Comparison of diffusion-tube measured nitrogen dioxide concentrations at child and adult breathing heights: who are we monitoring for?

Many towns and cities use passive samplers (diffusion tubes) to monitor nitrogen dioxide (NO2) concentration. However, literature studies have shown large horizontal and vertical concentration gradients for diffusion tubes placed over short distances, raising concerns over the representativeness of monitoring locations. This study examines variations in NO2 concentrations with height at two roadside locations along a busy urban road in Newcastle upon Tyne (UK) over an 8-month period. NO2 concentrations were passively monitored at building facades (approximately 7.0 m from the roadside) at heights of 0.7 m, 1.7 m and 2.7 m to replicate child breathing height in prams and buggies, adult breathing height and the Newcastle City Council sampling height (for 2017), respectively. Paired t tests indicated that NO2 concentrations were significantly lower at 2.7 m (4.7% lower, n = 16, p = 0.001) and 1.7 m (7.1% lower, n = 14, p = 0.007) compared with those at 0.7 m. There was no statistically significant difference between NO2 concentrations measured at 2.7 m and 1.7 m, indicating that UK local authority practice of placing diffusion tubes at higher than adult breathing height does not result in underreporting of NO2 concentrations for regulatory purposes. The results have clear public health implications as they provide evidence that young children, in an urban setting and close to busy roadways, may be exposed to higher NO2 concentrations compared with adults in the same location. We have shown that such differences might not be adequately reflected in the monitoring data from municipal authorities

Longitudinal associations between hearing loss and general cognitive ability:The Lothian Birth Cohort 1936

Hearing impairment is associated with poorer cognitive function in later life. We tested for the potential contribution of childhood cognitive ability to this relationship. Childhood cognitive ability is strongly related to cognitive function in older age, and may be related to auditory function through its association with hearing impairment risk factors. Using data from the Lothian Birth Cohort 1936, we tested whether childhood cognitive ability predicted later-life hearing ability then whether this association was mediated by demographic or health differences. We found that childhood cognitive ability was negatively associated with hearing impairment risk at age 76 (odds ratio = .834, p = .042). However, this association was non-significant following subsequent adjustment for potentially mediating demographic and health factors. Next, we tested whether associations observed in older age between hearing impairment and general cognitive ability level or change were accounted for by childhood cognitive ability. At age 76, in the minimally adjusted model, hearing impairment was associated with poorer general cognitive ability level (β = -.119, p = .030) but was not related to decline in general cognitive ability. The former association became non-significant following additional adjustment for childhood cognitive ability (β = -.068; p = .426) suggesting that childhood cognitive ability contributes (potentially via demographic and health differences) to the association between levels of hearing and cognitive function in older age. Further work is needed to test whether early-life cognitive ability also contributes to the association (documented in previous studies) between older-age hearing impairment and cognitive decline

Peroxide bleach activation: kinetics and mechanisms of some acyl transfer reactions

This research has been concerned with a kinetic and mechanistic study of peroxide bleach activation, which is an important process with regard to detergent formulations. Bleach activation occurs in situ in the laundry liquor and utilises the reaction of alkaline hydrogen peroxide with a peroxyacid precursor (the bleach activator), such as tetraacetylethylenediamine (TAED) or pentaacetylglucose (PAG), to yield an organic peroxyacid - usually peracetic acid. Peroxyacids are more efficient than the traditionally used hydrogen peroxide at stain removal in today's preferred low-temperature washes. The studies contained herein will have hopefully contributed to a greater understanding of the process of bleach activation, facilitating developments in this area. Our approach to this study was to initially work on a bleach activator, p-nitrophenylacetate (PNPA) for which the activation reaction scheme was relatively easy to elucidate. An important feature to arise from the PNPA study was that, in addition to the reaction of hydrogen peroxide with PNPA to yield peracetic acid, peracetic acid itself reacts with PNPA, yielding diacetyl peroxide, which subsequently undergoes hydrolysis and perhydrolysis. It was essential during this study to be able to measure peracetic acid in the presence of excess hydrogen peroxide. This was made possible by the development, by us, of an iodimetric spectrophotometric technique capable of rapidly and accurately measuring peracetic acid concentrations as low as 1x 10-5 M in the presence of up to 1000-fold excess of hydrogen peroxide. The methods and approach developed in the study of PNPA were successfully applied to the study of two commercially used bleach activators, TAED and PAG. Our studies of the reactivity of various nucleophiles towards TAED revealed enhanced reactivity for the hydrogen peroxide anion compared to other peroxide species. A cyclic intermediate mechanism is proposed by us to explain this observation; the hydrogen peroxide anion acts as both nucleophile and general acid catalyst in its reaction with TAED. From work done on PAG we have shown that, despite the often quoted yield of 2.5 moles of peracetic acid per mole of PAG, all 5 acetyl groups are available for transfer to nucleophiles. Also suggested from the PAG studies is the possibility that rate limiting acetyl migration may be important for these reactions

