QUANTITATIVE ASSESSMENT OF THE RISK RELATED TO THE INGESTION OF METALS DUE TO THE CONSUMPTION OF WELL WATER (IN COTE D'IVOIRE)

in the well water of San Pedro, Daloa and Abidjan.The results indicate that the risk related to the ingestion of arsenic to due the consumption of these waters is 1.75% and 4.2% respectively in the cities of San-Pedro and Abidjan.That is to say ,1750 to 4200 individuals who would probably suffer from cancer out of 100,000 people exposed to the consumption of well water from these study areas. In short, the consumption of well water would constitute a health risk for the consumer. This method of data analysis showed that the populations of the towns of Daloa, San-Pedro and Abidjan ingest lead following the consumption of well water at doses higher than the daily tolerance dose. Out of 100,000 inhabitants, the cities of San Pedro, Daloa and Abidjan respectively 1650, 3370 and 6020 of their population would observe risks related to the ingestion of lead.Similarly, the probability of ingesting arsenic at doses above the daily tolerance dose is 1.75% in San-Pedro and 4.42% in Abidjan. That is to say, out of 100,000 inhabitants, 1700 individuals in San-Pedro and 4200 individuals in Abidjan would be exposed to health problems related to the ingestion of arsenic contained in well water used as drinking water. In sum, the consumption of well water would constitute a health risk for consumers.


ISSN: 2320-5407
Int. J. Adv. Res. 8 (11), 964-971 965 objective of this study is to estimate the levels of health risks to which consumers are exposed as a result of the ingestion of metals contained in well water.

Material and methods:-Presentation of the study area
The assessment of risks related to the ingestion of heavy metals (Pb, Cd and As) due to the consumption of well water discussed in this study focused on well water from seven localities in Ivory Coast. These cities were selected from the main regions : Abidjan (South), Abengourou (South-East), Bouaké (Center), Korhogo (North), Daloa (Center-West), Man (West), and San-Pedro (South-West) (Fig.1).

Investigation
In order to collect information on water sources, the amount of water ingested per person per day, the fréquence of water consumption and the body mass of individuals, a Survey was conducted in the cities selected for the study (Figure 1).To this end, a semi-directive questionnaire was developed based on a qualitative analysis of the population. The survey period ran from December22, 2017 to August 28, 2018.

Sizes of the population to be surveyed
To determine the number of people who participated in the survey, the systematic random sampling technique of (Giezendanner, 2012) was used with the following statistical formula expression. Equation (1) n :minimum size of the persons to be investigated 966 e: margin of error t: margin coefficient deducted from the confidence rate p: proportion of items in the parent population that have a given property Thus, the conventional value of each element of this fraction is as follows: t : 1. 96; p: 0,5 and e: 0. 05.
The number of people selected in each city was proportional to its demographic size (quota sampling). The minimum size of the number of people to be surveyed, using equation 1, is therefore 384. 16. In the case of this study, the size of respondents was extrapolated to 600

Sampling
The sampling campaign was conducted from January 17 to May 28, 2018. A total of 270 well water samples (30 samples for each of the cities of Korhogo, Bouaké, Daloa, Man, Abengourou, San-Pedro and 60 samples for the city of Abidjan) were collected in these different localities.Before the sampling campaign, the labelled material was thoroughly washed, rinsed with distilled water and then washed and rinsed again. The samples were taken using a sump. The water collected was then transferred to polyethylene bottles with a capacity of 1000 mL.The water samples for mineral analysis were acidified with concentrated sulfuric acid at (98%) to obtain a pH ˂ 2.They were then put out of the light in coolers containing ice to maintain the temperatures at 4°C until they reached the laboratory.

Analysis of chemical parameters
Heavy metals were determined by atomic absorption spectrometry (AAS) with an air-acetylene flame, type Varian AA20 according to the Afnor NFT 90-112 standard.

Quantitative risk assessment
Quantitative health risk assessment is a method for estimating by calculation the health risks to a population exposed to contamination of food or water. The assessment of health risks related to the ingestion of lead, arsenic and cadmium from the consumption of well water will follow four main steps (Codex Alimentarius, 2007).

Hazard identification
Hazard identification allows the selection of substances to be taken into account in the quantitative health risk assessment (QHRA) and to identify the effects that can be derived from them. In the case of this study the selected hazards are: arsenic, cadmium and lead.

Hazard characterization
This step consists of establishing the dose response relationship. The purpose of the dose-response relationship is to define a quantitative relationship between the dose administered or absorbed and the incidence of the effect, from which the Toxicological Reference Value (TRV) or Reference Dose (RfD) is established. In this study, the TRV used are those published by the Institut National de l'Environnement et des Risques (INERIS; 2012; 2014). For chronic threshold effects, the ATSDR (Agency for Toxic Substances and Disease Registry).

