Researchers have called for measures to restrict the harvest of crustaceans and mollusks from Taft River in Eastern Samar due to high levels of heavy metals found in the flesh of certain crabs and snails.
In the August 4 edition of the Philippine Journal of Science, researchers from the Northwest Samar State University in Calbayog City said the meat of the four mollusk and two crustacean species harvested from the Taft River contained high levels of arsenic, copper, nickel, chromium, lead and zinc “all of which were beyond the acceptable limits for human consumption set by authorities.” The mollusk species are snails called locally as bebe, tangili, tunway and sihi.
Taft River had received drainage water and sediments from the Bagacay Copper Mine, which was abandoned in 1992 after more than three decades of operation. The government started rehabilitating the abandoned copper mine even before the COVID-19 pandemic and the local government unit is trying to promote the river as a tourist attraction.
Prolonged exposure to heavy metals such as lead, mercury and arsenic could be life threatening and can cause irreversible damage since these bind with body cells that prevent human organs from functioning properly.
The report said arsenic concentration in certain seafoods was 4,000 times higher than the allowable limit for human consumption while concentration of copper in two mollusk species was higher than the critical limit, with the highest level at 195 times more. The concentration of nickel, chromium, manganese and zinc in certain seafood and snail species were far higher than the critical limit.
“The HM (heavy metal) concentrations in water samples obtained from the lower and the middle sections of the river were lower than the DENR-EMB (Department of Environment and Natural Resources-Environmental Management Bureau) limit set for class C,” the research paper showed.
“In contrast, the water samples from the upper section of the river have higher values of As (arsenic), Pb (lead), and Cu (copper) than those samples from the lower and middle section of the river and these values are above the DENR-DAO (DENR Administrative Order) 2016-08 limit for class C,” it added.
Heavy metal concentration in the flesh of tested species was probably due to their feeding habits. The researchers said the flesh of tested species were washed several times before testing.
“All these mollusk species have HI (hazard index) values between 47.07–58.33, which are considered to be hazardous to human health. The consumption of T. telescompium and S. serrata for crustaceans will result in the highest TCR (target cancer risk) for adults and HI as compared to other species, which is attributed to a relatively high THQ (target hazard quotient) due to high concentration of As in its flesh,” it said
The researchers said the initial results of their research on heavy metal accumulation in the mollusks and crustaceans “warrant further investigation with respect to their different growth stages and seasonal variations in the area. Given the high concentration of HM in these species, legislation for harvest restriction is recommended,” it added.
