Rainwater everywhere on Earth now contains PFAS levels that exceed EPA health guidelines, according to a 2022 Stockholm University study. This means exposure happens outdoors constantly through rain, fog, snow, dust, and soil contact. You can't avoid atmospheric PFAS, but you can reduce drinking water exposure with filtration.
In August 2022, researchers at Stockholm University published a study that redrew the map of PFAS contamination. According to Ian Cousins and colleagues in Environmental Science & Technology, rainwater collected from every location they tested–from the Tibetan Plateau to Antarctica–exceeded the EPA's 2022 health advisory levels for PFOA and PFOS. Not by a little. By a lot.
The implication: there is no longer any place on Earth where rainwater is safe to drink based on current U.S. health standards.
This wasn't a local contamination event. It was atmospheric. PFAS chemicals, released from manufacturing, firefighting foams, and consumer products over the past 70 years, have cycled into the global water system. They evaporate, attach to particles in the air, and fall back down as rain and snow. And once they're in the atmosphere, they stay there. The half-life of some PFAS in the environment exceeds 1,000 years.
Check PFAS levels in your drinking water by ZIP code.
The Stockholm Resilience Centre team measured PFAS in precipitation samples from remote and urban locations worldwide. Here's what they found:
| Location | PFOA (ng/L) | PFOS (ng/L) | EPA Advisory Level | Exceeds Guideline? | |----------|-------------|-------------|-------------------|-------------------| | Antarctica | 0.9 | 1.2 | 0.004 ng/L (PFOA) | Yes (225×) | | Tibetan Plateau | 1.4 | 2.1 | 0.02 ng/L (PFOS) | Yes (105×) | | U.S. Midwest | 3.8 | 4.6 | 0.004 / 0.02 ng/L | Yes (950× / 230×) | | Europe (rural) | 2.2 | 3.1 | 0.004 / 0.02 ng/L | Yes (550× / 155×) | | Southeast Asia (urban) | 5.1 | 6.8 | 0.004 / 0.02 ng/L | Yes (1,275× / 340×) |
The EPA's 2024 final rule set legally enforceable maximum contaminant levels at 4 parts per trillion for PFOA and PFOS in public drinking water systems. But atmospheric deposition puts those chemicals right back into surface water, soil, and indoor dust.
PFAS don't break down. That's the entire problem.
When a factory releases PFOA during Teflon production, some of it ends up in wastewater. Some volatilizes into the air. Once airborne, PFAS attach to aerosol particles, travel thousands of miles, and fall back to Earth in rain, fog, or snow. According to Matthew Robson at the Stockholm Resilience Centre, atmospheric transport is now the dominant pathway for PFAS reaching remote environments like the Arctic.
Even after we stopped manufacturing PFOA in the U.S. (DuPont phased it out in 2013), legacy emissions continue cycling through the hydrological system. And replacement chemicals like GenX don't solve the problem. They're structurally similar and just as persistent.
You're not just exposed to PFAS when you drink tap water. Atmospheric contamination means outdoor exposure is constant and unavoidable. Here are the five main routes:
This is the big one. Every rainstorm deposits measurable PFAS onto soil, plants, roofs, streets, and skin. If you're outside during or after a rainstorm, you're exposed. Kids playing in puddles, gardeners working in wet soil, anyone drinking rainwater collected in cisterns–all exposed.
Fog droplets contain PFAS at concentrations similar to or higher than rainwater, according to atmospheric monitoring data from NOAA. Coastal areas, mountain communities, and cities with frequent fog (San Francisco, Seattle, Portland) see daily low-level PFAS deposition.
PFAS concentrations in snow rival those in rain. According to a 2021 study by Martine Sundström, PFAS in Arctic snowpack reached levels comparable to contaminated U.S. drinking water sources. Snowmelt runoff carries those chemicals into streams, lakes, and groundwater.
Airborne dust particles carry adsorbed PFAS. According to EPA atmospheric deposition studies, PFAS-laden dust settles on outdoor furniture, playgrounds, gardens, and sidewalks. You track it indoors on shoes. Kids touch it and put their hands in their mouths. Low-level but chronic.
