||A specified concentration of a contaminant in water. If this concentration is reached or exceeded,
certain actions (e.g., further treatment and monitoring) must be taken to comply with a drinking water regulation.
||See etiologic agent.
||A geologic formation or part of a formation (e.g., gravel, sand, or porous stone) that yields water to wells
||A hydraulic condition caused by a difference in water pressure that causes nonpotable water or other liquid
to enter the potable water system by either backpressure or backsiphonage. See cross-connection.
||A hydraulic condition that results when pressure from a customer's water system (e.g., potentially nonpotable water) is higher than pressure in the public water system, resulting in backflow of water into the public water system.
||A hydraulic condition caused by negative or subatmospheric pressure within a water system, resulting
||Microbial cells that adhere to a surface through a matrix of primarily polysaccharide materials in which
they are encapsulated. Biofilms can grow on piping and surfaces of water systems and can be difficult to remove. They
offer protection to microbes from disinfectants (e.g., chlorine) in the water.
||A statement to the public advising that tap water must be boiled before drinking.
||Commercially produced bottled water.
||A categorization given to waterborne disease and outbreaks (WBDOs) indicating to the strength of the
epidemiologic and water-quality data implicating water as the source of the disease or outbreak (see Table 3).
||All aerobic and facultative anaerobic, gram-negative, nonspore-forming, rod-shaped bacteria that
ferment lactose with gas formation within 48 hours at 95°F (35°C). Coliforms are mostly harmless bacteria that live in soil and
water as well as the gut of humans and animals.
|community water system
||A public water system that has at least 15 service connections used by year-round
residents or that regularly serves at least 25-year-round residents. The system might be owned by a private or public entity
providing water to a community, subdivision, or mobile home park.
||Any actual or potential connection between a drinking water supply and a possible source
of contamination or pollution (i.e., nonpotable water). Under this condition, contaminated water might flow back into
the drinking water system. See backflow.
||An antecedent event or situation contributing to the occurrence of a waterborne disease or outbreak.
||Inflammation of the skin. In this report, the term dermatitis is used to denote a broad category of
skin-related symptoms (e.g., folliculitis, cellulitis, chemical burns, or rash).
||A treatment that kills microorganisms (e.g., bacteria, viruses, and protozoa); in water treatment, a
chemical (commonly chlorine, chloramine, or ozone) or physical process (e.g., ultraviolet light) may be used.
||Chemicals formed in water by the reaction between organic matter and other waste
products and disinfectants.
|| Water pipes, storage reservoirs, tanks, and other means used to deliver drinking water to
consumers or to store finished water before delivery to a customer. In community water systems, the distribution system is under
the jurisdiction of a water utility and ends at the water meter or at the customer's property line (if the system is not metered).
In noncommunity and nonpublic individual water systems, the distribution system ends at the point where water enters
the building or house. See plumbing.
||The pathogen, chemical, or toxin causing a waterborne disease or outbreak. Infectious etiologic agents
are bacteria, parasites, viruses, or fungi.
||Coliform bacteria that grow and ferment lactose to produce gas at 112.1°F (44.5°C) in <24 hours.
These bacteria are associated with human and animal wastes, and their presence in water might be an indication of recent sewage
or animal waste contamination.
||In water treatment, the process of passing water through one or more permeable membranes or media
of small diameter (e.g., sand, anthracite, and diatomaceous earth) to remove suspended particles from the water. Filters might
be effective in removing pathogens, depending on the type and operation.
||The water (e.g., drinking water) delivered to the distribution system after treatment, if any.
||The chlorine in water that is not combined with other constituents, therefore, serving as an
effective disinfectant (also referred to as free available chlorine and residual chlorine).
||Water that is contained in interconnected pores in an aquifer.
|ground water system
||A system that uses water extracted from an aquifer (i.e., a well or spring) as its source.
|ground water under the direct influence of
||As defined by the U.S. Environmental Protection Agency (EPA), any water beneath the surface of the ground
with substantial occurrence of insects or other macrooganisms, algae, or large-diameter pathogens (e.g.,
Giardia intestinalis or
Cryptosporidium), or substantial and relatively rapid shifts in water characteristics (e.g., turbidity, temperature, conductivity,
or pH) that closely correlate with climatologic or surface water conditions. Direct influence must be determined for
individual sources in accordance with criteria established by the state.