High carbon burial rates by small ponds in the landscape

Temperate ponds may be important sinks and sources of greenhouse gases but just how quickly ponds bury carbon (C) is poorly understood. We derived – to the best of our knowledge – the first organic carbon (OC) burial rates for small ponds of known age by digging out the whole sediment from ponds, and determined that the average C burial rate was 142 g m −2 yr −1 , with a range of 79–247 g m −2 yr −1 , depending on the ponds' vegetation. Burial rates in the ponds were 20–30 times higher than rates estimated for many other habitat types, such as woodlands or grasslands, and higher than those of other natural wetlands. Although small ponds occupy a very small proportion of the landscape as compared to these other habitats, their high OC burial rates result in comparable annual OC burial overall. Ponds are easy to create, can fit in with other land uses, and are a globally ubiquitous habitat. Our results indicate that ponds have the potential to be a very useful additional tool for mitigating C emissions

Associations between hearing and cognitive abilities from childhood to middle age:The National Child Development Study 1958

Previous cross-sectional findings indicate that hearing and cognitive abilities are positively correlated in childhood, adulthood, and older age. We used an unusually valuable longitudinal dataset from a single-year birth cohort study, the National Child Development Study 1958, to test how hearing and cognitive abilities relate to one another across the life course from childhood to middle age. Cognitive ability was assessed with a single test of general cognitive ability at age 11 years and again with multiple tests at age 50. Hearing ability was assessed, using a pure tone audiogram, in childhood at ages 11 and 16 and again at age 44. Associations between childhood and middle-age hearing and cognitive abilities were investigated using structural equation modelling. We found that higher cognitive ability was associated with better hearing (indicated by a lower score on the hearing ability variables); this association was apparent in childhood (r  =  -0.120, p [less than]0.001) and middle age (r  =  -0.208, p [less than]0.001). There was a reciprocal relationship between hearing and cognitive abilities over time: better hearing in childhood was weakly associated with a higher cognitive ability in middle age (β  =  -0.076, p  =  0.001), and a higher cognitive ability in childhood was associated with better hearing in middle age (β  =  -0.163,

