Sergio Alvarado

Neurodevelopmental effects in children associated with exposure to organophosphate pesticides: A systematic review

Many studies have investigated the neurodevelopmental effects of prenatal and early childhood exposures to organophosphate (OP) pesticides among children, but they have not been collectively evaluated. The aim of the present article is to synthesize reported evidence over the last decade on OP exposure and neurodevelopmental effects in children. The Data Sources were PubMed, Web of Science, EBSCO, SciVerse Scopus, SpringerLink, SciELO and DOAJ. The eligibility criteria considered were studies assessing exposure to OP pesticides and neurodevelopmental effects in children from birth to 18 years of age, published between 2002 and 2012 in English or Spanish. Twenty-seven articles met the eligibility criteria. Studies were rated for evidential consideration as high, intermediate, or low based upon the study design, number of participants, exposure measurement, and neurodevelopmental measures. All but one of the 27 studies evaluated showed some negative effects of pesticides on neurobehavioral development. A positive dose-response relationship between OP exposure and neurodevelopmental outcomes was found in all but one of the 12 studies that assessed dose-response. In the ten longitudinal studies that assessed prenatal exposure to OPs, cognitive deficits (related to working memory) were found in children at age 7 years, behavioral deficits (related to attention) seen mainly in toddlers, and motor deficits (abnormal reflexes) seen mainly in neonates. No meta-analysis was possible due to different measurements of exposure assessment and outcomes. Eleven studies (all longitudinal) were rated high, 14 studies were rated intermediate, and two studies were rated low. Evidence of neurological deficits associated with exposure to OP pesticides in children is growing. The studies reviewed collectively support the hypothesis that exposure to OP pesticides induces neurotoxic effects. Further research is needed to understand effects associated with exposure in critical windows of development.

Predictors of exposure to organophosphate pesticides in schoolchildren in the Province of Talca, Chile

BACKGROUND Few data exist in Latin America concerning the association between organophosphate (OP) urinary metabolites and the consumption of fruits and vegetables and other exposure risk variables in schoolchildren. METHODS We collected samples of urine from 190 Chilean children aged 6-12 years, fruits and vegetables, water and soil from schools and homes, and sociodemographic data through a questionnaire. We measured urinary dialkylphosphate (DAP) OP metabolites and OP pesticide residues in food consumed by these 190 children during two seasons: December 2010 (summer) and May 2011 (fall). We analyzed the relationship between urinary DAP concentrations and pesticide residues in food, home pesticide use, and residential location. RESULTS Diethylalkylphosphates (DEAP) and dimethylalkylphosphates (DMAP) were detected in urine in 76% and 27% of the samples, respectively. Factors associated with urinary DEAP included chlorpyrifos in consumed fruits (p<0.0001), urinary creatinine (p<0.0001), rural residence (p=0.02) and age less than 9 years (p=0.004). Factors associated with urinary DMAP included the presence of phosmet residues in fruits (p<0.0001), close proximity to a farm (p=0.002), home fenitrothion use (p=0.009), and season (p<0.0001). CONCLUSIONS Urinary DAP levels in Chilean school children were high compared to previously reported studies. The presence of chlorpyrifos and phosmet residues in fruits was the major factor predicting urinary DAP metabolite concentrations in children.

Long term energy-related environmental issues of copper production

Primary copper production is a major activity in the mining sector of several countries. However, it is highly energy-intensive and poses important environmental hazards. In the case of Chile, the worlds largest copper producer (40% of world total), we examine its energy consumption and energy-related environmental implications over a time horizon of 25 years. Concerning the latter, we focus on greenhouse-gas (GHG) emissions, one of the most debated environmental issues. This paper follows-up our previous report in which the current situation was analyzed and a particular technical option for improving the energy efficiency and concurrently reducing GHG emissions was discussed. Estimated reference or base (BS) and mitigation (MS) scenarios are developed for the period ending in 2020. The former assesses the energy demand projected in accordance with production forecasts and specific energy consumption patterns (assuming that energy efficiency measures are adopted ‘spontaneously’) with their resultant GHG emissions, while the latter assumes induced actions intended to reduce emissions by adopting an aggressive policy of efficient energy use. For the year 2020, the main results are: (i) BS, 1214t of CO2/ton of refined copper content (49% lower than in 1994); (ii) MS, 1037t of CO2/t of refined copper content (56% lower than in 1994). CO2 emissions have been estimated considering both fuel and electricity process requirements.

Energy and environmental implications of copper production

Primary copper production is a major activity in the mining sector. It is highly energy-intensive, ranking third in specific energy consumption (SEC) among the five major basic metals (aluminum, copper, iron, lead and zinc) and poses important environmental hazards. We examine the large discrepancy between theoretical (from thermodynamics) and actual (from empirical data) SECs and then describe relevant environmental issues, focusing on the most significant energy-related environmental impacts of primary copper production with emphasis on greenhouse-gas (GHG) emissions. An example of GHG energy-related abatement that concurrently improves energy use is presented.

