Chemical contaminants in drinking water

Along its journey, water picks up contaminants from industrial and municipal discharges, agricultural and urban runoff, atmospheric pollution, drinking water treatment, bottles it’s sold in, and leaching from the pipes delivering water to your tap. Contaminants may include arsenic, lead, copper, volatile organic compounds (VOCs), pesticides, pharmaceuticals, bacteria and pathogens, and chloride and disinfection byproducts (DBPs). There are also contaminants of emerging concern that are not well-regulated or treated yet, including nano- and microplastics, and per- and polyfluorinated alkyl substances (PFAS).

Water quality also varies with season and weather events. For example, dry periods/droughts can concentrate contaminants in source waters, making treatment less efficient. Algal blooms during summer months produce dissolved organic matter that supports growth of bacteria, requiring enhanced disinfection treatment, which results in higher levels of DBPs. Also, salt and other chemicals used to deice roads during winter storms can leach into ground and surface waters.

Health issues related to contaminated drinking water include increased risk of cancer (DBPs), neurological impairment (lead), Parkinson’s Disease (pesticides), and hormone disruption (estrogenic chemicals in plastic), among others. For example, exposure to DBPs can increase the risk of kidney cancer over time,¹ as well as low birth weights and preterm births in infants exposed to higher concentrations in utero.² Consumption of water from private wells in regions where pesticides have been in use has been linked to increased risk of Parkinson’s Disease.

Sources of drinking water

We get our drinking water from various sources, including municipalities, private wells, and/or bottled water. But those are not regulated equally. Under the Safe Drinking Water Act, the federal government regulates municipal water but not private wells³ or bottled water, though the latter is regulated by most states.⁴ And municipal water tests do not account for contaminants picked up after it leaves the facility, including lead from pipes in homes.

Though bottled water may be convenient and essential if other water sources are heavily contaminated, there are drawbacks. Bottled water may contain substantially more nano- and microplastics than tap water, with polypropylene caps a major contributor.^4,5 Water bottled in glass can reduce some contaminants, with less than half the levels of estrogenic contaminants than in plastic bottles.⁶ But even water in glass bottles contained higher levels of microplastics than tap water, likely due to use of plastic tubing and filters used to process the water, as well as plastic caps.⁴

What’s in your water?

Step one before deciding on a filtration system is to learn what’s in your water. If you’re on municipal water, download your utility’s report on water quality to learn about water quality issues in your service area. Also check the Environmental Working Group’s (EWG) Tap Water Database for standard exceedances and emerging contaminants that might not be reported by your utility.

If you’re on a private well, it’s important to know about land uses near the aquifer you’re drawing from that could contribute contaminants to your water supply. These might include agriculture, gas stations or dry cleaners, as well as industrial operations or a major road that receives salt during winter. Because groundwater can travel great distances, it’s a safer bet to have it tested for nitrates, heavy metals, and organics like pesticides, petroleum compounds, and PFAS. To test your water, see options listed below in Resources.

For both municipal and private well sources, you should determine whether your home’s pipes contain lead. The U.S. mandated lead-free solder in pipes and lead-free service lines in homes built after 1986, so homes built before then may have pipes containing lead.

Decision time

After determining whether your city’s water or your well water exceeds allowable levels for contaminants of concern, and whether your pipes contain lead, it’s time to decide on a filtration system. 

• If your water meets standards and you don’t have lead pipes, then a simple system like a fridge or pitcher filter is probably adequate to remove things like chlorine and DBPs.
• If contaminants exceed allowable levels or you have lead contamination, then it would be best to choose a more efficient filtration system for your drinking water.
• If your source water contains elevated levels of bacteria, viruses, or amoeba, fridge filters won’t do much to eliminate them.⁷ That may require treatment with ultraviolet light (UV).

There are many filtration options to choose from, each having strengths and weaknesses, depending on which contaminants you’re concerned with and cost, space, and time considerations in your home. It may come down to a choice between convenience versus efficacy.

Products available for home use include pitcher, fridge, faucet, beneath sink, countertop, and whole house filters. Pitchers (e.g. Brita) & refrigerator filters are the simplest but not the most efficient if you have high levels of contaminants. On the other end of the spectrum, beneath sink cartridges and reversed osmosis may have a higher capacity for contaminant removal.

Technologies that remove contaminants include the following:

• Physical filters screen sediment and larger particles (does not include microplastics).
• Ion exchange filters trap dissolved minerals, nitrates, and heavy metals, releasing sodium in exchange.
• Activated carbon, either granular or solid block, bind chlorine, DBPs, heavy metals, VOCs, and contaminants like pesticides and pharmaceuticals. Efficiency for removing these contaminants varies so check their certification. Activated carbon filters do not effectively remove contaminants like nitrate, perchlorate, and 1,4 dioxane.
• Reversed osmosis uses a semipermeable membrane to remove nitrates, minerals, heavy metals, and organics, as well as microplastics depending on pore size. Downsides to RO: it also removes essential minerals,⁷ which must be added back, and produces a large volume of wastewater (note – don’t water edible plants with that, as it contains higher levels of contaminants than your tap water).
• Ultraviolet systems kill bacteria and pathogens.

