Investigación original / Original research
Arsenic in drinking water in the Los Altos de Jalisco region of Mexico
Roberto Hurtado-Jiménez1 and Jorge L. Gardea-Torresdey 2
Suggested citation Hurtado-Jiménez R, Gardea-Torresdey JL. Arsenic in drinking water in the Los Altos de Jalisco region of Mexico. Rev Panam Salud Publica. 2006;20(4):236–47.
ABSTRACT Objective. To establish the degree of contamination by arsenic in drinking water in the Los Altos de Jalisco (LAJ) region of west-central Mexico, and to estimate the levels of exposure that residents of the area face. Methods. Total arsenic concentration (the sum of all arsenic forms, organic and inorganic) was determined for 129 public water wells in 17 municipal capitals (cabeceras municipales) of the LAJ region, using inductively coupled plasma-optical emission spectroscopy. For most of the wells, water samples were taken in both November 2002 and October 2003. The levels of exposure to arsenic were estimated for babies (10 kg), children (20 kg), and adults (70 kg). Results. Mean concentrations of arsenic higher than the Mexican national guideline value of 25 μg/L were found in 44 (34%) of the 129 wells. The mean concentration of total arsenic for the 129 wells ranged from 14.7 μg/L to 101.9 μg/L. The highest concentrations were found in well water samples collected in the cities of Mexticacán (262.9 μg/L), Teocaltiche (157.7 μg/L), and San Juan de los Lagos (113.8 μg/L). Considering the global mean concentration for all the wells in each of the 17 cities, the mean concentration of arsenic exceeded the Mexican guideline value in 7 of the cities. However, the global mean concentration in all 17 cities was higher than the World Health Organization guideline value of 10 µg/L for arsenic. The range of the estimated exposure doses to arsenic in drinking water was 1.1–7.6 μg/kg/d for babies, 0.7–5.1 μg/kg/d for children, and 0.4–2.7 μg/kg/d for adults. Conclusions. At the exposure doses estimated in the LAJ region, the potential health effects from chronic arsenic ingestion include skin diseases, gastrointestinal effects, neurological dam- age, cardiovascular problems, and hematological effects. While all the residents may not be af- fected, an important fraction of the total population of the LAJ region is under potential health risk due to the ingestion of high levels of arsenic. Epidemiological studies to determine the ar- senic levels in the blood, hair, and nails of humans should be conducted in the LAJ region to help assess the relationship between the prevalence of health problems and the chronic inges- tion of arsenic.
Key words Arsenic, water supply, water pollutants, Mexico.
1 El Colegio de la Frontera Norte, A.C., Ciudad The Los Altos de Jalisco (Highlands population around 665 000 inhabi- Juárez, Chihuahua, México. Send correspondence 2 to: Roberto Hurtado-Jiménez, Ave. Insurgentes No. of Jalisco) region is made up of a tants, and has an area of 165440.69 km 3708, Fracc. Los Nogales, CP 32350, Ciudad Juárez, group of 20 municipalities (municipios) (1). The LAJ region belongs to the Chihuahua, México; telephone: 52 656 6168578; fax: 52 656 6169214; e-mail: [email protected] located in the northeastern part of Trans-Mexican Volcanic Belt, an active 2 University of Texas at El Paso, Department of Jalisco, a state located in west-central volcanic area that exhibits intense hy- Chemistry and the Environmental Science and Engi- neering Ph.D. Program, University of Texas at El Mexico (Figure 1 and Figure 2). The drothermal activity, as evidenced by Paso, El Paso, Texas 79925, United States of America. Los Altos de Jalisco (LAJ) region has a hot springs, fumaroles, and geysers.
236 Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico Original research
FIGURE 1. Location of the state of Jalisco, the Los Altos de Jalisco region, and the Trans- Consequently, underground aquifers Mexican Volcanic Belt in Mexico located in the Trans-Mexican Volcanic Belt have a high probability of being N contaminated with toxic elements (2, 3). It is well known that thermal waters contain high levels of heavy metals W E and trace elements. One of these ele- ments is arsenic, whose toxicity has been recognized since ancient times. S Arsenic is a naturally occurring Los Altos de Jalisco chemical element that is widely dis- Trans-Mexican Volcanic Belt tributed in the earth’s crust. It occurs in several forms, often combined with other chemical elements. When arsenic is combined with oxygen, chlorine, and sulfur, it is known as inorganic JALISCO arsenic. Arsenic combines with carbon and hydrogen to form organic arsenic compounds. In general, inorganic ar- senic is more dangerous than is or- ganic arsenic (4). Inorganic arsenic pre- 05001 000 1 500 2 000 2 500 kilometers dominates in underground aquifers. Arsenic minerals can be found in a variety of geological environments, in- cluding igneous, sedimentary, and metamorphic rocks (5). Many arsenic minerals may be found at trace levels in practically all living matter (6). FIGURE 2. Location of municipalities in the Los Altos de Jalisco region of Mexicoa Other sources of arsenic include vol- canic gases and geothermal waters (7). The arsenic concentrations in nat- ural waters around the world range from < 0.5 to 5 000 μg/L. However, the 10 typical concentrations in most coun- μ N tries are of less than 10 g/L, and 19 sometimes substantially lower (less 5 1. Acatic than 1 μg/L) (8). High arsenic concen- 2. Arandas W E 15 8 3. Cañadas de Obregón trations occur in a variety of environ- 4. Cuquío ments, including both oxidizing (high 5. Encarnación de Díaz pH) and reducing aquifers (9). 6. Jalostotitlán S 9 12 7. Jesús María Arsenic contamination of drinking 6 8. Lagos de Moreno water supplies can result from natural 17 20 3 9. Mexticacán or artificial processes. Natural con- 10. Ojuelos de Jalisco tamination generally comes mainly from 18 13 11. San Diego de Alejandría 14 10 12. San Juan de los Lagos mineral deposits or geothermal fluids. 4 13. San Julián The main sources of artificial or anthro- 14. San Miguel el Alto pogenic contamination are usually as- 16 15. Teocaltiche 16. Tepatitlán de Morelos sociated with industrial applications 1 2 17. Unión de San Antonio such as wood preservation, petroleum 18. Valle de Guadalupe refining, semiconductor manufactur- 7 19. Villa Hidalgo 20. Yahualica de González ing, production of nonferrous alloys Gallo (principally lead alloys used in lead- acid batteries), burning of fossil fuels 0 50 100 150 200 kilometers (especially coal), metal production (such as gold), agricultural applications a In this study, chemical analyses for three municipal capitals (Cañadas de Obregón (3), Cuquío (4), and Yahualica de Gon- (pesticides and feed additives), and irri- zález Gallo (20)) were not performed because their water supply comes only from surface water. gation with polluted waters (4, 10–12).
Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 237 Original research Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico
Mexico’s current national guideline vomiting, and diarrhea), neurological ating conditions, that is, delivering value for arsenic in water delivered to damage, cardiovascular problems water to the public water system. Sam- the public water system was recently (high blood pressure, heart attack, and ples were taken manually from the set at 25 μg/L (13). In 1993 the World stroke), various types of cancer (skin, wellhead sampling port of each well. Health Organization (WHO) set 10 μg/L bladder, lung, kidney, and other or- Before the sampling, a bottle was rinsed as the guideline value for arsenic in gans), and respiratory, pulmonary, three times with water from the same drinking water (14). In the United hematological, hepatic, renal, develop- well. In order to get a representative States of America the current standard, mental, reproductive, immunological, sample (free of any contamination from or maximum contaminant level, for genotoxic, and mutagenetic effects the pipe line), the sampling port was arsenic in drinking water is 50 μg/L, (4, 9, 16, 21). first purged for several minutes. Water which was set in 1975. Nevertheless, a The three aims of this study were: (1) samples were preserved by adding new standard (10 μg/L) was promul- to determine the levels of arsenic in the trace-grade nitric acid. The samples gated in 2001 by the Environmental public water wells located in the LAJ were then stored at approximately 5 °C. Protection Agency (EPA) of the United municipal capitals (cabeceras munici- Two series of water samples were States. Water systems were supposed pales), (2) to report the distribution of taken. The first series was collected to start complying with the new EPA arsenic in the groundwaters in the re- during November 2002, and the sec- standard by January 2006 (15). gion, and (3) to estimate the levels of ond in October 2003. Three water sam- The occurrence of arsenic in drink- the arsenic exposure via drinking water ples per well were taken during each ing waters has been reported in vari- that residents of the LAJ region face. series. ous countries, including Argentina, (The municipal capital is the city or Austria, Bangladesh, Chile, China, town where the municipality’s admin- Ghana, Greece, Hungary, India, Mex- istrative offices are located. In general, Analytical ico, Romania, South Africa, Taiwan, the city or town with the largest popu- Thailand, and the United States (16). lation among the communities in the The total arsenic concentration in In Mexico there are several areas municipality is the municipal capital. the water samples was determined by where high levels of arsenic in ground- The municipality and the municipal inductively coupled plasma-optical water have been reported. The four capital usually have the same name.) emission spectroscopy (ICP-OES). The most important areas are: (1) Comarca instrument used was an Optima 4300 Lagunera (a region of 15 municipalities DV ICP-OES (PerkinElmer, Shelton, located in the north-central part of MATERIALS AND METHODS Connecticut, United States). The corre- Mexico, 5 in the state of Coahuila and lation coefficients for the wavelengths 10 in the state of Durango), where the Sampling used (188.979 and 197.197 nm) were in total arsenic concentration (the sum the range of 0.9970 to 0.9999. of all arsenic forms, organic or inor- In order to determine the level of ar- Temperature, pH, and conductivity ganic) in well waters has ranged from senic in the groundwater aquifers lo- were determined by using selective 7 to 740 μg/L (17); (2) Valle del Gua- cated in the LAJ region, water samples electrodes. diana (located in the state of Durango, were collected from 129 public wells in in the north-central part of Mexico), 17 of the LAJ region’s 20 municipal with arsenic concentrations in the capitals. In this study, arsenic concen- Data analysis range of 5 to 167 μg/L (18); (3) Valle de trations were determined in ground- Zimapán (in the state of Hidalgo, in water samples only. There are three Statistical analysis was performed to central Mexico), where the concentra- LAJ municipal capitals (Cañadas de obtain the arithmetical mean and stan- tion of arsenic in 32 groundwater sam- Obregón, Cuquío, and Yahualica de dard deviation for each of the physi- ples has ranged from 14 to 1 097 μg/L González Gallo) where surface water cal and chemical properties measured (the highest value was found in the is the only source of water, and so we in this study. A standard spreadsheet water pumped from one of the most did not take samples in those three lo- was used to calculate those statistical productive wells) (19); and (4) the city cations. (A preliminary study carried values. The distribution of arsenic in of Hermosillo (in the state of Sonora, in out by the authors (not published) the groundwaters of the study area northern Mexico), with arsenic concen- showed that the levels of arsenic were was presented graphically by using a trations up to 305 μg/L (20). lower than 1 μg/L in those three geographic information system. The It is well known that chronic expo- cities.) These 129 wells represent ap- average concentrations of arsenic for sure to high levels of arsenic causes a proximately 81% of the total number each of the municipal capitals were as- wide variety of serious human health of wells that are supplying water to signed to polygon coverage of the mu- problems. These problems include those 17 communities. nicipality boundaries. In addition, a dermal changes (pigmentation, hyper- The water samples were collected in pie graph has been used to show the keratosis, and ulceration), gastroin- prewashed polyethylene bottles from percentage distribution of the water testinal effects (stomach pain, nausea, public water wells under normal oper- wells according to the level of arsenic.
