Influence of gastric residual assessment in preterm neonates on time to achieve enteral feeding (the GRASS trial)-Multi-centre, assessor-blinded randomised clinical trial.

PURPOSE: Gastric residual measurement is routinely performed in premature infants prior to feeding despite a lack of evidence of benefit. We aimed to evaluate if the exclusion of routine gastric residual measurement and evaluation has an impact on the time taken to achieve full enteral feeding in preterm neonates. METHODS: International multi-centre randomised controlled trial. Clinically stable, appropriate for gestational age infants between 26+0 and 30+6 weeks of gestation and less than 1.5 kg birth weight were eligible. Infants were randomised to the intervention arm (no monitoring of gastric aspirates) or control arm (routine care). Primary outcome was the achievement of enteral feeds of 100 ml/kg/day by day 5 of life. RESULTS: Ninety-five infants were recruited with 88 included in an intention-to-treat analysis, 45 in the intervention arm and 43 in the control arm. There was no imbalance in baseline characteristics. Thirty-three (73.3%) infants in the intervention group and 32 infants (74.4%) in the control group reached full feeds by day 5 of life (p = 0.91) with no difference in median time to full feeds. There were no statistically significant differences in survival or the major morbidities of prematurity. CONCLUSION:  There was no difference in time to attainment of enteral feeds of 100 ml/kg/day in premature infants when gastric residuals were not monitored. In the absence of a clinical benefit to routine monitoring, it may be appropriate to discontinue this practice and only monitor residuals when clinical concern of feeding intolerance or gastrointestinal pathology arises in this group of patients. TRIAL REGISTRATION:  NCT03111329- https://clinicaltrials.gov/ . Registered 06/04/2017. WHAT IS KNOWN: • Previous randomized trials have shown little benefit to the performance of routine assessment of gastric residuals in preterm infants. Despite this, they continue to be performed due to concerns from observational data regarding development of NEC. Meta-analysis to date has failed to answer the question regarding NEC. WHAT IS NEW: • In very low birth weight infants who are fed using modern feeding practice of faster feed advancement, to minimize use of central access and parenteral nutrition, exclusion of routine checks of gastric residuals did not increase the proportion of infants reaching full enteral feeds by day 5. No harm was seen when residual checks were not performed. • In the absence of a clinical benefit to the routine performance of gastric residuals in very low birth weight infants, it may be appropriate to discontinue their use and instead check residuals when clinical concern of pathology arises.

Using food fortification to improve vitamin D bioaccessibility and intakes.

Vitamin D intakes and status are low in many countries due to seasonal UVB exposure variation and the fact that few foods are naturally vitamin D rich. Data modelling studies show that vitamin D intakes increase with food fortification, and countries with mandatory fortification policies have higher vitamin D intakes and status compared to countries without. While many foods can be vitamin D fortified, vitamin D bioavailability differs depending on fortification methods, food structure and composition. Randomised controlled trials (RCT) report that vitamin D2 bioavailability varies between foods, whereas vitamin D3 is bioavailable from many foods. In vitro studies suggest that altering the lipid composition of fortified foods increases vitamin D3 absorption. Olive oil increased vitamin D3 absorption during in vitro digestion compared to other dietary oils. Additionally, when vitamin D3 was incorporated into micelles formed from in vitro digestion of olive oil, more vitamin D3 was absorbed compared to other dietary oils. However, in a human postprandial study, a preformed vitamin D3 micelle dairy drink did not increase vitamin D3 absorption, and a vitamin D3 olive dairy drink increased vitamin D3 absorption in vitamin D insufficient participants only. Action is urgently needed to improve vitamin D intakes and status worldwide. Food fortification improves vitamin D intakes; however, fortification strategies unique to each country are needed. This review will synthesise the literature describing data modelling and intervention trials that assess the safety and efficacy of vitamin D fortification strategies, and those manipulating food composition to alter vitamin D bioavailability from fortified foods. Additionally, RCT examining the impact of vitamin D fortification strategies on vitamin D intakes and status over time are reviewed.

The P4 study: Subsequent pregnancy maternal physiology after hypertensive and normotensive pregnancies.

