What Happens to a Place After It’s Covered in Toxic Sludge?

View photos of Hungary’s toxic sludge disaster.

Hungarian authorities are currently struggling to contain the damage from a deluge of toxic sludge on Monday that resulted from a burst dam at an aluminum processing plant. At least four people were killed and over 100 injured by the 35 million cubic feet of sludge, which knocked cars off the road, burned through victims clothes and affected a 15 square mile area. Hundreds of people in several towns had to be evacuated by police. So just how long will it take for the region to recover from the sludge?

It depends on what’s in it. Greenpeace workers who took samples of the sludge on Tuesday are having them tested to determine what exactly rescue workers will be dealing with. Experts believe the substance, a byproduct of refining bauxite into aluminum, is likely to contain heavy metals, such as lead, as well as high levels of arsenic. If these chemicals are present in high amounts, the area’s soil could be contaminated for years to come. Children and pregnant women are most at risk, from high levels of lead, can cause birth defects and brain damage.

Once the sludge dries, the lead may be even more dangerous. If inhaled, the sludge dust can cause respiratory problems, even lung cancer.

Arsenic, which can lead to nerve damage, stomach pain, and some types of cancer, is extremely difficult to remove from soil and can be transferred into crops, threatening agricultural yields for years.

The most dangerous immediate factor is the sludge’s high alkaline level. The aluminum plant’s runoff has an extremely high ph level of around 13, meaning it can burn through the skin of those who come in contact with it. Most of the injuries reported so far have been alkali burns.

After the sludge itself is cleaned up, the affected soil will likely remain alkali, making it unsuitable for planting, and will have to be treated with acid before agriculture can resume (assuming it hasn’t been poisoned by lead.)

Hungarian authorities say the sludge has not yet entered the region’s water supply, but EU authorities worry that it could reach the Danube, one of Europe’s main waterways, and be carried to countries downstream. This could be catastrophic. When a cyanide-contaminated storage pond burst into local rivers near Baia Mare, Romania, in 2000, it wiped out all fish and plant life in a several hundred kilometer swathe. Two years after the accident, fish populations still hadn’t returned to their normal levels.

Authorities say the sludge itself will take a year to clean up. But it’s clear that the region will be feeling the health and economic effects of the spill for years to come.