Exposure of Applicators to MonosodiumMethanearsonate and Cacodylic Acid in Forestry

L A. NORRIS

Department of Forest Science, Oregon State University, Corvallis, OR 97331

Effective worker training and supervision and use ofprotective gear should minimize exposure of both humansand other animals to MSMA and cacodylic acid, herbicidesused in forestry. Arsenic (As) concentration in urine, auseful index to exposure, increased rapidly with anapplicator's first exposure, then decreased rapidly whenexposure ceased; As concentration reflected the degree ofapplicator exposure and paralleled levels in smallmammals in treated areas. Poor handling and applicationtechniques raised As concentrations in urine as high as1.8 ppm, corresponding to an exposure of at least0.036 mg As/kg body weight/day. Proper handlingtechniques and use of protective gear can reduce exposureto < 0.003 to 0.007 mg As/kg body weight/day, if urine isassumed the sole excretory source.

The organic arsenic-containing herbicides cacodylic acid(dimethylarsinic acid) and MSMA (monosodium methanearsonate) areused to kill selected trees (usually conifers) during preconvnercialthinning in Pacific Northwest forests. Although felling unwantedtrees with saws is an al ternative to chemical thinning, it iscostly, dangerous to forest workers, increases fire danger becausefelling concentrates slash on the ground, reduces access of domesticand wild animals to forage, and has an unsightly appearance.Chemically killed trees are left standing; the needles or leavesfall first, then the branches, and eventually the main stem.

Both cacodylic acid and MSMA are registered for this use and arebeing applied by both private and public forest-management groups inthe Pacific Northwest and elsewhere in the United States. Total usefigures are difficult to compile, the level varying over time; forexample, the USDA Forest Service applied 18,000 lb on 3,558 acres inFiscal Year 1979 (1), but larger amounts were used in the early1970's when more funds were being allocated for intensive forestmanagement.

0097-6156/85/0273 -0109506.00/01985 American Chemical Society

110 DERMAL EXPOSURE RELATED TO PESTICIDE L..2

Several million acres of young, overstocked stands are at ornear the age where precommercial thinning is needed. MSMA inparticular, and possibly cacodylic acid, could be important toolsfor this purpose, but both benefits and risks must be assessed.Particularly at risk are pesticide applicators, who have thegreatest, and only substantive, potential for exposure. The purposeof this paper is (1) to review (a) studies of applicator exposure toMSMA and cacodylic acid and (b) strategies for applicator protectionand (2) to calculate magnitude of applicator exposure.

Application Methods and Opportunities for Exposure

MSMA and cacodylic acid are injected into the tree cambium by one ofthree methods:

. Hack and squirt--axe or hatchet used to cut into the stem,usually one cut per inch of diameter, and herbicide applied witha plastic squeeze bottle or pump-type oil can,. Injection hatchet--specially designed hatchet containing aninertia-driven piston which forces the herbicide concentrateinto the cut when the hatchet strikes the tree stem, and. Injection bar--long tube (containing herbicide) with a narrowbit on the end; the bit is plunged into the cambium at the baseof the tree, and a small amount of herbicide enters the cut inthe tree through a hole In the bit when the operator opens theval ye.

Each method allows opportunity for applicator exposure at threepoints:

. Transporting and transferring the herbicide concentrate frailthe manufacturer's container to the application equipment,

Carrying, using, and repairing the application equipment inthe field, and. Emptying and cleaning application equipment at the end of thework day.

Potential Exposure Indexes

Arsenic (As) has been reported in a variety of tissues, any of whichare potentially useful as indexes to exposure. However, the organicpentavalent arsenicals are not accumulated in tissues and arerapidly excreted in urine (2-4). Therefore, urine generally is aparticularly valuable index to applicator exposure. Exon et al. (5)reported both urine and feces were important pathways of excretionin rabbits exposed to MSMA in their feed. They found 70 % ofingested As had been excreted (54% in urine, 46% in feces) during a17-week exposure period. Arsenic levels in liver, hair, and urinewere the same as in controls after 12 weeks of MSMA exposurefollowed by 5 weeks of control rations, indicating excretion wasultimately fairly complete.

