保健医療科学

2023

Vol.72 No.1 p.31－42

Topics: Recent topics in public health in Japan 2023

＜ Review ＞
Recent water quality incidents and a methemoglobinemia outbreak in infants
due to inadequate plumbing of a university hospital's private water supply
ASAMI Mari, MIYOSHI Taro, MIURA Takayuki
Area on Water Management, Department of Environmental Health, National Institute of Public Health
Abstract
Water supply facilities that supply water to more than 100 residents or supply more than 20 m3 of water per day are called specified privately owned water supply systems (SPOWs). SPOWs and small water
systems require proper maintenance and management at their facilities, especially small water systems
including private drinking water wells, where many water quality incidents involving health hazards haveoccurred. Most water quality incidents in SPOWs occurred in facilities where the groundwater was used as
raw water, requiring thorough water quality management by those who install SPOWs. In addition to recent
water quality incidents associated with microbial contamination in drinking water storage tanks, the incident at a building of university hospital is introduced. In October 2021, methemoglobinemia developed in
10 of 17 infants in the neonatal intensive care unit of the university hospital. It was found that these infants
had been fed milk that had been prepared in the kitchen within the building of university hospital. It was
finally proved that the water was contaminated with nitrite contained in the anticorrosion agent used in the
air-conditioning system due to cross-connection.
Abbreviations
DWQSs, drinking water quality standards
MHLW, Ministry of Health, Labour and Welfare
SPOWs, specified privately owned water supply systems
keywords: drinking water supply; risk management; waterborne infectious disease; methemoglobinemia;building design(accepted for publication, December 21, 2022)

I. Frequent incidents in specified privately
owned water supply systems (SPOWs)
SPOWs are water supply facilities that supply water tomore than 100 residents or supply more than 20 m3 of water
per day. As of March 31, 2021, there were 8,228 SPOWs forapproximately 370,000 people in Japan. [1] (see Figure 1).
Although some facilities are supplied only by a public watersupply service, the number of SPOWs is increasing every
year. The main reasons for this increase are some hospitals
and other facilities use their own wells to save costs of pub-lic water supply or to prepare as a backup for emergency
events like an earthquake.
As a rule, for new facilities or remodeling work under the
category of SPOWs, it is necessary to consult with the public health center in advance (at the time of planning) before
doing any work related to SPOWs. The right side of Figure
1 illustrates an explanation of a slightly complicated definition of SPOWs and the public notice, especially for small
water systems.
Water supply systems require proper maintenance andmanagement at their facilities, especially small-scale fa-

Corresponding author: ASAMI Mari
2-3-6 Minami, Wako, Saitama 351-0197, Japan.
Tel: 048-458-6304
E-mail: asami.m.aa@niph.go.jp

J. Natl. Inst. Public Health, 72 (1) : 2023

31

ASAMI Mari, MIYOSHI Taro, MIURA Takayuki
Water supply business that supplies water to meetthe general demand through the water supply
system

上水道事業

Water supply service(a)5,000

individuals

Supply water to a popula�on of >5,000 individuals(1,312 services, water supply popula�on: 121.28 million)

Small-scale water supply service(a)(publicly or privately operated)100

individuals
Waterstorage tankvolume of

10 m3

Private water supply for dormitories,
company housing, etc.

簡易水道事業

Supply water to a popula�on between 101 and 5,000 individuals.
(2,507 services, water supply popula�on: 1.74 million)

Speciﬁed building water supply(a)

簡易専用水道Speciﬁed privately owned
water supply systems (SPOWs)(a)

専用水道

Supply water to a popula�on of >100 individuals orwith a maximum daily supply of >20 m3.
(8,228 services, water supply popula�on: 370,000)
Including facili�es receiving water from Water Supply
Service only

Small water supply facili�es(b) 飲料水供給施設
Supply water to a popula�on between 50 and <100 individuals.

System with a storage tank volume of >10 m3

Speciﬁed building water supply 小規模貯水槽水道
System with a storage tank volume of <10 m3

Commercial drinking water well(c)Private drinking water well(c)

業務用
飲用井戸

一般飲用井戸Figure 1 Categories of drinking water supply (modified by the authors from [1]).
In addition to those shown in this Figure 1, the Water Supply Act is applied to “wholesale water supply service.”
Facilities covered by the Act on Maintenance of Sanitation in Buildings (applicable to specified buildings), inns,
public bathhouses, and food-related businesses are not included in “potable wells, etc.”(a) Designated by the Water Supply Act, (b) designated by some local governments, and (c) designated by theofficial notes for hygiene management of drinking water wells.
Water supply
service 4%

Tank
13%

Small-scale service
11%

Water supply service (4%)
Small-scale water supply service (11%)

Small water
system
44%

SPOWs
26%

Specified privately owned water supply system (26%)
Small water system incl. private water wells, etc. (44%)
Tank storage (13%)
Unknown (2%)

Figure 2 Percentage of water supply types in the water quality
incidents with health hazard between 1983 and 2012
(adopted from Kishida et al., 2015 [2]).

cilities such as SPOWs and private drinking water wells,
where many water quality incidents involving health hazards have occurred (see Figure 2; Kishida et al. [2]). Manywater quality incidents in SPOWs occur in facilities whereindividual groundwater is used as raw water, requiring
thorough water quality management by those who install
SPOWs and appropriate guidance by the government.
In this study, the authors would like to generally introduce
the water quality incidents especially related to buildings.
In addition to recent water quality incidents associated withmicrobial contamination in drinking water storage tanks, theincident at a university hospital building is introduced.