|individual water system
||A water system that does not meet the EPA definition for a public water system. The
system might serve a single family or farm not having access to a public water system, or it might regularly serve as many as
24 persons or 14 connections. States are responsible for regulating these water systems.
||An aquifer characterized by water-soluble limestone and similar rocks in which fractures or cracks have
been widened by the dissolution of the carbonate rocks by ground water; the aquifer might contain sinkholes, tunnels, or
|maximum contaminant level
||The maximum permissible concentration (i.e., level) of a contaminant in water supplied
to any user of a public water system.
||More than one type of etiologic agent is identified in clinical specimens from affected persons,
and each etiologic agent is found in more than 5% of positive clinical specimens (e.g., an outbreak with
Giardia spp. [parasites] and
Salmonella spp. [bacteria] with each agent identified in >5% of stool specimens).
||More than one type of illness is reported by more than 50% of patients in a single outbreak (e.g.,
a combination of gastroenteritis and dermatitis).
||More than one type of source water is implicated in the outbreak (e.g., a combination of
ground water and surface water).
||More than one type of water system is implicated in the outbreak (e.g., a combination
of noncommunity and individual water systems).
|noncommunity water system
||A public water system that is not a community system; it does not serve
year-round residents. There are two types: transient and nontransient noncommunity systems.
|nontransient noncommunity water system
||A public water system that is not a community system and that regularly serves at least 25 of the same persons
for more than 6 months per year but not year-round (e.g., a school, a factory, or a business with its own water supply).
||Water pipes, storage reservoirs, tanks, and other means used to deliver drinking water to consumers
inside buildings or houses or to store drinking water inside buildings or houses before consumption. In community water
systems, the plumbing begins after the water utility's water meter or at the property line (if the distribution system is not metered).
In noncommunity and nonpublic individual water systems, the plumbing begins at the point where water enters the building
or house. See distribution system.
||The category of illness reported by at least 50% of ill respondents (e.g., gastroenteritis, dermatitis,
or acute respiratory illness). When more than one illness category is reported for a single WBDO, they are listed together
as predominant illnesses. These mixed illness WBDOs are analyzed separately from WBDOs with single illnesses.
|primary water exposure
||For use in this report, a classification used for the source of contaminated water not
intended for drinking or contaminated water of unknown intent.
|public water system
||A system, classified as either a community water system or a noncommunity water system,
that provides piped water to the public for human consumption and is regulated under the Safe Drinking Water Act. Such
a system must have at least 15 service connections or regularly serve at least 25 persons daily for at least 60 days per year.
||Surface water or ground water that has not been treated in any way.
||An artificially maintained lake, created for the collection and storage of water. This body
of water can be available as a source of raw water for drinking purposes and/or recreational use. In certain instances, a
finished water storage facility in the distribution system might also be called a reservoir.
||Location where exposure to contaminated water occurred (e.g., restaurant, water park, or hotel).
||Untreated water (i.e., raw water) used to produce drinking water.
||All water on the surface (e.g., lakes, rivers, reservoirs, ponds, and oceans) as distinguished from subsurface
or ground water.
||Fecal and nonfecal coliforms that are detected by using a standard test. The extent to which total
coliforms are present in water can indicate the general quality of that water and the likelihood that the water is fecally contaminated
by animal and/or human sources.
|transient noncommunity water system
||A public water system that is not a community system and that does not regularly serve at least 25 of the same persons
for more than 6 months per year. These systems provide water to places where persons do not remain for long periods
(e.g., restaurants, campgrounds, highway rest stations, or parks with their own public water systems).
||Surface water or ground water that has not been treated in any way (i.e., raw water).
|water not intended for drinking
||Water that has not been treated for human consumption in conformance with
EPA drinking water standards and that is provided for uses other than for drinking. This might include water used in
occupational settings; lakes, springs, and creeks used as drinking water by campers and boaters; irrigation water; and other nonpotable
water sources with or without taps but does not include exposure to recreational water or flood water.
|water of unknown intent
||The information about the water is insufficient to determine for what purpose it is
being provided or used and whether is has been treated for human consumption in conformance with EPA drinking water standards.
||A system for the provision of water for human consumption through pipes or other constructed
conduits. This includes any collection, treatment, storage, and distribution facilities used primarily in connection with such a system.