Hai r and blood are possible indexes of applicator exposure.Exon et al. (5) reported As accumulation in hair of rabbits, butabout 4 weeks of continuous exposure to MSMA in their feed wererequired before the concentration was high enough to measure withconfidence. Dickinson (6) reported nonsignificant As accumulation

8. NORRIS MSMA and Cacodylic Acid Exposure in Forestry

in hair of cattle fed enough MSMA in their diet (10 mg/kg/day for10 or 12 days) to cause the death of the animals. However, Asconcentration increased measurably in 10 days In hair of cattle

exposed to 10 mg/kg/day of cacodylic acid; the concentrationcontinued to increase with duration of exposure. Arsenic in hairmay be a useful index to long-term As exposure, but it does not

respond with sufficient speed to be useful in short-term tests orfor operational monitoring of workers. Wagner and Weswig (7) found

a slight increase in As levels in blood of forest workers applying

cacodylic acid, but the increases were quite erratic and were not

apparent before the second week of exposure.Hair is simple to collect and analyze, but arsenic levels in

hair do not respond rapidly to exposure. Blood both is difficult to

collect and does not give a consistent or rapid enough response toAs exposure of an organism. Thus, even with the attendant

collection problems, urine is the most practical index to theexposure of forest workers to the organic arsenical herbicides.

Unfortunately, the pharmacokinetics of these herbicides have not

been fully developed for dermal exposure, and there are indications

that urine is not the sole excretory route. Thus, estimates of

exposure based only on As excretion in urine may be only 30t of

actual exposure levels (5, 8).

Applicator Exposure and Influence of Protective Strategies

The First Study. Forest-applicator exposure to MSMA and cacodylic

acid was first studied by Tarrant and Allard (9). They collected

individual urine samples on Monday mornings an Friday afternoons

for 9 consecutive weeks from five applicators (each using a

different combination of application method and chemical) and one

control. Workers were supplied with clean clothes daily, includingtwo pair of cotton gloves (to be changed at noon, or earlier if one

pair became substantially contaminated with herbicide). Completedata were obtained for weeks 2, 3, 4, 7, and 8 (except for the

injection hatchet-cacodylic acid combination, which was not included

in the analysis).

Analysis of variance showed that As concentration In urine was

significantly higher (P < 0.05) than in the control (Table I).

Concentration was higher by the end of the first work week, and

Friday levels were higher than the succeeding Monday levels,indicating absence from contact over the weekend was sufficient to

complete elimination (except in a for cases where Friday levels weresubstantially higher than average). The Friday concentrations did

not increase substantively over the 9 weeks, which also indicates

rapid clearance and lack of accumulation. None of the workers

experienced illness that seemed associated with the herbicideexposure.

Official standards for As in urine following exposure to these

compounds is lacking, other than one manufacturer's recommendationof 0.3 ppm. This standard appears to be based on a study of urinaryexcretion of arsenic in 163 unexposed individuals, which showed a

maximum excretion value of 0.85 mg As/day (10); the 0.3 ppmconcentration was selected based on a daily void of urine

and is therefore quite conservative. in the Tarrant and Allard

112 DERMAL EXPOSURE RELATED TO PESTICIDE USE

study (9), 47% of the Friday values were > 0.3 ppm; the maximumvalue was 2.5 ppm. In contrast, only 4% of the observations (all inthe injection hatchet-cacodylic acid treatment group) were > 0.3 ppmon Mondays.

Table I. Mean Concentration ( + 1 Standard Deviation) of Arsenic inUrine from Forest Workers at 2, 3, 4, 7, and 8 Weeks of a 9-Week

Exposure Period (9)

Total As(mg/1) Monday Fr f day

% % >

0.3 ppm 0.3 ppm

0.04 (+ 0.01) 0 0.07 (* 0.03) 4

0.07 (+ 0.01) 0 0.26 (+ 0.05) 32

0.03 (+ 0.01) 0 0.41 (+ 0.08) 46

0.10 (+ 0.01) 0 0.50 (+ 0.12) 54

0.10 (+ 0.01) 0 0.36 (+ 0.07) 42

Appl ication Methodand Chemical

r6ntrol ,no exposure

Hack and squi rt,MSMA

Hack and squirt,cacodyl ic acid

Injection hatchet,MSMA

Injection bar,MSMA

Source: Reproduced with permission from Ref. 9. Copyright 1972,American Medical Association.

