Why PFAS Are Called Forever Chemicals in Our Water

PFAS is short for a family of thousands of human-made chemicals. Factories began making them in the 1940s. Because they resist heat, water, and grease, they went into many everyday products. You can find them in nonstick pans, stain-proof carpet, waterproof jackets, food wrappers, and firefighting foam. For decades, few people worried about where they ended up.

The problem is that PFAS almost never break down. Each molecule is built around a chain of carbon atoms bonded to fluorine atoms. The bond between carbon and fluorine is one of the strongest in all of chemistry. Sunlight, heat, and bacteria that break down most pollutants barely touch it. So once a PFAS molecule forms, it can last for decades in soil, water, and living things. That is why people call them "forever chemicals."

This lasting nature causes two linked problems. First, PFAS spread far from where they were used. Second, they build up over time, a process called bioaccumulation. Small amounts that enter a river or a body do not simply wash away. They collect. Over years, even tiny doses can add up to levels that concern health scientists.

PFAS reach drinking water by several paths. Factories that make or use them can release them into rivers and the air. Firefighting foam is a major source. When crews train with it at airports and military bases, the foam soaks into the ground. Landfills also leak PFAS as rain filters through buried waste. From the soil, the chemicals seep into groundwater. That groundwater feeds the wells many towns rely on. In the fictional town of Birchmill, the water utility found PFAS in one of its wells and had to shut it down while it planned a fix.

Because PFAS are now widespread, the federal government set its first national limits. In April 2024, the Environmental Protection Agency issued a rule for drinking water. It set the limit for two of the most studied PFAS, called PFOA and PFOS, at 4.0 parts per trillion each. A part per trillion is an extremely small amount, roughly one drop in 20 Olympic-size swimming pools. The low limit shows how potent these chemicals are thought to be. The rule is still in motion. Water systems must meet the limits by April 2029. In May 2026, the agency proposed letting eligible systems apply for a two-year exemption, to April 2031, which would give some utilities more time to install treatment. The exemption would not be automatic for every system, and the limits would stay at 4.0 parts per trillion. The proposal was not yet final as of September 2026.

Removing PFAS from water is possible, but it is not simple. Utilities use three proven methods: granular activated carbon, ion exchange resin, and reverse osmosis. Granular activated carbon is the most common choice. Here is how it works. Water flows into a tall tank packed with grains of specially treated carbon. Each grain is riddled with tiny pores, so a handful has an enormous surface area. As the water passes through, PFAS molecules stick to the carbon surface and stay behind. The cleaned water flows out the bottom. Over time, though, the carbon fills up with captured PFAS. Once it is saturated, it can no longer hold more, and PFAS begin to pass through. So operators must test the water and replace or reactivate the carbon before that point is reached.

Treatment works, but it is costly. A carbon system can cost a utility a great deal to build and to keep running. Large cities can spread that cost across many customers. Small rural systems cannot. A town with only a few hundred connections may face a bill it can barely afford. For these small systems, meeting the new limit is a real challenge, which is one reason EPA has proposed letting eligible systems apply for more time.

There is another way to think about the problem. Treatment removes PFAS after they have already entered the water. Source reduction tries to stop them from entering at all, by limiting how and where the chemicals are made and used. Treatment protects people today but must run forever. Source reduction prevents future contamination but does nothing about the PFAS already in the ground. Communities are weighing both approaches as the science, and the rules, keep developing.

1. What makes the bond between carbon and fluorine important to why PFAS are called forever chemicals?
2. According to the passage, name two ways that PFAS get into drinking water sources.
3. The passage describes how a granular activated carbon system cleans water. Put its steps in order, and include what operators must do before the carbon becomes full.
4. Why would a small rural water system have a harder time meeting the PFAS limit than a large city system? Use details from the passage.
5. What is the federal limit for PFOA and PFOS, and what did EPA propose about the deadline? Why does the passage say the rule is still in motion?
6. The passage describes both treating water and reducing PFAS at the source. Explain which approach prevents the problem and which one manages it, and give one tradeoff of each.