Seasonal trends of PM2.5 and PM10 in ambient air and their correlation in ambient air of Lucknow city, India

The PM₁₀ concentration (μg/m³) in Lucknow city at 4 locations in three different seasons ranged between 148.6–210.8 (avg. 187.2 ± 17.1) during summer, 111.8–187.6 (avg. 155.7 ± 22.7) during monsoon and 199.3–308.8 (avg. 269.3 ± 42.9) during winter while PM_2.5 ranged between 32.4–67.2 (avg. 45.6 ± 10.9), 25.6–68.9 (avg. 39.8 ± 4.6) and 99.3–299.3 (avg. 212.4 ± 55.0) during respective seasons. The mass fraction ratio of PM_2.5 ranged between 0.22–0.92 (avg. 0.42 ± 0.26) and was significantly high during winter season indicating their composition.     

Carbonyls in the urban atmosphere of Monterrey,Mexico: sources,exposure, and health risk

Characteristics and sources of carbonyls in the ambient urban atmosphere of Monterrey, Mexico, were studied from April 10, 2012 to March 12, 2013. A total of 184 samples were collected using silica-gel cartridges impregnated with DNPH during morning (08:00–12:00 h) and afternoon (15:00–19:00 h) sampling periods. Samples were analyzed using high-performance liquid chromatography with an UV detector. Acetaldehyde was the most abundant carbonyl with mean concentrations of 13.08, 21.26, 12.19, and 11.78 μg m^?3 for spring, summer, autumn, and winter, respectively. Corresponding seasonal concentrations of formaldehyde were 7.11, 10.42, 5.93, and 8.48 μg m^?3. Both carbonyls showed a clear seasonal pattern and exhibited significantly higher levels in summer. Formaldehyde showed higher concentrations during the morning sampling period for all seasons except autumn, whereas acetaldehyde showed higher levels during the morning sampling period in summer and winter but higher concentrations during the afternoon sampling period in spring and autumn. Meteorological parameters and criteria air pollutants were measured and correlated with measured carbonyls using a principal component analysis. Prevailing winds showed that carbonyl levels were influenced by sources located to the SSE (during spring and summer), which include industrial, vehicular, and area sources. During autumn and winter, prevailing winds were from the NNE. Health risk assessment results show that values for the integrated lifetime cancer risk and non-cancer risk exceed acceptable risk levels and that long-term exposure to both carbonyls may result in a significant risk of cancer and adverse health effects.     

Summer-autumn air pollution in León,Spain: changes in aerosol size distribution and expected effects on the respiratory tract

The temporal variation of aerosol size distribution in León, Spain, was analyzed with an optical spectrometer, in order to identify changes associated with the summer-autumn transition. For each hour and day of the week, we have studied the temporal variation of the particle number during the day. As the summer progresses, the total particle number increases from 1000?±?600 in August to 1500?±?1000 particles cm^?3 in October, mainly due to more intense road traffic after the summer holidays and to the beginning of the new academic year in the study area in September. The particle number was higher on weekdays than on weekends in September and October. However, in August the values were similar, due to lower activity in the city, coinciding with the main holiday period. The aerosol size distributions were bimodal. In the fine mode, both the highest concentration (573 particles cm^?3) and the lowest count median diameter (0.08 μm) were recorded in October. The contribution of particles from forest fires and Saharan dust intrusions had a negative impact on the air quality of the city during the summer. Considering the estimated respirable fraction in healthy adults (after the Standard ISO 7708:1995), on weekdays the highest values are obtained between 0600 and 1000 UTC (around 15 μg m^?3) and in the afternoon, between 1700 and 2000 UTC (around 12 μg m^?3), coinciding with the rush hour.     