OBJECTIVES: Hypertensive disorders of pregnancy are associated with subsequent increased risk of cardiometabolic disease. Adverse cardiometabolic measures are noted soon after hypertensive versus normotensive pregnancy (NP); to what degree these persist into a subsequent pregnancy (SP) is unknown. This study aimed to assess women's physiology early in SP after hypertensive pregnancy (HP: preeclampsia or gestational hypertension) or NP and compare SP to 6 months postpartum findings from the index pregnancy. STUDY DESIGN: Prospective sub-study of the P4 (Postpartum, Physiology, Psychology and Paediatric) observational cohort. Measurements six months after NP versus HP, and the SP at 11-13 weeks gestation. MAIN OUTCOME MEASURES: Blood pressure (BP), blood and urine tests (urine ACR, HOMA-IR, LDL cholesterol), body composition, and contribution of maternal characteristics and inter-pregnancy factors to BP and body fat (FM%) in SP. RESULTS: 49 women (34 NP, 15 HP). In the SP, post-HP women had higher BP (112/70 mmHg HP vs 102/64 mmHg NP; p < .001), with no significant drop from six months postpartum to early SP. On regression analysis, systolic and diastolic BP at 6-months were the major predictors for SP systolic (p < 0.001) and diastolic (p = 0.009) BP respectively in the SP. Longer interpregnancy interval and increased FM% 6-months postpartum were associated with higher SP FM% (p < 0.001). CONCLUSIONS: BP and body fat six months postpartum were similar early in the SP for HP group, and postpartum BP and FM% were major predictors of their corresponding SP measurements. Postpartum/inter-pregnancy intervention programs to improve these cardiometabolic risk markers might help improve women's long-term health and require investigation.

Maternal macro- and micronutrient intake six months after hypertensive versus normotensive pregnancy: is poor diet quality contributing to future cardiometabolic disease risk?

BACKGROUND: Hypertensive pregnancy is associated with increased long-term cardiometabolic disease risk. Assessing dietary intake patterns after hypertensive (HP) versus normotensive pregnancy (NP) may provide insights into the mechanism of this risk. METHODS: This study was a prospective sub-study of the P4 (Postpartum, Physiology, Psychology and Paediatrics) cohort. Women were studied six months after NP versus HP (preeclampsia or gestational hypertension). Dietary energy, macronutrient and micronutrient intake were measured using a three-day food diary (FoodWorks™) and assessed against Australian and New Zealand Nutrient Reference Values to determine nutritional adequacy. Comparisons between breastfeeding and non-breastfeeding women were assessed, and linear regression modelling (using hypertensive status, breastfeeding status, and demographic/pregnancy variables) performed to assess predictors of energy intake. RESULTS: Seventy-four women (60 NP, 14 HP) were included. HP women had higher mean body mass index (p = 0.02) and lower breastfeeding rates (29% HP versus 83% NP, p < 0.001) compared to NP women. Twenty-four-hour energy intake and total fat intake were 17% and 20% lower after HP respectively. Nutrient deficiencies were prevalent across all participants, however more HP women had inadequate magnesium, calcium and phosphorus intake. Breastfeeding women had significantly increased energy (17%), carbohydrate (15%) and total fat intake (21%), and increased vitamin A, vitamin E, riboflavin, magnesium and iron intake compared to non-breastfeeding women. HP and breastfeeding status were independent predictors of energy intake. CONCLUSIONS: HP women had lower micronutrient intake and greater prevalence of nutritional inadequacy compared to NP women, reflecting poorer diet quality and potentially contributing to future increased cardiometabolic disease risk.

An in vitro investigation into the release of fugitive medical aerosols into the environment during manual ventilation.

