Fate and Management of Turfgrass Chemicals - American Chemical

Chapter 17

Hazard Evaluation and Management of Volatile and Dislodgeable Foliar Pesticide Residues following Application to Turfgrass 1

1

1

1

2

Downloaded by STONY BROOK UNIV SUNY on May 18, 2018 | https://pubs.acs.org Publication Date: December 29, 1999 | doi: 10.1021/bk-2000-0743.ch017

J. Marshall Clark , G. R. Roy , J. J. Doherty , A. S. Curtis , and R. J. Cooper 1

MassachusettsPesticide Analysis Laboratory, Environmental Science Program, University of Massachusetts, Amherst, MA 01003 Department of Crop Science, North Carolina State University, Raleigh, NC 27695 2

Volatilization can be a major route of pesticide loss following application to turfgrass. Consequently, a significant proportion of applied pesticides may be available for human exposure via volatile and dislodgeable foliar residues. Our research has established that there are volatile and dislodgeable residues available for golfer exposure following pesticide application to turfgrass and not all of these exposures can be deemed completely safe using the USEPA Hazard Quotient assessment. Of the 14 pesticides examined, 10 never resulted in an inhalation exposure situation that had a Hazard Quotient greater than 1.0. Five never resulted in a dermal exposure situation that resulted in a Hazard Quotient greater than 1.0 and after the first day following application, 9 had Hazard Quotients less that 1.0. Application of ethoprop, isazofos, diazinon and isofenphos, however, did result in Hazard Quotients greater than 1.0 over a period of 3 days post-application and hence the safety of exposure to these organophosphorous insecticides is less certain. We have evaluated the practical use of spray tank adjuvants, irrigation and the role of thatch accumulation on the dissipation of volatile and dislodgeable residues as means to mitigate the exposure potential of the organophosphorous insecticides that have high vapor pressures and inherent high toxicity. To date, the use of adjuvants and thatch management (aeration, dethatching) have not resulted in the attenuation of the exposure potential of these insecticides. However, the managed application of these insecticides in the combined presence of adjuvants and/or with post-application irrigation may hold some promise.

294

© 2000

American Chemical Society

Clark and Kenna; Fate and Management of Turfgrass Chemicals ACS Symposium Series; American Chemical Society: Washington, DC, 1999.


295 Volatilization may be defined as the loss of chemicals from surfaces in the vapor phase with the subsequent movement into the atmosphere (1). Post-application vaporization of pesticide residues was reported as early as 1946 (2) and numerous studies since then have established volatilization as a major avenue of pesticide loss following application (3). While pesticide volatilization following soil application has been fairly well documented, volatilization from plant canopies has been studied far less (4). A dense perennial ground cover, such as turfgrass, is quite different from a plowed field or field crop planting and is likely to provide a unique environment for volatilization. The high surface area associated with the dense turfgrass blades and the thatch layer, which retards the downward leaching of pesticides, is likely to result in a significant increase in volatile and dislodgeable pesticide residues (5, 6). Understanding the nature and magnitude of volatilization and dislodgeable foliar residues is important not only because of its impact on pesticide dissipation but also because of concerns regarding pesticide efficacy and human exposure via inhalation and dermal penetration. Unfortunately, research evaluating pesticide volatilization and dislodgeable foliar residues from turfgrass has been quite limited. Volatilization of pesticide residues from plants under field conditions often exhibit marked diurnal fluctuations with maximum loss occurring at approximately solar noon (7-9). This diurnal variation is driven primarily by solar heating. During mid-afternoon, solar heating is at a maximum resulting in elevated surface temperatures and increased atmospheric turbulence. Prior to sunrise and after sunset, however, there is little insolation to elevate surface temperatures, thus resulting in minimal volatility during these periods (5). Loss of pesticides by volatilization from foliage typically follows a diphasic decline with an initial rapid loss for approximately 1 week, followed by a period of much slower volatile loss (10, 9). The slower rate of volatile loss typically observed after the first week may be explained by two hypotheses (3). The first suggests that the remaining residues are less available because they lie deeper within the canopy and are trapped in irregular areas of leaves, stems and leaf-stem junctions. The second suggests that the latter residues are lost at a reduced rate because they are more strongly adsorbed or have penetrated the leaf surface. Both mechanisms contribute to volatile loss and the availability of dislodgeable foliar residues but the relative importance of each factor has not been determined (5). While the benefits of pesticides in maintaining golf courses are clear, pesticide use also raises serious concerns regarding potential environmental pollution, human exposure risks and adverse impacts on wildlife. Substantial research has focused on assessing exposure of pesticide applicators (11) and harvesters reentering pesticidetreated crops (12). However, there is little research assessing golfer exposure to pesticides applied to golf course turfgrass. During the golfing season, courses usually are open every day during the week, leaving little time between pesticide application and reentry into the treated area. Inhalation of volatile pesticides may be of toxicological concern given the high susceptibility of the human lung to airborne toxins, particularly those associated with



