Contaminants show up in drinking water, soil, food, household products, indoor air, and even inside the human body. Many are invisible and odorless, which means exposure often happens without any obvious warning. Understanding where these substances concentrate helps you reduce contact with the ones that matter most.
Drinking Water
Tap water is one of the most common routes of exposure to environmental contaminants. Two categories get the most attention right now: lead and PFAS, sometimes called “forever chemicals” because they don’t break down naturally.
The EPA finalized new limits for PFAS in drinking water, setting maximum levels at 4 parts per trillion for the two most studied compounds (PFOA and PFOS) and 10 parts per trillion for three others. To put that in perspective, a part per trillion is roughly equivalent to one drop of water in 20 Olympic swimming pools. These chemicals leach into water supplies from firefighting foam, industrial discharge, and manufacturing sites, and they’ve been detected in public water systems across the country.
Lead enters drinking water not from the source itself but from old pipes, solder, and fixtures between the water main and your faucet. The EPA recently lowered its lead action level from 0.015 mg/L to 0.010 mg/L, with water systems required to comply by late 2027. Homes built before 1986 are most likely to have lead service lines or lead solder in their plumbing.
Soil, Especially in Cities
Soil absorbs decades of pollution from leaded gasoline, paint chips, industrial activity, and pesticide use. Lead occurs naturally in U.S. surface soils at about 22 parts per million (ppm), but urban soils regularly exceed that by a wide margin. In Chicago, lead levels in metropolitan soil samples were five times higher than in nearby rural forest soils. Community garden testing across U.S. cities paints a vivid picture: median lead levels ranged from about 47 ppm in Philadelphia gardens up to 950 ppm in parts of Boston, with individual samples in New York City reaching nearly 9,000 ppm.
Arsenic and cadmium also accumulate in garden soils, particularly in areas near former industrial sites or where pressure-treated wood was used for raised beds. California soils carry a median arsenic background of 5 ppm, higher than most of the rest of the country. These metals can be taken up by root vegetables and leafy greens, creating a direct path from soil to diet.
Food, Particularly Seafood
Mercury is the contaminant most closely tracked in the food supply, and fish is the primary source of human exposure. Mercury concentrations vary enormously by species. Fresh or frozen salmon averages just 0.022 ppm, while canned light tuna comes in around 0.126 ppm. Albacore tuna, whether canned or fresh, averages roughly 0.350 ppm. At the high end, swordfish averages 0.995 ppm, with some samples reaching 3.22 ppm. Bigeye tuna, popular in sushi, averages 0.689 ppm.
The pattern is straightforward: larger, longer-lived predatory fish accumulate more mercury because they eat smaller fish that have already absorbed it. Choosing smaller species like salmon, sardines, or shrimp dramatically reduces your exposure while still providing the nutritional benefits of seafood.
Beyond mercury, pesticide residues appear on conventional produce (the EWG’s annual lists track which fruits and vegetables carry the highest loads), and PFAS have been found in food packaging, particularly grease-resistant wrappers and containers used in fast food.
Household and Personal Care Products
Your bathroom cabinet is a surprisingly significant source of chemical exposure. Phthalates, parabens, and other hormone-disrupting compounds are common ingredients in everyday products. The three phthalates most frequently used in personal care items show up in perfumes, deodorants, soaps, shampoo, nail polish, and cosmetics. Parabens serve as preservatives in many of these same products. Oxybenzone, a UV-filtering chemical, is found in sunscreens, lip balm, and cosmetics with sun protection claims.
The exposure doesn’t stop at the bathroom. Air fresheners, fabric softeners, and cleaning products also contain phthalates, which is why switching personal care brands alone may not fully reduce your levels. One intervention study with adolescent girls found that even after replacing all their personal care products with cleaner alternatives, phthalate levels didn’t drop as much as expected, likely because scented household products remained in the home.
Indoor Air
Radon is the most dangerous indoor air contaminant you’ve probably never tested for. It’s a naturally occurring radioactive gas that seeps into homes through cracks in foundations, and it’s the second leading cause of lung cancer. The EPA recommends taking action if your home’s radon level reaches 4 picocuries per liter (pCi/L) or higher, and suggests considering remediation even between 2 and 4 pCi/L. Risk varies dramatically by geography: the EPA divides the country into three zones based on predicted radon potential, with the highest concentrations in the northern Great Plains, the Appalachian region, and parts of the upper Midwest.
Other indoor air contaminants include volatile organic compounds (VOCs) released by new furniture, paint, carpet, and cleaning sprays. Formaldehyde off-gasses from pressed-wood products and certain insulation materials. These tend to be highest in newer or recently renovated spaces with limited ventilation.
Legacy Industrial Sites
Some of the most persistent contaminants trace back to chemicals that were banned decades ago but refuse to leave the environment. PCBs, once widely used in electrical transformers, capacitors, and industrial fluids, have been identified at more than 500 of the EPA’s roughly 1,600 designated hazardous waste sites. Low levels of PCBs can still be found essentially everywhere on Earth. They continue to enter the environment through leaking old equipment, poorly maintained waste sites, and landfills that accepted PCB-containing consumer products before the 1979 ban.
These legacy chemicals matter because they accumulate in the food chain. PCBs concentrate in the fat of fish and animals, meaning people who eat contaminated fish from rivers or lakes near former industrial sites face higher exposure than the general population.
Inside the Human Body
Perhaps the most unsettling place contaminants are found is in human tissue itself. Microplastics, tiny fragments of synthetic materials, have now been detected in blood, lungs, and placentas. Researchers analyzing human blood vessels found microplastic concentrations of 1.6 micrograms per milliliter, composed of polymers from common plastics like polyester, polyethylene, and polystyrene. Lung tissue samples have contained particles as small as 1.6 micrometers (far too small to see). In one study, 149 microplastic particles were identified in a single human placenta, ranging from 20 to 307 micrometers, made of materials found in food packaging, textiles, and household items.
The health consequences of microplastics in human tissue are still being studied, but their sheer presence in organs like the placenta underscores how pervasive synthetic material contamination has become.
Reducing Your Exposure
You can’t eliminate all contaminant exposure, but targeted steps make a real difference. For drinking water, home filters certified to NSF Standard P473 are verified to remove PFOA and PFOS. The two most effective technologies are granular activated carbon filters and reverse osmosis systems. Reverse osmosis removes the broadest range of contaminants, including lead, PFAS, and many dissolved solids, though it wastes more water than carbon filters.
For soil, test your garden before growing food, especially if you live in an older urban area. Raised beds filled with clean soil and compost offer a simple workaround. For food, vary your fish choices and favor smaller, shorter-lived species. For indoor air, test your home for radon (kits cost under $20) and ventilate well during and after renovation projects. For personal care products, fragrance-free options tend to contain fewer phthalates, and checking labels for paraben-free formulations is now easy given how many brands have moved away from them.