	0.00411	136	119	 	Dermal	150	0.00548	102	89

Ingestion	150	0.00016	938

 	Ingestion	150	0.00021	714

	Spray quality (low/fine)	Buffer (ft)	Dose 	MOE

 	Spray quality (low/fine)	Buffer (ft)	Dose 	MOE

	Dermal	60	0.00324	173	152	 	Dermal	60	0.00433	129	113

Ingestion	60	0.00012	1250

 	Ingestion	60	0.00017	882

	Dermal 	100	0.0023	243	212	 	Dermal 	100	0.00306	183	160

Ingestion	100	0.00009	1667

 	Ingestion	100	0.00012	1250

	Dermal	150	0.0017	329	286	 	Dermal	150	0.00227	247	215

Ingestion	150	0.00007	2143

 	Ingestion	150	0.00009	1667

	Spray quality (Hi/med-coarse)	Buffer (ft)	Dose	MOE

 	Spray quality (Hi/med-coarse)	Buffer (ft)	Dose	MOE

	Dermal	60	0.00234	239	209	 	Dermal	60	0.00312	179	157

Ingestion	60	0.00009	1667

 	Ingestion	60	0.00012	1250

	Dermal 	100	0.00172	326	283	 	Dermal 	100	0.0023	243	212

Ingestion	100	0.00007	2143

 	Ingestion	100	0.00009	1667

	Dermal	150	0.00131	427	374	 	Dermal	150	0.00175	320	278

Injestion	150	0.00005	3000

 	Injestion	150	0.00007	2143

	Spray quality (low/med-coarse)	Buffer (ft)	Dose 	MOE

 	Spray quality (low/med-coarse)	Buffer (ft)	Dose 	MOE

	Dermal	60	0.00147	381	331	 	Dermal	60	0.00197	284	247

Ingestion	60	0.00006	2500

 	Ingestion	60	0.00008	1875

	Dermal 	100	0.0011	509	448	 	Dermal 	100	0.00148	378	329

Ingestion	100	0.00004	3750

 	Ingestion	100	0.00006	2500

	Dermal	150	0.00086	651	576	 	Dermal	150	0.00115	487	431

Ingestion	150	0.00003	5000

 	Ingestion	150	0.00004	3750

	Airblast application (1.5 lb ai/A)	Buffer (ft)	Dose	MOE

 	Airblast application (2.0 lb ai/A)	Buffer (ft)	Dose 	MOE

	Apple, Pear, Crabapple



	 	Almond, Pistachio, Walnut





Sparse



	 	Sparse





Dermal	60	0.02626	21	19	 	Dermal	60	0.035	16	14

Ingestion	60	0.00101	149

 	Ingestion	60	0.00135	111

	Dermal 	100	0.01178	48	42	 	Dermal 	100	0.01571	36	31

Ingestion	100	0.00045	333

 	Ingestion	100	0.0006	250

	Dermal	150	0.00569	98	86	 	Dermal	150	0.00759	74	65

Ingestion	150	0.00022	682

 	Ingestion	150	0.00029	517

	Dense	Buffer (ft)	Dose 	MOE

 	Dense	Buffer (ft)	Dose 	MOE

	Dermal	60	0.01442	39	34	 	Dermal	60	0.01923	29	25

Ingestion	60	0.00055	273

 	Ingestion	60	0.00074	203

	Dermal 	100	0.00859	65	57	 	Dermal 	100	0.01146	49	43

Ingestion	100	0.00033	455

 	Ingestion	100	0.00044	341

	Dermal	150	0.00056	1005	418	 	Dermal	150	0.00074	755	307

Ingestion	150	0.00021	714

 	Ingestion	150	0.00029	517

	Normal	Buffer (ft)	Dose 	MOE

 	Normal	Buffer (ft)	Dose



Dermal	60	0.00131	427	374	 	Dermal	60	0.00175	320	278

Ingestion	60	0.00005	3000

 	Ingestion	60	0.00007	2143

	Dermal 	100	0.00087	644	570	 	Dermal 	100	0.00117	479	424

Ingestion	100	0.00003	5000

 	Ingestion	100	0.00004	3750

	Dermal	150	0.00061	918	818	 	Dermal	150	0.00081	691	607

Ingestion	150	0.00002	7500

 	Ingestion	150	0.00003	5000

	

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