Dioxin

Dioxins: A Factual Overview

Dioxins are a class of chemicals known as polychlorinated aromatic compounds, characterised by similar structures and chemical and physical properties. They are not intentionally produced but are by-products of various chemical processes. These processes include natural events like volcanic eruptions and forest fires, as well as human activities such as the manufacturing of chemicals, pesticides, steel, and paints, pulp and paper bleaching, exhaust emissions, and incineration. For instance, when chlorinated waste is incinerated without proper controls, dioxins are released into the air.

Dioxins are colorless and odourless organic compounds composed of carbon, hydrogen, oxygen, and chlorine. The term "dioxin" encompasses a broad family of chemicals, with only 17 of the 210 different dioxin compounds being of toxicological concern. The most toxic and extensively studied form is 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), measured in parts per trillion (ppt).

Environmental and Biological Impact

Dioxins are insoluble in water but highly soluble in fat, leading them to bind with sediment and organic matter in the environment and accumulate in animal and human fatty tissues. They are not biodegradable, making them persistent and prone to bioaccumulation in the food chain. Once released into the environment, they accumulate in the fat tissues of animals and humans.

Polychlorinated Biphenyls (PCBs)

PCBs, or polychlorinated biphenyls, are another group of chlorinated aromatic hydrocarbons synthesized by chlorinating biphenyls. Despite being widespread, technical PCB mixtures are still present in transformers, building materials, lubricants, coatings, plasticizers, and inks. Some PCB compounds share toxicological properties with dioxins and are often referred to as "dioxin-like" PCBs.

Dioxin in the Environment

Dioxins are prevalent in the environment, found in air, water, soil, and food across industrialized regions. Human exposure occurs through industrial work, accidents, food, breast milk, and drinking water, with skin contact or inhalation being minor exposure routes.

Entry into the Food Chain

Dioxins enter the food supply through various routes, primarily via aerial transportation and deposition of emissions from sources like waste incineration and chemical production. Soil acts as a natural sink for dioxins, absorbing them through atmospheric deposition, sewage sludge, composts, spills, and erosion. These contaminants are then absorbed by grazing animals and through dust deposits on vegetation.

Food Products Affected

Animal-origin foods contribute approximately 80% of human dioxin exposure. Contamination levels vary based on food origin, with meat, eggs, milk, farmed fish, and other products potentially exceeding background levels due to local environmental contamination or incidents like the 1999 Belgian crisis.

Health Implications

Dioxins are linked to various toxic and biochemical effects, including carcinogenicity. In laboratory animals, they have been associated with endometriosis, developmental and neurobehavioral effects, reproductive issues, and immunotoxic effects. These effects occur at lower exposure levels than carcinogenic effects.

Dioxins in Breast Milk

While mothers' milk contains elevated dioxin levels, the intake by infants is limited to a short period. The SCF and WHO emphasize that current evidence does not warrant changes to breastfeeding recommendations, as breastfeeding offers significant nutritional and immunological benefits.

Detection and Regulation

Dioxin contamination is detected through biological health effects and monitoring programs. Following the 1999 Belgian crisis, the EU imposed trade restrictions on affected products. The European Commission has developed a strategy to reduce dioxin contamination in feed and food, involving scientific assessments and legislative measures.

Legislative Measures

The EU aims to reduce dioxin and PCB contamination in the environment, feed, and foodstuffs to protect public health. Proposed measures include setting maximum levels, action levels for early warnings, and target levels for long-term compliance with scientific recommendations.

Conclusion

Dioxins are not intentionally produced, making prohibition impractical. However, legislation exists to limit PCB production and use, with directives for their disposal. The EU continues to develop strategies to manage dioxin contamination, ensuring public health protection through comprehensive regulatory frameworks.