Photochemical Production of Atmospheric Carbonyls in a Rural Area in Southern China

For the first time, ambient carbonyls were measured in a rural area in southern China from August 2012 to February 2013 to investigate their distribution characteristics and sources. Formaldehyde, acetaldehyde, and acetone were the three most abundant carbonyls, which accounted for 83–95 % of total seven carbonyls identified. The O₃ formation potential of carbonyls in summer (59.55 μg/m³) was approximately ten times greater than that (6.37 μg/m³) in winter, and calculated photolysis rates were significantly faster in summer than those in winter, suggesting intensive photochemical activities in summer. Seasonal and diurnal variations of carbonyls showed that (1) the concentration of total carbonyls in summer (12.62 ± 10.83 μg/m³) was approximately five times greater than that in winter (2.33 ± 0.90 μg/m³), and a similar trend applied to the three abundant carbonyls; (2) the average summer to winter (S/W) ratio of formaldehyde and acetaldehyde was 10–13, and the S/W ratio of acetone was ~2.59; and (3) the highest concentrations of the three carbonyls and total carbonyls occurred at 14:00–16:00 with high temperature and intensive sunlight, especially in summer. These variations provided direct evidence for significant photochemical production of ambient carbonyls. Average C₁/C₂ ratios (3.07 ± 1.62) in summer were much greater than those (1.28 ± 0.25) in winter, and average C₂/C₃ ratios (35.09 ± 58.67) in summer were significantly greater than those (4.75 ± 2.12) in winter, both cases indirectly implying positive photochemical productions in summer. Especially, strong correlations (R ² = 0.63–0.98) of temperature and sunlight intensity with the three abundant carbonyls and total carbonyls were observed, indicating a similar causal source such as significant photochemical production.     

Solar ultraviolet exposures at ground level in tree shade during summer in south east Queensland

Data are presented on the effect of the tree canopy transmittance in the visible waveband (VT), canopy width, height and height of the start of the tree canopy (CH) on the solar UV in tree shade on a horizontal plane at ground level during a Southern Hemisphere summer. Of these factors, the VT and CH have an influence on the UV irradiances in the tree shade. The shade ratios (UV in tree shade to that in full sun) for erythemal UV ranged from 0.71 to 0.42, 0.54 to 0.29 and 0.63 to 0.41 for morning, noon and afternoon, respectively, for the VT range of 0.4-1.0. Over the same VT range, the shade ratios for UVA ranged from 0.61 to 0.28, 0.50 to 0.22 and 0.49 to 0.29 for morning, noon and afternoon, respectively. The UV exposures in the tree shade decreased with the VT with a marginally higher decrease in the irradiances for the UVA compared to the erythemal UV. Despite the protection by the tree shade, significant UV in the tree shade of approximately 4 MED (minimum erythemal dose) were received for the latitude in this research on a cloud free summer day on a horizontal plane over a 2-h period centred about solar noon.     

The recommended Threshold Limit Values for heat exposure fail to maintain body core temperature within safe limits in older working adults

Purpose: The American Conference of Governmental and Industrial Hygienists (ACGIH®) Threshold Limit Values (TLV® guidelines) for work in the heat consist of work-rest (WR) allocations designed to ensure a stable core temperature that does not exceed 38°C. However, the TLV® guidelines have not been validated in older workers. This is an important shortcoming given that adults as young as 40 years demonstrate impairments in their ability to dissipate heat. We therefore evaluated body temperature responses in older adults during work performed in accordance to the TLV® recommended guidelines.

Methods: On three occasions, 9 healthy older (58 ± 5 years) males performed a 120-min work-simulated protocol in accordance with the TLV® guidelines for moderate-to-heavy intensity work (360 W fixed rate of heat production) in different wet-bulb globe temperatures (WBGT). The first was 120 min of continuous (CON) cycling at 28.0°C WBGT (CON[28°C]). The other two protocols were 15-min intermittent work bouts performed with different WR cycles and WBGT: (i) WR of 3:1 at 29.0°C (WR3:1[29°C]) and (ii) WR of 1:1 at 30.0°C (WR1:1[30°C]). Rectal temperature was measured continuously. The rate of change in mean body temperature was determined via thermometry (weighting coefficients: rectal, 0.9; mean skin temperature, 0.1) and direct calorimetry.

