Biomedical subjects

Susanne Hering

Publications and source records attributed to Susanne Hering.

3 recordsLinked to original sources

PubMed2006

An inexpensive dual-chamber particle monitor: laboratory characterization.

In developing countries, high levels of particle pollution from the use of coal and biomass fuels for household cooking and heating are a major cause of ill health and premature mortality. The cost and complexity of existing monitoring equipment, combined with the need to sample many locations, make routine quantification of household particle pollution levels difficult. Recent advances in technology, however, have enabled the development of a small, portable, data-logging particle monitor modified from commercial smoke alarm technology that can meet the needs of surveys in the developing world at reasonable cost. Laboratory comparisons of a prototype particle monitor developed at the University of California at Berkeley (UCB) with gravimetric filters, a tapered element oscillating microbalance, and a TSI DustTrak to quantify the UCB particle monitor response as a function of both concentration and particle size and to examine sensor response in relation to changes in temperature, relative humidity, and elevation are presented here. UCB particle monitors showed good linearity in response to different concentrations of laboratory-generated oleic acid aerosols with a coarse (mass median diameter, 2.1 microm) and fine (mass median diameter, 0.27-0.42 microm) size distributions (average r2 = 0.997 +/- 0.005). The photoelectric and ionization chamber showed a wide range of responses based on particle size and, thus, require calibration with the aerosol of interest. The ionization chamber was five times more sensitive to fine rather than coarse particles, whereas the photoelectric chamber was five times more sensitive to coarse than fine. The ratio of the response between the two sensors has the potential for mass calibration of individual data points based on estimated parameters of the size distribution. The results demonstrate the significant potential of this monitor, which will facilitate the evaluation of interventions (improved fuels, stoves, and ventilation) on indoor air pollution levels and research on the impacts of indoor particle levels on health in developing countries.

Aerosols↗

PubMed2004

Evaluation of a personal and microenvironmental aerosol speciation sampler (PMASS).

In this study, an all-aluminum sampler was reconfigured to a lighter weight by using plastic for structural components not contacted by aerosol. Because the sampler body was made of plastic, the aluminum size-selective cyclone inlet was redesigned into a separate, removable unit. The resulting personal and microenvironmental aerosol speciation sampler (PMASS*) is a small, compact sampler designed for assaying concentrations of each major chemical constituent of particulate matter less than or equal to 2.5 pm in aerodynamic diameter (PM2.5) as well as its mass. The sampler consists of a miniature cyclone inlet and two parallel sampling channels, each of which may accommodate a denuder, particle filter, and backup filter. One channel serves to measure mass and inorganic ions; the other, organic and elemental carbon. Six of these samplers were first evaluated in the laboratory to verify the 50% cutpoint of the redesigned cyclone inlet near the target flow rate of 4.0 L/min and to test the effect of sampler orientation, aerosol type, and flow rate on the 50% cutpoint. The six samplers were fabricated at two different times with slight modifications in construction that yielded slightly different 50% cutpoints. The units were then evaluated as microenvironmental samplers under field conditions against reference samplers in Fresno, California, and Baltimore, Maryland. Testing in Maryland also included deployment as a personal sampler. In the laboratory, the mean (+/- SD) 50% cutpoint at a 4.1 L/min flow rate was 2.52 +/- 0.08 pm. Sampler orientation did not affect performance of the cyclone. Small differences in penetration efficiency were found with different challenge aerosols. For flow rates between 3.1 and 4.9 L/min, the 50% cutpoint varied from 3.3 pm to 2.1 pm, respectively. As a microenvironmental sampler, the PMASS performed well against relevant reference samplers for elemental carbon, organic carbon, and nitrate measurements but not for mass measurements, for which the PMASS showed a significant bias of -34%. Precision estimates for PMASS elemental carbon, organic carbon, nitrate, and mass, respectively, were 6.8%, 9.0%, 11.9%, and 12.7% in Fresno and 6.6%, 8.7%, 13.6%, and 17.5% in Baltimore. For personal sampling, PMASS measurements of mass again showed a significant bias of -24% compared with the reference sampler. Precision estimates for the PMASS as a personal sampler for elemental carbon, organic carbon, nitrate, and mass were 8.1%, 19.3%, 19.1% and 24.2%, respectively. Sulfate data were not analyzable because of the large magnitude and variability of the sulfate blanks. Field testing revealed some deformation of components of the PMASS filter pack. These problems may have affected the integrity of the particle filter.

Aerosols↗

PubMed2003

A personal particle speciation sampler.

Fuller understanding of personal exposures to particulate matter with aerodynamic diameters below 2.5 microm (PM2.5*) requires a personal sampler suitable for assaying not only PM2.5 mass but also its major chemical constituents: elemental carbon, organic carbon, sulfates, and nitrates. The goal to measure these constituents simultaneously imposes several constraints on personal sampler design. The aim of this project was to develop a sampler within these constraints that would be suitable for personal monitoring over 8 hours. In addition, with the intent to improve the precision of mass measurements, we investigated offline use of beta attenuation. The personal particle speciation sampler (PPSS) includes an inlet to remove particles larger than 2.5 microm, 2 sampling channels, and a pump with flow control. One channel serves for measuring particle mass and inorganic ions; the other, for measuring organic carbon and elemental carbon. Denuders can be placed in either channel or both channels. A backup filter can be placed on the denuded channel to collect volatilized particulate nitrate. Two prototype PPSS units were built and tested. The results of both laboratory testing of key PPSS components and a limited field study of the prototype in comparison to an AIHL (Air and Industrial Hygiene Laboratory) cyclone-based sampler are reported.

Aerosols↗