DDTs in Soils Affected by Mosquito Fumigation in Belize

Abstract

DDTs were sprayed extensively in Belize to combat malaria but widespread use ceased after 1997. To determine if DDTs still persist in Belize's soils, 23 composite soil samples were collected from each of the two towns of Dangriga and Punta Gorda. Dichlorodiphenyltricholoroethane (DDT) and its breakdown products dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD) were the only organochlorine compounds detected in the soils. Results show that DDTs are transferred to the soil environment as a result of spraying houses and that the pesticides still persist in soils in southern Belize after more than 10 years of non-use. Sprayed lots had DDT concentrations up to 240 μg/kg in Dangriga and up to 410 μg/kg in Punta Gorda. All unsprayed lots had below detection limit concentrations, with the exception of two sites in Punta Gorda. Hot spot analysis in GIS indicates that significant spatial variability exists in detected concentrations of DDTs, which has implications for extrapolation of local data. Belize currently has no guidelines for determining risk of DDTs to human health and soil cleanup, but soil cleanup guidelines employed by foreign governmental entities such as the Netherlands and California show that all detected pesticide concentrations in this study are below mandated concentrations of concern for the residential areas of these regions. However, since exposure scenarios may be different in Belize, it is recommended that the Belize Ministry of Health conducts a risk analysis to ascertain if the concentrations of DDTs in sprayed areas pose a risk to the inhabitants of the two towns.

Keywords:

• DDT
• soil quality
• Belize
• GIS

Acknowledgements

We would like to thank Matthew Schwartz and Carl Mohrherr for reviewing Michael F. Somerville's thesis. Nathan McKinney and Kristal Walsh were kind enough to assist with some GIS applications. Raid Amin advised on the use of statistical methods. Thanks also to Martin Alegria and Anthony Mai from the Belize Department of the Environment for providing in-town transportation and assisting with sampling and site selections. This study was made possible through financial support to Michael F. Somerville from the University of West Florida Scholarly and Creative Activities Committee. The original version of this manuscript greatly benefited from the comments by anonymous reviewers.