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Human health risk assessment of lead in drinking water: a case study from Port-au-Prince, Haiti

Evens Emmanuel*, Ruth Angerville and Osnick Joseph Laboratoire de Qualité de l'Eau et de l'Environnement, Université QuisqueyaBP 796, Port-au-Prince, Haiti Fax: 509 221 421 1 E-mail: evemml@yahoo.fr E-mail: fsga@uniq.edu *Corresponding author

Yves Perrodin Laboratoire des Sciences de l'Environnement, Ecole Nationale des Travaux Publics de l'Et&, Rue Maurice Audin, 695 18 Vaulx-en-Velin, France

Abstract: In Latin America and the Caribbean (LAC), human intoxication to lead is considered as an important public health issue. In Port-au-Prince, concentrations of lead ranging fiom 40 pg/L to 90 pg/L, greater than the threshold value (10 pg/L) for drinking water, were measured in groundwater and drinking water. This study aims to assess human health risks generated by exposure to lead in the Port-au-Prince water supply. Two sampling campaigns were performed between April2004 and December 2004 on different structures of the public water supply. A significant lead concentration of 250 pg/L, greater than the threshold value, had been detected in a water tank. Risk of deterioration of the psychological development of children exposed to these waters was calculated. These results require monitoring in order to control the human health risk by lead in Port-au-Prince's drinking water.

Keywords: lead; human health, risk; drinking water.

Reference to this paper should be made as follows: Emmanuel, E., Angerville, R., Joseph, 0. and Perrodin, Y. (2007) 'Human health risk assessment of lead in drinking water: a case study fiom Port-au-Prince, Haiti' Znt. J. Environment and Pollution, Vol. 3 1, Nos. 314, pp.280-291.

Biographical notes: Evens Emmanuel is a Professor and Dean of the Faculty of Sciences and Engineering, and the Director of the Laboratory of Water and Environment Quality (LAQUE) of Université Quisqueya in Haiti. He is also the responsible for the Graduate School of Ecotoxicology, Environment and Management of Water. He holds a Master of Sciences in Sanitary Engineering of Universidad San Carlos de Guatemala and a PhD of National Institute of Applied Sciences of Lyon. He is Professor of Water and Wastewater Treatrnent. His research field is methodological approach of human health risk assessment and ecological risk assessment of water and wastewater.

Ruth Ange~il le is an Enviromnental Engineer, and she received Master of Sciences in Ecotoxicology, Environment and Water Management of Quisqueya University (UniQ) in Haiti. She is doing a PhD in the field of ecological risks assessment in the Laboratory of Environmental Sciences (LSE) of the National School of Sîate Public Works of State in France, and in the Laboratory of Water and Environment Quality (LAQUE) of Université Quisqueya in Haiti, under the direction of Professors Yves Perrodin and Evens Emmanuel.

Osnick Joseph is an Environmental Engineer, and he received Master of Sciences in Ecotoxicology, Environment and Water Management of Université Quisqueya in Haiti. He is a PhD student of National Institute of Applied Sciences of Lyon. His working on the use of agricultural by-products, such as sugar cane bagasse, in water and waste water treatment, under the direction of Professors Rémy Gourdon and Evens Emmanuel.

Yves Perrodin is a Professor and Director of the Laboratory of Environmenîal Sciences (LSE) of the National School of State Public Works (ENTPE) in France. Holder of a Master of Sciences in Microbiology and a PhD of National Institute of Applied Sciences of Lyon, his general field of reseach relates to health and ecological nsks assessment of scenarios in wban environment. He assumes responsibilities in several scientific networks intewening on the topic of 'Water and Health'. He teaches the methods of human health and ecological nsks assessment in several French Grande Ecole as well as in universities in developing countries (Haiti, Cameroon).

1 Introduction

The presence of lead in environmental compartments constitutes an ecological and human health concern, since heavy metals are not degraded biologically like organic pollutants (Angerville et al., 2004). Lead particularly targets the nervous system, blood and kidney (INERIS, 2002). Concentrations higher than 10 pgiL in drinking water constitute important public health problems owing to metal absorption and bioaccumulation (Chiron et al., 2003). Indeed, drinking water is one of the major sources of human exposure to lead (INERIS, 2002; Fertmann et al., 2004). A guideline value of 10 pgiL was adopted for drinking water in order to minimise human exposure to lead (OMS, 1996). This new threshold value was also adopted by the European Union in (1998), allowing for transitional regulations until2013 (European Commission, 1998).

