These chemicals are highly toxic environmental pollutants that can accumulate in the food chain and pose a variety of health threats.
Dioxin is the name of specific organic chemical but the term, and its plural form dioxins, are more widely used to describe some of that chemical’s derivatives such as the highly toxic PCDDs (polychlorinated dibenzodioxins).
Dioxins are major environmental pollutants that have been linked to skin diseases, immunological disorders, cancer and birth defects.
Dioxins are not made intentionally but are produced as by-products of a variety of human activities.
Incinerators that burn hospital waste, municipal waste, and hazardous waste are the main source of dioxins, and this helps to explain why these pollutants are now found the world over (see Waste Management).
Other sources are metal smelters, pesticide manufacture and industrial processes that involve chlorine bleaching (such as paper production). Volcanoes and forest fires also produce dioxins but in much smaller quantities than human activities.
Dioxins can dissolve in fats and oils and this allows them to accumulate in the bodies of people and wildlife. For this reason, people are most often exposed to dioxins in the food they eat, especially meat, fish and dairy products.
People are at greater risk if they work with some kinds of chemicals (especially herbicides) or live near major sources of emissions that contain dioxins.
Also at higher risk are developing foetuses and breastfeeding infants who can receive dioxins via their mothers’ blood or milk.
The World Health Organization (WHO) says all people have some dioxins in their tissues, but for most people this will be at very low levels. The WHO has provisionally identified a level of dioxin exposure that it considers to be safe.
A group of dioxin-like chemicals called PCBs are also sometimes referred to as dioxins but they are covered in their own Toolkit page.
Dioxins are persistent organic pollutants (POPs) and, as such, they are subject to the Stockholm Convention, which obliges countries to eliminate where possible, and minimize where not possible, all sources of dioxins.
Dioxin emissions from incinerators can be greatly reduced by ensuring complete combustion and by rapidly cooling the emissions just as they leave the chimney (known as quenching).
Many countries now monitor their food supply for traces of dioxins and can act to reduce any threats if they detect excessive levels.
As most food-related exposures are due to contaminated animal feed the Codex Alimentarius Commission has developed a code of practice to reduce this threat.
In industrialized countries scientists have assessed the sources of dioxins and imposed of dioxins in people’s bodies, but this information is generally lacking in developing nations.
Dioxins are a difficult issue for journalists to report on as it is not easy to prove that any health problems are because of a particular source of pollution.
It is also very difficult to prove that dioxins are even present as the cost of analyzing samples is very high and only a few laboratories in the world can do this work.
Even when it is well known that a large exposure to dioxins has occurred, as in the case of the Seveso chemical disaster, or the Vietnam War (see Warfare), it is still not easy to directly show a link between dioxins and health effects in individual people.
Despite this, such large-scale exposures are themselves are rich sources of strong human stories.
Journalists can also investigate what parties to the Stockholm Convention are doing to minimize or eliminate emissions of dioxins.
The convention has a specific programme to promote the best approaches for reducing this threat, and is a good general source of information and story ideas.
As incinerators are the major emitter of dioxins, journalists can investigate how they are controlling emissions – and whether they are seeking or receiving assistance from government or international agencies to do so.
Journalists can also investigate how dioxin levels in food are regulated and monitored by their national authorities, as this is the main source of exposure.
For this kind of reporting, the World Health Organization’s Food Contamination Monitoring and Assessment Programme is a useful source of contacts and information about each of the 70 countries it operates in.
While incinerators are the main source of dioxins, and chemical disasters and occupational risks are the biggest ways people can get a large exposure to dioxins, food remains the main route of exposure to most people.
In recent years, there have been a number of health scares linked to high levels of dioxins in food.
They include chickens, eggs and catfish in the United States in 1997, milk in Germany in 1998, chickens, eggs and pork in Belgium and other countries in 1999, and meat and dairy products in European countries in 2007.
In every case, the contamination was traced to products that had been fed to farm animals. In some cases the animal feed came from as far as Brazil or India, which demonstrates the ability of dioxins to persist and pose threats far from their source.
These cases also demonstrate the need for systems that monitor food quality and withdraw hazardous products from sale.