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Special Issue on Malaria in Southern Africa

Blooming of insecticides from polyethylene mesh and film

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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 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 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.

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.

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 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.

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.

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 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 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.

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