Ryan Pb

Ozone Reactive Chemistry on Interior Latex Paint

The heterogeneous chemistry of ozone on interior latex paint was investigated in a tube flow reactor. The emissions of several polar volatile organic compounds (VOCs) including organic acids and carbonyls (aldehydes and ketones) were measured while a glass tube coated with latex paint was exposed to clean air and ozone. Four different commercial brands of latex paint were tested. Formic and acetic acids were not found to be generated via ozone reactions ; however, both were found to off-gas from the latex paints, and the off-gasing increased with increasing relative humidity. The off-gasing rates are large enough, particularly for acetic acid, to impact residential concentrations significantly. Formaldehyde was found to be produced by reactions related to the ozone concentration. There was some evidence that acetaldehyde and acetone may also be produced by processes related to the ozone concentration. A steady-state model is presented that is used to extrapolate the chamber results to a representative indoor environment. The model is based on an experimentally derived parameter termed the VOC formation factor, which is defined as the number of VOC molecules of a particular species formed via an ozone reaction divided by the total number of ozone molecules sticking to the surface. Using this model, it was found that formaldehyde production via ozone reactions is significant enough to impact indoor concentrations of formaldehyde.

Personal Exposure to Nitrogen Dioxide in the Los Angeles Basin

A large scale study of human exposure to nitrogen dioxide (NO2) was conducted in the Los Angeles Basin, the only metropolitan area in the United States that exceeds the NO2 NAAQS. Data are available for a population representative sample of 482 households and 682 individuals. Personal exposures, as well as indoor and outdoor home levels, were monitored using passive time-integrating filter badges. Monitoring extended over a one-year period (May 1987 to May 1988), with each individual providing two consecutive days of data. Information was also collected on activity patterns, household and personal characteristics, and spatial and temporal variables. This paper describes the study design, summarizes the sample characteristics and representativeness, and presents the distribution of personal, indoor, and outdoor NO2 concentrations recorded by the monitors. Over the entire sample, median personal and outdoor levels were 35 ppb; median indoor levels were 24 ppb. Personal exposures for those in homes with gas ranges with pilot lights average 10 ppb greater than those with electric ranges, and 4 ppb greater than those with gas ranges without pilot lights. Forty percent of the variation in indoor concentrations is explained by outdoor levels; 59 percent of the variation in personal exposures is explained by indoor levels; and 48 percent of the variation in personal exposures is explained by outdoor levels.

Modeling ozone deposition onto indoor residential surfaces

Modeling the deposition of pollutants onto surfaces requires the inclusion of two separate components: (1) the transport of the pollutant to the surface and (2) the subsequent uptake of the pollutant onto the surface. The relationship of these two components to the deposition velocity can be written in the form of two resistances corresponding to the two components (i.e., the boundary layer resistance and the surface uptake resistance). In order to calculate the surface uptake resistance, the mass accommodation (or «sticking») coefficient is required. We present an experimental method for determining accurately the mass accommodation coefficient and report the results of measurements on several common indoor surfaces

Indoor/Outdoor Measurements of Volatile Organic Compounds in the Kanawha Valley of West Virginia

The Kanawha Valley region of West Virginia which is comprised of Charleston and surrounding communities is the center of a heavily industrialized area known for its chemical manufacturing. As part of a larger study designed to investigate the impact of the chemical industry on human exposures to volatile organic compounds (VOC), a study of the relationship between indoor and outdoor concentrations was conducted. Thirty-five homes were selected for monitoring from among volunteers; approximately ten in each of three distinct population-industry centers and four outside the Valley to act as controls. Monitoring was performed using passive, badge samplers with a three-week monitoring period. Two separate questionnaires were administered: one for characterization of the residence; and one to characterize source use during monitoring. Participants were also asked to keep a record of their activities with respect to in-home, outdoors and other indoor environments. Analysis of the samplers was performed by solvent extraction followed by gas chromatography using a flame-ionization detector. Results suggest that indoor VOC concentrations are higher than outdoor concentrations. Additionally, certain ventilation-related parameters were identified that afforded some predictive power for indoor concentrations. No statistically significant differences between regions were identified.