Results: Rectal temperature exceeded 38°C in all participants in CON[28°C] and WR3:1[29°C] whereas a statistically similar proportion of workers exceeded 38°C in WR1:1[30°C] (χ²; P = 0.32). The average time for rectal temperature to reach 38°C was: CON[28°C], 53 ± 7; WR3:1[29°C], 79 ± 11; and WR1:1[30°C], 100 ± 29 min. Finally, while a stable mean body temperature was not achieved in any work condition as measured by thermometry (i.e., >0°C·min^?1; all P<0.01), heat balance as determined by direct calorimetry was achieved in WR3:1[29°C] and WR1:1[30°C] (both P ≥ 0.08).

Conclusion: Our findings indicate that the TLV® guidelines do not prevent body core temperature from exceeding 38°C in older workers. Furthermore, a stable core temperature was not achieved within safe limits (i.e., ≤38°C) indicating that the TLV® guidelines may not adequately protect all individuals during work in hot conditions.     

Study on Airborne Heavy Metals in Industrialized Urban Area of Delhi,India

This study assessed the concentrations of airborne heavy metals (HMs) in particulate matter with a cutoff size of 10 µm (i.e., PM₁₀) in an industrialized urban area (Naraina Industrial Area) of New Delhi, India. The samples were collected from January to December, 2011. The annual mean concentrations of selected HMs were as follows As (0.002?±?0.002), Cd (0.030?±?0.020), Co (0.003?±?0.002), Cr (0.170?±?0.081), Cu (0.183?±?0.120), Fe (4.774?±?1.889), Mn (0.258?±?0.145), Ni (0.170?±?0.146), Pb (0.345?±?0.207) and Zn (1.806?±?1.042) µg/m³. The seasonal trend for HMs followed the order postmonsoon?>?winter?>?premonsoon?>?monsoon. Principal component analysis-multiple linear regression (PCA-MLR) suggested the three major emission sources: industrial emission (70?%), mobile and stationary combustion sources (16?%), and suspended/re-suspended dust (14?%). Mean seasonal concentrations of PM₁₀ exceeded both the 24-hour and annual Indian National Ambient Air Quality Standards (NAAQS) of 60 and 100 µg/m³, respectively, in all four seasons. Mean seasonal Ni concentrations in Delhi ambient air also exceeded the 24-h annual NAAQS of 0.020 µg/m³ during all four seasons. Mean Pb concentrations exceeded the annual NAAQS of 0.50 µg/m³ only during the post monsoon season. The high levels of Ni- and Pb-contaminated PM₁₀ would appear to present the possibility of significant health risks.     

Seasonal Variation and Health Risk Assessment of Polycyclic Aromatic Hydrocarbons in Miaoli City,Taiwan

The ambient PAHs levels in the downtown area of a traditional small city were analyzed for winter and summer seasons. A total of 16 PAHs in gaseous and particulate phase were quantified. The average gaseous PAHs were 2,189 ± 1,194 and 623.8 ± 545.1 ng/m³ in winter and summer seasons, respectively. For the PAHs in particulate phase, they were 40.32 ± 12.15 and 11.99 ± 5.63 ng/m³ in winter and summer seasons, respectively. These values were comparable to those reported for large cities or even higher. The estimated BaPeq was 12.32 ± 6.34 ng/m³. As low-molecular-weight PAHs primarily existed in gaseous phase, high-molecular-weight PAHs in particulate phase became a significant fraction of total particulate phase PAHs. Particulate phase PAHs was significantly inversely associated with the ambient temperature for each individual PAHs species. However, this relationship did not exist for high-molecular-weight PAHs in gaseous phase. The results indicated the photo-degradation of high-molecular-weight PAHs should warrant a further thoughtfully investigation.     

The impact of school-day variation in weight and height on National Child Measurement Programme body mass index-determined weight category in Year 6 children

