Richard J. C. Brown

A review of airborne polycyclic aromatic hydrocarbons (PAHs) and their human health effects

Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds comprised of two or more fused benzene rings arranged in various configurations. PAHs are widespread environmental contaminants formed as a result of incomplete combustion of organic materials such as fossil fuels. The occurrence of PAHs in ambient air is an increasing concern because of their carcinogenicity and mutagenicity. Although emissions and allowable concentrations of PAHs in air are now regulated, the health risk posed by PAH exposure suggests a continuing need for their control through air quality management. In light of the environmental significance of PAH exposure, this review offers an overview of PAH properties, fates, transformations, human exposure, and health effects (acute and chronic) associated with their emission to the atmosphere. Biomarkers of PAH exposure and their significance are also discussed.

New limits in ultrasensitive trace detection by surface enhanced Raman scattering (SERS)

We show the possibility of chemical tracing in solution down to a concentration of a fraction of an atto mol (10 � 18 ) by means of non-resonant surface enhanced Raman scattering (SERS). The experiments are demonstrated with rhodamine 6G dissolved in water. Based on our results here, we propose a technique for counting a small number of SERS active molecules in micro-droplets of liquid. It is argued that, by choosing the appropriate SERS enhancement condition, the technique could be used and implemented as a routine analytical method with unprecedented detection capabilities for the monitoring and tracing of important families of biomolecules. 2003 Elsevier Science B.V. All rights reserved.

Electromagnetic contribution to surface enhanced Raman scattering revisited

Several aspects of the electromagnetic contribution to surface enhanced Raman scattering (SERS) are revisited and analyzed in terms of known concepts and ideas in the field of photonic crystals. A qualitative understanding of some reported SERS phenomena can be achieved by this analysis of the complex energy distribution and spatial localization of surface plasmon resonances in SERS active media. A few of the outstanding issues in the electromagnetic contribution to SERS (like the overwhelming success of nonresonant excitation) can be explained within this framework and, in addition, new physical phenomena utilizing the stimulation or inhibition of the Stokes/anti-Stokes fields are proposed.

The physical and chemical properties of electroless nickel–phosphorus alloys and low reflectance nickel–phosphorus black surfaces

Novel insights into the manufacture of nickel–phosphorus black surfaces by chemical etching of electroless-deposited Ni–P alloy has been achieved by examining the influence of pre-etch phosphorus composition and etching method on the resulting morphology, composition and reflectance of the black surface produced. An optimum phosphorus composition and etching regime to produce low reflectance blacks of 0.4% or lower in the visible region is proposed. Cross-sectional analysis of the etched surface has allowed, for the first time, an accurate determination of the scale of the enhanced morphologies produced and the thickness of the oxidised black layer itself. AFM studies have also provided information on the phase structure of the as-deposited Ni–P alloy.

Reduced free-radical-trapping capacity and altered plasma antioxidant status in cystic fibrosis.

ABSTRACT: Plasma antioxidant status and total radical-trapping antioxidant potential (TRAP) of children (n = 24) with cystic fibrosis (CF) were compared with those of children (n = 21) without the disease. Children with CF were found to have elevated plasma concentrations of ascorbic acid (94.6 ± 58.2 μmol/L), with respect to normal children (65.6 ± 18.8 μmol/L). Plasma uric acid (330.8 ± 84 versus 198.0 ± 31 μmol/L p < 0.01) and sulfhydryl group (518 ± 43 versus 363 ± 31 μmol/L p < 0.01) concentrations were also elevated in CF. Vitamin E levels (16.9 ± 1.8 versus 18.4 ± 1.3 μmol/L) were at the low end of the normal range. Despite an overall increased antioxidant array, CF patients had a reduced TRAP capacity (488 ± 34 versus 580 ± 79 μmol/L, p < 0.05). TRAP measurements in CF patients showed a strong negative correlation (r = 0.80, p < 0.001) with high ascorbic acid concentration, suggesting a prooxidant effect of ascorbic acid. Oral administration of ascorbic acid to adults was found to diminish TRAP activity. Concentrations of ascorbic acid similar to those seen in CF patients were attained in ascorbate-supplemented individuals, with substantial decreases in TRAP capacity. These studies suggest that high plasma ascorbic acid levels in children with CF may have a prooxidant effect. This appears to reduce the extracellular antioxidant defense of these children and may increase susceptibility to oxidative stress.

