Quantifying commuter exposures to volatile organic compounds

2014 Spring.Includes bibliographical references.Motor-vehicles can be a predominant source of air pollution in cities. Traffic-related air pollution is often unavoidable for people who live in populous areas. Commuters may have high exposures to traffic-related air pollution as they are close to vehicle tailpipes. Volatile organic compounds (VOCs) are one class of air pollutants of concern because exposure to VOCs carries risk for adverse health effects. Specific VOCs of interest for this work include benzene, toluene, ethylbenzene, and xylenes (BTEX), which are often found in gasoline and combustion products. Although methods exist to measure time-integrated personal exposures to BTEX, there are few practical methods to measure a commuter's time-resolved BTEX exposure which could identify peak exposures that could be concealed with a time-integrated measurement. This study evaluated the ability of a photoionization detector (PID) to measure commuters' exposure to BTEX using Tenax TA samples as a reference and quantified the difference in BTEX exposure between cyclists and drivers with windows open and closed. To determine the suitability of two measurement methods (PID and Tenax TA) for use in this study, the precision, linearity, and limits of detection (LODs) for both the PID and Tenax TA measurement methods were determined in the laboratory with standard BTEX calibration gases. Volunteers commuted from their homes to their work places by cycling or driving while wearing a personal exposure backpack containing a collocated PID and Tenax TA sampler. Volunteers completed a survey and indicated if the windows in their vehicle were open or closed. Comparing pairs of exposure data from the Tenax TA and PID sampling methods determined the suitability of the PID to measure the BTEX exposures of commuters. The difference between BTEX exposures of cyclists and drivers with windows open and closed in Fort Collins was determined. Both the PID and Tenax TA measurement methods were precise and linear when evaluated in the laboratory using standard BTEX gases. The LODs for the Tenax TA sampling tubes (determined with a sample volume of 1,000 standard cubic centimeters which is close to the approximate commuter sample volumes collected) were orders of magnitude lower (0.04 to 0.7 parts per billion (ppb) for individual compounds of BTEX) compared to the PIDs' LODs (9.3 to 15 ppb of a BTEX mixture), which makes the Tenax TA sampling method more suitable to measure BTEX concentrations in the sub-parts per billion (ppb) range. PID and Tenax TA data for commuter exposures were inversely related. The concentrations of VOCs measured by the PID were substantially higher than BTEX concentrations measured by collocated Tenax TA samplers. The inverse trend and the large difference in magnitude between PID responses and Tenax TA BTEX measurements indicates the two methods may have been measuring different air pollutants that are negatively correlated. Drivers in Fort Collins, Colorado with closed windows experienced greater time-weighted average BTEX exposures than cyclists (p: 0.04). Commuter BTEX exposures measured in Fort Collins were lower than commuter exposures measured in prior studies that occurred in larger cities (Boston and Copenhagen). Although route and intake may affect a commuter's BTEX dose, these variables are outside of the scope of this study. Within the limitations of this study (including: small sample size, small representative area of Fort Collins, and respiration rates not taken into account), it appears health risks associated with traffic-induced BTEX exposures may be reduced by commuting via cycling instead of driving with windows closed and living in a less populous area that has less vehicle traffic. Although the PID did not reliably measure low-level commuter BTEX exposures, the Tenax TA sampling method did. The PID measured BTEX concentrations reliably in a controlled environment, at high concentrations (300-800 ppb), and in the absence of other air pollutants. In environments where there could be multiple chemicals present that may produce a PID signal (such as nitrogen dioxide), Tenax TA samplers may be a better choice for measuring BTEX. Tenax TA measurements were the only suitable method within this study to measure commuter's BTEX exposure in Fort Collins, Colorado

Measuring linearity of connected configurations of a finite number of 2D and 3D curves