II. Water quality incidents caused by malfunctioning facilities and devices
The Ministry of Health, Labour and Welfare (MHLW)
requests local governments and water suppliers to report
the water quality incidents that excessively do not follow
the drinking quality standards (DWQSs) or those that could
lead to health hazards [3]. On the basis of the information

32

reported to the MHLW [4], major water quality incidents
caused by malfunctions of facilities and equipment within
the last 4 years are shown in Table 1. Unexpected backflow
through an overflow tube to the drinking water storagetank and cross-connection were the most common causesof reported water quality incidents. On the basis of theknowledge learned from these incidents, we should continuously pay attention to the water supply building facilities
or equipment to prevent inadequate piping and malfunction
especially during disinfectant injection.

III. A norovirus outbreak in a commercial
building
Three incidents of gastroenteritis or diarrheal diseases
occurred because of microbial contamination in drinking water storage tanks between 2019 and 2022 (Table 1). The two
incidents with the contamination in concrete drinking water
storage tanks installed in the basement of buildings happened
in Hyogo Prefecture and Tokyo in 2019 and 2022, respectively. A total of 35 gastroenteritis cases were identified in three

J. Natl. Inst. Public Health, 72 (1) : 2023

Recent water quality incidents and a methemoglobinemia outbreak in infants due to inadequate plumbing of a university hospital's private water supply
restaurants in a commercial building (built in 1970) in Kobe
City, Hyogo Prefecture, in February 2019. On the basis of
the outbreak investigation by the local public health center,norovirus GI.2 and GII.4 Sydney 2012 were detected in stool
samples collected from five patients and water samples fromrestaurants’ tap and a groundwater collection tank [5].
The water storage tank stored water from a public watersupply, and the stored water was pumped up to a water tankon the roof, before being distributed to each floor (Figure 3).
Water infiltrates in buildings are collected in groundwatercollection tanks, and there was an overflow tube from thewater storage tank to the groundwater collection tank. A
water pipe above the groundwater collection tank was broken, and unfortunately, the drainage pump was out of order.
Groundwater flowed into the water storage tank throughthe overflow tube, and drinking water was contaminatedby the groundwater. It is not known why noroviruses were
contained in the groundwater, but the building is located in
the downtown area of Kobe City and the groundwater surrounding the building could be contaminated by untreatedsewage [6]. Noroviruses have been detected in groundwater samples collected in private wells [7], and pathogen
contamination in groundwater is one of the major causes ofwaterborne outbreaks in Japan.
Similar waterborne outbreaks due to contamination ofdrinking water storage tank at the basement of buildings
have been reported for Cryptosporidium in Hiratsuka,
Kanagawa Prefecture, in 1994 [8]; Giardia in Chiba Prefecture in 2010 [9]; norovirus GI and Campylobacter jejuni in
Osaka in 2013 [10]; and norovirus GI in Tokyo in 2022. In
1977, the Building Standards Act was revised and the use of
a water storage tank with all surfaces that can be checkedvisually has become mandatory. Buildings constructed before 1977 still exist, in fact, and their owners are obligatedto operate and maintain the water supply facilities properly.
In Japan, if a building complies with the standards at thetime of construction, it will not be deemed nonconformingToa water tankon the roof
Publicwater
supplyWater pipe break
Malfunction ofdrainage pump

Groundwatercollection tankFlow back throughan overflow tube
Pump

Drinking water
storage tankeven if the standards are subsequently revised (so-called
existing nonconformity).

IV. Outbreak of methemoglobinemia in a hospital
A chemical incident occurred because of a cross-connection in a building. On October 19, 2021, methemoglobinemia developed in 10 of 17 infants in the neonatal intensive
care unit of Gunma University Hospital, Maebashi, Gunma,
Japan [11]. It was found that these infants had been fed milkthat had been prepared in the kitchen on the first floor of
the same hospital building, and it was suspected that theevent was caused by nitrite in the water used to prepare themilk. Treatment was immediately initiated, and fortunately,
the incident did not become more serious, but normal operations of the hospital had to be suspended because water
was supposedly contaminated.
In methemoglobinemia, the hemoglobin in red blood
cells changes to abnormal methemoglobin, causing theskin and mucous membranes to turn blue. It is also calleda blue baby syndrome because the whole body turns blue.
These symptoms are caused by the ingestion of nitrite or
nitrate. Many cases of methemoglobinemia have been reported worldwide for a long time [12], mainly in European
countries and the United States. In 1996, a serious case of
cyanosis in a newborn baby due to nitrite of 36.2 mgN/L (asnitrogen concentration) in the well water used for preparing
bottles of infant milk formula at home was also reported in
the north Kanto area in Japan [13].
The hospital conducted a water quality survey and foundthat the nitrite concentration was abnormally high, up to
490 mgN/L [14] exceeding the DWQS by more than 10,000
times higher in some points. Because of the abnormal water quality, the water was supposed to be from the exclusive
water supply system of the university hospital (hereinafterreferred to as “tap water,” which is produced by treating
groundwater within the facility). The city health department and hospital conducted a water quality survey andfound that the water quality abnormality was limited to thetap water in the north building. The north building includes
outpatient and inpatient areas, a dialysis room, and a kitchen, where milk for the newborn room was prepared. The
hospital organized an investigation committee, in which theauthor was asked to participate as an external expert.