296 aerosols. In addition, it has been shown frequently that dermal exposure of agricultural workers is related to the amount of pesticide present as dislodgeable foliar residues (13). The hands, arms and legs of golfers are often unprotected during play. The hands are likely the main route of dermal exposure since they are usually unprotected and are involved in a number of repetitive tasks that result in direct exposure to turf (e.g., picking up golf balls, repairing ball marks on greens, replacing divots in the fairway, cleaning club heads, etc). Thus, the potential for significant exposure to pesticides applied to golf courses certainly exists. Because of the increasing environmental concern about pesticide use on golf courses and to the uncertainty of the extent of human exposure, we have conducted research for the past six years to develop means to assess the extent of pesticide volatilization and the availability of dislodgeable foliar residues following application to turfgrass. This chapter summarizes the exposure situations that we found, a hazard assessment of these exposures and preliminary findings on the effectiveness of selected processes to attenuate the exposure situations from pesticides of highest concern. Small-Plot Techniques for Measuring Airborne and Dislodgeable Pesticide Residues following Application to Turfgrass The volatile loss and the availability of dislodgeable foliar residues following application of pesticides to turfgrass has been examined using two small-plot techniques: The Field Chamber Method and the Theoretical Profile Shape Method. Field Chamber Method. The initial experiments that first examined the volatile and foliar loss of pesticides following application to turfgrass were described in a series of papers co-authored by J J . Jenkins and R.J. Cooper (14-16). Airborne and dislodgeable residues were determined following application of the dinitroaniline herbicide pendimethalin (i\T-(l-ethylpropyl)-2,6-dinitro-3,4-xylidine) to Kentucky bluegrass. In the first technique, airborne residues were measured using small field chambers consisting of 19 L Pyrex bottles without bottoms and fitted with Teflon cartridges containing XAD-4 polymeric polymer resin. Dislogeable foliar residues were determined from turfgrass plugs in which the grass blades were separated from soil and thatch and then extracted with methanol. The focus of this initial research was to determine what relationship, i f any, exists between dislodgeable foliar residues and pesticide volatility. If such a relationship exists, a mathematical model could be developed to estimate pesticide flux using only measurements of dislodgeable foliar residues, thereby eliminating the logistical and conceptual problems associated with estimating volatile loss using traditional micrometeorological or laboratory chamber methods. Also, the relationships between volatile loss and the physical parameters of temperature/solar radiation and windspeed could be investigated in a controlled and replicated fashion. These studies found that it was possible to estimate total daily flux based on the diurnal pattern of volatility by making single flux measurements during the period of peak volatility (1300-1500 hrs). These authors concluded that there was a relationship between volatile loss and dislodgeable foliar residues as both flux and



297 dislodgeable foliar residues exhibited similar biphasal patterns of decline over the course of the study. However, the measured values did not correlated well, suggesting that the relationship was more complicated than initially thought. While the field chambers allowed the examination of what impacts different variables might play in the attenuation of volatile and dislodgeable residues, the modification of the chamber environment with regard to temperature and windspeed made it unclear whether the measured values of "chamber flux" actually reflected what was happening outside the chamber. It was concluded that the effects of increased temperature and decreased windspeed in the chambers were probably offsetting each other in this case, but that the chamber technique itself could not reasonably be expected to reflect environmental volatility in all cases. As such, the field chamber technique is not appropriate for studies that require an accurate determination of ambient pesticide air concentration (e.g. exposure studies) as opposed to an estimate of pesticide flux. Theoretical Profile Shape Method. A second group of experiments was conducted to compare flux rates from the chambers with those obtained from an ambient method, the Theoretical Profile Shape (TPS) method, which is based on the trajectory-simulation (TS) model of Wilson et al., (17). Details of the TPS method and the TS model are given in Wilson et al., (17, 18) and Majewski et a l , (19-21). Briefly, the TPS method employs the TS model, a 2-dimensional dispersion model, to estimate source strength [F (0)] from a single measurement within the vertical profile of the horizontal flux at the center of a circular plot. Where: z

F (0) = ( u c ) z

F (0) (uc) Φ

mcasured

/O 2

z

measured

= source strength determined as the actual vertical flux rate (mg/m /hr) = product of the measured windspeed and air concentration = normalized horizontal flux predicted by the TS model.

The measurement height (ZINST) is chosen based upon the plot radius, roughness length (zo), and the Monin-Obukhov atmospheric stability length (L). In these experiments, the airborne residue and windspeed were measured at a height ZINST of 73 cm chosen according to a plot radius of 20 meters and a surface roughness length of 0.2 cm. Pendimethalin airborne residues were collected with a Staplex TF1A high volume air sampler onto XAD-4 polymeric resin. Dislodgeable foliar residues were determined as described for the field chamber experiments. Previous work by Majewski and co-workers (19-21) has determined the TPS method to be comparable to other micrometeorological techniques for estimating evaporative flux of a number of pesticides from soil. In the case of pesticide application to turfgrass, the two small-plot techniques gave comparable results for pendimethalin flux. The important difference between the two methods is that while the TPS method has inherent error associated with the mathematical TS model used to calculate flux, its results are based on actual air concentrations, whereas the levels measured in the field chambers reflect an artificial environment and ultimately requires verification with an ambient technique. Additionally, the TPS method provides an


298 accurate measure of pesticide air concentration, which can be used for purposes other than estimating flux, such as exposure estimates and hazard evaluations. The TPS method, likewise, uses plots small enough to allow for replication, which is a major limitation in the evaluation of information gathered using aerodynamic-based methods.


