A chronology of events

Prehistory 1976 1977 1978-1982 1983-1986 1993-1995 People

1976

Friday, 9 July	14.30 hours Seveso/Icmesa. Dr Paolo Paoletti, director of production at Icmesa, discusses the production programme with the various foremen, including the one responsible for Building B. As usual in Building B, trichlorophenol (TCP) was to be produced. Trichlorophenol is an intermediate used in the production of the disinfectant hexachlorophene. 16.00 hours The TCP reaction vessel is filled with the various starting materials.
Saturday, 10 July	02.30 hours Icmesa. According to the temperature diagram the reaction is completed. 04.45 hours The foreman in charge gives the order to interrupt a distillation which is not completed. The heating is turned off and the vessel contents mixed for a further 15 minutes. The last measured temperature is 158°C. 06.00 hours The night shift is over. The workers leave the factory, and only the cleaning and maintenance crew remains behind. 12.37 hours The rupture disk in the safety valve bursts as a result of excessive pressure, caused by an exothermic reaction in the TCP vessel. An Icmesa technician later told the investigating commision that the reactor temperature at the time of the accident was between 450°C and 500°C and the conditions for the formation of a significant amount of dioxine had developed. The reasons for the sudden increase in temperature and pressure are, according to Givaudan and Icmesa official statementes, unknown and unexplainable. A chemical mixture in the form of an aerosol cloud escapes into the air in a south-easterly direction. Heavy rain fell and brouht the toxic material down to the ground. Some children reported seeing the cloud, but then it disappeared. It is later learned that the mixture falls mainly on the communes of Seveso, Meda, Cesano Maderno and Desio. 13.00 hours A foreman present at the plant telephones Dr Clemente Barni, the deputy head of production, who is on standby call that day. 13.10 hours Dr Barni arrives at the Icmesa plant. 13.45 hours A foreman turns on the cooling system, thereby stopping the escape of the mixture. 14.30 hours Dr Barni inspects the area immediately surrounding the factory but notices nothing out of the ordinary. 17.45–18.30 hours Dr Barni inspects the immediate surroundings of the factory and warns the inhabitants not to eat any local vegetables or fruit. 19.00 hours The factory porter is instructed by Dr Barni to reach the ufficiale sanitario, the local health officer for Seveso and Meda, Professor Giuseppe Ghetti. He is absent, and it is not possible to find out who his deputy is. 20.30 hours Dr Barni telephones the carabinieri of Meda and reports the incident. He inquires whether damage has been reported and requests that any such reports should be transmitted to Icmesa.
Sunday, 11 July	08.00–10.30 hours Icmesa. Dr Paoletti and Dr Barni inspect the surroundings for signs of damage to plants. 10.30-11.25 hours The Icmesa management tries unsuccessfully to reach the ufficiale sanitario or his deputy. 14.05 hours Dr Paoletti reaches Herwig von Zwehl, the Technical Director of Icmesa, who had gone away for the weekend. They decide on the following procedure: they would first see the ufficiale sanitario or his deputy; then visit the mayor of Meda, Fabrizio Malgratti and the mayor of Seveso, Francesco Rocca; they would again contact the carabinieri and then collect samples for analysis from the vessel and in the surrounding area. 14.15 hours Von Zwehl telephones Dr Jörg Sambeth, the Technical Director of Givaudan in Geneva, the parent company of Icmesa. They decide to send the samples the same evening by courier for examination in Switzerland. 15.00 hours Dr Paoletti again unsuccessfully tries to reach the ufficiale sanitario. 16.10 hours Dr Paoletti and Dr Barni visit the mayor of Seveso and request that the inhabitants of the presumably affected areas be warned not to eat or even touch fruit and vegetables. They also request an interview with the mayor of Meda. 17.00 hours At the carabinieri station in Meda, two representatives of Icmesa meet with the mayor of Meda, the chief surveyor of the commune, the officer in charge of the Meda police station and a municipal policeman (vigile urbano). The Icmesa representatives request that the population be warned not to eat or even touch fruit and vegetables. They also state that in all likelihood the aerosol mixture which escaped consists of sodium trichlorphenate, caustic soda and solvent, but possibly other toxic substances as well. 18.00 hours Dr Barni, together with a carabiniere and a vigile urbano, go around the area of Meda and warn the inhabitants. It is not possible to do the same in Seveso as the mayor cannot find any vigile.