BACKGROUND: During manual resuscitation, nebulizer therapy may be used to deliver therapeutics to patients in respiratory distress. However, the devices used to generate and deliver these medical aerosols have the potential to release these therapeutics into the local environment and expose caregivers to unwanted medical aerosols. AIM: To quantify the levels of fugitive medical aerosol released into the environment during aerosol drug delivery using a manual resuscitation bag with and without filtration. METHODS: Time-varying fugitive aerosol concentrations were measured using an aerodynamic particle sizer placed at a position designed to mimic a caregiver. Two nebulizer types were assessed, a vibrating mesh nebulizer and a jet nebulizer. The aerosol dose delivered to the simulated patient lung was also quantified. FINDINGS: Filtration of the exhalation port of the manual resuscitation bag was seen to reduce fugitive medical aerosols to ambient levels for both nebulizer types. The vibrating mesh nebulizer delivered the greatest quantity of aerosol to the simulated adult patient (18.44 ± 1.03% versus 3.64 ± 0.26% with a jet nebulizer). CONCLUSIONS: The results highlight the potential for exposure to fugitive medical aerosols released during the delivery of aerosol therapy with a manual resuscitation bag and also the potential for significant variation in patient lung dose depending on nebulizer type.

Central catheter removal timing and growth patterns in preterm infants.

BACKGROUND: Early discontinuation of total parenteral nutrition (TPN) at 100 ml/kg/day of enteral feeds, compared with 140 ml/kg/day, led to significant delay in time to regain the birth weight in very low birth weight infants (birth weight < 1500 g, VLBW). Our aim was to compare the growth of infants in relation with timing of TPN discontinuation up to 2 years corrected gestational age (CGA). METHODS: Posttrial follow-up study using review of paper medical records. Participants of the randomized controlled trial studying effect of early parenteral nutrition discontinuation on time to regain birth weight in VLBW infants were included. Growth parameters inclusive of weight, length, and occipital-frontal circumference (OFC) were collected. Z-scores were calculated at five predefined time points-birth, 0-11 weeks CGA, 12-35 weeks CGA, 36-60 weeks CGA, and 61-96 weeks CGA and compared for control and intervention groups. RESULTS: Regarding weight, we found lower mean Z-score in the intervention group between 0 and 11 weeks CGA, with larger difference in extremely low birth weight infants (birth weight < 1000 g, ELBW), but this did not reach the statistical significance. Regarding length, the same difference, slightly delayed to 35 weeks CGA was observed and reached statistical significance for ELBW infants between 12 and 35 weeks CGA. There was no difference in OFC mean Z-scores at any timepoint. CONCLUSIONS: The discontinuation of TPN at 100 ml/kg/day showed significantly lower Z-score for length in ELBW infants between 12 and 35 weeks CGA. There were no differences in Z-scores by 2 years CGA.

Don't go chasing artificial waterfalls: Artificial line limits and cascading failures in power grids.

Research on cascading failures in power-transmission networks requires detailed data on the capacity of individual transmission lines. However, these data are often unavailable to researchers. Consequently, line limits are often modeled by assuming that they are proportional to some average load. However, there is scarce research to support this assumption as being realistic. In this paper, we analyze the proportional loading (PL) approach and compare it to two linear models that use voltage and initial power flow as variables and are trained on the line limits of a real power network that we have access to. We compare these artificial line-limit methods using four tests: the ability to model true line limits, the damage done during an attack, the order in which edges are lost, and accuracy ranking the relative performance of different attack strategies. We find that the linear models are the top-performing method or are close to the top in all the tests we perform. In comparison, the tolerance value that produces the best PL limits changes depending on the test. The PL approach was a particularly poor fit when the line tolerance was less than two, which is the most commonly used value range in cascading failure research. We also find indications that the accuracy of modeling line limits does not indicate how well a model will represent grid collapse. The findings of this paper provide an understanding of the weaknesses of the PL approach and offer an alternative method of line-limit modeling.

IgG4 Related Disease, A Case of Large Vessel Vasculitis

Aim This report describes a case of large vessel vasculitis highlighting diagnostic and therapeutic challenges. It describes the use of the B cell depleting agent Rituximab in this setting. This is the case of a 50 year old lady with bipolar disorder presenting with lower limb pain. Method PET CT and CT angiography were employed in the diagnosis of a large vessel vasculitic process. Serum IgG4 was elevated. Histological sampling was not clinically feasible. A presumptive diagnosis of IgG4 related disease was made. Results The patient responded well to steroids and later rituximab. A prompt taper of steroids was required due to labile mood and Rituximab proved to be effective in this case as a maintenance therapy. Conclusion This case demonstrates that a combination of clinical findings, laboratory results and radiological imaging may be necessary for diagnosis for IgG4 related disease, especially in the absence of a histological diagnosis. Rituximab was used in this case as a maintenance therapy allowing for a relatively rapidly reducing course of steroids.

