FLUORIDE OCCURRENCE IN TAP WATER AT “LOS ALTOS DE ” IN THE CENTRAL REGION 1R. Hurtado, 2J. Gardea-Torresdey, and 2K. J. Tiemann 1Environmental and Engineering Ph. D. Program, Center for Environmental Re- sources Management, The University of Texas at El Paso, 505 W. University Ave, El Paso, TX 79902; Phone: (915) 747-8626; Fax: (905) 747-5145; e-mail: [email protected]. 2Department of Chemistry & Environmental Science and Engineering, The University of Texas at El Paso, 505 W. University Ave, El Paso, TX 79902; Phone: (915) 747-5359; Fax: (905) 747-5748; e-mail: [email protected]. ABSTRACT In Mexico, like most countries in the world, the maximum contaminant level (MCL) of fluoride in drinking water is 1.5 mg/L. The toxic effects of fluorides, other than dental and skeletal fluorosis, include enzyme dam- ages, which result in a wide range of chronic diseases such as genetic damage, premature aging, mental retarda- tion, cancer, bone pathology, and others. In order to characterize the content of fluoride in the drinking water at region, tap water and well water samples from 23 different sites were electrochemically analyzed using the approved U.S. EPA ion-selective method (Method 340.2). Los Altos de Jalisco is located in the Trans-Mexican Volcanic Belt (TMVB), also known as Neo-Volcanic Axes, where the many groundwater wells have been found to have fluoride concentrations over the MCL. Based on the results of this study, the content of fluoride in the water samples ranged from 0.14 to 12.97 mg/L. The cities where we found reticulated water with fluoride concentration over the MCL are Temacapulín (11.25-12.97), Mexticacán-1 (6.64-7.50), (4.77-4.96), Encarnación de Díaz (4.25-4.40), and Tepatitlán-1 (1.83-6.79). While everyone may not be affected, an important fraction of the total population (approximately 200,000) of these cities is under serious health risk and should be of a major concern. Key words: fluoride, fluorosis, fluorite, tap water, Los Altos de Jalisco

INTRODUCTION rainwater, which is stored in surface reservoirs. The Los Altos de Jalisco region, with The mineral content in rivers, lakes, and reser- 16,410 km2 of surface area and a population voirs is mainly due to the discharge of spring over 600,000 people, is located in the north- waters into the main streams. Nevertheless, it is eastern part of the state of Jalisco, Mexico (see possible to find polluted waters from anthropo- Figures 1 and 2). Los Altos de Jalisco is genic sources. The use of groundwater for conformed by 20 counties or municipalities with drinking purposes should be decided after populations ranging from 4,907 to 124,927 chemical characterization, because there are inhabitants. Table 1 shows the surface area and many hydrothermal zones where the mineral its corresponding population for each county in content is over the Mexican national standards. the Los Altos de Jalisco region (INEGI, 1995; Our interest to evaluate the quality of the ITESM, 1995). drinking water in Los Altos de Jalisco is Drinking water, in Los Altos de Jalisco, because the region is located in the Trans- has two origins: (1) surface water, and (2) Mexican Volcanic Belt (TMVB), also known as groundwater wells. In the case of surface water, Neo-Volcanic Axes (Eje Neovolcánico, in the mineral content is low and is mainly due to ). The TMVB is a Pliocene-

Proceedings of the 2000 Conference on Hazardous Waste Research 211 Figure 1. Location of the state of Jalisco in the Figure 2. Location of the Los Altos de country of Mexico. Jalisco region.