We define a new linearity measure for a wide class of objects consisting of a set of of curves, in both 2D and 3D . After initially observing closed curves, which can be represented in a parametric form, we extended the method to connected compound curves—i.e. to connected configurations of a number of curves representable in a parametric form. In all cases, the measured linearities range over the interval (0,1], and do not change under translation, rotation and scaling transformations of the considered curve. We prove that the linearity is equal to 1 if and only if the measured curve consists of two straight line overlapping segments. The new linearity measure is theoretically well founded and all related statements are supported with rigorous mathematical proofs. The behavior and applicability of the new linearity measure are explained and illustrated by a number of experiments

Evaluating energy and indoor air quality potential impact of spray foam: a case study of robotic application

Homes in the UK require transformational retrofit to meet Net Zero legislation. Selecting the right insulation balances multiple, often clashing, performance criteria: energy savings, capital cost, thermal comfort, installation disruption, heritage impact and indoor air quality. There is a lack of evidence in balancing trade-offs between energy, heritage and indoor air quality impact when comparing insulation products. This thesis converged data from different disciplines and showed the retrofit potential, key barriers and enablers of insulating millions uninsulated floors in the UK. In underfloor voids with limited space polyurethane spray foam applied with robots offers better insulating potential compared to conventional products with the same thickness, however more scientific evidence was needed on off-gassing emissions. To measure spray foam emissions, heritage science techniques were adopted to develop a novel method. The method could be applied in built environment case studies to measure volatile organic compounds (VOC) from polyurethane products. The VOC emissions during spraying were assessed for a majority of spray foam product available on the open market. The original data provided evidence for generating a new hypothesis for why 1,2-dichloropropane (1,2-DCP) was found in spray foams. The data suggests 1,2-DCP may have been part of some of the raw materials contrary to the existing hypothesis from 2003 suggesting it was a result of flame retardants degradation. This is relevant as 1,2-DCP was re-classified as Class 1 carcinogen in 2014. Furthermore, ventilation strategies and their effectiveness as a mitigation measure for reducing VOCs were evaluated. Spray foam VOC concentrations were first measured in controlled conditions. Experimental data revealed that VOC concentrations are significantly lower next to sprayers when robots and robust ventilation are deployed. The findings were validated in a case study where long-term VOC concentrations were measured for a period of up to 2 months after retrofit. The majority of VOC concentrations were not detected indoors post-installation with the exception of flame retardants

Implementation and optimization of a sequential injection analysis ( SIA ) system by UV - Visible spectroscopy

Due to the increasing environmental awareness of society and administration, a great number of regulations became effective over the last years in order to preserve natural resources restricting and limiting industrial waste, especially when spills affect aqueous systems. This fact has contributed to the development of a large amount of research programs to come across new methods and processes to monitor and reduce contaminants present in wastewater. Among the variety of contaminants present in industrial effluents, heavy metals are the most hazardous as this compounds are biomagnified and can reach human organism. One of the methods developed for reducing heavy metal concentration in wastewater is biosorption. Biosorption process monitoring has led to the development of sensor arrays or electronic tongues. These kinds of sensors require exhaustive training through the analysis of huge sets of standards, which is time, effort and reagent consumptive. This project is addressed on the optimization of a Sequential Injection Analysis (SIA) prototype built to prepare automatically random generated known training standards and monitor bioprocess absorption to model sensor’s response. In this phase of optimization a miniature spectrometer is assembled to the SIA tubing to monitor flow response in real time of a colorant solution. Spectroscopic analysis also allows monitoring traces of reagent remaining on the system. Calibration and cleaning routines will be designed to ensure reproducibility. Moreover, automatic preparation of standards will be discussed

Investigation of dynamic stresses in detona- tion technical note no. 7

Axial and hoop stress calculation in blast loaded thin walled cylindrical pressure vessel

Method development for measuring volatile organic compound (VOC) emission rates from spray foam insulation (SPF) and their interrelationship with indoor air quality (IAQ), human health and ventilation strategies

