Fact Sheet - How safe is my drinking water?

Most community water suppliers deliver high quality drinking water to the population of Lithuania every day. Nationwide, drinking water systems have spent millions of litas to build drinking water treatment and distribution systems, and they spend an additional money each year to operate and maintain them.

In addition, there is a network of government agencies whose job is to ensure that public water supplies are safe. Nonetheless, problems with local drinking water can, and do, occur.

All sources of drinking water contain some naturally occurring contaminants. Because water is the universal solvent, many materials are easily dissolved upon contact. At low levels, these contaminants generally are not harmful in our drinking water. Removing all contaminants would be extremely expensive and in nearly all cases would not provide greater protection of health. A few of the naturally occurring substances may actually improve the taste of drinking water and may have nutritional values at low levels.

As development in our modern society increases, there are growing numbers of threats that could contaminate drinking water. Suburban sprawl has encroached upon once pristine watersheds, bringing with it all of the by-products of our modern life style. Actual events of serious drinking water contamination occur infrequently, and typically not at levels posing immediate health concerns. Nonetheless, with the threats of such events increasing, we cannot take drinking water safety for granted. Greater vigilance by you, your water supplier, and your government is vital to ensure that such events do not occur in your water supply.

Microbiological and chemical contaminants can enter water supplies. These materials can be the result of human activity or can be found in nature. For instance, chemicals can migrate from disposal sites and contaminate sources of drinking water. Animal wastes and pesticides may be carried to lakes and streams by rainfall runoff or snow melt. Human wastes may be discharged to receiving waters that ultimately flow to water bodies used for drinking water. Coliform bacteria from human and animal wastes may be found in drinking water if the water is not properly treated or disinfected. These bacteria are used as indicators that other harmful organisms may be in the water.

The potential for health problems from drinking water is illustrated by localized outbreaks of water-borne disease. Many of these outbreaks have been linked to contamination by bacteria or viruses, probably from human or animal waste.

Certain pathogens, such as Cryptosporidium, may pass through water treatment filtration and disinfection processes in sufficient numbers to cause health problems. Cryptosporidium is a protozoa that causes the gastrointestinal disease cryptosporidiosis. The most serious, and sometimes deadly, consequences of cryptosporidiosis tend to be focused among sensitive members of the population, such as individuals with immune system deficiencies.

Nitrate in drinking water at levels above the national standard poses an immediate threat to young children. Excessive levels can result in a condition known as "blue baby syndrome." If untreated, the condition could be fatal.

Boiling water contaminated with nitrate increases the nitrate concentration and the potential risk. Persons worried about nitrate should talk with their doctor about alternatives to using boiled water in baby formula.

Naturally occurring contaminants also are being found in drinking water. For example, the radioactive gas radon-222 occurs in certain types of rock and can get into ground water. People can be exposed to radon in water by drinking it, while showering, or when washing dishes. The primary source of exposure to radon in the home is radon seeping out of the soil and into the basement air.

Information on water quality in your area is available from several sources, including your local public health department and your water supplier. You can determine whom to contact by checking your water bill or by calling your local town hall.

State agencies also can provide extensive information on your water supply and its quality. Each region has a department responsible for drinking water quality.

A process called risk assessment is used to set drinking water quality standards. When assessing the cancer and non-cancer risks from exposure to a chemical in drinking water, the first step is to measure how much of the chemical could be in the water. Next, scientists estimate how much of the chemical the average person is likely to drink. This amount is called the exposure. In developing drinking water standards, countries often assume that the average adult drinks 2 liters of water each day throughout a 70-year life span.

Risks are often estimated separately for cancer and non-cancer effects. For cancer effects, a risk assessment estimates a measure of the chances that someone may get cancer because they have been exposed to a drinking water contaminant. Some countries generally set Maximum Contaminant Levels that will limit an individuals risk of cancer from that contaminant to between 1 in 10,000 and 1 in 1,000,000 over a lifetime. For non-cancer effects, the risk assessment estimates an exposure level below which no adverse effects are expected to occur.

Maximum Contaminant Levels are set based on known or anticipated adverse human health effects, the ability of various technologies to remove the contaminant, their effectiveness, and cost of treatment. All Maximum Contaminant Levels are set at levels that protect public health. The limit for many substances is based on lifetime exposure so, for most potential contaminants, short-term exceed-ances pose a limited health risk. The exceptions are the standards for coliform bacteria and nitrate, for which exceedances can pose an immediate threat to health.

To comply with Maximum Contaminant Levels, public water systems may use any state-approved treatment. When it is not economically or technologically feasible to set an Maximum Contaminant Level for a contaminant--for example, when the contaminant cannot be easily measured-- the use of a particular treatment technique may be required instead. The technique specifies the design for part of the drinking water treatment process.

Local governments, public water systems, the regions, and the national government work together towards the goal of ensuring that all public water supplies are safe. For households on private wells, state and local health departments usually have some standards for the drinking water, but it is generally up to the homeowner to maintain the quality of the drinking water.

Local governments have a direct interest in protecting the quality of their drinking water source, be it ground water or surface water. They may be responsible for overseeing land uses that can affect the quality of untreated source water. Public water systems have a responsibility to maintain sound treatment works and water distribution networks. They are responsible for ensuring that the water they supply does not contain contaminants at levels higher than the law allows.

When a state water agency or water supplier announces that the standard for a particular contaminant has been exceeded, that may or may not by itself be a cause for alarm, but it can be a cause for action. It is a safety precaution required by the law to alert the public to deficiencies in drinking water quality.

Boil Water Notices

When microorganisms such as those that indicate fecal contamination are found in drinking water, water suppliers may be required to issue "boil water notices." Boiling water kills the organisms that can cause disease. Therefore, the notices serve as a precaution for the public.

2. How Safe Is My Drinking Water?