Background In England, the National Child Measurement Programme (NCMP) annually measures the weight and height of Year 6 schoolchildren (age 10–11 years). While measurement protocols are defined, the time of measurement within the school day is not. This study examined the impact of school‐day variation in weight and height on NCMP body mass index (BMI)‐determined weight category in Year 6 children. Methods Standing height and weight were measured in morning and afternoon sessions in 74 children, boys (n= 34; height: 141.16 ± 7.45 cm; weight: 36.48 ± 9.46 kg, BMI: 18.19 ± 3.98 kg/m²) and girls (n= 40; height: 144.58 ± 7.66 cm; weight: 42.25 ± 11.29 kg; BMI: 19.97 ± 3.98 kg/m²) aged 11 ± 0.3 years. Results In the whole sample, height decreased (Mean =?0.51 cm, 95% CI: ?0.39 to ?0.64 cm, P= 0.01), weight did not change (Mdn = 36.40 to 36.35, P= 0.09) and BMI increased (Mdn = 18.04 to 18.13, P= 0.01). In girls weight increased (Mdn = 41.40 to 41.60, P= 0.01). BMI percentile increased (Mdn = 57th to 59.5th centile, P= 0.01). One girl increased in BMI category from morning to afternoon according to the clinical cut‐offs (≤2nd, >91st and >98th) and three girls increased BMI category according to the population monitoring cut‐offs (≤2nd, ≥85th, ≥95th). Conclusions School‐day variation in height (and in girls alone, weight) impact upon increased BMI and BMI percentile in afternoon versus morning measurements in Year 6 children. Although not reaching statistical significance, resultant variation in categorization at the individual level may lead to unwarranted follow‐up procedures being initiated. Further research with larger samples is required to further explore the impact of daily variability in height and weight upon both clinical and population monitoring BMI‐determined weight status categorization in the NCMP.     

Indoor air pollutant exposure and determinant factors controlling household air quality for elderly people in Hong Kong

This study investigated the levels and determinant factors of indoor air pollutants including fine particles (PM_2.5), nitrogen dioxide (NO₂), and formaldehyde (HCHO) in 55 households exclusively for the elderly in Hong Kong during summer and winter (Jul.–Sep. 2016 and Nov. 2016–Mar. 2017). The average concentrations of PM_2.5, NO₂, and formaldehyde were 25.3?±?15.0, 40.5?±?16.0, and 26.1?±?22.8 μg/m³ in summer and 34.2?±?19.0, 43.5?±?17.0, and 15.4?±?4.5 μg/m³ in winter, respectively. There were ~?50.3% of households exceeding the World Health Organization indoor air quality standard for PM_2.5 throughout the study, with ~?40.6 and ~61.0% of the households in summer and winter, respectively. The determinant factors for indoor PM_2.5 and NO₂ concentrations were identified as from incense burning and cooking. Cooking with suitable ventilation is an important factor to ease indoor pollutant concentrations. Both of PM_2.5 and NO₂ indoor concentrations showed good correlations with outdoor concentrations. Winter was observed with higher pollutant concentrations than summer except for formaldehyde concentrations. Major factors controlling indoor formaldehyde concentrations are temperature and humidity. The outcome will be useful for the development of future indoor air quality guidelines for Hong Kong.     

Characterization and Local Emission Sources for Ammonia in an Urban Environment

Ammonia levels were evaluated in the urban environment of Madrid City, Spain. A total of 110 samplers were distributed throughout the city. Vehicle traffic density, garbage containers and sewers were identified as local emission sources of ammonia. The average ammonia concentrations were 4.66?±?2.14 µg/m³ (0.39–11.23 µg/m³ range) in the winter and 5.30?±?1.81 µg/m³ (2.33–11.08 µg/m³ range) in the summer. Spatial and seasonal variations of ammonia levels were evaluated. Hotspots were located in the south and center of Madrid City in both winter and summer seasons, with lower ammonia concentrations located in the north (winter) and in the west and east (summer). The number of representative points that were needed to establish a reliable air quality monitoring network for ammonia was determined using a combined clustering and kriging approach. The results indicated that 40 samplers were sufficient to provide a reliable estimate for Madrid City.     