Human beings are continuously exposed to lead fiom natural as well as anthropogenic sources (Christensen, 1995). Lead and its inorganic by-products in drinking water (oral exposure) are not carcinogenic (ATSDR, 1999). However, long-term lead exposure may generate irreversible fùnctional and morphological renal changes (Christensen, 1995), distal motor neuropathy and possibly seizures and coma (Robson, 2003). Infants and small children are more sensitive to the effects of lead, which moreover is transported through the placenta to the foetus (Yule and Rutter, 1985; Milman et al., 1988; Shennan and Boyd, 1988; Bellinger et al., 1990; Dietrich et al., 1990; Goyer, 1990; Cleyrnaet et al., 1991; Christensen, 1995). Lead accumulation in foetuses and small children might cause developmental disruption in terms of neurological impairment characterised by a decrease of cognitive faculties, which can be reversible or not, evaluated by psychomotor tests such as the verbal IQ (intellectual quotient) test

(Académie des Sciences, 1998). The period when IQ is most affected is fiom birth to about four years of age (Watt et al., 2000).

In the Americas, lead has been a well-known contaminant for populations exposed to road traffic. During the Miami Sumrnit of 1994, the Presidents of Arnerican and Caribbean countries chose to switch fiom leaded to unleaded gasoline. Information reported on lead characterisation in urban areas of Latin America and the Caribbean (LAC) did not mention the magnitude of the lead intoxication problem in Haiti (OPSIOMS, 1996). However, the fact that rainwater, polluted by atmospheric lead particles originating fiom industrial activities and motor vehicles (Cabrera et al., 1995), feeds the karstic aquifers of Port-au-Prince (Butterlin, 1960; Simonot, 1982; Desreumaux, 1987), therefore leads to the assumption that the groundwater is subject to lead pollution (Denii-Jukii and Jukii, 2003). In addition, significant lead concentrations (up to 1670 pgL) were measured in wastewater discharged by paint factories in Port-au-Prince (Carré, 1997). Lead concentrations ranging fiom 40 pgL to 90 pgL were measured in the dnnking water of Port-au-Prince (Emmanuel et al., 2004). This study aims to evaluate the human health risk caused by chronic exposure to lead fiom Port-au-Prince's public water supply.

2 Theoretical aspects of human health risk assessment

Human health risk assessment is the activity or process that evaluates the effects of a chernical's toxic properties on human beings exposed to it (NRC, 1983). This process is structured in four stages: hazard identification, dose-response assessment, exposure assessment and risk characterisation.

In the fust stage, the known or potential health effects associated with a particular agent are identified. Hazard identification requires the establishment of a causal relation between the appearance of one or several adverse effects on a living organism after its exposure to a chemical substance, according to the scenario (route, intensity, duration) considered within the fiamework of the evaluation (Bonvallot and Dor, 2002). The dose-response relationship, the specific exposure route (oral, dermal or inhalation) and the link between the amount of substance in contact with the organism results in the appearance of the toxic effect (INVS, 2000). The European Commission Guide on Risk Assessment for New and Existing Substances states that the objective of the thud stage, 'exposure assessment', is to predict the concentration profile or dose of a substance to which the receptor will be exposed (European Commission, 1995). For human health exposure assessment this involves evaluating occupational, consumer and environmental exposure. Finally, risk characterisation is a synthesis of the dose-response assessment and the exposure assessment. It consists in linking the data fiom the exposure assessment with the dose-response assessment. If no carcinogenic substances, such as lead in drinking water (ATSDR, 1999), are present, the risk is expressed as a quotient of danger (QD) resulting fiom the ratio 'MDUADI'. This risk ratio is purely qualitative. When the 'D' quotient value is greater than 1, the risk is considered significant, becoming even more so as the quotient increases. Conversely, the lower the quotient is below 1, the weaker the risk.