Quaternary calc-alkaline province, which theless, most people in the region are consum- crosses Mexico between 19° and 21° N ing bottled water and are cooking food with latitude, and is characterized by hydrothermal boiled water. activity (Campos-Enriquez and Garduño- The highest health risk corresponds to Monroy, 1995). children in the schools, mainly public schools, In the TMVB province, the chemical where they consume considerable amounts of composition of the geological materials indicates tap water directly from the faucets. that groundwater wells might have considerable The objective of this manuscript presenta- amounts of toxic elements, such as copper, tion is the chemical characterization of the tap strontium, zinc, arsenic, lead, chromium, sele- water in Los Altos de Jalisco in order to help in nium, aluminum, and fluoride. the determination of a practical solution for each Our chief concern is that the large amount site where the quality of the water is not satisfy- of people living in Los Altos de Jalisco are ing national and international standards. under high health risk because they are consum- GEOCHEMISTRY OF FLUORIDE ing groundwater without any treatment or Fluorine is found in the environment as support from the water and health agencies. fluorides, mainly because it is the most electrone- However, we found information in the regional gative and reactive of all chemical elements. newspapers where the health authorities mention Practically all natural waters have fluoride, that the people in Los Altos de Jalisco are ranging from trace levels to several dozen consuming safe water. milligrams per liter. Exceptionally higher values The result of our evaluation, which is can be found, such as in the case of some lakes shown below, indicates that several cities are in Kenya where the content of fluoride is over consuming water with levels of fluoride over the 2,000 mg/L (Gaciri and Davies, 1993). The Mexican national standard of 1.5 mg/L. Never-

212 Proceedings of the 2000 Conference on Hazardous Waste Research average concentration of fluoride in seawater is precipitating ions and colloids, solubility of 1-1.3 mg/L; however, rivers, lakes, and ground- fluorine-bearing minerals, anion exchange water generally have concentrations of less than capacity of aquifer materials (OH- for F-), and 0.5 mg/L. In contrast, high fluoride concentra- the size and type of geological formations tions are frequently associated with hydrother- traversed by water are the most important mal waters resulting from volcanic activity and factors controlling the concentration of fluoride fumarolic gases (WHO, 1996). Temperature, in natural waters (Apambire et al., 1997). pH, presence or absence of complexing or

Table 1. Municipality surface and population in Los Altos de Jalisco.

Mmunicipality Surface (k 2))Population (1995

A2catic 366 17,90

A8randas 11,23 70,90

C1añadas de Obregón 477 4,90

C0uquío 848 17,03

E7ncarnación de Díaz 15,29 43,87

J1alostotitlán 478 26,29

J0esús María 567 20,35

L9agos de Moreno 27,84 124,92

M7exticacán 187 7,32

O7juelos de Jalisco 13,31 25,74

S2an Diego de Alejandría 493 6,38

S4an Juan de los Lagos 867 53,36

S8an Julián 206 13,70

S1an Miguel el Alto 571 27,23

T4eocaltiche 941 37,16

T3epatitlán de 10,53 109,30

U8nión de 628 15,17

V6alle de Guadalupe 531 5,66

V1illa 551 13,71

Y1ahualica de González Gallo 592 23,53

T0OTAL 196,41 664,51 Sources: (ITESM, 1995), and (INEGI, 1995)

Proceedings of the 2000 Conference on Hazardous Waste Research 213 Some of the minerals where fluoride can fluorapatite, (Ca10(PO4)6F2, is incorporated in be found in significant fractions are fluorite the enamel in place of the hydroxyapatite.

(CaF2), apatite, villiaumite (NaF), cryolite (Na3 Fluorapatite is less soluble in mouth acids;

Al F6), topaz (Al2SiO4 (F,OH)3), mica, amphib- hence fluoride-containing teeth are less suscep- oles, and rock phosphate. The mineral that tible to decay. predominantly determines the concentration of After the WHO recommendation, an fluoride found in natural waters is fluorite. important number of countries legislated to set

