Blooming of insecticides from polyethylene mesh and film

Figures & data

Figure 1. Insecticidal mesh installed as ITWLs in community dwellings as part of the field trial: (a) indoor installation of mesh in a traditional hut, (b) green (0.29 wt-% alphacypermethrin) mesh as an insecticidal wall lining in a western style brick house.

Figure 2. WHO bioassay tube test set up for evaluating the residual efficacy of insecticidal mesh samples.

Figure 3. Fluorescence images recorded on filaments of insecticidal Netlon mesh samples. (a) alphacypermethrin; (b) fipronil, and (c) chlorfenapyr.

Table 1. WHO tube bioassay results for insecticidal mesh impregnated with alphacypermethrin, 60 months after installation in the field trial.

Mesh colour		Number	Knock down	Alive	Dead	Knock down	Mortality
(Insecticide, wt-%)	Sample	mosquitoes	60 min	24 h	24 h	%	%
White	A16	23	0	23	0	0	0
(None)	B2	25	0	25	0	0	0
	B6	25	0	25	0	0	0
	B14	24	0	24	0	0	0
	B17	25	0	24	1	0	4
Green	A10	26	26	0	26	100	100
(0.29)	A15	24	24	0	24	100	100
	A20	25	23	1	24	92	96
	B3	24	24	0	24	100	100
	B7	25	25	0	25	100	100
	B11	25	25	0	25	100	100
	B19	24	23	0	24	96	100
Orange	A3	27	27	0	27	100	100
(0.47)	A7	25	24	0	25	96	100
	A11	24	24	0	24	100	100
	A19	25	25	0	25	100	100
	B4	25	25	0	25	100	100
	B8	24	24	0	24	100	100
	B12	24	24	0	24	100	100
	B20	27	27	0	27	100	100
Tube control	Control	25	0	25	0	0	0

Figure 4. FTIR-ATR spectra. (a) Comparing the spectra for the neat chlorfenapyr powder to that for virgin HDPE. (b) Change in the FTIR-ATR spectra with ageing time at 40°C for the chlorfenapyr-containing HDPE film compared to the neat spectrum obtained for the neat insecticide powder.

Figure 5. Normalised insecticide contents of films as a function of ageing time at 40°C. The transmission data indicate compositions estimated from spectra recorded after rinsing the films with acetone. The FTIR-ATR data provide a relative indication of the accumulation of the insecticides on the surface of the films. The dotted lines indicate error bands corresponding to one standard deviation above and below the mean.

Table 2. Summary of the estimates of insecticides accumulated at the surface and retained internally in the polyethylene film samples.

Insecticide	Polymer	Retained	Surface (outside)	Surface (inside)	Total
Alphacypermethrin	LDPE	0.111 ± 0.046	0.30 ± 0.10	0.059 ± 0.130	0.469
	LDPE/HDPE	0.236 ± 0.051	0.23 ± 0.05	0.038 ± 0.036	0.508
	HDPE	0.838 ± 0.083	0.035 ± 0.037	0.011 ± 0.005	0.884
Chlorfenapyr	LDPE	0.145 ± 0.011	0.35 ± 0.16	0.31 ± 0.09	0.811
	LDPE/HDPE	0.161 ± 0.006	0.49 ± 0.09	0.45 ± 0.11	1.099
	HDPE	0.228 ± 0.009	0.39 ± 0.07	0.32 ± 0.04	0.944
Fipronil	LDPE	0.652 ± 0.061	0.17 ± 0.04	0.15 ± 0.03	0.983
	LDPE/HDPE	0.615 ± 0.048	0.19 ± 0.04	0.15 ± 0.04	0.963
	HDPE	0.714 ± 0.058	0.15 ± 0.04	0.12 ± 0.02	0.981

Note: The total amount was calculated as the sum of the retained and the apparent surface fractions.

Figure 6. Optical images of the surfaces of polymer films after long-term ageing. (a) alphacypermethrin in the 1:1 m/m LDPE/HDPE film. LDPE films that contained (b) alphacypermethrin, (c) chlorfenapyr and (d) fipronil.

Figure 7. Sum spectra and SEM-EDX images of HDPE film surfaces. (a) neat HDPE film; (b) alphacypermethrin; (c) fipronil, and (d) chlorfenapyr. The false green colour indicates elemental distribution of chlorine detected by EDX.

Figure 8. Radial scattering curves (left) and 2D-WAXS patterns (right) of HDPE films containing insecticides.