AMOUGOU Judith Virginie
Doctor Ph.D in geography, University of Yaoundé I, email@example.com
Professor, University of Yaoundé I
Households in the city of Yaounde and in particular those of the Efoulan district are stuck in vulnerability due to the difficulties of access to drinking water, which results in increased multiple health risks. Surveys of water-borne diseases (amoebiasis, typhoid and itching) as well as a bacteriological analysis of groundwater have shown health risks due to pollution. Significant statistical tests of the variables established associations between access to water and household health conditions.
In this paper, we propose a qualitative and quantitative modeling of health risks that can serve as reference for public authorities and local populations within the framework of participatory management.
Key words : Yaounde, Efoulan, household, water access and health risk
In Cameroon, galloping demographic growth is not automatically accompanied by the development of easy access to the basic needs of the populations. The production capacity of essential goods (basic social infrastructure) such as drinking water supply by public authorities is far from meeting the needs of the population.
The indicators of the Millennium Development Goals (MDGs) relating to the supply of drinking water and sanitation, show that in Central Africa, of which Cameroon is part, the drinking water coverage remained below 60% in 2006. Moreover, according to the Third General Population and Housing Census (3rd RGPH, 2005), only 47.3% of the population of Cameroon have access to clean water.
Many studies have been carried out by researchers on the issue of water supply to populations around the world and in Yaounde in particular, and its impact on health. Some of these studies have highlighted the links between sanitation systems and the quality of the water consumed by the populations. For Nola and al. (1998), and Zebaze (2004), consumers of water from wells and springs in the city of Yaounde are exposed, in the long term, to health risks linked to poor physicochemical quality and, in the short term, to those related to microbiological characteristics. In this regard, the lack of partitioning of groundwater implies widespread pollution of the water in the city of Yaounde in general, and of Efoulan in particular.
The ways of access to water concern the one intended for drinking and for domestic use. These are: the water supply capacity, the alternatives available and the type of water collected by households.
The concept of risk refers to the detection of its factors. A risk factor is any exposure of a subject that increases the probability of developing a disease or suffering a trauma (WHO, 2013).
The intermittent supply of drinking water by public services has led people to diversify their sources of supply. As a result, households resorted to spring and well water, to the point where it was used as a drink for some, and for various domestic uses. However, don’t the different means used by households in this neighborhood to obtain water present a health threat? The water supply ways of households in Efoulan expose them to health risks.
The development of this article has two sections including: materials and methods, results and discussion. This part will help decipher this issue concerning the exposure of households to health risks. Then, we will open a breach on risk management through a proposal for qualitative and quantitative modeling of health risks that can serve as a reference for public authorities and local populations within the framework of participatory management.
2. Materials and methods
The method used, consisted of carrying out ad hoc studies between 2011 and 2015 as part of exploratory and predictive research. The construction of the sample was based on a stratification method. We conducted a direct survey of representatives of 120 households aged 15 or over in the Efoulan district. The Households’ choice was divided into 6 sections according to the different topographical sites of the concessions (table n ° 1), focused on those who were willing to answer our questions.
Table n°1. Composition of the survey’s sample
|Topographic site of the land||Households|
|Slightly inclined slope||73|
|Very sloping slope||23|
Source : Field data, 2011-2015
2.2. Methods of investigation
The quantitative approach adopted in our research consisted of collecting data on the households surveyed, their methods of access to water and the types of water-related diseases of households in this neighborhood. In addition to this, the aim of this approach was to locate households using GPS and groundwater points in order to model them spatially. This approach made it possible to obtain quantitative data aimed at carrying out descriptive analyzes and statistical tests (explanatory study).
On the other hand, water samples from five wells and three sources were taken during the campaign of December 18, 2015 according to the drinking criterion for a laboratory analysis.
The qualitative approach consisted of conducting direct interviews using guides prepared in advance. This approach also consisted of making direct observations in the field about the water access points.
2.3. Data analysis tools
– the use of QuickBird 2013 satellite images, those of the habitat of the Urban Community of Yaounde, and of the Yaounde guide plan at 1: 10,000 from the National Cartographic Institute to develop basic and thematic maps;
– the application of GIS ArcGis 10.2.2 for geospatial data;
– the ASTER 2007 satellite image, particularly for calculating elevations and slopes;
– the indicators of access to water and those of health risks;
– The variables were selected from the interview guide, entered into the SPSS 18 application for cross-referencing and statistical association tests and link modeling;
– Fischer’s exact non-parametric test to investigate possible links between the origin of drinking water and water-borne diseases, and household water treatment. Next, testing the relationship between the origin of bath water and water-borne diseases, and the treatment of the water. Cross and simply descriptive variables were also represented by the Excel 2010 charts.
