About 37 percent of samples of organic vegetables have tested positive for pesticide residues, the Consumer Council said.
Over 100 samples of vegetables, including 75 organic samples which are selling for higher prices than their traditionally grown counterparts, were tested for residues of over 300 types of pesticides and seven types of heavy metals, Apple Daily reports.
Of the 52 non-organic samples, 60 percent were found to have residues of pesticides and 12 percent contained heavy metals.
About 86 percent of the choi sum samples and 73 percent of the tomatoes were found to have residual pesticides, the highest proportion among the samples tested.
Cabbages and carrots had the least number of samples with pesticide residues.
The test shows that organic vegetables are not necessarily free of pesticides.
This is best illustrated by a sample of sweet potato from a farm in Shandong province that has obtained an organic certification from the European Union (EU).
Laboratory tests showed the sample contained 0.07 mg of chlorpyrifos per kilogram, exceeding the legal limit of 0.05 mg/kg.
A sample of organic carrot from the United States was also found to have 0.09 mg of cadmium per kilogram, which is just a fraction shy of the legal limit 0.1 mg/kg.
A sample of string beans from mainland China was found to have 0.03 mg of chlorpyrifos per kilogram, which was three times the legal limit of 0.01 mg/kg, along with the presence of five other pesticides (including prochloraz at 4.74 mg/kg).
The daily intake limit would be exceeded if an adult weighing 60kg would eat 80 grams of the sample beans each time for two meals in a day, the Consumer Council said.
Intake of chlorpyrifos within a short period of time could lead to acute intoxication, diarrhea, abnormal heart beating, and difficulty in breathing.
According to Consumer Council vice chairman Philip Leung Kwong-hon, US food and drug regulators require that the level of residual pesticides in vegetables be at least 5 percent lower than the legal limits in order to be called organic.
Pesticide residues must also come from the environment and not from chemicals applied on plants and crops, he added.
Leung said Hong Kong does not have legal definitions to organic produce, and as such, no laws are violated if a vegetable sample is found to have excessive pesticides.
Lau Lai-kwan, from the Sustainable Ecological Ethical Development Foundation, said only organic pesticides made from plant extracts should be used in organic farming.
Any chemical pesticides, such as chlorpyrifos, should never be used in organic farming, and therefore should not be found in organic vegetables.
Secretary for Food and Health Ko Wing-man said authorities have been monitoring vegetables for residual pesticides in the past two years and vowed to step up spot checks.
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