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Quantification of population exposure to secondhand smoke

Institution: Stanford University
Investigator(s): Paul Switzer, Ph.D.
Award Cycle: 1997 (Cycle 6) Grant #: 6RT-0118 Award: $686,858
Subject Area: Epidemiology
Award Type: Research Project Awards

Initial Award Abstract
To determine the health risks from secondhand smoke, it is important to know the pollutant concentrations to which people are exposed and the durations of their exposures. Despite public concern about secondhand smoke, there are surprisingly few studies in California that actually measure the pollutant levels to which people are exposed as a result of smoking activity. Recent advances in monitoring instruments make it possible to measure secondhand smoke in the actual places where people are exposed. Indeed, some of our past studies have used these advanced monitoring instruments to measure indoor air pollution in California restaurants, taverns, bars, lounges, and automobiles.

Without reasonable estimates of the pollutant levels caused by secondhand smoke, it is difficult to study whether its adverse pollutants, such as particles and carbon monoxide, come from smoking or from activities such as cooking or outdoor sources. Virtually no data are available on indoor air quality levels before and after smoking intervention steps. In a previous 3-year study, we measured fine particle air pollutant concentrations on multiple visits to a California sports tavern both before and after smoking prohibition. Fine particle concentrations, which can penetrate deep into the lungs, dropped 77% after smoking was prohibited in the tavern.

Since more potential ETS exposure occurs in the home than in any other location, the optimal place for measuring and modeling exposure is the home. We propose to study secondhand smoke in the home using direct measurements under controlled experimental conditions. The resulting data will enable us to develop a computer model that allows us to predict and understand pollutant levels due to smoking and other sources and the effect of interior door positions, window openings, house configuration, and smoking activity patterns. Closed doors may cause rooms in homes sometimes to act as compartments collecting pollutants. By characterizing and modeling pollutants in controlled monitoring experments, it will be possible to predict pollutant levels at other similar locations from information on smoking patterns, room volumes, and ventilation rates.

As part of the proposed research, we will adapt existing monitoring instruments to operate automatically, storing readings continuously on portable computers. These new automated systems should allow secondhand smoke levels to be measured more effectively in future studies. We also will test the accuracy of the model predictions using our measurements in real homes. Finally, using data from these studies, together with published studies on the charact-eristics of California homes and the activity patterns of California residents, we will develop a general computerized total exposure model to predict the population distributions of exposures. For example, information on the time spent in homes, motor vehicles, etc., and corresponding pollutant profiles for these locations will allow us to estimate combined exposure. Such a model consolidates existing knowledge on human exposure and provides a powerful tool for assessing health risks, guiding public health decisions, and choosing smoking intervention strategies.

Final Report
Determining the public health risks of environmental tobacco smoke (ETS) and formulating effective public policy in light of these risks require accurate information on the population's exposure to ETS pollutants. However, few studies have measured actual population exposure to ETS. Our research determines how people become exposed to ETS, where they are exposed, how much exposure occurs, how long they are exposed, and what factors affect their exposure. Our first aim was to develop a portable air monitoring system to measure ETS pollutants in indoor environments with sufficient time resolution for exposure modeling. We developed two complementary Continuous Air Monitoring Package (CAMP) systems that can measure several ETS pollutants and take readings every minute. Our second aim was to determine the levels of ETS exposure by direct measurement in a wide variety of nonresidential indoor locations. We conducted a field survey that visited 247 such nonresidential locations including restaurants, sports taverns, pizza parlors, stores, banks, copy centers, and building lobbies. To assess ETS exposure due to smoking activity, we counted the number of burning cigarettes and measured indoor pollutant concentrations at each location. Fine particle concentrations at some locations briefly exceeded EPA's health-based ambient standard for fine particles. We also measured ETS pollutant concentrations in homes relating these concentrations, via our modeling effort, to model inputs such as smoking activity and the volume and air exchange rate of the home. We conducted 300 air exchange rate experiments in two homes on the effect of external window and door positions on air flow and consequent pollutant concentration profiles. We found that even small door openings erase differences between smoking and nonsmoking rooms, whereas tightly closed interior doors provide effective separation. We developed mathematical multi-room indoor air quality models that allow us to generalize our empirical findings. We also analyzed population survey data that provided detailed information on human activity patterns. These were large surveys that recorded the trajectories of individuals through time together with information on ETS exposure. The survey data were combined with our measurements of ETS pollutant concentrations in different environments to produce a population exposure model. Our computer model predicted that an appreciable percentage of Californians living in homes with smokers will experience exposures that exceed the annual average EPA health-based standard for fine particles, while ETS fine particle exposure would not often exceed the 24-hour standard. Our model also demonstrates the important role of ETS exposure in vehicles. During this research grant, we made 6 presentations at scientific meetings and completed 8 scientific papers published in peer-reviewed journals on air pollution, exposure assessment, epidemiology, and public health. Our work to date points to an urgent need for further research on in-vehicle exposures to ETS, multi-compartment modeling of homes, and demographic-based modeling of ETS exposure.

