Dioxin: Seveso disaster testament to effects of dioxin

May 6, 1999

Dioxin: Seveso disaster testament to effects of dioxin

Third in a series

By MICK CORLISS Staff writer

MILAN, Italy-- Today, birds chatter in the trees and people take Sunday strolls along the paths of Bosco delle Querce, or Seveso Oak Forest park. One would not suspect that beneath the lush green carpet and vegetation lurk the poisonous remains of a chemical disaster nearly 23 years ago.

The origin of the park, roughly 15 km north of Milan in Italy's Lombardy region, can be traced back to the afternoon of July 10, 1976.

A little after noon that Saturday, a valve broke at the Industrie Chimiche Meda Societa Azionaria chemical plant in Meda, releasing a cloud of chemicals containing dioxin that wafted an estimated 50 meters into the sky.

Carried southeast by the wind, the toxic cloud enshrouded the municipality of Seveso and other communities in the area.

About 3,000 kg of chemicals were released into the air, according to some researchers. Among them was 2,4,5 trichlorophenol, used in the manufacture of herbicides, and anywhere from about 100 grams to 20 kg of dioxin, said Dr. Paolo Mocarelli of the Hospital of Desio. The accident was not immediately noticed. No one was at the plant when it happened and ICMESA -- the company responsible -- failed to swiftly address the event.

The first sign of health problems, burn-like skin lesions, appeared on children a few hours after the accident. Beginning in September of that year, chloracne, a severe skin disorder usually associated with dioxin, broke out on some of the people most exposed to the cloud.

Authorities began an investigation five days after the accident, when animals such as rabbits began to die en masse. Nearly two weeks later, a chemist deduced that the cause was dioxin. And within three weeks, some 736 people living closest to the plant were evacuated.

About 37,000 people are believed to have been exposed to the chemicals, according to researchers familiar with the case.

Approximately 4 percent of local farm animals died, and those that didn't -- roughly 80,000 animals -- were killed to prevent contamination from filtering up the food chain.

The affected areas were divided and subdivided based on soil contamination levels. Zone A -- the most contaminated area, covering 110 hectares -- was completely evacuated and was later turned into the park it is today, Seveso Oak Forest.

In Zones B and R, the next-most contaminated areas, farming as well as consumption of local agricultural goods and meats were strictly prohibited.

Not only did exposure to one of the most toxic chemicals known to humanity change the lay of the land and the lives of local people, it also altered the life of Dr. Mocarelli.

Mocarelli was put in charge of a laboratory set up two weeks after the accident to test people for health problems. The first day on the job, he initiated a series of tests that today have surpassed 1 million, he said.

At the time of the accident, the technical knowhow for testing dioxin concentrations in people did not exist, so Mocarelli's lab ran neurological, obstetric and other tests on those believed to have been exposed.

"I got the inspiration to save one sample (of blood from each person)." 

"(Samples) like this more or less," he says holding his hand in front of his face and indicating the fingernail of his pinkie to show an amount of roughly 1 milliliter. "Just in case it would be possible to measure TCDD (dioxin) someday."

Fortunately, this became possible in 1987, the doctor said.

Now the nearly 30,000 samples Mocarelli put in the refrigerator following the accident are paying research dividends as he works with the U.S. Centers for Disease Control and Prevention, headquartered in Atlanta, to unravel the accident and its implications more than two decades later.

The Seveso accident is likely the most systematically studied dioxin contamination incident in history and, in Mocarelli's words, a chance experiment on human beings.

The chance experiment has shed light on the threat dioxin poses. "Probably the strongest effect is on reproduction," Mocarelli said.

In the first seven years after the accident, an incredibly high proportion of females were born to parents who were exposed to the chemical cloud: 46 females compared to only 28 males. Usually, the proportion is roughly equal.

This was the first time a chemical had been observed to change the sex ratio, Mocarelli said.

"There is no other molecule known to induce change in the sex ratio," he said, adding that this implicates dioxin as a hormone disrupter.

Victims of the Seveso accident also reported symptoms of other afflictions -- immune system and neurological disorders as well as spontaneous abortions -- but studies found no link to dioxin.

Minor increases in some forms of cancer were found in one exposed group. Studies have suggested a link between dioxin and cancer.

The lessons of Seveso may offer clues to how dioxin might signal its presence in Japan.

Such telltale signs might include a shift in the sex ratio in areas suspected of contamination, or an appearance of chloracne or skin disorders, such as those found in former employees of a waste incinerator in Nose, Osaka Prefecture.

The blood-dioxin contamination level of one former Nose worker was almost twice the average of the most contaminated group surveyed in Seveso, although far below the most contaminated. 

In addition, research using the Seveso samples taken over the last two decades may help determine what dioxin levels are dangerous, and help in making more accurate risk assessments in other nations.

Today, Mocarelli and his team are conducting research on the children of victims of the incident, as well as on dioxin's long-term carcinogenic properties. These studies will likely help enrich debate on the topic around the world as well as in Japan, which is now in the throes of its own reassessment of the chemical's effects. 

Apart from monitoring victims of the accident, another type of monitoring continues as well.

Beneath Seveso Oak Forest's grassy undulations are two massive concrete tanks -- the resting place of the top 40 cm of soil removed after the explosion.

It is also the final resting place of the contaminated animals that were slaughtered, the factory -- taken apart brick by brick by workers in protective suits -- as well as other buildings coated by the fallout.

Water seeps from the two giant tombs that lie just below the park's surface into another container where the dioxin is treated.

The facilities, overseen by the park service, are constantly monitored for leaks. Ironically, today the soil here "has lower dioxin levels than in average areas," according to park administrator Antonio Mambriani.

A desolate chunk of land after the accident and until reclamation was completed in the 1980s, the area is now a place where families gather on Sundays. Animals have returned to the park and adjacent 13-hectare nature reserve.

"In 1984, this place was a desert. Now, you see it is covered with trees," Mambriani said. "If anything good came of dioxin, it was probably this park and the green it gave Seveso."

Another gift of the incident has been the data on the effects of dioxin. Reconstruction of the event using samples taken over time have helped clarify how long dioxin stays in the human body, as well as the different effects it has on children and adults.

After 20 years of work to decipher the lessons of Seveso, Mocarelli has simple advice to offer.

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