Fate of Volatile and Dislodgeable Residues following Pesticide Application to Turfgrass and Implications for Human Exposure Estimation of Golfer Exposure and Hazard Assessment. We recently have addressed two significant concerns of the turfgrass industry (5, 6). First, we were interested in establishing the potential and the routes for golfer exposure to pesticides applied to turfgrass. Second, we wanted to prioritize those pesticides that may be of most concern following exposure. Using a small circular plot design is conjunction with the TPS method, airborne pesticide concentrations were determined and used to estimate the inhalation and dermal exposure situations for golfers using the U S E P A Hazard Quotient determination. A n average daily inhaled dose of pesticide for a 70 kg adult playing a 4-hr round of golf was estimated by Eq. 1. C x R x 4 h r / 7 0 k g = Di

[Eq. 1]

where C = measured air concentration of pesticide determined by high-volume air sampling fag m" ), R = adult breathing rate during moderated activity (2.5 m h* , 22), and Dj = daily inhaled dose of pesticide fag kg* ). The estimated inhaled dose (DO is divided by a chronic reference dose (Rfd, μ§ kg" d" , 23) resulting in the Inhalation Hazard Quotient (D* / Rfd = IHQ). Similarly, an average daily dermal dose was calculated using Eq. 2. 3

3

1

1

1

1

1

S χ Ρ / 70 kg χ 1000 μg m g = D

[Eq. 2]

d

where S = calculated dermal exposure (mg). S is determined by multiplying the dislodgeable foliar residues determined from a cheesecloth wipe (24) by a dermal transfer coefficient of 5 χ 10 cm h" (13), Ρ = dermal permeability (0.1, U S E P A default value, 25) and D = daily dermal dose of pesticide fag kg" ). The estimated dermal dose (Dd) is divided by the chronic Rfd resulting in the Dermal Hazard Quotient (D / Rfd = DHQ). Chronic Rfds were determined from daily doses shown to cause no observable effects on laboratory animals over their lifetime (NOELs) and then divided by safety factors of 10 to 10 000 depending on the completeness of the toxicological data set (23). Thus, Rfds are deemed to be safe doses that can be received over a lifetime without causing adverse effect. From this, HQs less than or equal to 1.0 indicate that the residues present are at concentrations below those that could cause adverse effects in humans. A HQ value greater than 1.0 does not necessarily infer the residues levels will cause adverse effects, but rather that the absence of adverse effects is less certain. 3

1

1

d

d



299 Hazard Assessment following Turfgrass Pesticide Applications. Using the above format, four pesticides were initially examined: Two insecticides, isazofos (0-5chloro-1 -isopropyl-//-1,2,4-triazol-3-yl 0, 0-diethyl phosphorothioate) and trichlorfon (dimethyl 2,2,2-trichloro-l-hydroxyethylphosphonate); a herbicide, M C P P (meoprop, (/tS)-2-(4-chloro-o-tolyloxy) propionic acid); and a fongicide, triadimefon (l-(4-chlorophenoxy)-3,3-dimethyl-l(l/f-l,2,4-triazol-l-yl) butanone). The hydrolytic degradative product of trichlorfon, DDVP (2,2-dichlorovinyl dimethyl phosphate), was also determined. The results of these experiment are summarized in Tables I and Π. As indicated in Tables ΠΙ and IV, only the application of isazofos resulted in both IHQs and DHQs greater than 1.0 over the course of this study. Additionally, the hydrolytic degradative product of trichlorfon, DDVP, also resulted in a D H Q value greater than 1.0 (4.6, Table IV) but this only occurred in the combination with 1.3 cm of post-application irrigation. Using the USEPA Hazard Quotient criteria, it is apparent that exposure situations exist following application of pesticides to turfgrass, which cannot be deemed completely safe. Furthermore, the pesticides of most concern appear to be insecticides that have inherently high vapor pressure (high volatility) and relatively high inherent toxicity (low Rfds). To validate these findings, a larger study was conducted that included 13 pesticides (plus DDVP) used extensively on turfgrass, which varied widely in terms of their vapor pressure, water solubility and inherent toxicity (Table V). Volatile and dislodgeable foliar residues were determined from small circular turfgrass plots and used to estimated M Q and DHQ values exactly as described in the original studies (5, 6). For pesticide applications, the boom sprayer used in the initial studies was replaced with a Rogers Wind Foil® (Model GF 1500) equipped with a rubber skirt to retard spray drift. Methods for extraction and instrumental analysis of additional pesticides are given in Clark et al., (26). Post-application irrigation was reduced from 1.3 cm to 0.63 cm in this expanded study. Of the 14 pesticides examined, only 3 (ethoprop, diazinon and isazofos) resulted in volatile residues at sufficiently high enough concentrations to produce IHQs greater than 1.0 over the entire time course of this study (Table VI). As in our initial study, all 3 pesticides were organophosphorous insecticides that have high vapor pressures (high volatility) and low Rfds (high inherent toxicity). As indicated in Table VII, 7 pesticides resulted in dislodgeable foliar residues at sufficiently high enough concentrations to produce DHQs greater than 1.0. Except for bendiocarb (a carbamate), all the rest were organophosphorous insecticides. Only ethoprop, isazofos, diazinon and isofenphos produced DHQs that exceeded 1.0 in the intervals beyond the first 24 hr period following application. Trichlorfon, chlorpyrifos and bendiocarb had DHQs only slightly above 1.0 and these fell below 1.0 after the first day following application. These results are consistent with our original findings and substantiate that there are exposure situations involving volatile and dislodgeable foliar residues following the application of selective pesticides (organophosphorous insecticides) to turfgrass that cannot be deemed completely safe using the U S E P A H Q criteria. Additionally, increased hazard appears to be well correlated with pesticides that have high vapor pressures and low Rfd values and these characteristics