3 Materials and methods

3.1 Presentation of s t u 4 area

In this human health risk assessment of lead in drinkllig water, an area containing four boreholes, a water tank of 4600 m3 and five domestic water taps were selected in the north of Port-au-Prince as an experimental site (Figure 1). Domestic water taps Cl and C2 were directly connected to the pumping pipe of the four boreholes (upstream of the water tank), while dornestic water taps Dl, D2 and D3 were connected to the water supply network (downstream of the water tank).

Figure 1 Different sampling points ffom borehole and domestic tap water facilities

1 Boreholes k

The boreholes and water tank supply water to a population of over 90,000. Ninety percent of this population were adults and children over five years and 10% were children under five years (IHSI, 2003). Nine thousand people of this estimated population could be considered as children under five years and were thus the most sensitive subgroup to lead intoxication @anks et al., 1997; Bellinger et al., 1987; Needleman and Gatsonis, 1990; Winneke et al., 1990; Goyer, 1996; Académie des Sciences, 1998). The only source of lead exposure considered in this study was the drinking water provided by the public water supply of Port-au-Prince.

Two sampling events were conducted. The first event occurred £rom 16 to 22 April2004 during the rainy season, while the second was conducted £rom 7 to 9 December 2004 during the dry season. Water samples £rom the water tank were collected by a telescopic perch. Conductivity, total dissolved solids (TDS), temperature and pH were measured directly on site after sampling. Al1 water samples for lead characterisation were kept in a 1-L glass flask at 4OC until analysis. Storage conditions of samples were in accordance

with Eaton et al. (1995). Only lead was analysed in the samples collected during December 2004.

3.3 Physicochemical analysis

pH: The pH of collected water samples was measured using a WTW pH 340 ION pH meter fitted with reference and pH electrodes.

Electric ConductiviS, (EC) and Total Dissolved Solids (TDS): EC and TDS were measured on the sampling sites using a WTW-LF 330 multipurpose potentiometer coupled with specific electrodes.

Chlorides (CI): This parameter was determined by the Mohr method, consisting in proportioning chlorides with silver nitrate and potassium chromate. In the presence of silver nitrate (AgN03), Cl ions are mobilised to form cerargyrite. When al1 the chloride ions precipitate as AgC1, silver nitrate reacts with potassium chromate to form a brick red precipitate. Knowing the concentration of AgN03 (Co = 1 O-' M) in 100 ml of solution (E = 100 ml), the volume necessary to obtain equivalence (V,), the concentration of CI ions in the solution is given by the formula: (CI -) = Co x V,/E.

Water samples fiom the fust collection batch were filtered at 0.45 pm and treated with nitric acid (HN03) at pH < 2.0. Lead measurements in pre-treated water samples were camed out by flame atomic absorption spectrophotometry (F-AAS) according to the method described by Eaton et al., (1995). Lead concentrations in the December samples were determined according to the ISO 11 885 protocol (AFNOR, 1999) using ICP-AES (Inductively Coupled Plasma-Atom Emission Spectroscopy) UL,TIMA II fiom Jobin Yvon.

The detection principle of the F-AAS method functions by the absorption of light emitted by a 'lead' lamp. As for the detection principle of ICP-AES, it obtains a spectrum characteristic of lead lines following atomisation in argon plasma. The intensity of these lines is proportional to the quantity of atoms present in solution (AFNOR, 1999).

3.4 Risk characterisation

The risk generated by lead in the drinking water of Port-au-Prince was characterised as a function of equation (l), which expressed the ratio between the exposure assessment (MDI) and the dose-response assessment (ADI):

R: risk MDI: maximum daily intake ADI: dose-response assessment.

For a chemical substance and a given exposure pathway, the general equation for estimating MDI, controlled by exposure vector i, is (INVS, 2000):

MDIi=CixQixERxET/BWxWT (2)

where MD1 (maximum daily intake) is the proportion of substance absorbed per, day of exposure, Ci is the concentration of the toxic substance in the polluted medium i,

Q the quantity of this vector brought into daily contact with the organism by the route considered (expressed in Llday for water media), ER is the exposure rate (without unit), ET is the exposure time (in years), BW is the body weight (in kg) and WT the time of weighing. TP is the duration (in years) over which the amount is weighed. In this formula, by convention, the time of weighing is identical to the exposure time (TW = EW) to reach the threshold: MD1 is close to an annual average without consideration of the total period of exposure.

