Assignment 2- Risk Analysis
Please read the article on Carcinogenic and non-carcinogenic health risk assessment of heavy
metals in drinking water and answer the following questions
1a. Should the community be concerned about the carcinogenic effects of Lead? Why or Why
not? .....3 pts
1b. Based on your finding from (1a), what do you recommend?...........2 pts
2a. How about the non-carcinogenic effects of Barium? Why or Why not?...........3 pts
2b. Based on your finding from (2a), what do you recommend?............2 pts
3. Please read both articles on: Carcinogenic and non-carcinogenic health risk assessment of
heavy metals in drinking water and Communicable disease risk assessment
Discuss the major differences between the two approaches used in the articles
MethodsX 6 (2019) 1642–1651
Contents lists available at ScienceDirect
MethodsX
journal homepage: www.elsevier.com/locate/mex
Method article
Carcinogenic and non-carcinogenic health risk
assessment of heavy metals in drinking water of
Khorramabad, Iran
Ali Akbar Mohammadia , Ahmad Zareib , Saba Majidic ,
Afshin Ghaderpouryd,** , Yalda Hashempoure ,
Mohammad Hossein Saghif , Abdolazim Alinejadg,**,
Mahmood Yousefih , Nasrin Hosseingholizadehi,
Mansour Ghaderpoorij,k,*
a
Department of Environmental Health Engineering, Neyshabur University of Medical Sciences, Neyshabur,
Iran
b
Department of Health, School of Public Health, Social Determinant of Health Research Center, Gonabad
University of Medical Sciences, Gonabad, Iran
c
Department of Environmental Health Engineering, Health Center, Qazvin University of Medical Sciences,
Qazvin, Iran
d
Student Research Committee School of Public Health, Shahid Beheshti University of Medical Sciences,
Tehran, Iran
e
Department of Environmental Health Engineering, School of Health, Mazandaran University of Medical
Sciences, Sari, Iran
f
Department of Environmental Health Engineering, School of Public Health, Sabzevar University of Medical
Sciences, Sabzevar, Iran
g
Department of Public Health, Fasa University of Medical Sciences, Fasa, Iran
h
Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical
Sciences, Tehran, Iran
i
PhD. Student of Health Education and Promotion, Department of Health Education and Promotion, School of
Public Health, Tehran University of Medical Sciences, Tehran, Iran
j
Department of Environmental Health Engineering, School of Health and Nutrition, Lorestan University of
Medical Sciences, Khorramabad, Iran
k
Nutrition Health Research Center, Lorestan University of Medical Sciences, Khorramabad, Iran
A B S T R A C T
The continuous urbanization and industrialization in many parts of the world and Iran has led to high levels of
heavy metal contamination in the soil and then on the surface and groundwater. In this study, the concentrations
* Corresponding author at: Department of Environmental Health Engineering, School of Health and Nutrition, Lorestan
University of Medical Sciences, Khorramabad, Iran.
** Corresponding authors.
E-mail addresses: ghaderpoory_a@yahoo.com (A. Ghaderpoury), azimalinejad@gmail.com (A. Alinejad),
ghaderpoori.m@lums.ac.ir (M. Ghaderpoori).
https://doi.org/10.1016/j.mex.2019.07.017
2215-0161/© 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://
creativecommons.org/licenses/by/4.0/).
A.A. Mohammadi et al. / MethodsX 6 (2019) 1642–1651
1643
of 8 heavy metals were determined in forty water samples along distribution drinking water of Khorramabad,
Iran. The ranges of heavy metals in this study were lower than EPA and WHO drinking water recommendations
and guidelines and so were acceptable. The mean values of CDItotal of heavy metals concentrations in adults were
found in the order of Zn > Ba > Pb > Ni > Cr > Cu > Cd > Mo. The health-risk estimation indicated that total hazard
quotient (HQing + HQderm) and hazard index values were below the acceptable limit, representing no noncarcinogenic risk to the residents via oral intake and dermal adsorption of water. Moreover, the results of total risk
via ingestion and dermal contact showed that the ingestion was the predominant pathway. This study also
presents that the carcinogenic risk for Pb, Cr, Cd and Ni were observed higher than the acceptable limit (1 106).
The present study will be quite helpful for both inhabitants in taking protective measures and government
officials in reducing heavy metals contamination of urban drinking water.
The data analyzed in this study show a clear situation regarding the quality of drinking water in Khorramabad.
The results of this study can be used to improve and develop the quality of drinking water that directly affects
the health of consumers.
The present study will be quite helpful for both inhabitants in taking protective measures and government
officials in reducing heavy metals contamination of urban drinking water
© 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://
creativecommons.org/licenses/by/4.0/).
A R T I C L E I N F O
Method name: Application of carcinogenic and non-carcinogenic health risk assessment of heavy metals in drinking water
Keywords: Heavy metals, Non-carcinogenic risk, Carcinogenic risk, Ingestion, Dermal contact
Article history: Received 8 May 2019; Accepted 12 July 2019; Available online 19 July 2019
Specifications Table
Subject area:
More specific subject area:
Method name:
Name and reference of the
original method:
Resource availability:
Environmental Science
Drinking water monitoring and quality
Application of carcinogenic and non-carcinogenic health risk assessment of heavy metals
in drinking water
Concentration and ecological risk of heavy metal in street dust of Eslamshahr, Iran. Human
and Ecological Risk Assessment: An International Journal, 1-10
The data are available with this article.
