RESUMEN
Taxes on sugar-sweetened beverages can promote health and raise revenue. Whether these taxes negatively impact domestic sugar producers, an argument often made by opponents, is understudied. We extended a simulation model based on a uniform specific volume-based tax of UAH 4/L in Ukraine. We estimated best- and worst-case scenarios for reductions in domestic sugar demand to be 162 and 23â000 metric tons. This is at worst â¼0.5% of current exports, meaning decreases in domestic demand could easily be absorbed by export markets given export trends. Due to highly protectionist sugar sector policy, sugar producers would not be able to fully substitute domestic sales revenues through increased export revenues, but the worst-case revenue gap was <0.5% of total sectoral output in recent years. Overall, introducing a tax on sugar-sweetened beverages in Ukraine is likely to have a very limited impact on domestic sugar producers.
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Bebidas Azucaradas , Humanos , Azúcares , Bebidas , Promoción de la Salud , Ucrania , Impuestos , ComercioRESUMEN
BACKGROUND: There is growing interest in fructosamine, glycated albumin, and 1,5-anhydroglucitol (1,5-AG) as alternative measures of hyperglycemia, particularly for use in settings where traditional measures (glucose and HbA1c) are problematic or where intermediate (2-4 weeks) glycemic control is of interest. However, reference intervals for these alternative biomarkers are not established. METHODS: We measured fructosamine, glycated albumin, and 1,5-AG in a community-based sample of US black and white adults who participated in the Atherosclerosis Risk in Communities (ARIC) Study. We calculated reference intervals, evaluated demographic differences, and derived cutoffs aligned with current diagnostic cutpoints for HbA1c and fasting glucose. RESULTS: In a healthy reference population of 1799 individuals (mean age, 55 years; 51% women; 15% black), the 2.5 and 97.5 percentiles, respectively, were 194.8 and 258.0 µmol/L for fructosamine, 10.7% and 15.1% for glycated albumin, and 8.4 and 28.7 µg/mL for 1,5-AG. Distributions differed by race, sex, and body mass index. Equivalent concentrations of fructosamine and glycated albumin corresponding to an HbA1c of 6.5% (96.5 percentile) were 270.2 µmol/L and 15.6%, respectively. Equivalent concentrations of fructosamine and glycated albumin corresponding to a fasting glucose of 126 mg/dL (93.9 percentile) were 261.7 µmol/L and 15.0%, respectively. CONCLUSIONS: The reference intervals for these biomarkers should inform their clinical use. Diagnostic cutpoint equivalents for fructosamine and glycated albumin could be useful to identify persons with hyperglycemia in settings where fasting glucose or HbA1c are not available or where the interpretation of these traditional measures is problematic.
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Desoxiglucosa/sangre , Fructosamina/sangre , Albúmina Sérica/metabolismo , Desoxiglucosa/normas , Femenino , Fructosamina/normas , Hemoglobina Glucada/análisis , Productos Finales de Glicación Avanzada , Humanos , Masculino , Estándares de Referencia , Albúmina Sérica/normas , Albúmina Sérica GlicadaAsunto(s)
Diabetes Mellitus Tipo 2/epidemiología , Diabetes Mellitus Tipo 2/prevención & control , Encuestas Nutricionales/tendencias , Estado Prediabético/epidemiología , Conducta de Reducción del Riesgo , Adulto , Anciano , Estudios Transversales , Diabetes Mellitus Tipo 2/diagnóstico , Femenino , Humanos , Masculino , Persona de Mediana Edad , Encuestas Nutricionales/métodos , Estado Prediabético/diagnóstico , Estados Unidos/epidemiología , Adulto JovenRESUMEN
Fiscal policies to improve diet are a promising strategy to address the increasing burden of non-communicable disease, the leading cause of death globally. Sugar-sweetened beverage taxes are the most implemented type of fiscal policy to improve diet. Yet taxes on food, if appropriately structured and applied across the food supply, may support a larger population-level shift towards a healthier diet. Designing these policies and guiding them through the legislative process requires evidence. Equity-oriented cost-effectiveness analyses that estimate the distribution of potential health and economic gains can provide this critical evidence. Taxes on less healthy foods are rarely modelled in low-income and middle-income countries.We describe considerations for modelling the effect of a food tax, which can provide guidance for food tax policy design. This includes describing issues related to the availability, reliability and level of detail of national data on dietary habits, the nutrient content of foods and food prices; the structure of the nutrient profile model; type of tax; tax rate; pass-through rate and price elasticity. Using the Philippines as an example, we discuss considerations for using existing data to model the potential effect of a tax, while also taking into account the political and food policy context. In this way, we provide a modelling framework that can help guide policy-makers and advocates in designing a food policy to improve the health and well-being of future generations in the Philippines and elsewhere.