Peroxide reactions of environmental relevance in aqueous solution

The main objective of this research programme was to determine the factors influencing the decolourisation of dyes at low pH by different peroxide species, both in the presence and absence of metal ion catalysts and, therefore, to find a set of optimal conditions for application to wastewater treatment processes. An additional study looked at whether peroxoborates were capable of acting as nucleophiles. The specific aims of the study were: to investigate the in-situ formation of peracetic acid from the equilibrium formed between hydrogen peroxide and acetic acid, and whether this can be achieved without the addition of an acid catalyst such as sulphuric acid; to study the comparative reactivity of in-situ generated peracetic acid and hydrogen peroxide towards a range of dyes used in industry; to investigate the catalytic potential of a range of metal ions towards the reaction between peroxides and dyes; to investigate the structural features of dyes that might influence reactivity (decolourisation); and to investigate the reactivities of other peracid-like peroxide species that can be generated from hydrogen peroxide (peroxoborates and peroxocarbonates).The novel aspects arising from this study were: (a) The development of a new method for the in-situ generation of peracetic acid that gives the same equilibrium yield as established methods yet does not require the addition of an acid catalyst;(the reaction was slow, but there was minimal decomposition and so it is ideal for circumstances that allow the preparation of peracetic acid well in advance of use). (b) The first comprehensive study of the bleaching potential of peracetic acid and hydrogen peroxide towards a wide structural range of dyes both in the presence and absence of metal ions (iron, manganese, silver and copper). (c) The inference that for iron-catalysed bleaching of azo dyes by peracetic acid the catalytic mechanism involves pre-complexation of iron and dye, followed by reaction of the 'activated' complex with peracetic acid rather than a free radical mechanism that might have been expected for such systems. (d) The evidence that, in contradiction to literature studies, peroxoborate species do not act as nucleophiles. As an introduction to this work the reactions of peroxyacids are described in general terms. The experimental work is divided in three parts. In Chapter two, the homogeneous preparation of peracetic acid (PAA) from acetic acid (AA) and hydrogen peroxide (H2O2) was investigated with and without the catalysis of sulphuric acid (H2SO4). The formation of PAA and total peroxide content was determined by iodimetric titration. The reaction was slow in the absence of a strong acid catalyst, and was faster with a sulphuric acid catalyst. There was no loss of total peroxide over the timescales of both reactions, whether a catalyst was used or not. The equilibrium constant for peracetic acid formation at temperature of 20 was found to be 2.04 with a catalyst, and 2.10 without catalyst. The rate constant for the hydrolysis of peracetic acid for both forward and reverse reactions increased when the sulphuric acid concentration was increased from 0.02 M to 0.32 M. Linear relationships were found between the observed rate constants and H+ concentrations at 25oC. Moreover, it was found that the preparation of peracetic acid showed a first-order dependence with respect to peroxide concentration. In Chapter three, the application of this preparation of peroxyacids to the degradation of different types of dyesstuffs was investigated. As we know, physical or other chemical methods for dye degradation are expensive and can generate secondary pollution. In this part of the study the reactions of dyes with hydrogen peroxide and peracetic acid in the absence and presence different metal ions (Fe3+, Cu2+, Mn2+ and Ag+) were investigated. The iron/peroxyacid system was found to be the most effective. Consequently, Chapter 4 evaluates the decolourization of five azo dyes under conditions of bleaching by peracetic acid in the presence of Fe3+ as a catalyst. The experiment was carried out in aqueous acidic media. Dye oxidation systems are complex because: they involve several different tautomers; there is the possibility