Across the United States, water quality is shaped by more than rainfall, geology, and geography. The country’s major biomes—from Arctic tundra and boreal forests to deserts, grasslands, wetlands, and coastal marshes—also influence how contaminants move through the environment. Yet when it comes to PFAS, the map is not as simple as “one biome, one risk.”
Per- and polyfluoroalkyl substances, commonly known as PFAS, are manufactured chemicals used in products designed to resist water, grease, stains, and heat. They have been detected in drinking-water supplies, rivers, groundwater, soils, sediments, fish, and human blood. Their distribution reflects industrial activity, military and airport operations, firefighting-foam use, wastewater discharges, landfills, and atmospheric transport as much as it reflects natural ecosystems.
Understanding the relationship between US biomes and PFAS pollution helps explain why contamination can appear in very different landscapes—and why protecting water requires more than a single national map.
What a biome map can—and cannot—tell us
A biome map groups regions according to broad ecological characteristics such as climate, vegetation, soil, and wildlife. Common US biome categories include temperate forests, grasslands, deserts, tundra, freshwater systems, and marine or coastal environments.
These ecological boundaries are useful for understanding water movement and environmental vulnerability. Forest soils may store and slowly release contaminants. Wetlands can retain pollutants in sediment while also transporting them during floods. Arid landscapes may have little surface water but can contain highly vulnerable groundwater aquifers. Coastal ecosystems can receive PFAS from rivers, wastewater systems, and atmospheric deposition.
However, biomes do not produce PFAS. The primary source is human activity. A remote wetland may contain PFAS if it receives contaminated runoff from upstream, while a heavily industrialised city may have relatively low concentrations in a particular water body if its discharge is controlled and its water source is protected.
The most useful approach is therefore to combine ecological maps with information about land use, hydrology, population centres, industry, waste management, and known PFAS sources.
Why PFAS behave differently from many other pollutants
PFAS include thousands of related compounds. Some, such as PFOA and PFOS, have been studied extensively, while many newer or less well-known compounds remain difficult to detect and assess. Their chemical structures contain strong carbon-fluorine bonds, which make them resistant to heat, water, and natural degradation.
This persistence has earned PFAS the nickname “forever chemicals.” The term is not a precise scientific classification, but it communicates an important reality: once released, many PFAS can remain in the environment for years or decades.
PFAS are also highly mobile. Depending on the compound and local conditions, they can:
- Move through soil into groundwater.
- Travel downstream in rivers and streams.
- Remain dissolved in water rather than settling quickly into sediment.
- Accumulate in plants, fish, birds, and mammals.
- Cycle between surface water, groundwater, soil, and biological systems.
- Reach distant locations through wastewater, wind, ocean currents, and atmospheric transport.
Chain length, functional groups, temperature, soil composition, organic matter, and pH all affect how an individual PFAS behaves. This is one reason why a simple “contaminated versus clean” map can hide important differences in exposure and risk.
Temperate forests: extensive watersheds and hidden groundwater pathways
The eastern United States contains large areas of temperate deciduous and mixed forests, including the Appalachian region, the Great Lakes basin, and much of New England. These landscapes often receive substantial rainfall, and dense networks of streams, wetlands, and aquifers connect rural communities with urban and industrial areas.
Forest cover can slow runoff and reduce soil erosion, but it does not necessarily stop dissolved PFAS. Rainfall moving through contaminated soil can carry PFAS into shallow groundwater and streams. In areas with fractured bedrock, pollutants may travel through cracks and underground channels that are difficult to map.
PFAS concerns in forested regions may be associated with airports, military bases, industrial facilities, wastewater treatment plants, landfills, and historic use of aqueous film-forming foam for firefighting. A forest downstream of a former training site may appear pristine while receiving contamination through groundwater or a small tributary.
The Great Lakes region illustrates the complexity of this issue. It combines major freshwater resources with dense manufacturing, large cities, wastewater infrastructure, and extensive shipping activity. PFAS entering tributaries or wastewater systems can affect drinking-water sources, fish, and sediments across state and national boundaries.
Grasslands and agricultural regions: water scarcity increases vulnerability
The Great Plains are dominated by prairies, croplands, and grazing lands. The region includes major aquifers, including the High Plains Aquifer, which supports drinking water and irrigation for millions of people.
In agricultural landscapes, PFAS may enter the environment through industrial emissions, landfill leachate, contaminated biosolids, wastewater reuse, and runoff from developed areas. The use of treated sewage sludge, or biosolids, on land has attracted particular attention because some PFAS can remain in the material and later migrate into soil or water.
Where rainfall is limited, groundwater is often the most important source of drinking water. That makes aquifer protection especially important. Groundwater contamination can be difficult and expensive to remediate because the water moves slowly and pollutants may spread over large areas.
Surface water and groundwater are also closely linked in prairie landscapes. A stream can recharge an aquifer under some conditions, while groundwater can feed the stream during dry periods. Contamination can therefore move in both directions rather than remaining confined to its original source.
Deserts and the Southwest: less water, longer contamination concerns
Desert ecosystems across the Southwest receive limited rainfall, but intense storms can generate rapid runoff. Dry riverbeds, washes, and ephemeral streams may remain empty for months before carrying large volumes of water during a storm.
This pattern creates a distinctive PFAS challenge. Contaminants deposited in dry soils or stored near industrial sites can be mobilised quickly during heavy rainfall. At the same time, scarce groundwater resources may have limited natural replenishment, increasing the consequences of a contaminated aquifer.
