Assessing urban atmospheric chemistry effects on the environmental fate of current-use pesticides in Harris County, TX
Abstract
Harris County Public Health authorities in Houston, TX release pesticides directly in to the atmosphere to control adult mosquito populations and reduce the threat of mosquito-borne diseases. Pesticides registered with the EPA for this purpose are called adulticides. Permethrin and Malathion are the primary adulticides used in Houston and are typically sprayed as aerosols at night using ULV (ultra low volume) sprayers mounted to a truck. Malathion is sprayed as a pure solution while Permethrin is sprayed as a mixture with a mineral oil and PBO, a synergistic compound used to increase the toxicity of the adulticide. During the summers of 2013, 2016 and 2017, atmospheric particulate matter (PM) samples were collected in multiple size fractions (TSP, PM2.5 and PM1.0) at adulticide application and downwind sites in Houston. Nighttime atmospheric half-lives of Malathion were determined to be 40-90% shorter, which is driven by the high NOx pollution in Houston that supports nighttime oxidation chemistry (via nitrate radical and ozone) known to oxidize Malathion to Malaoxon. This increased degradation rate raises concerns of the effectiveness of using Malathion in heavily NOx polluted atmospheres because Malaoxon is less effective as an adulticide and is more toxic to humans. Moreover, results show higher atmospheric concentrations of Malaoxon than Malathion in the fine PM. This suggests Malathion is volatilizing from the ULV aerosols, and subsequently condensing and accumulating to the smaller particle size fraction, while undergoing nighttime oxidation in potentially both the gas and particle phases. In contrast, results show Permethrin is accumulating in the larger particle size fraction than in the smaller particle size fractions, which suggests the use of mineral oil heavily influences the environmental fate and transport of adulticides. Additionally, the sum of pesticide mixtures represents over 1% of aerosolized organic matter (OM) at both the application and the downwind sites, which has serious health implications. Lastly, atmospheric concentrations of adulticide mixtures at the application site are 5-10 times higher than at the downwind site, which represents some of the highest levels of current-use pesticides in an urban area.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGH43D1234G
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0240 Public health;
- GEOHEALTH