The Lubizol plant in Rouen was classed as a Seveso site because of the nature of the chemicals – mainly additives for oils and lubricants – that it produces.
So what is Seveso?
There are 1,171 Seveso sites in France, and they are factories or manufacturing plants that have been identified as risky by authorities because of their “association with certain hazardous industrial activities”.
It's named after the town of Seveso in Italy, which was the site of a devastating industrial accident in 1976 which saw high levels of the toxic chemical dioxin released into the air.
The disaster prompted a Europe-wide approach to identifying and classifying high-risk sites.
The interactive map below has been put together by the Sciences et Avenir news website based on information from the French government.
Are they dangerous?
There are two types of Seveso site: “seuil haut” (high threshold) or “seuil bas” (low threshold) depending on the size of the risk. Each type has its own safety measures (classification regulations, labelling and packaging of substances and mixtures) to try to prevent accidents and plants must provide regularly updated risk assessments.
The aim is also that everyone knows exactly what is made there, so if there is an incident like a fire or a leak, emergency services have all the information that they need.
Clearly, given what has happened in Rouen, it's not a foolproof system. Indeed the blaze was the third serious incident at Lubrizol in recent years, including a gas leak in 2013 that caused a noxious pong that reached as far as England.
Where are they?
As you would expect, the Seveso sites are mostly clustered in industrial areas so there is a high concentration of such sites in Marseille, Lille, Le Havre and the outskirts of Paris. Having said that though, there are sites around the country, even in smaller towns or more rural areas such as the Dordogne and Périgord.
You can click on the interactive map above to find out if there is one near you, or near a place you are thinking of moving to. You can also find out if it is “high” or “low” risk.
If there are plans to set up a new Seveso site near where you are already living, any resident has the right to bring an action before the courts if they feel their rights are being infringed.