Press Release WHO/45 3 June 1998 WHO EXPERTS RE-EVALUATE HEALTH RISKS FROM DIOXINS Forty specialists from 15 countries met at the headquarters of the World Health Organization (WHO) in Geneva from 25 to 29 May to evaluate the risks which dioxins might cause to health. Since the Seveso incident in 1976, this group of persistent environmental chemicals has consistently grabbed the headlines, although the real effect of these substances is difficult to determine. This group of chemicals includes polychlorinated dibenzodioxins (PCDDs), polychlorinated dibensofurans (PCDFs) and polychlorinated biphenyls (PCBs), although the most toxic dioxin of all is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD has been shown to cause dermatological problems, notably chloracne, a chronic and disfiguring skin disease. These substances are omnipresent in the ground, river beds and air. They are involuntary by-products formed when thermal processes produce chlorine and other organic substances. They can also be produced by volcanic activity, which cannot be controlled, and by forest fires, but the principal controllable sources of dioxin production are waste incinerators. In recent years, the WHO European Centre for Environmental and Health (WHO-ECEH) has been coordinating a comprehensive programme, in collaboration with the International Programme on Chemical Safety (IPCS) on PCDDs, PCDFs and PCBs, to evaluate the possible health risk, as well as methods of prevention and control of environmental exposure of the general population to these chemicals. During a previous meeting on dioxins, held at Bilthoven, in the Netherlands, in 1990, WHO experts established a tolerable daily intake of 10 picogrammes/kilogram body weight for TCDD, said to be the most toxic dioxin. (One picogramme equals a millionth of a millionth of a gram). Since then, new epidemiological data has emerged, notably concerning dioxins' effects on neurological development and the endocrine system, and WHO thus convened the consultation which has just taken place in Geneva to re-evaluate the tolerable daily dose of dioxins to which a human can be exposed. After ample debate, the specialists agreed on a new tolerable daily intake range 1 to 4 picogrammes/kilogram body weight. The experts, however, recognized that subtle effects may already occur in the general population in developed countries at current background levels of 2 to 6 picogrammes/kilogram body weight. They therefore recommended that every effort should be made to reduce exposure to the lowest possible level. The background documents for the experts' meeting discussed carcinogenic and non-carcinogenic effects of dioxins on humans and animals, the risks for young children, transmission mechanisms, general exposure to dioxins and the compounds of the same nature, as well as current means of evaluating these risks in different countries. "Recent exposure data show that measures introduced to control dioxin release in a number of countries have resulted in a substantial reduction in intake of these compounds in the past few years", emphasized Dr Maged Younes, Chief of the Assessment of Risk and Methodology unit in the WHO Programme for the Promotion of Chemical Safety. "This is evidenced by a marked decrease in dioxin levels in human milk, as found in an exposure study conducted by the WHO European Centre for Environment and Health, with the highest rates of decrease being observed in areas which had the highest initial concentrations." For further information, journalists can contact Philippe Stroot, WHO, Geneva. Tel: (41 22) 791 2535, Fax: (41 22) 791 48 58, E-Mail: strootp@who.ch , or Dr Maged Younes, IPCS, Geneva, Tel: (41 22) 791 35 74, Fax: (41 22) 791 48 48, E-mail: younesm@who.ch , or Dr F.X. Rolaf van Leeuwen, ECEH, Bilthoven Division, Tel: (31 30) 22 95 307, Fax: (31 30) 22 94 252, E-mail: rle@who.nl All WHO Press Releases, Fact Sheets and Features as well as other information on this subject can be obtained on Internet on the WHO home page http://www.who.ch/