Food Safety Focus (4th Issue, November 2006) – Food Safety Platform

Overview of Chemical Hazards

Reported by Miss Joan YAU, Scientific Officer,
Risk Assessment Section, Centre for Food Safety

In the last issue of the newsletter, we have introduced one of the common food hazards - biological hazards. This time, we shall brief you on another one - chemical hazards.

What are Chemical Hazards?

Eating a wide range of chemicals is part of our daily life. Thanks to wider application of agricultural chemicals and food additives, a broader range of safe and wholesome food from different parts of the world is made available to meet consumers' needs. Today, the international food safety authority, Codex Alimentarius Commission, has already established standards for more than 250 food additives as well as more than 250 agricultural chemicals. Together with natural toxicants and industrial chemicals arising from natural sources or human activities, we might be exposed to more than 700 different kinds of chemicals in the food we eat everyday.

These chemicals are present in our food for different reasons, which are:

• Food additives that are intentionally added to achieve certain technological functions during food processing, e.g. preservatives (e.g. benzoic acid) can inhibit microbial growth and colour retention agents (e.g. ascorbic acid) can retain or stabilise the original food pigments.
• Environmental pollutants such as heavy metals (e.g. mercury, lead) and persistent organic pollutants (e.g. dioxins) that enter the food chain as contaminants.
• Chemicals formed during certain food processing or cooking conditions (e.g. acrylamide).
• Residues of agricultural chemicals resulting from previous application of pesticides and veterinary drugs during production and storage of food crops and animals.
• Some naturally produced toxins by microbes or sea animals, e.g. aflatoxins in peanuts, ciguatoxin in coral fish.
• Some naturally present components of food, which may cause adverse reactions under certain conditions, e.g. phytohaemagglutinin in inadequately cooked pulses and beans, allergic substances in peanuts and milk, etc.

The number of chemical hazards is at least hundred times more than that of biological hazards.

Do Chemical Hazards Affect Human Health?

The potential of these chemicals to cause adverse health effects in humans is of particular concern to the general public.

Different from biological hazards, which may cause food poisoning symptoms within a short period of time, long-term toxic effects of food chemicals are usually the prime concern. Harmful chemicals may disrupt body metabolism, cause cancers, damage genes, alter organ functions, affect reproduction and development, etc. Examples are aflatoxins that can increase the risk of liver cancers whereas mercury can affect developing brains in foetuses, infants and children. However, some food chemicals do cause acute effects, e.g. ciguatoxin poisoning.

The presence of chemicals is, however, regulated to protect public health, making reference to safe reference values established by international authorities. Only when dietary exposure exceeds the safe reference value, public health may be at risk. Mere exposure to chemicals should have no cause for undue concern.

Simple Rules to Manage Chemical Risk

For the trade

Food trade should exercise due care in applying and choosing food chemicals; add only the right type and right amount of food chemical which could serve the desired technological function. The trade should also take note of the regulatory requirements in Hong Kong .

For the public

As a general rule, members of the public are advised to take a balanced diet so as to avoid excessive exposure to food chemicals from a small range of food items. You may find specific advice on reducing risks of particular food chemicals on the website of the CFS.