Figure 3 The water supply system in the commercial
building. The drinking water storage andgroundwater collection tanks were made ofconcrete and placed at the basement as partof the building.

J. Natl. Inst. Public Health, 72 (1) : 2023

33

ASAMI Mari, MIYOSHI Taro, MIURA Takayuki

V. Accidents caused by incorrect plumbing in
the building
The committee investigated the route of drinking water,route of water for air conditioning in the hospital facility,
and operation status of switching water for air conditioning before and after the onset of the accident. Additionally,
temporal changes in water quality abnormalities and spatial
distribution of nitrite in the hospital were investigated, andanalysis of substances in the drinking water and bacteriological tests were conducted. As a result, it was found that
there was a connection point between the tap water andhot/cold water pipe for air conditioning via a check valve,
which allows water to flow only from tap water piping to the
air-conditioning system with a simple structure. Althoughreverse flow from the air-conditioning system to the tap water piping could be effectively restricted by the function of
the check valve, complete sealing by check valves may not
be generally guaranteed because of unexpected erroneous
motions of the valve or deformation as a result of corrosion
even when the valves are installed properly.
An anticorrosion agent was injected into the hot water
pipes for air conditioning every day using an injection pumpcontrolled by a timer to prevent rust, and the anticorrosion
agent contained nitrite and other substances. Generally,benzotriazole or other substances are used as additives forthe anticorrosion. Nitrite and other substances containedin the anticorrosion agent were detected in the tap water(for drinking) collected from the hospital at the moment of
this chemical incident. Because there was no other equipment from which these components were injected, it was
concluded that the check valve was not working properly
and the air-conditioning water containing the anticorrosion
agent flowed back, mixed with the water, and contaminatedone side of the building through the piping of the upper water on the top floor. A daily volume of 13 L of chemical (6.4
kg as nitrite) was injected into a chilled water generator;
the generator was shut down for 6 days from October 13
to 18. The amount of chemical injected during this period
corresponds to 38.4 kg nitrate (7.8 kg of nitrite-nitrogen(NO2-N)). It was suspected this high-concentration portion may have unexpectedly flowed into the water in the
air-conditioning system because of the malfunctioning valve
on October 18. Water for the air-conditioning system wascirculated through the facility, including other buildings in
the area of the medical department, supplied by a pumpinstalled in the central machine room. Additionally, theanticorrosion agent of the hot water system of the northbuilding (water volume 11 m3) entered the water supply
system at the highest nitrite concentration of 4,800 mg/L
(corresponds to 370 mgN/L), based on the calculation.

34

After disconnecting the water supply system and cleaning the air-conditioning pipe system and the water and hot
water piping system, nitrite was no longer detected in thewater supply and hot water. Therefore, it was concluded
that the nitrite in the drinking water was due to contamination of the anticorrosion agent contained in the hot water inan air-conditioning system and that the methemoglobinemia
in the infants was due to the nitrite contained in the water
for air conditioning and in the drinking water.

VI. Hospital “private water supply” and water supply service
The “tap water” in this case was not supplied by the water service run by the local city but by a SPOW that pumped
groundwater from the university grounds, which the hospital independently purified and disinfected. The hospital had
a contract with the city’s water supply service for a shorttime. However, for the most part, the SPOW treated only
its own groundwater and supplied it via rooftop water tanks
installed in each building.
In response to this incident, the city health department,
which has jurisdiction over the facility, conducted on-site
investigations, water quality tests. It immediately issued adirective requesting the suspension of water supply in thehospital wards and an investigation into the cause, to prevent secondary accidents, whereas the hospital’s investigation committee examined the cause of water contaminationand measures to prevent recurrence.
Meanwhile, Maebashi City’s Waterworks Bureau received an urgent request for an emergency water supply,
and two water trucks were dispatched every day over a
period of approximately 10 days, as the hospital is the corefacility in the area with a high degree of urgency.

VII. Recovery phase
Investigation of the cause revealed that the water piping
equipped in air conditioning system and the water piping
used in the water supply system had been directly connected by a check valve with a simple structure (Figure 4 [15])since the construction of the ward approximately 20 years
ago. In the piping shown in Figure 5 [15], this connection
is not capable of completely preventing backflow from the
air-conditioning water piping to that of the water supply
system (Figure 6 [15]). On the basis of the results of theinvestigation, the hospital disconnected the water piping for
air conditioning from that for the water supply system asa measure to prevent recurrence. Afterwards, the hospital
implemented intensive cleaning of the water supply systempiping and confirmed that nitrite was no longer detected.

J. Natl. Inst. Public Health, 72 (1) : 2023

Recent water quality incidents and a methemoglobinemia outbreak in infants due to inadequate plumbing of a university hospital's private water supply

A

Check valve

B

Check valve
stopperOpen

ClosedFigure 4 Structural drawing (vertical crosssection) of a check valve. The
valve has a simple mechanism,and the sealing properties are loweven when operating properly.
Figure 5 The water system in the hospital building. (A) The pipe connected to the air-conditioning system. The part where thecheck valve was installed is indicated with a white arrow. (B)An anticorrosion agent was injected from a tank with a pump,both of which were installed in the central machine room.

