Occupational determinants of serum cholinesterase inhibition among organophosphate-exposed agricultural pesticide handlers in Washington State.

Abstract

To identify potential risk factors for serum cholinesterase (BuChE) inhibition among agricultural pesticide handlers exposed to organophosphate (OP) and N-methyl-carbamate (CB) insecticides.
We conducted a longitudinal study among 154 agricultural pesticide handlers who participated in the Washington State cholinesterase monitoring program in 2006 and 2007. BuChE inhibition was analysed in relation to reported exposures before and after adjustment for potential confounders using linear regression. ORs estimating the risk of BuChE depression (>20% from baseline) were also calculated for selected exposures based on unconditional logistic regression analyses.
An overall decrease in mean BuChE activity was observed among study participants at the time of follow-up testing during the OP/CB spray season relative to pre-season baseline levels (mean decrease of 5.6%, p<0.001). Score for estimated cumulative exposure to OP/CB insecticides in the past 30 days was a significant predictor of BuChE inhibition (beta=-1.74, p<0.001). Several specific work practices and workplace conditions were associated with greater BuChE inhibition, including mixing/loading pesticides and cleaning spray equipment. Factors that were protective against BuChE inhibition included full-face respirator use, wearing chemical-resistant boots and storing personal protective equipment in a locker at work.
Despite existing regulations, agricultural pesticide handlers continue to be exposed to OP/CB insecticides at levels resulting in BuChE inhibition. These findings suggest that modifying certain work practices could potentially reduce BuChE inhibition. Replication from other studies will be valuable.

Full text

Page 1

Occupational determinants of serum cholinesterase
inhibition among organophosphate-exposed
agricultural pesticide handlers in Washington State
Jonathan N Hofmann,1Matthew C Keifer,2Anneclaire J De Roos,1,3
Richard A Fenske,2Clement E Furlong,4,5Gerald van Belle,2,6Harvey Checkoway1,2
ABSTRACT
Objective To identify potential risk factors for serum
cholinesterase (BuChE) inhibition among agricultural
pesticide handlers exposed to organophosphate (OP) and
N-methyl-carbamate (CB) insecticides.
Methods We conducted a longitudinal study among 154
agricultural pesticide handlers who participated in the
Washington State cholinesterase monitoring program in
2006 and 2007. BuChE inhibition was analysed in relation
to reported exposures before and after adjustment for
potential confounders using linear regression. ORs
estimating the risk of BuChE depression (>20% from
baseline) were also calculated for selected exposures
based on unconditional logistic regression analyses.
Results An overall decrease in mean BuChE activity was
observed among study participants at the time of follow-
up testing during the OP/CB spray season relative to pre-
season baseline levels (mean decrease of 5.6%,
p<0.001). Score for estimated cumulative exposure to
OP/CB insecticides in the past 30 days was a significant
predictor of BuChE inhibition (b¼?1.74, p<0.001).
Several specific work practices and workplace conditions
were associated with greater BuChE inhibition, including
mixing/loading pesticides and cleaning spray equipment.
Factors that were protective against BuChE inhibition
included full-face respirator use, wearing chemical-
resistant boots and storing personal protective
equipment in a locker at work.
Conclusions Despite existing regulations, agricultural
pesticide handlers continue to be exposed to OP/CB
insecticides at levels resulting in BuChE inhibition. These
findings suggest that modifying certain work practices
could potentially reduce BuChE inhibition. Replication
from other studies will be valuable.
