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Background: Cortisol has functions on homeostasis, growth, neurodevelopment, immune function and the stress response. Secretion follows a diurnal rhythm that mediates these processes. Our objective was to examine the association between prenatal lead exposure and infant diurnal cortisol rhythms.Methods: We measured infant cortisol rhythms in saliva collected repeatedly over 2 days at either 12 (n = 255) or 18-24 (n = 150) months of age. Prenatal lead exposure was assessed by measuring maternal pregnancy blood lead levels and early postnatal maternal bone lead content. We analyzed age-specific basal secretion and the association between trimester-specific and cumulative lead exposure with a) change in total diurnal cortisol and b) the shape of the cortisol curve across the length of the day.Results: Our results showed age related differences in salivary cortisol secretion and an age dependent association with maternal lead exposure. In age-stratified models we saw an inverse association between lead and cortisol levels in 12-month-old infants and a positive association for 18-24-month-old infants. For the 12-month-old infants 2nd-trimester-lead ≥10 μg/dL was associated with 40 % lower cortisol levels (95 % CI (-57, -16)) and a significant change in the shape of the cortisol curve (p = 0.01), compared to infants with low blood lead levels (<5 μg/dL).Conclusions: Basal cortisol secretion changes with age. Increased early gestation lead exposure alters diurnal cortisol rhythms and the association is modified by infant age, perhaps representing an early maturation of cortisol homeostasis. [ABSTRACT FROM AUTHOR]

Abstract: A range of studies has been conducted on the detrimental effects of lead in mining and smelting communities. The neurocognitive and behavioural health effects of lead on children are well known. This research characterized the conjoint influence of lead exposure and home enriched environment on neurocognitive function and behaviour for first-grade children living in a Mexican lead smelter community. Structural equation models were used for this analysis with latent outcome variables, Cognition and Behaviour, constructed based on a battery of assessments administered to the first-grade children, their parents, and teachers. Structural equation modelling was used to describe complex relationships of exposure and health outcomes in a manner that permitted partition of both direct and indirect effects of the factors being measured. Home Environment (a latent variable constructed from information on mother''s education and support of school work and extracurricular activities), and child blood lead concentration each had a main significant effect on cognition and behaviour. However, there were no statistically significant moderation relationships between lead and Home Environment on these latent outcomes. Home Environment had a significant indirect mediation effect between lead and both Cognition and Behaviour (p-value<0.001). The mediation model had a good fit with Root Mean Square Error of Approximation <0.0001 and a Weighted Root Mean Square Residual of 0.895. These results were highly significant and suggest that Home Environment has a moderate mediation effect with respect to lead effects on Behaviour (β =0.305) and a lower mediation effect on Cognition (β =0.184). The extent of home enrichment in this study was most highly related to the mother''s support of schoolwork and slightly less by the mother''s support of extracurricular activities or mother''s education. Further research may be able to develop approaches to support families to make changes within their home and child rearing practices, or advocate for different approaches to support their child''s behaviour to reduce the impact of lead exposure on children''s cognitive and behavioural outcomes. [Copyright &y& Elsevier]

Abstract: Introduction: Because children exposed to lead have a very high health risk, surveillance and prevention programs are very important to avoid short- and long-term health effects. Objectives: To describe the trend for the blood lead levels over a 12-year period in environmentally exposed children and to document the actions implemented to reduce the blood lead levels. Materials and methods: We performed a retrospective cohort study of children aged 0–15 years who were enrolled in the Coahuila Health Secretary''s Childhood Blood Lead Level Surveillance program. This database includes children from the city of Torreon, Coahuila, Mexico, where the biggest smelter in Latin America is located. Results: A total of 151,322 observations were analyzed in the study. The percentage of samples with elevated blood lead levels decreased from 84.9% to 10.4% during 1998–2010, and the decrease was greater in girls than in boys. Conclusion: According to the results of our study, the majority of strategies and activities to decrease blood lead levels in an environmentally exposed population should be focused on children aged 0–5 years, on the home environment, on preventing fugitive emissions from smelters and other sources and on the proper disposal and confinement of industrial residues. [Copyright &y& Elsevier]

Exposure to lead (Pb) and mercury (Hg) remains a world public health problem, particularly for young children in developing countries. In Mexico, the main sources of exposure to Pb and Hg are wastes from human activities that increase the natural sources of these metals. Pb and Hg are highly toxic during development and maturation periods of the central nervous system (CNS); these effects are associated with the risk for neurodegenerative diseases. Mexico has numerous exposure sources to Pb and Hg; nevertheless, information on exposure in children is limited, particularly for Hg. Therefore, we conducted a review of the studies performed in children exposed to Pb and Hg. Data presented support that an important proportion of Mexican children have Pb levels above values associated with dangerous effects. On the other hand, studies on Hg-exposure are scarce, so we need more studies to estimate the magnitude of the problem and to determine exposure levels in Mexican children. Available data support the urgent need for coordinated actions among researchers, and health and environmental government authorities to implement education and nutritional campaigns, as well as to decrease exposure and effects of Pb and Hg. In addition, there must be a priority for the implementation of educational campaigns directed to the general population, but with emphasis in parents, education staff and health care providers to decrease both the risk of exposure of children to Pb and Hg and the effects of the exposure to these metals. [ABSTRACT FROM AUTHOR]

