Evangeline C. Santiago
NPC from the Philippines
Natural Sciences Research Institute
University of the Philippines
The river systems of two important fish- producing and
agricultural provinces in the Philippines were selected as study areas for the
second three-year phase (2002-2005) of UNU Monitoring project in the Philippines.
The monitoring aims to determine if significant residues of organochlorine
pesticides are present in the river waters and sediments that could potentially
contaminate the fish produced in the provinces.
The first year monitoring in Laguna Rivers detected traces of
BHC, aldrin, trans and cis
chlordane, dieldrin and DDT and endrin
aldehyde in water samples at the levels near the
Method Detection Limits during the first sampling and significant levels of dieldrin (0.03-0.13 ppb) during the second sampling. Aldrin was
detected in most Pangasinan Rivers at levels (0.063
ppb) higher than the MDL during the first sampling. During the second sampling, dieldrin was most significant (0.04-0.09 ppb) in all Pangasinan sites and endrin aldehyde (0.27 ppb) in one river site.
The second year monitoring showed only traces of trans and cis chlordane in most
river waters from both provinces during the first sampling. Traces of dieldrin, p,p’DDT
and trans-nonachlor were detected during the second
sampling in addition to the chlordanes. However, the
concentrations detected were all below the MDLs.
It is extremely difficult to derive conclusions from the
monitoring results. The extraction method and the GC/MS method differed for the
first and second years. The considerable decrease in the OCPs
detected in the second year maybe due to an improvement of the analytical
method or maybe due to natural loss of the pesticides with time.