The Council of Agriculture (COA) late on Wednesday questioned the methodology used and the conclusions reached by an investigative report published in the Chinese-language Business Weekly that alleged that up to 70 percent of the dairy products on the market contained potentially harmful drug residues.
The report said it found pyrimido Azepine, plasticizers, metabolites of estrogen and contraceptive drugs, and metabolites of tranquilizer and anti-depressant drugs in the samples of nine milk products, several produced by well-known food companies, including Uni-President and Wei Chuan, which are already embroiled in the edible oil scandal.
Immediately following the publication of the report, the council held a press conference.
COA Deputy Minister Wang Cheng-teng (王政騰) called the testing “not rigorous enough.”
Wang said that the testing was not done in a nationally recognized laboratory, and “Ming Chuan University associate professor of biotechnology Chen Liang-yu’s (陳良宇 testing is qualitative, but to attain accuracy, quantitative testing has to be performed,” Wang said.
He said it is inaccurate to describe metabolites as “drug residues,” calling the report’s implication of the use of banned drugs from the presence of certain metabolites into question.
Chang Su-san (張淑賢), director of the council’s Bureau of Animal and Plant Health Inspection and Quarantine, said that normally the testing of pesticide or veterinary drug residues does not target metabolites, since it is possible that the use of legal pesticides or animal drugs might result in the same kind of metabolite as the use of banned drugs.
For example, she said, the report concludes that dairy farmers used estrogen because of the presence of tetrachloro-o-benzoquinone, a metabolite of estrogen and contraceptive drugs that are prohibited from use in dairy farming.
However, Chang said that tetrachloro-o-benzoquinone is also the metabolite of a chemical compound called pentachlorophenol, which is widely used in herbicides, pesticides and wood preservatives and can produce tetrachloro-o-benzoquinone after decomposition by micro organisms in the soil.
Bureau Deputy Director Huang Kuo-ching (黃國青) added that the report said that the presence of pyrimido Azepine in the milk product suggests the use of illicit antibiotics, but it can result from the use of trimethoprim, an antibiotic permitted at up to 0.05ppm, so the presence of the metabolite alone does not necessarily indicate the use of illicit antibiotics.
Huang also denied that the enzyme-linked immunosorbent assay (ELISA) was the main testing method used by the authority, saying is has been using liquid chromatography-tandem mass spectrometry (LC-MS/MS), a testing method that is even more accurate than the GC-MS used by the study.
Residues of antidepressant might result from tranquilizers, of which certain kinds can be legally used, and plasticizers might have been released from the plastic containers, Huang said.
The Food and Drug Administration yesterday echoed the COA by saying that the presence of certain chemicals does not necessarily indicate violations of the law, as some may not have exceeded the maximum residue level allowed, and added that the agency has been monitoring the use of 81 drugs, of which 48 are approved by the COA and allowed up to a certain level.
There is also a list of 116 drugs that are permitted for treatment if approved by the COA, FDA Deputy Director-General Chiang Yu-mei (姜郁美) said.
Later yesterday, the COA released the latest test results for seven of the said nine products, confirming that they have passed the tests for 48 antibiotics and a kind of painkiller and that plasticizer content was lower than 1ppm.
The agency acknowledged that it has not yet ruled out banned drug use, but reiterated that metabolites cannot be used to determine which drugs have been used or their source.