BACKGROUND
Organophosphate (OP) and N-methyl-carbamate
(CB) insecticides are widely used in agriculture. In
Washington State,approximately
(267166 kg) of azinphos-methyl, chlorpyrifos and
carbaryl (three common OP/CB insecticides) were
applied in apple orchards in 2007.1Other crops
grown in Washington State are also frequently
treated with OP/CBs including pears, cherries,
grapes and potatoes.1
Acute effects of OP/CB exposure have been well
documented; inhibition of neuronal acetylcholin-
esterase (AChE) enzyme activity is the main
mechanism of OP/CB toxicity.2AChE hydrolyses
the neurotransmitter acetylcholine, and thereby
plays a critical role in regulating nerve trans-
589000lb
missions in the central and peripheral nervous
systems.2Cholinesterases (ChE) are found in blood
in two different forms; AChE is associated with red
blood cell membranes, and butyrylcholinesterase
(BuChE) is present in serum.3Both AChE and
BuChE inhibition are considered to be markers of
early biological effects related to OP/CB exposure.4
Generally, AChE inhibition is considered to be
a better marker of toxicity, whereas BuChE inhi-
bition is a more sensitive marker of exposure
because it is inhibited more effectively than AChE
by most OP/CBs including chlorpyrifos, diazinon
and malathion.5BuChE measurements have been
used successfully as endpoints in several previous
studies of OP-exposed individuals.6e8
Among agricultural workers in the USA, OP/CBs
continue to be responsible for a high proportion of
pesticide poisonings,9likely due to their high acute
toxicity and widespread use in agriculture. In an
analysis of acute pesticide poisonings among US
agricultural workers from 1998 to 2005, Calvert
et al found that OP/CBs were implicated more
frequently than any other class of pesticides.9There
is also growing concern about a variety of health
endpoints that may be associated with chronic
What this paper adds
< Agricultural pesticide handlers who are exposed
to organophosphate and N-methyl-carbamate
insecticides may experience inhibition of serum
cholinesterase enzyme activity, a short-term
marker of exposure and early biological effects.
< In this study, handlers who mixed/loaded
pesticides or cleaned spray equipment had
significantly greater serum cholinesterase inhi-
bition than handlers who did not perform these
activities.
< Several work practices appeared to protect
against serum cholinesterase inhibition, including
wearing a full-face respirator (rather than a half-
face respirator), wearing chemical-resistant
footwear and storing personal protective equip-
ment in a locker at work.
< Results of this study suggest that models used
to characterise occupational pesticide exposure
for regulatory risk assessments may under-
estimate the degree of exposure attributable to
specific work activities and practices.
1Department of Epidemiology,
University of Washington,
Seattle, Washington, USA
2Department of Environmental
and Occupational Health
Sciences, University of
Washington, Seattle,
Washington, USA
3The Fred Hutchinson Cancer
Research Center, Seattle,
Washington, USA
4Department of Medicine -
Division of Medical Genetics,
University of Washington,
Seattle, Washington, USA
5Department of Genome
Sciences, University of
Washington, Seattle,
Washington, USA
6Department of Biostatistics,
University of Washington,
Seattle, Washington, USA
Correspondence to
Dr Jonathan N Hofmann,
Occupational and Environmental
Epidemiology Branch, Division of
Cancer Epidemiology and
Genetics, National Cancer
Institute, 6120 Executive Blvd,
EPS 8109, MSC 7240,
Bethesda, MD 20892-7240,
USA; hofmannjn@mail.nih.gov
Accepted 27 August 2009
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exposure to OP/CB insecticides, including chronic neurological
effects10 11and various cancers.12
Agricultural pesticide handlers are workers who are involved
in the pesticide application process, which includes applying
pesticides and related activities, such as mixing and loading
pesticides into spray tanks and repairing application equipment.
Handlers are generally considered to have higher levels of pesti-
cide exposure than agricultural workers engaged in other tasks.
However, relatively few studies have evaluated specific pesticide
handling practices and conditions in relation to biological
markers of exposure. Agricultural pesticide handlers may be
exposed to OP/CBs as a result of dermal contact with pesticides
or spray equipment,13inhalation,14accidental spills or spray
equipment malfunction,15inadequate use of personal protective
equipment (PPE),16 17and lack of decontamination facilities.18
In 2004, the Washington State Department of Labor and
Industries initiated a monitoring program among agricultural
workers who handle OP/CB insecticides. Workers who partici-
pate in this monitoring program are tested for AChE and BuChE
activity at an annual baseline (ie, before the OP/CB spray
season), and follow-up tests are conducted throughout the spray
season to evaluate ChE inhibition relative to baseline levels.