Method details
Supply of healthy drinking water is necessary to human life, and safe drinking water should not
cause a remarkable risk to human health. The increasing trend of water shortage has various
negative impacts on economic development, human livelihoods, and environmental quality around
the world [1–3]. Numerous contaminants, including heavy metals, organic and inorganic
compounds, etc. may contaminate water. Among harmful and persistent contaminants found in
water, a special emphasis is given to heavy metals [4,5]. Rapid economic development and
industrialization in many parts of the world and Iran has led to high levels of heavy metal
contamination in the soil and then in the surface and groundwater [6–10]. The heavy metals are
released into the water naturally or via human activities [11,12]. Many heavy metals are the natural
elements of the earth’s crust. Weathering and decomposition of metal rock and ores can transfer
heavy metals in groundwater and have led to human exposure for the entire history of mankind
[5,13,14]. The levels of metals vary significantly from the soil of one region to another [15].
Anthropogenic activities considerably affect the availability of heavy metals in the ecosystems.
Heavy metals may be released into water the in large quantities via vehicle exhaust, poor waste
disposal, fossil fuel combustion, fertilizer and pesticide application, untreated wastewater irrigation,
and atmospheric precipitation from various human activities including mining, smelting operation,
1644
A.A. Mohammadi et al. / MethodsX 6 (2019) 1642–1651
agriculture, etc. which can influence human health by affecting on vegetation, food chain and water
quality [16]. Once released into the drinking water, heavy metals can be taken into the human body
through several pathways such as direct ingestion, dermal contact, inhalation, through mouth and
nose [17]. Heavy metals in water can cause extensive damage to the ecological environment and
consequently human health due to their unique characteristics such as toxicity, poor biodegradability and bioaccumulation [18–21]. Some heavy metals are detrimental for metabolisms in the
human body, serving as both structural and catalytic constituents of proteins and enzymes, but can
have adverse effects when the levels were greater than international guidelines [22]. During
prolonged exposure, heavy metals can accumulate in target tissues such as brain, liver, bones, and
kidneys in the human body resulting in serious health hazards, depending on the element and its
chemical form [23]. Health risk assessment of heavy metals is usually performed to estimate the
total exposure to heavy metals among the residents in a particular area. Risk assessment of
contaminants in humans is based on a mechanistic assumption that such chemicals may either be
carcinogenic or non-carcinogenic [24]. Generally, ingestion and dermal absorption are the major
pathways of exposure in water environment [25,26]. In order to assess water quality in an area
effectively, it is crucial to find possible human health impacts of contaminants in drinking water. The
traditional technique for estimating health impacts is to directly compare the analyzed levels with
guideline limits, but it is not adequately valid to provide comprehensive hazard levels and find
contaminants of the most important [27]. Health risk assessment is an essential method for
evaluating the possible health effects in water environments caused by numerous contaminants
[28,29]. This method has been extensively utilized by many researchers in literature for the
estimation of the adverse health effects possible from exposure to contaminated water [30,31].
Although ingestion is the predominant pathway of exposure to contaminants in drinking water,
inhalation and dermal absorption should also be considered [24]. Most health risk estimations
associated with human exposure to contaminants in soil, water, and air are based on the exposure
methods presented by the USEPA [13]. With the increasing trend of population, economy, and
industry growth in Iran, the study is required to determine the impacts of development on the
surface and groundwater, before any preventive measures can be considered in the land-use systems
and watersheds to decrease the contamination levels of heavy metals. The main objectives of the
present research were to determine levels of eight heavy metals including Lead (Pb), Chromium (Cr),
Cadmium (Cd), Molybdenum (Mo), Zinc (Zn), Copper (Cu), Barium (Ba), and Nickel (Ni) in the
drinking water of Khorramabad city and estimate health risks of non-carcinogenic (Pb, Cr, Cd, Mo,
Zn, Cu, Ba, and Ni) and carcinogenic (Pb, Cr, Cd, and Ni) metals with respect to daily drinking of
groundwater and dermal pathways for general adults in the community. The results of our research
may provide some insight into heavy metal contamination in water and are useful for inhabitants in
formulating protective procedures and health professionals in reducing heavy metal contamination
of water environment, and also serve as a basis for comparison to other areas both in Iran and
worldwide.
Materials and methods
Study area description
The geographic coordinates of the study area are 33 290 1600 N 48 2102100 E in DMS (Degrees Minutes
Seconds), located in the Khorramabad city, Lorestan Province in the west of Iran. Khorramabad is
situated in the Zagros Mountains with a warm and temperate climate. Natural springs are the main
sources of water supply in this city. At the 2016 census, its population was 373,416. Average annual
rainfall in this region is 488 mm. This city stands at an elevation of approximately 1147 m above sea
level [32]. The location map of the study area is depicted in Fig. 1.
Materials and sampling
Analytical grade HNO3 purchased from Merck Company was used in this work. Deionized water
was utilized for solution preparation and also for dilution objectives. All glassware was washed and
A.A. Mohammadi et al. / MethodsX 6 (2019) 1642–1651
1645
Fig. 1. Location map of sampling sites in the distribution network.
dried in an oven at 105 C. Sampling bottles were cleaned by rinsing in a metal-free soap and then by
soaking in 10% HNO3 before sample taking. Finally, the bottles were washed with deionized water.
