The first transmission of the mosquito-borne Zika virus in the continental U.S. was discovered August 2016 in Miami-Dade County, Florida. Efforts have been mounted to eradicate the mosquito vectors; however, some of these efforts, including insecticide sprays, have been viewed with skepticism by local communities due to limited knowledge and inconsistent information concerning the fate of the insecticide and the subsequent ecological and human health impacts. Thus, there are growing concerns about the human health and ecological impacts of insecticide spraying, especially Naled spraying in Miami. Those against Naled's use emphasize that Naled has negative health and ecosystem impacts impacting honeybees and birds and was banned by the European Union in 2012. Those proposing continued use of Naled cite studies that suggest it is safe to use according to specifications (in ultra-low volume). The objective of this project is to develop an understanding of the environmental fate of Naled by conducting laboratory-controlled experiments supplemented by full-scale opportunistic monitoring during aerial spray activities.
Specifically, this study will evaluate the impact of soil and water on the persistence of Naled and its by-product, Dichlorvos, both of which have insecticidal properties. The laboratory study will be supplemented with sampling conducted before and after the spray of Naled in the coming summer season, to identify potential areas of accumulation within the coastal intertidal zone. The PI's team will evaluate the persistence of environmental insecticides; specifically, they will evaluate the impacts of sediment properties on the fate of Naled and Dichlorvos and assess whether the intertidal zone serves as a reservoir of insecticide accumulation. The existing literature sheds little light on the fate of Naled and degradation by-products in natural settings. Moreover, scant data are available on the impacts of environmental matrices, especially sediments, on the persistence of Naled. The PI will evaluate Naled as a model organophosphate insecticide which is currently the insecticide of choice for Zika larvae eradication. They hypothesize that the persistence of Naled in the environment varies across environmental media, e.g., shorter persistence in beach sands than the soils with higher organic content. They further hypothesize that Naled from the aerial sprays in coastal areas will accumulate in the intertidal zone, allowing for potential exposures nearshore. Results from this study can be used to quantify decay rates for Naled under different soil conditions. These decay rates will be validated against measurements collected during full-scale spray activities. Results can be incorporated into fate and transport models that simulate Naled persistence in the environment. The Miami-Dade community will benefit from the translation of the knowledge gained from this project to mosquito control decisions by Miami-Dade County's Mosquito Control Division, and from assessments of human health risks by the Miami-Dade Department of Health.