Follow-up tests are only required when workers have handled
OP/CBs for 30+ h in a 30-day period. Generally, most handlers
who return for follow-up testing have only one follow-up test
each year, although some have multiple follow-up tests during
the same spray season.19If a worker experiences >20% AChE or
BuChE inhibition at follow-up relative to annual baseline levels,
the employer must conduct a work practice investigation to
determine possible sources of exposure. For $30% AChE inhi-
bition or $40% BuChE inhibition, the worker is removed from
handling activities (with wage protection) until his or her ChE
activity returns to within 20% of baseline.
We recruited participants from the statewide ChE monitoring
programforastudytoidentifyworkplaceandbehaviouralfactors
associated with BuChE inhibition. This study addresses the need
for further epidemiological research characterising relationships
between pesticide use practices and biological markers of expo-
sure, as suggested by Acquavella et al20and Quandt et al.21Rela-
tively few studies have evaluated pesticide-related effects among
agricultural pesticide handlers due to logistic challenges in
accessing and following farmworker populations over time.10 22
By recruiting participants from the statewide ChE monitoring
program,wewereabletoinvestigatepotentialexposuresandtheir
relationship with BuChE inhibition among agricultural workers
who handle OP/CB insecticides.
METHODS
We conducted a longitudinal study among agricultural pesticide
handlers in Washington State during the OP/CB spray season
(AprileJuly) in 2006 and 2007. To recruit participants, we
collaborated with two clinics that conducted ChE monitoring in
eastern Washington State. Participants were recruited at the
clinic or the worksite at the time of follow-up ChE testing. We
used a computer-based survey instrument to collect information
from participants. The survey was administered on tablet
computers in either Spanish or English. All questions were
displayed on the screen and audio-recorded, and icons or photos
were used to represent possible responses for most questions.
The final survey consisted of 64 items. We collected infor-
mation about: (1) OP/CB insecticides used and crops treated; (2)
pesticide handling activities performed and spray equipment
used; (3) duration and frequency of handling activities; (4) use,
condition and storage of PPE; (5) decontamination practices; (6)
acute exposure events; and (7) pesticide safety training. We also
collected information about symptoms that may be related to
OP/CB exposure, non-occupational risk factors for BuChE
inhibition and demographic characteristics. Questions about
potential sources of exposure and pesticide-related symptoms
focused on the 30-day period prior to the interview and follow-
up ChE test. We considered this 30-day period to be the most
aetiologically relevant in terms of risk of BuChE inhibition
because BuChE activity levels recover naturally over time.5
Moreover, focusing on relatively recent exposures likely facili-
tated recall among study participants.
All study procedures were approved by the Institutional
Review Board at the University of Washington.
Exposure algorithm scores
Several algorithms were used to calculate scores for OP/CB
toxicity, work activities and PPE use. The toxicity score was
estimated by assigning values to specific OP/CBs based on the
relative potency factors used in the United States Environmental
Protection Agency (USEPA) cumulative risk assessments for OP
and CB insecticides.23 24Relative potency factors were deter-
mined by the USEPA based on the degree of brain AChE inhi-
bition in rat studies. As in the USEPA cumulative risk
assessments, we assumed additive effects of exposures to
multiple OP/CBs. It should be noted that one participant had an
implausibly high toxicity score that was inconsistent with: (1)
OP/CB insecticides registered for use on reported crops treated;
and (2) OP/CB use by other participants from the same orchard.