Background: Fetal lead exposure is associated with adverse pregnancy outcomes and developmental and cognitive deficits; however, the mechanism(s) by which lead-induced toxicity occurs remains unknown. Epigenetic fetal programming via DNA methylation may provide a pathway by which environmental lead exposure can influence disease susceptibility. Objective: This study was designed to determine whether prenatal lead exposure is associated with alterations in genomic methylation of leukocyte DNA levels from umbilical cord samples. Methods: We measured genomic DNA methylation, as assessed by Alu and LINE-1 (long interspersed nuclear element-1) methylation via pyrosequencing, on 103 umbilical cord blood samples from the biorepository of the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) study group. Prenatal lead exposure had been assessed by measuring maternal bone lead levels at the mid-tibial shaft and the patella using a spot-source 109Cd K-shell X-ray fluorescence instrument. Results: We found an inverse dose-response relationship in which quartiles of patella lead correlated with cord LINE-1 methylation (p for trend = 0.01) and and tibia lead correlated with Alu methylation (p for trend = 0.05). In mixed effects regression models, maternal tibia lead was negatively associated with umbilical cord genomic DNA methylation of Alu (β = -0.027; p = 0.01). We found no associations between cord blood lead and cord genomic DNA methylation. Conclusions: Prenatal lead exposure is inversely associated with genomic DNA methylation in cord blood. These data suggest that the epigenome of the developing fetus can be influenced by maternal cumulative lead burden, which may influence long-term epigenetic programming and disease susceptibility throughout the life course. [ABSTRACT FROM AUTHOR]

This article presents a study which evaluated the cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) contents of the white shrimp Litopenaeus vanamei from commercial landings from six lagoons of Sinaloa in Mexico and determined possible health risks for consumers. The organisms were dissected and the abdominal muscles and hepatopancreas were separated, freeze-dried, ground and homogenized in a Teflon mortar, giving three composite samples of each tissue for each lagoon. Study results reveal that the mean contents of all metals are lower in the muscle than in the corresponding hepatopancreas samples.

Studies of low to moderate level lead exposures have reported mixed findings regarding the risk of spontaneous abortion, despite lead's abortifacient properties at very high doses. To evaluate the risk of spontaneous abortion from low or moderate lead exposures, a nested case-control study was conducted within a cohort of pregnant women in Mexico City, 1994–1996. During their first trimester, 668 women enrolled, were interviewed, and contributed blood specimens. Pregnancies were followed by home visits or telephone calls. Spontaneous abortions before week 21 (n = 35) were matched with pregnancies that survived beyond week 20 (n = 60) on maternal age, hospital, date of enrollment, and gestational age at enrollment. Mean blood lead levels were 12.03 μg/dL for cases and 10.09 μg/dL for controls (p = 0.02). Odds ratios for spontaneous abortion comparing 5-9, 10-14, and ≥15 μg/dL with the referent category of <5 μg/dL of blood lead were 2.3, 5.4, and 12.2, respectively, demonstrating a significant trend (p = 0.03). After multivariate adjustment, the odds ratio for spontaneous abortion was 1.8 (95% confidence interval = 1.1, 3.1) for every 5 μg/dL increase in blood lead. Low to moderate lead exposures may increase the risk for spontaneous abortion at exposures comparable to US general population levels during the 1970s and to many populations worldwide today; these are far lower than exposures encountered in some occupations. Am J Epidemiol 1999; 150: 590-7. [ABSTRACT FROM PUBLISHER]

DNA damage and DNA repair ability by means of the comet assay and the hydrogen peroxide challenge in lymphocytes from 65 children exposed simultaneously to As and Pb in Region Lagunera, Mexico. The first exposure scenario was concerned with natural As contamination in drinking water affecting all children, particularly those attending the schools farthest from (Gomez Palacio) and closest to the smelter (Pedro Garcia). The second scenario related to additional Pb and As soil and dust contamination in the schools located in the smelter vicinity (Heroe de Nacozari and Pedro Garcia). Most children (93%) had As in urine (AsU) above 50 μg/L and 65% had blood Pb (PbB) above 10 μg/dL. The highest AsU median levels were observed in the school farthest from the smelter, whereas the highest PbB values were observed in the closest school. DNA damage and a decreased repair ability observed in children attending the schools were more severe than those reported for healthy Mexican children. However, the multivariate analysis did not show significant associations between DNA basal damage and PbB or AsU. Lymphocytes from 58% of the children did not respond to the peroxide challenge, and those had a more severe basal DNA damage. DNA repair capacity showed a slowed response and was negatively associated with AsU. Thus, in addition to reduced exposure, further studies are needed to ascertain if the deficiency in DNA repair is transient or if children are already displaying a mutator phenotype and are at risk of developing cancer. [ABSTRACT FROM AUTHOR]