Characterising urban zinc generation to identify surface pollutant hotspots in a low intensity rainfall climate.

Characterising stormwater runoff quality provides useful insights into the dynamics of pollutant generation and wash off rates. These can be used to prioritise stormwater management strategies. This study examined the effects of a low intensity rainfall climate on zinc contributions from different impermeable urban surface types. First flush (FF) and steady state samples were collected from seven different surfaces for characterisation, and the data were also used to calibrate an event-based pollutant load model to predict individual 'hotspot' surfaces across the catchment. Unpainted galvanised roofs generated very high concentrations of zinc, primarily in the more biologically available dissolved form. An older, unpainted galvanised roof had FF concentrations averaging 32,338 µg/L, while the new unpainted roof averaged 4,782 µg/L. Roads and carparks also had elevated zinc, but FF concentrations averaged only 822-1,584 µg/L. Modelling and mapping expected zinc loads from individual impermeable surfaces across the catchment identified specific commercial roof surfaces to be targeted for zinc management. The results validate a policy strategy to replace old galvanised roof materials and avoid unpainted galvanised roofing in future urban development for better urban water quality outcomes. In the interim, readily-implemented treatment options are required to help mitigate chronic zinc impacts on receiving waterways.

Patterns of dairy food intake, body composition and markers of metabolic health in Ireland: results from the National Adult Nutrition Survey.

BACKGROUND: Studies examining the association between dairy consumption and metabolic health have shown mixed results. This may be due, in part, to the use of different definitions of dairy, and to single types of dairy foods examined in isolation. OBJECTIVE: The objective of the study was to examine associations between dairy food intake and metabolic health, identify patterns of dairy food consumption and determine whether dairy dietary patterns are associated with outcomes of metabolic health, in a cross-sectional survey. DESIGN: A 4-day food diary was used to assess food and beverage consumption, including dairy (defined as milk, cheese, yogurt, cream and butter) in free-living, healthy Irish adults aged 18-90 years (n=1500). Fasting blood samples (n=897) were collected, and anthropometric measurements taken. Differences in metabolic health markers across patterns and tertiles of dairy consumption were tested via analysis of covariance. Patterns of dairy food consumption, of different fat contents, were identified using cluster analysis. RESULTS: Higher (total) dairy was associated with lower body mass index, %body fat, waist circumference and waist-to-hip ratio (P<0.001), and lower systolic (P=0.02) and diastolic (P<0.001) blood pressure. Similar trends were observed when milk and yogurt intakes were considered separately. Higher cheese consumption was associated with higher C-peptide (P<0.001). Dietary pattern analysis identified three patterns (clusters) of dairy consumption; 'Whole milk', 'Reduced fat milks and yogurt' and 'Butter and cream'. The 'Reduced fat milks and yogurt' cluster had the highest scores on a Healthy Eating Index, and lower-fat and saturated fat intakes, but greater triglyceride levels (P=0.028) and total cholesterol (P=0.015). CONCLUSION: Overall, these results suggest that while milk and yogurt consumption is associated with a favourable body phenotype, the blood lipid profiles are less favourable when eaten as part of a low-fat high-carbohydrate dietary pattern. More research is needed to better understand this association. CONCLUSION: Overall, these results suggest that although milk and yogurt consumption is associated with a favourable body phenotype, the blood lipid profiles are less favourable when eaten as part of a low-fat high-carbohydrate dietary pattern. More research is needed to better understand this association.

Use of plasma human herpesvirus-8 viral load measurement: evaluation of practice in three UK HIV treatment centres.