This record was therefore excluded from all analyses involving
OP/CB toxicity score. Scores for work activities and PPE use
were based on algorithms developed in the Agricultural Health
Study25; these algorithms have been validated in several studies
in different US regions with various chemicals and crops.26 27
Work activity scoring was modified slightly to include tower
sprayers and cleaning activities, and PPE scoring was modified to
reflect greater use of PPE among participants in this study rela-
tive to Agricultural Health Study participants. PPE score was
expressed in terms of the estimated likelihood of exposure:
handlers wearing full PPE received a score of zero (lowest
possible score), and handlers wearing no PPE received a score of
14 (highest possible score).
For all analyses, the exposure score variables were transformed
into z scores (ie, standardised based on the mean and standard
deviation) to allow for meaningful comparisons between these
variables. We also calculated a score for cumulative OP/CB
exposure in the last 30 days by adding the z score values for each
of the individual exposure score variables:
Ztotal¼ Ztoxicity þ Zwork activityþ ZPPE
A detailed description of the scoring system used to estimate
values for OP/CB toxicity, work activities, and PPE use is
provided in Appendix A.
Serum cholinesterase (BuChE) measurements
We obtained participants’ BuChE test results from the partici-
pating clinics in the statewide monitoring program. Clinic staff
collected and processed serum samples, which were shipped cold
overnight for laboratory testing. BuChE assays were performed
by the Washington State Public Health Laboratories in 2006 and
by Pathology Associates Medical Laboratories in 2007. Both
laboratories measuredBuChE
method28with the ChE reagent kit from Roche Diagnostics. The
Public Health Laboratories measured BuChE activity using an
automated Dade Dimension
activity usingthe Ellman
ARsystem, andPathology
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Associates Medical Laboratories used an Olympus AU5421/
AU2700 system. Both laboratories had high precision for BuChE
measurements; the coefficients of variation were 2.5% in 2006
and 2.6% in 2007.29The main outcome in our study was BuChE
inhibition, which was defined as the per cent change in BuChE
activity comparing levels at follow-up during the OP/CB spray
season against pre-season baseline levels for each handler.
We did not evaluate AChE inhibition because assays
performed in 2007 had low precision (16.7% coefficient of vari-
ation),29and analyses of state monitoring program data found
little overall evidence of AChE inhibition. In 2006, mean AChE
inhibition among handlers with at least one follow-up test was
1.8%, and only two of the 472 handlers with follow-up tests had
>20% AChE inhibition.19AChE inhibition may be a more rele-
vant outcome for handlers in developing countries where higher
levels of OP/CB exposure are generally observed.30 31
Sample selection
Records for 154 participants with complete surveys and both
baseline and follow-up BuChE test results were included in this
analysis. This represents 50.7% of the 304 pesticide handlers
who were invited to participate in this study during the 2006
and 2007 spray seasons. Study participants were similar to all
handlers in the statewide monitoring program in terms of age,
ethnicity and gender. Mean age was 33.6 years for study
participants and 32.9 years for all handlers in the state program,
and almost all handlers (>99%) in both this study and the state
program were Latino males.19
For handlers who participated in this study in either 2006 or
2007, we selected the first completed survey and corresponding
BuChE data for this analysis. Some handlers participated in this
study in both 2006 and 2007 (N¼22). For those subjects, we
chose only one record per subject to ensure independent results.
The record with the larger value of BuChE inhibition was
included to enhance the range of values for statistical testing.
This would not introduce bias in the results because this choice
was made without consideration of determinants of exposure.
Analysis
We evaluated BuChE inhibition in relation to overall OP/CB
exposure during the past 30 days based on the algorithms
described above. Cumulative OP/CB exposure score was
modelled as a continuous predictor, and per cent change in
BuChE activity from baseline level was modelled as a continuous
outcome (ie, degree of BuChE inhibition per 1-unit increase in
OP/CB exposure score). In another model, we evaluated OP/CB
toxicity score, work activity score and PPE score as separate
predictors of BuChE inhibition. Both models included year of
participation, days since baseline ChE test and age in years as
covariates. Linear regression with robust standard error esti-
mates was used for each of these analyses.
