Understanding the Seveso Disaster: Science, Impacts, and Policy Changes

Here's what we learned from one of the worst industrial disasters in history.

A state policeman pins up warning signs around the town of Seveso in Italy, following the area's contamination by a toxic cloud.
A state policeman pins up warning signs around the town of Seveso in Italy, following the area's contamination by a toxic cloud. Hulton Deutsch / Getty Images

The Seveso Disaster of 1976 was an industrial accident in which a chemical manufacturing facility in northern Italy overheated, releasing toxic gases into a residential community. It joins the ranks of Fukushima, Bhopal, Chernobyl, and Three Mile Island as one of the worst industrial accidents in the past century in terms of its effects on workers and residents.

The resulting environmental impacts led to the creation of tougher, more uniform environmental regulations and health protections throughout Europe.

Seveso: Before and During the Disaster

A small suburban town some 10 miles north of Milan, Italy, Seveso had a population of about 17,000 in the 1970s and was one of several towns in the area that formed a mix of urban, residential, and small farming areas. A nearby chemical plant was owned by ICMESA, a subsidiary of pharmaceutical giant Hoffman-La Roche, and run by the Givaudan corporation. The plant manufactured 2,4,5-trichlorophenol, used in the production of cosmetics and pharmaceuticals.

On the afternoon of Saturday, July 10, 1976, while residents of Seveso and the surrounding area were tending their gardens, running errands, or watching their children play, one of the buildings in the chemical plant became dangerously hot, causing temperature and pressure to rise inside one of the plant’s tanks.

When the temperature reached a critical level, a pressure release valve blew out, emitting a cloud of toxic gas containing sodium hydroxide, ethylene glycol, and sodium trichlorophenate. The gas cloud that drifted over the Seveso area also contained an estimated 15 to 30 kilograms of TCDD, technically known as 2,3,7,8-tetrachlorodibenzodioxin.

The Science Behind the Disaster

TCDD is one type of dioxin, a family of chemical compounds that are a by-product of industrial activities like bleaching wood pulp, incinerating garbage, and chemical production. Dioxin is also present in small amounts in the herbicide Agent Orange, which was used during the Vietnam War.

Dioxins are called persistent organic pollutants because they take a long time to break down in the environment. It is universally recognized as a carcinogen and can cause reproductive, immune, and developmental effects in mammals. Chloracne, a serious skin condition consisting of lesions, can also result from high exposures to dioxin.

The Aftermath

Within a few hours of the ICMESA gas release, over 37,000 people in the Seveso area were exposed to unprecedented levels of dioxin. Among the first to suffer, however, were the area's animals. 

Dead animals, especially chickens and rabbits kept as food, began to overwhelm the city. Many were slaughtered on an emergency basis to prevent people from eating them. (Dioxin accumulates in fatty tissue, and the vast majority of human exposures come from ingesting exposed animal fats.) By 1978, an estimated 80,000 animals had been slaughtered to avoid human consumption.

Despite exposure to high levels of dioxin, it was a few days before people began to feel the initial effects. As a result of the slow onset of symptoms, authorities did not immediately evacuate the area.

The response to the Seveso accident was widely criticized as slow and bungled. Several days passed before authorities announced that dioxin had been released from the facility; evacuation of the worst-affected areas took several more days.

The Legacy of Seveso

In 1983, a court convicted five chemical company officials for their role in the disaster. After several appeals, however, only two were found guilty of criminal negligence. Roche eventually paid about $168 million in damages to cover decontamination, a disposal dump, and new housing for affected residents. However, a subsequent civil suit on behalf of victims was unsuccessful. 

Despite a perceived lack of justice for victims, the Seveso disaster became a symbol of the need for more stringent industrial safety regulations in Europe and worldwide. In 1982, the Seveso Directive was enacted by the European Community to prevent such accidents, improve response to industrial disasters, and enforce an EC-wide regulatory safety framework.

Seveso is now associated with tough regulations that require any facility storing, manufacturing, or handling hazardous materials to inform local authorities and communities and to create and publicize measures to prevent and respond to accidents.

The other significant legacy of the Seveso disaster is the expanded understanding of how dioxin affects human health. Scientists continue to study Seveso survivors, and research into the long-term health effects of the disaster continues.

What Happened to the Factory?

The ICMESA plant is now completely closed, and the Seveso Oak Forest park was created above the buried facility. Beneath the wooded park sits two tanks that hold the remains of thousands of slaughtered animals, the destroyed chemical plant, and the most contaminated soil.

It is a quiet but potent reminder of the health risks posed by industrial toxins and the importance of robust safety regulation and enforcement.

View Article Sources
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