Monday, 12 July	05.30 hours Icmesa. Dr Barni closes off Building B. Yet, the factory was open and normal work resumed. Icmesa sent a letter to the local health authorities that confirmed that an accident had occurred at the factory, but, again, they mentioned only herbicides. 'Not being able to evaluate the nature of the substances carried by those vapors and their exact effects, we have intervened with neighbors asking them not to consume garden products, knowing that the final product is also used in herbicides.' 10.30 hours Dr Uberti, the deputy of the ufficiale sanitario of Seveso, inspects the factory premises. Givaudan Dübendorf. Arrival of the first samples. The laboratories work round the clock and produce the first results on 14–15 July.
Tuesday, 13 July	Icmesa. Dr Paoletti and Alfio Marcolini, the commercial head of Icmesa, learn that some small animals have died. Health authorities sent a letter to the Mayors of Meda and Seveso assuring them that there was no danger to people living in the surrounding areas.
Wednesday, 14 July	Icmesa. The first signs of skin inflammation occur in children. 23.00 hours Dr Sambeth informs von Zwehl that the samples contain traces of dioxin (TCDD). The precise quantity of dioxin that escaped could not be determined after the accident. Estimates by experts vary from a few hundred grams to a few kilograms at most. Near the factory, the deaths of a large number of animals were reported.
Thursday, 15 July	09.00 hours Icmesa. Marcolini tries unsuccessfully to arrange a meeting with the mayors of Meda and Seveso. 11.15 hours The factory doctor, Dr Ernesto Bergamaschini, examines the affected inhabitants and all Icmesa factory workers, first of all those who were involved in the TCP production process. He finds no signs of toxicity in the factory workers. In the neighbourhood families, however, he finds some cases of acute skin inflammation, particularly in two children. All those affected are hospitalized. 18.15 hours A meeting is held at the communal offices of Seveso. The Icmesa representatives again ask the population not to eat or touch fruit or vegetables. Von Zwehl points out that the substance which escaped is highly toxic. The need for evacuation of the area is discussed. The mayor of Seveso issues decree No. 43, declaring the area of San Pietro, to the south of the Icmesa premises, contaminated. Warning signs are to be put up and the danger zone fenced off. The mayor of Meda issues decree No. 2 in which the area of San Pietro is declared to be contaminated. This zone includes area of the communes of Seveso and Meda. He also prohibits consumption of fruit or vegetables from this zone. Switzerland. Dr Sambeth and Dr Bruno Vaterlaus, head of research at Givaudan in Dübendorf travel to Roche Basel to discuss the situation with the Technical Director, Reto Schett. Dr Giuseppe Reggiani, director of Clinical Research at Roche Basel, is instructed by the management of Roche to investigate the possible effects of the accident on the health of the Icmesa employees and the local population and to take all necessary measures to prevent or treat any damage to health.
Friday, 16 July	18.15 hours The mayor of Seveso and his deputy, Dr Uberti, as well as eight further members of the communal executive meet. Dr Uberti reports that between 12 and 16 children have been hospitalized, but nobody knew what treatment to give. The resident called for a strike and insisted that the authorities give them an accurate information. The evacuation recommended by Icmesa is postponed. Professor Ghetti, the ufficiale sanitario, is called back from his holidays for consultation on this question. 19.00 hours Dr Barni and Dr Bergamaschini visit the families in the neighbourhood and recommend that they voluntarily evacuate their houses. The occupants of two houses are evacuated.
Saturday, 17 July	Icmesa. The management orders the factory to be closed as a precautionary measure. Dr Reggiani arrives and arranges for four of the twelve hospitalized children to be transferred from the local hospital to the Niguarda Hospital in Milan, which has special equipment. On Sunday, 18 July he gives the doctors in Milan and Desio all available documentation on the toxicology of TCDD. The mayors of Seveso and Meda added extra instruction for the residents around the factory, now ordering the burning ofnpolluting garden and burning and killing of affected animals. 19.30 hours Icmesa. Discussion with representatives of the Italian health authorities (including Professor Ghetti and Dr Aldo Cavallaro, head of the provincial Laboratory for Hygiene and Prophylaxis). Von Zwehl announces that in the accident TCDD was released. The ufficiale sanitario questions the extent of the danger presented by this substance.
Sunday, 18 July	10.00 hours Seveso. The mayor of Seveso has called a further meeting in which the Icmesa representatives, Dr Cavallaro, Professor Ghetti, the district judge Salvatore Adamo and representatives of the works council participate. Professor Ghetti and Dr Cavallaro decide to travel to Givaudan in Dübendorf to have the results of the analysis directly confirmed by the chemists and to familiarize themselves with the methods of detecting TCDD. 16.00 hours The factory is officially closed and the entrance to Building B sealed.