300


Table I. Summary of volatile and dislodgeable residues following triadimefon and M C P P application to turfgrass.

1. Less than 8% of applied triadimefon and less than 1% of applied M C P P were lost as measured volatile residues. 2. Nearly all of triadimefon's measured volatile residues were lost within the first two weeks following application. 3. Diurnal patterns of triadimefon volatility were observed. When surface temperature and solar radiation were greatest, volatile loss reached a maximum. 4. Dislodgeable residues of triadimefon and MCPP dissipated over time. By Day 5 post-application, dislodgeable residues of triadimefon and M C P P were less than 0.1% of applied compound. 5. Calculated HQs for triadimefon and MCPP from volatile and dislodgeable residues were below 1.0 for the entire 15-d experimental period. 6. Application of triadimefon and MCPP to turfgrass is not likely to result in a health hazard to golfers via volatile and dislodgeable residues. This reduced health hazard was due primarily to the low vapor pressures and relatively high Rfds associated with these two pesticides. 7. The vapor pressure, irrigation practices, water solubility and toxicity of a pesticide should be reviewed before application to golf courses.



301

Table Π. Summary of volatile and dislodgeable residues following trichlorfon and isazofos application to turfgrass.

1. A l l insecticide applications resulted in less than 13% of applied compound being lost as measured volatile residues: trichlorfon/DDVP (12.7%), with irrigation (11.6%), isazofos (11.4%). 2. The large majority of detectable volatile residues were lost within the first week following application. 3. Diurnal patterns of volatility were observed. When surface temperature and solar radiation were greatest, volatile loss reached a maximum. 4. When irrigation followed application, volatile and dislodgeable residues increased on Days 2 and 3 compared to those residues on Day 1. 5. Irrigation enhanced the transformation of trichlorfon to D D V P , a more toxic insecticide, with maximum residues apparent at Days 2 and 3 post-application. 6. Isazofos volatile residues resulted in a calculated IHQ greater than 1 through Day 3 post-application. 7. D D V P and isazofos dislodgeable residues resulted in a DHQ greater than 1 through Days 2 and 3 following application.


302

Table III.

Maximum air concentrations, doses, and inhalation hazard quotients


(IHQ).

Maximum Air Insecticide

Concentration-

Hazard D

o

s

e

>

Quotient

3

fogkg )

1.5

0.2

125

0.002

1.5

0.2

125

0.002

0.9 0.2

0.1 0.03

0.5 0.5

0.2 0.1

1.8 0.9

0.3 0.1

0.5 0.5

0.6 0.2

0.6

0.09

0.02

4.5

0.2

0.03

0.02

1.5

fogm )

1

Μ

1

1

Gig kg" * )

(IHQ)

Trichlorfon without irrigation Day 3 with irrigation (1.3 cm) Day 2 DDVP without irrigation Day 3 Day 5 with irrigation (1.3 cm) Day 2 Day 3 Isazofos with irrigation (1.3 cm) Day 2 Day 3

* Maximum air concentration occuring after application and irrigation if applicable. Office of Pesticide Programs Reference Dose Tracking Report, January 1993. Hazard Quotient = Dose/Rfd.

b

c

(Reproduced with permission from ref. 5, copyright 1996, Crop Science).


6

303


Table IV. Maximum dermal exposures, doses, and dermal hazard quotients (DHQ).

