Evangeline C. Santiago
University of the Philippines

The UNU monitoring of POPs in the East Asian hydrosphere project aims to gather data on the levels of POPs pesticides in coastal and river waters that can be used to assess the level of POPs pesticide pollution and to recommend policies for management of these compounds in the region. Scientists from a network of laboratories in eight countries in the region were provided training to monitor these pesticides using a harmonized method and analytical equipment to come up with comparable regional data.

In the Philippines, the reporting of the results was a major challenge. POPs pesticides are extremely hydrophobic substances and are expected to be present in natural waters in trace concentrations. Most of the pesticides analyzed in many samples obtained in rivers from the Philippines were either not detected or were detected in extremely small amounts. The task of deciding whether the trace result is significant or not, involved many experiments to determine the Method Detection Limit for each of the pesticide. Since the analytical method adopted for the project is liquid-liquid extraction and florisil clean-up which involved many steps that can introduce losses in the recovered analyte concentrations, the question on whether to adopt the MDL as calculated and defined by the IUPAC or EPA (MDL = the concentration equivalent to 3x Standard Deviation of blank or low level spike) or the MDL that takes into consideration the recovery of the analyte (MDL= t (n. 95% C.I) x Standard Deviation of the lowest spike concentration that gives 100 ± 40%Recovery) is also considered.

In this report, the pesticides that were found above the calculated MDLs in water samples in Pangasinan and Laguna River systems from 2002-2004 are presented.