Follow-up Studies. The results of the Tarrant and Allard study (9),CiinbTned

wil an incident in which several dead snowshoe hares wiTh

elevated levels of As (more than 100 ppm in various tissues) werefound in a treated area, prompted an intensive effort to furtherel ucidate patterns of applicator exposure and to evaluate means ofreducing exposure to humans and other animals.

Investigation of the hare mortality incident revealed thatcareless handling techniques and poor procedures for disposing ofleftover herbicide and clean-up water were the likely sources of Asfor the hares (the high salt content of the material probablyattracted them). In interviews, workers from the Tarrant and Allardstudy indicated that their cotton gloves in particular and sometimesportions of their clothing became quite wet with herbicide. Inaddition, their hands contacted the herbicide when the applicationequipment was being filled with herbicide concentrate or when theapplication equipment had to be repaired or cleaned. In some casesworkers were "splashed" with the herbicide during actual application.

Allard (11) conducted a second round of tests to determine howAs levels in urine could be reduced through worker training andimproved protection. In this test, applicators wore goggles, usedan impervious face cream, and were instructed in better techniquesfor handling of both herbicide concentrate and applicationequipment. In addition, two groups used rubber gloves instead ofcotton gloves.

g. NORR IS MSMA and Cacodylic Acid Exposure in Forestry 113

Arsenic levels in urine were substantially reduced in all crewsbut the Kaniksu (Table II). It was concluded from periodicobservations and interviews of crew members and foremen thatimpervious gloves, skin cream, and effective training andsupervision were the key factors. The foreman and the trainer ofthe Colville crew had been particularly effective; As level in urinefor that crew, which wore only cotton gloves, was similar to that ofone crew wearing rubber gloves, and the number of observations> 0.3 ppm was only 1/3 that of a similar crew in the same area theprevious year (Table I).

Table II. Mean Concentration of Arsenic in Urine from ForestWorkers Applying MSMA or Cacodylic Acid via the Hack and Squirt

Method in Operational Precomercial Tree Thinning (11)

Crew

Total As (ppm)1Monday Friday

Mean% >

Max. 0.3 ppm Mean Max. 0.3 ppm

MSMAColville 0.05 0.37 8 0.15 0.46 11Okanogan 0.07 0.50 9 0.24 1.30 33Wenatchee 0.03 0.14 0 0.07 0.35 7Cedar Creek 0.04 0.09 0 0.02 0.03 0Naselle 4 0.04 0.20 0 0.14 0.54 14

Cacodylic AcidKani ksu 0.01 0.02 0 0.80 1.80 75

1 Controls averaged 0.02 ppm.2 Crews used rubber gloves instead of cotton gloves.

Wagner and Weswig (7) implemented the best of all theseprocedures in monitoring an operational thinning program a yearlater. The crew consisted of five college students and a full-timesupervisor who were carefully trained in proper procedures forhandling the herbicide (cacodylic acid) and the hack and squirtme thod. All were impressed with the importance of minimizingpersonal exposure and based on their performance, seemed to haveapproached the study as something of a personal crusade.

Wagner and Weswig collected 24-hour urine samples from eachworker beginning late Thursday afternoon and continuing until theend of the work day on Friday, when blood samples were collected andanalyzed (Table III). At no time during the exposure period of7 weeks (5 work days/week) did As concentration in urine exceed0.2 ppm. Arsenic excretion increased once exposure began, reachingthe average level during the second week of exposure, but fellrapidly when exposure ended, reinforcing the results from the animal

H4 DERMAL EXPOSURE RELATED TO PESTICIDE USE

Table III. Mean Concentration in Blood and Excretion in Urine ofArsenic from Five Forest Workers Exposed to Cacodylic Acid and

Five Controls (7)

