Relationships of Indoor, Outdoor, and Personal Air (RIOPA). Part I. Collection Methods and Descriptive Analyses

EPA Grant Number: R828112C130-I
Subproject: this is subproject number 130-I , established and managed by the Center Director under grant R828112
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Health Effects Institute (2000 — 2005)
Center Director: Greenbaum, Daniel S.
Title: Relationships of Indoor, Outdoor, and Personal Air (RIOPA). Part I. Collection Methods and Descriptive Analyses
Investigators: Weisel, Clifford P.
Institution: Rutgers , Health Effects Institute , University of Medicine and Dentistry of New Jersey , Robert Wood Johnson Medical School
EPA Project Officer: Chung, Serena
Project Period: April 1, 2000 through March 31, 2005
RFA: Health Effects Institute (1996) RFA Text |  Recipients Lists
Research Category: Human Health , Air Quality and Air Toxics , Air


Urban populations are exposed to a complex mixture of possibly toxic pollutants generated and emitted by a variety of outdoor and indoor sources. These pollutants occur naturally or result from human activities; they may be present in the form of gases, liquid droplets, or solid particles. The US Environmental Protection Agency (EPA) defines an air toxic as any substance known or suspected to cause harm to humans or the environment. The Clean Air Act Amendments of 1990 list 188 air toxics as hazardous air pollutants; these include volatile organic compounds (VOCs), carbonyls (aldehydes and ketones), and components often associated with particulate matter (PM). The Amendments require the EPA to evaluate the possible health risks from air toxics and, if appropriate, control their ambient levels. To achieve this objective, the EPA identified pollutants that may be most hazardous to health and categorized them as urban air toxics (emitted from all sources) or mobile-source air toxics; some pollutants appear on both lists. Currently, the EPA regulates ambient levels of fine PM through the National Ambient Air Quality Standards for PM2.5 (PM of 2.5 µm or smaller).

Understanding personal exposures to both air toxics and PM—and how different sources contribute to individual exposures—has been considered an important first step in assessing the possible public health risks from these species in the urban environment. The Relationships of Indoor, Outdoor, and Personal Air (RIOPA) study was designed to provide such information for a large number of VOCs and carbonyls, including some that are listed as urban and mobile-source air toxics, and for PM2.5.


The investigators measured indoor, outdoor, and personal exposure concentrations of 16 VOCs, 10 carbonyls, and PM2.5 during two 48-hour sampling periods in different seasons between the summer of 1999 and the spring of 2001. The study included 100 homes with 100 adult residents in each of three cities with different air pollution sources and weather conditions: Los Angeles CA, Houston TX, and Elizabeth NJ. Homes were selected by distance from various sources.

In this report the investigators (1) compare concentrations of the pollutants measured in indoor, outdoor, and personal air (within the subject’s breathing zone), and in vehicles for carbonyls; (2) examine the effects of city, season, type of home, and other variables on measured concentrations; and (3) quantify how much outdoor sources contributed to the indoor concentrations using measurements of outdoor–indoor air exchange rates.

The VOCs measured include
• some on the EPA’s list of urban air toxics (benzene, carbon tetrachloride, chloroform, trichloroethylene);
• some on the EPA’s list of mobile-source air toxics (benzene, chloroform, ethyl benzene, MTBE, m- & p-xylenes, o-xylene, styrene, and toluene); and
• some that originate primarily from indoor sources (a-pinene, ß-pinene, and d-limonene).

The carbonyls measured include
• some from the EPA’s lists of urban air toxics and mobile-source air toxics (acetaldehyde and formaldehyde);
• several that are present at low levels in mobile source emissions (acrolein, butyraldehyde, crotonaldehyde, hexaldehyde, isovaleraldehyde, propionaldehyde, and valeraldehyde); and
• two that are primarily formed as a result of photochemical reactions with hydrocarbons (glyoxal and methylglyoxal).

The investigators used passive organic vapor monitors to collect VOC samples. For carbonyls, they used two sampling methods: a conventional active sampler and a new passive sampler that was developed as part of the study. The new sampler performed better for several carbonyls and was used most; therefore the Investigators Report presents only the analyses and conclusions based on the passive samples. For PM2.5, indoor and outdoor samples were collected on filters mounted in a Harvard impactor; personal samples were collected on smaller filters mounted in a personal monitor.

