615 N. Wolfe Street
Baltimore, Maryland 21205
Research Page: https://ehe.jhu.edu/research/faculty-research-interests/koehler/index.html
PhD, Colorado State University, 2007
MS, Colorado State University, 2004
BS, University of California, Los Angeles, 2002
As an Associate Professor in the Johns Hopkins Bloomberg School of Public Health my goals are to improve exposure assessment methods to inform occupational and public health policy. My research goals involve the use of direct-reading instrumentation to improve spatiotemporal exposure assessment. Direct-reading (i.e. “real-time”) monitors can rapidly assess exposures to various hazards. My Career Development Award involves coupling estimated exposures with a known location to identify occupational sources of these hazards. Contour plots of the hazard concentration over space, known as concentration maps, have recently been used to assess the spatial variability of hazards. Concentration maps have the potential to be powerful because they are easily comprehensible for workers, managers, and occupational/environmental health scientists to locate areas of concern. In the ambient environment, I am interested in spatiotemporal exposure assessment by pairing direct-reading instruments with a GPS unit to apportion exposures to different microenvironments. I am an investigator on a study in which we are using a Geographic Information System (GIS) to determine whether commuters can reduce their exposure to traffic-related air pollution by changing their route or mode of transportation (driving vs. bicycling). Additionally, I am the P.I. of an award to investigate the indoor exposures for this cohort. While I believe there is great potential for direct-reading instruments to aid in the identification of exposure hazards, it can be dangerous to apply such a methodology without understanding the uncertainties associated with this new form of exposure assessment. My continuing research interests include investigating the use of traditional spatial statistical methods like Kriging and more novel methods employing Bayesian statistics.
I am also interested in developing novel aerosol samplers to improve the relationship between exposures and health effects. I have investigated two novel, low-cost aerosol samplers in the laboratory. The first used polyurethane foams to mimic the size-specific deposition of aerosol in the human respiratory tract. We expect that estimating aerosol deposition will provide a more biologically-relevant estimate of dose and risk than traditional samplers that estimate aerosol intake. This sampler represents a large decrease in cost of the exposure assessment because the foam substrate is inexpensive and the low pressure-drop through it eliminates the need for costly personal sampling pumps. Future research will deploy these personal samplers in the field and investigate the link between exposure, particle deposition, and dose for airborne heavy metals. Second, I measured the aspiration efficiency of a several typical personal aerosol samplers (i.e., 37 mm cassettes, IOM, button) and a prototype high-flow inhalable sampler in a wind tunnel. This prototype sampler converted a disposable, 37-mm cassette into an inhalable sampler. This inexpensive adaption of the 37-mm cassette can provide a substantial cost savings over commercially available inhalable samplers, such as the IOM, and improve limits of detection for well-controlled, but highly toxic air contaminants.
Recipient of the Dept. of Atmospheric Science Alumni Award for Best Paper, CSU (May, 2007).
Recipient of Shrake-Cullor Scholarship, CSU (2005-2006).
Recipient of 3-F Scholarship CSU (2002-2003).