Week'Workers

Exposed Controls

Arsenic In blood (ppm)

1 0.05 0.052 0.173 0.264 0.195 0.066 0.06 0.067 0.038 0.039 0.0410 0.0111 0.02 0.02

Arsenic in urine (mg/24 h)

1 0.0382 0.077 0.0733 0.1414 0.1725 0.1066 0.103 0.0427 0.1698 0.2049 0.02410 0.06811 0.026

1 Week 1 was a pre-exposure period; weeks 2 through 8 were full5-day work weeks, although work records indicate applicationaccounted for only 23.7 hours of each 40-hour work week, and eachworker applied an average of 817 g dimethylarsinic acid/week; week9 included only 10 hours of exposure, which occurred during thefirst 2 days of the week; weeks 10 and 11 were post-exposureperiods.

Source: Reproduced with permission from Ref. 7. Copyright 1974.American Medical Association.

g NORRIS MSMA and Cacodylic Acid Exposure in Forestry 115

feeding studies (5). Though As level in blood initially increased,it decreased to control levels in 4 weeks and correlated poorly(correlation coefficient w 0.14) with As excretion in urine. On thebasis of 70 kg body weight and the assumptions that (1) excretionlevel measured at the end of the week is representative of the dailyrate and (2) urine is the principal route of excretion, theseworkers were exposed to an average of 0.002 mg As/kg body weight/day.

Monitoring Operational Projects

Seven operational application units were monitored on the basis ofinformation from the previous tests in an effort to minimizeapplicator exposure (11). Operational monitoring invol ved sixindividual application crews of from five to ten applicators; onecrew treated two units. All crews used the hack and squirt method,but some applied cacoclylic acid and others MSMA. The time requiredto complete a unit varied from 1 to 3 months, but not all crews wereinvolved with chemical thinning each day.

Each crew and foreman were briefed on results of previousstudies, and the importance of minimizing personal exposure wasemphasized. Guidel i nes on application equipment, protecti ve gear,and methods of handling and applying the herbicide to minimizeexposure were presented. Type and density of vegetation, roughnessof terrain, and climatic factors varied such that the method andprotective equipment best suited to each circumstance wereimplemented; no effort to "standardize" was made, emphasizing theoperational nature of the tests. Single urine samples werecollected from each applicator in each unit near the end of the workday on Friday; a similar sample was collected every third Monday,before the work day began. Of the seven units monitored, five werehighly successful (no As levels > 0.3 ppm), one was fairlysuccessful, and one (Kaniksu 1) was a failure (Table IV).

Table IV. Mean Concentration of Arsenic in Urine frcn ForestWorkers in Seven Application Units Thinned with MSMA or Cacoctylic

Acid by the Hack and Squirt Method (12)

Total As (ppm)Monday Friday

%> % >Application Mean Max. 0.3 ppm Mean Max. 0.3 ppm

Unit

Colville 1 0.06 0.21 0 0.10 0.34 4Colville 2 0.04 0.21 0 0.06 0.32 2Colville 3 0.03 0.11 0 0.05 0.13 0Siuslaw 1 0.03 0.05 0 0.09 0.19 0Waselle 1 0.03 0.08 0 0.09 0.49 5Cedar Creek 1 0.06 0.13 0 0.08 0.52 10Kaniksu 1 0.26 0.50 33 0.38 1.74 45

116 DERMAL EXPOSURE RELATED TO PESTICIDE USE

The pattern of arsenic in urine from the Kaniksu 1 crew is quiteinteresting (Table V). Mean As concentration increased immediately,the number of observations > 0.3 ppm exceeding 50%. As soon asthese results were available, the crew foreman and supervisor werenotified, and they intensified efforts to reduce exposure. Theywere partially successful for about 2 weeks (17% of observations> 0.3 ppm); then the average and maximum concentrations began torise. Late in July, 83% were > 0.3 ppm, and thinning was stopped toprevent futher applicator exposure. During the next 3 weeks, Asconcentration in urine dropped. After 2 succeeding weeks when theaverage and maximum concentrations were in the normal range (0.02 to0.03 ppm), the crew returned to thinning for 5 days. All urinesamples collected at the end of that period exceeded 0.03 ppm As;they averaged 0.85 ppm, and maximum was 1.74 ppm

