Drinking clean, pure water is essential for maintaining optimal health, yet over 2 billion people worldwide still lack access to safe drinking water.1 The increasing contamination of tap water with harmful substances has led many to seek alternatives like bottled water and home filtration systems in an effort to protect their well-being.
Yet, despite this shift, there’s still a lack of comprehensive scientific data on the safety of these water sources, particularly when it comes to the presence of hazardous chemicals and pollutants. This prompted researchers from California to investigate the safety and aesthetic qualities of three common drinking water options — bottled water, tap water and household-treated tap water.
Recently published in the journal PLOS Water,2 their findings reveal alarming levels of carcinogenic chemicals and other dangerous pollutants across all types of drinking water, raising concerns about what is truly safe to consume.
Cancer-Linked Chemicals Detected in Drinking Water
To conduct their analysis,3 the researchers collected 100 bottled water samples from 89 different brands, 603 tap water samples and 111 household-treated tap water samples from the San Francisco Bay Area. They tested these for 100 different contaminants, including metals, volatile organic compounds (VOCs), disinfection byproducts and microbial indicators, as well as evaluated factors that influence consumers’ choices in water source, including taste, odor and color.
One of the most alarming findings was the widespread presence of trihalomethanes (THMs) in all tested sources of drinking water. THMs are a group of disinfection byproducts that are formed when chlorine, which is used to treat drinking water, reacts with natural organic matter in the water. THMs are known carcinogens and have been linked to increased liver toxicity as well as reproductive and developmental problems.
The study revealed that tap water samples contained the highest concentrations of these chemicals, accounting for 94.5% of its total cumulative toxicity. Meanwhile, THMs accounted for 76.7% of the total toxicity observed in household-treated tap water.
Moreover, the researchers found that 2% of tap water samples exceeded the regulatory threshold for THMs, which is set at 80 micrograms per liter — a limit that is already higher than levels deemed safe for long-term health. In household-treated tap water, 25% of the samples still contained chloroform, a common THM, at concentrations that surpassed health-protective benchmarks.
In addition to THMs, the study found troubling levels of heavy metals in both tap and household-treated waters. Lead was detected in 51% of tap water samples and 30% of the household-treated samples, which researchers suggest is a result of aging water infrastructure and corroded pipes. Exposure to lead, especially in children, causes severe neurological damage and developmental delays.
Additionally, arsenic was found in 8% of household-treated tap water samples and 3% of tap water samples, while uranium was detected in 2% of both household-treated and direct tap water samples. Both contaminants pose significant long-term health risks, including cancer and kidney damage.
Bottled Water Is Not a Safer Alternative
While consumers often switch to bottled water due to concerns about the taste or safety of tap water, the featured study4 revealed that bottled water is not necessarily a safer option. While it generally displayed lower overall toxicity, it was not free from contamination.
Researchers found that 8% of bottled water samples exceeded California’s strict regulatory limit for THMs, with chloroform detected in 32% of the samples. Interestingly, some petroleum-derived compounds, including benzene and toluene, were detected exclusively in bottled water and were not found in tap or household-treated samples. As the researchers stated:5
“In BW [bottled water], additional detections and exceedances suggest that bottle production and processing may play a role in water quality. Two petroleum-derived compounds — benzene and toluene — were detected in BW only.
One benzene detection was in exceedance of the health benchmark, and all five toluene detections were below the health benchmark. One possibility is that these contaminants were introduced to bottled water products during processing.”
Another surprising finding was the prevalence of heterotrophic bacteria in bottled water, found in 43% of the samples. Although these bacteria are not typically associated with pathogens, their presence contradicts the common perception of bottled water as a purer alternative. According to the authors:6
“These findings corroborate previous studies identifying HPC [heterotrophic plate count] in BW, which found detections in 30% to 71% of samples. While tap water samples are likely to have HPC as well because of its ubiquitous presence in the environment, these findings are particularly interesting in BW because of marketing claims about the purity of BW.”
The results call into question the assumption that bottled water is inherently safer or cleaner than tap water. Both sources carry their own risks, and while bottled water addresses some aesthetic concerns, it still has its fair share of health-related issues you need to watch out for.
Bottled Water Also Exposes You to Endocrine-Disrupting Chemicals
The use of plastic water bottles introduces additional health concerns beyond the contaminants found in the water itself. The featured study7 noted two major categories of endocrine-disrupting chemicals (EDCs) associated with plastic water bottles — microplastics and per- and polyfluoroalkyl substances (PFAS). Long-term exposure to these EDCs through regular consumption of bottled water could have cumulative effects on your health.