Totally, forty water samples from 40 different sites along the distribution network were collected
during 2017 in order to measure the levels of potentially toxic heavy metals such as Pb, Cr, Cd, Mo, Zn,
Cu, Ba, and Ni in drinking water of Khorramabad city. These samples were then transported to the
laboratory and stored at 4 C until analysis.
Sample analysis
The collected samples were analyzed for eight heavy metals including Pb, Cr, Cd, Mo, Zn, Cu, Ba, and
Ni using standard methods for the examination of water and wastewater [33]. Concentrations of the
heavy metals in all samples were measured using an inductively coupled plasma mass spectrometry
(ICP-MS). The limit of detection (LOD) of individual metal was in the range 0.5–5 ng/L for water
samples.
Health risk assessment
Non-carcinogenic analysis
Risks of individual heavy metals. Risk assessment is defined as the methods of evaluating the
probability of occurrence of any given probable amount of the harmful health impacts over a
determined time period [34]. The health risk assessment of each contaminant is normally based on the
estimation of the risk level and is classified as carcinogenic or non-carcinogenic health hazards [35]. To
estimate the heavy metal contamination and potential carcinogenic and non-cancer health risk
caused via ingestion and dermal absorption of heavy metals in the water of the distribution network of
Khorramabad city, Hazard Quotients (HQ), Hazard Index (HI), and the Incremental Lifetime Cancer
Risk (ILCR) were used. The studied group in this study was adults.
Eq. 1 and Eq. 2 taken from the Environmental Protection Agency (USEPA) were applied to
determine the Chronic Daily Intake (CDI) via ingestion and dermal absorption routes, respectively
[25,36].
CDI
ingestion
¼
Cw :DI:ABS:EF:EP
BW:AT
ð1Þ
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A.A. Mohammadi et al. / MethodsX 6 (2019) 1642–1651
Table 1
Parameters and input assumptions for exposure assessment of metals through ingestion and dermal pathways.
Parameter
Unit
Heavy metal concentrations (Cw )
Daily average intake (DI)
Skin-surface area (SA)
Permeability coefficient (Kp)
Exposure time (ET)
Exposure frequency (EF)
Exposure duration (EP)
Conversion factor (CF)
Body weight (BW)
ABS
Average time (AT)
mg/L
CDI
dermal
¼
L/day
Cm2
Cm/hour
Hour/event
Day/years
Year
L/cm3
Kg
All
Days
Values
Ingestion
Dermal adsorption
–
2.2
–
–
–
365
70
–
–
18000
Pb, Cu, Ba 0.001, Cr, 0.002, Zn 0.006, Ni 0.0002
0.58
350
30
0.001
70
0.001
25550
70
0.001
25550
Cw :SA:Kp : ABS:ET:EF:EP:CF
BW:AT
ð2Þ
Where, Cw (in mg/L) is the concentration of heavy metals in water, SA (in cm2 ) is the skin area
available for contact, Kp (in cm/hour) is the permeability coefficient, ABS (unitless) is the dermal
absorption factor, DI (in L/day) is the daily average intake of water in the area, ET (in h/event) is the
exposure time, EF (in days/year) represents the annual exposure frequency, ED (in years) is exposure
period, CF (in L=cm3 ) is the unit conversion factor, BW (in Kg/person) is body weight, and AT (in days)
is the average time. The input assumptions and their values for computing the chronic daily intake
through oral ingestion and dermal absorption are summarized in Table 1.
The HQ for each heavy metal was estimated using the ratio of computed mean daily intake (ADI,
mg/kg/day) of a metal ingested with contaminated water to the reference oral dose (RfD) through oral
ingestion and dermal absorption for the residents. The sum of all HQs gives an estimation of total
potential health risks or HI. The calculation of the HI caused by water is presented as (Eq. 3):
HQ ¼
CDI
RfD
ð3Þ
Where, CDI and RfD are expressed in mg/kg-day.
The values of the RfD and cancer slope factor for different metals are listed in Table 2.
Hazard Index (HI) for multiple heavy metals. To estimate the total potential non-carcinogenic health
impacts caused by exposure to a mixture of heavy metals in water, the HI for several heavy metals was
computed according to the EPA guidelines for health risk assessment [37,38] using following Eq. 4:
Xn
HI ¼
HQ ¼ HQ Pb þ HQ Cr þ HQ Cd þ HQ Mo þ HQ Zn þ HQ Cu þ HQ Ba þ HQ Ni
ð4Þ
k¼1
Table 2
Reference dose (RfD) and cancer slope factor (CSF) for different metals.
Element
Rdforal
Rdfdermal
CSF (kg/day/mg)
Pb
Cr
Cd
Mo
Zn
Cu
Ba
Ni
1.4
3
0.5
5
300
40
70
20
0.42
0.015
0.005
1.9
60
12
14
5.4
8.5
41
6.1
0.84
A.A. Mohammadi et al. / MethodsX 6 (2019) 1642–1651
1647
The computed HI is compared to standard values: there is the possibility that non-carcinogenic
impacts may occur in the residents when HI > 1, while the exposed person is unexpected to experience
evident harmful health impacts when HI < 1 [39].