Solubility product (kSP) of fluorite, at 20 °C, is 1.5 mg/L as the maximum contaminant level 3.9 x 10-11. This low solubility value implicates (MCL) for fluoride in drinking waters. Never- that waters with low content of calcium should theless, the USEPA, after an evaluation by the have high fluoride concentration. National Research Council (NRC, 1993), kept The apatite group plays an important role 4.0 mg/L of fluoride as MCL or primary in determining the level of toxicity of waters due standard for drinking water and 2.0 mg/L as to the additional dissolution of elements such as MCLG (maximum contaminant level goal) or arsenic and lead. The general formula of the secondary standard. Instead of a health apatite group is problem, the USEPA considers mild dental A()( BO OH,F,Cl ) 543 fluorosis as an aesthetical one. where An important number of epidemiological A= Ca, Ba, Na, Pb, Sr, La, and Ce studies have shown possible adverse effects of B= P, V, and As the long-term ingestion of fluoride. Concentra-

BO4 = CO3 and SiO4 tions above the MCL value carry an increasing One important member of this group is risk of dental fluorosis, and much higher con-

fluorapatite, Ca10(PO4)6F2. centrations lead to skeletal fluorosis, bone HEALTH EFFECTS cancer, premature aging, mental retardation, and There is a big controversy on the useful- other health concerns. ness of fluoride in protecting tooth decay. In In several districts of Rajasthan, , the 1984, the World Health Organization (WHO) population is consuming water with fluoride recommended keeping the concentration of concentration up to 44 mg/L. Permanent fluoride in the range of 0.5 to 1.5 mg/L (WHO, deformities, joints pains, general debility, and 1996) in order to prevent dental caries, espe- misery has been the consequence of consuming cially in children. The ingestion of low doses of water with such high mentioned levels of fluoride fluoride could protect tooth enamel from disso- (Agarwal et al., 1999). lution. Tooth enamel consists of hydroxyapatite Endemic fluorosis has been reported in several regions of Mexico, where people are (Ca10(PO4)6(OH)2). If a reasonable level of fluoride ion is present in the diet during the consuming water with fluoride contents over the growing phase of teeth, a significant amount of MCL of 1.5 mg/L, which is the Mexican

214 Proceedings of the 2000 Conference on Hazardous Waste Research national standard for drinking water. Not only tap water, but also bottled waters with fluoride ranges between 0.33 to 6.97 mg/L were found in the city of San Luis Potosi, Mexico (Grimaldo et al., 1995). Similar values, between 0.7 and 5.6 mg/L, were detected in the city of , Mexico (Ortiz et al., 1998). In both cities, San Luis Potosi and Durango, the health risk is higher than normal because the intake of fluoride Figure 3. Calibration curve for determination of fluoride in tap waters. comes not only by drinking water with high levels of fluoride, but also by eating food METHOD OF ANALYSIS cooked with boiled water. Fluoride concentrations were determined In 1996, the WHO concluded that, in electrochemically, using the approved USEPA setting national standards for fluoride, it is ion-selective method (Method 340.2). This important to consider climatic conditions, water method is applicable to the measurement of intake, and intake of fluoride from other sources fluoride in drinking water, surface and saline such as food and air (WHO, 1996). In tropical waters, and domestic and industrial wastes in a countries, where people consume considerable range of concentration from 0.1 up to 1000 mg/ amounts of water, the health risk is higher. In L (USEPA, 1991). A detailed explanation of addition, high levels of fluoride in the air have this analytical method has been reported before been reported in some regions of China from (G. Rum et. al., 2000). The electrode used was the combustion of high fluoride-bearing coal a Fluoride/Combination Fluoride Electrode – (Wang et al., 1999). Therefore it is important to Orion 96-09, which was coupled to an Orion understand the total possible exposure to fluoride 420A Electrometer (pH meter). Standards were before assessing the potential public health risk. prepared from a stock solution (100 mg/L) of sodium fluoride. Figure 3 shows the calibration EXPERIMENTAL curve prepared from the measurement of the Sampling potential (mV) of five standard solutions (0.1, Tap water samples were collected in clean 1.0, 5.0, 10.0 and 20 mg/L) where the R2 value fluoride-free plastic bottles, directly from home was 0.9968. Three replicates of each sample faucets in Los Altos de Jalisco. Trace-grade were analyzed and the average is reported herein. nitric acid was added in order to preserve the RESULTS AND DISCUSSION samples for future ICP-MS analysis. The The total number of sites where water samples were then stored at approximately 5 samples were collected was 23; one corre- °C. The same procedure was used for the one sponds to a river sample (Rio Verde river); river sample obtained.