To estimate the maximum daily intake via drinking water, a normal default assumption is 2 Llday for adults and 0.75 Llday for bottle-fed infants (Fawell and Young, 1999). Body weights (BW) of 70 kg and 5 kg were attnbuted to adults and infants (less than five years), respectively.

To interpret the risk resulting fiom the ratio expressed by equation (l), three levels were considered:

R < 1 L: low

R = l M: medium

R > 1 H: high.

4 Results and discussion

The highest concentrations obtained for the physicochemical characterisation of the 1 samples fiom the two events are summarised in Table 1. In al1 the samples of the two

events (April and December, 2004), pH was always in the allcaline range (7.2C7.83). The values for chlorides were lower than 250 m a . Al1 the results obtained for the pH and chlorides were within acceptable limits for the drinking water guidelines (OMS, 1996).

Table 1 Highest concentrations obtained for selected physiochernical parameters fiom different water sampling points

Sampling Temperature Conductivi~ TDS CT Hardness points pH (OC) (~Slcm) (m&) (m&> ( m m -41 7.83 28.2 960 960 30.49 187 -42 7.26 29.3 1297 1238 27.82 25 1 -43 7.38 29.0 1004 960 23.33 204 A4 7.36 29.0 1089 1069 18.49 218 B 7.31 29.0 1250 1205 31.66 240 ci 7.29 29.6 1178 1122 20.83 234 c2 7.47 28.3 1197 1203 22.99 238 DI 7.40 29.1 1252 1126 21.49 234 D2 7.3 1 29.7 1121 1121 26.33 233 D3 7.44 28.4 1007 1006 19.16 227

The conductivity values indicated high mineralisation of the samples. Al1 the values were higher than 400 pS/cm, Le., the threshold value for drinkllig water (ERB, 1999). The same observation could be made for the values obtained for TDS. Indeed, al1 the TDS concentrations were higher than 500 m a , the value suggested for fiesh water (Desjardins, 1988). Furthermore, a value of 0.9 was obtained for the ratio between

TDS and conductivity. Theoretically, this ratio is an empirical factor that can vary fiom 0.55 to 0.9 depending on the soluble components of the water and on the measurement temperature. Relatively high factors may apply to saline or boiler waters, whereas lower factors may apply where considerable hydroxide or fiee acid is present (Eaton et al., 1995). Since pH in this study varied fiom 7.26 to 7.83, it is obvious that the salinity of the samples studied was very high.

Table 2 shows the variations in lead concentrations fiom the water samples collected in April 2004. Generally, the presence of lead in drinking water can originate fiom industrial discharges, mines and foundries or deterioration of old lead piping (Eaton et al., 1995). Water samples fiom the boreholes for the fust sampling events were lead-fiee, whereas during the same season, high lead concentrations were observed in the water samples fiom domestic taps and tanks. These observations can be explained by different factors. The lead concentrations of these analysed samples could be owing to the existence of equipment, lead piping or joints welded ont0 the network. On the other hand, the values obtained for lead determination using the water samples taken in Apnl 2004 were below the detection limit of the equipment. However, this information does not mean that the groundwater is fiee of lead pollution. The lead detection limit of the equipment (Perkin-Elmer) is 15 pg/L, which is higher than the threshold value (10 pg/L). A human health risk to the consumers of dnnking water fiom points 'C' may exist for any value not detected by the equipment and for which lead concentration would be higher than the threshold value. To ven@ this hypothesis, the presence of lead in water samples taken in December 2004 was determined using ICP-AES whose detection limit is lower than the threshold value (10 pg/L). Table 3 summarises the results obtained for lead fiom water samples collected during December 2004. Variations in lead concentrations between the two sampling events are illustrated in Figure 2.

