Grantee Research Project Results
1997 Progress Report: Longitudinal Studies of Indoor Air Quality in Office Buildings
EPA Grant Number: R825272Title: Longitudinal Studies of Indoor Air Quality in Office Buildings
Investigators: Batterman, Stuart A. , Franzblau, Alfred , Baker, Wayne
Institution: University of Michigan
EPA Project Officer: Chung, Serena
Project Period: July 1, 1997 through June 30, 2000 (Extended to June 30, 2002)
Project Period Covered by this Report: July 1, 1997 through June 30, 1998
Project Amount: $430,000
RFA: Air Quality (1996) RFA Text | Recipients Lists
Research Category: Air , Air Quality and Air Toxics
Objective:
This study addresses relationships between indoor air quality (IAQ), occupant health and comfort, and mitigation strategies. The major objectives are to relate direct measurements of IAQ to building-related illness (BRI) and sick building syndrome (SBS), and to increase the understanding of the relationships between occupant health, building system operation, and air quality.
The study uses a series of controlled interventions in large, mechanically ventilated office buildings with simultaneous measurements of IAQ parameters and surveys of occupant health and perception. The experimental interventions may include variations in fresh air exchange; ventilation rates; heating, ventilation, and air conditioning (HVAC) scheduling/operation; humidity; night-time purge; filtration; and cleaning. A psychosocial survey accounts for job-related and personal co-factors that may affect reporting results of the IAQ and symptom survey. The blind, controlled, and repeated measures of the study are designed to provide high discriminatory power; experimental controls and carefully controlled interventions will minimize effects of confounding factors. Statistical analyses of survey results, in conjunction with various IAQ indicators, will adjust for confounding and will indicate controlling factors.
The study should help to identify and quantify effects of various indoor pollutants and potential mitigation strategies, and should help to improve protocols for building investigations.
Progress Summary:
Building Selection
Building selection is a critical factor for this study as it determines: (1) the study population; (2) the feasible interventions; and (3) current IAQ exposures. After site visits and detailed examination of a number of candidate buildings, we selected building ISR-2 on the University of Michigan campus. This six-story building (including an occupied basement) was constructed in 1982. The building dimensions are approximately 56' x 115', and the total occupied area is approximately 40,000 ft2. Floors 2-5 contain mostly small office spaces and open areas targeted for study. Each floor contains 45-60 individuals, giving a total target population of about 240; however, many of the individuals work part-time. For those working more than 20 hours per week in the building, defined as a minimum qualification, the population is approximately 100 to 120. This building is connected to two other buildings (ISR-1 and ISR-3).
One of the major advantages of the selected ISR-2 building is the ability to manipulate the HVAC systems. The building utilizes five nearly identical variable air volume air-handling units (AHU). A 14,000 cfm AHU handles the basement and first floor. The remaining floors use separate 9,000 cfm AHU located on the same floor. The air intake for the five AHUs is a common vertical louver on the building's west side; the relief is a similar vertical louver located nearby. The reliefs are located above a loading dock, and the intakes around a corner of the building; the proximity of the intake to the loading dock has occasionally resulted in complaints due to odor. The HVAC systems utilize pleated prefilters and medium efficiency bag filters. Carbon impregnated prefilters have been used to control odors. The AHUs have sufficient room to install monitoring equipment and possibly additional filtration equipment upstream of the pre- and bag filters. Past the filters and heating/cooling decks, direct steam humidification is available, although not normally utilized. The mechanical rooms are clean and relatively spacious. Each system is equipped with direct digital control (DDC) systems linked to a central computer. The older, mechanical gauges remain in place and are functional. The DDC system monitors and controls temperatures, airflows, humidity, and damper positions.
A major advantage of the selected building is the ability to provide independent control of IAQ parameters for each floor. This will allow for good control of interventions and comparisons between experimental and control populations, and thus will facilitate the blind, crossover design for the intervention studies. Interventions will be performed by modifying operations on floors 2 and 4 simultaneously, with floors 3 and 5 acting as controls, and then vice versa for the crossover intervention. The effect of the intervention can be judged by comparing responses of the two "case" floors undergoing the intervention with responses from the two "control" floors. Responses include both IAQ monitoring results and occupant surveys. In addition, comparisons between floors 2 and 4, and comparisons between 3 and 5, will allow us to determine whether a "floor effect" exists.
The ground level floor differs from other floors in that it has greater occupant traffic leading to elevators and stairs, and its doors allow largely uncontrolled entry of outside air, dust, etc. This floor will not be examined. All of these features should increase the statistical power of the study.
IAQ Monitoring
This project involves a variety of IAQ monitoring, including continuous, integrated, and grab sampling. The integrated and grab sampling approaches are standard. Three identical systems are being developed to provide continuous monitoring of eight environmental parameters:
· Temperature is continuously measured using a solid state device (Omega HX93V).
· Relative humidity is continuously measured using a capacitive solid
state device (Omega HX93V).
· Carbon dioxide is continuously measured using nondispersive infrared
detector (Vaisala GMW21).
· Illuminance is continuously measured using a solid state photodetector (Extech Instruments 401021 Light Adaptor).
· Sound pressure level is continuously measured using a microphone with appropriate frequency response and damping (Radio Shack Analog Sound Level Meter, 33-2050).
