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Food Safety Focus (155th Issue, June 2019) – Incident in Focus

Pesticide Residues in Vegetables Available in Local Markets

Reported by Mindy LAM, Agricultural Officer,
Risk  Assessment Section,
Centre for Food Safety

In May 2019, a local organisation released its survey results on pesticide residues in some vegetables available in local markets.  Two vegetable samples (a Chinese amaranth and a Flowering white cabbage) were reported to contain pesticide residues at levels exceeding the Hong Kong regulatory standards.  Vegetables and fruits are essential components of a healthy diet, but would consumers’ health be affected if they consume these foods that are detected with pesticide residues?  This article is going to provide an overview of pesticides in food, health risks of consuming vegetables with pesticides, local regulatory measures and proper ways to wash vegetables.

Figure1. Using pyrimethanil as an example, an Acceptable Daily Intake (ADI) of 0-0.2mg/kg bw/day was established by Joint FAO/WHO Meeting on Pesticide Residues (JMPR). For European lettuce containing pyrimethanil at local legal limit of 3 mg/kg and assuming that European lettuce is the sole dietary source of pyrimethanil , a 60 kg person could consume 4 kg (approximately 6.6 catty) of the European lettuce every day over the entire lifetime without appreciable health risk (i.e. not exceeding the ADI). It is improtant to note, however, that pyrimethanil may also come from other foodstuff.

Pesticide Residues in Food

Pesticides are substances or mixtures of substances that are used for preventing, destroying, repelling or mitigating pests.  Proper use of pesticides in food production can enhance and stabilise crop yield, increase food quality and facilitate food storage.

Even proper use of pesticides will inevitably leave some residues in food. Nevertheless, if pesticides are used according to the Good Agricultural Practice (GAP), the residual levels would be small and consumption of these foods is not likely to affect health.

Health Risks of Consuming Vegetables with Pesticide Residues

Maximum residue limits (MRLs) are usually set by food safety authorities for indicating the maximum concentration of pesticide residues to be legally permitted in or on food when the GAP is observed.  The primary purpose of establishing MRLs is to ensure that only the minimum amount of pesticides is applied to crops for the need of pest control, and thereby minimising the risk to consumers’ health.  Before adopting an MRL, dietary exposure risk assessments are conducted with the established residual levels and food consumption pattern.  This is to ensure that food complying with the regulatory standards are safe for human consumption.  

Although the establishment of MRLs aims to protect consumers' health, these standards should not be directly interpreted as "food safety limits".  In fact, MRLs are set at levels below the amounts that could pose a health risk under normal consumption.  Therefore, intake of food containing pesticide residues that exceed MRLs does not imply that consumer’s health is at risk (e.g. pyrimethanil in European lettuce) (Figure 1), provided that dietary intake of that particular residue is lower than the safety reference values.

Local Regulatory Control of Pesticide Residues in Food

In Hong Kong, pesticide residues in vegetables and fruits are regulated under the Pesticide Residues in Food Regulation (Cap. 132CM).  In the past three years, 111 vegetable and fruit samples out of 72,583 food samples collected by the Centre for Food Safety (CFS) for testing of pesticide residues were found to be exceeding the local legal limits. The overall unsatisfactory rate was about 0.2%.

Previous CFS’s Total Diet Study on pesticides also showed that dietary exposures to the residues of 85 commonly encountered pesticides and some organochlorine pesticides would unlikely pose unacceptable health risks to consumers.

Proper Ways to Wash Vegetables

Consumers are advised to rinse vegetables thoroughly under clean running water to remove pesticides, dirt and germs from the surface of the vegetables, a measure also recommended by the World Health Organization.  Some national authorities have specifically not recommended the use of detergents or hand wash for home use lest it introduces a new source of chemical residues.  Peeling and scrubbing of hard produce (e.g. pumpkins) are also recommended to minimise pesticide residues and dirt.

Follow-up Action

In response to the above survey result, the CFS had collected follow-up samples of Chinese amaranth and Flowering white cabbage from the markets for testing of pesticide residues. All results were satisfactory.

Key Points to Note:

  1. The proper use of pesticides in food production can improve both the quantity and quality of crops.
  2. Intake of food with pesticide residues exceeding MRLs does not necessarily imply consumers' health is at risk under normal consumption.

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