Carcinogenic analysis
The probable cancer risks due to exposure to a specified dose of heavy metal in drinking water can
be computed using the ILCR [40]. The ILCR is defined as the incremental probability of a person
developing any type of cancer over a lifetime as a result of twenty-four hours per day exposure to a
given daily amount of a carcinogenic element for seventy years [41]. The following equation (Eq. 5)
was commonly used for the calculation of the lifetime cancer risk:
ILCR ¼ CDI :CSF
ð5Þ
Where, CSF is the cancer slope factor and is defined as the risk generated by a lifetime average amount
of one mg/kg/day of carcinogen chemical and is contaminant specific.
The permissible limits are considered to be 106 and Zn > Cu > Cr > Ni > Pb > Mo > Cd.
Non-carcinogenic analysis
Human health risk assessment comprises the determination of the nature and magnitude of adverse
health effects in humans who may be exposed to toxic substances in a contaminated environment. In the
present work, exposure and risk assessments were carried out based on the USEPA methodology. Human
exposure to heavy metals principally occurs via pathways of drinking water, food, inhaled aerosol
particles and dust [43]. The degree of toxicity of heavy metals to human health is directly related to their
daily intake. However, ingestion via drinking water and dermal adsorption was considered in this study.
The first step in the non-carcinogenic analysis is the calculation of chronic daily intake (CDI) values. As
given in the Table 4, the mean levels of total CDI (CDItotal) in mg/kg-day are 1.00E-04 for Pb, 11.60E-04 for
Cr, 1.34E-05 for Cd, 1.60E-05 for Mo,1.48E-03 for Zn, 2.13E-04 for Cu, 2.55E-03 for Ba, and 1.09E-04 for Ni.
Therefore, the mean values of CDItotal of heavy metals concentrations for adults were found in the order of
Zn > Ba > Pb > Ni > Cr > Cu > Cd > Mo.
As seen in Table 5, all the studied heavy metals had total HQs below 1. Accordingly, the health risk
estimation of Pb, Cr, Cd, Mo, Zn, Cu, Ba, and Ni revealed the mean HQs suggesting an acceptable level of
non-carcinogenic harmful health risk in all samples taken from Khorammabed’s water distribution
A.A. Mohammadi et al. / MethodsX 6 (2019) 1642–1651
1649
network. From the computation of total HQs, it can be concluded that the contribution of the eight
metals to the non-carcinogenic health risk was in the order of Zn > Ba > Cr > Cu > Mo > Pb > Ni > Cd.
Moreover, to estimate the total potential non-carcinogenic impacts induced by more than one
metal, the HQ computed for each metal is summed and expressed as a Hazard Index (HI) [44]. The
mean values of HI through ingestion and dermal adsorption as wells as total HI were obtained to be
3.31E-03, 2.15E-06, and 3.32E-03, respectively. It shows neglectable non-carcinogenic risk to residents
’ health as the value of HI is below 1. The values of HI for heavy metals of inhabitants in the study area
are summarized in Table 5.
Carcinogenic risk analysis
Heavy metals (Pb, Cr (VI), Cd, and Ni) can potentially enhance the risk of cancer in humans [45,46].
Long term exposure to low amounts of toxic metals could, therefore, result in many types of cancers.
Using Pb, Cr (VI), Cd, and Ni as carcinogens, the total exposure of the residents were assessed based on
the mean CDI values given in Table 4. The carcinogenic risk assessment for adults is given in Table 6.
The values of cancer slope factor (CSF) for different metals used for carcinogenic risk assessment are
listed in Table 2.
For one heavy metal, an ILCR less than 1 106 is considered as insignificant and the cancer
risk can be neglected; while an ILCR above 1 10-4 is considered as harmful and the cancer risk
is troublesome. For the total of all heavy metals through all exposure routes, the acceptable level is
1 10-5 [46–48]. Among all the studied heavy metals, chromium has the highest chance of
cancer risks (mean ILCR 6.54 10-3) and nickel has the lowest chance of cancer risk (mean ILCR
9.16 10-5). The results of this research present that there was a cancer risk from the contaminants
to residents through the cumulative ingestion and dermal contact routes in the drinking water of the
region.
Conclusions
This study was conducted to evaluate the health risks of exposure to heavy metals along with the
water distribution network of Khorramabad city in Iran. Risk assessment relevant for the present
study comprises computations of carcinogenic and non-carcinogenic risk of water through ingestion
and dermal contact pathways. The maximum and minimum concentrations of heavy metals measured
were related to Ba (81.31 mg/L) and Cd (0.43 mg/L), respectively. The order of the heavy metals toxicity
according to mean concentrations measured in drinking water of the studied area was:
Ba > Zn > Cu > Cr > Ni > Pb > Mo > Cd. Themean values of CDItotal of heavy metals concentrations in
adults were found in the order of Zn > Ba > Pb > Ni > Cr > Cu > Cd > Mo. The HQs for those routes of
this work decline in the following order: ingestion > dermal adsorption, meaning that ingestion is the
dominant pathway of exposure to every receptor. The mean values of HI through ingestion and dermal
adsorption as wells as total HI were obtained to be 3.31E-03, 2.15E-06, and 3.32E-03, respectively.
