Chapter 2. Health and Aesthetic Aspects of Drinking Water

2.2



CHAPTER two



Arsenic.............................................. 2.34

Asbestos........................................... 2.35

.

Boron. ............................................... 2.35

.

Cadmium.......................................... 2.36

.

Chromium......................................... 2.36

Copper. ............................................. 2.37

.

Fluoride............................................. 2.38

Hardness........................................... 2.38

Iron.................................................... 2.39

Lead................................................... 2.39

Manganese....................................... 2.40

Mercury............................................. 2.40

Nitrate and Nitrite............................ 2.41

.

Perchlorate........................................ 2.42

Selenium........................................... 2.43

Sodium.............................................. 2.43

Sulfate............................................... 2.44

ORGANIC CONSTITUENTS................ 2.44

.

Volatile Organic Chemicals. ............ 2.45

.

Pesticides.......................................... 2.50

Herbicides.......................................... 2.52

Insecticides....................................... 2.54

Fungicides......................................... 2.56

Additional and Emerging

Drinking Water Contaminants....... 2.56

.

Chemicals in Treatment Additives,

Linings, and Coatings.................... 2.58

.

DISINFECTANTS AND

DISINFECTION BY-PRODUCTS......... 2.59



General Background........................

Health Basis for DBP Regulation.....

Approaches for Evaluation of

Health Effects of DBPs. ..................

.

Disinfectants and Inorganic DBPs....

.

Organic Disinfection By-products.....

RADIONUCLIDES.................................

Introduction......................................

Health Effects of Radionuclides......

.

General Considerations for

Drinking Water Standards for

Radionuclides.................................

Specific Radionuclides as

Drinking Water Contaminants.......

.

AESTHETIC QUALITY..........................

Taste and Odor.................................

Turbidity and Color..........................

Mineralization...................................

Hardness...........................................

Staining.............................................

PREPAREDNESS AND HEALTH..........

FINAL COMMENT................................

INTERNET RESOURCES. ....................

.

ABBREVIATIONS.................................

ACKNOWLEDGMENTS.......................

REFERENCES.......................................



2.59

2.60

2.60

2.64

2.66

2.69

2.69

2.70



2.71

2.71

2.72

2.73

2.74

2.75

2.75

2.75

2.75

2.76

2.76

2.77

2.78

2.79



Microbiological and chemical contaminants in drinking water may cause acute or chronic health

effects or undesirable aesthetic properties when present at excessive concentrations. Hence,

health and aesthetic concerns are the principal motivations for water treatment. This chapter

summarizes the approaches used to develop the health and aesthetic basis for drinking water

standards and guidance, and the health and aesthetic effects of the major groups of contaminants

found in drinking water. Following an introductory discussion of waterborne disease outbreaks,

specific pathogenic organisms and indicator organisms are discussed. For chemical contaminants, basic concepts of toxicology and risk assessment for chemical and microbial contaminants

are presented, followed by separate sections on inorganic constituents, organic compounds, disinfectants and disinfection by-products (DBPs), and radionuclides. Emphasis is placed on contaminants that occur more frequently and at levels that are of concern for human health as well

as emerging contaminants of recent interest. Taste and odor, turbidity, color, mineralization, and

hardness are discussed in the final section, which is devoted to aesthetic quality.

Because of space considerations, citations have been limited to those most generally applicable, especially those from U.S. governmental organizations such as the U.S. Environmental

Protections Agency (USEPA) and the Centers for Disease Control and Prevention (CDC). A

general reference for toxicology is Klaasen (2007). For risk assessment, general references are

the USEPA risk assessment documents listed in the guidance section of the USEPA Integrated

Risk Information System (IRIS) Website. Useful sources of information on health effects,







HEALTH AND AESTHETIC ASPECTS OF DRINKING WATER



2.3



occurrence, and environmental fate and transport of specific contaminants include the National

Academy of Sciences series on drinking water, the Toxicological Profiles produced by the

Agency for Toxic Substances and Disease Registry (ATSDR) of the CDC, the USEPA IRIS

database, the World Health Organization (WHO) Guidelines for Water Quality, which will be

updated in 2010, and the National Library of Medicine’s Toxnet/Hazardous Substances Data

Bank (HSDB) and PubMed databases. The Internet websites for these resources are provided

at the end of this chapter.

As mentioned in Chap. 1, some states have established standards for some contaminants that are more stringent than the federal standards. More stringent standards may be

based on different interpretation of the health effects information, improved capabilities of

available analytical methods, or a more favorable cost-benefit analysis, reflecting the local

conditions. States may also establish standards or guidance for additional contaminants not

regulated on a national basis.

For chemicals, emphasis has been given to potential health effects from long-term exposure to concentrations that may occur in drinking water rather than to the effects of acute

poisoning by much higher concentrations. Where the effects are markedly different between

routes of exposure, effects from oral exposure rather than inhalation are emphasized. This

chapter is intended as an introductory overview of information on health effects and occurrence of drinking water contaminants. The cited references and public health officials should

be consulted when evaluating specific situations of contamination. This chapter does not

address acute poisoning situations. Effects of acute poisoning are addressed in other handbooks and Internet Websites. If such poisoning has occurred, local poison control authorities

should be consulted.