Maximum Insecticide

Exposure

(mg)

1

Hazard Dose

1

fcgkg )

Rfd

b

l

Quotient

1

fcgkg d' )

(DHQ)

Trichlorfon without irrigation 3 h post-application

37

53

125

0.4

5.5

7.9

125

0.1

0.0

0.0

0.5

0.1

Day 2

1.6

2.3

0.5

4.6

Isazofos with irrigation (1.3 cm) Day 2

0.2

0.34

0.02

17.1

with irrigation (1.3 cm) Day 2 DDVP without irrigation 3 h post-application with irrigation (1.3. cm)

a

b

c

Estimated fermai exposure after application and irrigation if applicable using the model of Zweig et al., (1985). Office of Pesticide Programs Reference Dose Tracking Report, January 1993. Hazard Quotient = Dose/Rfd. (Reproduced with permission from ref. 5, copyright 1996, Crop Science).


0

304

Table V. Physical and toxicological properties of turfgrass pesticides.

Molecular Weight*

Pesticides

Vapor Pressure * (mmHg)

Water Solubility "(ppnt)

NOEL (mg/kg/day)

Uncertainty Factor

OPPRfd (mg/kg/day)

b

b

b


Insecticides Organophosphorous 221.0 242.3 304.4 313.7 350.6 257.4 345.4

1.6 χ 10" 3.5 x1ο* 9.0 χ 10* 5.6 χ 10* 2.0xl03.8 χ 10* 3.3 χ 10*

8000 750 60 168 1.4 120000 18

0.05 0.015 0.009 nd 0.03 nd 0.05

100 1000 100 100 10 100 100

0.0005 0.000015 0.00009 0.00002 0.003 0.002 0.0005

223.2 201.2

3.4 χ 10* 3.1 χ 10*

280 120

0.5 1.43

100 100

0.005 0.014

434.3

2.0 xlO*

0.002

2.5

100

0.025

265.9

5.7x10''

0.6

1.5

100

0.015

Propiconizole

342.2

4.2 χ 10*

7

100

1.25

100

0.0125

ThiophanateMethyl

342.4

7.1X10*

8

1.0 χ 10" mm Hg), intermediate (vapor pressures between 1.0 χ 10" mm Hg and 1.0 χ 10" mm Hg), and low (vapor pressures < 1.0 χ 10" mm Hg) vapor groups. 5


5

7

7

Vapor

Pesticide

b

IHQs

Pressure (mmHg)

OPP Rfd (mg/kg/day)

Day 1

Day 2

Day 3

0.06 50 3.3 8.6 0.09

0.04 26 2.4 6.7 0.1

0.02 1.2 1.2 3.4 0.04

0.02 0.02 n/d 0.001 n/d 0.0005

0.004 0.002 0.02 0.001 n/d 0.0001

0.004 0.002 n/d 0.0003 n/d 0.00004

n/d n/d n/d

n/d n/d n/d

n/d n/d n/d

High V.P DDVP Ethoprop Diazinon Isazofos Chlorpyrifos

1.6 xlO"

2

5.0x10*

4

1.5x10*

3.5X10" s

9.0 x10 5.6 x10 2.0 x 1 0

s

s

9.0 x10 2.0 x10 3.0 xlO"

s

s

3

intermediate V.P. Trichlorofon Bendiocarb Isofenphos Chlorothalonil Propiconizole Carbaryl

6

3.8 χ 10* 3.4Χ10·

6

6

3.3 χ 10* 5.7 x l O ' 4.2 χ 10* 3.1 χ 10"

7

3

2.0 χ 10' 5.0 x l O 5.0 xlO" 1.5 xlO'

3 4

3

7

1.25X10

6

1.4 xlO'

8

8.0 x l O 6.1 xlO' 2.5 χ 10"

2

4

.ow V.P. Thiophanate-Methyl Iprodione Cyfluthrin

a

b

c

7.1 χ 10" 3.8 χ 10" 2.0 x l O '

9

9

2 2

2

The IHQs reported are the maximum daily IHQ measured, all of which occurred during the 11:00 a.m. to 3:00 p.m. sampling period. A l l pesticides were watered in following application using 0.63 cm post-application irrigation. n/d = not detected.


306


Table VII. Dermal hazard quotients (DHQs) for turfgrass pesticides listed with increasing Rfds from top to bottom through Day 3 post application.

Day 1 (DHQs)

Day 2 (DHQs)

Day 3 (DHQs)

Pesticide "

(mg/kg/day)

5 Hours

8 Hours

12:00 p.m.

12:00 p.m.

Ethoprop

0.000015

190

156

26

39

Isazofos

0.00002

135

112

18

24

Diazinon

0.00009

32

25

4.6

5.7

0.0005

5.7

5.7

1.1

Rfd

Isofenphos

1.1 b

n/d

DDVP

0.0005

0.3

0.3

n/d

Trichlorofon

0.002

0.8

1.1

0.9

0.5

1.8

0.3

0.4 0.09

0.003

2.3

Bendiocarb

0.005

0.7

l.l

0.7

Propiconizole

0.0125

0.3

0.02

0.05

0.02

0.01

0.007

0.0002

Chlorpyrifos

Carbaryl

0.014

0.009

Cyfluthrin

0.025

n/a

n/a

n/a

n/a

Ipridione

0.061

0.03

0.03

0.04

0.03

0.08

n/a

n/a

n/a

n/a

Thiophanate-Methyl

c

* All pesticides were watered in immediately following application with 0.63 cm of post-application irrigation. n/d = not detected. n/a = not available. b

