Before Hurricane Katrina hit, I saw a graphic on one of the cable news channels describing emergency water options. One of the recommendations was the boiling of water. To my great surprise, the graphic showed in parenthesis "except for pregnant women and small children."

This info must to be wrong, right? Why would boiled (and obviously cooled later) water be detrimental to the health of pregnant women and small children?

Hopefully the medical professionals here could dispell or confirm this potentially dangerous advice.

From the North Carolina Department of Health and Human Services:

"Boiling water can concentrate potential nitrate contamination. Although most adults are not generally affected by nitrate contamination, young infants and pregnant women are and should not be given boiled water."

From Nebraska Cooperative Extension G96-1279-A:

"Nitrogen is essential for all living things as it is an essential component of protein. Nitrogen exists in the environment in many forms and changes forms as it moves through the nitrogen cycle. However, excessive concentrations of nitrate-nitrogen in drinking water can be hazardous to health, especially for infants and pregnant women.

The primary health hazard from drinking water with nitrate-nitrogen occurs when bacteria in the digestive system transforms nitrate to nitrite. The nitrite oxidizes iron in the hemoglobin of red blood cells to form methemoglobin, which lacks the oxygen-carrying ability of hemoglobin. This creates the condition known as methemoglobinemia (sometimes referred to as "blue baby syndrome"), in which blood lacks the ability to carry sufficient oxygen to the individual body cells.

Most humans over one year of age have the ability to rapidly convert methemoglobin back to oxyhemoglobin; hence, the total amount of methemoglobin within red blood cells remains low in spite of relatively high levels of nitrate/nitrite uptake. However, in infants under six months of age, the digestive system has an underdeveloped capability to secrete gastric acid, thus the pH level in the digestive system may rise. At a higher pH, bacteria levels may rise, increasing the transformation of nitrate to nitrites. In addition, the enzyme systems for reducing methemoglobin to oxyhemoglobin are incompletely developed in infants under six months of age. Thus, methemoglobinemia can occur. Older persons who have a gastrointestinal system disorder producing a pH level which allows for increased bacteria growth may be at greater risk than the general population. In addition, individuals who have a genetically impaired enzyme system for metabolizing methemoglobin are at greater risk.

In addition, because of some reports of potential birth defects when pregnant women drank high nitrate water, pregnant women should not drink water containing more than 10 mg/L NO3-N. It also is recommended that nursing mothers use water that has an NO3-N concentration below 10 mg/L since nitrate may be passed to infants in breast milk.

Merely boiling water will increase rather than decrease the nitrate concentration. Carbon adsorption filters, mechanical filters of various types, and standard water softeners do not remove nitrate-nitrogen."

Personally, I'd give my pregnant wife and kids boiled water before I let them die of dehydration.

A good reason to have other disinfection methods available --bleach, filter, etc.