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Determining airborne concentrations of spatial repellent chemicals in mosquito behavior assay systems.

Martin NJ, Smith PA, Achee NL, DeLong GT - PLoS ONE (2013)

Bottom Line: Significantly higher levels of airborne DDT were measured in the chamber containing textiles treated with DDT compared to chambers free of AI.The mean DDT air concentrations in these two huts over a period of four days with variable ambient temperature were 0.74 µg/m(3) (n = 17; SD = 0.45) and 1.42 µg/m(3) (n = 30; SD = 0.96).The results from laboratory experiments confirmed that significantly different DDT exposure conditions existed in the three-chamber system establishing a chemical gradient to evaluate mosquito deterrency.

View Article: PubMed Central - PubMed

Affiliation: Viral and Rickettsial Diseases Department, U. S. Naval Medical Research Center, Silver Spring, Maryland, United States of America ; Preventive Medicine and Biometrics Department, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America.

ABSTRACT

Background: Mosquito behavior assays have been used to evaluate the efficacy of vector control interventions to include spatial repellents (SR). Current analytical methods are not optimized to determine short duration concentrations of SR active ingredients (AI) in air spaces during entomological evaluations. The aim of this study was to expand on our previous research to further validate a novel air sampling method to detect and quantitate airborne concentrations of a SR under laboratory and field conditions.

Methodology/principal findings: A thermal desorption (TD) gas chromatography-mass spectrometry (GC-MS) method was used to determine the amount of dichlorodiphenyltrichloroethane (DDT) in samples of air. During laboratory experiments, 1 L volumes of air were collected over 10 min intervals from a three-chamber mosquito behavior assay system. Significantly higher levels of airborne DDT were measured in the chamber containing textiles treated with DDT compared to chambers free of AI. In the field, 57 samples of air were collected from experimental huts with and without DDT for onsite analysis. Airborne DDT was detected in samples collected from treated huts. The mean DDT air concentrations in these two huts over a period of four days with variable ambient temperature were 0.74 µg/m(3) (n = 17; SD = 0.45) and 1.42 µg/m(3) (n = 30; SD = 0.96).

Conclusions/significance: The results from laboratory experiments confirmed that significantly different DDT exposure conditions existed in the three-chamber system establishing a chemical gradient to evaluate mosquito deterrency. The TD GC-MS method addresses a need to measure short-term (<1 h) SR concentrations in small volume (<100 L) samples of air and should be considered for standard evaluation of airborne AI levels in mosquito behavior assay systems. Future studies include the use of TD GC-MS to measure other semi-volatile vector control compounds.

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Related in: MedlinePlus

Box-and-whisker plot of DDT air concentration in samples collected from the treatment (Fig. 1 B), mosquito introduction (Fig. 1 C), and control (Fig. 1 D) chambers of the laboratory system (black circles denote samples above or below the 90% and 10% percentiles, respectively).Nylon fabric treated with 0.09 g/m2 4, 4′ DDT was prepared each day and placed on 50% of the wall surface area of the treatment chamber. The median airborne DDT concentration was significantly different between days (Kruskal-Wallis one-way ANOVA; H = 35.461; P<0.001). The DDT air concentration measured for the treatment chamber was significantly higher than the levels measured in the mosquito introduction and control chambers (Tukey post hoc; p<0.05 for both comparisons).
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pone-0071884-g004: Box-and-whisker plot of DDT air concentration in samples collected from the treatment (Fig. 1 B), mosquito introduction (Fig. 1 C), and control (Fig. 1 D) chambers of the laboratory system (black circles denote samples above or below the 90% and 10% percentiles, respectively).Nylon fabric treated with 0.09 g/m2 4, 4′ DDT was prepared each day and placed on 50% of the wall surface area of the treatment chamber. The median airborne DDT concentration was significantly different between days (Kruskal-Wallis one-way ANOVA; H = 35.461; P<0.001). The DDT air concentration measured for the treatment chamber was significantly higher than the levels measured in the mosquito introduction and control chambers (Tukey post hoc; p<0.05 for both comparisons).

Mentions: The median concentration of airborne DDT was not significantly different in the treatment chamber between the three days (Kruskal-Wallis ANOVA; H = 5.190; p = 0.075) indicating that a similar concentration of airborne DDT was generated during the three-day experiment. However, the median concentration of airborne DDT was significantly different between the three chambers (Fig. 4; Kruskal-Wallis ANOVA; H = 35.461; p<0.001) with median concentration significantly higher in the treatment chamber compared to the central and control chambers (Tukey post hoc; p<0.05).