Measurements and laplace transform models for the home: a multi-compartment model for predicting indoor environmental tobacco smoke concentrations
Periodical: Journal of the Air and Waste Management Association Index Medicus:
Authors: Ott W, Klepeis N, Switzer P ART
Yr: 0 Vol: Nbr: Abs: Pg:

The effect of cigar smoking on indoor air quality
Periodical: Journal of Exposure Analysis and Environmental Epidemiology Index Medicus:
Authors: Klepeis N, Ott W, Repace J ART
Yr: 0 Vol: Nbr: Abs: Pg:

Smoking cessation after surgery: a randomized trial
Periodical: Proceedings of the TRDRP Annual Investigator's Meeting Index Medicus:
Authors: Simon JA, Solkowitz SN, Carmody TP, Browner WS ABS
Yr: 1997 Vol: Nbr: Abs: 6D Pg: 27

The effect of cigar smoking on indoor levels of carbon monoxide and particles
Periodical: Journal of Exposure Analysis and Environmental Epidemiology Index Medicus:
Authors: Klepeis NE, Ott WR, Repace JL ART
Yr: 1999 Vol: 9 Nbr: 1 Abs: Pg: 622-635

Assessment of indoor fine aerosol contirbutions from environmental tobacco smoke and cooking with portable nephelometer
Periodical: Journal of Exposure Analysis and Environmental Epidemiology Index Medicus:
Authors: Brauer M, Hurtle R, Lang B, Ott W ART
Yr: 2000 Vol: 10 Nbr: Abs: Pg: 136-144

An introduction to the indirect exposure assessment approach: modeling human exposure using microenvironmental measurements and recent national human activity pattern survey
Periodical: Environmental Health Perspectives Index Medicus:
Authors: Klepeis NE ART
Yr: 1999 Vol: 107 Nbr: 2 Abs: Pg: 365-374

Validity of the uniform mixing assumption: determining human exposure to environmental tobacco smoke
Periodical: Environmental Health Perspectives Index Medicus:
Authors: Klepeis NE ART
Yr: 1999 Vol: 107 Nbr: 2 Abs: Pg: 357-363

The national human activity pattern survey (NHAPS): A resource for assessing exposure to environmental pollutants
Periodical: Journal of Exposure Analysis and Environmental Epidemiology Index Medicus:
Authors: Klepeis NE, Nelson WC, Ott WR, et al ART
Yr: 2001 Vol: 11 Nbr: Abs: Pg: 231-252

Mathematical models for predicting indoor air quality from smoking activity
Periodical: Environmental Health Perspectives Index Medicus:
Authors: Ott WR ART
Yr: 1999 Vol: 107 Nbr: 2 Abs: Pg: 375-381