Specific exposure variables were selected for multivariate
analysis based on a priori hypotheses and preliminary bivariate
analyses. Several potential confounding factors were included in
the statistical models, including year of participation, days since
baseline ChE test, age in years, toxicity score, work activity score
and PPE score. Per cent change in BuChE activity from baseline
levels (ie, BuChE inhibition) was used as the main endpoint in
these analyses. Due to wide inter-individual variability in BuChE
activity,32the relative change from baseline levels may be
considered to be more biologically meaningful than the absolute
level. Additionally, analyses were performed evaluating BuChE
activity at follow-up (with baseline BuChE activity included as
a covariate) and with log-transformed BuChE values. We also
evaluated the risk of BuChE depression (>20% inhibition from
baseline levels) in relation to specific exposure variables using
multiple logistic regression adjusting for year of participation,
days since baseline ChE test and age.
Differences were considered to be statistically significant if p
values were <0.05. Analyses were performed using Intercooled
Stata 9.2.
RESULTS
All of the participants in this study were male, and all with
reported ethnicity, except for one participant, were Hispanic/
Latino (table 1). Almost all participants completed the survey in
Spanish (97%). Most participants were younger than 35 years of
age (61%), and approximately half had a primary school
education or less. Many participants had limited experience
handling pesticides; approximately half had been employed as
handlers for 3 years or less. Over three-fourths of our sample had
baseline ChE tests within 60 days prior to their follow-up ChE
Table 1
Demographic characteristics of study participants (N¼154)*
CharacteristicN%
Sex
Male154 100.0%
Race/ethnicity
Hispanic/Latino
White, non-Hispanic
Age in years
18e24
25e34
35e49
$50
Level of education
Did not attend school
Did not complete primary school
Primary school
Middle school
High school
Able to read
In Spanish
In English
Years employed as a pesticide handler
1 year or less
2e3 years
4e5 years
6e10 years
>10 years
Location of home
In town
Rural area, away from orchards
Rural area, near orchards
In/next to orchards
Other
Survey language
Spanish
English
Year of participation
2006
2007
Days since baseline ChE test
#30 days
31e60 days
61e90 days
>90 days
15299.3%
0.7%1
25
69
49
10
16.3%
45.1%
32.0%
6.5%
5 3.2%
12.3%
36.4%
37.0%
11.0%
19
56
57
17
152
48
98.7%
31.4%
22
37
26
22
13
18.3%
30.8%
21.7%
18.3%
10.8%
76
23
20
28
6
50.0%
15.1%
13.2%
18.4%
3.9%
15097.4%
2.6%4
82
72
53.3%
46.8%
95.9%
71.2%
10.5%
12.4%
109
16
19
*Missing values were excluded from percentages.
ChE, cholinesterase.
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test; longer time since baseline testing was associated with
greater BuChE inhibition (b¼?0.145; p<0.001).
Overall, mean BuChE activity at follow-up was significantly
lower than BuChE activity at baseline (p<0.001) (table 2). Mean
BuChE inhibition was somewhat greater among handlers who
participated in 2007 relative to participants in 2006; however,
this difference was not statistically significant (mean (SD) of
?4.8% (13.8) and ?6.6% (8.6) for 2006 and 2007, respectively;
p¼0.34). Approximately 12% of the study sample had >20%
BuChE depression, which was consistent with the frequency of
BuChE depression in the statewide ChE monitoring program in
2006 and 2007.29More cases of BuChE depression were observed
in 2006 than in 2007 (p¼0.086, c2test).
We observed a significant trend toward greater BuChE inhi-
bition with increasing cumulative OP/CB exposure score (table
3). When analysed as separate predictors, OP/CB toxicity score
and PPE score were significantly associated with BuChE inhibi-
tion, and there was a borderline significant association between
work activity score and BuChE inhibition. Results were similar
after several records with high outlying values for toxicity score
or PPE score were excluded (data not shown). There was little
evidence of correlation between OP/CB toxicity score, work
activity score and PPE score in this analysis (correlation coeffi-
cients ranged from ?0.06 to 0.12, p$0.16).