WATERBORNE DISEASE

From 1993 through 2006, the CDC reported 203 waterborne disease outbreaks in the United

States and its territories, with a total of 418,894 actual or estimated cases of illness (Table 2-1).

The responsible agent was not identified in 50 (25 percent) of these outbreaks, while microbes

caused 119 (59 percent) and chemicals caused 34 (17 percent) of the outbreaks. The data include

an estimated 403,000 illnesses from the 1993 Cryptosporidium disease outbreak in Milwaukee,

Wis., but this number has been questioned due to recall bias (Hunter and Syed, 2002). The data

also include 26 disease outbreaks (156 cases and 12 deaths) caused by Legionella following exposure to water intended for drinking for the period 2001 through 2006. Legionella data were not

available prior to 2001; thus the outbreak data are underrepresented in this regard. Much of the

disease burden involves gastrointestinal (GI) illness, but a variety of other, more serious illnesses

also occur (e.g., pneumonia, hepatitis). This reporting period was selected because 1993 was the

year when compliance with most provisions of the USEPA Surface Water Treatment Rule was

required (USEPA, 1989a). All provisions of the USEPA Total Coliform Rule (TCR) were in effect

at the start of 1991 (USEPA, 1989b). The last year for which data are available is 2006.

If outbreaks caused by a source other than a community or a noncommunity water

system (e.g., illnesses caused by contaminated bottled water or container, consuming

non-potable water, water from private systems, or water from systems serving fewer

than 15 residences) are excluded from the data, there were 144 outbreaks affecting

417,468 persons, including 23 outbreaks (16 percent) caused by chemicals affecting

281 persons. Excluding the caseload from the large 1993 Milwaukee Cryptosporidium

outbreak, the outbreaks due to Legionella, as well as the outbreaks in U.S. territories,

between 1993 and 2006 the number of disease outbreaks and cases of illness caused

by exposure to contaminated water linked to a community or non-community water

system in the United States was 122 and 14,324, respectively. This equates to a 14-year



2.4



CHAPTER two



Table 2-1  Agents Causing Waterborne Disease Outbreaks in the United States and Territories,

1993–2006a,b

Agent



Number of

outbreaks



Footnote Percent



Number of cases of illness



Unknown



50



25



2761



Bacteria

Legionella spp.c

E. coli O157:H7

Campylobacter spp.

Shigella spp.

Salmonella spp.

Vibrio cholerae

Mixed bacteria



63

26

11

9

5

4

2

6



31



3423

156

267

447

439

928

114

1072



Viruses

Norovirus

Hepatitis A



17

15

2



8



3636

3612

24



Parasites

Giardia intestinalis (G. lamblia)

Cryptosporidium parvum

Entamoeba histolytica

Naegleria fowleri

Mixed parasite

Mixed Microbe Groups



35

22

10

1

1

1

4



17



407001

1908

404728

59

2

304

1698



Chemicals

Copper

Nitrate/nitrite

Sodium hydroxide

Lead

Fluoride

Soap/cleaning product

Other chemical



34

11

6

4

3

2

2

6



i



203



 



Total



d,e-1



d

d

e-2

f



e-3

g

h



2

17



300

167

21

38

3

43

15

13



100



418819



a

An outbreak is defined as: (1) two or more persons experience a similar illness after consumption or use of

water intended for drinking, and (2) epidemiologic evidence implicates the water as a source of illness. A single case

of chemical poisoning constitutes an outbreak if a laboratory study indicates that the water has been contaminated

by the chemical.

b

Data are from Kramer et al. (1996), Levy et al. (1998), Barwick et al. (2000), Lee et al. (2002), Blackburn

et al. (2004), Liang et al. (2006), and Yoder et al. (2008).

c

Legionella data are from 2001–2006. Only includes illness data for water intended for drinking.

d

Legionella pneumophila (20), L. micdadei (1), Legionella spp. (5); Shigella sonnei (4) and Shigella flexneri (1);

Salmonella Typhimurium (3), S. Bareilly (1).

e

U.S. territories: 1 = one outbreak from the Virgin Islands; 2 = Mariana Islands (Saipan) and Marshall Islands;

3 = Palau.

f

1996: Plesiomonas shigelloides and Salmonella Hartford. 1999: E. coli O157:H7 and Campylobacter jejuni.

