Pesticides: Deadly persistence

THE air and water of Davao City's Panigan-Tamugan and Talomo-Lipadas watersheds may not be as pristine as they seem.

A study conducted by Interface Development Interventions Incorporated (IDIS) revealed that 18 pesticides and breakdown products have been detected in the area's air and that 17 pesticides and breakdown products were detected in the area's water. Traces of 12 banned pesticides or breakdown products were found in both the air and water. Banned pesticides found to be polluting the area are Alrdin and Dieldrin, DDT, Gamma Chlordane and Lindane. Researchers were unable to pinpoint the exact sources of the pesticides but plantations upstream are most likely the culprits.

IDIS revealed the results of their study last Monday in the Board Room of Ateneo de Davao University's Jacinto campus.

Dr. Romeo Quijano, adviser for the study, explained the presence of the banned pesticides as they were classified as Persistent Organic Pollutants (POPs), which are chemicals that can take years before they fully degrade.

The pesticide residue, as explained by the research, spreads through natural environmental occurrence, as traces of the pesticide can be found in surface water, which can then reach other places by evaporating and then being deposited in land once more through rainfall. This cycle, coupled with pesticide's persistent nature, makes it a dangerous presence in a land dominated by agricultural activity, such as the Davao region.

It is alarming then, that two of Davao's watersheds are polluted with pesticide sentiments that cannot be easily detected by plain human senses. People could be ingesting large amounts of pollutants everyday without even realizing it.

Take for example, the amount of pollutants IDIS found to be in the air. IDIS set up sampling stations in three schools to identify potential threats of pesticide pollution in the air. Using a drift catcher, IDIS found that the Baguio High School of Agriculture in Tawantawan, Vinzons Elementary School in Manuel Guianga and the Baracayo Elementary School in Daliaon Plantation were under great risk.

Traces of seven of the pesticides found in the air were found to have exceeded the Reference Exposure Level (REL) at least once during the 24 day sampling period. The REL determines the "acceptable" amount of exposure of people to pesticides, and the air surrounding the three schools was found to be polluted beyond what the RELs deem acceptable.
Moreover, the samples rarely contained traces of just one pesticide. Findings of the study show that there is an average of at least two kinds of pesticides present in the air collected from the sampling stations in the schools, while the air in Baracayo Elementary School yielded traces of a whopping eight pesticides, seven of which are banned.

The multiple pollutants cause a threat which researchers are unable to draw conclusions upon, as there have been no studies to determine risk from exposure to multiple pesticides. Anne Fuertes, executive director of IDIS noted that it is possible that in the presence of other pesticides, a single pesticide may react and yield greater toxicity. Taking into account the persistent nature of the pesticides, it is even more fearful that people are subject to long-term exposure to the pesticides.

Even the watershed's rivers showed long-term pollution from the pesticides. Over an eight-month period of water sampling, the Tamugan and Panigan Rivers showed the presence of six and seven pesticides, respectively. Four pollutants were also detected in the Panigan-Tamugan junction while six pollutants were present in the Wines-Gumalang river junction. Finally the Gumalang River yielded the highest number of pollutants with 11 pesticides detected. Risk assessment could not be made for pesticides in water, however, as only short term studies on it have been made.

Even without risk assessment, however, pesticides level in air has already been shown to exceed RELs. Moreover, the traces of persistent pesticides in the water put the surrounding areas at risk of exposure to multiple pesticides from multiple sources. For a region that thrives much on agriculture, the amount of pollution in the watershed poses a great threat to the production of crops, but more importantly, the amount of pollution poses a great threat to its people.

The people in the region, especially those living close to the sources of pollution are vulnerable and IDIS has come up with policy recommendations to counter these problems.

IDIS will be moving on to long-term monitoring of the polluted areas to come up with more comprehensive data for policy makers. Until the policy makers make a definite move to clean up the pesticide-laden practices of farmers, however, the seeming clean air and water around the Talomo-Lipadas and Panigan-Tamugan will remain a threat to the communities surrounding them.
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