Table V. Mean Concentration of Arsenic in Urine from Kaniksu 1Application Crew (12)

Total As (ppm)Crew % >

Date Day Mean Range Size 0.3 ppm

June—T5— Tue. 0.08 0.02-0.20 5 0

18 Fri. 0.31 0.08-0.42 5 6025 Fri. 0.20 0.04-0.33 5 20

12._2,1x

Fri. 0.21 0.05-0.33 6 336 Tue. 0.17 0.03-0.48 6 179 Fri. 0.15 0.07-0.37 6 17

16 Fri. 0.29 0.05-0.68 6 3323 Fri. 0.72 0.19-1.32 6 6726 Mon. 0.53 0.11-1.01 6 8330 Fri. 0.49 0.10-1.38 6 50

AugustChemical thinning suspended

6 Fri. 0.17 0.13-0.36 6 1713 Fri. 0.02 0.02-0.03 6 020 Fri. 0.02 0.01-0.03 5 023 Thinning resumed27 Fri. 0.85 0.32-1.74 3 100

(Last day of thinning)

The daily diary of the Kaniksu 1 foreman noted numerousoccasions when applicators received considerable exposure as aresult of poor handling practices and use of inappropriate gear.Coincident with applicator monitoring, however, small mammals(usually mice) were trapped in these seven units and analyzed forarsenic. Interestingly (though the details are beyond the scope of

8. NORRIS MSMA and Cacodylic Acid Exposure in Forestry 117

this paper), there was a strong relationship between Asconcentration in small mammals and that in applicator urine(Table VI)--which leads me to believe that care in application is apredominant factor influencing small animal as well as humanexposure. Thus, monitoring applicator urine for As may be useful asan index to both applicator and animal exposure.

As Concentration in Urine Related to 24-Hour Excretion in Urine

Wagner and Weswig (7) recommended 24-hour As excretion in urine asthe best measure of—applicator exposure. Though useful inexperimental work, this measure is impractical as an operationalmonitoring tool: the likelihood of workers successfully collectinguncontaminated 24-hour urine samples on a routine basis seems low.The best monitoring tool is the one which "will be used" and whichgives a reasonably good index to exposure.

Table VI. Mean Concentration of Arsenic in Whole Bodies of SmallMammals and in Urine from Applicators (12)

Arsenic in Applicator Urine Arsenic in Small-Manual Whole Bodies

Application %Friday % ObservationsUnits i Observations < 0.5 > 1 > 3 > 5

> 0.03 ppm PPm PP* PPR

Col vilTe 1 4 54 9 2 0Colville 2 2 72 9 0 0Colville 3 0 38 37 9 0Siuslaw 1 0 83 0 0 0Kaniksu 1 45 20 50 25 15

I No data for Naselle or Cedar Creek units.

Norris (13) conducted a study to determine the relationship, ifany, between—Xs concentration in a single (small) urine sample andAs excretion in urine over a 24-hour period. In this study, 17workers applied MSMA by the hack and squirt method. On thedesignated collection day, each crew member received one large andone small container; all urine excreted during the 24-hour periodwas collected in the large container except that excreted at the endof the work day, which was collected in the small container. Thepaired samples (one large and one small) constituted a sample set.The number of sample sets from any one individual ranged from one tonine (average 3.3); in total, 56 sample sets were collected. Thevolume of both samples in a set was measured and urine analyzed fortotal As, creatinine, and osmolality.

Multiple regression analysis of data shooed that the independentvariables (urine volume, As concentration, mg% creatinine, andosmolality) accounted for 76 %of the variation in the dependentvariable lug As excreted in 24 hours). Adding independent variables

118 DERMAL. EXPOSURE RELATED TO PESTICIDE USE

stepwise, in order of their importance, showed that:. Arsenic concentration in the small sample accounted for 73.4%of the variation,. Urine volume and As concentration in the small sampleaccounted for 75.9% of the variation, and. The other independent variables did not significantly improvethe model.