Among all the studied heavy metals, chromium has the highest chance of cancer risks (mean ILCR
6.54 103) and nickel has the lowest chance of cancer risk (mean ILCR 9.16 10-5). The present study
will be quite helpful for both inhabitants in taking protective measures and government officials in
reducing heavy metals contamination of urban drinking water.
Declaration of Competing Interest
The authors of this article declare that they have no conflict of interests.
Acknowledgment
The authors would agree and thank Professor Mehdi Zarrei in SickKids - hospital in Toronto, Canada
for valuable comments and suggestions, allowing us to improve this paper. Also, the authors of this
study thanks to the Lorestan University of Medical Sciences (LUMS) to support this project and the
students involved in conducting the experiments.
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WHO/CDS/NTD/DCE/2007.4
Communicable disease
risk assessment: protocol for
humanitarian emergencies
June 2007
© World Health Organization 2007
All rights reserved.
The designations employed and the presentation of the material in this publication do not imply
the expression of any opinion whatsoever on the part of the World Health Organization
concerning the legal status of any country, territory, city or area or of its authorities, or concerning
the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border
lines for which there may not yet be full agreement.
The mention of specific companies or of certain manufacturers’ products does not imply that they
are endorsed or recommended by the World Health Organization in preference to others of a
similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary
products are distinguished by initial capital letters.
All reasonable precautions have been taken by the World Health Organization to verify the
information contained in this publication. However, the published material is being distributed
without warranty of any kind, either express or implied. The responsibility for the interpretation
and use of the material lies with the reader. In no event shall the World Health Organization be
liable for damages arising from its use.
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
1
Contents
Page
Acknowledgements
3
1. Introduction
4
2. Communicable disease threats
4
3. Risk assessment framework
5
4. References
10
Annex 1. Indicators to define potential hazard for
selected diseases
12
Annex 2. Risk assessment matrix
13
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
2
Acknowledgements
Edited by Dr John Watson, Dr Michelle Gayer and Dr Máire Connolly of the Programme on
Disease Control in Humanitarian Emergencies (DCE), Communicable Diseases cluster
(CDS/NTD).
This document is a product of the Communicable Diseases Working Group on Emergencies (CDWGE) at World Health Organization (WHO) headquarters. The CD-WGE provides technical and
operational support on communicable disease control to WHO Health Action in Crisis cluster
(HAC), WHO regional and country offices, ministries of health, other United Nations agencies,
and nongovernmental and international organizations. The Working Group includes the
departments of Epidemic and Pandemic Alert and Response (EPR) and Control of Neglected
Tropical Diseases (NTD) in the Communicable Diseases (CDS) cluster; Roll Back Malaria
(RBM), Stop TB (STB) and HIV/AIDS in the HIV/AIDS, Tuberculosis and Malaria (HTM)
cluster; departments of Child and Adolescent Health and Development (CAH) and Immunization,
Vaccines and Biologicals (IVB) in the Family and Community Health (FCH) cluster; Food
Safety, Zoonoses and Foodborne Diseases (FOS) and Public Health and Environment (PHE) in
the Sustainable Development and Healthy Environments (SDE) cluster; Injuries and Violence
Prevention (VIP) and Nutrition for Health and Development (NHD) in the Noncommunicable
Diseases and Mental Health (NMH) cluster; Security and Staff Services (SES) in the General
Management (GMG) cluster; and the Health Action in Crises (HAC) cluster and Polio
Eradication Initiative (PEI).
The following people were involved in the development and review of this document, and their
contribution is gratefully acknowledged:
Pino Annunziata HAC; Eric Bertherat, CDS/EPR; Sylvie Briand, CDS/EPR; Claire Lise
Chaignat, CDS/NTD; Yves Chartier, SDE/PHE; Claire Chauvin, DGR/POL; Karen Ciceri
CDS/NTD; Micheline Diepart HTM/HIV; Pierre Formenty, CDS/EPR; Dominique Legros,
CDS/EPR; Pamela Mbabazi CDS/NTD; David Meddings, NMH/VIP; Angela Merianos,
CDS/EPR; Tim Nguyen, CDS/EPR; Jose Nkuni, HTM/GMP; Salah Ottmani HTM/STB; Suzanne
O'Rourke CDS/NTD; William Perea (CDS/EPR); Zita Weise-Prinzo (NMH/NHD).
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
3
1.
Introduction
Humanitarian emergencies caused by conflict or natural disasters, are frequently characterized by
the displacement of large numbers of people, with severe disruption of basic infrastructure,
resulting in overcrowding, increased exposure to disease vectors, food insecurity, and lack of
access to safe water, sanitation, and basic health services. In populations affected by humanitarian
emergencies, the risk of communicable diseases is greatly increased (1), with particularly high
morbidity and mortality from communicable diseases in acute conflict situations (2). Death rates
among displaced populations up to 10 that of baseline rates have been reported, with
communicable diseases responsible for the majority of deaths (1). Diarrhoeal diseases, measles,
malaria (in endemic areas), and acute respiratory infections are the most important causes of
morbidity and mortality in displaced populations, particularly in the presence of high rates of
malnutrition (1). Reducing this risk is a crucial part of protecting these highly vulnerable
populations. A systematic assessment of the risk of communicable diseases, based on the best
available evidence (risk assessment), is necessary to guide interventions designed to mitigate this
increased risk (risk management).