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Países en Desarrollo , Alimentos , Humanos , Filipinas , Reproducibilidad de los Resultados , ImpuestosRESUMEN
BACKGROUND: 1,5-Anhydroglucitol (1,5-AG) is a novel biomarker of glycemic control proposed to monitor recent hyperglycemic excursions in persons with diabetes. The clinical utility of 1,5-AG outside of diagnosed diabetes is unclear, but it may identify people at high risk for diabetes and its complications. We compared associations of 1,5-AG with 2-h glucose for risk of major clinical complications. RESEARCH DESIGN AND METHODS: We prospectively followed 6644 Atherosclerosis Risk in Communities (ARIC) Study participants without diagnosed diabetes for incident diagnosed diabetes, chronic kidney disease, cardiovascular disease, and all-cause mortality for â¼20 years. We assessed associations of 1,5-AG and 2-h glucose (modeled categorically and continuously with restricted cubic splines) with adverse outcomes using Cox models and evaluated improvement in risk discrimination using Harrell's c-statistic. RESULTS: 1,5-AG <10 µg/mL was statistically significantly associated with incident diabetes (HR: 2.70, 95% CI 2.31, 3.15), and showed suggestion of association with the other outcomes compared to 1,5-AG ≥10 µg/mL. Continuous associations of 1,5-AG with outcomes displayed a clear threshold effect, with risk associations generally observed only <10 µg/mL. Comparing associations of 1,5-AG and 2-h glucose with outcomes resulted in larger c-statistics for 2-h glucose than 1,5-AG for all outcomes (difference in c-statistic [2-h glucose -1,5-AG] for diagnosed diabetes: 0.17 [95%CI, 0.15, 0.19]; chronic kidney disease 0.02 [95%CI 0.00, 0.05]; cardiovascular disease 0.03 [95%CI, 0.00, 0.06]; and all-cause mortality 0.04 [95%CI, 0.02, 0.06]). CONCLUSIONS: In this community-based population without diagnosed diabetes, low 1,5-AG was modestly associated with major clinical outcomes and did not outperform 2-h glucose.
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Aterosclerosis , Desoxiglucosa , Aterosclerosis/epidemiología , Glucosa , Humanos , Factores de RiesgoRESUMEN
CONTEXT: Weight loss is strongly recommended for overweight and obese adults with type 2 diabetes. Unintentional weight loss is associated with increased risk of all-cause mortality, but few studies have examined its association with cardiovascular outcomes in patients with diabetes. OBJECTIVE: To evaluate 2-year weight change and subsequent risk of cardiovascular events and mortality in established type 2 diabetes. DESIGN AND SETTING: The Action in Diabetes and Vascular Disease: Preterax and Diamicron-MR Controlled Evaluation was an international, multisite 2×2 factorial trial of intensive glucose control and blood pressure control. We examined 5 categories of 2-year weight change: >10% loss, 4% to 10% loss, stable (±<4%), 4% to 10% gain, and >10% gain. We used Cox regression with follow-up time starting at 2 years, adjusting for intervention arm, demographics, cardiovascular risk factors, and diabetes medication use from the 2-year visit. RESULTS: Among 10 081 participants with valid weight measurements, average age was 66 years. By the 2-year examination, 4.3% had >10% weight loss, 18.4% had 4% to 10% weight loss, and 5.3% had >10% weight gain. Over the following 3 years of the trial, >10% weight loss was strongly associated with major macrovascular events (hazard ratio [HR], 1.75; 95% confidence interval [CI], 1.26-2.44), cardiovascular mortality (HR, 2.76; 95% CI, 1.87-4.09), all-cause mortality (HR, 2.79; 95% CI, 2.10-3.71), but not major microvascular events (HR, 0.91; 95% CI, 0.61-1.36), compared with stable weight. There was no evidence of effect modification by baseline body mass index, age, or type of diabetes medication. CONCLUSIONS: In the absence of substantial lifestyle changes, weight loss may be a warning sign of poor health meriting further workup in patients with type 2 diabetes.