2000: C. jejuni, E. coli O157:H7, and E. coli O111. 2001: C. jejuni and Yersinia enterocolitica. 2003: C. jejuni and

Shigella spp. 2006: E. coli O157:H7, E. coli O145, and C. jejuni.

g

1994: Giardia intestinalis and Entamoeba histolytica.

h

2002: C. jejuni, Entamoeba spp., and Giardia spp. 2004a: C. jejuni, Campylobacter lari, Cryptosporidium spp.,

and Helicobacter canadensis. 2004b: C. jejuni, norovirus, and Giardia intestinalis. 2006: Norovirus (G1, G2) and

C. jejuni.

i

One outbreak each due to: ethylene glycol; bromate and disinfection by-products; ethyl benzene, toluene, and

xylene; gasoline by-products; chlorine; unknown chemical.







HEALTH AND AESTHETIC ASPECTS OF DRINKING WATER



2.5



average of 9 outbreaks and 1023 illnesses per year. Of the 63 (52 percent) outbreaks

(6193 cases) that had a community water system as the source, a review of the outbreak

details revealed that at least 26 (41 percent), likely more, were caused by events that

occurred after delivery of water to the customer. Although 63 percent of the 144 outbreaks involved public water systems (PWSs) using groundwater sources, 91 percent

of the PWSs in the United States use groundwater sources (www.epa.gov/safewater/

databases/pdfs/data_factoids_2008.pdf). Furthermore, although the USEPA Ground

Water Rule (GWR) treatment requirements did not become effective until December

2009 (USEPA, 2006b), many states have had treatment requirements in place for many

years for PWS using groundwater sources.

Disease outbreak reporting is voluntary, and cases must be diagnosed and characterized

as waterborne. As such, the number or outbreaks and cases are underrepresented in some

states, given their respective populations. The summer peak in outbreaks is explained by

the many outbreaks that occur at seasonal venues such as summer camps, fairs, and resorts

(Table 2-2). Harder to explain is the smaller number of outbreaks that occurred in winter

as opposed to the other seasons at year-round venues such as homes, communities, and

various facilities.

Table 2-2  U.S. Disease Outbreaks by Source Venue and Season,

1993–2006*

Season‡

Source venue



†



Year-round

Homes

Facilities

Total

Seasonal

Recreation

Winter recreation



Total



Winter



Spring



Summer



78

64

142



11

10

21



21

11

32



27

22

49



43

4



0

3



3 (May)

1 (Mar.)



36

0



Fall

19

21

40

4 (3 Sep.)

0



*Data are from Kramer et al. (1996), Levy et al. (1998), Barwick et al. (2000),

Lee et al. (2002), Blackburn et al. (2004), Liang et al. (2006), and Yoder et al. (2008).

Outbreaks due to contaminated containers (11), unknown season (2), or multiple

seasons (1) not included.

†

Homes = homes, apartments, condominiums, mobile home parks, communities. Facilities = restaurants (including golf course restaurants), hotels, inns, schools,

churches, offices, factories, stores, medical care centers, other. Recreation = camps,

fairs/fairgrounds, parks, sport camps/events/venues, resorts/resort areas (except winter resorts).

‡

Winter = Dec. to Feb.; spring = Mar. to May; summer = Jun. to Aug. fall = Sep. to Nov.



Disease outbreak data do not include sporadic or endemic cases of illness. For several

reasons, the number of reported outbreaks and illnesses is a small proportion of the total

waterborne disease burden in the United States. The amount of GI illness attributable to public drinking water systems in the United States each year has been estimated to be between

4 and 33 million cases (Colford et al., 2006; Messner et al., 2006). If disease endpoints other

than GI illness were included, even higher numbers of cases would result. It should also

be noted that a portion of the total population exposed to any disease-causing agent does

not become ill. People whose infections are asymptomatic may become “carriers,” capable

of spreading disease through the shedding of the infectious agent in their feces and other

excretions. This topic is discussed further under Microbial Risk Assessment in the section

on Risk Assessment of Drinking Water Contaminants.



2.6



CHAPTER two



PATHOGENIC ORGANISMS

Pathogenic organisms are microorganisms capable of causing disease after getting past

host barriers and defenses and multiplying within the host. A number of characteristics

and circumstances determine whether or not a microorganism is a pathogen or a harmless

or even beneficial member of a host’s microbial community (Falkow, 1997). For example,

uptake of a bacterial virus or “plasmid” carrying “virulence genes” can convert some

types of harmless bacteria into pathogens. Readers who desire information on waterborne

pathogens beyond what can be included in this chapter are encouraged to consult the

most recent edition of Waterborne Pathogens (AWWA, 2006), as well as other recent

reviews (e.g., Szewzyk et al., 2000; Leclerc, Schwartzbod, and Dei-Cas, 2002; Cotruvo

et al., 2004; Craun et al., 2006). Recent pathogen-specific reviews are cited throughout

this section.

The three categories of pathogenic microorganisms that can be transmitted by water are

bacteria, viruses, and protozoan parasites (Table 2-1). Disease agents in these categories

were responsible for 63 (31 percent), 17 (8 percent), and 35 (17 percent) of the disease outbreaks, respectively (multiple groups were involved in four outbreaks). Due to diagnostic

limitations, many of the outbreaks caused by an unknown agent are likely caused by a virus.