Generalservice tank
CentralMachineBuilding

Expansion
tank

Drinking
water tank(e.g., toilet flushing)

Centralized hot
water supply
ping system also
contaminatedCeiling pipe

Water
tank

80 m
deep
well

Airconditioning
systemCentral Machine
Building
Corrosion inhibitor
injected every day

Usually add
water to theairconditioning
systemMixer tap
defectHospitalrooms, etc.

The flow
direction at thetime of theaccident

Hospitalrooms, etc.

Central kitchen
Milk production

Hot watertank

DialysisShould not be connected to air-conditioning system piping

Flow of contaminatedwater at the time of theaccident

Check valve not working

The North Building
Figure 6 Schematic diagram of ward piping. Dashed lines indicate wards where accidents occurred. The
authors added the contaminated water flow to the Gunma University press release on December 16, 2021 [14].

Then, the water supply system in the north building, thesite of the accident, was restored.
Although the hospital suspended outpatient care for approximately one week, many inner workers were hard at work, carrying emergency water in polyethylene tanks using temporary
piping from other routes. Analyzing the nitrite concentrationin each of the many hot water circulation systems and faucets
in the building and cleaning the nitrite in the water taps took
more than one month to complete from the start of the investigation of the original water supply system.

VIII. The simulation of water flow in thebuilding
Pipeline calculations were performed to reproduce theflow of water in the building with a particular emphasis on
the reverse flow of water from the piping for the air conditioning to that for water supply. EPANET [16], a software
for pipeline simulation, was used. The flow rate based on
the estimated water volume and information on pipes basedon the committee survey were utilized in the simulation
system.

J. Natl. Inst. Public Health, 72 (1) : 2023

35

ASAMI Mari, MIYOSHI Taro, MIURA Takayuki
Hydrological simulations in the north building were
performed for two cases: base demands at the two nodes
adjacent to the piping connected to the air conditioning (i.e.,kitchen and shower) were 5 L/sec (Figure 7A) and 10 L/sec(Figure 7B), and the water demands at the kitchen (Demand1) and shower (Demand 2) were moderately at a higher level. In other words, the water demands of 10 L/sec are within the expected range during the designing of the facility.
The reservoir with a head of 50 m described on the top of
the two figures corresponds to the rooftop tank from which
tap water is distributed to the entire building. Therefore, in
usual conditions, all the water in the pipeline described in
Figure 7 should be introduced from this reservoir. It should
be noticed here that all the simulations were performedA

under the assumption that the check valve described in
Figure 7 did not work properly. Therefore, both upward anddownward flows were possible in the piping connected tothe air-conditioning system.
In case the water demand in both Demands 1 and 2 is
5 L/sec (Figure 7A), water in the piping connected to the
air-conditioning system flows downward with a flow rate of
0.17 L/sec. As mentioned earlier, this flow regime is normal
and in accordance with the design concept. Conversely,
upward flow with a flow rate of 0.05 L/sec is expected tobe generated when the water demands in both Demands 1
and 2 increased to 10 L/sec (Figure 7B). This alteration in
the flow direction is attributed to the elevated head loss inthe piping adjacent to the “Reservoir” shown in Figure 7

Reservoir(Head = 50 m)

12.5 L/sec

10 L/sec

0.17 L/sec

The other side of
the building

Demand 1(Kitchen)

Check valve
B

Reservoir(Head = 50 m)

12.5 L/sec

Demand 2(Shower)

Air-conditioning system(Head = 45 m)
20 L/sec

0.05 L/sec

The other side of
the building

Check valve

Demand 1(Kitchen)

Demand 2(Shower)

Air-conditioning system

Figure 7 Hydraulic simulations of the flow in the hospital building. Temporalwater demands at Demands 1 and 2 are (A) 5 L/sec (22.5 m3/day), and(B) 10 L/sec (45 m3/day). The check valves described in this Figure 7
did not work properly; both upward and downward flows were possible in the piping connected to the air-conditioning system.

36

J. Natl. Inst. Public Health, 72 (1) : 2023

Recent water quality incidents and a methemoglobinemia outbreak in infants due to inadequate plumbing of a university hospital's private water supply(i.e., rooftop tank). As the water usage in Demands 1 and
2 increased, the flow rate in the piping connected to therooftop tank also increased. Increase in flow rate results inincrease in friction loss and decrease in the available headat the branch of the piping connected to the air-conditioning
system. Eventually, the head of the air-conditioning system
overcomes the one associated with the rooftop tank. In suchsituations, a reverse flow from the air-conditioning system
to the piping of the water supply system could occur.