Proceedings of the 2000 Conference on Hazardous Waste Research 215 three correspond to samples directly collected Mexican national standard of 1.5 mg/L. This from well bore (Cañadas-2, Mezcala-1, and river is considered important since it is feeding Jalostotitlán); and 19 were tap water, collected the Rio Grande de that drains into the directly from home faucets. Tepatitlán de Chapala Lake. The city of , one of Morelos was the municipality where the highest the most important cities of Mexico, consumes number of samples was taken (six samples, water directly from the Chapala Lake Reservoir. corresponding to three different cities). The With the exception of Temacapulín, the Cañadas de Obregón municipality was where levels of fluoride found in the remaining five the highest concentration of fluoride was found, cities of Los Altos de Jalisco (mentioned which consisted of four samples and one river above) are very similar to the values reported sample. The sample from Temacapulín (a small by Grimaldo et al. (1995) in San Luis Potosi, village with a population of around 400 and by Ortiz et al. (1998) in Durango, México. people) had the greatest fluoride concentration Although there is no data on the percentage of of 12.97 mg/L. people (at Los Altos de Jalisco) who prepare Table 2 shows the fluoride concentration their food with boiled water, representing an of each site sampled across the Los Altos de additional risk factor for human exposure to Jalisco region. The fluoride content in the fluoride, we can assume that these are similar to water samples ranged from 0.14 to 12.97 mg/L. the values reported by Ortiz, et al. (1998), These values indicate not only the differences in which is approximately 90% of the population. the source of water (surface or groundwater) This is due to the similarities in and used in the region, but also different mineralogi- culinary costumes. However, one important cal characteristics in the geological structures of difference between Los Altos de Jalisco and the area. San Luis Potosi and Durango is that the ambient The cities where fluoride concentrations temperature of Los Altos de Jalisco is lower were found to be over the MCL are than both cities. This would imply that the intake Temacapulín (11.25-12.97 mg/L), Mexticacán- of fluoride could be less at Los Altos de Jalisco. 1 (6.64-7.50 mg/L), Lagos de Moreno (4.77- CONCLUSIONS 4.96 mg/L), Encarnación de Díaz (4.25-4.40 After obtaining samples from approxi- mg/L), and Tepatitlán-1 (1.83-6.79 mg/L). The mately 12,000 km2, 74% of the Los Altos de total population of these cities is around Jalisco region, we found five cities and one 200,000 people. While the entire population is river containing water with fluoride concentra- not at risk, a large portion of this population is tions in the range of 1.83 to 12.97 mg/L (all exposed to a serious potential health risk and over the Mexican national standards). should be of a major concern. In the case of some cities where there are The fluoride concentration of the Rio wells with different concentrations of fluoride Verde River (1.94-3.05 mg/L) was over the

216 Proceedings of the 2000 Conference on Hazardous Waste Research Table 2. Fluoride content (mg/L) of water samples at Los Altos de Jalisco.