238 Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico Original research
Exposure levels daily exposure doses to arsenic) for tivity (EC) for the wells in each of the 17 persons living in the LAJ region. In municipal capitals is given in Table 1. The daily exposure doses to arsenic this study, three groups of people In addition, a visual presentation of the in drinking water were estimated by were arbitrary selected: babies (12 arithmetic mean, minimum value, and using this equation: months old and weighing 10 kg), chil- maximum value of the arsenic levels of dren (6 years old and weighing 20 kg), the wells in each of the 17 municipal
ED = IWater/WBody and adults (25 years old and weighing capitals is given in Figure 3. 70 kg). Calculations were based on the The mean total arsenic concentra- where following assumptions: (1) the babies’ tions in the 17 LAJ municipal capitals ED = daily exposure dose to arsenic daily diet included a food formula pre- ranged from 14.7 μg/L (city of Aran- in drinking water, in μg/d/kg pared with 750 mL of tap water, (2) the das) to 101.9 μg/L (city of Mexticacán).
IWater = daily intake of arsenic from children’s daily diet included 1 000 mL While all of the 17 municipal capitals drinking water, in μg/d of tap water, and (3) the adults’ daily had a mean concentration of total ar- μ WBody = individual body weight, in kg diet included 1 850 mL of tap water. (A senic higher than 10 g/L (the guide- previous publication (22) had sug- line value set by the WHO), only 7 of Daily intake of arsenic from drink- gested using these values to estimate them exceeded the Mexican national ing water was calculated by using the the levels of exposure to fluoride in the guideline value for arsenic of 25 μg/L. next equation: LAJ region.) We estimated the mean, These cities were Encarnación de Díaz, minimum, and maximum daily expo- Mexticacán, Ojuelos de Jalisco, San
IWater = CWater IRWater sure doses to arsenic by using, respec- Juan de los Lagos, San Miguel el Alto, tively, the mean, minimum, and maxi- Teocaltiche, and Valle de Guadalupe. where mum concentrations of total arsenic in With the exception of San Miguel el
CWater = total arsenic concentration in drinking water that we had found Alto, the other 6 cities had a mean drinking water, in μg/L from our sampling of the wells. well-water temperature higher than
IRWater= water intake rate via inges- 30 °C, indicating origin or contamina- tion, in L/d tion from deeper geothermal waters. RESULTS Even though the mean temperature of A simulation process was devel- the wells in the cities of Acatic, Lagos oped to estimate the levels of exposure The information on arsenic levels, de Moreno, and Tepatitlán de Morelos to arsenic (daily intake of arsenic and temperature, pH, and electric conduc- was greater than 30 °C, the mean ar-
TABLE 1. Data on water wells, including temperature, pH, electric conductivity (EC), and total arsenic concentration, in municipal capitals in the Los Altos de Jalisco region of Mexico, 2002–2003
μ μ No. of Temperature (°C) pH EC ( S/cm) Arsenic ( g/L) Municipal capital Populationa wells Mean Minb Maxc Mean Min Max Mean Min Max Mean Min Max
Acatic 11 005 4 32.4 31.2 33.7 6.7 6.5 7.0 252 182 297 16.5 5.1 30.8 Arandas 39 478 11 28.0 23.3 32.8 6.5 6.2 6.7 279 230 408 14.7 3.8 26.1 Encarnación de Díaz 20 772 6 30.1 25.8 36.6 7.1 7.0 7.4 537 451 661 25.2 17.9 42.8 Jalostotitlán 21 291 5 26.8 24.7 29.3 7.0 6.8 7.0 459 417 494 23.4 18.1 29.8 Jesœs María 7 852 4 27.3 24.1 31.3 6.5 6.5 6.7 413 206 421 22.8 4.0 52.6 Lagos de Moreno 79 592 18 30.2 22.2 35.2 7.0 6.5 7.5 556 395 1 084 21.8 10.8 43.3 Mexticacán 3 603 4 30.3 26.6 37.7 7.2 7.1 7.3 563 489 691 101.9 12.9 262.9 Ojuelos de Jalisco 9 338 3 37.5 36.4 38.7 6.9 6.9 7.0 548 548 548 28.3 20.5 33.9 San Diego de Alejandría 4 749 2 27.5 27.4 27.7 7.4 7.3 7.5 475 434 517 20.7 4.8 52.2 San Juan de los Lagos 42 411 11 32.2 26.7 45.2 7.1 6.9 7.5 830 474 1 888 54.5 0.5 113.8 San Julián 12 117 3 26.2 25.1 27.3 7.0 6.8 7.1 452 439 467 20.3 8.6 62.0 San Miguel el Alto 21 098 6 25.7 22.6 28.7 7.2 7.0 7.3 553 347 922 30.8 5.8 74.8 Teocaltiche 21 518 5 30.6 26.2 33.9 6.8 6.6 7.2 796 620 1 074 89.5 54.0 157.7 Tepatitlán de Morelos 74 262 27 30.9 24.0 42.3 6.7 5.9 8.0 310 177 576 22.1 4.5 74.0 Unión de San Antonio 6 317 3 26.8 24.6 30.2 7.2 7.0 7.4 429 427 431 20.0 6.1 31.8 Valle de Guadalupe 4 178 4 35.0 33.9 36.8 7.0 6.8 7.3 479 375 548 28.2 16.5 47.0 Villa Hidalgo 11 552 13 28.5 25.7 32.4 6.3 6.0 7.2 171 155 204 16.3 4.0 36.5 Total/Overall 391 133 129 29.9 22.2 45.2 6.8 5.9 8.0 447.1 155 1 888 29.4 0.5 262.9 a The population data for the municipal capitals are from the Instituto Nacional de Estadística, Geografía e Informática (1). b Min = minimum. c Max = maximum.
Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 239 Original research Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico
FIGURE 3. Arsenic levels, with minimum, mean, and maximum, in water values were found in Lagos de wells in the municipal capitals of the Los Altos de Jalisco region of Mex- Moreno (Well O, 1 084 μS/cm) and in a ico, 2002–2003 Teocaltiche (Well No. 5, 1 074 μS/cm). In general, there was a positive corre- Arandas lation between arsenic concentration Villa Hidalgo and conductivity. The pH of the water wells tested ranged from 5.9 to 8.0. Acatic Table 3 shows the number of water Minimum Unión de San Antonio wells tested in each of the municipal Mean capitals and the number and percent- San Julián Maximum age of the wells in each capital that San Diego de Alejandría met the international WHO guideline value for arsenic (10 μg/L) and the Lagos de Moreno Mexican national guideline value (25 μg/L). While 85 of the 129 water wells Tepatitlán de Morelos sampled (66%) met the Mexican na- Jesús María tional guideline value, only 10 wells (8%) met the WHO guideline value.
Jalostotitlán The data from Table 3 also show that: Encarnación de Díaz (a) there were 3 cities where 100% of the sampled wells had a total mean ar- Valle de Guadalupe senic concentration greater than 25 μ Ojuelos de Jalisco g/L, (b) there were 13 cities where at least one well had a total arsenic con- San Miguel el Alto centration greater than 25 μg/L, and San Juan de los Lagos (c) there were 4 cities where 100% of the sampled water wells met the na- Teocaltiche tional guideline value. Graphic depic- tions of the distributions of the values Mexticacán for the arsenic concentration for the 0 25 50 75 100 125 150 175 200 225 250 275 129 wells are given in Figure 4, Figure Arsenic concentration, μg/L 5, and Figure 6. Figure 7 shows the distribution of a The municipal capitals are ordered by the mean arsenic concentration. the mean arsenic concentrations in the groundwaters in the LAJ region. The range into which the mean concentra- tion of arsenic in each of the municipal capitals falls is represented by the in- senic concentrations for each of those dents of the LAJ region could be facing tensity of the shading. The three white three cities was lower than 25 μg/L. some potential health risks. areas correspond to the municipal cap- The total population of the 7 cities that Of the 129 wells sampled in the 17 itals of Cañadas de Obregón, Cuquío, had wells exceeding the Mexican na- municipal capitals, 44 of the wells, in and Yahualica de González Gallo, tional guideline value for arsenic was 13 municipal capitals, had a mean total which each had a mean total arsenic around 125 000 persons. arsenic concentration exceeding 25 concentration in the range of 0 to 1 The cities with the highest mean μg/L (Table 2). Of these 44 wells, the μg/L (as noted earlier in this article, concentrations of total arsenic were water from 23 of them, located in 13 these three municipal capitals are Mexticacán (101.9 μg/L), Teocaltiche municipal capitals, had a mean tem- being supplied with surface water). (89.5 μg/L), and San Juan de los Lagos perature higher than 30 °C. The estimated daily exposure doses (54.5 μg/L). These data suggest that Electric conductivity is an indirect to arsenic in drinking water in the 17 the approximately 70 000 inhabitants measure of total dissolved solid con- municipal capitals are presented in in these three cities could be under se- centration. Due to technical problems, Table 4. Mexticacán, Teocaltiche, and rious health risk due to the chronic in- EC was not accurately measured in 17 San Juan de los Lagos were the cities gestion of high levels of arsenic from wells. In the 112 water wells accurately with the highest estimated levels of drinking water. Assuming that the tested, the EC ranged from 155 to 1 888 exposure. The range of values estimated WHO guideline value for arsenic of 10 μS/cm. The highest value was mea- for the arsenic exposure doses were: ba- μg/L is a better criterion for protecting sured in Well No. 1 in San Juan de los bies, 1.1–7.6 μg/kg/d; children, 0.7–5.1 human health, more than 400 000 resi- Lagos. Other wells with very high EC μg/kg/d; and adults, 0.4–2.7 μg/kg/d.
240 Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico Original research
TABLE 2. Total arsenic concentration and other physical properties of well waters that ex- DISCUSSION ceed the Mexican national guideline value of 25 μg/L for arsenic, in the Los Altos de Jalisco region of Mexico, 2002–2003 Arsenic occurrence
a Arsenic (μg/L) Temperature EC Three main factors are essential to Municipal capital/Well (°C) pH (μS/cm) Mean Minb Maxc the presence of arsenic in groundwa- Encarnación de Díaz ter: (1) a source of arsenic (minerals, Well No. 1 26.8 7.0 451 25.7 23.7 28.6 rocks, sediments, and soils), (2) envi- Well No. 2 27.0 7.4 . . . d 28.8 26.7 30.8 Well No. 6 25.8 7.2 661 30.9 23.2 42.8 ronmental conditions to enhance mobi- Jalostotitlán lization of arsenic (temperature, pH, Well No. 1 24.7 7.0 494 27.4 25.0 29.8 redox potential, and chemical species), Well No. 4 25.7 7.0 446 26.0 24.2 27.9 and (3) physical and chemical phenom- Jesús María ena that increase the transport pro- Well No. 4 24.1 6.5 . . . 28.1 10.4 52.5 cesses (adsorption-desorption) (8, 23). Lagos de Moreno In natural waters, arsenic can occur Well J 35.2 6.5 395 25.2 23.6 27.8 Well O 23.8 7.3 1 08428.1 13.8 39.4 in several oxidation states (–3, 0, +3, Well Q 22.2 7.2 830 29.6 20.8 43.3 and +5), but it is present mainly as ar- Mexticacán senite (As(III)) and arsenate (As(V)) Well No. 1 26.9 7.1 565 45.1 36.5 63.1 oxyanions. While speciation of arsenic Well No. 2 30.0 7.3 489 62.3 51.5 68.1 Well No. 3 37.7 7.1 691 222.6 197.0 262.9 is strongly dependent on both redox Ojuelos de Jalisco potential and pH (8), other important Well A 37.4 6.9 . . . 