Note – with any of these options, be sure to follow guidelines for replacing filters. Letting them go too long can result in high concentrations of contaminants desorbing from the overloaded filter, which I describe in my Peak Gunk post.

Because many of these systems have plastic housing, pitchers, or other components, it’s unclear whether they add nano- and microplastics or plasticizers to your filtered water. For example, I found one system with no plastic components but ships filter refills in plastic packaging. With anything, removing most is better than nothing. If your filter system has a plastic receiving pitcher, consider transferring the filtered water to a glass or stainless-steel container. If you’re concerned about the potential for microplastics to shed from plastic components of any of these systems, consider pouring filtered water through something like a Chimera plastic-free water filter system.

Filter recommendations

I’ve listed recommendations below for filter systems from the Environmental Working Group, a source I respect, or from looking at performance sheets or certifications. I have not had these tested myself and do not receive a commission for their purchase. Before you buy any filter, it would be a good idea to check the company’s website for a Performance Data Sheet to see the full list of contaminants filtered out and at what percentage.

EWG’s recommendations for pitcher and countertop water filters:

• Epic Pure Pitcher (removed 47% hexavalent chromium, 98% PFAS, 100% arsenic, 9% nitrate, 100% DBPs.)
• Clearly Filtered Water Pitcher w Affinity Filtration Tech (removed 79% hexavalent chromium, 100% PFAS and arsenic, 8% nitrate, 100% DBPs.)
• Zero Water (removed 85% hexavalent chromium, 100% PFAS, arsenic, and nitrate, 82% DBPs.)
• PUR Plus faucet filter (removed 86% hexavalent chromium, 79% PFAS, 41% nitrate, 100% DBPs.)

If your water is contaminated by PFAS, here are EWG’s Top 3 recommendations for filters:

• Black Berkey (removes DBPs, >99.6% chlorine and >99.9% chloramine, 99 to >99.9% heavy metals, and >99.9% organics like pesticides, pharmaceuticals, petroleum, and PCBs, and >99.9% PFAS.) Note – though tests on their system’s removal of microplastics aren’t complete, it filters particles above 24-26 nm, thus it’s likely it also removes nanoplastics and microplastics above that size.
• Culligan Zero Water (removes >99.4% chlorine and >99.6% chloramine, 99.1% lead, 97.8 to 99.4% pesticides, 99.6% PFAS, 96.5% microplastics.)
• EPIC Pure Pitcher (removes >99.9% chlorine and >90.4% chloramine, 99.8% DBPs, 96 to 99.9% lead, 97.8 to 99.4% pesticides, 99.9% PFAS, 99.9% microplastics, allows trace minerals like calcium and magnesium to pass through.)

Whatever you choose, honor that you can’t clear all potential contaminants and that it will be an improvement. Even imperfect water is essential for life.

Resources and references

For municipal water customers, find out about your water:

• Search online for your town’s Consumer Confidence Report or use the EPA’s link: https://ordspub.epa.gov/ords/safewater/f?p=136:102::::::
• EWG’s Tap Water Database https://www.ewg.org/tapwater/

Labs for water analysis:

• For your state’s list of commercial, ELAP-certified labs (Environmental Laboratory Accreditation Program): https://www.epa.gov/system/files/documents/2023-03/state-cert-programs-certify-labs-to-conduct-drinking-water-analyses.pdf
• Commercial lab: https://mytapscore.com/products/advanced-city-water-test
• The Silent Spring Institute’s resource for help you interpreting results for groundwater: https://privatewells.silentspring.org

References:

1. Villanueva, C. M. et al. 2004. Disinfection byproducts and bladder cancer. Epidemiol. 15:357-367.
2. Currie, J. et al. 2013. Something in the water: contaminated drinking water and infant health. Canadian Econ. Assoc. 46:791-810.
3. EPA: https://www.epa.gov/privatewells
4. NRDC 24 October 2025. Bottled water vs. tap water.
5. Mason, S. A. et al. 2018. Synthetic polymer contamination in bottled water. Front. Chem. Vol. 6.
6. Wagner, M. and Oehlmann, J. 2009. Endocrine disruptors in bottled mineral water: total estrogenic burden and migration from plastic bottles. Environ. Sci. Pollut. Res. 16:278-286.
7. Watson, S. K. 27 July 2018. Which water is best for health? Hint: don’t discount the tap. NPR: Eating and Health.