Although a variety of fungi have been identified in water (Hageskal et al., 2006), there are

no documented waterborne disease outbreaks due to fungi in the United States, and there

is little if any evidence of potential adverse health effects due to waterborne fungi. Many

fungi are pathogenic to humans, but exposure is mostly by airborne inhalation or direct

dermal contact. A fourth category, cyanobacteria (blue-green algae), is covered separately.

Cyanobacteria are not pathogens. However, excessive growth (blooms) in rivers, lakes, and

reservoirs can result in the release of taste- and odor-causing chemicals that can be difficult

and expensive to remove during treatment. Some types of cyanobacteria can also produce

toxic chemicals, which have harmed wild and domestic animals and, on rare occasions,

humans (Carmichael, 2001).

A term increasingly used is emerging pathogen or emerging infectious disease. The

CDC defines emerging diseases as those in which “the incidence in humans has increased

in the past two decades or threatens to increase in the near future” (www.cdc.gov/ncidod/

EID/about/background.htm). Emerging diseases include those resulting from: (1) a new

pathogen created as a result of a change or evolution of an existing organism; (2) a known

pathogen spreading to a new geographic area or population; (3) a previously unrecognized

pathogen, including those appearing in areas undergoing ecologic transformation; and (4)

previously controlled infections reemerging as a result of antimicrobial resistance or breakdowns in public health measures. Some of the pathogens discussed below are considered

to be emerging pathogens.

Every biological species except viruses bears a two-word italicized name in Latin.

The first word, always capitalized, is the genus (e.g., Escherichia). The second name

is the species name, not capitalized, and there is usually more than one species for any

given genus (e.g., Escherichia coli [E. coli], Escherichia hermannii, etc.). Species are further

differentiated as to the types of antigens (protein and carbohydrate molecules) on their

surface to which host immune systems respond (serotypes, e.g., E. coli O157:H7). For the

genus Salmonella, what appear to be species names are actually serotypes with the serotype capitalized (e.g., Salmonella enterica serotype Typhimurium or simply Salmonella

Typhimurium). Species can also be differentiated by genetic differences (“genotypes”),

their mode of action (e.g., enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli

(EHEC), etc.), or other characteristics.

In nature in general and in source waters and drinking water distribution systems

in particular, microbes exist primarily in “biofilms”: diverse communities of protozoa,







HEALTH AND AESTHETIC ASPECTS OF DRINKING WATER



2.7



bacteria (and their secretions), and viruses. Microbial interactions in this environment

are constant. For example, viruses (phage) infect bacteria, protozoans feed on bacteria

and each other, and bacteria compete with one another. Some bacteria have evolved

mechanisms to survive and multiply within protozoa, most notably, Legionella, but also

other bacterial pathogens (Harb, Gao, and Abu, 2000; Snelling et al., 2006a). Microbial

characteristics in this environment, such as survival and resistance to disinfection, can

be quite different than when grown in isolation (King et al., 1988; Eboigbodin, Seth,

and Biggs, 2008). For example, in the natural environment, the function of antibiotic

compounds is not to kill or inhibit the growth of other organisms (with some exceptions) but rather to serve as signaling molecules to communicate and interact with other

microbes (Mlot, 2009).



Bacteria

Bacteria are single-celled prokaryotic microorganisms, meaning that their cellular architecture is different from that of the eukaryotic cells of protozoa and animals or of the archaea,

which are bacteria-like microorganisms with their own unique architecture. A few types

such as Clostridium and Bacillus can develop into resting endospores that can withstand

extreme environmental stresses. Bacteria exist in a variety of shapes, but two common

shapes are spheres (cocci) and round-ended rods (bacilli). Typical sizes range from 0.5 to

8 mm, but smaller and larger sizes exist. Some bacteria exist in colonies as clumps, sheets,

or chains.

Bacteria reproduce by binary fission. Of the three main groups of pathogens, bacteria are the only group with members capable of growth (reproduction) outside of their

host. Many bacteria, including many clinically important pathogens, can be grown in the

laboratory. Bacteria occur in feces in high concentrations (e.g., 107 to 1011 per gram).

Some pathogens are aerobes requiring oxygen for growth, while others are anaerobes

that are killed in the presence of oxygen (but anaerobic Clostridia can form endospores

that remain viable in the presence of oxygen). Another group, facultative anaerobes, can

thrive in the presence or absence of oxygen. Of the many bacteria in nature, only a few

cause disease. Many bacterial infections can be treated with antibiotics. Because of the

extensive use of antibiotics in hospitals and farms over many years, a number of bacterial

pathogens have developed resistance to many antibiotics. Bacterial pathogens of current

interest are described below.

