Superfund sites are normally fuming with hazardous substances, many of these toxic to humans and the environment.

When the U.S. government recognized areas contaminated with hazardous waste were threatening the health of communities, it created the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) — AKA Superfund — in 1980. If you’d like to learn a little more on Superfunds before reading ahead, check out my last post for a basic breakdown.

But back to the hazardous substances. According to the Environmental Protection Agency (EPA), there are a number of these found at Superfunds across the nation. These substances are used in a variety of industries, and they’re bad — like, really bad — for us.

National Geographic put together a list of these substances. Here are the top 5 most common, which can affect the health of people, especially if they’re exposed for long periods of time.

1. Arsenic — a natural element of the Earth and gray in color. Humans can intake arsenic in small amounts through food, water and the air. According to the EPA, “Superfund sites with a mining or smelting history may retain high levels of arsenic in soil or water.” Arsenic poisoning can lead to skin, lung and bladder cancers.
2. Lead — naturally occurring, but can be really harmful if inhaled or ingested, especially by children. According to the Centers for Disease Control and Prevention (CDC), prolonged exposure can lead to “high blood pressure, heart disease, kidney disease and reduced fertility.”
3. Mercury — also naturally occurring, and it’s found in the air, soil and water. Even small amounts of exposure can threaten human health. According to the World Health Organization, “Mercury may have toxic effects on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes.” WHO considers it one of the top ten chemicals “of major health concern.”
4. Vinyl Chloride — used to make polyvinyl chloride, which is used to manufacture plastic products. People are exposed to this substance by breathing contaminated air and drinking contaminated water. According to Safer Chemicals, this “chemical is a known human carcinogen causing liver cancer, brain cancer and some cancers of the blood. Vinyl chloride has also been associated with mammary (breast) cancer.”
5. Polychlorinated Biphenyls (PCBs) — industrial products or chemicals. PCBs are usually oily liquids or solids that are light yellow or colorless. According to the CDC, “the most commonly observed health effects in people exposed to large amounts of PCBs are skin conditions such as acne and rashes.” Some studies say PCBs are linked to cancer, specifically liver cancer.