2.
Communicable disease threats
The factors that influence exposure to, and facilitate transmission of, communicable diseases in
emergency settings are well-described (1). The risk of communicable diseases is associated
primarily with the size and characteristics of the displaced population: specifically, the amount
and availability of safe water and functioning latrines; the nutritional status of the displaced
population; the level of immunity to vaccine-preventable diseases such as measles; and the level
of access to health care services (3). The risks to populations affected by humanitarian
emergencies can be grouped together and assessed by disease category in a way that links to
specific risks and interventions, as follows.
2.1
Water-borne diseases
Large-scale population displacement often results in poor access to safe water and to adequate
sanitation facilities, facilitating water-borne and food-borne transmission of pathogens. In these
settings, diarrhoeal diseases such as cholera, typhoid fever and shigellosis can cause epidemics
with high rates of mortality (4). Hepatitis E, which is also spread by the faecal–oral route, can
result in jaundice and increased mortality in pregnant women (5). Furthermore, infection with
leptospirosis is associated with displacement after flooding and the resulting proximity of rats to
humans on shared high ground.
2.2
Vector-borne diseases
Malaria is endemic in over 80% of areas affected by humanitarian emergencies (6). Weakened
immunity due to malnutrition or co-infection, increased exposure to vectors owing to inadequate
shelter and the collapse of health services can increase risk of death from malaria (6). Arboviruses
such as dengue, yellow fever, Japanese encephalitis and Rift Valley fever; tick-borne illnesses
such as Crimean–Congo haemorrhagic fever and typhus; and other vector-borne diseases such as
plague are also endemic in areas affected by humanitarian emergencies. Increased exposure to
vectors as a result of substandard housing can increase risk.
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
4
2.3
Diseases associated with overcrowding
Measles, occurring in populations with low levels of immunization coverage, spreads easily in the
crowded conditions associated with displacement, and outbreaks are common (1). Crowding can
facilitate the transmission of meningococcal disease and may also contribute to the high
prevalence of acute respiratory infections in displaced persons. Crowded living conditions can
also aid the transmission of tuberculosis infection and diarrhoeal diseases.
2.4
Vaccine-preventable diseases
In addition to measles and meningitis, displaced populations are at increased risk for vaccinepreventable diseases such as polio, tetanus, pertussis and diphtheria when levels of baseline
immunization coverage are low.
2.5
Malnutrition
Poor nutritional status compromises host immunity, leading to more frequent, prolonged and
severe episodes of infections. Measles, diarrhoeal diseases, acute respiratory infections and
malaria can result in high morbidity and mortality in malnourished populations (7).
Additionally, public health programmes such as those for tuberculosis, malaria and HIV/AIDS
are at risk of being disrupted by an acute humanitarian emergency. Rapid identification of those
on treatment and prompt resumption of services are essential to ensure continuity of care. It is
also crucial to reduce the risk of development and spread of drug-resistant strains such as
multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDRTB).
3.
Risk assessment framework
The process of communicable disease risk assessment described here uses existing data to gauge
both the likelihood and the impact of communicable diseases. Assessing risk is critical to identify
priority interventions, to inform health planning, and to contribute to the reduction of morbidity
and mortality in emergency-affected populations. At the World Health Organization (WHO), the
Communicable Diseases Working Group on Emergencies (CD-WGE) uses available evidence
and expert opinion to define the risk of communicable diseases (that is, the probability and impact
of health effects from communicable diseases) in specific populations affected by humanitarian
emergencies. The group consists of 28 technical experts representing the various disease units at
WHO headquarters. The CD-WGE meets to assess the risks of communicable diseases in
populations affected by humanitarian emergencies and, based on this, to prioritize interventions.
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
5
Figure 1. Standard operating procedures for developing a
communicable disease risk assessment
Event/Trigger
Acute conflict or natural disaster, e.g. earthquake, flooding, tsunami
Convene urgent CD-WGE meeting
Real-time analysis of event, threats, risk: identify and quantify key communicable
disease risks and interventions
• Potential data sources
o MoH national databases
o WHO communicable disease epidemiological data summaries
o WHO databases: WHO EMS, EPI summaries, WER, WHO
global atlas database, UNAIDS, tuberculosis control annual
reports, ioint WHO-UNICEF reports, etc.
Technical note on communicable disease risk assessment and
interventions
•
•
•
•
3.1
Circulate for technical review: CD-WGE, WHO regional/country office
Date document for publication
Distribute widely to partner agencies (Ministries of Health, WHO offices,
UN agencies, NGOs, etc.)
Upload to WHO web site
(http://www.who.int/diseasecontrol_emergencies/guidelines/en/)
Risk assessment framework: a three-step approach
The potential for transmission of communicable diseases is influenced by a complex interplay of
host, agent and environment. Accurately defining risk requires a careful consideration of the
potential interactions of all three factors, in this case within the specific context of the area and
population affected by the emergency.