IX. Relationship with regulations
The following is an excerpt from the Office Communication, plumbing fixtures for drinking water (including
plumbing fixtures that share the same water supply system as drinking water) shall not be directly connected toother plumbing facilities. 4) regarding the legal position.
In this case, the connection point with the water piping for
air conditioning was in a hospital ward, and therefore, theprovisions of Article 129-2-4 of the Building Standard Law
Enforcement Order (Cabinet Order No. 338 of 1950) wereapplicable to this case. However, if there is a misconnection with other piping facilities in the building, there is apossibility of contaminating the water to be used, and eventhough it is not directly regulated by the Water Supply Law,
it is necessary to keep this in mind.
When confirming the installation of an SPOW under
Article 32 of the Water Supply Law (Law No. 177 of 1957),
prefectures, must ensure that the structure of the watersupply facilities concerned is such that there is no risk ofwater contamination and that it complies with the facility
standards. It must be ensured that it is not connected topipes used for different purposes. Additionally, the publichealth center shall continue to provide guidance to the private waterworks installer. Moreover, if deemed necessary
to ensure proper management of the waterworks, the public health center shall appropriately supervise the private
waterworks installer by collecting necessary reports or
conducting on-site inspections as stipulated in Article 39,
Paragraphs 1 and 2 of the Waterworks Law.
In the event of drinking water quality abnormalities, occurring at water service providers, private water supply installers, private drinking water wells, etc. (other than thoserelated to the Food Sanitation Law), public health centersmust immediately contact the Water Supply Division,
Pharmaceuticals and Consumer Health Bureau, MHLW,
based on the “Guidelines for Drinking Water Health Risk
Management Implementation” and “Proper Implementationof Health Risk Management and Provision of Information
on Damage to Water Facilities and Abnormal Water Quality, etc.” it is necessary to immediately contact the Water

Supply Division, Pharmaceuticals and Consumer HealthBureau, MHLW.

X. Published notice
In this case, because the infant’s symptoms of poisoningby nitrous acid were acute and obvious, the provision ofmilk was stopped immediately, treatment was initiated, andthe cause was immediately treated properly.
In general, the plumbing in hospitals, hot springs, andlodging buildings is often complex, but no other pipes
should ever be connected to the water supply system for
drinking. The management of circulating water in the hotwater system, including from the perspective of Legionella
control, will require further attention in the future.
In addition to aging, expanding, and remodeling of buildings, buildings are affected by summer and winter air-conditioning piping system changes and pressure fluctuations. It
may be difficult to continuously secure appropriate personnel who are familiar with the facility and its structure due topersonnel transfers, contract changes, etc.
If warm or smelly water comes out of the cold water
faucet or if the continuous monitoring of dialysis machinesshows abnormalities, changes in the water quality may bepresent.
Additionally, in areas where pesticides and fertilizers areused or groundwater is contaminated, nitric and nitrous acidconcentrations may be high to begin with, requiring carefulwater quality control even when there is no piping error.
The SPOWs that use groundwater do not have a wide-area backup system with a distribution pipe network or sparepipes and pumps, making it difficult to respond in the eventof an earthquake, plumbing accident, or accidental watercontamination. Routine cooperation with local waterworks
and neighboring institutions is required.
We hope that this paper will be of interest to public healthsector personnel and engineers.

XI. Conclusions
In SPOWs, incidents such as cross-connections, aging
facilities, and accidental water contamination are likely tooccur. Recent accident cases are summarized. As for theoutbreak of methemoglobinemia at the University Hospital,
it was caused by the backflow of nitrite in the anticorrosion
agent in the water for air conditioning due to cross-connection. Hydraulic calculations also showed that backflow canoccur from air-conditioning water. We must be extremely
careful about the inadequate piping in facilities, especiallythose related to medical care.

J. Natl. Inst. Public Health, 72 (1) : 2023

37

ASAMI Mari, MIYOSHI Taro, MIURA Takayuki

References[1] 厚生労働省．水道の基本統計，令和 2 年度水道の種類．
2021．
MHLW. [Basic statistics of drinking water supply, types ofwater supply in FY2020.] 2021. https://www.mhlw.go.jp/
content/000916895.pdf (in Japanese) (accessed 2022-12-03)[2] 岸田直裕，松本悠，山田俊郎，浅見真理，秋葉道宏．我が国における過去30年間の飲料水を介した健康危機事例の解析（1983～2012年）．保健医療科学．
2015;64(2):70-80.
Kishida N, Matsumoto Y, Yamada T, Asami M, Akiba M.
[Analysis of health-related incidents associated with drinking water in Japan in the last three decades (1983-2012).] J
Natl Inst Public Health. 2015;64(2):70-80. (in Japanese)[3] 厚 生 労 働 省． 飲 料 水 健 康 危 機 管 理 実 施 要 領（ 平成 9 年 3 月，平成25年10月一部改定）．
2013.
MHLW. [The operating procedure on health crisis management of drinking water (Heisei 9 nen 3 gatsu. Heisei 25
nen 10 gatsu ichibu kaitei).] 2013. https://www.mhlw.go.jp/
stf/seisakunitsuite/bunya/topics/bukyoku/kenkou/suido/
kikikanri/inryo.html (in Japanese) (accessed 2022-12-03)[4] 厚生労働省．水質汚染事故等の発生状況．健康影響の発生した水質汚染事故（令和 4 年 6 月現在）．
2022．
MHLW. [Occurrence of drinking water contamination
incidents. Water quality incidents with health hazard. As
of June 2022.] 2022. https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/topics/bukyoku/kenkou/suido/kikikanri/03.html(in Japanese) (accessed 2022-12-03)[5] 有川健太郎，野本竜平，花房剛志，米澤武志，濵夏樹，
中西典子，田中忍，岩本朋忠．地下式受水槽のノロ
ウイルス汚染を原因とする食中毒事例と近年の神戸市で発生した下痢症ウイルス事例について．ウイル
ス性下痢症研究会第32回学術集会抄録集．
2021:22.
Arikawa K, Nomoto R, Hanabusa T, Yonezawa T, Hama N,
Nakanishi N, Tanaka S, Iwamoto T. [A foodborne outbreak
due to norovirus contamination of water storage tankinstalled in the basement and recent outbreaks of viralgastroenteritis in Kobe City.] Proceedings of the 32nd Congress of Japan Viral Gastroenteritis Study Group. 2021:22.
(in Japanese)[6] 三浦尚之．地下水の微生物汚染とリスク管理．公衆衛生．
2021;85(2):78-82.
Miura T. [Microbial contamination in groundwater andrisk management.] The Journal of Public Health Practice.
2021;85(2):78-82. (in Japanese)[7] Miura T, Takino H, Gima A, Haramoto E, Akiba M. Recovery of nucleic acids of enteric viruses and host-specificBacteroidales from groundwater by using an adsorption-direct extraction method. Appl Environ Microbiol.
2021;87(18):e0071021.