A retrospective audit of plasma human herpesvirus-8 (HHV-8) viral load testing was performed in three HIV treatment centres over 24 months. Reasons for testing (360 tests) were: symptoms of systemic inflammatory response syndrome (SIRS) (fever, lymphadenopathy and raised inflammatory markers); monitoring in known HHV-8 pathology other than Kaposi sarcoma (KS); investigation of known/suspected KS, and other/no reason. Of patients with multicentric Castleman disease (MCD), 14/16 (88%) had detectable plasma HHV-8, as did 27/45 (60%) with biopsy proven or clinically confirmed KS, and 6/19 (32%) with lymphoma. Neither of the two patients with MCD and no detectable HHV-8 had SIRS symptoms at the time of the test. There was wide variation between centres in the indications prompting HHV-8 testing, with a more conservative approach resulting in a higher proportion of positive results. Measuring plasma HHV-8 in the absence of SIRS symptoms, established HHV-8 disease monitoring, or confirmed/suspected KS is unlikely to yield detectable HHV-8 thus allowing potential cost savings.

A novel modelling framework to prioritize estimation of non-point source pollution parameters for quantifying pollutant origin and discharge in urban catchments.

Stormwater runoff in urban catchments contains heavy metals (zinc, copper, lead) and suspended solids (TSS) which can substantially degrade urban waterways. To identify these pollutant sources and quantify their loads the MEDUSA (Modelled Estimates of Discharges for Urban Stormwater Assessments) modelling framework was developed. The model quantifies pollutant build-up and wash-off from individual impervious roof, road and car park surfaces for individual rain events, incorporating differences in pollutant dynamics between surface types and rainfall characteristics. This requires delineating all impervious surfaces and their material types, the drainage network, rainfall characteristics and coefficients for the pollutant dynamics equations. An example application of the model to a small urban catchment demonstrates how the model can be used to identify the magnitude of pollutant loads, their spatial origin and the response of the catchment to changes in specific rainfall characteristics. A sensitivity analysis then identifies the key parameters influencing each pollutant load within the stormwater given the catchment characteristics, which allows development of a targeted calibration process that will enhance the certainty of the model outputs, while minimizing the data collection required for effective calibration. A detailed explanation of the modelling framework and pre-calibration sensitivity analysis is presented.

Early Childhood Dental Problems: Classification Tree Analyses of 2 Waves of an Infant Cohort Study.

Investigations into the wider bioecological understanding of dental problems in early childhood are limited in national surveys. Classification tree analysis (CTA) was used to explore multilevel interactions among key aspects of child and primary caregiver (PCG) psychosocial and physical health affecting dental problems in preschool children. Data were derived from the Growing Up in Ireland study, a nationally representative sample of 9-mo-olds (N = 11,134) in 2007/2008 followed up at age 3 y (N = 9,793) in 2010/2011. Analysis included PCG reports of children's dental problems, general health, temperament, emotional and behavioral difficulties, and their own general health, stress and depression, relationship, and sociodemographic variables. Misclassification costs were specified for the model by applying a higher penalty for misclassifying those with a dental problem (minority class). Logistic regression analyses were carried out for comparison. Dental problems were reported among 302 infants (2.7%) at 9 mo of age and 493 children (5.0%) at 3 y. CTA identified infant temperament (Infant Characteristics Questionnaire unpredictable) as the primary predictor of dental problems at 9 mo and child global health at 3 y of age. First-level predictors were PCG depression score and use of a soother at 9 mo and PCG ethnicity and unscheduled hospital visits at 3 y of age. Regression analyses results supported the most important predictors at 9 mo and 3 y of age. The CTA model for 9-mo-old infants had a specificity of 90.4%, sensitivity of 31.2%, and overall accuracy of 88.8% while that for 3-y-olds had a specificity of 58.5%, sensitivity of 66%, and overall accuracy of 59%. Key aspects of infant/child and PCG health, as well as psychosocial characteristics associated with reported dental problems, should be considered in future multidisciplinary approaches to child health. Knowledge Transfer Statement: The results of this data analysis should help raise awareness among clinicians of how primary caregiver and child psychosocial and general health factors are associated with early childhood dental problems, even before the primary dentition is complete. Classification tree analysis visually demonstrates how factors such as infant temperament (9 mo) and child global health (3 y) can interact at multiple levels and affect different subgroups of the child population. Future intervention strategies for oral health should involve consideration of the psychological and general health characteristics of the young child and PCG at both the patient and population levels. This knowledge could assist decision makers adopt an integrated multidisciplinary approach in formulating a coherent oral health policy for preschool children.

