Mid-IR Technologies Help EPA Monitor Environmental Stressors

March 19, 2012

What role can mid-infrared (mid-IR) spectroscopy play in protecting the environment and human health? That is precisely the question being addressed by Mid-Infrared Technologies for Health and the Environment (MIRTHE), a National Science Foundation-Engineering Research Center founded in 2006 at Princeton University (Princeton, NJ) and five partner institutions.

What role can mid-infrared (mid-IR) spectroscopy play in protecting the environment and human health? That is precisely the question being addressed by Mid-Infrared Technologies for Health and the Environment (MIRTHE), a National Science Foundation-Engineering Research Center founded in 2006 at Princeton University (Princeton, NJ) and five partner institutions. The center’s goal is to develop mid-IR optical-trace gas sensing systems that can detect minute amounts of chemicals in the environment or atmosphere, including both naturally occurring chemicals and industry contaminants.

To learn more about this work, Spectroscopy recently spoke to Jon Sobus, PhD, of the United States Environmental Protection Agency (EPA) about how mid-IR technologies are being used in the EPA’s Office of Research and Development (ORD). Sobus spoke on this topic last fall at a conference organized by MIRTHE.

Spectroscopy: What types of analyses does your office do?

Sobus: EPA’s ORD has a diverse research portfolio focused on evaluating, monitoring, and sustaining ecosystems and human health. Research often involves the analysis of environmental media (such as soil, dust, air, surface water, ground water, and drinking water), personal media (such as food and consumer products), and biological media (such as blood, urine, breath, and cells) from living intact organisms or surrogate systems. Target analytes in these media generally include naturally occurring (such as radiation) or anthropogenic stressors (such as air toxics and pesticides), or stress response markers (such as inflammation).

Spectroscopy: How do you make connections between exposure to stressors and the effect on environmental or human health?

Sobus: EPA’s mission is to protect human health and the environment. In carrying out our mission, EPA scientists assess and manage risks posed by environmental stressors. Generally, a stressor is first identified as “hazardous” to environmental or human health, or both. Next, a dose-response assessment determines the level at which a stressor becomes hazardous. Exposure assessment then informs us about the sources, routes, and magnitude of exposure to a population of interest. If exposures are deemed unacceptable, mitigation may be performed to reduce health risks. The primary steps of this process (hazard identification, dose-response assessment, and exposure assessment) often require measurement tools. For example, measurements of environmental media inform us about exposure sources and routes, measurements of biological fluids (biomarkers) inform us about dose levels, and measurements of response to a stressor in living tissue inform us about dose-response. Connections between these measurements help define the “source-to-outcome continuum” for a given stressor. A diagram of the source-to-outcome continuum for human health risk assessment is shown in Figure 1 (1). Mid-IR spectroscopy may prove a useful tool for obtaining these measurements.

Spectroscopy: Why is mid-IR spectroscopy well suited for this work? Is mid-IR more suitable than other approaches?

Sobus: Humans inhabit complex ecosystems that are both highly varied and dynamic. As such, intricate relationships govern human and environmental health. Understanding these relationships requires copious data and appropriate methods for interpretation. Consumer-driven products (for example, smart-phone technologies and global positioning systems) now provide near real-time data on human activities that may affect health (such as diet, physical activity, and proximity to pollution sources). Complements to these data are needed, on a highly resolved spatial and temporal scale, to provide information about health effects from exposure to environmental pollutants. Mid-IR spectroscopy is well suited to help fill this niche because instruments are becoming more portable, affordable, selective for target analytes, and sensitive for trace-level analysis. Analyses using lab-based benchtop instruments, the industry standard in many cases, can be somewhat prohibitive based on the costs (time and money) of sample collection, shipment, preparation, and so forth. Thus, there are clear benefits to methods that rapidly provide accurate and precise measurements to scientists in the field.

Spectroscopy: How is the EPA currently using mid-IR spectroscopy methods in monitoring programs?

Sobus: ORD’s “Air, Climate and Energy” research program is currently developing and evaluating new technologies, including mid-IR spectroscopy, to achieve more effective and efficient air monitoring in support of regulatory development and implementation. For example, mid-IR tools are being evaluated for their ability to characterize airborne emissions from high-priority fugitive and area exposure sources (such as refineries and roadways, respectively). I am unaware of current applications of mid-IR spectroscopy in ORD’s other research programs, which include “Sustainable and Healthy Communities” and “Chemical Safety for Sustainability,” amongst others. However, given the potential benefits of these technologies for analyzing air, biological matrices (for example, breath), and even headspace during in vitro assays, it seems likely that they will be evaluated in support of future monitoring programs.

Spectroscopy: Do current mid-IR tools meet your needs? If not, what new developments are needed?

Sobus: The suitability of a given tool for an application depends on the objectives of the study. As new products are being developed, investigators should work closely with product developers to specify their unique requirements. Some general needs of measurement methods are: sensitivity — investigators are sometimes forced to cope with left-censored data (when a data point is below a certain value but it is unknown by how much) potentially leading to biased results; selectivity — there is often a need to discriminate between analytes with similar chemical features; portability — there are cost advantages to generating data in the field rather than shipping samples for subsequent analysis; and versatility — it is becoming increasingly important to simultaneously analyze multiple stressors as we advance our mixtures research portfolio.


(1)    J.R. Sobus, Y.M. Tan, J.D. Pleil, and L.S. Sheldon, Sci Total Environ.409(22), 4875–4884 (2011).


More Information:

Learn more about the MIRTHE consortium at www.mirthecenter.org

Learn more about programs from the United States EPA’s Office of Research and Development:

Air, Climate and Energy 

Sustainable and Healthy Communities

Chemical Safety for Sustainability

Safe and Sustainable Water Resources

Human Health Risk Assessment

Homeland Security