AZF Accident

On 21 September 2001, just 10 days after the heinous terrorist attacks of 9/11 in USA, it was time for the people of Toulouse in South-West France to hear the noise of explosions but because of entirely different reasons. An explosion that would create a crater of a depth 20 to 30 m, with a 200 m diameter. 

View of the crater created after the explosion

PRELUDE: The AZF site

The AZF factory in Toulouse was part of Great Parish, leading French producer of fertilizers, a group company TotalFinaElf. It was situated on a plot of 78 hectares, 5 kilometers from the city centre; the plant was built between the highway leading to Tarbes and the Garonne. Built in 1924, most of its installations dating from 1960.

The AZF plant produced mainly ammonium nitrate, ammonium nitrate-based fertilisers and other chemicals including chlorinated compounds.

On this cursed day, the AZF factory in Toulouse employed 470 people. About 80 people, also working permanently on the site, were used by nine external companies. The explosion occurred in a “downgraded ammonium nitrates” store which had off-spec ammonium nitrate storage.

In the coming sections we will see how this accident led to a series of policy changes in areas of risk management and specifications of ammonium nitrate based fertilizers.

The Accident Itself

Site of the disaster

Till date the cause of the explosion has not been pin-pointed. There have been various theories that have been hypothesized. The major ones are that it could be a human error, a terrorist attack, an underground explosion outside the AZF which acted as an initiator, electromagnetic disturbances in the EDF network. The case that went for prosecution considered this as a chemical accident where a chemical, which is a chlorine derivative ‘DCCNa’, was mistakenly stored in the hangar that had ammonium nitrate and these two chemical compounds reacted to lead to an explosive reaction.

Consequences of this Accident

The explosion unfortunately killed 31 people, including 21 working in the AZF factory. More than 4500 injured have been identified. 27 000 structures were destroyed property around the plant. Compensation of more than 2 Billion Euros has been paid since the accident.

Lessons from the accident

Even though the exact causes for the explosions have not been figured out but this accident left a big dent on the fertilizer industry and triggered a lot of policy changes in area of risk management.

The disasters at Toulouse reminded Europe that the control-based Seveso II directive (in particular its Safety Management System requirement) was not enough to prevent major a accidents turning into disasters.

Some of the major changes are:

1) The maximum content of nitrogenous fertilisers should very rapidly be limited to a maximum value of between 28 and 31.5% of nitrogen (80 to 90% of ammonium nitrate), which would reduce the risk of explosion and the risk of their use as explosives.

2) The Toulouse explosion showed the need to improve our knowledge of potential risks. The Toulouse disaster has created a strong awareness concerning the coexistence cities industries. To address these issues, the law of 30 July 2003 on risk prevention plans to develop “Technology Risk Prevention Plans" (PPRT). This law puts a long-term perspective on urban development around hazardous plants. It also gives local councillors a stake in the risk prevention decision making process, instituting Local Committees for Information and Dialogue (CLIC). Public opinion thus becomes involved in decision-making, the aim being to make choices more acceptable to local stakeholders.

3) The accident that occurred in Toulouse on the 21st of September should lead to a re-examination of the position of many factories that are situated in an urban environment. Based on the AZF Disaster the French Government has put new regulations in place from July 2003. These regulations concern new measures to improve the efficiency of future construction limitations and to deal with existing dangerous situations of urbanism around SEVESO sites.

4) To have the corresponding hazard studies brought up to date (taking into account the risks of the domino effect in production factories between ammonium nitrate stores and ammonia stores).

Sources :

1) http://www.azf.fr/

2) Urban growth analysis within a high technological risk area, Case of azf factory explosion in toulouse (france), Casita project: www.adpc.net/casita/Case/AZF_CASE_STUDY_REPORT_v2.doc

3) Economic and Poverty times: http://www.grida.no/files/publications/environment-times/kobetimes_1415.pdf

4) Press release:Explosion at the azf factory in toulouse: The general inspectorate for the environment

Seveso Disaster : the Dioxin Crisis

ICMESA plant after the accident

Summary data  Date : July 10th 1976 Place : the ICMESA factory at Meda near Milan, Italy Type of accident : dioxin release Outcome : 725 people evacuated, 2000 people treated for dioxin poisoning, 4% of the local farm animals dead and 80 000 additional animals killed to prevent contamination from filtering up the food chain.