c



307

may be useful in predicting hazard associated with other related pesticides not included in the present study. It is also of interest that the volatile and dislodgeabie foliar residues measured in the expanded study are generally greater than those measured in the initial study (compare IHQ and DHQ values in Tables III and IV versus VI and VII, respectively). This disparity is likely the result of two factors; the first is the use of a spray drift suppression skirt that resulted in more pesticide being applied to the turfgrass during applications and the second is the reduction in the amount of post-application irrigation used in the expanded study (1.3 to 0.63 cm). Careful examination of both features may provide the means to attenuate turfgrass residues and reduce the hazard associate with such exposures. Effects of Post-Application Irrigation. Using the 1.3 cm level of post-application irrigation (Tables III and IV), two unwanted processes occurred. First, trichlorfon was converted into its more toxic, volatile and water-soluble metabolite, D D V P , at a higher level than with 0.63 cm of irrigation (Tables V I and VII). Second, the higher level of post-application irrigation seems to delay the appearance of the maximal level of hazard associated with volatile and dislodgeabie foliar residues from the day of application (0.63 cm) to Days 2 and 3 following application (1.3 cm). In order to demonstrate this aspect independently of the conflicting factor of different application regimes, we applied isazofos with the boom sprayer used in the original study and compared the two different levels of post-application irrigation (Table VIII). To show the dramatic effect that post-application irrigation has on the initial levels of dislodgeabie foliar residues, samples were collected 15 min following application but before irrigation. Both levels of irrigation greatly reduced the initial levels of dislodgeabie foliar residues, (compare 15 min values to 3 h values), with the 1.3 cm level slightly more effective than the 0.63 cm level. After irrigation, however, the maximal hazard associated with isazofos occurred on Day 2 (DHQ = 17.1) in the presence of 1.3 cm of irrigation whereas the maximal hazard in the presence of 0.63 cm of irrigation occurred at 3 h post-application (DHQ = 12). These findings indicate that the judicial use of post-application irrigation in combination with managed spray volume and sprayer configurations may be an effective means to attenuate the hazards associated with exposures to volatile and dislodgeabie foliar residues associated with pesticide-treated turfgrass. Use of Adjuvants and Thatch Management to Reduce Volatile and Dislodgeabie Pesticide Residues. In order to mitigate the exposure potential of the organophosphorous insecticides that have high vapor pressures and inherent high toxicity, we evaluated the practical use of spray tank adjuvants and the importance of thatch accumulation on the dissipation of volatile and dislodgeabie foliar residues following application of these more problematic insecticides. Two adjuvants were examined in these preliminary studies: Aqua Gro-L®, a non-ionic wetting agent/penetrant; and Exhalt 800®, an encapsulating spreader/sticker. Because ethoprop consistently resulted in the highest IHQ and DHQ values, it was chosen as a problematic organophosphorous insecticide for study in the combined presence with adjuvants. It was applied at the established rate reported previously to our standard


308


Table VIII. Effect of post-application irrigation on dislodgeabie foliar residues of isazofos.

Post Application Irrigation

Dislodgeabie Residues fag/m ) 2

Dose (mg/kg)

Rfd (mg/kg/day)

DHQ (Dose/Rfd)

1.3 cm Day 1

15 min* 3h 8h

Day 2 Day 3

3,920 20 10 120 40

1.0 xlO5.7 xlO' 2.9 χ 10 3.4 χ ΙΟ" I.lxiO"

0.00002 0.00002 0.00002 0.00002 0.00002

560.0 2.86 1.43 17.14 5.71

4,280 84 63 61 12

1.2 χ iO* 2.4 χ ΙΟ" Ι.δχΙΟ·

2

0.00002 0.00002 0.00002 0.00002 0.00002

611.1 12.04 8.93 8.65 1.70

2

5

s 4

4

0.63 cm Day 1

Day 2 Day 3

8

15 min* 3h 8h

4

4

1.7X10-

4

5

3.4 χ HT

Dislodgeabie foliar residue samples were collected 15 min after application prior to irrigation.