Monday, 19 July	Milan. Professor Ghetti and Dr Cavallaro receive documentation on the methods used for detecting TCDD. Five more children were hospitalized.
Tuesday, 20 July	Dübendorf. The Givaudan chemists confirm for Professor Ghetti and Dr Cavallaro that TCDD was found in the samples. They receive a map showing the places where dioxin was found. Animals died within a 3-Km radius outside the area originally considered endangered.
Wednesday, 21 July	Icmesa. During a meeting on the premises of Icmesa with Rocca and the works council members, von Zwehl is arrested. In the courthouse of Desio he meets Dr Paoletti who has also been arrested for causing an accident. They are questioned by the district judge Adamo. Milan. Professor Ghetti and Dr Cavallaro inform the prefect of Milan and the provincial health officer that the initial analyses have revealed relatively high amounts of TCDD. The prefect calls a meeting of the health board of the Region of Lombardy, to which experts from the ministry of Health in Rome and the Istituto Superiore di Sanità are invited. Part of the area of the communes of Cesano Maderno and Desio are also found to be contaminated. Measures similar to those for Meda and Seveso are taken. Basel. Dr Reggiani contacts experts from the firms Coalite (Great Britain), BASF (West Germany), Philips-Duphar (Holland), Chemie Linz (Austria) and Dow Chemicals (USA), which have all had dioxin accidents. All the experts recommend evacuation of the population. Although the extent of the contaminated area is not yet known, Dr Reggiani decides to recommend to the Italian authorities that the inhabitants should be evacuated and travels to Milan for this purpose.
Friday, 23 July	Milan. The specialists invited the previous day by the prefect of Milan to a meeting are of the opinion that no further protective measures are necessary. The university representatives as the meeting unanimously agreed that further measures were not necessaty or urgent. Vittoria Rivolta, the Minister of Health of the Region, declares on television that the measures taken are sufficient. Dr Reggiani, who has already spoken with the mayor of Seveso in order to have the population evacuated, tries the same morning to speak at the meeting at the prefect's office in Milan to recommend this urgent measure. He is turned down because he cannot prove that he is an official emissary of Givaudan and Roche. Seveso. Towards the evening, Dr Reggiani succeeds in speaking to Rivolta in the communal offices of Seveso. He tries to persuade him of the necessity of evacuating the population. Rivolta then declares his willingness to call another meeting the next day. Basel. At the same time, the director of Hoffman-LaRoche's medical center in Basel declared that the situation was very serious, that draconian measures were necessary, and that 20 cm of the ground surface had to be removed, the factory buried, and the houses destroyed.
Saturday, 24 July	Milan/Evacuation. In place of Dr Reggiani, who has returned to Switzerland on learning that he is being sought by the Italian police, Dr Vaterlaus appears with an authorization from Givaudan. He gives the authorities a map with details of the contaminated area southeast of the Icmesa premises. In the accompanying letter Dr Guy Waldvogel, Director of Givaudan SA and member of the Board of Directors of Icmesa, strongly urges that the contaminated area should be evacuated. The same evening Dr Cavallaro confirms that the responsible Italian laboratory has found traces of dioxin in soil samples. Evacuation has become unavoidable. Medical monitoring. Givaudan recommends to the Italian authorities that the medical supervision of patients should be continued even after symptoms have regressed and should be extended to all persons living in the contaminated areas. The regional health director castigated the Hoffman-LaRoche medical director: This person was dumped on us; nobody expected him, and nobody expected such severe statements. To my knowledge, he is not an official representative of the company and I shall today request to know on whose behalf he speaks. I have made clear to him the seriousness of what he says. I have the impression that this person is bluffing. And this person will have to answer for his statment. Later in the afternoon the official position changed, and decision was made to evacuate 179 people who lived in an area of two square miles. They were told not to eat any produce or meat from the area (which, except for the immediater neighbors of the factory, they had eaten for the previous two weeks). The contaminated area was not closed completely, however; a road passing through it continued to be used.
Sunday, 25 July	Seveso. The evacuation is prepared and the population informed. The area to be evacuated is fenced off. Dr Cavallaro travels to Zurich with Professor Franco Pocchiari, head of the Istituto Superiore di Sanità and other representatives of the health authorities to discuss matters with European dioxin experts and representatives from Givaudan.
