Bottled water contains more than just water. Even after purification, it can carry trace amounts of disinfection byproducts, minerals, plastic-derived compounds, and in some cases, industrial contaminants like PFAS. Most of these chemicals fall well below safety thresholds set by federal regulators, but the specifics matter, especially when storage conditions come into play.
Disinfection Byproducts
Before bottled water reaches you, it typically goes through filtration, reverse osmosis, and a disinfection step, often using ozone or chlorine. These treatments kill bacteria effectively, but they also react with naturally occurring organic material and minerals in the source water, creating a class of chemicals called disinfection byproducts.
The most common ones in bottled water are bromate (formed when ozone reacts with bromide), chlorite, and haloacetic acids. In testing across multiple brands, bromate levels in bottled water have been measured at around 0.1 micrograms per liter, far below the EPA’s maximum of 10 micrograms per liter. Haloacetic acids like dichloroacetic acid have been found at roughly 0.6 micrograms per liter, also well under the 60 microgram limit. Not every brand shows detectable levels of these compounds. In one study of ten brands, bromate appeared in only one, while haloacetic acids showed up in about half.
The FDA sets its own allowable limits for bottled water that mirror EPA standards for tap water: 0.010 mg/L for bromate, 0.060 mg/L for the five regulated haloacetic acids, and 0.080 mg/L for a group of chlorine byproducts called trihalomethanes. Residual chlorine itself is allowed up to 4.0 mg/L, though most bottled water uses ozone rather than chlorine, so chlorine residues are uncommon.
Chemicals That Leach From Plastic
The bottle itself is a source of chemicals. Most single-use water bottles are made from PET plastic, which can release several compounds into the water over time. The ones researchers focus on most are BPA (a plasticizer linked to hormonal effects), phthalates (a family of softening agents), and antimony (a metal used as a catalyst in PET manufacturing).
A 2021 review in the Journal of Water and Health compiled data from studies worldwide. BPA concentrations in bottled water ranged from 0.01 to 5.7 micrograms per liter. Phthalates showed wider variation: one common type (DBP) ranged from trace levels up to 82.8 micrograms per liter, while another (DEHP) reached up to 64.0 micrograms per liter. These upper values came from bottles that had been stored for extended periods or in warmer conditions.
Storage temperature is the single biggest factor in how much plastic leaches into the water. A Chinese study tracked antimony release across different temperatures: after one week at refrigerator temperature (4°C), antimony levels stayed between about 2 and 8 nanograms per liter. At room temperature, levels roughly doubled. At 70°C, the kind of heat a bottle might reach sitting in a hot car, antimony surged to as high as 2,604 nanograms per liter. BPA followed the same pattern. Both compounds continued leaching over four weeks but at a decreasing rate, suggesting the release eventually plateaus.
Are These Levels Dangerous?
Under normal storage conditions, the answer from current research is no. A 2025 cross-sectional study assessing endocrine-disrupting chemicals in bottled water found that hazard quotients for all measured compounds remained below 1, the standard threshold for health concern. The estimated daily intake from drinking bottled water fell below established reference values for most chemicals. The exceptions were two phthalates, DnBP and DEHP, where the most highly exposed individuals exceeded WHO recommendations by small margins (around 1.5% to 5.8% of the reference dose). The takeaway: proper storage keeps risk low, but leaving bottles in heat meaningfully increases your exposure.
Microplastics and Nanoplastics
Beyond chemical leaching, bottled water contains physical fragments of plastic. Research published through the National Institutes of Health found that a typical liter of bottled water contains roughly 240,000 tiny plastic particles. About 90% of those are nanoplastics, fragments smaller than one micrometer, small enough to potentially cross cell membranes. These particles come from the bottle itself, the cap, and the bottling process. The long-term health effects of ingesting nanoplastics are still being studied, but the sheer volume detected in bottled water is significantly higher than what’s found in tap water.
PFAS (Forever Chemicals)
PFAS are synthetic chemicals that resist breaking down in the environment or the body, earning them the nickname “forever chemicals.” The FDA tested 197 bottled water samples collected from U.S. retail locations between 2023 and 2024, screening for 18 types of PFAS. Ten of the 197 samples had detectable levels. None exceeded the maximum contaminant levels the EPA has set for public drinking water.
Among the positive samples, domestic brands (purified and spring water) contained between one and four different PFAS compounds per sample. Imported artesian waters showed one to two. Four of the detected PFAS types had established EPA limits and fell below them. Two others don’t yet have federal limits at all. The results suggest PFAS contamination in bottled water exists but is not widespread and currently remains at low concentrations.
Heavy Metals and Arsenic
Bottled water can contain trace levels of naturally occurring metals picked up from the source water or from processing equipment. The FDA sets a limit of 10 micrograms per liter (10 parts per billion) for arsenic in bottled water, matching the EPA standard for tap water. Lead, cadmium, and other metals are also regulated, though at different thresholds.
These metals enter water primarily from the geological formations the source water passes through. Spring and mineral waters, which are less heavily processed than purified water, are more likely to contain measurable mineral and metal content. For most brands, levels fall well below regulatory limits, but the FDA does not require companies to print specific contaminant levels on the label.
Fluoride
Some bottled water contains fluoride, either naturally present in the source or deliberately added. If fluoride is added, the FDA requires it to appear in the ingredient list on the label. Naturally occurring fluoride does not require the same disclosure, so the absence of fluoride on a label doesn’t guarantee the water is fluoride-free. If avoiding or seeking fluoride matters to you, look for brands that specifically state “fluoride added” or “no added fluoride” and check for water quality reports, which some companies publish online.
How Bottled Water Compares to Tap Water
The FDA regulates bottled water as a packaged food product. The EPA regulates municipal tap water. By design, the FDA sets its chemical limits to be “comparable” to EPA standards, so on paper, the two are held to similar thresholds for contaminants like bromate, arsenic, and disinfection byproducts.
The practical differences come down to two things. First, tap water suppliers are required to publish annual water quality reports listing every detected contaminant. Bottled water companies face no equivalent public disclosure requirement, making it harder to know exactly what’s in a specific brand. Second, bottled water introduces a contamination source tap water doesn’t have: the plastic container. The microplastics, phthalates, BPA, and antimony discussed above are largely unique to bottled water and directly tied to packaging and storage conditions. If you do drink bottled water regularly, storing it in a cool place and avoiding bottles that have been sitting in heat are the simplest ways to minimize chemical exposure from the plastic itself.