309 small circular plots using a Rogers Wind Foil® sprayer. For those applications done using spray tank adjuvants, a 2 % v/v concentration of adjuvant was used. Volatile and dislodgeabie foliar residues were collected, analyzed and IHQ and D H Q values calculated as before. As for previous experiments, pesticide applications were carried out at the University of Massachusetts Turfgrass Research Facility in South Deerfield, M A . A paired-plot experimental design was used in these comparisons with one group of plots being prepared on turf established in 1991, which was never aerated or dethatched (Mature Turf) and the other plots being prepared on turf established in 1995 (New Thatch). It was estimated by physical examination that the mature turf plots had a thatch layer that was approximately 3-times thicker than the more newly established turf plots. For Application #1, only ethoprop was applied to a mature turf plot whereas the new turf received ethoprop with the adjuvant. In Application # 2, the treatments were reversed with the new plots receiving only ethoprop and the mature plots receiving ethoprop plus adjuvant. To evaluate the effects of thatch accumulation on the dissipation of volatile and dislodgeabie foliar residues, two additional applications of ethoprop were made. In the first application, ethoprop was applied simultaneously to a mature turf plot and a new turf plot, both in the absence of any spray tank adjuvant. In the second, ethoprop was applied to a mature turf plot that has been dethatched by vericutting in two directions, and the results compared to results obtained from this same plot prior to dethatching. Table I X presents the results of applying ethoprop to mature and more recently established turf plots in the presence and absence of the wetting agent, Aqua Gro®. In no instance did the addition of this adjuvant result in substantial reductions in the amount of volatile and dislodgeabie foliar residues of ethoprop following its application as determined by IHQ and DHQ determinations. In fact, the addition of this adjuvant generally resulted in slight increases in the IHQ and D H Q estimations between treatments. Similar results were obtained using the spreader/sticker adjuvant, Exhalt 800® (data not shown). Under these experimental conditions, neither of the adjuvants tested appeared to reduce the exposure to volatile and dislodgeabie foliar residues following the application of ethoprop or isofenphos (data not shown) as judged by IHQ and D H Q determinations, respectively. Similarly, no substantial or consistent differences were found in levels of volatile or dislodgeabie residues following the application of ethoprop or isofenphos to mature versus more recently established turf plots or to thatched versus dethatched turf plots (data not shown). These preliminary results indicated that thatch management may not be a meaningful approach to mitigating the exposure to volatile and dislodgeabie residues following pesticide application to turfgrass. Conclusions The large majority of the turfgrass pesticides evaluated in this study were deemed safe using the U S E P A Hazard Quotient criteria. Pesticides that were not deemed completely safe by these criteria were all organophosphorous insecticides with high


310

Table IX. Inhalation (IHQs) and dermal (DHQs) hazard quotients for ethoprop following application with and without the wetting agent (WA) Aqua-Gro to mature and newly established turfgrass. R

ETHOPROP IHQs


Applications without WA

Applications with WA New turf

New turf

Mature turf

Mature turf

99 72 32

34 27 10

116 123 63

51 32 13

6.0 5.1

5.3 4.7 2.4

41 26

17 11 4.9

0.6 0.2 0.5

3.1 5.2 1.9

0.4 1.0 0.7

3.2 3.4 1.9

SAMPLE Day 1 9:00-11:00 11:00-15:00 15:00-19:00 Day 2 9:00-11:00 11:00- 15:00 15:00-19:00 Day 3 9:00-11:00 11:00-15:00 15:00-19:00

ETHOPROP DHQs Applications without WA Mature turf

SAMPLE Day 1 2 hr post app. 5 hr post app. Day 2 12:00 p.m.

βΐ)

57 35

Mature turf βΐ)

25 56

Applications with WA New turf βΐ)

69 35

25

Day 3 12:00 p.m.

* Application #1. Application #2. Sample period canceled. below detection limit. b

c

d


New turf β2)

49 56 30


311 vapor pressures and high inherent toxicity. Because effective organophosphorous and carbamate insecticide alternatives are available that do not share these problematic features, the use of ethoprop, isazofos and diaztnon on turfgrass should be minimized and applied judiciously and only when a delayed reentry period is practical. Additionally, the use of wetting agents and spreader/sticker adjuvants and thatch management do not appear to be practical means to minimize the potential exposure to these pesticides once applied to turfgrass. Post-application irrigation and spray volume regimes, however, may merit additional consideration. We have determined that selected pesticides, which possess high volatility and toxicity, may result in exposure situations that cannot be deemed completely safe as judged by the USEPA Hazard Quotient criteria. This assessment, however, must be viewed in terms of the assumptions that were used in making these estimations. In all instances, maximum pesticide concentrations were used for the entire 4 hour exposure period, maximum rates for pesticide applications were used, and dermal transfer coefficients and dermal penetration factors were taken from non-turfgrass situations that are likely to exceed those that would take place on a golf course. Because of this, we view such estimates as worst case scenarios. In order to more accurately predict the health implications of pesticide exposure on golfers, a relevant dosimetry/biomonitoring evaluation of golfers, playing golf on a golf course, needs to be carried out. With more accurate exposure estimates, it is our belief that the exposure levels reported here will be found to be in excess of the true exposure to pesticides on a golf course. References 1.

2. 3. 4.

5.

6.

7. 8.