– To assess the health risk factors, a bacteriological analysis was carried out by hydrobiologists from the Hydrobiology and Environment Unit (General Biology Laboratory) of the Faculty of Sciences of the University of Yaounde I. Said analysis was carried out on the detection and isolation of bacteria: Fecal Coliforms, Total Coliforms, Escherichia coli species and Fecal Streptococci. For this, the water samples intended for these analyzes were taken at the various study sites (see Figure n ° 1) in vials previously labeled and sterilized at 120 ° C for 15 minutes in an autoclave. The search for germs is carried out within 2 to 4 hours after the samples are taken (Rodier, 2009). Isolation of the bacteria was carried out by the surface spreading or plating technique in 90 mm diameter glass Petri dishes containing the Endo culture media for Fecal Coliforms, Total Coliforms, Fecal Streptococci and Escherichia coli and Bile Esculin Azide (BEA) medium for Fecal Streptococci. Indeed, a 100 μl sample was taken using a sterile pipette and inoculated by the plating technique on the culture media poured into Petri dishes, then incubated at 44 ° C for Fecal Coliforms and at 37 ° C for the others for 24 hours to 48 hours in an oven. After this time, the colonies were identified and enumerated manually. The number of Colonial Forming Units (CFU) is expressed in CFU / 100 ml of water according to the formula:
– Regarding the simulations, the qualitative one focused on an inductive approach called the cause-consequence diagram of well water pollution. A so-called quantitative Monte Carlo simulation on water-borne diseases was carried out using the @Risk 6.1.2 application.
3. Results and discussion
3.1. Impact of water supply on waterborne diseases
The result of the crossing of two qualitative variables, namely the origin of drinking water and water-borne diseases appears in the figure below:
Figure n ° 2. Origin of drinking water and water-borne diseases
An exact Fischer test and a P value of 0.009 at the significance level of 0.05 supported the alternative hypothesis of association of the origin of drinking water with waterborne diseases. Then, testing an association of the two previous variables with that of the water treatment gave us the following result:
- -Fischer’s exact test for households that treat water with a P value of: 0.017 at the threshold of 0.05;
- -Fischer’s exact test for those who do not treat water with a P value of 0.301 at the threshold of 0.05
The effect of crossing said variables is shown in the two figures below:
Figure n ° 3 A. Relationship between the origin of drinking water and water-borne diseases according to the households that treat the water
Figure n ° 3 B. Relationship between the origin of drinking water and water-borne diseases according to households that do not treat water
The result of the test of the two variables, namely the origin of drinking water and the cases of water-borne diseases, shows that one exerts an influence on the other. However, examining the extent of their influence on other variables, among other things, water treatment reveals that the association persists for households that treat water, but disappears for those that do not treat it.
On the other hand, the test for the link between the origin of bath water and water-borne diseases is expressed as follows: Fischer’s exact test with a P value of 0.047. The crossing of these variables is shown in the figure below.
Figure n ° 4. Origin of bath water according to water-borne diseases
The origin of bath water is linked to water-borne diseases in households. However, these two parameters have no connection with the treatment of the water in view of the following result:
- Fischer’s exact test for households dealing with water with a P value of: 0.426 at the threshold of 0.05;
- Fischer’s exact test for those who do not treat water with a P value of 0.301 at the threshold of 0.05
3.2. Types of diseases to which households are exposed
The table below shows the different water-borne diseases to which households are exposed.
Table n ° 2. Diseases declared to be water-borne by households
|Water-borne diseases||Relative frequencies|
|Amebiasis and typhoid||11,7|
|Amebiasis, typhoid and itching||1,7|
Source : Field surveys 2011 – 2015
With regard to water-borne diseases declared by households, the most striking case is that of itching. In fact, body itching is an allergy produced after certain individuals come into contact with unhealthy water, in particular bath water.
3.3 Contaminated groundwater
The table below shows the results of the bacteriological analysis of the various samples.
Table n ° 3. Microbial contamination of groundwater points
|S1||6,5 × 104||1,4 × 104||1,6 × 104||8,12 × 106|
|S2||3 × 103||1,2 × 104||6 × 106||9 × 103|
|S3||2,4 × 104||8 × 103||4 × 106||3 × 103|
|P1||0||1,616 × 105||1,31 × 104||0|
|P2||1,4 × 104||5 × 106||3 × 106||3 × 103|
|P3||0||6 × 103||0||0|
|P4||0||1,1 × 104||2 × 103||0|
|P5||0||5 × 106||1,6 × 104||0|
Source : Collection campaign of 12/18/2015
S1 : Source n°1 ; P1 : Well n°1 ; E. Coli : Escherichia coli ; TC : Total Coliforms ; FC : Fecal Coliforms ; FS : Fecal Streptococci ; 0 : Absence
– Favorable environmental conditions for bacterial propagation
Bacterial risks can have multiple factors:
- Insufficient chemical disinfection: households in general do not control the dosage of bleach or chlorine according to the volume of well water or the depth. The disinfectants used are often not suitable for the water to be treated. Some germs such as faecal streptococci need ozone to be eliminated. In addition, the frequency of disinfection seems random, given that it does not respect a pre-established and fixed schedule. On the other hand, when bleach or chlorine is poured into a well, bacteria firstly go dormant. These bacteria then become active again in the short term. In short, households do not seem to have mastered the challenges of disinfection. The effectiveness of disinfection may also be insufficient with regard to pathogens present inside flocs or particles, which protect them from the action of disinfectants. High turbidity can also protect microorganisms from the effects of disinfection, stimulate the growth of bacteria and trigger a high demand for chlorine.
