P. Barry Ryan

Measurement of Organic Acids, Aldehydes, and Ketones in Residential Environments and Their Relation to Ozone

Ozone and several polar volatile organic compounds (VOCs) including organic acids and carbonyls (aldehydes and ketones) were measured over an approximately 24 hour period in four residences during the winter of 1993 and in nine residences during the summer of 1993. All residences were in the greater Boston, Massachusetts area. The relation of the polar VOCs to the ozone concentration was examined. Indoor carbonyl concentrations were similar between the summer and winter, with the total mean winter concentration being 31.7 ppb and the total mean summer concentration being 36.6 ppb. However, the average air exchange rate was 0.9 hr-1 during the winter and 2.6 hr-1 during the summer. Therefore, the estimated carbonyl emission rates were significantly higher during the summer. Indoor organic acid concentrations were about twice as high during the summer as during the winter. For formic acid, the indoor winter mean was 9.8 ppb, and the summer indoor mean was 17.8 ppb. For acetic acid, the indoor winter mean was 15.5 ppb, and the summer indoor mean was 28.7 ppb. The concentrations of the polar VOCs were found to be significantly correlated with one another. Also, the emission rates of the polar VOCs were found to be correlated with both the environmental variables such as temperature and relative humidity and the ozone removal rate; however, it was difficult to apportion the relative effects of the environmental variables and the ozone removal.

The Boston residential NO2 characterization study—II. Survey methodology and population concentration estimates

Abstract A recently completed year-long study of NO2 and air exchange rates in over 500 homes in the Boston Metropolitan area provides data to quantify the component of total NO2 exposures attributable to indoor sources, especially to gas-fired appliances. The approach of this work was to provide field data for validation or refinement of exposure models developed in previous, related work. For an indoor characterization field study, sample sizes of 450 gas- and 150 electric-range-equipped housing units were selected based on: (1) modeled estimation of precision and stability of parameter estimates using various sample sizes; (2) calculations including anticipated attrition from one monitoring period to the next. The sample was selected using standard area probability sampling to allow extrapolations of survey sample results to the larger population. The survey design included stratification by range fuel and area clustering for sampling and logistical efficiency. This paper presents the sampling results and field work progress through the year, with a discussion of response rates typical for exposure monitoring investigations. Monitoring results provide NO2 concentration data to evaluate the overall success of the survey implementation. A series of analyses isolate and quantify the standard errors of distribution estimates. Using sample data weighted for stratification, population exposure distribution parameter estimates are presented. Overall, analyses indicate that key model assumptions are valid. The relatively low standard errors of exposure parameters indicate that the design used in the study was relatively efficient. This illustrates the utility of standard survey research methodology in exposure assessment problems.

Estimated distributions of personal exposure to respirable particles.

A method of estimating distributions of exposure to respirable particles is presented. Using pollutant monitoring data from outdoors and indoors, time-activity data and a time-weighted exposure model, means and variances for exposure distributions are generated. Variances are estimated using Gauss law of error propagation. The model is calibrated using data from a personal monitoring study. Estimated distributions of exposure to respirable particles for children in six cities living in homes with and without smokers are presented. The implications of these estimates for air pollution epidemiology and needs for further research are discussed.

Sequential box models for indoor air quality: Application to airliner cabin air quality

Abstract In this paper we present the development and application of a model for indoor air quality. The model represents a departure from the standard box models typically used for indoor environments which has applicability in residences and office buildings. The model has been developed for a physical system consisting of sequential compartments which communicate only with adjacent compartments. Each compartment may contain various source and sink terms for a pollutant as well as leakage, and air transfer from adjacent compartments. The mathematical derivation affords rapid calculation of equilibrium concentrations in an essentially unlimited number of compartments. The model has been applied to air quality in the passenger cabin of three commercial aircraft. Simulations have been performed for environmental tobacco smoke (ETS) under two scenarios, CO 2 and water vapor. Additionally, concentrations in one aircraft have been simulated under conditions different from the standard configuration. Results of the simulations suggest the potential for elevated concentrations of ETS in smoking sections of non-air-recirculating aircraft and throughout the aircraft when air is recirculated. Concentrations of CO 2 and water vapor are consistent with expected results. We conclude that this model may be a useful tool in understanding indoor air quality in general and on aircraft in particular.

Estimating personal exposures to NO2

Abstract In this work, we present the results in a simulation study of an application of a modeling tool to the problem of estimating human exposure to nitrogen dioxide. The model uses a Monte Carlo approach to simulate a distribution of exposures within a given microenvironment the partial exposure) as well as the impact of the partial exposures to the total exposure distribution. The conditions simulated are meant to be indicative of a range of environments typical of urban and rural United States. Tables are presented of the mean exposure and exposure variance for each of four cases. In addition, the distributions are presented graphically to depict the overlap of exposure classifications.

