Which statement about boiling water and nitrates is true?

Boiling water is primarily known for its ability to kill harmful bacteria and other pathogens, which makes it a common practice for ensuring water safety in terms of microbial contamination. However, when it comes to nitrates, boiling is not effective as the process does not remove or reduce nitrate levels in water. Instead, boiling water actually concentrates nitrates because the water evaporates, leaving the nitrates behind.

Therefore, stating that boiling water decreases overall water quantity is somewhat misleading. While boiling will reduce the volume of water due to evaporation, it does not tackle the issue of nitrates directly, making popping this particular statement misleading in context of water treatment.

The correct perspective is that boiling water indeed kills harmful bacteria making the water safer to consume from a microbiological standpoint, but it is not a treatment method for removing nitrates or improving the safety for that particular contaminant. Other methods such as ion exchange, reverse osmosis, or specific filtration systems would be required to effectively treat water with high nitrate levels.