Bottled water is often perceived as a safer alternative to tap water, largely due to beliefs that it is consistently filtered and free of lead, agricultural pesticides, and industrial pollutants that municipal systems might not fully eliminate. However, lab tests commissioned by the consumer watchdog app Oasis Health have challenged this perception, revealing that a higher price does not equate to purer water. These tests found plastic-derived 'forever chemicals,' known as PFAS, to be widespread in bottled water across various brands, from budget-friendly options like Deer Park and Poland Spring to premium choices such as Essentia and Topo Chico.

Forever chemicals are a category of synthetic compounds known for their water and stain-repellent properties. They are commonly used to coat the insides of plastic water bottles and their caps to prevent leaks, entering the water supply as byproducts of plastic production. These chemicals are exceptionally persistent, taking decades or even centuries to degrade in both the environment and the human body. Over time, PFAS accumulate in the environment, seeping into the water and food supply, becoming ubiquitous. Notably, contamination can also occur during the purification process, even for water packaged in glass bottles, if it is stored or filtered through plastic systems.

The accumulation of PFAS in the body's tissues can disrupt essential biological processes. This includes interfering with hormone regulation, sabotaging the body’s ability to clear out harmful cholesterol, and promoting cancer-causing inflammation. For pregnant women, PFAS exposure can disrupt fetal development, potentially leading to learning and developmental delays in children. Specific types of PFAS like PFOA have strong links to kidney and testicular cancer, liver damage, and thyroid disease, while PFOS is associated with kidney and thyroid cancer, liver damage, and high cholesterol.

Oasis Health analysts undertook a comprehensive study, scoring thousands of bottled water brands, including Deer Park, SmartWater, Dasani, and Fiji, among others. Their scoring methodology utilized a points-based system, where a base score out of 100 was adjusted by penalties for risks and bonuses for transparency. Products were penalized for missing third-party lab reports, the presence of contaminants, unsafe packaging materials (like certain plastics), or sourcing from municipal supplies. Bonuses were awarded for brand transparency, such as publishing test data. The final score placed each product into a clear risk band, ranging from ‘Excellent’ (90–100) to ‘Very Poor’ (below 60), providing a standardized, science-backed way for consumers to compare products.

The tests revealed concerning levels of PFAS in many popular brands. While the EPA sets a PFAS exposure limit at 0.4 parts per trillion (ppt), the health guideline most researchers agree on is 0.1 ppt. Most of the worst-performing brands contained PFAS concentrations of about 0.2 ppt, roughly double the health guideline. More alarmingly, Topo Chico registered 3.9 ppt, and Perrier 1.7 ppt, representing PFAS concentrations 39 and 17 times the safe limit, respectively. Deer Park also showed 1.21 ppt, 12 times the safe limit. Brands like Essentia, Dasani, Smartwater, and Aquafina each contained PFAS at 0.2 ppt. Fiji was the only product that did not exceed PFAS levels, with 0.05 ppt, but it did test positive for arsenic, albeit a trace amount that was still twice the EPA's stringent 0.004 ppt health advisory goal for PFOA, underscoring that even waters marketed as pure can contain persistent industrial pollutants.

One particularly alarming finding was Perrier Sparkling Water's high concentration of HFPO-DA, also known as GenX, a common replacement for PFOA. Although research on GenX is less extensive than for PFOA or PFOS, existing animal studies indicate concerning health effects, including an elevated risk of liver toxicity, lesions in the kidneys, and atrophied pancreas. The EPA has classified GenX as likely carcinogenic in humans, based on animal studies linking the chemical to liver, pancreas, and testicular tumors.

PFAS are pervasive contaminants, found not only in bottled water but also in numerous household items, from cookware to food wrappers. They can persist in the environment and human tissues for years or even decades. Many public health experts and organizations contend that there is no truly safe level of exposure to highly persistent, bioaccumulative, and toxic PFAS like PFOA and PFOS, especially as scientists link harmful health effects to increasingly minuscule concentrations. Consequently, official ‘safe’ limits for these chemicals in drinking water become obsolete almost as soon as they are established. For example, the EPA's recommended limit for PFOA alone plummeted from 400 ppt in 2009 to 70 ppt in 2016, with some states now enforcing limits as low as 0.1 ppt. This drastic tightening applies to just one of thousands of PFAS compounds, and research shows individuals typically carry a mixture of multiple PFAS in their bodies simultaneously. With over 200 million Americans believed to have PFAS in their tap water, the challenge extends beyond bottled water to a systemic environmental and public health issue.