Learn About Dioxins, Environmental Pollutants


       The Hong Kong authorities announced that hairy crabs were found to contain dioxins exceeding the adopted level. Why are dioxins found in our food? Environmental pollution caused by human industrial activities cannot be ignored. In the “One Health” approach, humans are at the top level of the food chain and the food we eat on a day-to-day basis is interrelated with the Nature. The destruction and pollution of natural environment inevitably threaten food safety to different degrees.


What are dioxins?

       Dioxins are a group of persistent organic pollutants in the environment. They are mainly by-products of industrial processes and are produced during a wide range of manufacturing processes including smelting, chlorine bleaching of paper pulp and manufacture of some herbicides and pesticides. They can also be formed during natural processes, like volcanic eruptions and forest fire.


       Of the various sources of dioxin formation, incomplete burning of waste (solid waste and hospital waste, etc.) is often the worst culprit. When these harmful fumes from waste incineration are released into the atmosphere and entered into rivers, lakes, soils, sediments (e.g. riverbed sediment) and plants (e.g. pasturage), they cause environmental pollution. The harmful substances present in the atmosphere and soils may enter the water system in huge quantity via heavy rainfall and affect water quality and ecology.


Why are dioxins present in our food?

     Dioxins are environmental pollutants found throughout the world. They enter the human food chain mainly through contaminated animal feed and are subsequently accumulated inside the bodies of food animals, primarily in their fatty tissues. Over 90% of human exposure to dioxins is via food supply, mainly from meat, dairy products, fish and shellfish.


How to reduce impacts created by dioxins?

       Due to the omnipresence of dioxins, humans have background exposure to these pollutants and a certain level of dioxins in the body. So far, normal background exposure is unlikely to affect human health. As recommended by the World Health Organization, prevention or reduction of human exposure to dioxins is best done via source-directed measures, i.e., strict control of industrial processes to reduce formation of dioxins.


      Yet, over 90% of human exposure to dioxins is through food intake, mainly from meat, dairy products, fish and shellfish. Protecting the safety and integrity of the food supply chain has thus become crucial. In addition to source-directed measures to reduce dioxin emissions, secondary contamination of food supply has to be avoided throughout the food chain. Since contaminated animal feed is one of the causes of secondary contamination, entities which produce and operate foodstuffs and animal feed have the responsibility to ensure safety of the raw materials and process safety during production.


How can we reduce the risk of exposure to dioxins in daily lives?

      As dioxins are usually accumulated in the fatty tissues of animals, trimming fat from meat and consuming low-fat dairy products can decrease the exposure to dioxin compounds. Maintaining a balanced diet (including adequate amounts of fruits, vegetables and cereals) can help to avoid excessive exposure from a single source.


Source of reference materials:

From “Dioxins and their Effects on Human Health” (www.who.int/mediacentre/factsheets/fs225/zh/), World Health Organization (October, 2016), as of 3 November, 2016