It was almost certainly poisonous puffer fish—and not pesticides—that killed seven people and sickened 69 others in the Siem Reap area in late June, an environmental engineer with the World Health Organization said Friday.
While a first round of tests found traces of pesticides in the fish, further testing revealed the levels were so low as to be insignificant, said the engineer, Steven Iddings.
He said 12 samples of various kinds of fish from the Ou Cheak River in Siem Reap province were subjected to more sophisticated lab tests in Japan and Australia.
The Australian lab, which specializes in pesticide testing, subjected each of the 12 samples to tests for 39 different pesticides, performing a total of 468 tests.
Only six of those tests came up positive for pesticides, and that was for amounts so low as to be harmless, Iddings said.
Twelve samples were also sent to a lab in Japan that specializes in fish. That lab found that most varieties of fish submitted—including catfish and shrimp—were harmless.
But the samples also included puffer fish, an Asian delicacy that can be poisonous if prepared improperly, Iddings said. The Japanese lab determined that the puffer fish samples were “definitely” toxic, he said.
Iddings said health officials initially suspected pesticides because the first tests were simple screening tests, intended to detect the presence of organo-phosphates, a common ingredient in pesticides.
The second tests showed the amounts were so low that “pesticides almost certainly played no role in those poisonings,” he said.
But health officials do not have an explanation as to why so many people may have eaten fish known to be poisonous and why the rate of poisonings would be higher this year than past years.
Fisheries specialist Touch Seang Tana said the fish may have become poisonous from ingesting naturally occurring biotoxins. He said the government should conduct an extensive survey of Cambodia’s lakes, rivers and reservoirs, testing water and fish samples for toxins.
“I’m very concerned about this,” he said.