Columba livia as a Sentinel Species for the Assessment of Urban Air Genotoxicity

This study explored the comet assay as a possible tool to assess genotoxicity in erythrocytes of Columba livia to detect genotoxic effects induced by exposure to urban air pollution. Fieldwork was conducted between June 2004 and June 2005 in the city of Milan, Italy, by sampling pigeons in different areas almost twice a week. Six air contaminants—CO, PM10, NO₂, O₃ (ozone), SO₂, and C6H6—plus polycyclic aromatic hydrocarbons (PAHs) in fine particles, temperature, and ultraviolet index, were considered. Genotoxicity levels, expressed as %DNA migrated, tail moment, and damage index (DI), were always higher in wild pigeons than in pigeons living indoors (controls). Animals exposed to urban air showed significant differences from season to season, and the genotoxic parameters presented the highest values in summer (45.30% ± 1.40% %DNA migrated, 12.73 ± 0.80 tail moment, and 22.30 ± 0.15 × DI × 10⁻¹); regression analyses showed a positive relation between DI and O₃ concentrations (P < 0.001). The use of the comet assay DI parameter as a rapid assessment of incipient genotoxic risk by pollution, as measured in C. livia living in urban areas, is also discussed.     

Hypertension and Triglyceride Catabolism: Implications for the Hemodynamic Model of the Metabolic Syndrome

Objective: We sought to determine if hypertensive adults have a blunted triglyceride catabolic rate (TG K₂) and if related hemodynamic and vascular alterations are determinants of TG K₂.

Methods: Fasting levels of insulin, glucose, lipoproteins and plasma catecholamines were measured in 10 normotensive and 10 hypertensive adults. TG K₂ was determined by an intravenous fat tolerance test. Forearm blood flow, maximum forearm blood flow and minimal forearm vascular resistance were determined by strain gauge plethysmography. Vascular compliance and systemic hemodynamics were measured by computerized arterial pulse waveform analysis.

Results: Compared to normotensives, hypertensives had a significantly elevated blood pressure (145 ± 8/94 ± 11 versus 111 ± 15/74 ± 14 mm Hg, p < 0.001), systemic vascular resistance (1695 ± 441 versus 1172 ± 430 dynes × sec × cm^?5, p = 0.02) and reduced large vessel compliance (11.7 ± 3.6 versus 15.1 ± 3.1 ml/mm Hg × 100, p = 0.04). There were no significant group differences in TG K₂ (3.07 ± 2.01 versus 2.88 ± 2.12 mg/dL/min, p = 0.85) or other metabolic and anthropometric variables. TG K₂ was not predicted by the forearm vascular measures or the hemodynamic variables, but was correlated to waist/hip ratio (r = ?0.71, p = 0.001), fasting triglycerides (r = ?0.64, p = 0.003), and male gender (r = 0.56, p = 0.012). An enhanced TG K₂ was independently predicted by a reduced small vessel compliance (r = ?0.61, p = 0.006).

Conclusions: Elevated blood pressure per se and hypertension-related hemodynamic and vascular alterations are not associated with reduced TG K₂ or other metabolic abnormalities. Rather, aspects of the insulin resistance syndrome are closely related to abdominal adiposity. The independent association between small vessel compliance and TG K₂ deserves further investigation.     

Temporal Variation of Phthalic Acid Esters (PAEs) in Ambient Atmosphere of Delhi

Phthalic acid esters (PAEs) are a group of chemical species, ubiquitously present in the environment and pose a serious risk to humans. In the present study, the average concentrations of PAEs in PM₁₀ (particulate matter ≤?10 µm) are reported at a densely populated site in Delhi. The average concentration of PAEs was reported to be 703.1?±?36.2 ng m^?3 with slightly higher concentrations in winter than in summer; suggesting that sources are relatively stable over the whole year. The average concentration of PAEs was 35.7?±?30.5 ng m^?3 in winter, 35.4?±?27.0 ng m^?3 in summer, 3.4?±?1.5 ng m^?3 in monsoon and 7.5?±?5.2 ng m^?3 in post-monsoon. Principal component analysis was performed, which suggested that emissions were mainly due to plasticizers, cosmetics and personal care products, municipal solid waste, thermal power stations, industrial wastewater, cement plants and coke ovens.     

Bioremediation of Eutrophicated Water by <Emphasis Type="Italic">Acinetobacter Calcoaceticus</Emphasis>

Removal of phosphorus and nitrogen from eutrophicated water was carried out by in situ bioremediation. With the addition of Acinetobacter calcoaceticus, 65.0% ± 4.0% of total phosphorus (TP), 37.0% ± 4.0% of total nitrogen (TN), 75.0% ± 7.0% nitrite (NO₂ ⁻–N), and 87.0% ± 4.0% of ammonia (NH₄ ⁺–N) were removed. Furthermore, chlorophyll a removal in the inoculated treatments reached 83.7% ± 1.5%, and algae in the water was basically controlled.     

