Chemical Safety and Health
Through the Chemical Safety and Health Unit, WHO works to establish the scientific basis for the sound management of chemicals, and to strengthen national capabilities and capacities for chemical safety.
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Dioxins and dioxin-like substances

Dioxins and dioxin-like substances, including PCBs, are persistent organic pollutants (POPs) covered by the Stockholm Convention. They can travel long distances from the source of emission, and bioaccumulate in food chains.

Human exposure to dioxins and dioxin-like substances has been associated with a range of toxic effects, including chloracne; reproductive, developmental and neurodevelopmental effects; immunotoxicity; and effects on thyroid hormones, liver and tooth development. They are also carcinogenic. Developmental effects in males are the most sensitive toxic end-point, making children – particularly breastfed infants – the population most at risk.

These substances are unwanted byproducts of combustion and various industrial processes, such as chlorine bleaching of paper pulp and smelting. While manufacture of PCBs is now prohibited and their use in equipment is to be phased out by 2025, release into the environment still occurs from disposal of large-scale electrical equipment and waste. General population exposure to dioxins and dioxin-like substances occurs mainly through consumption of contaminated food, but higher levels of exposure can occur in occupational settings.

Actions to reduce emissions of these substances are required by the Stockholm Convention. Interventions to reduce human exposure include:

  • identifying and safely disposing of material containing or likely to generate dioxins and dioxin-like substances, such as electrical equipment;
  • ensuring appropriate combustion practices to reduce emissions;
  • implementing FAO/WHO strategies to reduce contamination in food and feed; and
  • monitoring of food items, human milk and air, as well as exposures in workers likely to be exposed to higher levels.