Observation of dynamic oxygen release in hemoglobin using surface enhanced Raman scattering

Photoinduced oxygen dynamics in hemoglobin is monitored by surface enhanced resonant Raman spectroscopy (SERRS) using silver colloids. The spectra are characterized by massive transient amplifications which we assign to a charge-transfer mechanism during the opening of the heme-pockets in the release of oxygen. This transient lifts the selection rule specificity of normal Raman active modes and allows for the full density of states of the hemes to be observed. The amplification of specific forbidden modes is controlled by the orientation alignment of individual molecules in proximity with the colloid surface. We propose that the technique can be used to monitor oxygen release in single proteins.

The modern paradox of unregulated cooking activities and indoor air quality

Pollutant emission from domestic and commercial cooking activities is a previously neglected area of concern with respect to human health worldwide. Its health effects are relevant to people across the globe, not only those using low quality food materials in lesser-developed countries but also to more affluent people enjoying higher quality food in developed countries. Based on the available database of pollutant emissions derived from fire-based cooking, its environmental significance is explored in a number of ways, especially with respect to the exposure to hazardous vapors and particulate pollutants. Discussion is extended to describe the risk in relation to cooking methods, cooking materials, fuels, etc. The observed pollutant levels are also evaluated against the current regulations and guidelines established in national and international legislation. The limitations and future prospects for the control of cooking hazards are discussed.

Electromagnetic modelling of Raman enhancement from nanoscale substrates: a route to estimation of the magnitude of the chemical enhancement mechanism in SERS

Despite widespread use for more than two decades, the SERS phenomenon has defied accurate physical and chemical explanation. The relative contributions from electronic and chemical mechanisms are difficult to quantify and are often not reproduced under nominally similar experimental conditions. This work has used electromagnetic modelling to predict the Raman enhancement expected from three configurations: metal nanoparticles, structured metal surfaces, and sharp metal tips interacting with metal surfaces. In each case, parameters such as artefact size, artefact separation and incident radiation wavelength have been varied and the resulting electromagnetic field modelled. This has yielded an electromagnetic description of these configurations with predictions of the maximum expected Raman enhancement, and hence a prediction of the optimum substrate configuration for the SERS process. When combined with experimental observations of the dependence of Raman enhancement with changing ionic strength, the modelling results have allowed a novel estimate of the size of the chemical enhancement mechanism to be produced.

Current Status of Trace Metal Pollution in Soils Affected by Industrial Activities

There is a growing public concern over the potential accumulation of heavy metals in soil, owing to rapid industrial development. In an effort to describe the status of the pollutions of soil by industrial activities, relevant data sets reported by many studies were surveyed and reviewed. The results of our analysis indicate that soils were polluted most significantly by metals such as lead, zinc, copper, and cadmium. If the dominant species are evaluated by the highest mean concentration observed for different industry types, the results were grouped into Pb, Zn, Ni, Cu, Fe, and As in smelting and metal production industries, Mn and Cd in the textile industry, and Cr in the leather industry. In most cases, metal levels in the studied areas were found to exceed the common regulation guideline levels enforced by many countries. The geoaccumulation index (I geo), calculated to estimate the enrichment of metal concentrations in soil, showed that the level of metal pollution in most surveyed areas is significant, especially for Pb and Cd. It is thus important to keep systematic and continuous monitoring of heavy metals and their derivatives to manage and suppress such pollution.

SERS Effects in Silver‐Decorated Cylindrical Nanopores

Optimization of pore diameter, the placement of nanoparticles, and the transmission of surface-enhanced Raman scattering (SERS) substrates are found to be very critical for achieving high SERS activity in porous alumina-membrane-based substrates. SERS substrates with a pore diameter of 355 nm incorporating silver nanoparticles show very high SERS activity with enhancement factors of 10(10) .