In response to an acute humanitarian emergency, the CD-WGE meets urgently to systematically
review multiple sources of data (including existing data on outbreaks notified to WHO and other
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
6
disease programmes, relevant Ministry of Health data from affected countries and relevant
published literature) in order to better define the risk of communicable diseases facing the
emergency-affected populations (Figure 1). The CD-WGE undertakes a basic three-step approach
when developing a communicable disease risk assessment (Table 1), modified from established
risk assessment methods (8). The steps are event description, threat/vulnerability assessment, and
risk characterization.
Event description is the process of systematically assessing the type of emergency and
the characteristics of the population displaced. Displacement caused by conflict,
particularly when rates of malnutrition are high, generally carries a higher risk of
mortality from communicable disease than displacement arising from natural disasters (3).
The size of the displaced population and the duration of the displacement, among other
factors, can influence the risk of transmission of communicable diseases.
The process of threat/vulnerability assessment identifies potential interactions between
the emergency-affected population (host factors), likely pathogens (agents) and exposures
(environment) that determine factors that facilitate communicable disease transmission.
Population factors include immunization coverage and underlying rates of malnutrition,
as well as community practices such as use of bednets and boiling of drinking-water.
Cultural practices, e.g. consumption of bushmeat or interaction with domestic animals,
may also contribute to communicable disease risk. A comprehensive consideration of
likely agents or pathogens is critical for the threat assessment. Specifically, endemic and
epidemic-prone diseases (and their seasonality), the history of recent outbreaks and the
communicable disease control programmes operating in the area must be considered.
Indicators, such as those used to quantify burden of disease or programmatic impact, are
also assessed (Annex 1). Environmental factors, such as shelter (amount, quality,
location), availability of safe water and sanitation and access to basic health care services,
can also strongly influence communicable disease transmission.
The third step, risk characterization, uses a risk assessment matrix to analyse the
available information on hazard and exposure for each disease under consideration
(Annex 2). Both aspects of risk – the potential magnitude of the health impact and the
likelihood of the event occurring – are approximately quantified and the overall risk is
then characterized using the matrix. Based on the overall risk assessment, interventions
for disease control are prioritized by evaluating additional factors such as cost,
technology, availability and infrastructure requirements
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
7
Table 1. Three-step communicable disease risk assessment
framework
Step
STEP 1
Event description
Main qualitative assessment(s)
•
•
Type of humanitarian emergency: conflict or natural disaster
(flooding disaster, earthquake, tsunami)
Characteristics of population displacement (size, duration,
location, demographics, etc.)
STEP 2
Threat/vulnerability
assessment (host, agent,
environment)
Host:
• Underlying malnutrition rates
• Immunization coverage (e.g. measles, polio)
• Community practices (e.g. use of bednets, boiling of
drinking-water)
• Community cultural practices (e.g. ritual slaughtering
practices)
• Availability of food
Agent:
• Endemic diseases present (e.g. malaria, Rift Valley fever)
• Epidemic-prone diseases and recent epidemics (e.g. cholera,
typhoid, meningococcal disease)
• Ongoing communicable disease control efforts
• Disease incidence, prevalence, seasonality (e.g. dengue,
Japanese encephalitis, malaria)
Environment:
• Amount, quality and location of shelter
• Availability of safe water and sanitation
• Thermal extremes
• Secondary toxic exposures
• Available infrastructure for health and social services;
access to basic primary health care services
• Presence of vectors (and potential for proliferation)
STEP 3
Risk characterization
•
Integration of information collected in Steps 1 and 2 into risk
assessment matrix to estimate overall risk to population based
the magnitude of potential impact and likelihood of a disease
occurring using a risk assessment matrix (Annex 2)
Very high: +++
High: ++
Low:
+
None:
–
No information available: N
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
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The outcome is a concise, timely and population-specific profile of projected communicable
disease risk, allowing evidence-based decision-making and focusing relief efforts on critical
immediate actions. The event-specific technical note is entitled Communicable disease risk
assessment and interventions. Using this mechanism, risk assessments have been performed for
the Horn of Africa flooding disaster (9), the Middle East crisis (10) and the Indonesia earthquake
(11) in 2006, and for the severe food shortage in Niger (12), the South Asian earthquake (13) and
the Asian tsunami in 2005 (14).
The CD-WGE mechanism focuses WHO technical capacity on reducing the risk and impact of
communicable diseases on emergency-affected populations. The risk assessment framework used
by the Working Group can inform the prioritization of interventions, identify priority diseases to
guide surveillance and early warning strategies, inform health policies and ultimately improve the
quality of data available for the ongoing protection of populations affected by humanitarian
emergencies.
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
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4.
References
1. Connolly MA et al. Communicable diseases in complex emergencies: impacts and challenges.
Lancet, 2004, 3(364):1974–1983.
2. Connolly MA, Heymann DL. Deadly comrades: war and infectious diseases. Lancet, 2002,
360:23–24.
3. Watson JT, Gayer M, Connolly MA. Epidemics after natural disasters. Emerging Infectious
Diseases, 2007, 13:1–5.
4. Goma Epidemiology Group. Public health impact of Rwandan refugee crisis: what happened in
Goma, Zaire, in July 1994? Lancet, 1995, 11(345):339–344.
5. Aggarwal R, Krawczynski K. Hepatitis E: an overview and recent advances in clinical and
laboratory research. Journal of Gastroenterology and Hepatology, 2000, 15:9–20.