Thus, two types of data, easily collected, could be used to predictapplicator exposure with reasonable accuracy in operationalmonitoring programs, according to the relationship:

V 12.88 + 1386 (X1) + 0.14 (X2); r 2 = 0.76where:

V = ug As excreted in 24 hours,XI = ppm As in a single urine sample collected at the end of

the work day, andX2 . ml urine in the sample.

In this study, the average As concentration was 0.075 ppm(maximum 0.28 ppm), and the average amount of As excreted 126 ug/24hours (maximum 323 ug/24 hours). On the basis of 70 kg body weight,these workers were exposed to an average of 0.002 (maximum of0.005) mg As/kg body weight/day. Similar values were reported byWagner and Weswig (7).

Calculating Applicator Exposure

With the possible exception of Wagner and Weswig (7) and Norris(13), none of the studies on applicator exposure gives more than anindex to exposure, based on rising and falling As concentration insingle urine samples. Unfortunately (for this purpose), both Wagnerand Weswig (7) and Norris (13) examined situations where applicatorexposure was quite low. However, exposure can be calculated usingthe several other data sets in this paper and the followingassumptions:

All arsenic absorbed is excreted in urine--The validity ofthis assumption needs testing; for instance, p ossible Asexcretion in perspiration has not been addressed. If thisassumption Is not valid, calculated exposure levels will be twoto three times lower than actual (5, 8).. mg As excreted/day = 12.88 + 1386(4m As in single urinesample) + 0,14(ml urine in single sample)--The validity of thisassumption depends on the degree to which the Norris (13)relationship is accurate at higher levels of arsenic exposure.

The average volume of urine voided in a single sample is373 ml--based on the average reported by Norris (13).

The body weight of the average forest worker is 70 kg.Using the data in Tables I-IV and these assumpt i ons, I have

calculated the mean and maximum applicator ex p osure for each dataset in this paper (Table VII). The overall average was 0.005 mgAs/kg body weignt/day, the highest individual maximum 0.036 mg As/kgbody weight/day. If urine is not the sole excretory source of As,the overall average could be 0.015 mg As/kg body weight/day and thehighest individual maximum 0.018 mg As/kg body weight/day.

8. NORRIS MSMA and Cacodylic Acid Erposure in Forestry 119

Table VII. Exposure of Forest Workers to MSMA or Cacodylic Acid:

Sumnary of Data Sets Presented in Prior Tables

Total As

in Urine, Friday (ppm)

Calculated As Exposure

(mg/kg/day)1

Crew 2 Mean Max. % > 0.3 ppm Mean Max.

Table IA 0.26 0.36 32 0.006 0.008B 0.41 0.51 46 0.009 0.011C 0.50 0.93 54 0.011 0.019D 0.36 0.58 42 0.008 0.012

Table II

E 0.15 0.46 11 0.004 0.010F 0.24 1.30 33 0.006 0.027G 0.07 0.35 7 0.002 0.008H 0.02 0.03 0 0.001 0.001I 0.14 0.54 14 0.004 0.012J 0.80 1.80 75 0.017 0.036

Table IV

K 0.10 0.34 4 0.003 0.008L 0.06 0.32 2 0.002 0.007M 0.05 0.13 0 0.002 0.004N 0.09 0.19 0 0.003 0.0050 0.09 0.49 5 0.003 0.011P 0.08 0.52 10 0.003 0.011

Q 0.38 1.74 45 0.008 0.035Average EMS 0.013Maximum 0.017 0.036

1Based on the four assumptions proposed in the text: (a) all

arsenic excreted in urine; (b) mg As excreted/day = 12.88 + 1386 (ppm

As in urine) + 0.14 (ml urine excreted in one sample), see 13; (c)

373 ml urine excreted in one sample, see 13; (d) 70 kg body-IT/eight.

Upper case letters represent entries, in order, from Tables I-1V.

2Upper case letters represent entries for exposed workers, in order,

from Tables I, II. and IV.