Implementation of safe sleep practices in the neonatal intensive care unit.

OBJECTIVE: To increase the percentage of eligible infants engaging in safe sleep practices (SSP) in two level III neonatal intensive care units (NICUs) in the Boston, Massachusetts area. STUDY DESIGN: On the basis of eligibility criteria (⩾34 weeks or ⩾1800 g without acute medical conditions), all infants were eligible for two sleep practices: SSP or NICU therapeutic positioning (NTP) depending on their gestational age, weight, clinical illness and need for therapeutic interventions. Compliance with SSP was defined as: (1) supine positioning, (2) in a flat crib with no incline, (3) without positioning devices and (4) without toys, comforters or fluffy blankets. NTP comprised usual NICU care. Nursing education was comprised of a web-based learning module and in-person teaching sessions with a study team member. Double-sided crib cards (SSP one side and NTP on the other) were attached to the bedside of every infant. Pre- and postintervention audits of all infants were carried out at both study sites. We compared compliance across all time points using generalized estimating equations to account for correlated data (SAS v9.3, Cary, NC, USA). RESULT: Of 755 cases, 395 (52.3%) were assessed to be eligible for SSP. From the pre- to post-intervention period, there was a significant improvement in overall compliance with SSP (25.9 to 79.7%; P-value<0.001). Adherence to each component of SSP also improved significantly following the intervention. CONCLUSION: Safe infant sleep practices can be integrated into the routine care of preterm infants in the NICU. Modeling SSP to families far in advance of hospital discharge may improve adherence to SSP at home and reduce the risk of sleep-related morbidity and mortality in this vulnerable population of infants.

Impact of chronic congestive heart failure on pharmacokinetics and vasomotor effects of infused nitrite.

BACKGROUND AND PURPOSE: Nitrite (NO2⁻) has recently been shown to represent a potential source of NO, in particular under hypoxic conditions. The aim of the current study was to compare the haemodynamic effects of NO2⁻ in healthy volunteers and patients with stable congestive heart failure (CHF). EXPERIMENTAL APPROACH: The acute haemodynamic effects of brachial artery infusion of NO2⁻ (0.31 to 7.8 µmol·min⁻¹) was assessed in normal subjects (n = 20) and CHF patients (n = 21). KEY RESULTS: NO2⁻ infusion was well tolerated in all subjects. Forearm blood flow (FBF) increased markedly in CHF patients at NO2⁻ infusion rates which induced no changes in normal subjects (ANOVA: F = 5.5; P = 0.02). Unstressed venous volume (UVV) increased even with the lowest NO2⁻ infusion rate in all subjects (indicating venodilation), with CHF patients being relatively hyporesponsive compared with normal subjects (ANOVA: F = 6.2; P = 0.01). There were no differences in venous blood pH or oxygen concentration between groups or during NO2⁻ infusion. Venous plasma NO2⁻ concentrations were lower in CHF patients at baseline, and rose substantially less with NO2⁻ infusion, without incremental oxidative generation of nitrate, consistent with accelerated clearance in these patients. Plasma protein-bound NO concentrations were lower in CHF patients than normal subjects at baseline. This difference was attenuated during NO2⁻ infusion. Prolonged NO2⁻ exposure in vivo did not induce oxidative stress, nor did it induce tolerance in vitro. CONCLUSIONS AND IMPLICATIONS: The findings of arterial hyper-responsiveness to infused NO2⁻ in CHF patients, with evidence of accelerated transvascular NO2⁻ clearance (presumably with concomitant NO release) suggests that NO2⁻ effects may be accentuated in such patients. These findings provide a stimulus for the clinical exploration of NO2⁻ as a therapeutic modality in CHF.