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Trayectoria del Peso Corporal , Enfermedades Cardiovasculares/etiología , Enfermedades Cardiovasculares/mortalidad , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Gliclazida/uso terapéutico , Hipertensión/tratamiento farmacológico , Indapamida/uso terapéutico , Perindopril/uso terapéutico , Adulto , Anciano , Enfermedades Cardiovasculares/prevención & control , Diabetes Mellitus Tipo 2/complicaciones , Diabetes Mellitus Tipo 2/mortalidad , Diabetes Mellitus Tipo 2/fisiopatología , Combinación de Medicamentos , Femenino , Estudios de Seguimiento , Humanos , Hipertensión/complicaciones , Hipertensión/mortalidad , Estilo de Vida , Masculino , Persona de Mediana Edad , Obesidad/complicaciones , Obesidad/tratamiento farmacológico , Obesidad/mortalidad , Sobrepeso/complicaciones , Sobrepeso/tratamiento farmacológico , Sobrepeso/mortalidad , Factores de Riesgo , Aumento de Peso/fisiología , Pérdida de Peso/fisiologíaRESUMEN
OBJECTIVE: To characterize long-term kidney disease trajectories in persons with and without diabetes in a general population. RESEARCH DESIGN AND METHODS: We classified 15,517 participants in the community-based Atherosclerosis Risk in Communities (ARIC) study by diabetes status at baseline (1987-1989; no diabetes, undiagnosed diabetes, and diagnosed diabetes). We used linear mixed models with random intercepts and slopes to quantify estimated glomerular filtration rate (eGFR) trajectories at four visits over 26 years. RESULTS: Adjusted mean eGFR decline over the full study period among participants without diabetes was -1.4 mL/min/1.73 m2/year (95% CI -1.5 to -1.4), with undiagnosed diabetes was -1.8 mL/min/1.73 m2/year (95% CI -2.0 to -1.7) (difference vs. no diabetes, P < 0.001), and with diagnosed diabetes was -2.5 mL/min/1.73 m2/year (95% CI -2.6 to -2.4) (difference vs. no diabetes, P < 0.001). Among participants with diagnosed diabetes, risk factors for steeper eGFR decline included African American race, APOL1 high-risk genotype, systolic blood pressure ≥140 mmHg, insulin use, and higher HbA1c. CONCLUSIONS: Diabetes is an important risk factor for kidney function decline. Those with diagnosed diabetes declined almost twice as rapidly as those without diabetes. Among people with diagnosed diabetes, steeper declines were seen in those with modifiable risk factors, including hypertension and glycemic control, suggesting areas for continued targeting in kidney disease prevention.
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Aterosclerosis/etiología , Diabetes Mellitus/fisiopatología , Tasa de Filtración Glomerular/fisiología , Anciano , Aterosclerosis/epidemiología , Aterosclerosis/fisiopatología , Presión Sanguínea/fisiología , Estudios de Cohortes , Complicaciones de la Diabetes/epidemiología , Complicaciones de la Diabetes/fisiopatología , Diabetes Mellitus/epidemiología , Diabetes Mellitus/patología , Progresión de la Enfermedad , Femenino , Humanos , Hipertensión/complicaciones , Hipertensión/epidemiología , Hipertensión/fisiopatología , Riñón/fisiopatología , Masculino , Persona de Mediana Edad , Insuficiencia Renal Crónica/complicaciones , Insuficiencia Renal Crónica/epidemiología , Características de la Residencia , Factores de RiesgoRESUMEN
BACKGROUND: In people with chronic kidney disease (CKD), HbA1c may be a problematic measure of glycemic control. Glycated albumin and fructosamine have been proposed as better markers of hyperglycemia in CKD. In the present study we investigated associations of HbA1c, glycated albumin, and fructosamine with fasting glucose by CKD categories. METHODS: A cross-sectional analysis was performed of 1665 Atherosclerosis Risk in Communities Study participants with diagnosed diabetes aged ≥65 years. Spearman's rank correlations (r) were compared and Deming regression was used to obtain root mean square errors (RMSEs) for the associations across CKD categories defined using estimated glomerular filtration rate and urine albumin:creatinine ratio. RESULTS: Correlations of HbA1c, glycated albumin, and fructosamine with fasting glucose were lowest in people with severe CKD (HbA1c r = 0.52, RMSE = 0.91; glycated albumin r = 0.39, RMSE = 1.89; fructosamine r = 0.41, RMSE = 1.87) and very severe CKD (r = 0.48 and RMSE = 1.01 for HbA1c; r = 0.36 and RMSE = 2.14 for glycated albumin; r = 0.36 and RMSE = 2.22 for fructosamine). Associations of glycated albumin and fructosamine with HbA1c were relatively similar across CKD categories. CONCLUSIONS: In older adults with severe or very severe CKD, HbA1c, glycated albumin, and fructosamine were not highly correlated with fasting glucose. The results suggest there may be no particular advantage of glycated albumin or fructosamine over HbA1c for monitoring glycemic control in CKD.