Urban growth, military installations, aviation facilities, semiconductor manufacturing, waste sites, and water-reuse systems are important factors in parts of Arizona, Nevada, New Mexico, California, and Texas. In water-stressed areas, communities may rely on a small number of wells or on heavily managed surface-water supplies. A single contamination event can therefore place pressure on already limited alternatives.
Desert ecosystems also show why “low rainfall” does not mean “low pollution risk.” Less water can mean less dilution. Persistent chemicals may remain concentrated in groundwater or in isolated pools that support wildlife during dry periods.
Wetlands and freshwater ecosystems: natural filters with limits
Wetlands, lakes, ponds, rivers, and floodplains play a central role in the US water cycle. They can slow water movement, trap sediment, support biodiversity, and provide valuable habitat. These functions sometimes reduce the spread of certain pollutants.
PFAS behave differently from contaminants that strongly attach to sediment. Many PFAS remain dissolved in water, allowing them to pass through wetlands and travel downstream. Some compounds can still interact with organic matter, sediments, and biological tissues, but wetlands should not be treated as permanent PFAS filters.
Flooding can redistribute contamination. When a river overtops its banks, PFAS in water or sediment may reach agricultural fields, homes, wetlands, and wildlife habitat. Repeated flooding can create a cycle in which contaminants move between sediment and surface water.
Fish are an important concern in freshwater ecosystems. PFAS can accumulate in aquatic organisms, and fish consumption may become a relevant exposure pathway for people who fish regularly. State advisories do not all use identical testing methods or thresholds, so local guidance should be checked before consuming fish from potentially affected waters.
Tundra and boreal regions: remote does not always mean protected
Alaska contains tundra, boreal forest, glaciers, wetlands, rivers, and coastal ecosystems. Many areas are remote, but PFAS have been detected in locations influenced by human activity, including military installations, airports, fire-training areas, and communities with limited waste and water infrastructure.
Cold conditions can slow many natural processes, while seasonal freeze-thaw cycles may alter the movement of contaminants through soil and groundwater. Permafrost changes add another layer of uncertainty. As frozen ground thaws, stored chemicals can potentially become more mobile, although the behaviour of PFAS depends strongly on local hydrology and soil conditions.
Subsistence fishing and hunting make environmental contamination especially significant for some northern and Indigenous communities. When local foods are central to culture, nutrition, and household economies, a water-quality problem can affect far more than drinking water alone.
Coastal and marine ecosystems: the downstream destination
Coastal regions receive PFAS from rivers, stormwater, wastewater discharges, landfill leachate, industrial sites, and atmospheric deposition. Estuaries are particularly important because they sit at the boundary between freshwater and saltwater and support nurseries for fish, shellfish, birds, and marine mammals.
PFAS can enter coastal food webs. Shellfish and fish may be exposed through contaminated water and sediments, while birds and mammals can receive PFAS through their diet. Because some coastal species travel widely, contamination in one location may have ecological effects beyond the original discharge area.
Wastewater treatment deserves careful attention. Conventional treatment plants are not generally designed to destroy PFAS. Some processes may transfer PFAS from wastewater into sludge or other waste streams rather than eliminate them. Advanced technologies, including granular activated carbon, ion exchange, and high-pressure membrane systems, can reduce PFAS in water, but each has operating costs and waste-management requirements.
Where PFAS monitoring is most useful
A reliable assessment should combine environmental sampling with source investigation. Useful questions include:
- Is the water source downstream or down-gradient from a known PFAS facility?
- Are there airports, military bases, landfills, factories, or fire-training sites nearby?
- Does the area use biosolids, reclaimed water, or private wells?
- Are local rivers, wetlands, or aquifers connected to the suspected source?
- Have fish, sediment, groundwater, and finished drinking water all been tested?
- Which PFAS were included in the laboratory analysis?
Testing only for PFOA and PFOS may not reveal the full picture. Laboratories and regulators increasingly use broader analytical methods, but no single test captures every PFAS compound. Results also depend on sampling location, season, rainfall, treatment processes, and detection limits.
What US regulations mean for communities
In April 2024, the US Environmental Protection Agency established legally enforceable drinking-water limits for several PFAS under the Safe Drinking Water Act. The rule set a maximum contaminant level of 4.0 parts per trillion for PFOA and PFOS individually, alongside limits for certain other PFAS and mixtures.
These federal limits apply to public water systems, not every private well. Private well owners are responsible for arranging and interpreting their own testing. State requirements may also differ, and water suppliers may be working through monitoring and compliance timelines.
Residents should consult their water provider, state environmental agency, or local health department for current results. Home filtration can reduce exposure when the equipment is properly selected and maintained. Certified products using activated carbon or reverse osmosis may be appropriate for certain PFAS, but filters must be replaced on schedule. A neglected filter can become a maintenance problem rather than a solution.
Reading the biome map with the PFAS map
Biome maps reveal how ecosystems function. PFAS maps reveal where human activities have altered those systems. Neither map is sufficient on its own.
The most informative picture emerges when ecological regions are viewed alongside watersheds, groundwater flow, industrial history, wastewater infrastructure, and community exposure data. A protected forest, productive prairie, desert aquifer, northern wetland, or coastal estuary may look very different, but each can be connected to PFAS through water.
That is the central lesson: PFAS pollution follows pathways, not biome labels. Better monitoring, transparent reporting, source reduction, and effective treatment can help protect both public health and the ecosystems that depend on clean water.