Determining airborne concentrations of spatial repellent chemicals in mosquito behavior assay systems.

Martin NJ, Smith PA, Achee NL, DeLong GT - PLoS ONE (2013)

Box-and-whisker plot of DDT air concentration in samples collected from the treatment (Fig. 1 B), mosquito introduction (Fig. 1 C), and control (Fig. 1 D) chambers of the laboratory system (black circles denote samples above or below the 90% and 10% percentiles, respectively).Nylon fabric treated with 0.09 g/m2 4, 4′ DDT was prepared each day and placed on 50% of the wall surface area of the treatment chamber. The median airborne DDT concentration was significantly different between days (Kruskal-Wallis one-way ANOVA; H = 35.461; P<0.001). The DDT air concentration measured for the treatment chamber was significantly higher than the levels measured in the mosquito introduction and control chambers (Tukey post hoc; p<0.05 for both comparisons).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3756037&req=5

pone-0071884-g004: Box-and-whisker plot of DDT air concentration in samples collected from the treatment (Fig. 1 B), mosquito introduction (Fig. 1 C), and control (Fig. 1 D) chambers of the laboratory system (black circles denote samples above or below the 90% and 10% percentiles, respectively).Nylon fabric treated with 0.09 g/m2 4, 4′ DDT was prepared each day and placed on 50% of the wall surface area of the treatment chamber. The median airborne DDT concentration was significantly different between days (Kruskal-Wallis one-way ANOVA; H = 35.461; P<0.001). The DDT air concentration measured for the treatment chamber was significantly higher than the levels measured in the mosquito introduction and control chambers (Tukey post hoc; p<0.05 for both comparisons).
Mentions: The median concentration of airborne DDT was not significantly different in the treatment chamber between the three days (Kruskal-Wallis ANOVA; H = 5.190; p = 0.075) indicating that a similar concentration of airborne DDT was generated during the three-day experiment. However, the median concentration of airborne DDT was significantly different between the three chambers (Fig. 4; Kruskal-Wallis ANOVA; H = 35.461; p<0.001) with median concentration significantly higher in the treatment chamber compared to the central and control chambers (Tukey post hoc; p<0.05).

Bottom Line: Significantly higher levels of airborne DDT were measured in the chamber containing textiles treated with DDT compared to chambers free of AI.The mean DDT air concentrations in these two huts over a period of four days with variable ambient temperature were 0.74 µg/m(3) (n = 17; SD = 0.45) and 1.42 µg/m(3) (n = 30; SD = 0.96).The results from laboratory experiments confirmed that significantly different DDT exposure conditions existed in the three-chamber system establishing a chemical gradient to evaluate mosquito deterrency.

View Article: PubMed Central - PubMed

Affiliation: Viral and Rickettsial Diseases Department, U. S. Naval Medical Research Center, Silver Spring, Maryland, United States of America ; Preventive Medicine and Biometrics Department, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America.

ABSTRACT

Background: Mosquito behavior assays have been used to evaluate the efficacy of vector control interventions to include spatial repellents (SR). Current analytical methods are not optimized to determine short duration concentrations of SR active ingredients (AI) in air spaces during entomological evaluations. The aim of this study was to expand on our previous research to further validate a novel air sampling method to detect and quantitate airborne concentrations of a SR under laboratory and field conditions.

Methodology/principal findings: A thermal desorption (TD) gas chromatography-mass spectrometry (GC-MS) method was used to determine the amount of dichlorodiphenyltrichloroethane (DDT) in samples of air. During laboratory experiments, 1 L volumes of air were collected over 10 min intervals from a three-chamber mosquito behavior assay system. Significantly higher levels of airborne DDT were measured in the chamber containing textiles treated with DDT compared to chambers free of AI. In the field, 57 samples of air were collected from experimental huts with and without DDT for onsite analysis. Airborne DDT was detected in samples collected from treated huts. The mean DDT air concentrations in these two huts over a period of four days with variable ambient temperature were 0.74 µg/m(3) (n = 17; SD = 0.45) and 1.42 µg/m(3) (n = 30; SD = 0.96).

Conclusions/significance: The results from laboratory experiments confirmed that significantly different DDT exposure conditions existed in the three-chamber system establishing a chemical gradient to evaluate mosquito deterrency. The TD GC-MS method addresses a need to measure short-term (<1 h) SR concentrations in small volume (<100 L) samples of air and should be considered for standard evaluation of airborne AI levels in mosquito behavior assay systems. Future studies include the use of TD GC-MS to measure other semi-volatile vector control compounds.

Show MeSH
Related in: MedlinePlus