29.8 24.9 31.9 factors, such as temperature and the Well B 36.3 6.9 548 28.8 24.8 33.9 occurrence of metallic sulfide and ox- Well C 38.7 7.0 . . . 26.4 20.5 31.6 ides, also affect arsenic speciation. San Juan de los Lagos Under reducing conditions, such as Well No. 1 42.6 7.0 1 888 100.3 88.7 113.8 Well No. 2 31.1 7.5 1 045 67.8 55.4 87.8 those often found in underground Well No. 3 29.5 7.3 491 29.2 8.7 52.2 aquifers, arsenite is generally the most Well No. 4 45.2 7.1 . . . 73.7 73.7 73.7 common species present (24). The Well No. 7 34.6 7.1 488 40.6 32.0 47.1 level of dissolved arsenic in natural Well No. 11 29.6 7.0 531 38.0 16.2 76.5 Well No. 13 29.0 6.9 762 34.8 0.5 58.6 waters is predominantly controlled by Well No. 15 27.0 7.0 672 67.9 56.4 73.0 the capacity of some metallic oxides Well No. 17 29.3 7.2 . . . 74.2 69.5 78.9 present in aquifers to absorb or desorb Well No. 18 32.1 7.0 1 125 87.3 79.2 96.6 arsenites and arsenates (25). From the San Julián Well No. 1 25.1 6.8 439 27.8 11.6 62.0 health point of view, the oxidation San Miguel el Alto state of arsenic is important. Trivalent Well No. 2 22.6 7.2 922 59.1 43.4 74.8 arsenic (As(III)) is more toxic than Well No. 5 24.1 7.2 . . . 48.0 48.0 48.0 pentavalent arsenic (As(V)) is. Teocaltiche Our study has shown that the total Well No. 2 31.9 6.8 772 75.0 60.9 82.4 arsenic concentrations in the LAJ Well No. 3 28.2 6.6 647 73.3 56.3 88.7 Well No. 4 34.8 6.7 620 142.8 129.0 157.7 groundwater fall on the lower bound- Well No. 5 31.8 6.6 1 074 95.5 77.2 114.4 ary of both subsurface natural waters Well No. 6 26.2 7.2 866 71.2 54.0 105.0 (< 0.5 to 5 000 μg/L) (8) and of deep geo- Tepatitlán de Morelos thermal waters (< 100 to 50 000 μg/L) Well No. 9 37.9 6.5 342 33.8 26.3 38.7 Well No. 10 42.3 6.9 576 69.5 61.3 75.0 (26). The data that we collected do not Well No. 17 37.9 6.8 422 44.2 41.6 47.5 make it possible to establish the oxida- Well No. 20 32.5 6.8 423 47.4 44.8 48.9 tion states of arsenic in the LAJ ground- Well No. 21 41.9 6.8 313 27.3 25.2 30.4 waters. Nevertheless, the mean pH val- Well No. 22 24.0 6.0 450 25.5 23.3 27.8 ues (from 6.3 to 7.4), depth of the water Valle de Guadalupe Well No. 1 34.8 7.0 548 28.7 22.4 47.0 wells (ranging from approximately Well No. 2 33.9 7.1 508 32.9 24.1 44.1 50 m to 550 m), and high proportion of Well No. 3 36.8 6.8 375 25.6 19.8 32.3 volcanic rocks in the aquifers indicate Well No. 4 34.7 7.3 484 25.4 16.5 32.6 that reducing conditions might exist in Villa Hidalgo the LAJ groundwater supplies (25, 27, Well No. 17 25.7 6.5 204 33.4 30.2 36.5 28). The data in Table 1 suggest that a EC = electric conductivity. there are two groups of aquifers in the b Min = minimum. c Max = maximum. LAJ region. One group shows a posi- d The ellipsis points (. . .) indicate missing data, where, due to technical problems, EC was not accurately measured. tive correlation between arsenic and
Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 241 Original research Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico
TABLE 3. Number and percentage of water wells in the municipal capitals of the Los Altos FIGURE 5. Percentage of water wells in the de Jalisco region of Mexico, by range of the mean total arsenic concentration, 2002–2003 municipal capitals of the Los Altos de Jalisco region of Mexico, by range of ar- Concentration of arsenic (µg/L) senic concentration (C ) (μg/L), 2002–2003 Total W < ≤ a < ≤ > no. of 0 CW 10 10 CW 25 CW 25
Municipal capital wells No. % No. % No. % CW>100 ≤ 2.3% 0 are consuming contaminated water. This situation might represent a seri- ous human health risk for the inhabi- FIGURE 4. Distribution of arsenic concentrations (CW) in water wells in the municipal capi- tals of the Los Altos de Jalisco region of Mexico, 2002–2003 tants of this area and for any people who consume agricultural or livestock 80 products that come from this region. In the LAJ region, both agricul- 70 tural and livestock activities are very 60 75 intensive and highly groundwater- dependent, with more than 1 600 50 water wells in use (29). Only 10% of 40 these wells are being used to supply potable water (for drinking, cooking, 30 Number of Wells and other household purposes). The 20 29 use of contaminated water represents a serious environmental problem for 10 3 the regional ecosystem, mainly for hu- 10 12 0 man beings, and the situation needs 0 242 Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico Original research FIGURE 6. Cumulative distribution of arsenic concentrations in water wells in the municipal Human exposure to arsenic capitals of the Los Altos de Jalisco region of Mexico, 2002–2003 Arsenic in the LAJ region is ingested 140 129 119 via three main routes: drinking water, ells 120 eating food, and consuming hot bever- w ages (tea and/or coffee). In this study 100 we have used two sets of data: (1) the 80 concentration of arsenic in the water samples that we studied and (2) the lev- 60 44 els of arsenic in foods, obtained from Number of 40 the scientific literature. The intake of 15 arsenic from hot beverages and food in 20 3 countries such as Bangladesh, Canada, 0 Chile, Croatia, India, Japan, Mexico, > 0 > 10 > 25 > 50 > 100 Spain, and the United States has been well documented (17, 30–38), but there Arsenic concentration, μg/L is no information about that for the LAJ region. Nevertheless, data on the daily intake of total arsenic in food from FIGURE 7. Distribution of the mean arsenic concentration in the groundwaters of the mu- other regions similar to the LAJ (17, 35, nicipalities in the Los Altos de Jalisco region of Mexico, 2002–2003a 38, 39) have been used in the simulation process to estimate exposure doses in a more accurate manner. The studies for other countries men- tioned in the preceding paragraph indi- cate that the highest levels of arsenic N are found