· Total volatile organic compounds (TVOCs) are continuously measured using a photoionization detector (RAE Systems ModuRAE, PDM-10A). Speciated VOCs also will be monitored with collection using a sorbent tube and laboratory analysis using GC/MS.
· Particulate concentration is measured using a semicontinuous method based on the pressure drop across a filter. This approach is under development and evaluation. Currently, characteristic pressure drop curves, as a function of filter loading, are being tested using an aerosol generation system. As a backup, each system also will collect a conventional low-flow filter sample from which concentrations are quantified gravimetrically.
· Motion is continuously measured utilizing a differential infrared sensor (Radio Shack Passive Infrared Motion Sensor, 49-208). This technology is commonly used in intruder alert systems. This sensor indicates human activity near the monitoring location. The system is configured to provide sensitivity in a wide aperture and an adjustable distance. The instantaneous response obtained from the sensor is integrated and dampened using a low-pass filter. The final output signal is proportional to the amount of activity within the sensing region. Although this approach does not strictly quantify the number of individuals near the monitoring location, it does indicate activity near the monitoring site that may affect monitoring results. This approach is innovative in the context of IAQ investigations.
Each sensor is interfaced to a data acquisition system consisting of an 8-channel 12-bit analog-to-digital card (Computer Boards PCM-DAS08), a laptop PC (Hitachi Vision Book Plus 4140X), and software (Labtech Notebook Pro v.10.0). The sensors, interface circuitry, PC, and related equipment are housed inside an enclosure designed to accommodate requirements for component cooling, power, airflow, and security. The enclosure will occupy about 2 cubic feet.
Calibration methods have been developed for most of the sensors. Some additional damping (using low pass filters) may be necessary to reduce instrument noise. Standard protocols are being developed for laboratory and field calibration. Standard operating protocols (SOPs) have been developed for the setup and configuration of the A/D systems.
The data acquisition hardware and software have been configured to record at 1 Hz, and average and log files contain 1 minute and 1 hour averages. This numerical information is then written in ASCII format to a unique log file, which is created at the beginning of each day and closed at the end of the day, to minimize data loss in case of a catastrophic event such as a power failure. The log files consist of nine tab delineated columns of numbers, each column corresponding to the block-averages of the analog voltage output of each sensor, plus a time column recording the time of day each set of entries is written to the file. This numerical information is readily imported into the Excel spreadsheet application where it then is converted to relevant values (e.g., ppm) using information obtained during the calibration procedures. The converted values then are trended as scatter plots, with time as the ordinate and the converted value(s) as the abscissa. The trends then are displayed using identical time scales so as to facilitate comparison of variables. In addition to trending, this data format readily lends itself to statistical analysis using functions bundled into Excel or other statistical analysis applications.
Occupant Survey
Several questionnaires will be administered to building occupants to gather information regarding: (1) demographics; (2) medical history; (3) symptoms and environmental perceptions (e.g., odors, irritants); and (4) psychosocial factors (e.g., information needed to construct a social network analysis). The initial questionnaire to be administered to occupants is fairly lengthy (18 pages), but is very comprehensive, innovative, and is the result of an extensive review of the literature. The followup survey, which will be administered during each intervention, is short (3 pages) and focuses on symptoms and perceptions.
Both questionnaires have undergone extensive revision and many iterations. These new questionnaires recently have been submitted and approved (May 1998) by the University of Michigan Health Sciences Institutional Review Board. (The research as a whole also has been approved by this Board.) The questionnaires are being evaluated in pilot tests using a small group (11 individuals) who will be interviewed individually following the survey administration. The pilot study, which began in April and May 1998 to test instrumentation and questionnaires, will identify potential problems related to the length, wording, confidentiality, ease of completion, etc. If necessary, the survey will be modified following the pilot studies.
Building Interventions
Mechanical drawings, key plans, and other technical information for the case study building have been provided by the University of Michigan Plant Department. Trending of the HVAC system operation at this building has commenced, and a computer file of 15-minute averages of all measured and controlled variables is generated weekly. Also, an energy report for this building is being developed. This information will be used to define the "envelope" for potential building interventions (e.g., changes in ventilation, outside air, humidity, filtration, hours of operation, etc). The interventions must continue to meet minimum air requirements and not impose excessive energy costs.
Several filtration companies have been contacted and are willing to donate materials and services to this project. In particular, we are investigating the feasibility of installing gas-phase filtration systems, which can remove oxidants, sulfur, and VOCs, upstream of the existing particulate filters. We also are investigating the feasibility of retrofitting the existing direct steam injection system using a secondary steam system to avoid problems associated with anticorrosive steam agents (e.g., amines).
Future Activities:
In the future, we will complete further testing and validation of the monitoring systems and additional pilot studies. We also will deploy the monitoring systems in the building, recruit and consent subjects, administer initial and followup surveys, implement the interventions, collect and analyze the data, and complete papers and reports.
Journal Articles:
No journal articles submitted with this report: View all 10 publications for this projectSupplemental Keywords:
indoor air, exposure, health effects, human health, sensitive populations, VOC, survey, social science, epidemiology, monitoring, Midwest, Michigan, MI., Health, Scientific Discipline, Air, Epidemiology, Risk Assessments, indoor air, Atmospheric Sciences, Environmental Engineering, building related illness, fresh air exchange, hvac, office buildings, surveys, occupant health, filtration, ventilation rates, ambient air, workplace, human exposure, mitigation strategies, sick building syndrome, furnaces, indoor air quality, air qualityProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.