Seveso II Directive

Seveso disaster

The Seveso disaster was an industrial accident that occurred around 12:37 pm July 10, 1976, in a small chemical manufacturing plant approximately 25 km north of Milan in the Lombardy region in Italy. It resulted in the highest known exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in residential populations which gave rise to numerous scientific studies and standardized industrial safety regulations. The EU industrial safety regulations are known as the Seveso II Directive.

The accident


The Seveso disaster was so named because Seveso was the community most affected. Seveso is a small town with the population of 17,000 in 1976, other affected neighbourhood communities were Meda (19,000), Desio (33,000), Cesano Maderno (34,000) and to a lesser extent Barlassina (6,000) and Bovisio-Masciago (11,000). The industrial plant was close by Meda, owned by the company ICMESA (Industrie Chimiche Meda Società), a subsidiary of Givaudan which in turn was a subsidiary of Hoffmann-La Roche (Roche Group). The factory building was built many years ago and the local population did not perceive it as a potential source of danger. Moreover although several industrial accidents involving dioxins had occurred before they were of a more limited scale with the exception of the use of Agent Orange as a herbicidal warfare agent during the Vietnam War.

Chemical events

The accident occurred in building B where 2,4,5 T (2,4,5 trichlorophenoxyacetic acid), a herbicide, was being produced from 1,2,4,5-tetrachlorobenzene by the nucleophilic aromatic substitution reaction with sodium hydroxide. It is thought that some 1,2,4,5-tetrachlorobenzene had formed a solid cake on the upper parts of the reaction vessel. As the temperature increased this melted and entered the sodium hydroxide containing mixture. The addition of more 1,2,4,5-tetrachlorobenzene increased the rate of heat production. It is likely that the dioxin formed by either an Ullmann condensation ether synthesis (this requires a metal catalyst) or by a simple pair of nucleophilic attacks on the aromatic ring. The 2,4,5-trichlorophenol was intended for use as an intermediate in the production of hexachlorophene, a medical disinfectant. An unintended byproduct of the manufacture of TCP is TCDD in trace amounts, measured in ppm (parts per million). Due to human error, around mid-noon on a Saturday, an uncontrolled reaction (thermal runaway) occurred bursting the security disk of the chemical reactor and an aerosol cloud containing sodium hydroxide, ethylene glycol, sodium trichlorophenate, and somewhere between a few hundred grams and up to a few kilograms of TCDD was released over an 18 km² area.

Immediate effects

The affected area was split into zones A, B and R in decreasing order of surface soil concentrations of TCDD. Zone A was further split into 7 sub-zones. The local population was advised not to touch or eat locally grown fruits or vegetables.

  • Zone A had a TCDD soil concentration of > 50 micrograms per square metre (µg/m²), it had 736 residents.
  • Zone B had a TCDD soil concentration of between 5 and 50 µg/m², it had about 4700 residents.
  • Zone R had negligible or a TCDD soil concentration of < 5 µg/m², it had 31,800 residents.

Within days a total of 3300 animals were found dead, mostly poultry and rabbits. Emergency slaughtering commensed to prevent TCDD from entering the food chain, by 1978 over 80,000 animals had been slaughtered. 15 children were quickly hospitalised with skin inflammation. By the end of August Zone A had been completely evacuated and fenced, 1600 people of all ages had been examined and 447 were found to suffer from skin lesions or chloracne. An advice center was set up for pregnant women of which several opted for an abortion, which was legal in special cases, after consultation. Herwig von Zwehl - the Technical Director of ICMESA, and Paolo Paoletti - director of production at ICMESA, were arrested. Then two government commissions were established to thrash out a plan for quarantining and decontaminating the area and finally the Italian government diverted 40 billion liras from its coffers, this amount would be tripled two years later.

Cleanup operations

In January 1977, an action plan consisting of scientific analysis, economic aid, medical monitoring and restoration/decontamination was completed. Shortly after Icmesa began to pay the first compensations to those affected. Later that spring decontamination operations were initiated and in June a system epidemiological health monitoring for 220,000 people was launched. In September The International Steering Committee was created, staffed with "renowned experts from all over the world", in order to assess the scientific data generated. In February, 1984 The International Steering Committee released its final report stating that "with the exception of chloracne, no ill effects can be attributed to TCDD".

In June 1978, the Italian government raised its special loan from 40 to 115 billion liras. By the end of the year most individual compensation claims had been settled [out of court]. On February 2, 1980 Paolo Paoletti - the Director of Production at Icmesa - was shot and killed in Monza by a member of the Italian radical left-wing terrorist organization Prima Linea. On December 19, 1980 representatives of the Region of Lombardy/Italian Republic and Givaudan/Icmesa signed a compensation agreement in the presence of the prime minister of Italy, Arnaldo Forlani. The total amount would reach 20 billion liras (€ 10.3 million).