Monday, 26 July	Evacuation. To start with, 208 people from 37 houses leave the contaminated area. Amaizingly, the evacuated residents are allowed to take only those personal effects which were in 'closed containers' at the time of the accident, which are potentially contaminated objects. Before they arrive at their provisional quarters in the Hotel Leonardo da Vinci in Bruzzano, they are examined by a doctor. On the basis of new analyses, Zone A is extended. Animal deaths slaughter. Approximately 3 300 animals perish, mostly poultry and rabbits. Emergency slaughtering is decreed to prevent TCDD from entering the food chain. By 1978 some 77 000 animals will have been slaughtered.
Wednesday, 28 July	The health authorities of the Region of Lombardy create four committees to deal with the following problems: medical monitoring of the population, analysis, decontamination of the site and veterinary medicine. A further 19 persons are evacuated. A total of 40 houses have had to be abandoned.
Friday, 30 July	Zone plan. The contaminated area is divided into three zones. Zone A has the highest degree of contamination (more than 50 micrograms per square metre). The contamination is less severe in Zone B (5-50 micrograms per square metre), while in Zone R no TCDD or only slight traces (less than 5 micrograms per square metre) are found. Zone A is further divided into 7 subzones according to the severity of contamination. The number of people affected in Zone A is 736 (they are all evacuated), in Zone B, about 4 700 and in Zone R, about 31 800. (see map)
July – August	Health. 1600 people of all age groups are examined at the outpatient clinic in Seveso. 447 of them are suffering from acute skin lesions, presumably caused by the escape of chemicals. The patients recover within two to three weeks. There is fear of outside contamination from people who come from evacuated area: some hotels refuse to provide them with accomodation and, ironically, Switzerland closes its border to Italian food products and take air samples along the border in order to detect any contamination that may reach Swiss territory. Some businesses refuses to take shipments of forniture coming from the Seveso area.The first cases of chloracne are recorded at the end of August.
Monday, 2 August	Evacuation/monitoring of health. New analyses make it imperative to evacuate a further 500 people from 90 houses in Zone A. After a medical examination, they are housed in the AGIP motel in Assago near Milan. A total of 736 persons have now been evacuated. The health authorities decide that children and pregnant women should leave Zone B during the day to minimize the danger of contact with TCDD. Abortion. The regional health authorities permit pregnant women in the contaminated zones to decide freely whether they wish to continue their pregnancy to the full term.
Tuesday, 3 August	Advice centre for pregnant women. In Seveso an advice centre for pregnant women is set up. At this point, the doctors are unable to tell the women with any certainty whether TCDD is teratogenic or not.
August	Abortion. In view of the risk of giving birth to a deformed child, some women decide to have an abortion.
Wednesday, 4 August	Cimmino Commission. The Italian government sets up a technical-scientific commission reporting to the Ministry of Health. Its task is to work out and propose decontamination measures for the affected area. This commission will later be known as the Cimmino Commission, after its chairman, Professor Aldo Cimmino.
Thursday, 5 August	Lombardy. The government of the Region of Lombardy issues Decree No, 25 on ‘Regional measures to aid the affected population’. A committee is created, under the chairmanship of the Regional Health Minister, to coordinate all activities in the Seveso area.
Tuesday, 10 August	Rome. The Italian government grants a loan of 40 billion lire to the Region of Lombardy to finance reclamation of the contaminated area as well as medical and welfare payments.
Wednesday, 11 August	Basel. Dr Adolf W. Jann, Chairman of the Board of Directors of Roche, and Dr Waldvogel give a press conference. The Roche group commits itself to covering the costs of the damage.
Friday, 13 August	Milan. The government of the Region of Lombardy sets up the Giovanardi Commission (named after its chairman, Augusto Giovanardi, the former Director of the Milan Institute of Hygiene). This Commission is to implement the proposals of the Cimmino Commission.
Tuesday, 24 August	Decontamination proposal. Givaudan submits an initial decontamination plan worked out by the British engineering firm Cremer & Warner.
September	Milan. After closing the factory, Icmesa opens an office in the centre of Milan to ensure efficient contact with the regional authorities. Seveso, Zone A. In spite of the guards, people are continually entering the off-limit Zone A. The area is thus sealed off with more stable, higher fences. Lombardy. The Region grants Givaudan authoritzation to decontaminate houses in Zones A6 and A7.
Autumn	The Region of Lombardy studies the possibility of constructing a high-temperature incinerator in the heavily contaminated zone in order to destroy the contaminated earth and buildings. The project meets with the opposition of the local population.
Tuesday, 23 November	An agreement reached between the Region of Lombardy and Givaudan governs the use, removal and disposal of chemicals and raw materials from the factory.

Appendix 1 | Appendix 2 |

Giorgio Maria Di Nunzio
nunziog@dcs.gla.ac.uk
Open Assessment - Safety Critical System 1999-2000