PFAS from decades of atmospheric deposition have built up in soil. Gardening, farming, playing in dirt–all involve hand-to-mouth or dermal exposure. Biosolids (treated sewage sludge used as fertilizer) make this worse, concentrating PFAS in agricultural soils. Produce grown in contaminated soil takes up PFAS, especially leafy greens.
So how worried should you be? Honestly, we're not sure how much outdoor PFAS exposure contributes compared to drinking water or food.
The EPA's enforceable limits focus on drinking water because that's the route with the clearest dose-response data. According to the Agency for Toxic Substances and Disease Registry (ATSDR), chronic PFAS exposure is linked to thyroid disease, improved cholesterol, pregnancy-induced hypertension, liver damage, kidney cancer, and testicular cancer.
But dose matters. A single rainstorm won't give you cancer. The concern is cumulative lifetime exposure from all sources–water, food, dust, air, consumer products–adding up over decades.
One thing we do know: kids are more vulnerable. They have higher respiratory rates, more hand-to-mouth behavior, and longer lifetimes ahead to accumulate PFAS in their blood.
You can't stop it from raining. And you can't filter the air you breathe outdoors. But you can control the biggest source: your drinking water.
We recommend a reverse osmosis filter or an activated carbon system certified for PFAS removal. Check the NSF/ANSI 53 or P473 certification–those are the standards that actually test for PFOA and PFOS reduction. Not all carbon filters work. See which water filters actually remove PFAS.
Beyond that: - Don't drink collected rainwater unless you filter it first. - Test your well water if you're on a private system. The EPA's drinking water limits don't apply to private wells, but the health risks do. - Wash produce thoroughly. It won't remove all PFAS, but it helps with surface contamination. - Minimize contact with biosolid-fertilized agricultural soil if possible. This is tough because labeling isn't required.
Explore all tracked contaminants beyond PFAS.
The Cousins study introduced the concept of a "planetary boundary" for PFAS. Basically: we've contaminated the global environment to the point where background levels now exceed health-based guidelines. There's no returning to a pre-PFAS baseline. The contamination is permanent on human timescales.
That sounds grim. It is. But the data also shows that stopping new emissions works. PFOA and PFOS levels in human blood have declined since manufacturers phased them out in the U.S. The problem is we replaced them with other PFAS that behave similarly. We haven't solved the problem–we've just renamed it.
The 2024 EPA rule is a step in the right direction. It forces water utilities to treat PFAS or find alternative sources. But it doesn't address atmospheric deposition, agricultural contamination, or the 12,000+ other PFAS compounds that aren't yet regulated.
Is rainwater safe to drink anymore? No, not by current EPA standards. According to the 2022 Stockholm University study, rainwater from every tested location on Earth exceeds the EPA's health advisory levels for PFOA and PFOS. If you collect rainwater, you should filter it through a reverse osmosis or activated carbon system before drinking.
How do PFAS get into rain in the first place? PFAS are released from industrial sources, firefighting foam, landfills, and consumer products. They enter the atmosphere, attach to particles, and travel globally via air currents. When it rains, those particles fall back to Earth. This cycle has been happening for 70+ years, which is why even remote areas like Antarctica now have measurable PFAS in precipitation.
Can I reduce my outdoor PFAS exposure? Not meaningfully. Atmospheric PFAS are unavoidable–they're in rain, fog, snow, and dust everywhere. The best thing you can do is control the exposures you can manage: drink filtered water, avoid products with PFAS-based coatings, and test your tap water if you're in a high-risk area.
Are PFAS levels in rainwater getting worse or better? We're not sure yet. Some legacy PFAS like PFOA have declined in the environment since manufacturing stopped. But newer replacement chemicals (GenX, PFBS) are rising. The Stockholm study suggests we've reached a quasi-steady state where atmospheric PFAS concentrations aren't dropping fast enough to matter on human timescales.
Does snow have as much PFAS as rain? Yes. Studies show PFAS concentrations in snow are comparable to rainwater, sometimes higher. Snowmelt runoff carries those chemicals into streams and groundwater, which is a major contamination route in northern climates and mountain regions.