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Hank: This is a beautiful and wonderful world, but there are some places that you probably don't want to visit. Some of them, called Superfund sites in the US, are contaminated with all kinds of toxic junk which poses a threat to anything living nearby. The sites that require long-term cleanup are put on the Environmental Protection Agency's national priority list, or NPL. Currently there are over 1,000 of them. So here are seven toxic sites that are -- or were -- being cleaned up by the Superfund program.

Let's begin with the site that started it all: the Love Canal in Niagara Falls, New York. This was supposed to become a canal and provide hydroelectric power, but the project was abandoned and left a huge hole in the ground. In the mid 1900s the the Hooker Chemical Company used the hole to dump and bury containers of around 19,000 metric tons of mixed industrial chemicals.

These were byproducts from things like dyes, perfumes, rubber, and resin production, which are not good for humans or the environment and are considered hazardous waste. By 1978, the chemicals had begun seeping up from the ground and residents noticed that something smelled...toxic.

The people that came in contact with the contaminants ended up with health issues like chemical burns, miscarriages, and possibly an increased risk of cancer. Later that year and in 1980, President Jimmy Carter declared two federal environmental emergencies, and evacuated over 900 families from their homes. Over the next two decades, the buildings were renovated, contaminated soil was moved into more secure landfills, and a permanent drain system was installed to collect chemical-filled groundwater called leachate.

The leachate is pumped to an off-site treatment plant and filtered using activated charcoal, which is basically just carbon atoms with a bunch of pores between them. These pores allow toxic chemicals, especially carbon containing ones to bind to the filter, making relatively clean water that can be treated along with normal sewage.

The Love Canal site was declared safe as of 2004, but the landfills where they relocated toxic materials are still proving to be environmental challenges. At the very least, this disaster led to congress passing the CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act), or Superfund bill in 1980 which created an official program to deal with contaminated sites.

This next site was added to the NPL in 1990, Reed-Kepler Park in West Chicago. It's a community area and swimming pool that happened to be right next to a landfill where the Rare Earths facility was dumping radioactive waste for 40 years until the early 1970s. Most of the waste was sand-like chinks of thorium, radium, and uranium called mill tailings and these radioactive elements are unstable.

They emit high energy particles that can knock electrons off of other atoms, this is called ionizing radiation. It's the kind of radiation that you don't want to mess with. Gamma radiation is especially dangerous in high concentrations. It can easily pass through human skin and damage DNA or other parts of your cells, which can lead to cancer.

So starting in 1997 the contaminated soil and debris was dug up and shipped off to a waste treatment facility, likely to be contained in these engineered chambers called embankments. And in 2010, the site was officially declared decontaminated and you can relax by the pool without worrying about radioactive particles.

Another notorious site was the Hart Senate office building in Washington D.C., which closed down when 30 employees were infected with anthrax bacteria.

In September and October of 2001, letters containing anthrax spores were maliciously sent to congressional leaders and members of the news media. These spores are a form of the bacterium protected by a protein shell which lie dormant until they enter a host, usually inhaled, ingested, or through a scrape on your skin. Then they become active infectious anthrax bacteria causing severe lesions, flu-like symptoms and potentially death.

The site cleanup involved fumigation with chlorine dioxide gas, which is reactive and steals electrons from molecules. It's an oxidizing agent and it's a really good bacteria killer. See, these chemical reactions can break up the bacterial cell membrane and molecules inside... and even the tough protein shell that protects the anthrax spores.

The EPA also use sandia decontamination foam, which is made from chemicals you can find in stuff around your house. Surfactants, like and air conditioner, make holes in the spore's outer shell, and oxidizing agents like in toothpaste get inside and break down important cellular stuff. After a rapid cleanup effort, this site was considered safe again in 2002.

Next up is the Blackburn and Union Privileges site in Walpole, Massachusetts, which was added to the NPL in 1994. It's been used for industrial and commercial purposes since the 1600s, which generated a huge amount of hazardous waste. The soil and groundwater were contaminated with things like lead, arsenic, and certain harmful volatile organic compounds, or VOCs, which easily become gases.

These VOCs, like some polycyclic aromatic hydrocarbons and benzine, could contribute to health problems like eye and throat irritation and liver and kidney damage or even cancer. But that's not all, at one point the site was used to manufacture brake and clutch parts for cars, which involved the fibrous compound asbestos.