The polyurethane foam industry is projected to reach a worldwide value of up to $74bn by 2022 and with airtightness of new and retrofitted properties continually increasing, an important question arises: what is the impact of these materials on the indoor air quality (IAQ), occupants’ health and indoor environment? As the foams are made in-situ through an exothermic reaction between two chemical mixtures (side A and side B), volatile organic compounds (VOCs) are emitted during their application and curing process. Current research, commercial practices and governmental advice suggests that emissions decrease over time and 8-24 h after application are usually sufficient for residents to return safely to their properties. However, there is still a lack of case studies and a fundamental absence of robust analysis on how ventilation strategies affect long term off-gassing rates and chemical emission quantities. The emission rates from SPF materials could have a direct impact on IAQ if they exceed the occupational exposure rates recommended by NIOSH, or other professional associations. But the difficulty in recording these emission rates is evident as there is still a lack of an international standard for their quantification. To address this issue, we have developed an analytical methodology for measuring some of the composition materials of the foams and residual products associated with their application. The experiment consisted of two stages- active air sampling of spray foam emissions and spiking desorption tubes with a standard solution in order to develop calibration curves. The solution included SPF compounds, or by-products from their application, associated with possible acute impact on health: 1,4 dioxane, chlorobenzene, dibutyltin dilaurate, triethyl phosphate and bis(2-dimethylaminoethyl)ether. We managed to detect five of the chemicals of interest through air sampling and produce calibration curves for 1,4 dioxane, chlorobenzene and triethyl phosphate, which would allow us to quantify the emission rates at the next stage of research. The results of the experiments successfully demonstrated proof of concept quantitative methodology for the compounds of interest. With further research and experiments, this technique has the capacity to be developed into an international standard for measuring VOCs from spray foam emissions and other buildings products. This would provide scientists and industry professionals with the tools to further develop retrofit and ventilation strategies in order to provide healthier buildings

LFI 30 and 44 GHz receivers Back-End Modules

The 30 and 44 GHz Back End Modules (BEM) for the Planck Low Frequency Instrument are broadband receivers (20% relative bandwidth) working at room temperature. The signals coming from the Front End Module are amplified, band pass filtered and finally converted to DC by a detector diode. Each receiver has two identical branches following the differential scheme of the Planck radiometers. The BEM design is based on MMIC Low Noise Amplifiers using GaAs P-HEMT devices, microstrip filters and Schottky diode detectors. Their manufacturing development has included elegant breadboard prototypes and finally qualification and flight model units. Electrical, mechanical and environmental tests were carried out for the characterization and verification of the manufactured BEMs. A description of the 30 and 44 GHz Back End Modules of Planck-LFI radiometers is given, with details of the tests done to determine their electrical and environmental performances. The electrical performances of the 30 and 44 GHz Back End Modules: frequency response, effective bandwidth, equivalent noise temperature, 1/f noise and linearity are presented

Precise atmospheric oxygen measurements with a paramagnetic oxygen analyzer

A methodology has been developed for making continuous, high-precision measurements of atmospheric oxygen concentrations by modifying a commercially available paramagnetic oxygen analyzer. Incorporating several design improvements, an effective precision of 0.2 ppm O-2 from repeated measurements over a 1-hour interval was achieved. This is sufficient to detect background changes in atmospheric O-2 to a level that constrains various aspects of the global carbon cycle. The analyzer was used to measure atmospheric O-2 in a semicontinuous fashion from air sampled from the end of Scripps Pier, La Jolla, California, and data from a 1-week period in August 1996 are shown. The data exhibit strongly anticorrelated changes in O-2 and CO2 caused by local or regional combustion of fossil fuels. During periods of steady background CO2 concentrations, however, we see additional variability in O-2 concentrations, clearly not due to local combustion and presumably due to oceanic sources or sinks of O-2. This variability suggests that in contrast to CO2, higher O-2 sampling rates, such as those provided by continuous measurement programs, may be necessary to define an atmospheric O-2 background and thus aid in validating and interpreting other O-2 data from flask sampling programs. Our results have also demonstrated that this paramagnetic analyzer and gas handling design is well suited for making continuous measurements of atmospheric O-2 and is suitable for placement at remote background air monitoring sites