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Biomarcadores/sangre , Diabetes Mellitus/sangre , Hiperglucemia/sangre , Insuficiencia Renal Crónica/sangre , Anciano , Anciano de 80 o más Años , Aterosclerosis/sangre , Aterosclerosis/etiología , Glucemia/análisis , Servicios de Salud Comunitaria/estadística & datos numéricos , Estudios Transversales , Diabetes Mellitus/diagnóstico , Ayuno/sangre , Femenino , Fructosamina/sangre , Hemoglobina Glucada , Productos Finales de Glicación Avanzada , Humanos , Masculino , Insuficiencia Renal Crónica/complicaciones , Factores de Riesgo , Albúmina Sérica/análisis , Albúmina Sérica GlicadaRESUMEN
OBJECTIVE: There is suggestive evidence linking hypoglycemia with cardiovascular disease, but few data have been collected in a community-based setting. Information is lacking on individual cardiovascular outcomes and cause-specific mortality. RESEARCH DESIGN AND METHODS: We conducted a prospective cohort analysis of 1,209 participants with diagnosed diabetes from the Atherosclerosis Risk in Communities (ARIC) study (analytic baseline, 1996-1998). Severe hypoglycemic episodes were identified using first position ICD-9 codes from hospitalizations, emergency department visits, and ambulance calls through 2013. Cardiovascular events and deaths were captured through 2013. We used adjusted Cox regression models with hypoglycemia as a time-varying exposure. RESULTS: There were 195 participants with at least one severe hypoglycemic episode during a median fellow-up of 15.3 years. After severe hypoglycemia, the 3-year cumulative incidence of coronary heart disease was 10.8% and of mortality was 28.3%. After adjustment, severe hypoglycemia was associated with coronary heart disease (hazard ratio [HR] 2.02, 95% CI 1.27-3.20), all-cause mortality (HR 1.73, 95% CI 1.38-2.17), cardiovascular mortality (HR 1.64, 95% CI 1.15-2.34), and cancer mortality (HR 2.49, 95% CI 1.46-4.24). Hypoglycemia was not associated with stroke, heart failure, atrial fibrillation, or noncardiovascular and noncancer death. Results were robust within subgroups defined by age, sex, race, diabetes duration, and baseline cardiovascular risk. CONCLUSIONS: Severe hypoglycemia is clearly indicative of declining health and is a potent marker of high absolute risk of cardiovascular events and mortality.
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Enfermedad Coronaria/mortalidad , Diabetes Mellitus Tipo 2/complicaciones , Hipoglucemia/complicaciones , Neoplasias/mortalidad , Anciano , Glucemia/metabolismo , Índice de Masa Corporal , Colesterol/sangre , Enfermedad Coronaria/complicaciones , Femenino , Estudios de Seguimiento , Hospitalización , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Neoplasias/complicaciones , Estudios Prospectivos , Factores de Riesgo , Factores Socioeconómicos , Triglicéridos/sangreRESUMEN
BACKGROUND: No consensus on definitions of prediabetes exists among international organisations. Analysis of associations with different definitions and clinical complications can inform the comparative value of different prediabetes definitions. We compared the risk of future outcomes across different prediabetes definitions based on fasting glucose concentration, HbA1c, and 2 h glucose concentration during over two decades of follow-up in the community-based Atherosclerosis Risk in Communities (ARIC) study. We aimed to analyse the associations of definitions with outcomes to provide a comparison of different definitions. METHODS: We did a prospective cohort study of participants in the ARIC study who did not have diagnosed diabetes and who attended visit 2 (1990-92; n=10â844) and who attended visit 4 (1996-98; n=7194). ARIC participants were enrolled from four communities across the USA. Fasting glucose concentration and HbA1c were measured at visit 2 and fasting glucose concentration and 2 h glucose concentration were measured at visit 4. We compared prediabetes definitions based on fasting glucose concentration (American Diabetes Association [ADA] fasting glucose concentration cutoff 5·6-6·9 mmol/L and WHO fasting glucose concentration cutoff 6·1-6·9 mmol/L), HbA1c (ADA HbA1c cutoff 5·7-6·4% [39-46 mmol/mol] and International Expert Committee [IEC] HbA1c cutoff 6·0-6·4% [42-46 