Trends in characteristics of 24-h urine samples and their relevance for human biomonitoring studies – 20 years of experience in the German Environmental Specimen Bank

To document trends in human exposure to environmental pollutants, the German Environmental Specimen Bank (ESB) has been routinely collecting and archiving 24-h urine samples from young adults at four sampling sites in Germany on an annual basis. For the purpose of normalizing measured analyte concentrations, urinary creatinine (UC), specific gravity (SG), conductivity (CON), and total urine volume (UV_tot) of 24-h urine samples have also been recorded. These parameters are however susceptible to variation over time, as well as within/among participants and normalization against them can thus affect the interpretation of data regarding exposure to environmental pollutants. To evaluate the influence of normalization against these parameters, we first sought to determine variations of these parameters with regard to differences between sexes and trends over time. We analysed data from 8619 urine samples collected from 1997 to 2016. We observed an inverse relation between UV_tot and UC, SG, and CON. We also found differences between sexes for UC, SG and CON, but not UV_tot. UC, SG, and CON showed significant decreasing trends over time in both sexes. In contrast, a significant increase of over 30% in UV_tot, independent of participant age and BMI, was revealed. This increase in UV_tot and the concomitant sample dilution is likely to have an impact on measured analyte concentrations in 24-h urine samples. Hence, normalization of urinary concentrations is warranted when interpreting time trends of human exposure. Next, urinary calcium (Ca²⁺) concentrations of ESB participants were used to demonstrate the effects of normalization against each of the four urine parameters. From 1997 to 2016, measured Ca²⁺ concentrations showed a statistically significant but scientifically implausible decrease. Normalization of Ca²⁺ concentrations against UV_tot (by calculating the total daily excretion), UC, or CON, but not SG, eliminated this decrease. Consistent with previous work, Ca²⁺ concentrations in urine and total daily Ca²⁺ excretion were higher for males than females. Normalization against UC, SG, or CON, however, attenuated this difference. Thus, to avoid misinterpretation in trend analysis and sex-specific excretion in 24-h urine samples, the calculation of the total daily excretion is recommended.     

Temporal Variation of Metals in Water,Sediment and Tissues of the European Chup (<Emphasis Type="Italic">Squalius cephalus</Emphasis> L.)

The aim of this study was to analyze seasonal variation of levels of Chromium (Cr), Manganese (Mn), Nickel (Ni), Copper (Cu), Zinc (Zn), Cadmium (Cd) and Lead (Pb) in water, sediment and tissues of Squalius cephalus (L., 1758) taken from five different stations chosen at Yamula Dam Lake (Kayseri, Turkey). Concentrations of metals were generally sorted as water<tissue<sediment. The highest concentration of metals in water was observed in the samples taken in the summer (Mn, 1.04 ± 0.15 mg L⁻¹; Ni, 0.42 ± 0.12 mg L⁻¹; Cu, 1.25 ± 0.88 mg L⁻¹; Zn, 3.61 ± 1.53 mg L⁻¹; Pb, 0.58 ± 0.09 mg L⁻¹). While the highest Zn (24.85 ± 21.82 μg g⁻¹) and Pb (10.89 ± 4.2 μg g⁻¹) concentrations in sediment were observed in the winter samples, the highest Mn concentration (167.2 ± 99.37 μg g⁻¹) was observed in the summer. Cd pollution was determined in sediment according to international criteria. The highest metal concentration in tissues was generally observed in the liver and the other tissues; following liver were gills and muscles. In liver tissues, while the highest accumulation of Zn (110.34 ± 13.1) and Mn (22.5 ± 14.85 μg g⁻¹), which are essential for the body, were observed in the winter, Pb (22.58 ± 7.83 μg g⁻¹) and Cd (11.77 ± 7.83 μg g⁻¹), which are toxic, were found to be higher in the summer. Also, concentrations of Mn, Cd and Pb in muscle tissues were found to be above the limits permitted.     