Microplastics leach from the plastic bottle itself or is present in the water source. In fact, a January 2024 study8 published in the Proceedings of the National Academy of Sciences revealed that consumers could be ingesting approximately 240,000 tiny plastic particles for every liter of bottled water.
Microplastics contain various additives and chemicals, including bisphenols (such as BPA and its alternatives), phthalates and heavy metals, which interfere with the endocrine system in multiple ways.9 Bisphenols are known to mimic estrogen, leading to hormonal imbalances, reproductive issues and certain cancers.10 Phthalates, on the other hand, are associated with antiandrogenic effects, impacting reproductive health and development.11
As for PFAS (aka “forever chemicals”), a 2021 study12 conducted by researchers at Johns Hopkins University found their presence in 39 out of over 100 bottled water samples tested. PFAS infiltrates bottled water through contaminated source water, manufacturing processes or cross-contamination.
These chemicals disrupt thyroid function, leading to metabolic disorders and developmental issues. They’ve also been associated with decreased fertility, altered immune function and increased risk of cancer.13
EWG’s Tap Water Database — What Contaminants Are in Your Water?
If you want to know what other contaminants are lurking in your water, you can get the results of your local drinking water analysis from your water utility. It’s your right to view the annual water quality report from your area, which should highlight contaminants of concern (although there could be others that are legally “safe” but still pose a long-term health risk).
The Environmental Working Group (EWG) also offers a comprehensive Tap Water Database that allows consumers to access detailed information about the quality of their local drinking water. This database provides insights into the contaminants detected in municipal water supplies, including their levels and potential health risks.
By simply entering your zip code, you’ll be able to learn about specific pollutants found in your area, such as lead, chlorine and various pesticides. This resource allows you to make informed decisions about your water quality and encourages local utilities to improve their standards.
Invest in a High-Quality Filtration System for Your Home
While the results of the featured study14 raised concerns about the effectiveness of some water filtration systems, the authors also emphasized that “household-scale treatment may reduce the potential for aesthetic issues and health risks of tap water.”
The key is to choose a system designed to effectively target the pollutants present in your water supply. One of the best water filters I’ve found so far is the Pure & Clear Whole House Water Filtration System, which uses a three-stage filtration process — a micron sediment pre-filter, a KDF water filter and a high-grade carbon water filter15 — to filter out chlorine, detergent byproducts and other contaminants.
Ideally, your best bet is to filter the water at both the point of entry into your home and at points of use. This means installing filters at the main water supply line entering your home and again at specific locations where water is consumed or used, such as the kitchen sink and showers.
For additional guidance, the EWG offers a helpful water filter guide that allows you to search by filters type, technology and specific contaminants. This resource help you make informed decisions about which filtration system is the most suitable for your home.16
More Ways to Protect Your Drinking Water
In addition to using high-quality water filtration systems, below are several effective strategies to protect the quality of your drinking water at home while contributing to a healthier environment:17
1. Stay informed about local water quality by regularly checking reports from your municipal water supplier. These reports provide details on contaminant levels, safety compliance and any advisories. You can also get local drinking water quality reports from the U.S. Environmental Protection Agency (EPA).
2. Maintain your plumbing system, especially if your home has older pipes made of lead or galvanized metal. Regular inspections and replacing old pipes prevent harmful substances from leaching into your water.
3. Store bottled water properly by keeping it in cool, dark environments. Avoid leaving it in warm areas or direct sunlight, which cause plastic to degrade and release chemicals into the water. Better yet, eliminate the use of plastic water bottles and opt for glass or stainless steel containers instead.
4. Adopt good environmental practices by properly disposing of hazardous materials like chemicals and medications. Reducing plastic use and participating in local clean-up efforts also protect water sources.
5. Test your water regularly, especially if you use well water or live in an older home. Home water testing kits help you identify contaminants such as lead, nitrates and bacteria, allowing you to take appropriate action to ensure your water is safe.
Progesterone Mitigates the Effects of EDCs in Bottled Water
To effectively minimize exposure to endocrine-disrupting chemicals (EDCs) from plastic water bottles, the most straightforward approach is to avoid using them altogether. Instead, use glass or stainless steel containers to store water.
However, if you find yourself frequently using bottled water or exposed to other sources of EDCs in your environment, I recommend using transmucosal progesterone combined with vitamin E via buccal or gingival administration (i.e., rubbed into your gums), as detailed below, to counteract the harmful effects of these chemicals.
Progesterone is a hormone that acts as a switch to “turn off” estrogen’s activity, helping mitigate the effects of phthalates and other estrogenic compounds. By counteracting the effects of these disruptive chemicals, progesterone helps restore balance in your body’s hormonal systems.