- The proximity of septic tanks and traditional latrines with a depth similar to that of wells: the actual depth (2 to 4 m) of wells is often close to that of septic tanks and traditional latrines. Indeed, the strong pressure of the building on space has multiplied the presence of septic tanks and traditional latrines communicating with the wells through the water table.
- Rainwater runoff: rainwater flowing down the slopes can easily infiltrate into wells and springs positioned below (case of well n ° 2; photo B).
- The discharge of domestic waste-water promotes pollution of the water table through infiltration.
- Insufficient sanitation measures: the lack of adoption of adequate hygienic rules in the handling of water fetch buckets. In addition, the lack of maintenance of the collection points (source n ° 3) can maintain mold which has a negative impact on health (photos F and H).
- The altimetric and topographical position of the water points (figure n ° 1): well n ° 2 is the most supplied with bacteria because it is located at a very low altitude (656 to 692 m) and on a low slope from 7.95 ° to 11.56 °; therefore very exposed to pollution. The location of sources in hydromorphic (0 to 4.53 °) and very low slope (4.53 ° to 7.95 °) zones. Showers sometimes inundate marshy lowlands causing them to become waterlogged.
- Drainage is facilitated by the lithological nature of the soil: the clay-sandy structure due to its porosity can promote contamination through the drainage of the aquifer.
- The straying of domestic animals: the presence of dogs in certain concessions (wells n ° 1 and n ° 3) or of cats can favor the pollution of the wells through their faeces which can touch the drawing buckets.
3.4. Potential risk management
In a context of decentralization, local authorities would benefit from developing strategies to anticipate or manage health risks or to minimize vulnerability to water. This is a community participatory approach in the management of available water resources, the participants of which would be made up of local authorities, communities and households and possibly other stakeholders. The activities to be developed include, among other things, training and supervision well suited to the needs of the populations.
- Cause-Consequence Diagram Method
The purpose of the cause-consequence diagram method is to describe accident scenarios based on initiating events. It consists of a combination of the Cause Tree and Consequence Tree Methods. The figure below is a cause-consequence diagram of “well water pollution”. “Normal” facts are represented through rectangles while circles represent “abnormal” or degenerative events.
Given a non-arranged well and close to the latrines, the combined action of precipitation and the contact of excreta with the water table leads to the contamination of said water table. The latter promotes the development of faecal microorganisms, in particular faecal streptococci and Escherichia coli which pollute the well water. Untreated polluted water is dangerous for health (water-borne diseases). If this water is treated it can be safe.
Source : Field surveys, 2011-2015
Figure n ° 6. Cause-consequence diagram of “well water pollution”
This is a process to raise awareness on the risks of well water pollution.
- Monte Carlo simulation with the RiskNormal function
The normal distribution (“bell curve”) results in the definition of the mean or probable value and a standard deviation to describe the variation around the mean (Palisade, 2010). Intermediate values close to the mean are the most likely. This is the case of the simulation of the distribution of amebiasis according to households (figure n ° 7).
Figure 7 below is the result of a simulation of 100 iterations of the static value 37 consistent with the number of households affected by amebiasis. Although the possible outcomes are in the range [-∞; + ∞] for normal function, the number of households affected by amebiasis is in the range [28.1; 45.8], the probable outcomes belong to the range [30.79; 42.97] with 90% certainty.
Figure n ° 7. Probabilities’ distribution of amebiasis according to RiskNormal
The dysfunctions in the drinking water supply by the public services have led households to develop numerous strategies for diversifying their sources of supply. Our results showed that the origin of drinking and bath water influenced waterborne diseases in households through statistically significant hypothesis tests. There is also a relationship between households dealing with water and the origin of drinking water. Water-borne diseases reported to be recurrent in households are amebiasis, typhoid and itching. On the other hand, the groundwater which include the wells and the sources consumed by households are practically polluted by bacteria such as Escherichia coli, faecal streptococci, faecal and total coliforms. The pollution cause-consequence diagram and the Monte Carlo simulation illustrate health risk scenarios. This study involves developing and implementing a strategy, a policy for anticipating and managing health risks in a concerted manner at the level of local communities, civil society and local populations. Future research could focus on the risks of the emergence of other water-borne diseases including cholera.
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