120 DERMAL EXPOSURE RELATED TO PESTICIDE USE

Conclusions

The concentration of total arsenic in urine increases anddecreases rapidly with initiation and termination of applicatorexposure; levels in urine usually are near normal by the Mondaymorning following a full week of chemical thinning. Moreover, Aslevel of exposed applicators seems to parallel that in small mammalsin treated areas. The use of impervious gloves, long-sleevedshirts, and silicon face cream, combined with effective training andsupervision, markedly reduces urine arsenic levels. Thus, a urinemonitoring program can give a good index to exposure of humans andother animals during operational thinning. Even single urinesamples can be used to project daily As excretion, facilitatingmonitoring and calculation of applicator exposure.

Several monitoring efforts suggest that forest workers applyingMSMA and cacodylic acid may be exposed to As levels as high as0.036 mg/kg (average 0.005 mg/kg), although the actual level varieswith the worker and the protective measures employed. However,these levels likely are underestimates because urine may not be theonly source of excretion.

Nontechnical Summary

MSMA and cacodylic acid herbicides are used to thin overstockedforest stands. Although these arsenic containing herbicides areinjected into the tree stem, applicators may still be exposed duringthe handling, application and clean-up stages of operation. Theamount of arsenic in urine is a good indicator of applicatorexposure. The first tests conducted during operational thinningprograms showed the levels of applicator exposure were higher thanadvised, and there appeared to he a correlation between the levelsof arsenic in urine from applicators and the whole body levels ofarsenic in small animals. This suggests that minimizing applicatorexposure will also reduce exposure to small mammals. Later testsshowed effective worker training and supervision, and the use ofprotective gear are effective in this regard. Monitoring arsenic inapplicator urine is useful for determining if exposure goals arebeing achieved during operational forest thinning with MSMA andcacodylic acid herbicides.

Acknowledgments

This research is supported in part by USDA Forest Service, PacificNorthwest Forest and Range Experiment Station, PNW 84-359.

Literature Cited

"Pesticide-use Advisory Memorandum 246." USDA Forest Service,1980.Schroeder, H. A.; Balassa, J. J. J. Chronic Dis. 1966, 19,85-106.

3. Hogan, R. B.; Eagle, H. J. Pharmacol. Exp. Ther. 1944, 80,93-113.

8. NORRIS MSMA and Cacodylic Acid Exposure in Forestry 121

Frost, D. V. Fed. Proc. Fed. Am. Soc. Exp. Biol. 1967, 26,194-208.Exon, J. H.; Harr, J. R.; Claeys, R. R. Nutr. Rep. Int. 1974,9, 351-7.Dickinson, J. O. Am. J. Vet. Res. 1972, 33, 1889-92.Wagner, S. L.; Weswfg, P. Arch. Environ. Health 1974, 28, 77-9.Dutkiewicz, T. Environ. Health Persp. 1977, 19, 173-7.Tarrant, R. F.; Allard, J. Arch. Environ. Health 1972; 24,277-80.Mattice, M. R.; Weisman, D. Amer. J. Med. Sci. 1937; 193,413-20.Allard, J., In The Behavior and Impact of Organic ArsenicalHerbicides in the Forest: Final Report of Cooperative Studies";USDA Forest Service, Pacific Northwest Forest and RangeExperiment Station, Portland, Oreg., 1974; pp. 4-8.Norris, L. A., In The Behavior and Impact of Organic ArsenicalHerbicides in the Forest: Final Report of Cooperative Studies";USDA Forest Service, Pacific Northwest Forest and RangeExperiment Station, Portland, Oreg., 1974; pp. 75-89.Norris, L.A., In The Behavior and Impact of Organic ArsenicalHerbicides in the Forest: Final Report of Cooperative Studies";USDA Forest Service, Pacific Northwest Forest and RangeExperiment Station, Portland, Oreg., 1974; pp. 10-17.

RECEIVED December 3, 1984

In: Honeycutt, Richard C.; Zweig, Gunter;

Ragsdale, Nancy N., comps. and eds.Dermal exposure related to pesticideuse: discussion of risk assessment.St. Louis: American Chemical Society;

1985.Reproduced by USDA Forest Service

for official use.