of dye aggregation at lower dye concentrations; and the oxidant species involved can be either the undissociated peroxide acting as an electrophile, or the dissociated peroxide acting as a nucleophile. The results obtained for the reaction of azo dyes with peracetic acid without added iron, when converted to the second order rate constant for the electrophilic reaction, k2E gave a value of 4.5x10-6 dm3 mol-1 s-1 for orange II, which is very high. This may be due to trace metal ions still being present and catalysing the reaction, possibly from impurities in the dye itself. No metal ion chelators were used in the present study because the bulk of the study was designed to elucidate the effect of metal ions concentration on reaction rate. For the catalysed reactions a significantly increased rate of absorbance decrease with increasing iron concentration was observed. Saturation of iron was also demonstrated at high iron concentrations, suggesting the formation of an iron (III)-dye complex which then reacted with peracetic acid. The maximum rate of reaction was observed at an iron concentration of 0.012 M, and the results showed a reactivity order of Ponceau 4R > Amaranth > (Orange II & Carmosine) > Black PN; Orange 1 was unreactive under these conditions. Also one of the key objectives of this chapter was to determine the optimum conditions for dye degradation in terms of pH and oxidant and catalyst concentrations. The optimum conditions for maximum degradation occurred at the highest pH of 3.0 and at about 1x10-3 M iron. Evidence of the possible involvement of radicals in our studies comes from the observation of a lag phase followed by a more rapid bleaching phase in the oxidation of azo dyes by peracetic acid at the lowest iron concentrations (another possibility is that at these iron concentrations the reactive iron complex forms at a much slower rate). However, this process is slow by comparison with the rate of oxidation at higher iron concentrations that do not exhibit this lag phase; consequently, if free radical mechanisms are suggested then they are not significant compared to the proposed formation of a reactive iron-dye complex.ixThe work contained in final experimental Chapter aimed to clarify whether or not any of the peroxyborate species displayed nucleophilic characteristics and thus accelerated the rate of the reaction of hydrogen peroxide with p-nitrophenyl acetate. The pH range of 6.0 to 8.0 is critical in terms of the distribution of peroxide species for a hydrogen peroxide / boric acid system. The triganol peroxoboric acid, B(OH)2OOH, is the only significant peroxoborate species below pH 6.5. However, above this pH, increased concentrations of the monoperoxoborate anion, B(OH)3OOH, the peroxodiborate anion, (HO)3BOOB(OH)32-, and the diperoxodiborate anion (HO)2B(OO)2B(OH)22-, are formed, with diperoxoborate, B(OH)2(OOH)2- forming at higher hydrogen peroxide concentrations. Therefore this is the ideal pH range in which to elucidate any effects of borate on the reaction of hydrogen peroxide and PNPA. The observed second order rate constants (k2obs) for the reaction between p-nitrophenyl acetate and hydrogen peroxide, and the corresponding second order rate constants, k2, for the reaction of the perhydroxyl anion with p-nitrophenyl acetate was determined by equation:In borate buffer the k2 values were significantly reduced compared to other buffers; this reduction was consistent with the hydrogen peroxide complexing with borate to form a range of non-reactive (towards carbonyl groups) peroxoborate species, thus also reducing the equilibrium concentration of the perhydroxyl anion. There was no evidence for peroxoborate species that could act as nucleophiles, in contradiction of literature claims. Values of k2 in the case of phosphate buffer compared reasonably well with values in the literature of 3140 and 3520 dm3 mol-1 s-1 obtained at pH 6.8 in ionic strengths of 0.02 dm3 mol-1 and 0.1dm3 mol-1 respectively. In carbonate buffer the literature value is 3785 dm3 mol-1 s-1 at pH 10, ionic strength 0.1 M, in borate buffer.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A novel approach to the development of 1-hour threshold concentrations for exposure to particulate matter during episodic air pollution events

