Ratio of DDT/DDE in the all saints bay, brazil and its use in environmental management

Abstract

DDT degrades to DDE and the ratio of DDT/DDE can be used as a rough estimate of the period of its application, if the half-life of DDT for the specific environment is known. A cross-sectional survey was conducted in SH summer 1994/95 for several organochloride (OC) residues in 13 intertidal sites of the All Saints Bay, using sediments, crabs and three species of local bivalves with different feeding habits as indicators. The quantified compounds were: DDT, DDE, DDD, HCB, γ-HCH, Aldrin, Dieldrin and Endrin. All concentrations found were below limit of regulatory action. Highest levels were found in the Aratu Industrial Centre area, in the Subaé estuary and the Itaparica Channel, where palm oil nursery exists. From the eight compounds DDE presented the highest levels (44 ng/g wet wt in B.exustus) and B.exustus the highest bioconcentration factors. Comparing these data with equivalent ones of 1985, increases have been observed at all sites, except where an oil refinery operates in restricted area. DDT/DDE ratio for the sediments in some sites were 0.91 or higher, indicating probable DDT use in the last 5 years. Regular consumption of these edible molluscs lead to daily ingestion of total DDT compounds between 75 to 589 ng/d. Official use of DDT in 1985 for malaria campaign and recent use, notwithstanding prohibition, seem to be the reason for the observed increases in levels.