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Level of exposure
To assess the level of exposure and to quantify the exposureresponse relation,
50 cotton growers in three groups from clusters in Gaochen and Langfang
counties were selected for study in 1987 and 1988. Subjects had no history of
exposure to pyrethroids in the week before the investigation, and all were
confirmed to be healthy by interview and physical examination. Each subject
sprayed pyrethroids in the cotton field for 5 h/day using single-nozzle pressure
sprayers for I day in group 1, then for 3 days in groups 2 and 3,
consecutively (Table 1). All subjects were monitored by project personnel
throughout the spraying.
Air samples were collected from subjects in groups I and 2 using DuPont
personal samplers with an air flow of 2 L/min throughout the 5 h of spraying;
respiratory exposure (g/h) was calculated as air concentration at breathing
zone (g/m3) times ventilation volume (0.01 m3/min) times 60 minutes.
Deltamethrin and fenvalerate in the air were collected on polyester filters.
Meteorological conditions were monitored with respect to temperature, relative
humidity, wind speed, wind direction, and atmospheric pressure.
Five-layer gauze pads (5 x 5 cm), pretreated with n-hexane and Soxhiet's
extractor, were used to measure dermal exposure of the head, chest, back,
forearms, thighs, legs, hands, and feet of each subject in groups I and 2. Dermal
exposure was estimated as the concentration in one gauze pad (g/cm2) times
total body surface area (cm2) times percentage of body area sprayed divided
by spraying time (h). Total exposure was also calculated, as respiratory exposure
level plus dermal exposure level per kilogram of body weight.
Table 1. Controlled exposure of subjects to pyrethroids during spraying.
No. of
subjects
Amount of
pyrethroid
(mL ± SD) Dilution
3 12 428±90 1:1000(D) 5x3
Note: D, deltamethrin; F, fenvalerate; M, methamidophos; SD, standard deviation.
51
Spraying time
(h/day x days)
Group
I
a 6 100±14 1:1250(D) 5x1
b 6 117±103 1:2000(D)+1:600(M) 5x1
c 6 96±77 1:1250(F) 5x1
2
a 5 376±30 1:1000(D) 5x3
b 5 420±45 1:1000(D) +1:600(M) 5x3
c 5 376±50 1:1 000(F) 5x3
d 5 364 ± 64 1:1 000 (F) + 1:600 (M) 5 x 3