How does the Centre for Food Safety Monitor and Control Vegetables on Sale in Hong Kong?

Proper use of pesticide on vegetables can improve crop quality and reduce harmful effects of the pests. Consumers’ health and living quality are thereby enhanced. However, if pesticide is used improperly, consumers may ingest excessive amount of pesticide which affects their health and may lead to acute food poisoning with symptoms such as vomiting, diarrhoea, abdominal pain, dizziness and numbness. In severe cases, the victim may even have difficulties in breathing, blurred vision and convulsion. Prolonged consumption of vegetables with excessive pesticides may also damage the nervous system or other organs such as the liver and kidneys. Some pesticides may be transferred via the placenta or breast feeding, thereby affecting development of the baby.

The use of pesticide will inevitably leave some residues on the crops. However, if pesticide is used properly, the residual level would be small and consumption of these vegetables will not affect health. Excessive pesticide residue can arise from several causes, including excessive use of pesticide, insufficient time for pesticide to decompose before harvesting as well as environmental contamination. Pesticide residual problems are more commonly seen in leafy vegetables such as Chinese flowering cabbage, Chinese white cabbage, spinach, water spinach, garland chrysanthemum, matrimony vine and Chinese kale.

The Centre for Food Safety (CFS) of Food and Environmental Hygiene Department (FEHD) operates a Food Surveillance Programme and regularly takes samples of vegetables at import, wholesale and retail levels for testing. Most of the vegetables on sale in Hong Kong come from the Mainland. CFS has a Food Control Office at Man Kam To and samples vegetables imported from the Mainland. All vegetables imported from the Mainland must come from registered farms or purchasing stations under the supervision of the Mainland monitoring authorities. When the vegetables reach Man Kam To, CFS would inspect relevant documents including Pesticide Declaration Certificate, Monitoring Card etc. Random samples of vegetable will also be collected for testing of pesticide residues at the Man Kam To Food Laboratory whenever necessary. In addition, CFS would also collect vegetable samples at the wholesale and retail levels for testing of pesticide residues in Government Laboratory. Furthermore, vegetable samples will also be collected and tested for heavy metals. So far, the existing surveillance and control system on vegetables in Hong Kong is effective in safeguarding public health.

CFS currently take reference from the Maximum Residue Limits (MRLs) recommended by Codex Alimentarius Commission in determining whether vegetables contain excessive pesticide residues. MRL is the maximum concentration of a pesticide residue permitted in a food commodity when Good Agricultural Practice is observed. The primary aim of setting MRLs for pesticides in food is to safeguard public health and provides an indicator for the trade. Foods containing pesticides below MRLs are considered wholesome and fit for human consumption. However, pesticide residue levels exceeding the MRL does not necessarily mean that there is an immediate health risk. There is no cause for undue alarm for the public. Instead, pesticide residual levels exceeding the MRL reflect improper use of pesticide or contamination of the vegetable and rectification at source is required.

In 2005, some 20 000 vegetable samples were collected at the import, wholesale and retail levels for testing of pesticide residues. Only 10 samples were found to be unsatisfactory.

Recent findings of an environmental concern group alleged that prohibited pesticides or excessive pesticide residues were found in some of the vegetables sold in two local chains of supermarket. CFS immediately took a series of follow-up action, including contacting the party concerned for more information, liaising with the two supermarket chains involved on the source of vegetables and their suppliers, informing the Mainland authorities of the findings and collecting vegetable samples from local supermarkets for testing of pesticide residues. A total of 39 samples of vegetables and beans were collected from a number of supermarkets earlier on for testing of pesticide residues and all were found to be satisfactory.

Advice to the Public

To reduce the health risk due to consumption of vegetables with excessive pesticide residues, members of the public can wash the vegetables well in clean running water for several times, then soak vegetables in water for one hour. Alternatively, they may blanch the vegetables in boiling water for one minute and discard the water used for blanching. The above measures can be adopted together for further risk reduction. For concerned individuals who wish to further reduce their intake of pesticides, they may also remove the outer leaves and peel the vegetables.

Vegetables are an essential component of a healthy diet. Members of the public should take a balanced diet and eat a variety of fruits and vegetables to avoid excessive exposure to contaminants from a small range of food items. If consumption of "poisonous" vegetables is suspected, one should seek medical advice immediately from hospitals or clinics.

Advice to the Trade

To prevent the occurrence of pesticide poisoning, the trade should observe Good Agricultural Practice, including the followings:

＊ Use only permitted pesticides;
＊ Apply minimum quantities required to achieve effective control;
＊ In general, the crops should not be harvested within 2 weeks after the last treatment.