Enteric Bacteria.  Until the early 1900s, enteric bacteria were responsible for many

waterborne disease epidemics worldwide. Epidemics of typhoid fever (caused by

Salmonella Typhi), dysentery (Shigella dysenteriae), and cholera (Vibrio cholerae) were

not uncommon and resulted in considerable mortality. Following the advent of clean

water technologies (Cutler and Miller, 2005) and improvements in hygiene in the early

1900s, disease outbreaks due to these bacteria no longer occur in the United States, but

they continue to occur in countries with inadequate sanitation. Although self-limiting

gastrointestinal illness is the primary symptom in most cases of illness caused by enteric

bacteria, other types of illnesses occur, and some outbreaks have resulted in hospitalizations and mortality.

Enteric bacteria are members of the family Enterobacteriaceae. Members of this family are foodborne as well as waterborne pathogens that are able to infect exposed persons by the fecal-oral route. For waterborne outbreaks, this usually means drinking water

that is contaminated with human or animal feces from which these pathogens are derived.

Between 1993 and 2006, species of enteric bacteria in the genera Escherichia, Shigella,



2.8



CHAPTER two



Salmonella, Plesiomonas, and Yersinia were identified as causative agents in 26 waterborne disease outbreaks in the United States (Table 2-1). Although all of these pathogens

can cause gastroenteritis, infection with enterohemorrhagic E. coli O157:H7 can result in

bloody diarrhea. In susceptible persons, particularly children and the elderly, this infection

can sometimes progress to hemolytic-uremic syndrome whereby kidney failure can result

in serious illness or death (Yoon and Hovde, 2008). Cattle and other ruminants are significant sources of E. coli O157:H7. A few other E. coli strains can also cause hemorrhagic

disease, and strains of enterotoxigenic E. coli can cause a mild to severe watery diarrheal

illness in young children and travelers (Hunter, 2003).

Enteric-like Bacteria.  Enteric-like bacteria are found in feces and transmitted by the

fecal-oral route of exposure, but they are also found in various aquatic niches. Drinking

water–related genera in this group include Vibrio and Aeromonas. Vibrio cholerae can

cause gastroenteritis. Two toxin-producing serotypes, V. cholerae O1 and O139, can

cause cholera, a disease characterized by profuse watery diarrhea leading to dehydration

and loss of electrolytes. In the developing world, lack of access to rehydration therapy

and medical care are causes of considerable illness and death from cholera. V. cholerae

caused disease outbreaks in two tropical U.S. territories (Kramer et al., 1996; Blackburn

et al., 2004).

Aeromonas hydrophyla and other aeromonads are commonly found in the environment,

including distribution system biofilms. Only a few strains of A. hydrophyla are human

opportunistic pathogens. They can cause gastroenteritis as well as a number of other more

serious illnesses that can develop following wound infections. Waterborne transmission is

possible but not proven (Borchardt, Stemper, and Standridge, 2003).

Treated water from a properly operated water treatment system (i.e., in compliance with

all pathogen-related regulations) should be free of enteric and enteric-like bacteria. These

organisms are inactivated by all disinfectants commonly used in water treatment. Disease

outbreaks caused by these bacteria have only occurred after consumption of water that was

untreated, inadequately treated, or contaminated following treatment, such as by crossconnections or back-siphonage within the distribution system or by use of a contaminated

container.

Campylobacter.  Campylobacter spp. are genetically related to Helicobacter spp. (see

below) and, like Helicobacter, have a helical shape but are otherwise like enteric bacteria

in terms of being a leading cause of foodborne and waterborne gastroenteritis (Moore et al.,

2005). Between 1993 and 2006, species of Campylobacter were involved in 18 outbreaks,

most involving the thermophilic species C. jejuni (Table 2-1). Other less frequent human

infecting species include C. coli and C. upsaliensis. Campylobacter was also the agent

responsible for most bacterial outbreaks in Canada (Schuster et al., 2005). Although infection with Campylobacter leads mostly to GI illness, in some cases, it can lead to Reiter’s

syndrome, which is an arthritic disease affecting the joints (~1 percent of cases); GuillainBarré and Miller Fisher syndromes, which cause acute neuromuscular paralyses (~0.1 percent of cases); and other diseases (Peterson, 1994; Dorrell and Wren, 2007). Men are more

susceptible to campylobacteriosis than women (Strachan et al., 2008). Domestic and wild

birds are a significant source of Campylobacter, but a number of other warm-blooded animals including pets can also be sources. Campylobacter can remain viable in environmental

waters for extended periods of time in a nonculturable state, and they can also form biofilms

and infect free-living protozoa. As with enteric bacteria, Campylobacter is amenable to

conventional water treatment and disinfection. A related genus, Arcobacter, contains several emerging foodborne and waterborne pathogenic species (especially A. butzleri) (Ho,

Lipman, and Gaastra, 2006; Snelling et al., 2006b; Miller et al., 2007). Arcobacter have







HEALTH AND AESTHETIC ASPECTS OF DRINKING WATER



2.9



been identified in water samples collected during two U.S. waterborne disease outbreaks

involving Campylobacter and other agents (Figueras, 2008).