Avoiding the high Bonferroni penalty in genome‐wide association studies

A major challenge in genome‐wide association studies (GWASs) is to derive the multiple testing threshold when hypothesis tests are conducted using a large number of single nucleotide polymorphisms. Permutation tests are considered the gold standard in multiple testing adjustment in genetic association studies. However, it is computationally intensive, especially for GWASs, and can be impractical if a large number of random shuffles are used to ensure accuracy. Many researchers have developed approximation algorithms to relieve the computing burden imposed by permutation. One particularly attractive alternative to permutation is to calculate the effective number of independent tests, M_eff, which has been shown to be promising in genetic association studies. In this study, we compare recently developed M_eff methods and validate them by the permutation test with 10,000 random shuffles using two real GWAS data sets: an Illumina 1M BeadChip and an Affymetrix GeneChip^® Human Mapping 500K Array Set. Our results show that the simpleM method produces the best approximation of the permutation threshold, and it does so in the shortest amount of time. We also show that M_eff is indeed valid on a genome‐wide scale in these data sets based on statistical theory and significance tests. The significance thresholds derived can provide practical guidelines for other studies using similar population samples and genotyping platforms. Genet. Epidemiol. 34:100–105, 2010. © 2009 Wiley‐Liss, Inc.     

Beetroot Increases Muscle Performance and Oxygenation During Sustained Isometric Exercise,but Does Not Alter Muscle Oxidative Efficiency and Microvascular Reactivity at Rest

Objective: To examine the effects of beetroot juice (BRJ) on (i) in vivo skeletal muscle O₂ consumption (mVO₂) and microvascular reactivity at rest and (ii) muscle performance, muscle oxygenation, and mVO₂ during sustained isometric handgrip exercise (IHG).

Methods: Sixteen young males consumed, randomly, a nitrate-rich (8.1 mmol BRJnitrate) or nitrate-depleted (BRJplacebo) BRJ. After 2.5 hours, they performed an occlusion-reperfusion maneuver at rest, a 3-minute sustained IHG, and a sustained IHG to exhaustion with arterial occlusion. Changes in muscle oxygenated hemoglobin (O₂Hb), deoxygenated hemoglobin (HHb), microvascular red blood cell content (tHb), and mVO₂ were measured using near-infrared spectroscopy. Force output was recorded.

Results: During occlusion, the O₂Hb decline did not differ between BRJnitrate and BRJplacebo (magnitude: ?30.3 ± 1.6 vs. ?31.1 ± 1.5 ΔμΜ; slope: ?0.107 ± 0.007 vs. ?0.111 ± 0.007 μΜ second^?1). During reperfusion, all microvascular reactivity indices were not altered after BRJnitrate (e.g., O₂Hbslope: 1.584 ± 0.093 vs. 1.556 ± 0.072 μΜ second^?1). During the second and third minute of IHG, O₂Hb and tHb were higher in BRJnitrate versus BRJplacebo (p < 0.05), and force output was higher during the third minute (10.8 ± 0.7 vs. 9.5 ± 1.2 kg; p < 0.05); HHb did not differ between trials. In IHG with arterial occlusion, BRJnitrate prolonged the time to fatigue (94.1 ± 5.8 vs. 80.1 ± 3.3 seconds; p < 0.01), with no effects on O₂Hb decline (O₂Hbslope: ?0.226 ± 0.015 vs. ?0.230 ± 0.026 μΜ s^?1) and mVO₂ (14.1 ± 1.0 vs. 14.3 ± 1.6 μmol l^?1 minute^?1).

Conclusion: Acute BRJ ingestion in moderately trained individuals (i) did not alter in vivo skeletal muscle microvascular reactivity (index of microvascular function at rest) and basal oxidative efficiency, (ii) increased muscle oxygenation during IHG (possibly via enhanced O₂ delivery), and (iii) provided ergogenic benefits during sustained IHG with no effects on muscle oxidative efficiency. The ergogenic effects of BRJ appeared independent of its tissue perfusion benefits.