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.

In April 2012, the Government has made the Pesticide Residues in Food Regulation . (Cap. 132CM, "the Regulation"). The Legislative Council completed scrutiny of the Regulation in June 2012 and the Regulation comes into operation on 1 August 2014. The Regulation specifies in Schedule 1 a list of maximum residue limits (MRLs) and extraneous maximum residue limits (EMRLs) for certain pesticide-food pairs, i.e. the maximum concentration of specified pesticide residues permitted in specific food commodities. Schedule 2 to the Regulation specifies a list of exempted pesticides with no MRLs/EMRLs. These are pesticides that are natural and the residues of which are identical to or indistinguishable from natural food components. The general principle of the Regulation is that except for exempted pesticides, import or sale of food containing pesticide residues with no specified MRLs/EMRLs in Schedule 1 is only allowed if the consumption of the food concerned is not dangerous or prejudicial to health. Based on risk assessment, CFS will decide whether the consumption of the food concerned is dangerous or prejudicial to health.

In 2013 , about 18800 vegetable samples were collected at the import, wholesale and retail levels for testing of pesticide residues. Only 2 samples were found to be unsatisfactory.

Advice to the Public

Members of the public can wash vegetables thoroughly under clean running water. When appropriate, scrub produces with hard surfaces with a clean produce brush to remove dirt and substances including pesticides and contaminants from the surface and the fissures. Use of soaps, special detergents or produce washes is not recommended. Soaking in water and blanching are effective in terms of removing dirt and reducing pesticide residues, but they are no longer considered necessary in the face of nutrient loss in the processes.

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

1. For importers and traders engaged in the import and sale of vegetable supplied from the Mainland, they should import vegetables from farms and processing establishments registered with the Mainland authority, General Administration of Customs of the People's Republic of China.
2. The trade should ensure that the foods they sell or import are fit for human consumption and comply with legal standards.
3. During the use of pesticide for crop protection, the farmers should follow Good Agricultural Practice (GAP) which include but not limited to the following recommendations -
   1. Use only permitted pesticides;
   2. Apply minimum quantities necessary to achieve adequate control;
   3. Leave residues that are the smallest amounts practical and that are toxicologically acceptable;
   4. Strictly adhere to the withholding period or pre-harve s t interval specified on the label of the pesticide to avoid causing harvested crops to contain excessive pesticide residues.
4. For more information regarding the list of permitted pesticides in Hong Kong as well as the safe use of agricultural pesticides, please visit the Agriculture, Fisheries and Conversation Department's Website at http://www.afcd.gov.hk/english/quarantine/qua_pesticide/qua_pesticide.html