Understanding Nitrates in Water
Nitrate (NO3) is a compound made of nitrogen and oxygen that occurs naturally in the nitrogen cycle. It is essential for plant growth, but human activities have increased its concentration in many water sources. High levels are often due to agricultural runoff from fertilizers and manure, animal feedlots, septic systems, and wastewater. Because nitrates move easily in soil, they can leach into groundwater, a common source for both municipal tap water and some bottled water.
How Bottled Water Sources Affect Nitrate Levels
The amount of nitrates in bottled water directly depends on its origin. Several categories of bottled water exist, each with a different potential for nitrate content:
- Spring water: This water comes from an underground formation from which water flows naturally to the surface. Since spring water comes from groundwater, its nitrate levels can vary based on local agricultural practices and other sources of contamination. Some studies have found significant nitrate levels in spring waters.
- Purified water: This water is sourced from a municipal supply or another source but is then treated with processes such as reverse osmosis, distillation, or deionization to remove most dissolved solids, including nitrates. Purified water typically has very low or undetectable levels of nitrates.
- Mineral water: This water originates from a protected underground source and contains a constant proportion of minerals and other trace elements. The water is bottled directly at the source, and no minerals can be added or removed. Nitrate content is determined by the geology and purity of the specific underground aquifer. Studies show a wide range of nitrate levels in different mineral water brands.
- Drinking water: This is a broad category, and the water can come from various sources. It is often simply bottled tap water that has undergone some form of treatment, but it is not required to be as pure as 'purified' water. Its nitrate levels will be dependent on the source and treatment.
Health Implications of Nitrate Consumption
While nitrates are generally not harmful to healthy adults, the main health concern is methemoglobinemia, or "blue baby syndrome," which affects infants under six months of age. In an infant's stomach, nitrates can be converted to nitrites, which interfere with the blood's ability to carry oxygen. This can cause the baby's skin to turn bluish and, in severe cases, can be fatal.
Besides infants, research suggests potential health impacts from long-term exposure to nitrates at levels below the EPA standard, including associations with thyroid problems, adverse pregnancy outcomes, and certain cancers. For example, a study in Spain found a link between long-term ingestion of waterborne nitrate and prostate cancer risk.
Comparing Nitrate Levels in Different Water Types
The following table compares the typical range of nitrate levels found in different types of water. It's important to note that specific values can vary based on regional factors and the exact source.
| Water Type | Typical Nitrate Range (mg/L NO3) | EPA Standard (mg/L NO3-N, 10 mg/L) | Comments |
|---|---|---|---|
| Tap Water | Varies widely (often below 3 mg/L, but can exceed 10 mg/L) | Yes | Levels are tested and regulated by the municipality, but can fluctuate based on source water quality. |
| Spring Water | Varies widely (some studies show median levels from <1 to >5 mg/L) | Yes | Depends on the protection and location of the specific spring source. |
| Purified Water | Often non-detectable or very low (<1 mg/L) | Yes | Reverse osmosis and distillation effectively remove nitrates during the purification process. |
| Mineral Water | Varies widely (studies show ranges from <1 to over 10 mg/L) | Yes | The natural mineral and nitrate content is specific to the source aquifer. |
| Well Water | Varies widely (high risk if near agricultural areas) | No (Private wells) | Not under EPA jurisdiction, making regular testing crucial for well owners. |
How to Minimize Nitrate Exposure from Bottled Water
For consumers concerned about nitrates, especially those preparing formula for infants, several steps can be taken:
- Read the label carefully. Although not always required, some bottled water companies provide information about their water quality. Check for terms like "purified" or "distilled," which indicate lower nitrate levels.
- Choose purified or distilled brands. These types of bottled water undergo intensive treatment that effectively removes nitrates, providing the safest option for infants and other vulnerable individuals. Boiling water is not an effective method and will actually increase nitrate concentration as the water evaporates.
- Check for water quality reports. Reputable brands may make their water quality reports publicly available on their websites. This provides transparency on nitrate levels and other contaminants.
- Consider your local tap water. For healthy adults and children over six months, the local tap water might be perfectly safe and have low nitrate levels, especially if it comes from a well-managed public water system. You can obtain a Consumer Confidence Report (CCR) from your public water utility to see testing results.
- Use a home water filter. Certain home water filtration systems, such as reverse osmosis, can also effectively remove nitrates from tap water for a more controlled supply.
Conclusion
Bottled water often contains nitrates, with levels determined by its source and treatment. Regulators limit nitrate levels to a maximum of 10 mg/L to prevent infant methemoglobinemia. Consumers concerned about nitrate exposure, especially for infants, can significantly reduce risk by selecting purified or distilled bottled water. The long-term health effects of low-level nitrate exposure are still being studied, underscoring the importance of informed consumer choices and understanding your drinking water source.
For more details on nitrate guidelines and public health, visit the U.S. Environmental Protection Agency's official website at https://www.epa.gov.
Frequently Asked Questions
Does all bottled water contain nitrates?
No, not all bottled water contains nitrates. The presence of nitrates depends on the water's source and treatment method. Purified or distilled water typically has had nitrates removed, while spring and mineral water may contain them naturally.
What is a dangerous level of nitrates in drinking water?
For infants under six months, a level above the 10 mg/L (as nitrate-nitrogen) regulatory standard is considered dangerous due to the risk of blue baby syndrome. The World Health Organization also uses this level as a guideline, though some research suggests potential risks for adults at lower, long-term exposures.
How do nitrates get into water sources?
Nitrates primarily enter water sources from human activities, including runoff from agricultural fertilizers and animal manure, septic systems, and wastewater. Natural decay of plant matter can also contribute.
Is bottled water with nitrates safe for adults?
Generally, moderate levels of nitrates in bottled water are not considered a significant health risk for healthy adults. However, long-term exposure and consumption of high levels may be linked to other health concerns.
Can nitrates be removed from water at home?
Yes, some home water treatment systems can remove nitrates. Reverse osmosis, distillation, and ion exchange units are effective methods for removing nitrates from tap water.
Why is boiling water bad for removing nitrates?
Boiling water is ineffective for removing nitrates because nitrates do not evaporate. Instead, as the water boils and turns to steam, the concentration of nitrates in the remaining water increases.
Which type of bottled water is best for babies?
For infants, purified or distilled bottled water is the safest option for preparing formula, as these types have undergone treatment to remove contaminants like nitrates. Health authorities recommend avoiding bottled water from unknown sources or with potentially high nitrate content.