Episodic air pollution events that occur because of wildfires, dust storms and industrial incidents can expose populations to particulate matter (PM) concentrations in the thousands of µg m-3. Such events have increased in frequency and duration over recent years, with this trend predicted to continue in the short to medium term because of climate warming. The human health cost of episodic PM events can be significant, and inflammatory responses are measurable even after only a few hours of exposure. Consequently, advice for the protection of public health should be available as quickly as possible, yet the shortest averaging period for which PM exposure guideline values (GVs) are available is 24-hours. To address this problem, we have developed a novel approach, based on Receiver Operating Characteristic (ROC) statistical analysis, that derives 1-hour threshold concentrations that have a probabilistic relationship with 24-hour GVs. The ROC analysis was carried out on PM10 and PM2.5 monitoring data from across the US for the period 2014 to 2019. Validation of the model against US Air Quality Index (AQI) 24-hour breakpoint concentrations for PM showed that the maximum-observed 1-hour PM concentration in any rolling 24-hour averaging period is an excellent predictor of exceedances of 24-hour GVs

Cognitive function trajectories and their determinants in older people:8 years of follow-up in the English Longitudinal Study of Ageing

BACKGROUND: Maintaining cognitive function is an important aspect of healthy ageing. In this study, we examined age trajectories of cognitive decline in a large nationally representative sample of older people in England. We explored the factors that influence such decline and whether these differed by gender. METHODS: Latent growth curve modelling was used to explore age-specific changes, and influences on them, in an 8-year period in memory, executive function, processing speed and global cognitive function among 10 626 participants in the English Longitudinal Study of Ageing. We run gender-specific models with the following exposures: age, education, wealth, childhood socioeconomic status, cardiovascular disease, diabetes, physical function, body mass index, physical activity, alcohol, smoking, depression and dementia. RESULTS: After adjustment, women had significantly less decline than men in memory (0.011, SE 0.006), executive function (0.012, SE 0.006) and global cognitive function (0.016, SE 0.004). Increasing age and dementia predicted faster rates of decline in all cognitive function domains. Depression and alcohol consumption predicted decline in some cognitive function domains in men only. Poor physical function, physical inactivity and smoking were associated with faster rates of decline in specific cognitive domains in both men and women. For example, relative to study members who were physically active, the sedentary experienced greater declines in memory (women −0.018, SE 0.009) and global cognitive function (men −0.015, SE 0.007 and women −0.016, SE 0.007). CONCLUSIONS: The potential determinants of cognitive decline identified in this study, in particular modifiable risk factors, should be tested in the context of randomised controlled trials