38[8] 黒木俊郎，渡辺祐子，浅井良夫，山井志朗，遠藤卓郎，宇仁茂彦，木俣勲，井関基弘．神奈川県内で集団発生した水系感染Cryptosporidium症．感染症学雑誌．
1996;70(2):132-140.
Kuroki T, Watanabe Y, Asai Y, Yamai S, Endo T, Uni S,
Kimata I, Iseki M. [An outbreak of waterborne Cryptosporidiosis in Kanagawa, Japan.] Kansenshogaku Zasshi.
1996;70(2):132-140. (in Japanese)[9] 篠崎邦子，岸田一則，富田隆弘，遠藤幸男，小林八重子，
石井俊靖．ジアルジアによる集団感染事例について．
病原微生物検出情報（IASR）．
2014;35(8):7-8.
Shinozaki K, Kishida K, Tomita T, Endo Y, Kobayashi Y,
Ishii T. [A Giardiasis outbreak in Chiba Prefecture, November 2010]. Infectious Agents Surveillance Report (IASR).
2014;35(8):7-8. (in Japanese)[10] 大阪市．水を原因食品とする食中毒について．平成
26年度第 1 回大阪市食の安全に関する連絡会，情報
提供１：食中毒事例紹介．
2014
Osaka City. [A waterborne disease outbreak.] First Liaison
Meeting on Food Safety in Osaka City, FY2014. Information
1: Incidents of foodborne outbreaks. 2014. (in Japanese)[11] Press release of the university. 2021.10.20. [“Ten hospitalized infants have hematosis, possibly due to well watercontamination: Gunma University Hospital, Maebashi City,
Gunma prefecture, announced on October 20 that 10 hospitalized infants developed methemoglobinemia, a conditionin which red blood cells lose their oxygen-carrying capacity. All of them are alive and recovering well. High levels of
nitrogen compounds were detected in the well water used
for the milk, and the hospital is investigating the source.
According to the university, a nurse noticed the pale complexion of an infant admitted to the neonatal intensive careunit on the afternoon of October 19. Water taken from thefaucet contained 490 mg/L, up to 12,250 times the standard
value.” ] (in Japanese)[12] WHO. Nitrate and nitrite in Drinking-water, Backgrounddocument for development of WHO Guidelines for Drinking-water Quality, 2003. https://apps.who.int/iris/bitstream/
handle/10665/75380/WHO_SDE_WSH_04.03_56_eng.pdf(accessed 2022-08-08)[13] Tanaka J, Horigome H, Imai H, et al. A case of methemoglobinemia, cyanosis, in a newborn baby due to nitric acid
36.2mgN/L (as nitrogen concentration) in the well water athome (North Kanto). Clinical Pediatrics. 1996;49(7):16611665.
[14] 群馬大学プレスリリース．群大病院北病棟からの上
水系統の給水再開について（水質異常の原因と改善措置）．
2021年12月16日．
Gunma University press release: December 16, 2021
“Resumption of water supply to the water system from theNorth Ward of Gunma University Hospital (cause of water

J. Natl. Inst. Public Health, 72 (1) : 2023

Recent water quality incidents and a methemoglobinemia outbreak in infants due to inadequate plumbing of a university hospital's private water supply
quality problems and remedial measures) https://www. gunma-u.ac.jp/wp-content/uploads/2021/12/e80aa0ed221861e5da094e0ef9edc568.pdf (in Japanese) (accessed 2022-0310)[15] Office of Water Quality Control, Division of Water Supply,
Ministry of Health, Labour and Welfare: December 16,
2021 “Cases of abnormal water quality due to contamina-tion of water from air conditioning system in private waterworks” (administrative communication).
[16] Environmental Protect Agency. EPANET 2.2.0: An EPA
and Water Community Collaboration. June 22, 2020. https://www.epa.gov/sciencematters/epanet-220-epa-and-water-community-collaboration. (accessed 2022-08-08)