Helicobacter.  This genus currently contains many named and unnamed gastric, intestinal,

and hepatic species. The human-infecting species, Helicobacter pylori (H. pylori), is found

in the stomach where it can cause gastritis. Most infected persons remain asymptomatic,

but duodenal or gastric ulcer may develop in about 5 to 10 percent of cases. H. pylori also

causes mucosa-associated lymphoid tissue (MALT) lymphoma and is a major risk factor

for gastric adenocarcinoma (Kusters, van Vliet, and Kuipers, 2006).

In developed countries the mode of transmission of H. pylori appears to be mostly by

person-to-person from H. pylori-containing vomitus, saliva, stools, or medical equipment.

Some species, H. pylori included, can infect both humans and wild animals. Hence, animals

may represent a source of spread among humans (Solnick and Schauer, 2001; On, Hynes,

and Wadstron, 2002; Bellack et al., 2006).

The possibility of waterborne transmission of H. pylori is an area of active research.

Once excreted into the environment, H. pylori quickly transits to a nonculturable coccoid

cell state, which may (Cellini et al., 1994; She et al., 2003) or may not (Eaton et al., 1995;

Kusters et al., 1997) be infectious. Some Helicobacter species can persist in water in a

culturable state for only a few hours, but H. pylori can survive for days to weeks (Shahamat

et al., 1993; Konishi et al., 2007; Azevedo et al., 2008), a period sufficient for exposure

and infection in persons drinking untreated, fecal-contaminated water (Baker and Hegarty,

2001; Rolle-Kampczyk et al., 2004). H. pylori has been detected in surface and groundwaters by several investigators but has never been cultured from these sources, perhaps

because of limitations of the assays used (She et al., 2003; Watson et al., 2004). H. pylori

may gain entrance to drinking water distribution systems through either infiltration or

treatment deficiencies and has been detected in distribution system biofilms in a nonculturable state (Park, MacKay, and Reid, 2001; Watson et al., 2004; Giao et al., 2008). H. pylori

can also infect the protozoan Acanthamoeba (see below), remaining culturable for up to

eight weeks (Winieka-Krusnell et al., 2002).

H. pylori is readily killed by concentrations of disinfectants typically used in drinking

water treatment. As a possible corollary to this, infection rates of H. pylori in the United

States (20 percent of people under age 40 and 50 percent over age 60) are decreasing to the

point where some models show the organism gradually disappearing from the population

over the next century (Rupnow et al., 2000).

Legionella.  Legionella bacteria can cause legionellosis, which can be either a self-limiting

febrile illness called Pontiac fever or a serious type of pneumonia called Legionnaires’

disease with symptoms that are indistinguishable from pneumococcal pneumonia (Fields,

Benson, and Besser, 2002). The primary human exposure route is thought to be the inhalation of aerosols of water containing high concentrations of Legionella such as during

showering. Aerosol inhalation of Legionella containing waters from cooling towers and

whirlpool spas are other common, nondrinking water–related exposure routes, but disease

outbreaks derived from these sources are not included in the data in Table 2-1. Waterborne

ingestion of low levels of Legionella is common, perhaps universal, but is not associated

with disease.

The CDC began reporting disease outbreaks caused by Legionella bacteria in 2001.

In the six-year reporting period 2001 through 2006, there were 26 outbreaks involving

156 cases and 12 deaths due to Legionella from “water intended for drinking” (Table 2-1)

(Blackburn et al., 2004; Liang et al., 2006; Yoder et al., 2008). Thus, in the United States,

Legionella causes more drinking water–related outbreaks (but not more cases), and probably

more serious illness and mortality, than any other microorganism. An estimated 8000 to 18,000

persons are hospitalized with legionellosis each year in the United States (Marston et al., 1997).



2.10



CHAPTER two



Mortality rates from Legionnaires’ disease used to be significant (15–30 percent) but have

been falling since 1980 because of better and faster diagnosis and more widespread use of

prophylactic antibiotic therapy (Diederen, 2008). Although a number of different Legionella

species are frequently found in water distribution systems, about 91 percent of confirmed

cases of community-acquired Legionnaire’s disease are caused by L. pneumophila, and,

of this species, 84 percent were L. pneumophila serogroup 1 (Yu et al., 2002). Of exposed

individuals who become ill, most are elderly, smokers, or have weakened immune systems

or underlying illnesses. About 20 other species have been implicated in human disease

(Riffard et al., 2004).

Legionella are naturally occurring bacteria (not the result of fecal pollution) widely

distributed in fresh water, including groundwater and wet soil (Riffard et al., 2004), mostly

as a parasite of protozoa. Growth may occur in the environment in the presence of algae

and cyanobacteria (Fliermans, 1996; WHO, 2002). Small numbers of these organisms can

survive chlorination and have been found in distribution and plumbing system biofilms

(Rogers and Keevil, 1992).

The organism can multiply within many different types of protozoan hosts (e.g.,

Acanthamoeba spp. and Hartmanella spp.), but only at temperatures above 20°C (Fliermans,

1996; Snelling et al., 2006a; Ohno et al., 2008). Environments such as hot water systems,

showerheads, taps, and respiratory ventilators favor Legionella growth (Diederen, 2008).