Expected Results:

The homes and subjects selected did not proportionally represent the greater population. Rather, homes close to sources were preferentially sampled in order to examine the impact of possibly high exposures. In addition, the characteristics of the subjects and the homes differed among cities. Thus comparing results among the three areas, extrapolating the numeric results obtained in this study to the general population, or attributing them to a given city or region must be considered with caution.

The analyses of the aggregate data suggest some trends that will need to be verified with more detailed analyses. With a few exceptions, mean and median personal exposure and indoor concentrations of VOCs and carbonyls were higher than the outdoor concentrations within each city and for the whole data set. Personal PM2.5 concentrations were higher than indoor and outdoor concentrations. The finding that personal exposure concentrations were higher than outdoor concentrations for many compounds indicates that indoor sources contribute to, and in some cases dominate, personal exposures; this is consistent with results from other studies.

Several VOCs were present only at low levels in all environments and were not detected in many outdoor samples. The species detected in more than 60% of outdoor samples common to all three cities were MTBE, carbon tetrachloride, benzene, ethyl benzene, m- & p-xylenes, and o-xylene. MTBE had the highest outdoor concentrations. Although cities with different types of sources were chosen and homes near sources were preferentially sampled, the ranges of outdoor VOC concentrations were generally similar in the three cities. The median outdoor concentrations of carbonyls were more variable than VOCs across the cities (with the exception of formaldehyde).

Indoor concentrations of several VOCs and carbonyls differed among cities. The species with the highest indoor concentrations were the VOCs MTBE, toluene, a-pinene, and d-limonene and the carbonyls formaldehyde, acetaldehyde, and acetone. Personal exposure concentrations for several VOCs and some carbonyls also differed among cities.

Among the three cities, differences in indoor and outdoor PM2.5 levels were slight, but differences in personal PM2.5 exposures were more pronounced.

The analyses of the outdoor contributions to indoor air suggested that some VOCs (MTBE, benzene, carbon tetrachloride, and trichloroethylene) were primarily generated outdoors and contributed 90% to 100% of the indoor concentrations. Outdoor concentrations of other VOCs (chloroform, a-pinene, ß-pinene, and d-limonene) and most carbonyls (including formaldehyde, acetaldehyde, and hexaldehyde) contributed less to indoor air (13% to 43% of indoor concentrations). The carbonyls that contributed most were acrolein, crotonaldehyde, and propionaldehyde (50% to 63%). For PM2.5, outdoor air contributed 60% of the indoor concentration.

Supplemental Keywords:

Health Effects, Air Toxics, VOCs, urban air toxics, indoor air, epidemiology, MTBE, benzene, carbonyls, mobile-source air toxics  

Relevant Websites: Exit

Progress and Final Reports:

  • 2000
  • 2001
  • 2002
  • 2003
  • Final

  • Main Center Abstract and Reports:

    R828112    Health Effects Institute (2000 — 2005)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R828112C042 Does Inhalation of Methanol Vapor Affect Human Neurobehavior?
    R828112C043 Human Responses to Nitrogen Dioxide
    R828112C044 The Role of Inflammation in Ozone-Induced Lung Injury
    R828112C045 How Does Exercise Affect the Dose of Inhaled Air Pollutants?
    R828112C046 How Do Chemicals in Diesel Engine Exhaust Damage DNA?
    R828112C047 Effect of Nitrogen Dioxide on Bacterial Respiratory infection in Mice
    R828112C048 Effects of Ozone Exposure on Airway Epithelium
    R828112C049 Inhalation of Aldehydes and Effects on Breathing
    R828112C050 Does Ozone Cause Precancerous Changes in Cells?
    R828112C051 Effects of Formaldehyde on Human Airway Epithelial Cells Exposed in a Novel Culture System
    R828112C052 Carbon Monoxide and Cardiac Arrhythmias
    R828112C053 Effects of Formaldehyde and Particle-Bound Formaldehyde on Lung Macrophage Functions
    R828112C054 Mechanisms for Protecting Lung Epithelial Cells Against Oxidant Injury
    R828112C055 Relationship of Nitropyrene-Derived DNA Adducts to Carcinogenesis
    R828112C056 Particle Trap Effects on Heavy-Duty Diesel Engine Emissions
    R828112C057 Carbon Monoxide and Atherosclerosis
    R828112C058 Nitrogen Dioxide and Respiratory Illness in Children
    R828112C059 Noninvasive Methods for Measuring Ventilation in Mobile Subjects
    R828112C060 Oxidant Air Pollutants and Lung Cancer: An Animal Model
    R828112C061 Detection of Carcinogen-DNA Adducts: Development of New Methods
    R828112C062 Effects of Carbon Monoxide on Heart Muscle Cells
    R828112C063 Development of Personal Ozone Samplers: Three Approaches
    R828112C064 Development of Biomarkers to Monitor Carcinogen Exposure
    R828112C065 Effects of Prolonged Ozone Inhalation on Collagen Structure and Content in Rat Lungs
    R828112C065II Prolonged Ozone Exposure and the Contractile Properties of Isolated Rat Airways
    R828112C065III Changes in Complex Carbohydrate Content and Structure in Rat Lungs Caused by Prolonged Ozone Inhalation
    R828112C065IV Genetic Control of Connective Tissue Protein Synthesis After Prolonged Ozone Inhalation
    R828112C065V Pulmonary Function Alterations in Rats After Chronic Ozone Inhalation
    R828112C065VII Prolonged Ozone Exposure Leads to Functional and Structural Changes in the Rat Nose
    R828112C065VIII - IX Studies of Changes in Lung Structure and Enzyme Activitiesin Rats After Prolonged Exposure to Ozone
    R828112C065X An Innovative Approach to Analyzing Multiple Experimental Outcomes: A Case Study of Rats Exposed to Ozone
    R828112C065XI The Consequences of Prolonged Inhalation of Ozone on Rats: An Integrative Summary of the Results of Eight Collaborative Studies
    R828112C066 Interactive Effects of Nitropyrenes in Diesel Exhaust
    R828112C067 Detection of Formaldehyde–DNA Adducts: Development of New Methods
    R828112C068I Comparison of the Carcinogenicity of Diesel Exhaust and Carbon Black in Rat Lungs
    R828112C068II An Investigation of DNA Damage in the Lungs of Rats Exposed to Diesel Exhaust
    R828112C068III No Evidence For Genetic Mutations Found In Lung Tumors From Rats Exposed To Diesel Exhaust or Carbon Black
    R828112C069 Noninvasive Determination of Respiratory Ozone Absorption: The Bolus-Response Method
    R828112C070 The Effects of Inhaled Oxidants and Acid Aerosols on Pulmonary Function
    R828112C071 Biochemical Consequences of Ozone Reacting with Membrane Fatty Acids
    R828112C072 DNA Mutations in Rats Treated with a Carcinogen Present in Diesel Exhaust
    R828112C073 Developmental Neurotoxicity of Inhaled Methanol in Rats
    R828112C074 Methanol Distribution in Non Pregnant and Pregnant Rodents
    R828112C075 Is Increased Mortality Associated with Ozone Exposure in Mexico City?
    R828112C076 Effects of Fuel Modification and Emission Control Devices on Heavy-Duty Diesel Engine Emissions
    R828112C077 Metabolic Studies in Monkeys Exposed to Methanol Vapors
    R828112C078 Effects of Ozone on Pulmonary Function and Airway Inflammation in Normal and Potentially Sensitive Human Subjects
    R828112C079 Improvement of a Respiratory Ozone Analyzer
    R828112C080 Mechanism of Oxidative Stress from Low Levels of Carbon Monoxide
    R828112C081 Long-Term Exposure to Ozone: Development of Methods to Estimate Past Exposures and Health Outcomes