mmol/mol]), and 2 h glucose concentration (ADA and WHO 2 h glucose concentration cutoff 7·8-11·0 mmol/L). FINDINGS: Prediabetes defined using the ADA fasting glucose concentration cutoff (prevalence 4112 [38%] of 10â844 people; 95% CI 37·0-38·8) was the most sensitive for major clinical outcomes, whereas using the ADA HbA1c cutoff (2027 [19%] of 10â884 people; 18·0-19·4) and IEC HbA1c cutoff (970 [9%] of 10â844 people; 8·4-9·5), and the WHO fasting glucose concentration cutoff (1213 [11%] of 10â844 people; 10·6-11·8) were more specific. After demographic adjustment, HbA1c-based definitions of prediabetes had higher hazard ratios and better risk discrimination for chronic kidney disease, cardiovascular disease, peripheral arterial disease, and all-cause mortality than did fasting glucose concentration-based definitions (all p<0·05). The C-statistic for incident chronic kidney disease was 0·636 for ADA fasting glucose concentration clinical categories and 0·640 for ADA HbA1c clinical categories (difference -0·005, 95% CI -0·008 to -0·001). The C-statistics were 0·662 for ADA fasting glucose clinical concentration categories and 0·672 for ADA HbA1c clinical categories for atherosclerotic cardiovascular disease, 0·701 for ADA fasting glucose concentration clinical categories and 0·722 for ADA HbA1c clinical categories for peripheral arterial disease, and 0·683 for ADA fasting glucose concentration clinical categories and 0·688 for ADA HbA1c clinical categories for all-cause mortality. Prediabetes defined using the ADA HbA1c cutoff showed a significant overall improvement in the net reclassification index for cardiovascular outcomes and death compared with prediabetes defined with glucose-based definitions. ADA fasting glucose concentration clinical categories, WHO fasting glucose concentration clinical categories, and ADA and WHO 2 h glucose concentrations clinical categories were not significantly different in terms of risk discrimination for chronic kidney disease, cardiovascular outcomes, or mortality outcomes. INTERPRETATION: Our results suggest that prediabetes definitions using HbA1c were more specific and provided modest improvements in risk discrimination for clinical complications. The definition of prediabetes using the ADA fasting glucose concentration cutoff was more sensitive overall. FUNDING: US National Institutes of Health.
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Aterosclerosis/diagnóstico , Aterosclerosis/epidemiología , Estado Prediabético/diagnóstico , Estado Prediabético/epidemiología , Características de la Residencia , Anciano , Aterosclerosis/sangre , Glucemia/metabolismo , Estudios de Cohortes , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estado Prediabético/sangre , Pronóstico , Estudios Prospectivos , Factores de Riesgo , Estados Unidos/epidemiologíaAsunto(s)
Envejecimiento/fisiología , Aterosclerosis/diagnóstico , Aterosclerosis/etiología , Biomarcadores/metabolismo , Hiperglucemia/diagnóstico , Envejecimiento/sangre , Aterosclerosis/sangre , Aterosclerosis/epidemiología , Estudios Transversales , Femenino , Hemoglobina Glucada/metabolismo , Humanos , Hiperglucemia/sangre , Hiperglucemia/complicaciones , Hiperglucemia/epidemiología , Masculino , Persona de Mediana Edad , Características de la Residencia/estadística & datos numéricos , Factores de RiesgoRESUMEN
A series of m-xylene/NO(x) photooxidation experiments were conducted to determine the influence of light intensity and radiation spectrum on secondary organic aerosol (SOA) formation within the UC Riverside/CE-CERT environmental chamber. The environmental chamber is equipped with 80 115-W black lights and a variable voltage 200 kW argon arc lamp that emits a wavelength spectrum more similar to natural light. SOA formation increased significantly with light intensity, measured as the photolysis rate of NO2 to NO (k1), increased from 0.09 to 0.26 min(-1). The argon arc lamp produced approximately 20% more SOA than black lights at a k1 of 0.09 min(-1) for similar amounts of m-xylene consumed. These results may help explain the variation of SOA formation between environmental chambers and the differences between measured SOA in the ambient atmosphere versus environmental chamber predictions.