Waste from the cleanup

The waste from the clean up of the plant was a mixture of protective clothing and chemical residues from the plant. This waste was packed into waste drums which had been designed for the storage of nuclear waste. It was agreed that the waste would be disposed of in a legal manner.

To this end, in spring 1982, the firm Mannesmann Italiana was contracted to dispose of the contaminated chemicals from Zone A. Mannesmann Italiana made it a condition that Givaudan would not be notified of the disposal site which prompted Givaudan to insist that a notary public certify the disposal. On September 9 41 barrels of toxic waste left the Icmesa premises. On December 13, the notary gave a sworn statement that the barrels had been disposed of in an approved way.

However, in February 1983, the programme "A bon entendeur" on Télévision Suisse Romande, a French language Swiss TV channel, followed the route of the barrels to Saint-Quentin in northern France where they disappeared. A public debate ensued in which numerous theories were put forward when it was found out that Mannesmann Italiana hired two subcontractors to get rid of the toxic waste. On May 19 the 41 barrels were found in an unused abattoir in Anguilcourt-le-Sart, a village in northern France. From there they were transferred to a French military base near Sissonne. The Roche Group (parent firm of Givaudan) took it upon itself to properly dispose of the waste. On November 25, over nine years after the disaster, the Roche Group issued a public statement that the toxic waste consisting of 42 barrels (1 was added earlier that year) had all been incinerated in Switzerland. According to New Scientist it was thought that the high chlorine content of the waste might cause damage to the high temperature incinerator used by Roche, but Roche stated that they would burn the waste in the incinerator and repair it afterwards if it were damaged. They stated that they wanted to take responsibility for the safe destruction of the waste.

Criminal court case

In September, the Criminal Court of Monza sentenced five former employees of Icmesa or its parent company Givaudan, respectively, to prison sentences ranging from 2.5 years to 5 years. They all appealed.

In May 1985, the Court of Appeal in Milan finds three of the five accused not guilty, the two still facing prosecution appealed to the Supreme Court in Rome.

On May 23, 1986, the Supreme Court in Rome confirmed the judgment against the two remaining even though the prosecuting attorney had called for their acquittal.


The safety operations handled by the company's directors and local government were badly coordinated and to some extent incompetent. At least a week passed before it was publicly stated that dioxin had been emitted and another week passed before evacuation began. Few scientific studies had confirmed the level of danger TCDD posed and there were scant industrial regulations to be followed. As a result the local population was caught unaware when the accident happened and in such an insecure situation became very frightened. Confrontation with an invisible poison possibly extremely hazardous to human health was a very traumatic experience for small rural communities.

"In the context of such heightened tensions, Seveso became a microcosm where all the existing conflicts within society (political, institutional, religious, industrial) were reflected. However, within a relatively short time such conflicts abated and the recovery of the community proceeded. In Seveso accident the responsible party was known from the outset and soon offered reparation. Moreover, the eventual disappearance of the offending factory itself and the physical exportation of the toxic substances and polluted soil enabled the community to feel cleansed. The resolution of the emotional after-effects of the trauma, so necessary for the recovery of a community, was facilitated by these favourable circumstances."

Industrial safety regulations were passed in the European Community in 1982 called the Seveso Directive which imposed much harsher industrial regulations. The Seveso Directive was updated in 1999, amended again in 2005 and is currently referred to as the Seveso II Directive (or COMAH Regulations in the United Kingdom).

Treatment of the soil in the affected areas was so complete that it now has a dioxin level below what would normally be found. The whole site has been turned into a public park, Seveso Oak Forest park. Some say that Seveso is now the least polluted place in Italy.

It could be argued that Seveso is a disaster that has not yet produced identifiable disastrous consequences. Several studies have been completed on the health of the population of surrounding communities. It has been established that people from Seveso exposed to TCDD are more susceptible to rare cancers but when all types of cancers are grouped into one category, no statistical significant excess has yet been observed.

Epidemiological monitoring programmes established as follows (with termination dates): abortions (1982); malformations (1982); tumours (1997); deaths (1997). Health monitoring of workers at ICMESA and on decontamination projects, and chloracne sufferers (1985).

The Seveso disaster gives valuable comparative insight into the effects of Agent Orange on [flora and fauna] in Vietnam, not to mention Vietnamese people as TCDD was an active chemical element in Agent Orange.

The documentary "Gambit" is about Joerg Sambeth, the technical director of Icmesa who was sentenced to five years in the first trial and whose sentence was reduced to two years and paroled on appeal.




  • Fuller, John G. (1979). Poison That Fell from the Sky. New York: Berkley Books.

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