Observations Less than the Analytical Limit of Detection: A New Approach

Many times in the field of environmental assessment, data are reported from the analytical laboratory as below the limit of detection (

The effects of kerosene heaters on indoor pollutant concentrations: A monitoring and modeling study

Abstract The increase in use of kerosene heaters as a supplementary heat source represents a possible new source of pollutant emissions in the indoor environment. By-products of kerosene combustion including NO 2 and SO 2 may be expected to be present in residences using these appliances. A two-phase study including both monitoring in the field and modeling was undertaken. Monitoring of NO 2 by passive diffusion samplers showed indoor concentrations ranging from 50 to 300 μg m −3 in buildings using these appliances and no other open combustion sources. Modeling of both NO 2 and SO 2 concentrations and exposures suggest the possibility of very high pollutant concentrations in poorly-ventilated or small-mixing volumes.

Development of models for predicting the distribution of indoor nitrogen dioxide concentrations

Extensive data on residential indoor and outdoor NO{sub 2} levels have been collected in a limited number of U.S. locations. To data, researchers have analyzed these data sets individually, but have not analyzed them in the aggregate. Results have not, therefore, been suitable for application in a nationwide exposure assessment. This paper presents an analysis of indoor and outdoor NO{sub 2} field measurements from five U.S. metropolitan areas for homes with gas-fueled ranges and discusses potential applications of the results. Using linear regression analysis, the relationship between indoor NO{sub 2} and various predictor variables was explored. Results indicated that ambient NO{sub 2} levels alone explain an estimated 37 percent of the variability in indoor NO{sub 2} levels, that the relationship between indoor and outdoor NO{sub 2} concentrations differs significantly from summer to winter months, and that homes with range pilot lights have indoor levels approximately 7 ppb greater than homes without pilot lights. A logistic regression model which predicts the distribution of indoor NO{sub 2} levels based on ambient NO{sub 2} concentrations was developed. Estimation and testing of the logistic model indicated good model performance. The model is particularly useful for addressing policy-oriented questions that involve the concept of acceptablemorexa0» threshold levels for human exposure to NO{sub 2}.«xa0less

Source-receptor study of volatile organic compounds and particulate matter in the Kanawha Valley, WV—II. Analysis of factors contributing to VOC and particle exposures

Abstract The Kanawha Valley region of West Virginia includes a deep river valley with a large population living in close proximity to many potential sources of ambient volatile organic compounds (VOCs). The valley runs approximately 100 km from Alloy to Nitro and is between 100 and 200 m deep. Nearly 250,000 people live in this section of the valley, which includes the state capital of Charleston. Many large chemical manufacturing, transportation, and storage facilities are also located within the valleys walls. The topography, population density, and locations of sources dictate the possibility of high population exposures. To investigate exposures to VOCs emitted by the local industry, simultaneous measurements of 19 VOCs, particle pH, particle elemental composition, inorganic gases, and meteorological parameters were collected over an entire year. With the use of a mobile van, sampling was performed in the valley at three sites. Samples were collected for 15 days per month for 4 months at each site. Both unvariate and multivariate analyses were performed in an effort to resolve source contributions. Results of factor analyses suggest auto-related, transported aerosol, chlorinated organic sources as well as site-specific sources and a single incident source—a forest fire. The techniques employed suggest that inclusion of VOC measurements increase the ability of such studies to identify pollutant sources.

Source-receptor study of volatile organic compounds and particulate matter in the Kanawha Valley, WV—I. Methods and descriptive statistics

Abstract The Kanawha Valley of West Virginia is a highly industrialized region stretching 100 km from Alloy in the southeast to Nitro in the north. The valley which contains the state capital, Charleston, has a population of approximately 250,000 and is noted for its chemical manufacturing industry. The valley itself is narrow and steeply-walled. The combination of topography, local meteorological conditions, and the chemical industry potentiate elevated concentrations of volatile organic compounds (VOC) emitted within the region. An integrated approach designed to assess pollutant exposure in this region was implemented between April 1987 and March 1988. Data were collected simultaneously on volatile organic compound concentrations, particle pH, inorganic gases, and meteorological parameters. Data were collected using a mobile van sampling platform at one of the three within-valley sites for 15 days each month. A discussion of sampling methodology and statistics describing pollutant concentrations are presented in this paper. Concentrations of most pollutants were found to be in agreement with those found by other researchers, except during a period when a forest fire influenced the air quality. The results suggest that multivariate relationships may be found that will be useful in source identification.