Tag Archives: Mexico

Drinking Water Quality in Rural Oaxaca, Mexico

Rowles LS 3rd, Alcalde R, Bogolasky F, Kum S, Diaz-Arriaga FA, Ayres C, Mikelonis AM, Toledo-Flores LJ, Alonso-Gutiérrez MG, Pérez-Flores ME, Lawler DF, Ward PM, Lopez-Cruz JY, Saleh NB. Perceived versus actual water quality: Community studies in rural Oaxaca, Mexico. Sci Total Environ. 2017 Dec 6;622-623:626-634. doi: 10.1016/j.scitotenv.2017.11.309.

Compromised water quality risks public health, which becomes particularly acute in economically marginalized communities. Although the majority of the clean-water-deprived population resides in Sub-Saharan Africa and Asia, a significant portion (32 million) lives in Meso- and Latin-America. Oaxaca is one of the marginalized southern states of Mexico, which has experienced high morbidity from infectious diseases and also has suffered from a high rate of infant mortality. However, there has been a paucity of reports on the status of water quality of culturally diverse rural Oaxaca. This study follows community-based participatory research methods to address the data gap by reporting on water quality (chemical and microbiological) and by exploring social realities and water use practices within and among communities. Surveys and water quality analyses were conducted on 73 households in three rural communities, which were selected based on the choice of water sources (i.e., river water, groundwater, and spring water). Statistically significant variations among communities were observed including the sanitation infrastructure (p-value 0.001), public perception on water quality (p-value 0.007), and actual microbiological quality of water (p-value 0.001). Results indicate a high prevalence of diarrheal diseases, a desire to improve water quality and reduce the cost of water, and a need for education on water quality and health in all the surveyed communities. The complexities among the three studied communities highlight the need for undertaking appropriate policies and water treatment solutions.

Prenatal Fluoride Exposure Associated with Lower Cognitive Function, Mexico

Bashash M, Thomas D, Hu H, Angeles Martinez-Mier E, Sanchez BN, Basu N, Peterson KE, Ettinger AS, Wright R, Zhang Z, Liu Y, Schnaas L, Mercado-García A, María Téllez-Rojo M, Hernández-Avila M. Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6-12 Years of Age in Mexico. Environmental health perspectives. 2017 Sep 19;125(9):097017. doi: 10.1289/EHP655.

BACKGROUND: Some evidence suggests that fluoride may be neurotoxic to children. Few of the epidemiologic studies have been longitudinal, had individual measures of fluoride exposure, addressed the impact of prenatal exposures or involved more than 100 participants.

OBJECTIVE: Our aim was to estimate the association of prenatal exposure to fluoride with offspring neurocognitive development.

METHODS: We studied participants from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) project. An ion-selective electrode technique was used to measure fluoride in archived urine samples taken from mothers during pregnancy and from their children when 6-12 y old, adjusted for urinary creatinine and specific gravity, respectively. Child intelligence was measured by the General Cognitive Index (GCI) of the McCarthy Scales of Children’s Abilities at age 4 and full scale intelligence quotient (IQ) from the Wechsler Abbreviated Scale of Intelligence (WASI) at age 6-12.

RESULTS: We had complete data on 299 mother-child pairs, of whom 287 and 211 had data for the GCI and IQ analyses, respectively. Mean (SD) values for urinary fluoride in all of the mothers (n=299) and children with available urine samples (n=211) were 0.90 (0.35) mg/L and 0.82 (0.38) mg/L, respectively. In multivariate models we found that an increase in maternal urine fluoride of 0.5mg/L (approximately the IQR) predicted 3.15 (95% CI: -5.42, -0.87) and 2.50 (95% CI -4.12, -0.59) lower offspring GCI and IQ scores, respectively.

CONCLUSIONS: In this study, higher prenatal fluoride exposure, in the general range of exposures reported for other general population samples of pregnant women and nonpregnant adults, was associated with lower scores on tests of cognitive function in the offspring at age 4 and 6-12 y. https://doi.org/10.1289/EHP655.

Antimony Leaching from Drinking Water Bottling Material

C.A. Chapa-Martínez, L. Hinojosa-Reyes, A. Hernández-Ramírez, E. Ruiz-Ruiz, L. Maya-Treviño, J.L. Guzmán-Mar. An evaluation of the migration of antimony from polyethylene terephthalate (PET) plastic used for bottled drinking water. Science of The Total Environment, Volume 565, 15 September 2016, Pages 511-518.

The leaching of antimony (Sb) from polyethylene terephthalate (PET) bottling material was assessed in twelve brands of bottled water purchased in Mexican supermarkets by atomic fluorescence spectrometry with a hydride generation system (HG-AFS). Dowex® 1X8-100 ion-exchange resin was used to preconcentrate trace amounts of Sb in water samples. Migration experiments from the PET bottle material were performed in water according to the following storage conditions: 1) temperature (25 and 75 °C), 2) pH (3 and 7) and 3) exposure time (5 and 15 days), using ultrapure water as a simulant for liquid foods. The test conditions were studied by a 23 factorial experimental design. The Sb concentration measured in the PET packaging materials varied between 73.0 and 111.3 mg/kg. The Sb concentration (0.28–2.30 μg/L) in all of the PET bottled drinking water samples examined at the initial stage of the study was below the maximum contaminant level of 5 μg/L prescribed by European Union (EU) regulations. The parameters studied (pH, temperature, and storage time) significantly affected the release of Sb, with temperature having the highest positive significant effect within the studied experimental domain. The highest Sb concentration leached from PET containers was in water samples at pH 7 stored at 75 °C for a period of 5 days. The extent of Sb leaching from the PET ingredients for different brands of drinking water can differ by as much as one order of magnitude in experiments conducted under the worst-case conditions. The chronic daily intake (CDI) caused by the release of Sb in one brand exceeded the Environmental Protection Agency (USEPA) regulated CDI value of 400 ng/kg/day, with values of 514.3 and 566.2 ng/kg/day for adults and children. Thus, the appropriate selection of the polymer used for the production of PET bottles seems to ensure low Sb levels in water samples.

