Relationship of Indoor, Outdoor and Personal Air (RIOPA) study: study design, methods and quality assurance/control results

J Expo Sci Environ Epidemiol

Korn

et al. 2004

Self Cite

247

170

The Relationship of Indoor, Outdoor and Personal Air (RIOPA) study was designed to investigate residential indoor, outdoor and personal exposures to several classes of air pollutants, including volatile organic compounds, carbonyls and fine particles (PM 2.5 ). Samples were collected from summer, 1999 to spring, 2001 in Houston (TX), Los Angeles (CA) and Elizabeth (NJ). Indoor, outdoor and personal PM 2.5 samples were collected at 212 nonsmoking residences, 162 of which were sampled twice. Some homes were chosen due to close proximity to ambient sources of one or more target analytes, while others were farther from sources. Median indoor, outdoor and personal PM 2.5 mass concentrations for these three sites were 14.4, 15.5 and 31.4 mg/m 3 , respectively. The contributions of ambient (outdoor) and nonambient sources to indoor and personal concentrations were quantified using a single compartment box model with measured air exchange rate and a random component superposition (RCS) statistical model. The median contribution of ambient sources to indoor PM 2.5 concentrations using the mass balance approach was estimated to be 56% for all study homes (63%, 52% and 33% for California, New Jersey and Texas study homes, respectively). Reasonable variations in model assumptions alter median ambient contributions by less than 20%. The mean of the distribution of ambient contributions across study homes agreed well for the mass balance and RCS models, but the distribution was somewhat broader when calculated using the mass balance model with measured air exchange rates.

Section: Sample Collectionmentioning

confidence: 99%

Influence of ambient (outdoor) sources on residential indoor and personal PM2.5 concentrations: Analyses of RIOPA data

J Expo Sci Environ Epidemiol

Korn

et al. 2004

Self Cite

247

170

“…Briefly, residential indoor and outdoor PM 2.5 samples were collected from summer, 1999 to spring, 2001 in 212 homes in Houston (TX), Los Angeles County (CA), and Elizabeth (NJ) as part of the RIOPA study (29). One hundred sixty-two of these homes were sampled a second time approximately three months later.…”

Section: Sample Collection and Analysismentioning

confidence: 99%

PM_2.5 of Ambient Origin: Estimates and Exposure Errors Relevant to PM Epidemiology

Polidori

et al. 2005

Environ. Sci. Technol.

Self Cite

Epidemiological studies routinely use central-site particulate matter (PM) as a surrogate for exposure to PM of ambient (outdoor) origin. Below we quantify exposure errors that arise from variations in particle infiltration to aid evaluation of the use of this surrogate, rather than actual exposure, in PM epidemiology. Measurements from 114 homes in 3 cities from the Relationship of Indoor, Outdoor and Personal Air (RIOPA) study were used. Indoor PM 2.5 of outdoor origin was calculated: 1) assuming a constant infiltration factor, as would be the case if central-site PM were a "perfect surrogate" for exposure to outdoor particles; 2) including variations in measured air exchange rates across homes; 3) also incorporating home-to-home variations in particle composition, and 4) calculating sample-specific infiltration factors. The final estimates of PM 2.5 of outdoor origin take into account variations in building construction, ventilation practices, and particle properties that result in home-to-home and day-to-day variations in particle infiltration. As assumptions became more realistic (from the first, most constrained model to the fourth, least constrained model), the mean concentration of PM 2.5 of outdoor origin increased. Perhaps more importantly, the bandwidth of the distribution increased. These results quantify several ways in which the use of central site PM results in underestimates of the ambient PM 2.5 exposure distribution bandwidth. The result is larger uncertainties in relative risk factors for PM 2.5 than would occur if epidemiological studies used more accurate exposure measures. In certain situations this can lead to bias.

“…Gas phase aldehydes (Liu et al, 2006) and volatile organic compounds were also measured. The RIOPA study design is described in detail by Weisel et al (2004).…”

Section: Introductionmentioning

confidence: 99%

Fine organic particulate matter dominates indoor-generated PM2.5 in RIOPA homes

Polidori

J Expo Sci Environ Epidemiol

et al. 2006

Self Cite

Residential indoor and outdoor fine particle (PM 2.5 ) organic (OC) and elemental carbon (EC) concentrations (48 h) were measured at 173 homes in Houston, TX, Los Angeles County, CA, and Elizabeth, NJ as part of the Relationship of Indoor, Outdoor and Personal Air (RIOPA) study. The adsorption of organic vapors on the quartz fiber sampling filter (a positive artifact) was substantial indoors and out, accounting for 36% and 37% of measured OC at the median indoor (8.2 mg C/m 3 ) and outdoor (5.0 mg C/m 3 ) OC concentrations, respectively. Uncorrected, adsorption artifacts would lead to substantial overestimation of particulate OC both indoors and outdoors. After artifact correction, the mean particulate organic matter (OM ¼ 1.4 OC) concentration indoors (9.8 mg/m 3 ) was twice the mean outdoor concentration (4.9 mg/m 3 ). The mean EC concentration was 1.1 mg/m 3 both indoors and outdoors. OM accounted for 29%, 30% and 29% of PM 2.5 mass outdoors and 48%, 55% and 61% of indoor PM 2.5 mass in Los Angeles Co., Elizabeth and Houston study homes, respectively. Indirect evidence provided by species mass balance results suggests that PM 2.5 nitrate (not measured) was largely lost during outdoor-to-indoor transport, as reported by Lunden et al. This results in dramatic changes with outdoor-to-indoor transport in the mass and composition of ambient-generated PM 2.5 at California homes. On average, 71% to 76% of indoor OM was emitted or formed indoors, calculated by (1) Random Component Superposition (RCS) model and (2) non-linear fit of OC and air exchange rate data to the mass balance model. Assuming that all particles penetrate indoors (P ¼ 1) and there is no particle loss indoors (k ¼ 0), a lower bound estimate of 41% of indoor OM was indoor-generated (mean). OM appears to be the predominant species in indoor-generated PM 2.5 , based on species mass balance results. Particulate OM emitted or formed indoors is substantial enough to alter the concentration, composition and behavior of indoor PM 2.5 . One interesting effect of increased indoor OM concentrations is a shift in the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs) from the gas to the particle phase with outdoor-to-indoor transport.