Overview of the accident

We are in the chemical plant ICMESA owned by the Swiss company Givaudan (group Hoggmann-Laroche), located in Meda, a small town about 20 kilometres north of Milan.

On Saturday 10th July 1976, the control system of a chemical reactor for the production of trichlorophenol, a component of several herbicides, was damaged, and the temperature rose beyond the limits. The explosion of the reactor was avoided by the opening of safety valves, but the high temperature reached had caused a change in the reaction that led to a massive formation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), substance commonly known as dioxin, a high toxic compound.

This event became internationally known as the Seveso disaster since Seveso is the name of a neighbouring municipality that was the most severely affected.

After four days, Hoffmann-La Roche laboratories identified the causative agent (TCDD). By Thursday 15 July, five days after the accident, ICMESA had informed the authorities of the presence of toxic components while the population continued to live in a contaminated environment.

Zone A represents the area with the highest level of 

dioxin contamination, followed by Zone B and Zone R

The evacuation was ordered on Saturday 24 July, two weeks after the accident. On July 26, the first inhabitants were evacuated and 225 people left their homes. During the days that followed days, the authorities realized that the affected area was larger and 500 more people were evacuated.

The dioxin cloud, released into the air from the chemical plant, contaminated a densely populated area. The four most impacted municipalities were Seveso (a 1976 population of 17 000), Meda (19 000), Desio (33 000), and Cesano Maderno (34 000). Two other municipalities, Barlassina (6000) and Bovisio Masciago (11 000) were subject to post accident restrictions.

 The amount of TCDD released by the accident is subject to much debate. It is possible that between 1 and 30 kg of dioxin was release in the atmosphere.

The Seveso disaster areas were divided based on soil contamination levels. Zone A, the most contaminated area with more than 50 mg of TCDD per square meter and covering 110 ha, was completely evacuated and fenced-off with entry prohibited.

In the next-most contaminated areas, zone B (between 5 and 50 mg/m2) and zone R (below 5 mg/m2), farming as well as consumption of local agricultural goods and meats were strictly prohibited.

Consequences of the accident

A child diagnosed with chloracne

In the days following the accident, the trees turned yellow and dropped their leaves and thousands of pets died. In order to prevent TCDD from entering the food chain over 80 000 animals had to be slaughtered.

15 children were quickly hospitalized with skin inflammation. 1 600 people of all ages had been examined and 447 were found to suffer from skin lesions or chloracne. Pregnant women who wanted an abortion had been allowed to, which was usually unthinkable in Catholic Italy at that time.

The release of dioxin has not resulted in deaths. However, the plant manager, Paolo Paoletti, was assassinated shortly after by an armed group.

Lessons from the accident

The best-known consequence of the Seveso disaster was the creation of the European Community's Seveso Directive, a new system of industrial regulation.

The new European directives, Seveso I and II, were then used to identify sites at risk of major accidents and to establish a policy to prevent major accidents.

The resulting directives are currently applied to around 10 000 industrial establishments where dangerous substances are used or stored in large quantities, mainly in the chemicals, petrochemicals, storage, and refining sectors.

The industries handling dangerous substances above certain thresholds must regularly inform the public, providing safety reports, a safety management system and an internal emergency plan.

Sources :

- Lessons from seveso, David C. Wilson, Chemistry in Britain, July 1982, available at : http://www.davidcwilson.com/Seveso.pdf

- Case Study: The Dioxin Crisis in Seveso, Italy, available at : http://westox.site.wesleyan.edu/the-dioxin-crisis-in-seveso-italy/

- 4 Seveso: A paradoxical classic disaster, B. De Marchi, S. Funtowicz, and J. Ravetz, United Nations University, available at :http://archive.unu.edu/unupress/unupbooks/uu21le/uu21le09.htm

- Seveso Dioxin Cloud, Gilbert Cruz, TIME, May 2010, available at : http://www.time.com/time/specials/packages/article/0,28804,1986457_1986501_1986449,00.html

- Que s’est-il passé à Seveso ?, Matthieu Combe, April 2012, available : http://www.natura-sciences.com/pollution/catastrophe-seveso/que-sest-il-passe-a-seveso.html

- Chemical Accidents (Seveso III) - Prevention, Preparedness and Response, European Comission , November 2012, available at : http://ec.europa.eu/environment/seveso/index.htm