M9unicipality J9un-9 A9ug-9 N0ov-9 Feb-0

Arandas

(——5Arandas) 04.2 0.1

(———9Santa María del Valle) * 0.2

Cañadas de Obregón

(7Temacapulín) ** 152.9 121.2 191.4 12.2

(0Rio Verde) 24.5 15.9 34.0 2.8

(5Cañadas-1) * 08.2 04.2 05.4 0.2

(——8Cañadas-2) * 09.6 0.2

C———5uquío * 0.2

E——5ncarnación de Díaz * 40.2 4.4

J——3alostotitlán * 10.2 1.1

L——7agos de Moreno * 46.7 4.9

Mexticacán

(——0Mexticacán-1) * 74.5 6.6

(———3Mexticacán-2) * 6.3

S——5an Diego de Alejandría * 00.5 0.8

S——4an Juan de los Lagos 09.6 0.7

S——9an Julián * 07.4 0.4

S——4an Miguel el Alto 15.0 0.6

T——8eocaltiche 15.1 1.1

Tepatitlán de Morelos

(1Mezcala-1) * 00.5 0——.4

(7Mezcala-2) 04.1 0——.2

(——6Capilla de Guadalupe) 03.3 0.2

(5Tepatitlán-1) 04.1 0-.2 Ñ-Ñ

(3Tepatitlán-2) * 23.2 19.8 65.7 6.7

(——4Tepatitlán-3) * 03.6 0.2 * from groundwater well; ** from spring; others from surface reservoir

Proceedings of the 2000 Conference on Hazardous Waste Research 217 (such as in Tepatitlán), we recommend one of REFERENCES the following alternatives: (a) close wells that are Agarwal, K.C., S.K. Gupta, and A.B. Gupta, 1999. Development of new, low-cost delivering water with fluoride concentration over defluoridation technology (KRASS), the MCL; (b) mix the water of two or more Water Sci. Tech., 40-2, pp. 167-173. wells in order to deliver water within national Apambire, W. B., D. R. Boyle, and F. A. Michel, standards or; (c) use water wells with fluoride 1997. Geochemistry, genesis, and health content over the MCL for other applications, implications of fluoriferous groundwater in such as irrigation of public green areas. the upper regions of Ghana, Environ. Geol., 33-1, pp. 13- 24. In small towns and villages, such as Mexticacán and Temacapulín, where the popu- Campos-Enriquez, J.O., and V.H. Garduño- Monroy, 1995. Los Azufres silicic center lation is relatively low, we have to work for the (México): inference of caldera structural development and/or implementation of non- elements from gravity, aeromagnetic, and sophisticated methods of fluoride removal. An geoelectric data, J. Volcanol. Geoth. additional program of environmental Res., 67, pp. 123-152. needs to be developed. Ferrari, L., S. Conticelli, G. Vaggelli, C. M. A more complete sampling program will Petrone, and P. Manetti, 2000. Late Miocene volcanism and intra-arc be performed in order to have a better evalua- tectonics during the early development tion that will allow recommendations for specific of the Trans-Mexican Volcanic Belt, and practical methods of fluoride control for Tectonophysics, 318, pp. 161-185. each site. Nevertheless, our attention will be Gaciri, S. J., and T. C. Davies, 1993. The focused on the higher population cities, such as occurrence and geochemistry of fluoride Lagos de Moreno, Tepatitlán, and Encarnación in some natural waters in Kenya, J. Hydrol., 143, pp. 395-412. de Díaz, where we are planning a more intensive program of sampling and evaluation. Grimaldo, M., V.H. Borja-Aburto, A.L. Ramírez, M. Ponce, M. Rosas, and F. ACKNOWLEDGEMENTS Díaz-Barriga, 1995. Endemic fluorosis The authors would like to acknowledge in San Luis Potosi, Mexico: I. Identifi- cation of risk factors associated with support from the Environmental Protection human exposure to fluoride, Environ. Agency, the Center for Environmental Resource Res., 68, pp. 25-30. Management of the University of Texas at El INEGI (Instituto Nacional de Estadística, Paso, and Autotransportes Mezcala, S.A. Also, Geografía e Informática), 1995. 1995 we want to acknowledge the information and INEGI count of population and housing. comments from Dr. Sánchez Cavazos, a prac- ITESM (Instituto Tecnológico y de Estudios ticing family doctor in Tepatitlán, Jalisco. Superiores de , Campus

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Proceedings of the 2000 Conference on Hazardous Waste Research 219