Personal Exposure Monitoring Device Predicts Breathing Rates, Contributes to More Meaningful Environmental Dose Estimates

RESEARCH TRIANGLE PARK, N.C. — A new technology developed by a research team led by RTI International will help scientists better understand the relationship between environmental contaminants in the air and potential adverse health effects.

The new approach uses personal exposure monitors with built-in acceleration sensors to determine individual activity levels while predicting how fast adults, and potentially children, breathe pollutants in their environment. The advancement enables scientists to calculate potential dosage – how much pollutant enters the respiratory system – in real time.

"While scientists have been measuring exposure levels in the air for decades, knowing the pollutant concentration doesn't necessary indicate how much is taken into the body," said Charles Rodes, Ph.D., an RTI senior fellow and lead author of the study. "By knowing how fast someone is breathing, we can now estimate how much of a pollutant is actually making it into the respiratory system."

The initial results from the pilot program were recently accepted for publication in the journal Atmospheric Environment. The research team included scientists from RTI, Columbia University, Stanford University, Massachusetts Institute of Technology and Northeastern University, and was supported by the National Institute of Environmental Health Sciences (NIEHS) under the Exposure Biology Program (EBP).

"When NIEHS began the program, we had a goal of integrating technologies across aspects of the personal environment, from chemical exposures to physical activity to diet and stress," said David Balshaw, Ph.D., the program coordinator for the EBP. "We hoped that this integrated view would allow the environmental health community to test novel hypotheses and gain further insight into the connections between personal environment and disease. This publication is a demonstration that the vision was accurate; when we integrate measures of physical activity with particulate matter exposure we are able to analyze the health effects of exposure at a new level of sophistication."

In the innovative pilot program, participants wore prototype exposure monitors while conducting a variety of activities (sitting, standing, walking on a treadmill, climbing stairs, sweeping, etc.). By appropriately processing the motion data collected on the built-in accelerometer, the research team was able to reasonably predict breathing rates for a fairly wide range of typical daily activities.

The authors anticipate that the technology could help reduce the cost of linking exposures more closely with diseases that develop over a relatively short time period, such as cardiopulmonary diseases.

"Both the RTI and Columbia groups put accelerometers into their devices to monitor wearing compliance, but we always believed more could be done," said Steve Chillrud, Ph.D., a research professor at Columbia University and study co-author. "This technology is a game changer in exposure health studies. With adult ventilation rates varying by a factor of four across low to moderate activities, any study looking for associations with biomarkers or health outcomes should be better served by potential inhaled dose than with exposure concentrations."

The new approach is completely non-invasive for those wearing the personally sized exposure monitors, providing more accurate data without burdening those being studied.

The research finding could also significantly improve the strength of associations between exposure levels and adverse health responses across a wide range of studies. Supporting this observation, Matthew Longnecker, M.D., a principal investigator at NIEHS, noted that "In a study in South Africa, we will use exposure monitors with this embedded technology over 48-hour periods to assess both exposures and potential doses to characterize impacts from indoor air pollution from cookstoves. That should allow us to evaluate relationships with health outcomes more accurately."

The new technology will be extremely valuable for personal level sensors such as the RTI-developed MicroPEM device, a noninvasive particulate matter sensor that is small enough to fit into a shirt pocket. The upgraded RTI MicroPEM personal exposure monitor is already being used to study how children's exposures are linked to health in a variety of settings.

The accelerometric technology has also been applied to the black carbon personal monitor developed at Columbia University for both exposure and potential dose assessments. Black carbon is emitted into the air by a wide range of combustion sources, including biomass combustion and diesel engine exhaust.

Findings from both monitors are included in the new paper that can be viewed online.