Temporal variability of microenvironmental time budgets in Maryland

Information on human time-activity patterns is often required to interpret environmental exposure data fully and to implement exposure assessment models. Data on short-term time-activity patterns for individuals, such as 1-day measurements, are relatively abundant. The reliability of such data for use in chronic exposure (e.g., 1 or more years) assessments performed for evaluation of health risks is not well understood. As part of the NHEXAS-Maryland investigation, daily time budget data for seven microenvironments were collected from 80 people during as many as six 1-week Cycles over a 12-month period. The data were summarized and analyzed statistically by sampling Cycle, day of week, and individual to characterize long-term average microenvironmental time budgets and to identify their determinants. Median times spent in transit, indoors at home, outside at home, indoors at work or school, outdoors at work or school, indoors at other locations, and outdoors at other locations were found to vary significantly, although not substantively in many cases, by time of year (i.e., Cycle), by day of week, and by individuals. Time budgets for most of the microenvironments also exhibited significant variability by gender, age group, education level, annual household income, and work status. The results indicate that short-term (e.g., 1-day) measures of microenvironmental time budgets for individuals are unlikely to be representative of their long-term patterns. Thus, health risk or epidemiological assessments performed for a population mean or specific quantile may be relatively insensitive to when time budget data were collected. However, the accuracy of such assessments performed for individuals is likely to be greatly improved by collection of time budget data from numerous points in time.

Bias due to misclassification of personal exposures in epidemiologic studies of indoor and outdoor air pollution

Abstract In this paper, we examine the nature and magnitude of bias resulting in the estimation of relative health risks ( RR ) and risk differences ( ΔR ) due to misclassifications of exposures and disease. Bias correction expressions depending on the misclassification parameters, sensitivity and specificity, as well as the observed risk indicators, RR or ΔR , are provided. Examples based on predictions of exposures of adults and children to both indoor and outdoor respirable particles suggest the potential for significant bias toward the null, if exposure or disease misclassifications are not properly acounted for in the epidemiologic studies of air pollution health effects.

The Validation of a Passive Sampler for Indoor and Outdoor Concentrations of Volatile Organic Compounds

Volatile organics compounds (VOCs) are ubiquitous in the air we breathe. The use of passive samplers to measure these concentrations can be an effective technique. When exposed for long durations, a passive sampler may be a good tool for investigating chronic exposures to chemicals in the environment. A passive sampler that was designed for occupational exposures can be used as such a tool. Laboratory validation under as many conditions as possible needs to be accomplished so as to characterize the sampler with known parameters. This paper describes the methods and results of an investigation into the validity of using a passive monitor to sample VOCs for a three-week period. Two concentration levels, two relative humidities, and five VOCs were studied. Results indicate that the samplers work best under conditions of high concentration with low relative humidity and low concentration with high relative humidity. For the passive sampler, excluding chloroform, percent deviations from the predicted values varied between -41 and +22 percent; while the values between the passive and the active samplers varied between -27 and +24 percent. Benzene, heptane, and perchloroethylene were sampled with equal precision and accuracy.

The Boston residential NO2 characterization study: I. Preliminary evaluation of the survey methodology.

In conjunction with a large, population-based study of exposures to nitrogen dioxide, a pilot study was performed to evaluate methodological and logistical protocols. Survey research techniques have been applied to the collection of indoor air pollution data in an effort to produce a sample which represents the total population of the Boston Standard Metropolitan Statistical Area (SMSA). Essential sample sizes and the methods used to calculate them are discussed. The results of the pilot study are presented with analysis geared toward evaluating the efficiency of the survey methodology. The results suggest that survey research techniques can be applied to assessment of environmental exposures in general and, specifically, to the characterization of concentrations of nitrogen dioxide in housing units in urban and suburban regions. The results further suggest that an acceptance rate of approximately 60-70 percent can be expected in a survey of this type requiring monitoring protocols within occupied housing units. Additionally, this work suggests area clustering as a logistically efficient method of selecting sampling locations.