Spencer, W. F.; Cliath, M . M. Movement of pesticides from soil to the atmosphere. In Long range transport of pesticides; Kurtz, D. A . (ed.).; Lewis Publ.: Chelsea, MI, 1990; pp. 1-16. Staten, G. Contamination of cottonfieldsby 2,4-D or hormone type weed sprays. J. Am. Soc. Agron., 1946, 38:536-544. Taylor, A . W. Post-application volatilization of pesticides under field conditions. J. Air Pollut. Control. Assoc., 1978, 25:922-927. Cooper, R. J. Volatilization as an avenue for pesticide dissipation. In: Carrow, Ν. E. et al. (ed.); Intl. Turfgrass Soc. Res.; J., Intertec Publ. Corp.: Overland Park, K S , 1993, Vol. 7; pp. 116-126. Murphy, K . C.; Cooper, R. J.; Clark, J. M . Volatile and dislodgeabie residues following trichlorfon and isazofos application to turfgrass and implication for human exposure. Crop Sci., 1996, 36:1446-1454. Murphy, K . C.; Cooper, R. J.; Clark, J. M. Volatile and dislodgeable residues following triadimefon and MCPP application to turfgrass and implication for human exposure. Crop Sci., 1996, 36:1455-1461. Cooper, R. J.; Jenkins, J. J.; Curtis, A. S. Pendimethalin volatility following application to turfgrass. J. Environ. Qual., 1990, 79:508-513. Taylor, A. W.; Glotfelty, D. E.; Glass, B . L.; Freeman, H . P.; Edwards, W. M. Volatilization of dieldrin and heptachlorfroma maizefieldJ. Agric. Food Chem., 1976, 24:625-631.


312 9.

10. 11.


12.

13.

14. 15. 16.

17.

18.

19. 20. 21. 22. 23. 24.

25. 26.

Taylor, A . W.; Glotfelty, D. E.; Turner, Β. C.; Silver, R. E.; Freeman, H . P.; Weiss, A . Volatilization of dieldrin and heptachlor residues from field vegetation. J. Agric. Food Chem., 1977, 25:542-548. Spencer, W. F.; Farmer, W. J.; Cliath, M. M . Pesticide volatilization. Residue Reviews, 1973, 49:1-47. Fenske, R. Nonuniform dermal deposition patterns during occupational exposure to pesticides. Arch. Env. Contam. Toxicol., 1990, 19:332-337. Knaak, J.; Iwata, Y . The safe levels concept and the rapid field method. In: Plimmer, J. (ed.) Pesticide residue exposure; A C S Sympositum Series 182; Am. Chem. Soc.: Washington, D.C., 1982; pp. 23-39. Zweig, G. Leffingwell, J. T.; Popendorf, W. The relationship between dermal pesticide exposure by fruit harvesters and dislodgeabie foliar residues. Environ. Health, 1985, B20(l):27-59. Jenkins, J. J.; Cooper, R. J.; Curtis, A . S. In: Kurtz, D . A . (ed.); Long range transport of pesticides; Lewis Publ.: Chelsea, MI, 1990; pp. 29-46. Jenkins, J. J.; Cooper, R. J.; Curtis, A. S. Bull. Environ. Contam. Tox. 1991, 47; pp. 594-601. Jenkins, J. J.; Cooper, R. J.; Curtis, A . S. Two small-plot techniques for measuring airborne and dislodgeabie residues of pendimethalin following application to turfgrass. In: Racke, K . D ; Leslie, A . R. (eds.); Pesticides in urban environments; A C S Symposium Series 522; Am. Chem. Soc.: Washington, D.C., 1993; pp. 28-242. Wilson, J. D.; Thurtell, G. W.; Kidd, G. E.; Beauchamp, E.G. Estimation of the rate of gaseous mass transferfroma surface source plot to the atmosphere. Atmos. Environ., 1982, 6:1861-1867. Wilson, J. D.; Catchpoole, V. R.; Denmead, O. T.; Thurtell, G. W. Verification of a simple micrometeorological method for estimating the rate of gaseous mass transferfromthe ground to the atmosphere. Agric. Meteorol., 1983, 29:183-189. Majewski, M . S.; Glotfelty, D. E.; Seiber, J. N . Atmos. Environ. 1989, 23(5): 929-938. Majewski, M. S.; Glotfelty, D. E.; Paw, K . T.; Seiber, J. N. Sci. Technol. 1990, 24: 1490-1497. Majewski, M . S.; McChesney, M. M.; Seiber, J. N. Environ. Toxicol. Chem. 1991, 10: 301-311. U.S. Environmental Protection Agency. Exposure factors handbook. Appendix 3. Office of Health and Environmental Assessment: Washington, D.C. 1989, U.S. Environmental Protection Agency. Office of Pesticide Programs Reference Dose Tracking Report. Washington, D.C. 1993. Thompson, D. G.; Stephenson, G. R.; Sears, M.K Persistence, distribution and dislodgeable residues of 2,4-D following its application to turfgrass. Pest. Sci. 1984. 15:353-360. U.S. Environmental Protection Agency. Dermal exposure assessment: principles and applications. Interim Report. EPA/600/8-91/01 IB. 1992. Clark, J. M. Evaluation of management factors affecting volatile loss and dislodgeabie foliar residues. USGA, 1996 Turfgrass and Environmental Research Summary. USGA: Far Hills, NJ, 1996; pp. 60-63. Clark and Kenna; Fate and Management of Turfgrass Chemicals ACS Symposium Series; American Chemical Society: Washington, DC, 1999.

Fate and Management of Turfgrass Chemicals - American Chemical

Recommend Documents