It is believed that the ability to multiply within protozoan hosts enables L. pneumophila to

evade disinfection and to infect lung macrophages (phagocytic white blood cells) following inhalation.

It has been suggested that control actions should be taken whenever concentrations of

Legionella exceed 0.1 colony-forming unit (CFU) per mL or when heterotrophic bacteria

(see section on Indicators of Water Quality) exceed 10,000 CFU per mL (Health and Safety

Commission, 2000; WHO, 2007). Some protozoan hosts can withstand high concentrations

of chlorine and high temperatures for brief periods, and Legionella embedded within biofilms are also quite resistant to disinfection (Thomas et al., 2004; Loret et al., 2005). Thus,

it is difficult to eliminate Legionella from plumbing systems. Legionella can be controlled

in hot water storage tanks by keeping the temperature at 60°C, but high temperatures present a risk for scalding. The installation of thermostatically controlled mixing valves can

eliminate the scalding risk (WHO, 2006). High concentrations of chlorine can eliminate

Legionella, but such doses can corrode pipes. Therefore, most remediation contractors

employ superheating to eliminate Legionella from building plumbing systems. However,

some species can withstand 70°C for up to an hour and remain infective, so recolonization

of plumbing systems following heat-shock treatment may occur (Allegra et al., 2008).

Mycobacteria.  As with Legionella, Mycobacteria are free-living bacteria in water and

soil (including plant potting soil) that often colonize water distribution systems. As with

Legionella, Mycobacteria have been shown to be able to survive within a number of protozoa (Vaerewijck et al., 2005; Mura et al., 2006; Pagnier et al., 2009). Environmental

mycobacteria (EM), including the so-called Mycobacterium avium complex (M. avium and

M. intracellulare; MAC), can be waterborne pathogens under certain conditions (Pedley

et al., 2004; Vaerewijck et al., 2005). MAC can infect the lungs or GI tract, particularly

those of AIDS patients. Symptoms can include fatigue, cough, weight loss, and fever. In

AIDS patients, the bacterium can cause debilitating disease and death. Some species of

EM, MAC organisms in particular, have been isolated from water taps in medical facilities

with the same species isolated from AIDS patients in those facilities; however, the degree

of risk for either AIDS patients or healthy persons is unknown. The introduction of antiretroviral therapy for AIDS patients has reduced the amount of disease due to MAC and other

mycobacteria (Jones et al., 1999). Many EM other than MAC organisms (e.g., M. gordonae,

M. kansasii, M. abscessus, M. fortuitum, M. xenopi) have been found in water distribution







HEALTH AND AESTHETIC ASPECTS OF DRINKING WATER



2.11



systems, often more frequently than MAC organisms, and some of these organisms have

also been categorized as opportunistic pathogens associated with human disease.

Mycobacteria are resistant to various environmental stresses and water treatment disinfectants compared to most other waterborne bacteria and viruses (LeChevallier, 2006; Shin

et al., 2008). The ability of Mycobacteria to persist in water distribution systems is associated with a complex cell wall, survival or growth at warm water temperatures, association

with biofilms, and survival within protozoa. The role of protozoa in the persistence and

virulence of EM in distribution systems and the resistance of EM to disinfection requires

additional study.

Opportunistic Pathogens.  For information on Acinetobacter, Enterobacter, Klebsiella,

Pseudomonas, and other bacteria groups with species that are potentially pathogenic in

persons with weakened immune systems or in other susceptible subpopulations such as

burn patients, the reader is referred to AWWA (2006), Leclerc, Schwaartzbod, and Dei-Cas

(2002), and Szewzyk et al. (2000). Increasing levels of antibiotic resistance are a growing

problem in members of these and other genera (Taubes, 2008).

Viruses

Along with prions (misfolded proteins that can cause disease in some animals including

humans) and viroids (small, circular strands of RNA that can infect some plants), viruses

are among the smallest, most abundant infectious agents on earth. They range in size from

0.02 to 0.3 mm. They consist of a core of nucleic acid (either DNA or RNA) surrounded

by a protein capsid or shell. Some viruses also have an outer host-derived lipid membrane.

They depend on host cells for reproduction and have no metabolism of their own. Enteric

viruses comprise a number of classes of viruses that infect the intestinal tract of humans

and animals and are excreted in their feces (Carter, 2005; Nwachuku and Gerba, 2006).

Most pathogenic waterborne viruses can cause acute GI disease, although some cause more

severe illnesses. Enteric viruses that infect humans generally do not infect other animals

and vice versa, although there are a few exceptions to this rule. Viruses that have caused or

have the potential to cause waterborne disease are discussed next.

Norovirus and Other Calicivirus.  Of the four groups that comprise the Calicivirus family (Caliciviridae), two can infect humans: noroviruses (NVs) and sapoviruses (SVs).

