For decades, studies of health risks from air pollution were limited by uncertainty in characterizations of acute and chronic aerosol exposures. Because existing technologies for directly measuring sized aerosols were expensive and complex, researchers used surrogate metrics to estimate personal exposures.
This approach left critical gaps in data, making it difficult to define dose-response relationships for asthma, acute lower respiratory infections, and other diseases. That is, researchers could not make clear connections between the level of exposure to air pollutants a person received and the health effects he or she experienced. This, in turn, made it difficult for researchers to evaluate interventions to reduce risks to human health from exposure.
For asthma alone—a disease known to be triggered by ozone and airborne particles—the number of adults and children diagnosed exceeds 300 million worldwide, and some 250,000 people die annually as a result of the disease.
To combat the asthma and other critical health challenges, researchers need accurate data on personal exposure to air pollution.
MicroPEM Device Advances the Science of Personal Exposure Assessment
In response to the need for better exposure data, in 2006 our experts in particulate matter (PM) measurement launched an effort to develop a personal PM exposure monitor—dubbed MicroPEM. This effort was supported by the National Institute of Environmental Health Sciences as well as our own investment.
The MicroPEM device monitors individual exposures to very fine airborne particles—or particulate matter—at two sizes. PM10 has a diameter of less than 10 micrometers (PM10), which is approximately 1/30th the size of a human hair, and PM2.5, which at diameters of less than 2.5 micrometers, is even smaller.
First used in research studies in 2011, the MicroPEM device represented a significant advancement in personal exposure assessment. The monitor is small and light enough to be worn by an individual during daily tasks—including work, school, and leisure activities. MicroPEM enables real-time and gravimetric measurement of a person’s exposure—essential data for understanding the causes of adverse health outcomes. It also monitors the person’s activity levels via a built-in accelerometer, allowing researchers to correlate exposures with activity.
In 2012, R&D Magazine recognized the significant advancement of our MicroPEM device with its prestigious "R&D 100" award.
Comprehensive Data Collection, User-Friendly Interface, and Wearable Form Factor
Designed for ease of use by researchers and study participants, the MicroPEM device offers several key features and benefits:
- Lightweight (<240g) and only slightly larger than a smartphone
- Operates continuously for up to 48 hours on three AA batteries
- User-friendly setup and simple controls for downloading data
- On-board data collection and quality control
- Integrated filter collection to enable quantitative post-analyses and identification of potential confounding exposures from sources such as tobacco smoke.
An onboard pump maintains a stable flow rate, and interchangeable impactor stages provide PM2.5 or PM10 aerodynamic cut-points to match particle size regimes defined by the U.S. Environmental Protection Agency (EPA). Particles are detected using a light-scattering nephelometer, which records real-time PM concentration data at 10-second intervals. A user-replaceable filter is also available for sample collection, allowing gravimetric analysis and speciation studies of the collected sample.
Accelerometric Data Facilitates Dose Monitoring
Health impacts from air pollutants are not just based on the concentrations in the environment, but on how much of the pollutant is actually inhaled. To accurately measure actual exposure, our MicroPEM device features a sensitive triaxial accelerometer that enables researchers to determine when the monitor was worn in the personal mode. Equally important, the accelerometric data can also reliably estimate ventilation rates for adults in liters per minute.
With this built-in technology, for the first time direct concentration data can be used to estimate potential dose. This, in turn, enables the impact of periods of high exposure concentrations and elevated breathing rates to be linked with target health outcomes.
By enabling researchers to make these linkages, MicroPEM can help advance our understanding of dose-response relationships and support efforts to identify people who suffer the highest exposure rates and quantify their exposures.
A Versatile Tool for Occupational and Interventional Health Studies and Indoor Air Quality Research
The MicroPEM sensor is directly applicable to a wide range of challenges, including occupational exposure assessment, indoor air quality research, and interventional health studies. Children as young as 6 years can wear the MicroPEM device comfortably. For those 5 and under, we have developed the Enhanced Children's MicroPEM.
Because of its small, lightweight, and quiet form factor, the MicroPEM does not interfere with job duties—thus enabling representative measurements of occupational exposure throughout a work shift. Real-time PM exposure concentration and accelerometer data can be transmitted wirelessly to a worker, giving him or her instantaneous situational awareness of exposure risks in the workplace. By aggregating MicroPEM data transmitted to a central computer, researchers can create a complete spatial-temporal map of PM exposures across the workplace.
Using the MicroPEM, health researchers can define both acute and chronic exposure patterns for sized aerosols at both environmental and personal levels. Because it accurately measures both the highest and lowest exposures, the MicroPEM sensor can quantify the entire exposure range. Armed with the advanced capabilities of this sensor, epidemiologists and health professionals can plan and implement studies to set realistic targets for interventions.
RTI has tested the MicroPEM device for use in indoor air quality studies in both controlled and field settings. Using data from these trials, we further refined and enhanced the device’s design for ruggedness and data quality.
Seeking Research Partners
The MicroPEM was developed to help scientists collect accurate exposure data for populations of adults and children whose health is compromised by exposures to air pollutants. We are seeking university and commercial partners to apply the MicroPEM sensor in large-scale health studies that require accurate characterization of a range of exposure settings. In addition, patents and software that drive the MicroPEM sensor are available for nonexclusive licensing in a select group of countries outside the U.S.