Assessment of the ability of seaweed extracts to protect against hydrogen peroxide and tert-butyl hydroperoxide induced cellular damage in Caco-2 cells.

The ability of brown seaweed extracts, Ascophyllum nodosum, Laminaria hyperborea, Pelvetia canaliculata, Fucus vesiculosus and Fucus serratus to protect against tert-butyl hydroperoxide (tert-BOOH) induced stress in Caco-2 cells was investigated. Oxidative stress was determined by measuring alteration in the enzymatic activity of catalase (CAT) and superoxide dismutases (SOD) and cellular levels of glutathione (GSH). L. hyperborea, P. canaliculata and F. serratus significantly protected against tert-BOOH induced SOD reduction but did not protect against the reduction in CAT activity or the increased cellular levels of GSH. The ability of F. serratus and F. vesiculosus to protect against H(2)O(2) and tert-BOOH induced DNA damage was also assessed. The DNA protective effects of the two seaweed extracts was compared to those of three metal chelators; deferoxamine mesylate (DFO), 1,10-phenanthroline (o-phen) and 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (BAPTA-AM). F. serratus and F. vesiculosus significantly protected (P<0.05) against H(2)O(2) (50 µM) induced DNA damage but not tert-BOOH induced damage.

Build-up dynamics of heavy metals deposited on impermeable urban surfaces.

A method using thin boards (3 cm thick, 0.56 m(2)) comprising different paving materials typically used in urban environments (2 asphalt types and concrete) was employed to specifically investigate air-borne deposition dynamics of TSS, zinc, copper and lead. Boards were exposed at an urban car park near vehicular traffic to determine the rate of contaminant build-up over a 13-day dry period. Concentration profiles from simulated rainfall wash-off were used to determine contaminant yields at different antecedent dry days. Maximum contaminant yields after 13 days of exposure were 2.7 kg ha(-1) for TSS, 35 g ha(-1) zinc, 2.3 g ha(-1) copper and 0.4 g ha(-1) lead. Accumulation of all contaminants increased over the first week and levelled off thereafter, supporting theoretical assumptions that contaminant accumulation on impervious surfaces asymptotically approaches a maximum. Comparison of different surface types showed approximately four times higher zinc concentrations in runoff from asphalt surfaces and two times higher TSS concentrations in runoff from concrete, which is attributed to different physical and chemical compositions of the pavement types. Contaminant build-up and wash-off behaviours were modelled using exponential and saturation functions commonly applied in the US EPA's Stormwater Management Model (SWMM) showing good correlation between measured and modelled concentrations. Maximum build-up, half-saturation time, build-up rate constants and wash-off coefficients, necessary for stormwater contaminant modelling, were determined for the four contaminants studied. These parameters are required to model contaminant concentrations in urban runoff assisting in stormwater management decisions.

Contaminant removal and hydraulic conductivity of laboratory rain garden systems for stormwater treatment.

In order to evaluate the influence of substrate composition on stormwater treatment and hydraulic effectiveness, mesocosm-scale (180 L, 0.17 m(2)) laboratory rain gardens were established. Saturated (constant head) hydraulic conductivity was determined before and after contaminant (Cu, Zn, Pb and nutrients) removal experiments on three rain garden systems with various proportions of organic topsoil. The system with only topsoil had the lowest saturated hydraulic conductivity (160-164 mm/h) and poorest metal removal efficiency (Cu ≤ 69.0% and Zn ≤ 71.4%). Systems with sand and a sand-topsoil mix demonstrated good metal removal (Cu up to 83.3%, Zn up to 94.5%, Pb up to 97.3%) with adequate hydraulic conductivity (sand: 800-805 mm/h, sand-topsoil: 290-302 mm/h). Total metal amounts in the effluent were <50% of influent amounts for all experiments, with the exception of Cu removal in the topsoil-only system, which was negligible due to high dissolved fraction. Metal removal was greater when effluent pH was elevated (up to 7.38) provided by the calcareous sand in two of the systems, whereas the topsoil-only system lacked an alkaline source. Organic topsoil, a typical component in rain garden systems, influenced pH, resulting in poorer treatment due to higher dissolved metal fractions.