in seafood, cereals, meat, and meat by-products. Approximately 90% of the dietary intake of total arsenic W E comes from seafood. Most seafood ar- senic (80%–99%) is present in organic forms, which are less toxic (32). Esti- S mates of the mean daily intake of total arsenic in food for adults range from 42 μ μ Arsenic, μg/L g in Canada to 286 g in Spain (40). The Joint Food and Agriculture 50–100 Organization/World Health Organi- 25–50 zation Expert Committee on Food Ad- ditives has evaluated arsenic toxicity, 10–25 and has established a provisional tol- 1–10 erable weekly intake (PTWI) of 15 μg/ 0–1 kg/w for inorganic arsenic, equivalent to a provisional tolerable daily intake (PTDI) of 2.14 μg/kg/d. (PTWI is an estimate of the amount of a contami- 0 50 100 150 200 kilometers nant that can be ingested weekly over a lifetime without appreciable health a The arsenic concentration in the potable water of Cañadas de Obregón, Cuquío, and Yahualica de González Gallo (the three risk (41).) Daily exposure doses greater areas shown in white) was not analyzed in this study because their water supply comes only from surface water. A prelimi- than the PTDI might represent a po- nary study performed by the authors of this study (not published) found that the arsenic concentrations in those cities were lower than 1 μg/L. tential health risk. Using the recom- mended PTDI values of the Expert Committee, the provisional tolerable daily intake of arsenic for babies culture has 150–250 µg As/L (31), high the LAJ fields are being irrigated with (10 kg), children (20 kg), and adults levels of arsenic were found in corn arsenic-contaminated waters, there is (70 kg) living in LAJ region is 21.4, (1 848 μg/kg) and potatoes (864 μg/kg). no information on the arsenic levels in 42.8, and 150.0 μg As/d, respectively. While agricultural products grown in these products. These values indicate that the maxi- Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 243 Original research Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico TABLE 4. Estimated daily exposure dose (µg/kg/d) of arsenic in drinking water, with mean, minimum (min) value, and maximum (max) value, for babies, children, and adults in the municipal capitals of the Los Altos de Jalisco region of Mexico, 2002–2003a Babies (10 kg) Children (20 kg) Adults (70 kg) Municipal capital Mean Min Max Mean Min Max Mean Min Max Acatic 1.2 0.4 2.3 0.8 0.3 1.5 0.4 0.1 0.8 Arandas 1.1 0.3 2.0 0.7 0.2 1.3 0.4 0.1 0.7 Encarnación de Díaz 1.9 1.3 3.2 1.3 0.9 2.1 0.7 0.5 1.1 Jalostotitlán 1.8 1.4 2.2 1.2 0.9 1.5 0.6 0.5 0.8 Jesús María 1.7 0.3 3.9 1.1 0.2 2.6 0.6 0.1 1.4 Lagos de Moreno 1.6 0.8 3.2 1.1 0.5 2.2 0.6 0.3 1.1 Mexticacán 7.6 1.0 19.7 5.1 0.6 13.1 2.7 0.3 6.9 Ojuelos de Jalisco 2.1 1.5 2.5 1.4 1.0 1.7 0.7 0.5 0.9 San Diego de Alejandría 1.6 0.4 3.9 1.0 0.2 2.6 0.5 0.1 1.4 San Juan de los Lagos 4.1 0.0 8.5 2.7 0.0 5.7 1.4 0.0 3.0 San Julián 1.5 0.6 4.6 1.0 0.4 3.1 0.5 0.2 1.6 San Miguel el Alto 2.3 0.4 5.6 1.5 0.3 3.7 0.8 0.2 2.0 Teocaltiche 6.7 4.1 11.8 4.5 2.7 7.9 2.4 1.4 4.2 Tepatitlán de Morelos 1.7 0.3 5.6 1.1 0.2 3.7 0.6 0.1 2.0 Unión de San Antonio 1.5 0.5 2.4 1.0 0.3 1.6 0.5 0.2 0.8 Valle de Guadalupe 2.1 1.2 3.5 1.4 0.8 2.4 0.7 0.4 1.2 Villa Hidalgo 1.2 0.3 2.7 0.8 0.2 1.8 0.4 0.1 1.0 a A simulation process was developed to estimate the levels of exposure to arsenic. Calculations were based on the following assumptions: (1) the babies’ daily diet included a food formula prepared with 750 mL of tap water, (2) the children’s daily diet included 1 000 mL of tap water, and (3) the adults’ daily diet included 1 850 mL of tap water. The mean, minimum, and maxi- mum daily exposure doses to arsenic were estimated by using, respectively, the mean, minimum, and maximum concentrations of total arsenic in drinking water found from the sampling of the wells (Table 1). mum tolerable concentration of ar- In addition to the exposure time and no epidemiological studies have been senic in drinking water for babies, chil- the doses to which a person is ex- done in the LAJ region to assess the dren, and adults should not be higher posed, sensitivity to the toxic effects of impact of groundwater arsenic on the than 28.5, 42.8, and 81.0 μg/L, respec- arsenic is different for each individual, health of people living there. tively. Data from Table 1 indicate that: and appears to be strongly dependent In general, most of the epidemiolog- (1) there are 4 cities where the mean on the person’s nutritional status and ical studies analyze the toxicological concentration of total arsenic is greater genetic characteristics (42). Neverthe- effects of ingesting arsenic alone. Nev- than 28.5 μg/L, (2) in 3 cities the mean less, other factors could play an impor- ertheless, drinking water might con- arsenic concentration is higher than tant role in mitigating the toxic effect tain an excess of several chemical ele- 42.8 μg/L, and (3) in just 2 cities the of ingested arsenic, such as increased ments or compounds, so synergistic potable water has a mean arsenic con- awareness and better education (43). and/or antagonistic effects should be centration over 81.0 μg/L. It is impor- For example, there are some nutrients considered. tant to note that these numbers have a that can reduce the toxicity of arsenic, In the case of the LAJ groundwater, relative value and should be used only such as vitamin C and methionine. In there are some aquifers where both ar- as an index. Since each person has his contrast, vitamin A deficiency in- senic and fluoride exceed Mexican na- or her own metabolism, an intake creases the toxic effects of arsenic (35). tional guideline values. In addition, above the PTDI does not automatically Drinking water over a period of high levels of fluoride in bottled drink- mean that health is at risk. many years with a level of exposure ing water sold in