Risk factors for BuChE inhibition
Several particular work activities were associated with greater
BuChE inhibition (table 4) and risk of >20% BuChE depression
(table 5). Unadjusted results are reported in appendices B and C.
On average, handlers who reported mixing/loading pesticides
had 5.25% greater BuChE inhibition than handlers who did not
mix/load pesticides after adjusting for covariates (p¼0.007). In
the adjusted logistic regression analysis, we found that mixer/
loaders were approximately twice as likely to experience BuChE
depression as other handlers. Handlers who reported cleaning
spray equipment had an average of 4.4% greater BuChE inhibi-
tion than handlers who did not clean spray equipment
(p¼0.033), and we observed a nine-fold increased risk of BuChE
depression among handlers who cleaned spray equipment. Some
other work activities and exposures were moderately, although
not significantly associated with BuChE inhibition, including
repairing spray equipment, cleaning out pesticide containers,
cleaning up after pesticide spills, and reported use of azinphos-
methyl, carbaryl or multiple OP/CBs in the last 30 days. There
were no consistent associations of BuChE inhibition and
methods of pesticide application, air blast or tower spraying.
Recency of exposure did not appear to be associated with the
degree of BuChE inhibition. There was some suggestion of an
association between length of spray sessions and BuChE inhi-
bition, with handlers who reported three to four spray sessions
of 8 h or more having on average 6.9% greater BuChE inhibition
than participants who reported no 8 h spray sessions in the last
30 days. However, this association was not statistically signifi-
cant, and we did not see a consistent trend in the relationship
between number of 8 h spray sessions and BuChE inhibition.
Greater BuChE inhibition was observed with increasing age
after adjustment for covariates (p¼0.048). Self-reported health
status was also associated with BuChE inhibition, with partic-
ipants who reported ‘poor’ or ‘fair’ health having 6.4% greater
BuChE inhibition on average relative to participants who
reported ‘excellent’ health status (p¼0.02).
When analyses were repeated using log-transformed BuChE
values, similar associations were observed for each of these
exposures (results not shown).
Factors protecting against BuChE inhibition
Wearing a full-face respirator appeared to protect against BuChE
inhibition. Relative to full-face respirator users, handlers who
wore half-face respirators had approximately 7.0% greater
BuChE inhibition on average (p¼0.034). Half-face respirator
users were almost seven times as likely as full-face respirator
users to experience BuChE depression. Wearing chemical-resis-
tant footwear was also protective against BuChE inhibition.
Handlers who did not wear chemical-resistant footwear had an
average of 11.4% greater BuChE inhibition (p¼0.041), and an
estimated 7.6-fold increased risk of BuChE depression. Relative
to handlers who wore nitrile gloves alone, those who wore
nitrile gloves with cloth gloves underneath had somewhat less
BuChE inhibition, although this difference was not statistically
significant (p¼0.087). In terms of PPE storage, handlers who
reported storing PPE in a locker at work had less BuChE inhi-
bition than handlers who did not use lockers. On average,
handlers who did not use lockers for PPE storage had 7.6%
greater BuChE inhibition, and were 5.8 times as likely to expe-
rience BuChE depression as handlers who did use lockers.
Contrary to expectations, handlers who reported wearing
chemical-resistant aprons had somewhat greater BuChE inhibi-
tion than handlers who did not wear chemical-resistant aprons
(p¼0.119). Also, we did not observe any association between
hand washing practices before breaks during pesticide applica-
tions and BuChE inhibition.