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Aerosoles/efectos de la radiación , Luz , Óxidos de Nitrógeno/química , Xilenos/química , Aerosoles/química , Cinética , Óxidos de Nitrógeno/efectos de la radiación , Oxidación-Reducción/efectos de la radiación , Fotólisis/efectos de la radiación , Xilenos/efectos de la radiaciónRESUMEN
Amines in fine particulate matter have been detected and quantified during ambient studies of winter inversions in Logan, UT, using aerosol mass spectrometry. Amine-related compounds account for 0.5-6 microg m(-3) of fine particulate mass during some wintertime periods. The amine contributions sometimes show a clear diurnal pattern, reaching peak concentrations during the middle of the nightwhile decreasing during the morning and afternoon. Smog chamber reactions show that the reaction of tertiary amines with nitrate radical can account for this behavior in the atmosphere. The lower bound reaction rate of trimethylamine and nitrate radical is estimated at 4.4 x 10(-16) cm3/molecules/s with a conversion rate to the aerosol phase of approximately 65%. This suggests that amines could be a contributor to secondary organic aerosol formation in areas where nitrate radical is a significant player in oxidation chemistry.
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Aerosoles/análisis , Aminas/análisis , Atmósfera/química , Metilaminas/análisis , Material Particulado/análisis , Aerosoles/química , Aminas/química , Espectrometría de Masas , Nitratos/química , UtahRESUMEN
The formation of secondary organic aerosol (SOA) from the photooxidation of xylene isomers (m-, p-, and o-xylenes) has been extensively investigated. The dependence of SOA aerosol formation on the structure of xylene isomers in the presence of NO was confirmed. Generally, SOA formation of p-xylene was less than that of m- and o-xylenes. This discrepancy varies significantly with initial NOx levels. In a NOx-free environment, the difference of aerosol formation between o- and p-xylenes becomes insignificant. Several chemical pathways for the SOA dependence on structure and NOx are explored, with the experimental findings indicating that organic peroxides may be a major key to explaining SOA formation from aromatic hydrocarbons.
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Óxidos de Nitrógeno/química , Peróxidos/química , Xilenos/química , Xilenos/efectos de la radiación , Aerosoles , Contaminantes Atmosféricos/química , Contaminantes Atmosféricos/efectos de la radiación , Oxidación-Reducción , FotoquímicaRESUMEN
Formation of secondary organic aerosol (SOA) from m-xylene photoxidation in the absence of NOx was investigated in a series of smog chamber experiments. Experiments were performed in dry air and in the absence of seed aerosol with H2O2 photolysis providing a stable hydroxyl radical (OH radical) source. SOA formation from this study is exceptionally higher than experiments with existence of NOx. The experiments with elevated HO2 levels indicate that organic hydroperoxide compounds should contribute to SOA formation. Nitrogen oxide (NO) is shown to reduce aerosol formation; the constant aerosol formation rate obtained before addition of NO and after consumption of NO strongly suggests that aerosol formation is mainlythrough reactions with OH and HO2 radicals. In addition, a density of 1.40 +/- 0.1 g cm(-3) for the SOA from the photooxidation of m-xylene in the absence of NOx has been measured, which is significantly higherthan the currently used unit density.
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Contaminantes Atmosféricos/química , Xilenos/química , Aerosoles , Contaminantes Atmosféricos/efectos de la radiación , Monóxido de Carbono/química , Peróxido de Hidrógeno/química , Radical Hidroxilo/química , Óxidos de Nitrógeno/química , Fotoquímica , Fotólisis , Xilenos/efectos de la radiaciónRESUMEN
Propene is widely used in smog chamber experiments to increase the hydroxyl radical (OH) level based on the assumption that the formation of secondary organic aerosol (SOA) from parent hydrocarbon is unaffected. A series of m-xylene/NO(x) photooxidation experiments were conducted in the presence of propene in the University of California CE-CERT atmospheric chamber facility. The experimental data are compared with previous m-xylene/N0(x) photooxidation work performed in the same chamber facility in the absence of propene (Song et al. Environ. Sci. Technol. 2005, 39, 3143-3149). The result shows that, for similar initial conditions, experiments with propene have lower reaction rates of m-xylene than those without propene, which indicates that propene reduces OH in the system. Furthermore, experiments with propene showed more than 15% reduction in SOA yield compared to experiments in the absence of propene. Additional experiments of m-xylene/ NO(x) with CO showed similar trends of suppressing OH and SOA formation. These results indicate that SOA from m-xylene/NO(x) photooxidation is strongly dependent on the OH level present, which provides evidence for the critical role of OH in SOA formation from aromatic hydrocarbons.