As we now know, asbestos is really dangerous if it gets inside you. The tiny particular fibers can physically damage cells, cause some scarring, and even increase the risk of some cancers, like mesothelioma.

During initial cleanup in 2009, around 1,200 kilograms of contaminated soil, and nearly 27 metric tons of asbestos debris were sent to an off-site facility, probably a carefully designed landfill. But even today there is still tons more cleanup to do before the area is considered safe again.

Now these Superfund sites can get pretty dangerous but that has not stopped the state of Montana from charging two whole US dollars to view The Berkeley Pit. It used to be a huge copper mine in the 1900s with pumps that removed the groundwater so it wouldn't flood, but once the mine shut down in 1982, The Berkeley Pit started filling up with water. Plus, all the heavy metals and toxic chemicals.

It's super acidic because of sulfuric acid from sulfide minerals in the rocky mine tunnels that react with oxygen in the water. And all of the metals in the put give the water some weird colors: brownish-red, probably because of iron compounds, and bluish-green thanks to the copper. So definitely not water that you would want to swim in unless you are a specialized microbe.

In fact, in 1995 a flock of snow geese landed in the pit for a couple of days and 342 of them died because of chemical burns. The water is contained in the pit for now, but if it reaches a critical level, about 1,650 meters above sea level, the contamination will seep back into nearby groundwater and even into nearby Silver Bow Creek. And this would be really bad news. Some of the toxic water could even get into the Clark Fork River and make its way down to where we live here in Missoula.

To keep water levels from rising too quickly, since 2003 a nearby treatment plant is pumping away surface water that would normally flow into the pit. That plant is undergoing studies, tests, and upgrades to treat water from The Berkeley Pit starting in the 2020s at the latest. Right now their strategy is to add calcium oxide, which reacts with the water and other stuff inside, like it can convert sulfuric acid into calcium sulfate, making the water less acidic. As the water gets less acidic, the metals will start forming these sludgy clumps that can be filtered out. In the meantime, the pit water is gradually rising toward the critical level, so we will have to make sure that treatment technologies will be up to the challenge... and fast.

Speaking of water, 200 miles of the Hudson River in New York is one of the largest Superfund sites in the country. Between 1947 and 1977, General Electric poured nearly 600,000 kilograms of this group of man-made chemicals called polychlorinated biphenyls or PCBs into the Hudson River. PCBs are resistant to acids, bases, and heat, so they were used as insulation when electrical devices like transformers and capacitors were being manufactured, but at a huge environmental cost.

The PCBs that were dumped built up in river sediments and inorganic materials like wood or living things. That's why you're not supposed to eat fish from the Hudson, because PCBs are fat soluble and easily stored in their fatty flesh. In our bodies, they can bind to lots of molecules and damage DNA, and are linked to lots of health issues, including cancer, thyroid disease, and learning and memory problems.

Between 2009 and 2015 the river was dredged, meaning that mud and PCBs in the bottom of the river were scooped out and moved to a hazardous waste landfill, but cleanup and habitat restoration is still ongoing and the river, sediment, and life nearby will be monitored for years to come.

Our last Superfund site is basically every homeowners worst nightmare, thanks to CTS of Asheville, a company in North Carolina that made electrical components for car parts and hearing aids. From the 1950s to the 1980s the company was using a solvent called trichloroethylene or TCE to remove grease from metal parts. A lot of it ended up contaminating the local groundwater which feeds into wells that give water to people's homes.

TCE is a non-flammable, colorless substance with a sweet, burning taste that some of the residents could make out. And it can damage liver and kidney cells, and may even cause cancer. Plus, TCE can affect the central nervous system, although scientists aren't quite sure what the mechanism is.

Since 2012 when the site was officially placed on the NPL, residents have been given water filtration systems, but now most of them use the clean municipal water supply instead of wells. The EPA is also using a technology that essentially vacuums up the TCE from the soil and groundwater, called a soil vapor extraction system.

Like all these sites, it seems like this cleanup will take a while and require a lot of different technologies. It's pretty safe to say that we need to be more careful about producing wastes and how we store or decontaminate the most toxic compounds. These Superfund sites can get really bad for the environment, and for humans. Our cleanup efforts are improving, but in the future, we really should avoid making more of these huge dangerous problems in the first place.

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