Even though the National Bureau of Investigation (NBI) ruled that pesticides caused the death of 27 children in Bohol last week — not traces of poisonous cyanide in the tuberous plant — Villar, who serves as the vice chairman of the Senate committee on agriculture and food, said the DOH and the Bureau of Plant Industry (BPI) should come out with their respective pronouncements on the safe consumption of cassava.
The deaths were initially attributed to naturally occurring cyanide in cassava, which was used to make the snacks eaten by the children, but after completing its investigation, the NBI determined it was pesticide used by farmers that caused the fatal poisoning.
"I think the health and food authorities should settle the score regarding the edibility of cassava. We should once and for all quell speculations regarding this staple food of Filipinos. The public deserves to know," Villar said.
He expressed concern that the incident would damage the local cassava industry as fears of poisoning had caused a decline in demand for the root crop, known locally as kamoteng kahoy or balinghoy.
"We owe it to them also to declare cassava safe if it is really safe to eat. Cassava, after all, is an important agricultural crop of the country," Villar said.
Based on the NBI’s report, the poison that killed the children was an organophosphate insecticide called coumaphos, found in the cooking paraphernalia of a local cassava vendor as well as the internal organs of two schoolchildren who were poisoned.
However, the NBI findings are separate from those of the DOH.
"So far, only the NBI has absolved cassava as the culprit in the Bohol poisoning tragedy. The (DOH) and food authorities should also come up with their own official statements regarding cassava," Villar said.
He noted that the DOH and the BPI have so far only provided instructions on how to safely prepare cassava for cooking.
"While preparation and cooking tips come in handy, the public needs to be informed whether cassava per se poses hazards or danger to their health. We should put to rest their concerns and fears about this matter."
Last March 13, one of two local vendors who sold the deadly cassava snacks in Bohol admitted using flour made from a variety of cassava that had a higher cyanide content than normal, the NBI said.
In a telephone interview, NBI director Reynaldo Wycoco said the vendor, 68-year-old Ana Luyong, told investigators she had used flour made from white cassava that grew in her backyard.
He said the cyanide content of white cassava is between 330 to 360 parts per million while yellow cassava is between 30 to 60 ppm. The human body can tolerate a maximum cyanide level of 120 ppm.
Luyong, who was confined in a hospital after she ate some of the cassava sweets she prepared, may be charged with reckless imprudence resulting in homicide if it is proven that she knew the dangers of using flour made from white cassava, he added.
The Plant Resources of Southeast Asia (PROSEA) earlier said a cassava’s tubers (roots) and leaves contain hydrocyanic acid (HCN).
If the amount of HCN is more than the body can handle, this chemical compound can kill man and animal alike, PROSEA said yesterday.
All cassava cultivars (cultivated varieties) contain cyanogenic glucosides, according to PROSEA. Glucoside content such as HCN in the central part of fresh storage roots varies from 30 to 200 milligram (mg) per kilogram (kg), and can sometimes even be more.
"Small amounts are tolerable, but man should not consume more than one mg HCN per kg body weight per day," advised PROSEA, an international project focused on the documentation of information on plant resources of Southeast Asia.
High nitrogen and low potassium makeup in soil increases the glucoside content. The first rains after a dry season can also cause a large increase in glucoside.
"If the cells of storage roots are crushed, glucosides and enzymes make contact and the HCN is split off. This is the key to methods of removing HCN. The volatile HCN should be allowed to escape," PROSEA said.
DOH epidemiologist Dr. Manuel Mapue said cyanide could be produced by certain decomposing elements in the soil.