Exposure assessment
According to the Codex Alimentarius definition, exposure estimation is a quantitative and/or qualitative assessment of the likely absorption of hazards (biological, chemical, physical) from food or water. It consists of quantifying the level of chemicals, microorganisms or toxins in human populations, population subgroups and individuals who are exposed, in terms of magnitude, duration and frequency.In this work, the exposure assessment consisted of determining the quantities of heavy metals (lead, arsenic and cadmium) ingested following the consumption of well water. To define this exposure, the distribution of the quantity of water ingested (Q), the distribution of the concentration of arsenic and lead (C), the distribution of the frequency of water consumption (F) and the distribution

Hazard
Tolerated Daily Dose (TDI) Arsenic 3.10 -4 mg/kg/j. Cardium 2.10 -4 mg/kg/j Plomb 3.6. 10 -3 mg/kg/j. 967 of body weight (P) were determined. These variables were obtained from a survey and chemical analyses. Thus, the exposure estimate was determined according to the following expression : (2) I: daily dose of exposure C: Concentration of metals expressed in mg/kg; Q: Amount of water ingested per day, expressed in mg/day; F : Frequency: water is consumed 7 days/7 days, hence F= 1; P: Body weight of the individual (kg).
Variables C, Q, F and P were sampled by the Bootstrap method. The ingested daily EDI exposure intake of heavy metals as a function of C, Q, F and P was estimated using a Monte Carlo simulation. A total of 1,500 iterations were performed. Each simulation is a numerical calculation corresponding to a possible situation, more or less probable, of a real system. The results of this simulation represent the quantities of heavy metals ingested during the consumption of well water.
Disease risk has been defined as the probability of ingesting the chemical above the Daily Tolerance Dose (DTD). This risk named "R" is defined as being equal to 1-P. This probability "P" is obtained by projecting the DTD of the chemical substance on the function of the cumulative densities described by the different iterations by Monte Carlo simulation. R "Risk": Proportion of the population likely to become ill from water consumption.

Risk Characterization
Integrates the results of hazard identification, characterization and exposure assessment. Based on these results, the risk characterization must quantitatively estimate the severity (that means probability) of the effects.

Statistical analysis
The Excel 2013 analysis utility and Matlab R2015a software were used to analyze the data collected.   Fig.4A, 4B, and 4C describe the probabilities of ingesting a quantity of lead from well water in the cities of Daloa, San Pedro, and Abidjan. The projection of theDaily Tolerance Dose (DTD) on the cumulative functions, indicates that, the probabilities of ingesting lead at doses less than or equal to the Daily Tolerance Dose (DTD) (3.6 10 -3 mg/kg/J) are 93.99% (Abidjan), 96.63% (Daloa) and 98.35% (San -Pedro). Thus, the probabilities of ingesting lead at doses above the DTD are 1.65% (San Pedro), 3.37% (Daloa) and 6.02 % (Abidjan).This shows that, out of 100,000 inhabitants, between 1,650 and 6,020 individuals would be exposed to health problems related to the ingestion of lead contained in well water consumed daily. According to Shaimi et al (2014), lead is a metal that accumulates in various tissues of the body even at low doses. As such, ingestion of lead from well water could expose consumers to health risks. Studies similar to lead exposure conducted by Tanouayi  lead is responsible for abdominal pain, neurological disorders, anemia and high blood pressure in adults. In addition, the Health Canada report (2013) showed that children are particularly susceptible to lead poisoning. The report indicated that lead ingestion in children could lead to anemia, loweredintellectual quotient and neurodevelopmental disorders.  Figure 5 shows the cumulative density functions describing the probability of arsenic ingestion during well water consumption. The DTD projection on the density functions shows that the probabilities of ingesting arsenic at or 970 below the daily tolérance dose (3.10 -4 mg/kg/j) is 95.58 (Abidjan) and 98.25% (San Pedro). On the other hand, the probabilities of ingesting arsenic at doses higher than the daily tolérance dose are 1.75% (San-Pedro) and 4.42% (Abidjan). Per 100.000 inhabitants, the risks of arsenic ingestion following consumption of well water are 1750 (San-Pedro) and 4420 (Abidjan). These functions reveal that the populations of Korhogo, Bouaké, Daloa, Man and Abengourou ingest arsenic at doses below the daily tolérance dose.. However, the populations of the cities of San Pedro and Abidjan ingest amounts of arsenic at doses above the daily tolérance dose The probabilities of ingesting arsenic at doses above the Daily Tolerance Dose are 1.75% in San-Pedro and 4.42% in Abidjan. It is estimated that per 100,000 inhabitants, about 1750 individuals in San-Pedro and 4420 individuals in Abidjan would observe the risk associated with arsenic ingestion. The presence of arsenic in well water could come naturally from the earth's crust as well as from industrial activities such as the manufacture of pesticides, dyes, and metals (Rasheed et al. 2017). Studies similar to the exposure of arsenic were conducted by Rasheed et al. (2017) showed that doses of arsenic in groundwater above the daily tolerance dose.They stressed that populations consuming arsenic at doses above the Daily Tolerance Dose were exposed to health risks. Thus, the populations of the cities of San Pedro and Abidjan who ingest arsenic at doses higher than the Daily Tolerance Dose are also exposed to health risks. According to Rasool et al (2016), arsenic intoxication is manifested by more or less accentuated gastrointestinal disorders, hepatic and renal disorders and cardiovascular manifestations, hypertension and tachycardia.

Conclusion:-
Simulation using the Monte Carlo method made it possible to estimate the health risk related to heavy metals (lead, arsenic and cadmium) following the consumption of well water in seven localities of the Ivory Coast. The analyses carried out revealed the presence of lead and arsenic in the well water consumed by the populations of these towns.

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This method of data analysis showed that the populations of the towns of Daloa, San-Pedro and Abidjan ingest lead following the consumption of well water at doses higher than the daily tolerance dose. Out of 100,000 inhabitants, the cities of San Pedro, Daloa and Abidjan respectively 1650, 3370 and 6020 of their population would observe risks related to the ingestion of lead.Similarly, the probability of ingesting arsenic at doses above the daily tolerance dose is 1.75% in San-Pedro and 4.42% in Abidjan. That is to say, out of 100,000 inhabitants, 1700 individuals in San-Pedro and 4200 individuals in Abidjan would be exposed to health problems related to the ingestion of arsenic contained in well water used as drinking water. In sum, the consumption of well water would constitute a health risk for consumers.