Study looks at between inhalation of small particles, reduced heart rate variability and death

Jun 7 2004

While there is evidence to suggest that breathing air containing particulate matter can cause problems for people with decreased heart rate variability, no one has done a definitive study to examine whether there is a direct link between the two. Roger Jenkins of the lab’s Chemical Sciences Division hopes to address the situation with a two-year study involving 40 participants who will be exposed to three commonly encountered indoor air pollutants.

“Understanding the relationship between heart rate variability and particle exposure could help explain increased mortality associated with inhalation of small particles,” Jenkins said. “We hope this will be a first step toward learning how heart rate variability changes as we move through many environments during the course of a day.”

Heart rate variability refers to the beat-to-beat alterations in heart rate on a micro-second time scale. As people age, this micro-chaos tends to diminish, and there is evidence linking this condition to sudden death for people who have had previous heart attacks.

The study by ORNL and the University of Kentucky will address what Jenkins describes as a major flaw in previous studies that typically measure outdoor particulate concentrations. Most people, however, spend the majority of their time indoors, Jenkins noted.

“The big challenge -- and the only way to get a real handle on the problem -- is to simultaneously measure heart rate variability, respiration and particulate concentrations,” said Jenkins, who has published several papers about real-world exposures to environmental tobacco smoke.

While ORNL has vast experience in sampling and studying exposures to environmental tobacco smoke, researchers at the University of Kentucky’s Center for Biomedical Engineering provide expertise in the cardio-respiratory interface and measurement techniques.

Researchers will expose subjects to cooking oil fumes, environmental tobacco smoke and wood smoke intermittently for three hours on three separate occasions. “The exposures will average out to the levels of indoor air particles that many of us encounter in our daily lives,” said Jenkins, who hopes to accomplish two major goals.

“We should have a far better understanding of the mechanisms that control changes in heart rate variability associated with particulate exposure,” Jenkins said. “And we should know what it will take to develop a portable real-time monitor that can simultaneously measure heart rate variability, respiration and airborne particle concentration.”

With the new Environmental Protection Agency Particulate Matter 2.5 standard, which is stricter than the previous PM10 standard regarding acceptable quantities of pollutants in the air, Jenkins believes this study has special importance.

“National laboratories should deal with complex problems of national significance, and this project certainly falls into that category,” Jenkins said. “As a nation, we need to know the impact on human health of inhaling fine particles, and this research should enable us to make significant progress in that area.”

Jenkins expects recruiting of subjects to begin in July. In each year, about 20 non-smokers between 25 and 45 in age with an equal number of men and women will participate in the study. Each participant will undergo a physical examination to rule out certain risk factors such as diabetes, systemic hypertension, and respiratory and heart abnormalities.

The Oak Ridge Sitewide Institutional Review Board has granted approval to use human subjects and the associated research project protocol. Each exposure cycle will be less than three hours in duration, and actual exposures to the test aerosols likely will be less than one hour. In addition, maximum concentrations of smoke and fumes will be lower than what is allowed by the Occupational Safety and Health Administration for workers for eight hours.

Researchers will collect physiological response data during the experiments, and participants will provide information about other exposures they encounter as part of their daily routines. All information will be kept confidential and all data will be linked through an identifying number and code for each participant.

If the study shows sufficient reason to believe there are cardio-pulmonary responses to exposures to airborne contaminants, Jenkins hopes for a follow-up project to develop instrumentation that can be worn by participants under real-world exposure conditions.

ORNL is managed by UT-Battelle for the Department of Energy. The research is funded by Philip Morris.

http://www.ornl.gov