Research Note 94-11: Topic = How Much Air Do We Breathe?

 California Environmental Protection Agency

Air Resources Board

 No. 94-11

August 1994

 RESEARCH NOTES

Brief Reports to the Scientific and Technical Community


 Research Division, John R. Holmes, Ph.D., Chief

P.O. Box 2815, Sacramento CA 98512


How Much Air
 Do We Breathe?


In this Note we describe the first large systematic study to measure the amount of air people breathe during their normal activities. The amount of air breathed and related physiological factors were measured on 160 normally active males and females ranging from 6 to 77 years of age. Measurements were taken both during actual work and play conditions and in laboratory settings.

Results indicate that adult males from adolescents through seniors breathe similar amounts of air during similar activities, as do adult females across those age groups. Children inhale more air than do adults, relative to body surface area, breathing frequency, and heart rate. However, the investigator found that widely used estimation methods based on treadmill heart rate measurements tend to overpredict the amount of air breathed during field activities by 10-20 percent. This study provides actual measurements obtained during real activities, and will significantly improve population estimates of the amount of air pollutants inhaled, thereby reducing some of the uncertainty in air pollution risk assessment.

Background:

Estimating and reducing health risk from air pollution requires accurate estimates of the inhaled dose of pollutants. Inhaled dose is based on three factors: the concentration of pollutant in the air, the amount of time the person spends in the polluted environment, and the amount of air the person breathes while in the environment. Previous breathing measurement studies were conducted primarily on men performing athletic and occupational activities. This study emphasized breathing measurements of children, women, and senior citizens during common activities performed around the home. This study also included subjects representative of California´s ethnic diversity.

Methods:

Each subject´s heart rate, breathing frequency, and volume of air breathed were measured both in laboratory settings and at home during usual activities. Equal numbers of subjects were tested in each of four age groups: child, adolescent, young/middle-aged adult, and senior. In the laboratory, subjects were monitored while lying down, sitting, standing, walking, and jogging. Field measurements were gathered during a variety of common activities: playing, driving and riding in a car, working in the yard, performing housework, mowing the lawn, and engaging in woodwork and car maintenance.

Results:

The primary purpose of this study was to provide population-based breathing averages and distributions appropriate for air pollution risk assessment. Figures 1, 2, and 3 indicate the average volume of air breathed during various activities for children, adult females, and adult males, respectively. Relative to body surface area, the volume of air breathed by children is substantially higher than the volume breathed by adults because children have greater metabolic needs, due to growth. Differences in breathing volumes among adults are primarily due to differences in body surface area.

Findings from the field measurements indicate that common household tasks are typically conducted at moderate exercise levels. Children generally self-regulate and play at moderate exercise levels. Breathing volumes at light or moderate exercise levels are best predicted by body surface area and breathing frequency. For more intense exercise, such as sustained walking or running, tha heart rate is the best predictor of the amount of air breeathed for adult females. However, breathing frequency and body surface area are best for the other subpopulations during these activities. This study showed that using laboratory treadmill heart rate findings tends to overpredict by 10 to 20 percent the amount of air breathed during field activities.

The study discerned small but important differences in the volume of air breathed during seemingly similar activities. For example, sitting, riding in a car, and driving a car are all sedentary activities, yet subjects inhaled 5.4 percent more air per minute while riding in a car than while sitting quietly in the laboratory. While driving a car, subjects inhaled 15.4 percent more air per minute than while sitting in the laboratory and 9.6 percent more than while riding in a car.

Significance and Application:

A unique component of this study was the measurement of breathing volume and heart rate of subjects while they performed regular activities at home. This study eliminates the uncertainty of estimating breathing volumes for everyday activities from laboratory measurements. In addition the study provides breathing measurements for children, women, and seniors; previously, measurements for these groups were extremely limited. This information is pivotal for estimating the amount of pollutants inhaled by Californians.

Related Projects:

The Air Resources Board has sponsored studies to determine how much time Californians spend in different locations and activities. The results of this breathing study will be used in combination with results of the activity studies and indoor and outdoor pollutant concentration data to improve our estimates of the amount of air pollutants people inhale during their normal daily lives..

94-11_FIG1
94-11_FIG2
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This research was conducted under contract with the University of California, Davis (ARB Contract No. A033-205). Comments or questions can be directed to Dorothy Shimer, by mail, FAX (916) 322-4357, e-mail, or phone (916) 327-8693.

Copies of the research report upon which this Note is based can be ordered from:

National Technical Information Service
5285 Port Royal Rd
Springfield VA 22161
Request NTIS No. PB94109444

Title: Measurement of Breathing Rate and Volume in Routinely Performed Activites

Authors: William C. Adams