Table 2 Variation of lead concentrations in April2004 water samples from different sampling points

Samplingpoints Means (pg/L) Minima (pg/L) Maxima (pg/L) S.D. n

Others - - c l 5 - 7

Table 3 Variation of lead concentrations in December 2004 water samples from different sampling points

Samplingpoints Means (pg/L) Minima (pg/L) Maxima (pg/L) S.D. n

Figure 2 Variations in lead concentrations in water samples collected from different sampling points of two campaigns

Sampling points

B a m p l i n g Apnl2004 OSampling December 2004 OThreshold value 1

Lead concentrations in samples collected during the rainy season were found to be higher than the values obtained for samples taken during the ciry season. Since Port-au-Prince does not have an efficient urban waste management system (for liquids and solids), the karstic aquifer facilitates the transfer of surface pollution leachate to groundwater following storms (Deni&-JukiC and Jukik, 2003). However, the presence of lead at lower concentrations in water samples fiom the boreholes is an important indicator of the pollution of groundwater resources. Lead concentrations of water samples fi-om the different components of the public water system take into consideration the human health risk that can be linked to exposure by drinking water supplied by this system. Figure 3 illustrates the distribution of lead in water in the study area.

Figure 3 Schematic distribution of lead in water samples

4.1 Assessrnent of chernical risks of lead in drinking water

Table 4 shows the risk levels to the exposed population on oral ingestion of lead. A high risk can be seen for both adulîs and children. This human health risk assessrnent was determined by calculating a risk quotient specified as a function of the type of risk. In this study it was used to assess neurological impairment and decrease of cognitive faculties or IQ (intellectual quotient) in exposed children (INSERM, 1999).

Table 4 Level of estimated risks for human health f?om lead in drinking water

pb MDl (mglkg da^-') ADI Risk quotient R Level Points ( ~ a ) Adult Children (mglkg x day-') Adult Children Adult Children

B 250 1.10 5.79 0.0035 315 1653 H H

4.2 Estimation of increase of lead concentration in infants' blood

Theoretically, a risk assessment can be camed out with existing data reported in the literature and data obtained fiom analytical characterisation and eco-epidemiological studies. Observation, experiment and modelling constitute the most comrnon methods of performing risk assessrnent (Rivière, 1998). The epidemiological approach used here is the most appropriate tool for characterising human health risk assessment. In this study, although data were obtained only by physicochemical analysis of water samples, available epidemiological data could be used to estimate a decrease in the cognitive faculties of the exposed children of the experimental site.

Indeed, the existing scientific literature on this subject makes it possible to establish a functional 'dose-response' between the level of lead exposure and IQ degradation of the children (Zmirou and Perrodin, 1999). These data indicated that a contribution of +10 pg per day in the drinking water (or food) consumed by the children leads to an increase in the metal concentration in their blood of +16 pgL. In addition, it was also estimated that +100 pg PbiL in the blood of a child can be associated with a decrease of IQ fiom 2% to 3% (INSERM, 1999). Application of these eco-epidemiological data to the case of water collected fiom the water supply network of Port-au-Prince suggested an increase of lead in the children's blood. Table 5 s r n a r i s e s the estimation of the hypothetical decrease in the cognitive faculties (IQ) of children exposed to drinking water in Port-au-Prince.

Table 5 Estimation of hypothetical decrease in cognitive faculties (IQ) of exposed children

Highest Estimation of increase of Estimation of decrease of concen@ation of lead lead concen@ation in infants' infants' IQ (2-3% for

Points ( l a ) blood ( l a ) + 1 O0 l a ) (min max)

The data in columns 3 and 4 (Table 5) were formulated under the assumption of the linearity of the relation between the concentration of the function 'absorbed dose-lead concentrations in blood', and of the linearity of the function 'lead concentrations in blood-effect on IQ'. These assumptions provide a good idea on the possible effects on children's health caused by lead in drinking water. These estimations require backing up by epidemiological studies on the exposed population.

The information obtained was nevertheless sufficient to conclude that there is a considerable risk of deterioration of cognitive faculties in children who regularly consume water from points 'B', 'C2' and 'D3'. These results should be confmed by studies involving a larger sample size.

5 Conclusions

A high risk for both adults and children was calculated from the lead concentration determined in the samples studied. ~ a s e d on these results, this study estimated lead concentration in the blood of exposed children by oral ingestion using data in the literature on the target pollutant. A hypothetical decrease in the cognitive faculties (IQ) of the children exposed to the drinking water of Port-au-Prince was also considered. It would be interesting to reinforce these estimations by canying out epidemiological studies on the exposed population. It is also necessary to characterise lead with a larger number of water samples in order to confim these initial results.

Acknowledgements

The authors would like to acknowledge the AUF (Agence Universitaire de la Francophonie) and the UNESCO office in Haiti for their financial support.

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