the LAJ region have There are many cases around the even as low as 1.0 µg/kg/d has been been reported (3). Epidemiological world in which water discharged from associated not only with minor skin studies performed in the province of wells is directly delivered to a group diseases but also with skin, bladder, Xinjiang, China, have indicated that of houses. Thus, individual calcula- kidney, and liver cancer (4). There are fluoride and arsenic do not have a mu- tions for each well (mainly for those many examples from around the tual synergistic action. However, simi- wells exceeding standards) and for the world that show the dramatic health lar studies done in the province of group of people who use that well effects from ingesting arsenic from Guizhou, China, have suggested that should be performed. As indicated in groundwater, and the need to moti- the toxicological effects of fluoride Table 2, there are 32 wells with a mean vate health authorities to mitigate this could be enhanced by arsenic (44). total arsenic concentration greater situation. The most striking examples Studies from Mexico and many than 28.5 μg/L, 19 wells with a mean have been in Bangladesh, India (West other countries around the world indi- above 42.8 μg/L, and 5 wells with a Bengal), China (Inner Mongolia), and cate that guideline values (national or mean greater than 81.0 μg/L. Taiwan (9, 43). Unfortunately, so far, international) for both arsenic and flu- 244 Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico Original research oride are quite frequently exceeded drinking water at 10 μg/L, as sug- needed to determine the transport and both in drinking water supplies and in gested by the WHO. It is important to fate of arsenic in the environment. waters that are delivered to the public note that it is an interim regulation, Third, determining total and inorganic water system. Presently, arsenic and mainly when there is enough informa- arsenic levels in foods and beverages fluoride are recognized as the most se- tion indicating that potential cancer consumed in the LAJ region might rious inorganic contaminants in drink- risks remain high at the present guide- help to better estimate human expo- ing water on a worldwide basis (8). line of 10 μg/L (50). It is possible that sure. Fourth, epidemiological studies In Mexico only a few epidemiologi- this standard will be reduced in the to determine the arsenic levels in the cal studies have been done on the near future, as happened in Australia, blood, hair, and nails of humans health problems due to the ingestion where the guideline value is 7 μg/L should be conducted in the LAJ region, of arsenic from drinking water. Sev- (40). Regulations are a very important to help assess the relationship between eral studies have been done in the Co- in reducing health problems and im- the prevalence of health problems and marca Lagunera region to determine proving the quality of life. However, the chronic ingestion of arsenic. Fi- the effect of arsenic on skin cancer and there are other associated factors such nally, point-of-use solutions, such as its relation with the human papilloma as the enforcement of the law, the im- household filters and small treatment virus and changes in the immune sys- provement of nutrition programs, and plants, should be implemented in the tem (45–47). Levels of arsenic in urine risk communication. LAJ towns with high levels of arsenic. and the accumulation of arsenic in This exhaustive study was the first some parts of the body have been de- one ever done that was intended to termined in the city of Hermosillo, the generate a database on the level of ar- Acknowledgements. The authors Valle de Zimapán, and the Valle del senic in groundwater supplies in the would like to acknowledge the finan- Yaqui (39, 48, 49). LAJ region and to serve as a general cial support from El Colegio de la The arsenic concentrations found in indicator of the potential significance Frontera Norte, A.C., Mexico; the Uni- well waters in the LAJ region were of arsenic contamination in the area. versity of Texas at El Paso’s Center for lower than those reported in some other Our data set is not large enough to Environmental Resource Management areas of Mexico, including the Comarca perform detailed analyses regarding through funding from the Office of Lagunera, the Valle de Zimapán, and health environmental risks. This is due Exploratory Research of the U.S. En- the city of Hermosillo. However, there to the lack of information on the level vironment Protection Agency (Co- are many wells in the LAJ region with of arsenic in foods, and the lack of epi- operative Agreement CR-819849-01); arsenic levels exceeding both Mexican demiological studies. However, the re- and the National Institutes of Health national standards and international sults produced so far have allowed us (Grant S06GM8012-33). The authors standards, and this situation should be to reach five major conclusions con- also thank the Historically Black Col- a major concern. Skin diseases, gastro- cerning additional studies that should lege and University/Minority Institu- intestinal effects, neurological damage, be performed in the LAJ region. First, tion Environmental Technology Con- cardiovascular problems, and hemato- additional physicochemical studies sortium, which is funded by the U.S. logical effects are some of the potential on the arsenic oxidation state in the Department of Energy. We also ac- health effects from chronic arsenic in- groundwater are needed to determine knowledge the valuable technical sup- gestion at the exposure doses estimated the water’s level of toxicity and to bet- port received from the Los Altos de for the LAJ region. ter understand the process of mobi- Jalisco water utility authorities, and Most developed countries have set lization and transport of arsenic spe- the logistical support received from the guideline value for arsenic in cies. Second, geochemical studies are Autotransportes Mezcala, S.A. REFERENCES 1. México, Instituto Nacional de Estadística, Hazardous Substance Research Center; 2001. ing water supplies. Washington, D.C.: EPA; Geografía e Informática. XII Censo General de Pp. 211–9. 