Modeling of airborne particle exposure and effectiveness of engineering control strategies
Introduction
Maintaining good air quality indoors is important for reducing human exposure, and there is a recommended guideline to provide ventilation, but it focuses on non-residential buildings [1]. The ventilation standards for residences are much less documented. Due to different functional purposes of non-residential and residential buildings, maintaining good air quality becomes more difficult in residential homes. The reason is partly attributed to the fact that some sources of exposures cannot be avoided completely. Environmental tobacco smoke (ETS) and residential cooking have been identified as two major indoor sources for particulate matter. Exposure to ETS is virtually inevitable for every non-smoker, particularly in residences. There is a substantial body of scientific evidence demonstrating that ETS exposure increases risks of many diseases. Epidemiological studies have suggested that exposure of non-smokers to ETS increase their risk of lung cancer [2]. The United States Environmental Protection Agency (USEPA) has estimated that approximately 3000 lung cancer deaths per year result from exposure to ETS [3]. On the other hand, literature data for cooking emission factor is very rare [4], [5]. In addition, results of western style cooking may not be extended to oriental style. For an example, roasting or broiling meat is very common for western food; on the other hand, oriental food prefers pan-frying meat. We decided to estimate the particle emission during cooking by combining two separate studies.
Since both ETS and cooking emission particles pose threat to inhabitants, in order to achieve better indoor air quality, some control measures must be implemented. In general, we can classify them as (1) suppression of the generation rate, or source control; (2) reduction of indoor air contaminant concentration by outdoor air exchange, or dilution control; and (3) removal of indoor air contaminant concentration by air cleaners, or removal control. For multizone environments, additional measures can be implemented to restrict the transport of contaminants to non-contaminated zones, or local segregation. Increased ventilation and indoor air filtration are two commonly used engineering techniques to reduce occupant exposure in residential homes. Unlike cooking whose the location of activity is fixed, smoking can be occurred anywhere in a house. Segregating the smoker from the other occupants can also be an effective means of reducing exposure [6]. In the present paper, we focus our investigations on dilution, segregation and indoor air filtration.
The USEPA has developed a personal computer model, IAQX [7], to predict multizone pollutant concentrations and individual inhalation exposure. Although the model can evaluate multizone concentrations, the inter-zonal flow rates have to be measured or estimated a prior. Several multicompartment flow models have been developed, i.e. CONTAMW [8] and COMIS [9] that can estimate inter-zonal flow rates. In addition to air flow calculations, CONTAMW and COMIS can compute conservative gas pollutant concentrations. In the present work, CONTANW was employed to simulate both air flow and concentration.
For health risk assessment, after obtaining the concentration profile, detailed exposure modeling can be advanced, if necessary. It would be more meaningful to estimate a long-term exposure because there are some external factors which vary significantly with time. The wind pressure-driven ventilation flow depends on both the wind speed and the orientation relative to the residential opening, i.e. open window or leaky crack. The central objective of the present work is to investigate the effectiveness of some engineering controls on inhalation exposure, using ETS and cooking emitted particles as sources. The results will be very useful for exposure assessment and control strategy planning.
Section snippets
Multizone air flow simulation
A multizone infiltration model predicts the infiltration/exfiltration rates and inter-zones air flow rates through links or air flow path between zones. A model is set up by identifying all of the zones of concern and the links between those zones and with the outside environment. CONTAMW is a widely used multizone air infiltration flow and mass transport model. The model is based on conservation of mass in each of the defined zone. CONTAMW predicts inter-zonal air flow rates based on pressure
Results and discussion
There are several ways to express how effective the control strategy on reduction inhalation is, i.e. it can be expressed in terms of absolute or relative measures. In the present work, the main objective is to compare the effectiveness of different scenarios, therefore a relative comparison is more appropriate [23].
The effectiveness of a specific strategy is defined aswhere η is the effectiveness, ABL and Acontrol are the area under curves of the concentration time
Future directions
Although there are a couple of areas that have not been covered in this work, they are still merited for discussion. In this paper, the chemical composition of the sources is not studied. There are a lot of researches on ETS carried out, however, the composition of cooking emission particles is not well understood. Detail composition of the ETS and cooking emission particles should be determined before any in-depth health assessment is performed.
We realize that perfect mixing is not always a
Conclusions
Inhalation of ETS and cooking-emitted particles is almost inevitable in residential environments. There are many factors influencing the total dose inhaled in lung. Physical properties of the particles (i.e. size and density), activities of the resident, ventilation rates (infiltration and exfiltration) and the inter-zonal flow rates all affect the concentration. In the work, we studied the last three parameters in detail. The layout of the room is simple enough, but still preserves the
Acknowledgements
The author wish to thank G.N. Walton (NIST) for his helpful advice in preparing CONTAMW files. He also gratefully acknowledge Adeline Chu and JY Choo (both from NTU) for providing the measurement data and simulation files.
References (24)
COMIS—an international multizone air-flow and contaminant transport model
Energy and Buildings
(1999)- et al.
Control of respirable particles in indoor air with portable air cleaners
Atmospheric Environment
(1985) - ASHRAE. ASHRAE handbook—fundamental. Atlanta, GA, USA: American Society of Heating, Refrigerating and Air Conditioning...
- et al.
Does breathing other people's tobacco smoke cause lung cancer?
British Medical Journal
(1986) - US Environmental Protection Agency (USEPA). Respiratory health effects of passing smoking: lung cancer and other...
- et al.
Gaseous and particulate emission rates for residential food cooking. Engineering solutions to IAQ problems
(1997) - et al.
Size and composition distribution of fine particulate matter emitted from wood burning, meat charbroiling and cigarettes
Environment Science and Technology
(1999) - Miller SL. Characterization and control of exposures to indoor air pollutants generated by occupants. PhD dissertation,...
- Guo Z. Simulation tool kit for indoor air quality and inhalation exposure (IAQX) version 1.0 user's guide....
- Dols WS, Walton GN. CONTANW 2.0 user manual, NISTIR 6476. MD, USA: Building and Fire Research Laboratory, National...
Inhalation transfer factors for air pollution health-risk assessment
Journal of the Air and Waste Management Association
Effectiveness of in-room air filtration and dilution ventilation for tuberculosis infection control
Journal of the Air and Waste Management Association
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