Table 2
Change in serum cholinesterase (BuChE) activity during the OP/CB spray season relative to baseline levels
Per cent change in BuChE activity BuChE depression*
Year NMean (SD)p Valuey
<0.001
0.0016
<0.001
Medianp Valuez
<0.001
0.0076
<0.001
N%
Combined
2006
2007
154
82
72
?5.64% (11.65)
?4.82% (13.77)
?6.58% (8.64)
?3.58%
?2.23%
?5.21%
18
13
5
11.7%
15.9%
6.9%
*>20% BuChE inhibition from baseline activity level.
yPaired t test comparing mean baseline and follow-up BuChE activity.
zWilcoxon signed-rank test comparing baseline and follow-up BuChE activity.
BuChE, butyrylcholinesterase (serum cholinesterase); OP/CB, organophosphate/N-methyl-carbamate pesticide.
Table 3
last 30 days*
BuChE inhibition in relation to OP/CB exposure score in the
Exposure score variable
b Coefficienty
?1.74
?1.50
?1.67
?2.03
95% CIp Value
Cumulative exposure score
Toxicity score
Work activity score
PPE score
?2.61 to ?0.86
?2.93 to ?0.06
?3.39 to 0.05
?3.50 to ?0.57
<0.001
0.041
0.057
0.007
*Multiple linear regression with robust standard error estimates. Adjusted for year of
participation, days since baseline ChE test, and age in years. Toxicity score, work activity
score, and PPE score were all included in a single model when they were analysed as
separate predictors. Analyses were restricted to participants with non-missing values for all
covariates (N¼118).
yDifference in per cent change in BuChE activity from baseline per 1-unit increase in score.
BuChE, butyrylcholinesterase (serum cholinesterase); ChE, cholinesterase; OP/CB,
organophosphate/N-methyl-carbamate pesticide; PPE, personal protective equipment.
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Table 4
Differences in BuChE inhibition in relation to selected exposures after covariate adjustment*
b CoefficientExposure(s)N 95% CI p Value
OP/CB compounds used1
Chlorpyrifos
No
Yes
Carbaryl
No
Yes
Azinphos-methyl
No
Yes
Multiple OP/CBs
No
Yes
119
49
70
119
80
39
119
99
20
119
88
31
Ref
1.69
?3.52 to 6.890.522
Ref
?2.05
?7.54 to 3.440.461
Ref
?3.68
?14.35 to 7.000.496
Ref
?2.50
?8.35 to 3.350.399
Crops treated2
Number of crops treated
1 crop
2 crops
3+ crops
114
83
22
0.651y
Ref
?1.31
?0.93
?6.30 to 3.68
?8.29 to 6.42
0.604
0.8029
Application methods3
Air blast sprayer
No
Yes
Tower sprayer
No
Yes
116
22
94
116
100
16
Ref
0.58
?4.04 to 5.20 0.804
?2.47
Ref
?7.81 to 2.860.360
Handling activities3
Mixing/loading
No
Yes
Entering pesticide storage area
No
Yes
Early re-entry in treated area
No
Yes
Repairing spray equipment
No
Yes
120
39
81
120
86
34
120
98
22
120
106
14
Ref
?5.25
?9.06 to ?1.430.007
Ref
0.71
?4.24 to 5.66 0.777
Ref
0.07
?4.90 to 5.040.979
Ref
?3.16
?8.38 to 2.05 0.232
Cleaning activities3
Cleaning PPE
No
Yes
Cleaning spray equipment
No
Yes
Cleaning pesticide containers
No
Yes
Cleaning pesticide storage space
No
Yes
Cleaning pesticide spill
No
Yes
120
38
82
120
53
67
120
89
31
120
107
13
120
114
Ref
?1.60
?6.60 to 3.400.526
Ref
?4.39
?8.44 to ?0.350.033
Ref
?2.73
?6.58 to 1.130.164
Ref
0.60
?4.49 to 5.69 0.816
Ref
?4.126
?13.22 to 4.980.372
Exposure time2
Days since last exposure
Today
100 0.735y
0.81871.46
?11.11 to 14.04
Continued
Occup Environ Med 2010;67:375e386. doi:10.1136/oem.2009.046391 379
Original article
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