J. Natl. Inst. Public Health, 72 (1) : 2023

39

ASAMI Mari, MIYOSHI Taro, MIURA Takayuki
Table 1 Major water quality incidents from 2019 to 2022a
Type of water supply, the number Facility
Summary of incident
Cause of the incident Further actionof people supplied with or who
possibly ingested the water, thenumber of patients, and date of theincident
Water supply system with tank
Underground Gastroenteritis cases were reported to Kobe City, andContamination of un- Consideration andstorage (commercial building)drinking water the local public health center identified the contamination derground drinking implementation of
Hyogo
storage tank of drinking water storage tank with untreated groundwa- water storage tank measures to prevent
The number of people to be suprecurrence
ter through an overflow tube. Norovirus GI and GII weredetected in water samples collected from the tap andplied: unknown
groundwater collection tank in the building. Kobe City inThe number of patients: 35
February 5, 2019
structed the owner of the water supply system including
the storage tank to thoroughly maintain and manage
them.
Private water supply, Hokkaido
Chlorine
The drainage pump in the drainage tank adjacent to the Failure of miscella- Repaired theSeptember 13, 2018
disinfection
hotel's drinking water storage tank (underground) failed, neous drainage tank drainage and cleaned(deep well)raising the water level in the drainage tank to flow into pumpthe drinking water
the storage tank from the old pipe. This was discovered
storage tank.
because of a complaint from a guest. Water quality was
Renewal of pumps
tested and found to contain general bacteria exceedingin the drainage tankthe standard value (56,000 CFU/mL), with abnormal
and installation of
taste and odor. No health hazards occurred.
a water level alarmsystemWater supply system with tank
Underground A public sewer flowed into the water supply because of The incorrect joint The purpose of thedrinking water a misconnection to the pipe of the water storage tank at of the pipe and public pipe located in thestorage(condominium)
storage tank the condominium facility. The pipes were disconnected, sewer pipe
storage tank was unHyogo
and the water in the storage tank, rooftop tank, and pipes
known. No drawings
The number of people who possibly
were ozonated to clean.
were found.
ingested the water: 200
The number of patients: 15
June 18, 2020
Small water supply
Sewage overflow from the inhibition collector installed Sewage inflow into The water supply(Common building)on the first floor of the building flowed into the drinking storage tank due to was changed to a
Hokkaido
water storage tank under the floor through cracks in the inadequate building direct connection
structuresystem that directly
September 26, 2020
floor surface. We confirmed cloudiness and foaming in
the water in the storage tank and prohibited drinking the
supplies water to thehigh-set water tankwater from the storage tank. As an emergency measure,the drainage of the inhibition collector was improved, andusing temporary
piping, and drinkthe drinking water storage and high-set water tanks werecleaned and confirmed to meet water quality standards.
ing was resumed
because there wasno longer any risk ofwastewater flowing
into the tank.
SPOWs (hospital)
MembraneDuring the periodic on-site inspection, the residual chlo- Insufficient adjust- He instructed that
Shizuokafiltration
daily inspections
rine level was less than 0.05 mg/L, so the water supply ment of chlorine
November 20, 2020
(industrial
injection equipment should be conductwas stopped and chlorine injection dose was adjusted.
water)The dose of chlorine injection was increased, the water
ed to ensure thatin the water storage tank was replaced, and water supply
residual chlorine is
was provided after confirming that 0.2 mg/L of residual
checked and that thechlorine was detected at the terminal hydrant.
water supply technical manager shouldsupervise properly.
Because the residual chlorine level was less than 0.05
Small-scale water supply system Chlorine
Insufficient adjust- Educate residents
Shizuokadisinfection
mg/L in the periodic water quality inspection, the com- ment of chlorine
who conduct daily
December 18, 2020
(deep well)pany introduced the fact that water should be boiled if it injection equipment inspections and conand failure to proper- tracted workers who
was to be consumed. It was found that sodium hypoconduct inspections.
chlorite had leaked out because of a loose air vent drain ly conduct dailybolt on the chlorine injection pump and was not being
inspections
injected properly. The injection pump was adjusted, andit was confirmed that 0.2 mg/L of residual chlorine wasnow detected.
Monitoring system To ensure that the
SPOWs
Deferrization Because of damage to a component in the membrane
shutdown due to(Multi facilities)
demanganese, filtration equipment, water containing contaminants
alarm system isdamage to memFukuoka
activatedremoved by membrane filtration (concentrated water)
working properly,
July 15, 2021
carbon, andwas mixed with the purified water, causing manganese brane filtration
check the operation
membraneand chloride ion levels and color to exceed water quality equipment compo- status during daily
filtration
standards.
nents and power
inspections.
(deep well)
Additionally, the system monitoring the water treatment outages
facility did not function because of a power outage,
resulting in contaminated purified water being supplied
for approximately half a day. Parts of the membrane
filtration equipment were replaced, and the water tank
was cleaned, and it was confirmed that the water quality
standards were met.

40

J. Natl. Inst. Public Health, 72 (1) : 2023

Recent water quality incidents and a methemoglobinemia outbreak in infants due to inadequate plumbing of a university hospital's private water supply
Municipal water supply
Hyogo
August 18, 2021