Respiratory disease and particulate air pollution in Santiago Chile: contribution of erosion particles from fine sediments.

Air pollution in Santiago is a serious problem every winter, causing thousands of cases of breathing problems within the population. With more than 6 million people and almost two million vehicles, this large city receives rainfall only during winters. Depending on the frequency of storms, statistics show that every time it rains, air quality improves for a couple of days, followed by extreme levels of air pollution. Current regulations focus mostly on PM10 and PM2.5, due to its strong influence on respiratory diseases. Though more than 50% of the ambient PM10s in Santiago is represented by soil particles, most of the efforts have been focused on the remaining 50%, i.e. particulate material originating from fossil and wood fuel combustion, among others. This document emphasizes the need for the creation of erosion/sediment control regulations in Chile, to decrease respiratory diseases on Chilean polluted cities.

Energy–exergy optimization of comminution

The comminution process has exceedingly low efficiency because it is highly irreversible. An outline of energy analysis for comminution is presented. The application refers to an ore-processing plant, which consists of a series of crushers feeding a traditional ball mill that delivers products to a downstream metallurgical process. For optimization, the design characteristics are fixed, i.e. decision variables can only be operational parameters. The chosen decision variable is the size of the feed (F) to the mill. In practice, the mill operator may control the feed granulometry and keep the product size constant by using a constant ball charge. The objective cost function is the sum of energy costs at the crusher and mill, which depend only on F. The exergy consumption of the crusher and mill are evaluated using the Bond correlation, including pertinent correction factors. Optimization leads to a 10% saving in overall energy costs.

Polymorphism of Glutathione S-Transferase (GST) variants and its effect on distribution of urinary arsenic species in people exposed to low inorganic arsenic in tap water: an exploratory study.

ABSTRACT Glutathione S-tranferases (GST) are multigenic enzymes that have been associated with arsenic metabolism. The objective of this study was to evaluate the relationship between polymorphic variants of GST and urinary concentration of arsenic species in people exposed to low levels of arsenic. A cross-sectional study among 66 nonoccupationally exposed subjects, living in the city of Antofagasta, Chile. Polymorphic variants were analyzed by polymerase chain reaction (PCR) and arsenic species was determined by atomic absorption spectrometry. The effect of GST variants on arsenic concentration was evaluated using univariate and covariate-adjusted regressions. For both GSTT1 and GSTM1 there were no significant differences in detected arsenic relative species between carriers of the active and null polymorphic variants. There was nondefinitive evidence that polymorphic variants of GST play a role in arsenic metabolism in sample of the Chilean subjects studied.

Exergoeconomic optimization of a cogeneration plant

This paper illustrates, with a specifie example, the methodology presented in a previous paper for the exergoeconomic optimization of complex, multicomponent-multiproduct systems. The application selected is a cogeneration plant (the CGAM problem) to which methodologies developed by different authors have been applied previously. The CGAM problem involves a regenerative gas-turbine system and a heat-recovery steam generator producing 30 MW (net power) and 14 kg/sec of saturated steam at 2 MPa.

Minimum energy requirements in industrial processes: An application of exergy analysis

Exergy analysis is applied to the production of copper, wood pulp and steel. In Chile, these three sectors account for 56% of the total manufacturing industry-mining energy demands, with the following average specific energy uses: 25.6, 23.7 and 24.2 MJ/kg, respectively. The minimum energy requirements calculated are −90.6 MJ/kg for blister copper, −12.6 MJ/kg for pulp and 6.2 MJ/kg for steel ingots. These theoretical results show that the first two processes could be made energy self-sufficient and that there exists a large potential for improvement in energy efficiency in all three cases.

Modeling Chagas disease in Chile: From vector to congenital transmission

Chagaś disease is a human health problem in Latin America. It is highly prevalent in northern Chile between the Arica-Parinacota and Coquimbo regions, with reported incidence of 3-11/100000 inhabitants and mortality of 0.3-0.4/100000. The interruption of vector transmission was reported in 1999 by means of the elimination of the primary vector, Triatoma infestans, from human dwellings, thus the epidemiologic dynamics of this disease should be modified. Here we model the dynamics of Chagaś disease based on previous models for vector and congenital transmission, propose a model that includes both transmission forms and perform simulations. We derive useful relationships for the reproductive number (R0) showing that it may be expressed as the sum of the vector (R0V) and congenital (R0C) contributions. The vector contribution is larger than the congenital one; without the former Chagaś disease vanishes exponentially in two to three generations. Sensitivity analyses showed that the main parameters that intervene are the human bite rate, the density of vectors per human and the mortality rate of the insect vectors. Our model showed that the success of the eradication of Chagaś disease is based on the interruption of domestic transmission. Once this is obtained, the control strategies should focus on avoiding the domiciliation of wild vectors, re-colonization by the primary vector, and an adequate coverage of congenital case treatment.