Peroxide reactions of environmental relevance in aqueous solution

The main objective of this research programme was to determine the factors influencing the decolourisation of dyes at low pH by different peroxide species, both in the presence and absence of metal ion catalysts and, therefore, to find a set of optimal conditions for application to wastewater treatment processes. An additional study looked at whether peroxoborates were capable of acting as nucleophiles. The specific aims of the study were: to investigate the in-situ formation of peracetic acid from the equilibrium formed between hydrogen peroxide and acetic acid, and whether this can be achieved without the addition of an acid catalyst such as sulphuric acid; to study the comparative reactivity of in-situ generated peracetic acid and hydrogen peroxide towards a range of dyes used in industry; to investigate the catalytic potential of a range of metal ions towards the reaction between peroxides and dyes; to investigate the structural features of dyes that might influence reactivity (decolourisation); and to investigate the reactivities of other peracid-like peroxide species that can be generated from hydrogen peroxide (peroxoborates and peroxocarbonates).The novel aspects arising from this study were: (a) The development of a new method for the in-situ generation of peracetic acid that gives the same equilibrium yield as established methods yet does not require the addition of an acid catalyst;(the reaction was slow, but there was minimal decomposition and so it is ideal for circumstances that allow the preparation of peracetic acid well in advance of use). (b) The first comprehensive study of the bleaching potential of peracetic acid and hydrogen peroxide towards a wide structural range of dyes both in the presence and absence of metal ions (iron, manganese, silver and copper). (c) The inference that for iron-catalysed bleaching of azo dyes by peracetic acid the catalytic mechanism involves pre-complexation of iron and dye, followed by reaction of the 'activated' complex with peracetic acid rather than a free radical mechanism that might have been expected for such systems. (d) The evidence that, in contradiction to literature studies, peroxoborate species do not act as nucleophiles. As an introduction to this work the reactions of peroxyacids are described in general terms. The experimental work is divided in three parts. In Chapter two, the homogeneous preparation of peracetic acid (PAA) from acetic acid (AA) and hydrogen peroxide (H2O2) was investigated with and without the catalysis of sulphuric acid (H2SO4). The formation of PAA and total peroxide content was determined by iodimetric titration. The reaction was slow in the absence of a strong acid catalyst, and was faster with a sulphuric acid catalyst. There was no loss of total peroxide over the timescales of both reactions, whether a catalyst was used or not. The equilibrium constant for peracetic acid formation at temperature of 20 was found to be 2.04 with a catalyst, and 2.10 without catalyst. The rate constant for the hydrolysis of peracetic acid for both forward and reverse reactions increased when the sulphuric acid concentration was increased from 0.02 M to 0.32 M. Linear relationships were found between the observed rate constants and H+ concentrations at 25oC. Moreover, it was found that the preparation of peracetic acid showed a first-order dependence with respect to peroxide concentration. In Chapter three, the application of this preparation of peroxyacids to the degradation of different types of dyesstuffs was investigated. As we know, physical or other chemical methods for dye degradation are expensive and can generate secondary pollution. In this part of the study the reactions of dyes with hydrogen peroxide and peracetic acid in the absence and presence different metal ions (Fe3+, Cu2+, Mn2+ and Ag+) were investigated. The iron/peroxyacid system was found to be the most effective. Consequently, Chapter 4 evaluates the decolourization of five azo dyes under conditions of bleaching by peracetic acid in the presence of Fe3+ as a catalyst. The experiment was carried out in aqueous acidic media. Dye oxidation systems are complex because: they involve several different tautomers; there is the possibility of dye aggregation at lower dye concentrations; and the oxidant species involved can be either the undissociated peroxide acting as an electrophile, or the dissociated peroxide acting as a nucleophile. The results obtained for the reaction of azo dyes with peracetic acid without added iron, when converted to the second order rate constant for the electrophilic reaction, k2E gave a value of 4.5x10-6 dm3 mol-1 s-1 for orange II, which is very high. This may be due to trace metal ions still being present and catalysing the reaction, possibly from impurities in the dye itself. No metal ion chelators were used in the present study because the bulk of the study was designed to elucidate the effect of metal ions concentration on reaction rate. For the catalysed reactions a significantly increased rate of absorbance decrease with increasing iron concentration was observed. Saturation of iron was also demonstrated at high iron concentrations, suggesting the formation of an iron (III)-dye complex which then reacted with peracetic acid. The maximum rate of reaction was observed at an iron concentration of 0.012 M, and the results showed a reactivity order of Ponceau 4R > Amaranth > (Orange II & Carmosine) > Black PN; Orange 1 was unreactive under these conditions. Also one of the key objectives of this chapter was to determine the optimum conditions for dye degradation in terms of pH and oxidant and catalyst concentrations. The optimum conditions for maximum degradation occurred at the highest pH of 3.0 and at about 1x10-3 M iron. Evidence of the possible involvement of radicals in our studies comes from the observation of a lag phase followed by a more rapid bleaching phase in the oxidation of azo dyes by peracetic acid at the lowest iron concentrations (another possibility is that at these iron concentrations the reactive iron complex forms at a much slower rate). However, this process is slow by comparison with the rate of oxidation at higher iron concentrations that do not exhibit this lag phase; consequently, if free radical mechanisms are suggested then they are not significant compared to the proposed formation of a reactive iron-dye complex.ixThe work contained in final experimental Chapter aimed to clarify whether or not any of the peroxyborate species displayed nucleophilic characteristics and thus accelerated the rate of the reaction of hydrogen peroxide with p-nitrophenyl acetate. The pH range of 6.0 to 8.0 is critical in terms of the distribution of peroxide species for a hydrogen peroxide / boric acid system. The triganol peroxoboric acid, B(OH)2OOH, is the only significant peroxoborate species below pH 6.5. However, above this pH, increased concentrations of the monoperoxoborate anion, B(OH)3OOH, the peroxodiborate anion, (HO)3BOOB(OH)32-, and the diperoxodiborate anion (HO)2B(OO)2B(OH)22-, are formed, with diperoxoborate, B(OH)2(OOH)2- forming at higher hydrogen peroxide concentrations. Therefore this is the ideal pH range in which to elucidate any effects of borate on the reaction of hydrogen peroxide and PNPA. The observed second order rate constants (k2obs) for the reaction between p-nitrophenyl acetate and hydrogen peroxide, and the corresponding second order rate constants, k2, for the reaction of the perhydroxyl anion with p-nitrophenyl acetate was determined by equation:In borate buffer the k2 values were significantly reduced compared to other buffers; this reduction was consistent with the hydrogen peroxide complexing with borate to form a range of non-reactive (towards carbonyl groups) peroxoborate species, thus also reducing the equilibrium concentration of the perhydroxyl anion. There was no evidence for peroxoborate species that could act as nucleophiles, in contradiction of literature claims. Values of k2 in the case of phosphate buffer compared reasonably well with values in the literature of 3140 and 3520 dm3 mol-1 s-1 obtained at pH 6.8 in ionic strengths of 0.02 dm3 mol-1 and 0.1dm3 mol-1 respectively. In carbonate buffer the literature value is 3785 dm3 mol-1 s-1 at pH 10, ionic strength 0.1 M, in borate buffer.EThOS - Electronic Theses Online ServiceGBUnited Kingdo