Chlorine
The inspector contacted the water utility because residu- Injection failure ofThoroughly manage
disinfection
al chlorine was not detected during a routine water qual- disinfectant
the facility and notify(spring water) ity test and Escherichia coli was detected. The blockage
the public waterin the pipe of the disinfection equipment was repaired on
utility in the eventthe same day. In the daily inspection, residual chlorineof water quality
was also undetectable from the 17th, but the contractor
abnormalities.
did not report this to the water utility. No adverse healtheffects occurred.
Small-scale water supply (nursery Drinking water The standard plate count exceeded the DWQS after
The excess standard Temporary waterschool)quality testing constorage tank cleaning the drinking water storage tank. Five diarrhea plate count is preKanagawa
cases were identified in the nursery school, although the sumed to be caused tinues for the time
The number of people to be supby biofilm contained being.
causal relationship was unknown. Because water within red rust
plied: 150
red rust color had come out of the tap for more than 1
The number of patients: 5
week after cleaning the tank, the tank was cleaned again.
August 23, 2021
Water quality testing confirmed no abnormality, and thedrinking restriction of tap water was lifted. The nurseryschool will periodically test the water quality parameters
including residual chlorine.
SPOWs (hospital)
Chlorine
Ten infants developed methemoglobinemia at a hospital. The water piping for Temporary waterGunma
air conditioning isquality tests shall bedisinfection
Because high concentrations of nitrite-nitrogen were
The number of people to be sup- (deep well)detected in water purified and disinfected from the uni- directly connected conducted to confirm
to the water supply that there are no abplied: 3,000
versity’s groundwater used to prepare powdered milk,system piping, and normalities. Do not
Number of patients: 10
nitrite was thought to be the cause of methemoglobinnitrite-nitrogen is(See this article for details.)
directly connect theemia. As a result of the investigation, no abnormalities
October 19, 2021
were found in the water quality of the groundwater, and mixed in the water water supply system
supply system from piping to otherit was thought that the cause was contamination of thewater for air conditioning connected to the water supply the water piping for piping, even throughcheck valves are
piping via a check valve (chuck valve). The air-condition- air conditioning
installed. Issued by
ing water contains a chemical containing nitrous acid as
the office.
an anticorrosion agent to prevent rust in the piping, andit was concluded that the air-conditioning water containing nitrous acid was mixed into the water supply systembecause of the malfunctioning of the check valve.
As a recurrence prevention measure, the water supply
system piping was disconnected from the air-conditioning
water piping and the inside of the water supply systempiping was cleaned. As a result, nitrite-nitrogen was nolonger detected, and the water supply was resumed.
Wastewater flows
Small-scale water supply (mulConsider abolishing
Underground Unusual odor and turbidity of tap water was reported
into the drinking
titenant building)the use of underdrinking water to the local public health center. There was malfuncdrinking water stor- ground drinkingTokyostorage tank tion of the drainage pump in the wastewater tank, andThe number of people to be supwastewater flowed into the drinking water storage tank. age tank because of water storage tanks
After repair of the pump, the underground drinking
malfunction of theplied: unknown
water storage tank and a water tank on the roof were not drainage pump and
The number of patients: 14
cleaned. Water samples collected from the tap exceeded breakage of drainage
March 3, 2022
the DWQSs of standard plate count, E. coli, odor, color,pipingand turbidity. Norovirus GI was detected in the tap waterand toilet flushing water samples and swab samples fromthe kitchen sink and ice machine. After cleaning thewater tanks, water quality testing confirmed the sample
met the DWQSs.
Unusual odor of tap water was again reported by a tenantof the building after 10 days. The drainage piping above
the drinking water storage tank broke, and drainage
water flowed into the tank. Water samples collected fromthe tap again exceeded the DWQSs of standard plate
count, E. coli, odor, color, and turbidity. After repairing thepiping and cleaning the water tanks, water quality testing
confirmed the sample met the DWQSs.
a

Incidents related to SPOWs were selected and organized from MHLW (2022) [4].

[Note 1] An excerpt from the Building Standards Act Enforcement Order
Article 129-2-4 The installation and construction of water supply, drainage, and other piping facilities to be installed in buildings shall be inaccordance with the following provisions. (Omitted)(2) Plumbing facilities for drinking water to be installed in buildings (excluding plumbing facilities that fall under the category of water supply
equipment prescribed in Article 3, paragraph (9) of the Waterworks Act): (2) In addition to the provisions of the preceding paragraph, theinstallation and construction of drinking water piping facilities (excluding piping facilities that fall under the category of water supply equipment prescribed in Article 3, paragraph (9) of the Waterworks Act) installed in buildings shall be as follows:(i) Plumbing fixtures for drinking water (including plumbing fixtures that share the same water supply system as that of drinking water) shall not be directly connected to other plumbing facilities.
(Omitted)

J. Natl. Inst. Public Health, 72 (1) : 2023

41

ASAMI Mari, MIYOSHI Taro, MIURA Takayuki＜総説＞
大学病院専用水道の配管不備による乳児のメトヘモグロビン血症発生と最近の水質事故について
浅見真理，三好太郎，三浦尚之
国立保健医療科学院生活環境研究部（水管理研究領域）

抄録
住民100人以上への給水または日量20m3以上の給水を行う水道施設を専用水道（SPOWs）という．
専用水道や小規模水道の施設では適切な維持管理が必要であり，特に個人の飲料水用井戸を含む小規模水道では，健康被害を伴う水質事故が多く発生している．SPOWの水質事故の多くは，地下水を原水として使用している施設で発生しており，SPOWを設置する側には水質管理の徹底が求められている．最近の飲料水貯水槽の微生物汚染に関連する水質事故に加え，大学病院の建物で発生した事故について紹介する．2021年10月，大学病院の新生児集中治療室で，乳児17人のうち10人にメトヘモグロ
ビン血症が発症した．これらの乳児は，大学病院の建物内の厨房で調製されたミルクを与えられていたことが判明した．最終的には，空調設備に使用されている防錆剤に含まれる亜硝酸塩が，クロスコ
ネクションによりミルクを調製した水に混入したことが判明した．
キーワード：飲料水供給，リスク管理，水系感染症，メトヘモグロビン血症，給水設備

42

J. Natl. Inst. Public Health, 72 (1) : 2023