While public water supplies in the U.S. are generally safe, concern exists that some populations are more sensitive to certain contaminants. In fact, many websites for public water supplies contain a warning for individuals with compromised immune systems. This can include those undergoing chemotherapy for cancer, individuals with organ transplants or those who have been infected with HIV. Many medications may affect the immune system, which can make normal, healthy adults at risk should a water system fail. Also, pregnant women and newborn children may be more at risk when certain contaminants are present.
As we age, our immune systems change by becoming slower to act, making it easier for the elderly to become ill. Finally, some individuals have developed "multiple chemical sensitivity," in which they can be especially sensitive to certain chemicals.
Clearly, some diseases commonly affect the immune system, such as HIV, but many others should be considered, including rheumatoid arthritis, lupus, ulcerative colitis, Crohn’s disease, Type 1 diabetes, psoriasis and multiple sclerosis. Several of the medications used to treat many of these conditions affect the body’s immune system. Organ transplant recipients take immune-suppressing drugs to help prevent new organ rejection. The biggest side effect of taking an immune-suppressing drug is the risk of infection, so ensuring that drinking water is microbiologically safe is important. A bacterium or virus that can cause illness in the general population may cause those on medications that affect the immune system to be at higher risks for death. The U.S. Environmental Protection Agency (EPA) and the Centers for Disease Control and Prevention (CDC) have recommendations for further treatment of drinking water for Cryptosporidium. Recommendations include boiling water, microfiltration, ultrafiltration and reverse osmosis (RO).
Health risks for pregnant women
Pregnant women are also at a higher risk when exposed to certain contaminants in drinking water. Several studies suggest women who drink water containing trihalomethanes (THMs) have an increased risk of miscarriages. THMs are byproducts of chlorine disinfection, so they are very common in municipally supplied water. They are not as common in well water unless it has been treated with chlorine. They can easily be removed from drinking water using a simple carbon filter. Those who opt to use a carbon filter must ensure that it is changed on a regular basis. As carbon filters absorb THMs, they are filled up; and when a filter is full, it will not remove any THMs and, in fact, may start releasing THMs that are attached to the carbon, resulting in even higher levels of THMs in the water.
Other contaminants studied for adverse effects on pregnant women include arsenic, nitrates and lead. Studies suggest that these contaminants may have impacts on pregnant women, including miscarriages, birth defects and premature births. Emerging contaminants of concern, such as perfluorinated compounds (PFCs), have also been studied. Specifically, perfluorooctanoic acid (PFOA) was examined because of a class action legal settlement in an area in which PFOA contaminated drinking water supplies. The scientific panel assigned to perform the study announced a probable link of PFOA exposure and pregnancy-induced hypertension. Pregnancy-induced hypertension can lead to complications including premature birth and stillbirths, but further study is needed to determine what role PFOA plays.
Health risks for newborns and infants
In addition to pregnant women, newborns and infants can be at greater risk because of contaminants in drinking water. The standards for drinking water established by EPA under the Safe Drinking Water Act (SDWA) are based on average adult consumption, so infants can be at a higher risk even if the water meets EPA’s requirements. Infants drink more than two times as much water as adults in proportion to their body weight. This means that an infant on formula drinks about 1/7 of its weight in water — this would be the equivalent of an adult drinking almost three gallons of water. In short, an infant fed formula made with tap water could potentially be exposed to a lifetime level of contaminants within the first couple years of life.
Probably the most common water contaminant associated with newborns and infants is nitrate. Nitrate is associated with methemoglobinemia, commonly called "blue baby syndrome." Nitrate levels above the EPA’s MCL of 10 mg/l. When nitrate is ingested, it can be converted to nitrite, which oxidizes the iron in hemoglobin. This results in the formation of methemoglobin. Methemoglobin does not have the ability to carry oxygen as hemoglobin does, and this results in oxygen deprivation, which can cause the bluish coloring around the mouth, hands and feet of an infant. Nitrate is a common contaminant in well water, so testing is important to determine the levels present. Other contaminants — including arsenic, uranium, lead and pesticides — should also be considered when testing well water, especially if the water is to be used for preparing formula.
Health risks for the elderly
The elderly are another group that can be at risk for illness caused by water quality problems. As we age, our bodies change, making us more susceptible to both biological and chemical contamination that may be present in our drinking water. As we grow older, our immune system begins to decline and chronic diseases are more common, meaning more medications being prescribed, which can further weaken the immune system.
The elderly are at higher risk for microbiological contamination including bacteria, viruses and parasites that can be found in some water supplies. With weakened immune systems, the elderly population cannot easily fight infection, so when parasites such as Cryptosporidium or Giardia make it into the water supply, the results could be devastating.
Additionally, aging can also lead to hypochlorhydria, a condition that results in low stomach acid. Lower production of stomach acid results in a higher pH in the stomach, which can cause lower defenses against enteric pathogens like salmonella. One of the major symptoms of microbiological contamination, diarrhea, can be disastrous for the elderly, resulting in hospitalization or even death. While little study on the effects of chemical contaminants on the elderly has been conducted, speculation indicates that some impacts because of physiologic changes can occur when we age. This includes changes in absorption, metabolism and excretion, which can affect the way a person reacts to chemical exposures.
While most public water supplies provide safe water for the general populations, some incidents can occur within the distribution system, such as a water main break or household plumbing containing lead that is out of their control.
When discussing water treatment, educating people about the potential health risks for these sensitive populations is important. Keep in mind, they may not know they could be extra sensitive to contaminants, so take the time to ask questions about health and medications. Water treatment can make the difference between life and death for these populations.