    R828112C082 Effects of Ambient Ozone on Healthy, Wheezy, and Asthmatic Children
    R828112C083 Daily Changes in Oxygen Saturation and Pulse Rate Associated with Particulate Air Pollution and Barometric Pressure
    R828112C084 Evaluation of The Potential Health Effects of the Atmospheric Reaction Products of Polycyclic Aromatic Hydrocarbons
    R828112C085 Mechanisms of Response to Ozone Exposure: The Role of Mast Cells in Mice
    R828112C086 Statistical Methods for Epidemiologic Studies of the Health Effects of Air Pollution
    R828112C087 Development of New Methods to Measure Benzene Biomarkers
    R828112C088 Alveolar Changes in Rat Lungs After Long-Term Exposure to Nitric Oxide
    R828112C089 Effects of Prenatal Exposure to Inhaled Methanol on Nonhuman Primates and Their Infant Offspring
    R828112C090 A Pilot Study of Potential Biomarkers of Ozone Exposure
    R828112C091 Effects of Concentrated Ambient Particles on the Cardiac and Pulmonary Systems of Dogs
    R828112C092 Cancer, Mutations, and Adducts in Rats and Mice Exposed to Butadiene and Its Metabolites
    R828112C093 Effects of Concentrated Ambient Particles in Rats and Hamsters: An Exploratory Study
    R828112C094I The National Morbidity, Mortality, and Air Pollution Study: Methods and Methodologic Issues
    R828112C094II The National Morbidity, Mortality, and Air Pollution Study: Morbidity and Mortality from Air Pollution in the United States
    R828112C095 Association of Particulate Matter Components with Daily Mortality and Morbidity in Urban Populations
    R828112C096 Acute Pulmonary Effects of Ultrafine Particles in Rats and Mice
    R828112C097 Identifying Subgroups of the General Population That May Be Susceptible to Short-Term Increases in Particulate Air Pollution
    R828112C098 Daily Mortality and Fine and Ultrafine Particles in Erfurt, Germany
    R828112C099 A Case-Crossover Analysis of Fine Particulate Matter Air Pollution and Out-of-Hospital Sudden Cardiac Arrest
    R828112C100 Effects of Mexico City Air on Rat Nose
    R828112C101 Penetration of Lung Lining and Clearance of Particles Containing Benzo[a]pyrene
    R828112C102 Metabolism of Ether Oxygenates Added to Gasoline
    R828112C103 Characterization and Mechanisms of Chromosomal Alterations Induced by Benzene in Mice and Humans
    R828112C104 Acute Cardiovascular Effects in Rats from Exposure to Urban Ambient Particles
    R828112C105 Genetic Differences in Induction of Acute Lung Injury and Inflammation in Mice
    R828112C106 Effects on Mice of Exposure to Ozone and Ambient Particle Pollution
    R828112C107 Emissions from Diesel and Gasoline Engines Measured in Highway Tunnels
    R828112C108 Case-Cohort Study of Styrene Exposure and Ischemic Heart Disease Investigators
    R828112C110 Effects of Metals Bound to Particulate Matter on Human Lung Epithelial Cells
    R828112C111 Effect of Concentrated Ambient Particulate Matter on Blood Coagulation Parameters in Rats
    R828112C112 Health Effects of Acute Exposure to Air Pollution
    R828112C113 Benzene Metabolism in Rodents at Doses Relevant to Human Exposure from Urban Air
    R828112C114 A Personal Particle Speciation Sampler
    R828112C115 Validation and Evaluation of Biomarkers in Workers Exposed to Benzene in China
    R828112C116 Biomarkers in Czech Workers Exposed to 1,3-Butadiene: A Transitional Epidemiologic Study
    R828112C117 Peroxides and Macrophages in the Toxicity of Fine Particulate Matter in Rats
    R828112C118 Controlled Exposures of Healthy and Asthmatic Volunteers to Concentrated Ambient Particles in Metropolitan Los Angeles
    R828112C119 Manganese Toxicokinetics at the Blood-Brain Barrier
    R828112C120 Effects of Exposure to Concentrated Ambient Particles from Detroit Air on Healthy Rats and Rats with Features of Asthma or Mild Bronchitis
    R828112C121 Field Evaluation of Nanofilm Detectors for Measuring Acidic Particles in Indoor and Outdoor Air
    R828112C123 Time-Series Analysis of Air Pollution and Mortality: A Statistical Review
    R828112C126 Effects of Exposure to Ultrafine Carbon Particles in Healthy Subjects and Subjects with Asthma
    R828112C128 Neurogenic Responses of Rat Lung to Diesel Exhaust
    R828112C130-I Relationships of Indoor, Outdoor, and Personal Air (RIOPA). Part I. Collection Methods and Descriptive Analyses
    R828112C132 An Updated Study of Mortality Among North American Synthetic Rubber Industry Workers