Noroviruses were previously called small round-structured viruses (SRSV), human caliciviruses (HCV), or Norwalk-like viruses. Sapoviruses were previously called Sapporo-like

viruses. With the exception of Legionella pneumophila and Giardia lamblia (see below),

NVs have caused more identified waterborne disease outbreaks than any other biological

agent. Because caliciviruses cannot be grown in the laboratory and because these viruses

are highly infectious, many outbreaks of unknown etiology are likely caused by NVs

(Schaub and Oshiro, 2000). In addition, because illness symptoms, acute gastroenteritis,

are generally mild compared to those of some other agents, it is likely that many other NV

outbreaks are never identified and thousands of additional cases are never reported. Indeed,

NVs are estimated to cause 93 percent of the nonbacterial gastroenteritis in the United

States (Fankhauser et al., 2002). NVs likely cause more cases of foodborne illness than

any other pathogen.

Between 1993 and 2006, there were 15 identified waterborne disease outbreaks (3612

cases) in the United States due to NVs. Of the 12 outbreaks in which a cause was identified, 9 involved the consumption of untreated contaminated water (including two in which

a chlorinator was not functioning), two followed a back-siphonage or cross-contamination

event (with other possible causes in one), and one involved an improperly cleaned ice-making



2.12



CHAPTER two



machine. Transmission is mainly by the fecal-oral route, with person-to-person spread also

playing an important role. Airborne transmission over short distances and spread by contaminated objects (fomites) may also facilitate spread during outbreaks (Parashar et al.,

2001). Outbreaks due to the consumption of contaminated foods, particularly molluscan

shellfish, are common. Historically, NV disease was often referred to as “winter vomiting

disease,” reflecting the seasonal outbreak peak and one of the most common illness symptoms in addition to diarrhea.

Rotavirus.  Although no waterborne disease outbreaks due to rotaviruses (RVs) have

occurred in the United States in the past 14 years, outbreaks have occurred in earlier years

and in other countries as well. RVs are responsible for a significant amount of disease, primarily among infants and young children (Gray et al., 2008). Symptoms in children include

vomiting followed by watery diarrhea lasting four to seven days and fever. Most children

are infected by age 2 to 3. Adults are susceptible, but in many cases, adults are asymptomatic, though still infectious. The annual pattern of infection in the United States, a winter

peak with disease spreading from the west coast in late fall to the east coast in the spring,

appears to be due in large part to interstate differences in birth rates (Pitzer et al., 2009).

Dehydration can be rapid but can be combated with rehydration therapy. In the developing

world, lack of access to rehydration therapy and medical care results in 600,000 to 900,000

deaths each year, which is 6 percent of all mortality of children under age 5 (Bass, Pappano,

and Humiston, 2007). Death due to RV in the United States is rare (20–60 per year), but

an estimated 477,000 medical care visits and 55,000 to 70,000 hospitalizations each year

are a significant burden on health care resources and the economy (Parashar, Alexander,

and Glass, 2006).

RVs are primarily transmitted by the fecal-oral route, but there is growing evidence of

respiratory transmission as well. RVs have a low infectious dose (Ward et al., 1986) and

can persist on surfaces for long periods of time and on hands for an hour or more, likely

contributing to RVs apparent hand-to-mouth mode of transmission (Cook et al., 2004). RV

is capable of surviving for weeks to months in surface and groundwaters in an infectious

state (Caballero et al., 2004; Espinosa et al., 2008). Infection from livestock and pets has

been reported but is uncommon (Cook et al., 2004).

Because natural infection confers significant immunity and because two U.S. Food and

Drug Administration-licensed RV vaccines are available, the CDC now recommends routine vaccination for infants (Parashar, Alexander, and Glass, 2006; Cortese and Parashar,

2009). The vaccines protect against most, but not all, RV serotypes (Gentsch et al., 2005).

Vaccine use has resulted in delayed onset and reduced severity of RV illness among children in the United States (Staat et al., 2008).

Hepatitis A Virus.  Hepatitis A virus (HAV) is the sole member of the genus Hepatovirus

within the small RNA virus family. It is the cause of most cases of infectious hepatitis, an

inflammatory disease of the liver (Cuthbert, 2001). In countries with poor sanitation, most

people are infected with HAV as children. Disease symptoms in children are either mild or

absent and subsequent immunity is lifelong. In the United States and other industrialized

countries, most people reach adulthood having never been exposed to HAV. Disease symptoms are generally more severe when the first HAV infection occurs in adulthood rather

than childhood (www.who.int/mediacentre/factsheets/fs328/en/index.htmL). Hepatitis can

involve liver inflammation, with symptoms of dark urine and subsequent jaundice (yellowing of skin and eyes due to the inhibition of hemoglobin breakdown) and death in rare cases.

Acute disease lasts 2 to 4 weeks and full recovery can take 8 to 10 weeks, with excessive

fatigue a common postinfection problem. Relapse occurs in some people. Between 1993

and 2006, two drinking water–related outbreaks occurred in the United States involving the

consumption of untreated water from contaminated residential sources.