1,720,987 research outputs found
Development of improved methods for the characterisation of organic chemicals emitted into indoor air by building and furnishing products
Get PDFA wide range of organic compounds are released from building and furnishing products
and these have the potential to adversely affect indoor air quality. There are growing
international requirements for testing and controlling these emissions for the protection
of public health. The test methods require specialist analytical chemistry facilities based
on thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS). This
project has addressed the need for better performance and greater automation of the
analysis, as well as development of simpler screening tests.
A variety of products were tested using screening techniques, with an emission cell
method being used as a reference test. Short duration tests, using a micro-scale chamber
at slightly elevated temperature, were shown to have the potential to predict emissions
occurring during longer term reference tests.
Multi-sorbent air sampling tubes, that have the potential to extend the volatility range of
compounds determined by a single TD/GC/MS analysis, were compared with Tenax TA
tubes specified by current standard methods. This showed no difference in performance
for the range of compounds for which Tenax is optimal, with improved performance for
a number of more volatile compounds.
The determination of formaldehyde was investigated using 2-hydroxymethylpiperidine
as a derivatising agent, followed by TD/GC/MS. The results showed the possibility of
this method being developed as an alternative to the current standard method that
involves solvent elution and liquid chromatography.
The performance of a newly developed time-of-flight mass spectrometer was compared
with a standard quadrupole instrument. This showed its potential, with the use of
re-collection, to extend the concentration range of compounds quantified from a single
air sample, of particular benefit for the determination of carcinogens.
New compound identification software was applied to increase automation of analysis
of the TD/GC/MS data. Good correlation with manual processing was achieved,
demonstrating the possibility of routine application to material emissions testing
Indoor and outdoor dust in Damaturu Nigeria : composition, exposure and risk to human health
Get PDFHarmattan and Dust (sand) storms together with anthropogenic activities including the use of firewood and kerosene as fuel for cooking, and diesel/petrol generators for electricity generation are potential sources of particulate and gaseous pollutants in homes in Damaturu town, Nigeria. Other activities like the burning of locally produced incense and mosquito coils as well as the use of aerosol sprays are further possible sources of indoor pollution, which may result in exposure of people to a range of pollutants through inhalation, by ingestion of settled dusts as well as dermal contact. Local people associate occurrence of dust events with adverse health effects and hence there is a need for an understanding of the composition of the settled and airborne dusts in order to assess the possible associated health risks.
The first phase of the study involved selection and development of methods of dust sampling and analysis. For validation of the methods employed and to establish a broad understanding of the characteristics of the settled dusts, an initial survey study was conducted involving the application of thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) analysis for organic compound analysis, scanning electron microscopy (SEM), inductively coupled plasma-mass spectrometry (ICP-MS) for analysis of metals, and microbiological analysis. Airborne samples were also collected using sorbent tubes to determine organic compounds in air during activities such as cooking with kerosene, gas, and firewood as well as during electricity generation with fossil fuels. Carbon monoxide (CO) and ultrafine particles (UFPs) monitored simultaneously during some of the household activities.
The study involved a novel method of extracting organic chemical emissions from dust by heating of the dusts directly in a micro chamber (μ-CTETM) and collection of emissions on sampling tubes. The method provided a relatively quick way of collecting chemical emissions from dusts that are readily available for release. The sampled tubes were analysed by TD/GC/MS. The conventional solvent extraction of the dusts was also carried out and the extracts were analysed by liquid injection-GC/MS and results of the two methods compared.
The study determined a number of constituents (metals, SVOCs, phthalates and physical properties) of dusts collected from households in Damaturu during different weather events and from different indoor/outdoor locations; and compared with some UK samples. The samples investigated include dusts deposited; during two notable dusty-weather events (Harmattan and Storm) as well as when there was no notable dust event; during human activities; and dusts from different types of buildings (modern and traditional homes) as well as inside and outside homes. A standard reference material for organic chemicals (SRM 2585) was also analysed.
The physical characterization of the settled house dust samples analysed revealed the various shapes and sizes, and elemental composition of the constituents, which included respirable particles. The microbial analysis also indicated the presence of the spores of a host of fungi and bacterial species; and the possible contributions of household activities to the increased production of pollutants (UFP and CO) ascertained.
The μ-CTE extraction of the house dusts by heating with TD/GC/MS analysis of the emissions as well as the solvent extraction-GC/MS revealed the presence of many organic chemical compounds with different analytical retention times and varying concentrations in the dust samples. Chemicals of interest quantified: benzene, hexanal, nonanal, diethyl phthalate (DEP), diisobutylphthalate (DIBP), dibutylphthalate (DBP), and diethylhexylphthalate (DEHP). A host of other chemicals commonly present in the analysed samples identified using the NIST library associated with the MS system software. These chemicals included naphthalene and C10-C16 aliphatic and aromatic hydrocarbons, which would need confirmation by running the pure compound samples.