2000. (Report EPA-815-R-00-023). Población y Vivienda 2000. Aguascalientes: 3. Hurtado R, Gardea-Torresdey J. Environmen- 6. Thompson TS, Le MD, Kasick AR, Macaulay INEGI; 2001. tal evaluation of fluoride in drinking water at TJ. 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Food Addit National Academy Press; 2001. 24. Lemmo NV, Faust SO, Belton T, Tucker R. As- Contam. 2003;20(10):923–32. sessment of the chemical and biological sig- 38. Del Razo LM, Garcia-Vargas GG, Garcia- nificance of arsenical compounds in a heavily Salcedo J, Sanmiguel MF, Rivera M, Hernan- contaminated watershed. Part I. The fate and dez MC, et al. Arsenic levels in cooked food speciation of arsenical compounds in aquatic and assessment of adult dietary intake of ar- environments—a literature review. J Environ senic in the Region Lagunera, Mexico. Food Manuscript received 4 March 2005. Revised manuscript Sci Health. 1983;A18(3):335–87. Chem Toxicol. 2002;40:1423–31. accepted for publication 11 January 2006. 246 Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 Hurtado-Jiménez et al. • Arsenic in drinking water in the Los Altos de Jalisco region of Mexico Original research RESUMEN Objetivos. Determinar el grado de contaminación con arsénico del agua potable en la región de Los Altos de Jalisco (LAJ), en la parte centrooccidental de México, y esti- mar el nivel de exposición que enfrentan los habitantes de esa zona. Arsénico en el agua potable Métodos. Se determinó la concentración total de arsénico (la suma de todas las for- de la región de Los Altos mas de arsénico, tanto orgánicas como inorgánicas) en 129 pozos de agua públicos en de Jalisco, México 17 cabeceras municipales de LAJ, mediante espectroscopia de emisión óptica con plasma inductivamente acoplado. En la mayoría de los pozos se tomaron muestras en noviembre de 2002 y en octubre de 2003. En los restantes se tomó la muestra en uno de esos dos momentos. El nivel de exposición al arsénico se estimó para lactantes (10 kg), niños (20 kg) y adultos (70 kg). Resultados. En 44 (34%) de los 129 pozos se encontraron concentraciones media de arsénico superiores al límite de 25 μg/L, establecido en la norma nacional mexicana. Las concentraciones media de arsénico total en los 129 pozos estuvieron entre 14,7 μg/L y 101,9 μg/L. Las mayores concentraciones se encontraron en las muestras de agua colectadas en los pozos de Mexticacán (262,9 μg/L), Teocaltiche (157,7 μg/L) y San Juan de los Lagos (113,8 μg/L). Si se toma en cuenta la concentración general de todos los pozos de cada una de las 17 ciudades, la concentración media de arsénico fue superior a lo establecido en la norma mexicana en 7 ciudades. La concentración media general en las 17 ciudades fue superior al valor de 10 μg/L establecido en los lineamientos de la Organización Mundial de la Salud. Los niveles estimados de las dosis de exposición al arsénico por el agua potable fue de 1,1–7,6 μg/kg/d en los lac- tantes, de 0,7–5,1 μg/kg/d en los niños y de 0,4–2,7 μg/kg/d en los adultos. Conclusiones. Según la dosis de exposición estimada en la región de LAJ, la inges- tión continuada de arsénico puede afectar a la salud y causar enfermedades de la piel, trastornos gastrointestinales, daños neurológicos, problemas cardiovasculares y afec- ciones hematológicas. Aunque esta situación no afecte a todos los habitantes, la salud de una gran parte de la población de LAJ puede encontrarse en riesgo debido a la in- gestión de cantidades elevadas de arsénico. Se deben realizar estudios epidemiológi- cos para determinar el contenido de arsénico en la sangre, el pelo y las uñas de las per- sonas que viven en la región de LAJ, a fin de ayudar a evaluar la relación entre la prevalencia de problemas de salud y la ingestión continuada de arsénico. Palabras clave Arsénico, abastecimiento de agua, contaminantes del agua, México. Por una juventud sin tabaco En la primera parte del libro se muestran los problemas fundamentales del consumo de tabaco, especialmente para la juventud. Se revisan temas relacionados con la prevención de las enfermedades relacionadas con el tabaco en los países de la Región y se describen los aspectos más eficaces de los diferentes métodos usados para su preven- ción. En la segunda, se presentan los enfoques teóricos y prácticos del programa de prevención del hábito de fumar conocido como "Habilidades para la vida", que alecciona a los jóvenes para que sean capaces de resistir las presiones sociales y de los medios de comunicación que los incitan a fumar. Esta publicación está destinada a los profesionales de la salud, los planificadores de programas, los educadores, los encargados de formular las políticas y los grupos e insti- tuciones que participan en la lucha contra el tabaquismo. En ella encontrarán información 2001, 72p., muy útil sobre la situación del tabaquismo en la Región, así como pautas para planificar ISBN 92 75 31579 5 Código: PC 579 y desarrollar programas de prevención del abuso de drogas, similares al de "Habilidades Precios: US$ 14.00 en para la vida", que se adapten a las necesidades específicas de la Región y que sean un América Latina/ US$ 18.00 arma poderosa para la reducción de la carga evitable de muertes y discapacidades rela- en el resto del mundo cionadas con el tabaco. Envíe su pedido y pago en dólares estadounidense a: http://publications.paho.org; correo electrónico: [email protected]; Fax: (301) 209-9789; Tel: (301) 617-7806; (1-800) 472-3046 (U.S. solamente) Rev Panam Salud Publica/Pan Am J Public Health 20(4), 2006 247