How do Climate Models Account for Volcano Eruptions?

“Popocatépetl volcano came to life on Sunday morning, sending a column of gas and ash 2,000 metres (6,500ft) into the sky in central Mexico. A 12km (7.5-mile) security ring around the volcano has been mandated, preventing passage close to the crater. Popocatépetl’s last major eruption was in 2000, when more than 40,000 people had to be evacuated.” click here

Association of Urine Fluoride with Dental Fluorosis; Mexico

Jarquín-Yañez L, de Jesús Mejía-Saavedra J, Molina-Frechero N, Gaona E, Rocha-Amador DO, López-Guzmán OD, Bologna-Molina R. Association between urine fluoride and dental fluorosis as a toxicity factor in a rural community in the state of San Luis Potosi. TheScientificWorldJournal. 2015;2015:647184. doi: 10.1155/2015/647184.

OBJECTIVE: The aim of this study is to investigate urine fluoride concentration as a toxicity factor in a rural community in the state of San Luis Potosi, Mexico.

MATERIALS AND METHODS: A sample of 111 children exposed to high concentrations of fluoride in drinking water (4.13 mg/L) was evaluated. Fluoride exposure was determined by measuring urine fluoride concentration using the potentiometric method with an ion selective electrode. The diagnosis of dental fluorosis was performed by clinical examination, and the severity of damage was determined using Dean’s index and the Thylstrup-Fejerskov (TF) index.

RESULTS: The range of exposure in the study population, evaluated through the fluoride content in urine, was 1.1 to 5.9 mg/L, with a mean of 3.14±1.09 mg/L. Dental fluorosis was present in all subjects, of which 95% had severe cases. Higher urine fluoride levels and greater degrees of severity occurred in older children.

CONCLUSIONS: The results show that dental fluorosis was determined by the presence of fluoride exposure finding a high positive correlation between the severity of fluorosis and urine fluoride concentration and the years of exposure suggested a cumulative effect.

Concurrent Exposure to Arsenic and Fluoride

González-Horta C, Ballinas-Casarrubias L, Sánchez-Ramírez B, Ishida MC, Barrera-Hernández A, Gutiérrez-Torres D, Zacarias OL, Saunders RJ, Drobná Z, Mendez MA, García-Vargas G, Loomis D, Stýblo M, Del Razo LM. A Concurrent Exposure to Arsenic and Fluoride from Drinking Water in Chihuahua, Mexico. International Journal of Environmental Research and Public Health. 2015 Apr 24;12(5):4587-4601.

Inorganic arsenic (iAs) and fluoride (F-) are naturally occurring drinking water contaminants. However, co-exposure to these contaminants and its effects on human health are understudied. The goal of this study was examined exposures to iAs and F- in Chihuahua, Mexico, where exposure to iAs in drinking water has been associated with adverse health effects. All 1119 eligible Chihuahua residents (>18 years) provided a sample of drinking water and spot urine samples. iAs and F- concentrations in water samples ranged from 0.1 to 419.8 µg As/L and from 0.05 to 11.8 mg F-/L. Urinary arsenic (U-tAs) and urinary F- (U-F-) levels ranged from 0.5 to 467.9 ng As/mL and from 0.1 to 14.4 µg F-/mL. A strong positive correlation was found between iAs and F- concentrations in drinking water (rs = 0.741). Similarly, U-tAs levels correlated positively with U-F- concentrations (rs = 0.633). These results show that Chihuahua residents exposed to high iAs concentrations in drinking water are also exposed to high levels of F-, raising questions about possible contribution of F- exposure to the adverse effects that have so far been attributed only to iAs exposure. Thus, investigation of possible interactions between iAs and F- exposures and its related health risks deserves immediate attention.

Arsenic and Fluoride in an Endorheic Basin Groundwater

Reyes-Gómez VM, Alarcón-Herrera MT, Gutiérrez M, López DN.
Arsenic and Fluoride Variations in Groundwater of an Endorheic Basin Undergoing Land-Use Changes. Arch Environ Contam Toxicol. 2014 Sep 16.

The salt content of soil and water in endorheic basins within arid areas greatly restrict agricultural activities. Despite this limitation, these lands are increasingly used to accommodate new settlements and/or agricultural practices. This study focuses on the Laguna El Cuervo closed basin of northern Mexico and its underlying aquifer, which has been found to contain high concentrations of arsenic (As) and fluoride (F). The spatial distribution of As and F, their variations with time, and the impact of drought conditions and land-use changes were investigated using well data collected from a total of 27 wells in 2007, 2010, and 2011 (As data also collected in 2005). Four of these wells were used as monitoring wells. Data also included the As content of 140 surface sediments. Results showed that 54.5 % of the wells surpassed the As limit for drinking water of 0.025 mg L-1 and that 89.0 % surpassed he F limit of 1.5 mg L-1. Spatial analyses identified the areas in the center of the basin with the highest content of contaminants. Principal component and correlation analyses showed a co-occurrence of As and F with r = 0.55 for the 2011 data and 0.59 for the combined data. In contrast, the relationship of As and F concentrations to droughts and changes in land use were not as clearly shown, possibly because of the short time this area has been monitored. The high As and F concentrations in the groundwater may be limiting the availability of water within this basin, especially considering the greater groundwater demand foreseen for the future. Water-conservation practices, such as drip irrigation and artificial groundwater recharge, should be considered to maintain groundwater levels supportive of agricultural practices.

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