Dioxins are toxic chemical compounds that can cause reproductive, developmental, immune, and hormonal health problems in humans. According to the US Environmental Protection Agency, the largest sources of dioxin in the 20th century were:
- incinerators (municipal waste incineration),
- metal (ore) smelting,
- refining,
- chemical industry,
- natural sources,
- environmental reservoirs.
The bleaching of chemical cellulose with elemental chlorine also caused environmental damage in the last century, primarily through the release of organic materials into water bodies. Increased public awareness of environmental problems since the 1970s and 1980s influenced the pulp industry and governments to address the release of these materials into the environment. Bleaching with elemental chlorine produced and released large amounts of chlorinated organic compounds, including chlorinated dioxins, into the environment. Dioxins are considered a persistent environmental pollutant regulated internationally by “Stockholm Convention on Persistent Organic Pollutants". As a result, starting in the 1990s, the use of elemental chlorine in the delignification process was significantly reduced and replaced by ECF (Elemental Chlorine Free) and TCF (Total Chlorine Free) with bleaching processes.
Global pulp production by type of bleaching used: chlorine (Cl 2), elemental chlorine-free (ECF) and total chlorine free (TCF).
In 2005, elemental chlorine was still used in old mills for 19-20% of global pulp production, down from 90% in 1990. In 2005, 75% used ECF from pulp production and the remaining 5–6% used TCF. The BAT (Best Available Techniques) rules, which have been in force since the 1990s, do not allow the construction of new plants that use the elemental chlorine bleaching process.
The Swedish pulp industry's switch to ECF bleaching has reduced AOX (Chlorinated Organic Substances) levels to close to zero since 1995:
BAT today does not allow the use of outdated technology and modern ECF bleaching is "dioxin free".