There was an observed higher concentration of the chemicals in the solvent extracts than the μ-CTE extracted dust. The higher concentration of the chemicals in the solvent extracts expected due to the aggressive removal of the chemicals by the organic solvent whereas in the case of thermal extraction only the readily available chemicals (loosely bound to the matrix) released by increases in temperature were removed. Generally, the concentrations of the chemicals found were higher in the indoor than in the outdoor dust samples. In the analysis of the dusts collected during weather events; higher chemical concentrations observed in the samples collected during Harmattan period than the other periods. The Harmattan dust period may pose increased exposures to dust and possible health risks. More exposure is expected to occur in the traditional homes compared with the modern homes due to the higher concentrations of the chemicals in both the indoors and the outdoors and this may be especially important to women and children who spend most of their times at home.
Metal analysis involved microwave-assisted digestion of the dust samples followed by ICP-MS analysis. The total quant method of metal analysis for a general profiling indicated the presence of more than 50 elemental contaminants in house dust. The results of the quantitative analysis for six target metals: Cd, Cr, Cu, Ni, Pb, and Zn showed their presence in all indoor and the outdoor dust samples. The mean concentrations showed that the metals were in higher concentrations in the indoor dusts than in the outdoor dusts.
The quantitative analysis carried out indicated higher metal contents in the storm dusts than the dusts during the other periods. Results of the dusts collected from modern and traditional homes indicated the presence of the metals in higher concentrations in the dusts from traditional homes than the dusts from the modern homes.
The estimated mean concentrations of the metals and phthalates inadvertently ingested as a constituent of dust indicated that some of the pollutants could exceed the tolerable daily intake (TDI) due to high exposures to dust expected to be the case in Damaturu. The results of the investigation of the dust composition, combined with information on exposure to dust and pollutants, show that dusts are a risk to the health of people in the Damataru community.
Recommendations are made for more studies to provide a better understanding of dust ingestion and exposure to some phthalates and heavy metals in particular and the possible health risks.
To the best of my knowledge, this is the first ever research study of airborne and settled dusts undertaken in North-Eastern Nigeria
In vitro analysis of nanoparticles released from polyamide nanomaterial composites during drilling process
Get PDFNanomaterials provide a new avenue of progress into technological development.
By manipulating materials on the very basic atomic and molecular levels the
property of a given material can be specifically altered to suit the purpose of
intended applications. However, nanomaterials (nanoparticles and nanolayers)
have a more complex nature in physiochemical properties and surface reactivity
than their larger counterparts. Therefore, the release of these nanomaterials as
dust during crushing or drilling may lead to serious health hazards for humans
and the surrounding environment. This study, supported by the NEPHH
(Nanomaterial-related Environmental Pollution Health Hazards), addresses two
important questions about nanomaterials: - Whether nanomaterials can be released
from physical process of nanoproducts. - Toxicity potential of nanodusts
generated from nanoproducts in comparison with reference products. Both
questions address a massive gap in knowledge for toxicity and more specifically
nanomaterial toxicity
Risks to health of carbon monoxide and other combustion gases in energy efficient homes
Get PDFRevisions of the UK Building Regulations are resulting in changes in the design,
construction, heating and ventilation of new and refurbished homes. There are
concerns that inadequate ventilation of these energy efficient homes could
result in increased levels of indoor pollutants. This study considers the possible
risk to occupant health due to exposure to combustion by-products, such as
carbon monoxide (CO).
Measurements of combustion pollutants during the 2010/11 heating season
were undertaken in 14 homes built/refurbished in accordance with 2006
Building Regulations or to a higher standard of energy efficiency, as well as 5
older homes over a two week period.
No WHO indoor air guidelines for CO were exceeded in any home. It was found
that there was a significant difference between CO and nitrogen dioxide in the
kitchen and the bedroom of the main study homes. Modelling of CO
demonstrated how situations of low ventilation combined with high and also
moderate source emission rates could potentially lead to air quality guidelines
being exceeded. Combustion, heating elements and some aerosols were found
to greatly increase the number of ultrafine particles (UFPs). Currently, no
guidelines for UFPs in air are available and there is limited literature reporting
their measurement.
The air quality measurements do not show that energy efficient homes pose
greater risks to health of occupants from combustion pollutants than other
homes. However, modelling suggests some scenarios could produce exposure
to CO exceeding health based guidelines. The study is considered as a
preliminary investigation, not representative of the wide range of different house
types and occupant behaviours that may influence pollutant levels and
exposure of occupants. It does provide valuable indicative data and identifies a
need for further work as current knowledge about indoor air quality in energy
efficient homes is limited and possible risks to health have not been fully
evaluated
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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