With the aim of knowing seasonal variability of lead in fish and bivalve species from Coatzacoalcos estuary, biota collected during three seasons was examined. In muscle tissue of fish, the highest level (5.4 μg g−1) was found in the longnose gar Lepisosteus osseus from San Francisco stream (a highly impacted site); the lowest value (0.2 μg g−1) was registered in yellowfin mojarra Gerres cinereus from Ostión lagoon (control site). In bivalves, concentrations in soft tissue ranged from 1.5 μg g−1 in Polymesoda caroliniana from Calzadas river, to 0.1 μg g−1 in Corbicula fluminea from Hidalgotitlán (control site). [ABSTRACT FROM AUTHOR]

BACKGROUND: Previous studies have suggested an effect of high arsenic concentration on cognitive and neurobehavioral function in humans. OBJECTIVE: Our goal was to identify demographic and nutritional factors that are associated with As exposure and the influence of this exposure on cognitive function in school-age children. METHODS: We recruited 602 children 6-8 years of age living within 3.5 km of a metallurgic smelter complex in the city of Torreón, Mexico, to participate in a cross-sectional evaluation. Of these, 591 had complete anthropometry, iron, and zinc status by biochemical measurements in serum, blood lead concentration (PbB), and arsenic in urine (UAs), and 557 completed several cognitive performance tests. RESULTS: The mean for UAs was 58.1 ± 33.2 μg/L; 52% of the children had UAs concentrations > 50 μg/L, and 50.7% of children had PbB a 10 μg/dL. UAs concentration was associated with low socioeconomic status. Nutritional status indicators were not related to UAs concentrations. Linear and logistic regressions adjusted for hemoglobin concentration, PbB, and sociodemographic confounders showed a significant inverse association between UAs and Visual-Spatial Abilities with Figure Design, the Peabody Picture Vocabulary Test, the WISC-RM Digit Span subscale, Visual Search, and Letter Sequencing Tests (p < 0.05). Boys excreted significantly more UAs (p < 0.05) and were affected on different cognitive areas than girls. CONCLUSIONS: Children living in an area contaminated with both As and lead showed that As contamination can affect children's cognitive development, independent of any effect of lead. [ABSTRACT FROM AUTHOR]

The role of lead exposure or micronutrient deficiencies in children's sleep problems is unknown. Although elevated blood lead concentrations (BPb) are clearly related to behavior problems in children, few researchers have used objective observations. The authors investigated relationships between lead, micronutrient status, sleep, classroom behavior, and activity in Mexican children aged 6-8 years living close to a metal foundry. Mean BPb was 11.5 ± 6.1 μg/dL; 50% had levels &nvge; 10 μg/dL. Ten percent of children had hemoglobin < 12.4 g/dL. Parents reported on children's sleep and fatigue (n 550). The authors also observed classroom behavior (n = 157) and measured physical activity (n = 168). BPb &nvge; 10 μg/dL was associated with later waking time and shorter duration of sleep. Anemia was linked to more off-task behaviors, lower physical activity, earlier bedtime, and shorter sleep onset. Researchers should investigate these relationships further, using more sensitive measures. [ABSTRACT FROM AUTHOR]

The article provides information on evaluation of mean blood lead levels (BLLs) and the prevalence of elevated BLLs in children 1-6 year of age living in Torreón, Mexico and assessed risk factors for lead exposure in these children. In multivariate analyses, distance from the smelter, amount of income and education level of the primary caregiver predicted BLLs. In the environmental risk factor subsample dust and soil lead levels were associated with BLLs and distance from the smelter.

Discusses a study which determined the secular trend in blood lead levels in children born in Mexico City, Mexico between 1987 and 1993. Methods of the study; Effects of age on elevated blood lead levels (PbB); Effect of family use of lead-glazed ceramic pottery on PbB.

The article presents a study that investigates the lead contamination in plants, soil and water in several areas around a battery reprocessing plant in La Gloria near Tijuana in Baja California in Mexico. The study is undertaken through collecting soil samples, water sample as well as plant samples. The results of the study indicate that the highest lead concentration in plants and soil was closest to the factory, which suggests that lead oxide fumes settle quite closely to the factory.