6. Malaria control in complex emergencies: an interagency field handbook. Geneva, World
Health Organization, 2005.
7. Caulfield LE et al. Undernutrition as an underlying cause of child deaths associated with
diarrhea, pneumonia, malaria, and measles. American Journal of Clinical Nutrition, 2004,
80:193–198.
8. National Research Council. Risk assessment in the federal government: managing the process.
Washington, DC, National Academy Press, 1983.
9. Communicable disease risk assessment and interventions. Flooding disaster: Horn of Africa,
December 2006. Geneva, World Health Organization, 2006 (WHO/CDS/NTD/DCE/2006.9;
available from: http://www.who.int/diseasecontrol_emergencies/guidelines/flooding_hoa_3.pdf).
10. Guidelines for disease surveillance/early warning and response: Middle East crisis, August
2006. Geneva, World Health Organization, 2006 (WHO/CDS/NTD/DCE/2006.6; available from:
http://www.who.int/diseasecontrol_emergencies/guidelines/Middle%20East%20Crisis_WHO%2
0CD%20surveillance_early%20warning%20guidelines.pdf).
11. Indonesia earthquake-affected areas. Communicable disease risks and interventions, May
2006. Geneva, World Health Organization, 2006 (WHO/CDS/NTD/DCE/2006.3; available from:
http://www.who.int/diseasecontrol_emergencies/guidelines/Indonesia_post_earthquake_2.pdf).
12. Niger: communicable diseases risk assessment, July 2005. Geneva, World Health
Organization (available from:
http://www.who.int/diseasecontrol_emergencies/guidelines/Niger_risk_assessment.pdf).
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
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13. South Asia earthquake-affected areas, 2005: operational plan and communicable diseases
surveillance/early warning and response guidelines. Geneva, World Health Organization, 2005
(available from:
http://www.who.int/diseasecontrol_emergencies/guidelines/asia_earthquake_early_warning.pdf).
14.Tsunami affected areas, 2005: communicable disease risks and interventions. Geneva, World
Health Organization, 2005 (WHO/CDS/2005.34; available from:
http://www.who.int/diseasecontrol_emergencies/guidelines/tsunami_risk_assessment.pdf).
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
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Annex 1. Indicators to define potential hazard for selected diseases
Malaria
•
•
•
•
•
•
•
•
•
•
•
•
Measles
•
•
Estimated population at risk
Estimated population under 5 years of age at risk
Estimated pregnant women at risk
Reported malaria cases by year
Reported malaria cases in children under five years of age by year
Reported deaths attributed to malaria by year
Estimated malaria deaths per year
Estimated malaria incidence per 1000 population at risk per year
Estimated malaria prevalence
Population coverage, Insecticide-treated bednets/ indoor spraying of residual insecticide
Resistance to anti-malarial drugs
Resistance to insecticides
Number of cases reported annually
Immunization coverage (%), by year
Meningococcal disease
•
Cases and deaths reported, by year
•
Recent epidemics and serogroups involved
Yellow fever
•
Cases and deaths reported, by year
•
Recent epidemics
•
Estimated vaccine coverage (%)
Poliomyelitis
•
Cases and deaths reported, by year
•
Recent epidemics
•
Estimated vaccine coverage (%)
HIV/AIDS
•
Estimated number living with HIV/AIDS, by age and gender
•
HIV seroprevalence among ANC attendees
•
Estimated adult prevalence rate
•
Estimated number in need of ARV, including % children
•
Estimated number receiving ARV, including % children
•
National ARV regimen
•
Prevalence of HIV among adults with TB
Tuberculosis
•
Number of TB cases notified, by year
•
Case notification rates per 100,000, by year
•
Number of new smear-positive cases, by year
•
Rate of new smear-positive cases per 100,000, by year
•
Monitoring indicators, for DOTS: new cases and re-treatment cases
o
Number of cases notified
o
Number of cases registered
o
% cured
o
% completed treatment
o
% died
o
% failed
o
% default
o
% success
Malnutrition
•
Estimated size of at-risk population
•
Prevalence of moderate malnutrition (% of children with weight/height ratio of -3 Z-Scores)
•
Prevalence of severe malnutrition (% of children with weight/height ratio less than -3 Z-Scores)
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
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Annex 2. Risk assessment matrix
3+
Potential
magnitude
2+
of health impact
1+
1+
2+
3+
Likelihood of event occurring
Low risk
High risk
Very high risk
Potential magnitude of health impact
Severe (3+)
High morbidity/mortality
Moderate (2+) Excessive morbidity/mortality
Low (1+)
Minimal morbidity/mortality
Likelihood of epidemic occurring
High (3+)
Endemic disease with potential for epidemic transmission clearly present;
Widespread exacerbation of conditions favourable for communicable disease
transmission;
Highly susceptible population
Moderate (2+)
Endemic disease with potential for epidemic transmission present;
Some exacerbation of conditions favourable for communicable disease
transmission;
High background levels of immunity but large number of susceptible people
Low (1+)
Endemic disease with potential for epidemic transmission possibly present;
Conditions favourable for communicable disease transmission possibly
present;
Population largely immune
Communicable Diseases Working Group on Emergencies, WHO Disease Control in Humanitarian
Emergencies Program
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