Irwin H. Billick

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.

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.

Rates and mechanisms of NO2 removal from indoor air by residential materials

Recent studies have shown that NO{sub 2} is removed from indoor air more rapidly than by air exchange alone. The relative efficiencies for NO{sub 2} removal by a large number of materials are presented here, along with a discussion of the factors that influence the removal process. This work has demonstrated that reaction with indoor surfaces represents a significant sink for NO{sub 2}, and that these reactions currently are effecting a considerable degree of control over indoor NO{sub 2} levels. It seems likely that this control could be enhanced by judicious selection of furnishings and construction materials. Improved understanding of the rates and mechanisms of the removal process will permit optimization of the process for indoor air quality improvement.

Emission rates from range-top burners—Assessment of measurement methods

Abstract Unvented combustion sources in indoor environments generate emissions that contribute to indoor air pollution. Both the direct and mass-balance methods have been used to measure emission rates from these sources in field houses, test houses and chambers. In particular, emission rates have been obtained for pollutants from kerosene space heaters and from unvented gas appliances such as range-top burners, ovens, dryers and gas space heaters. Most studies have focused on the emission rates of the inorganic air constituents (NO, NO2, CO and a few others). This paper compares the two methods of emission rate measurement, and summarizes the emission rates of NO, NO2 and CO from range-top burners. The emission rates of NO, NO2 and CO from range-top burners are well quantified, but vary widely as a function of the source condition. The experiments described herein found that the two methods provide comparable emission rates. Consequently, in support of the research needed to establish the distribution of emission rates from range-top burners in the U.S. housing stock, the method to be employed should be the one that provides the required information cost effectively.

The areal association of urban air pollutants and residential characteristics: Louisville and Detroit

Abstract Whereas there is substantial literature on the geographic aspects of air pollution and health effects of pollutants, there is a need to identify the specific urban neighbourhoods that are at risk from certain air pollutants. Louisville, Kentucky, and Detroit, Michigan, were selected for analysis because in these cities detailed data existed on mean blood lead levels among children aged 1–72 months. This research demonstrates (1) the dispersion of suspended particulates, sulphur dioxide, nitrogen dioxide, and aerosol lead over the two cities; (2) the distribution of socioeconomic characteristics and mean pediatric blood lead levels for census tracts in these cities; and (3) the statistical association between these pollutants, blood lead levels, and census characteristics. Although it is fallacious to claim, on the basis of this analysis, that lead in petrol is responsible for elevated blood lead among children in Louisville and Detroit, the implication remains that poor inner city residents, particularly children, are at higher risk of ill health due to air pollutants.

Evaluation of NO2 Measurement Methods for Indoor Air Quality Applications

Measurement of nitrogen dioxide (NO2) and other oxidized nitrogen compounds in indoor environments can present some measurement difficulties not normally encountered in sampling outdoor air. This paper examines three methods that are in current use for monitoring indoor nitrogen dioxide. The methods include ozone-based and luminol-based chemiluminescence, and an electrochemical technique. We have examined these methods for accuracy, linear dynamic range, and interferences. Each of the methods was subject to interference. For indoor measurements, nitrous acid probably represents the most significant interference for the ozone-based chemiluminescence and electrochemical monitors.

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.

Effects of Operational Factors on Pollutant Emission Rates from Residential Gas Appliances

The NO, NO2, and CO emissions from residential gas combustion appliances contribute to indoor air pollution. The work described investigated the impact of various unvented gas appliances designs and/or operational factors on pollutant emission rates. All experiments were performed in a 1150 ft3 (32.56 m3) all aluminum chamber under controlled conditions. Results are presented for the effect of the following factors on emission rates: 1) appliance type and/or design, 2) primary aeration level, 3) firing rate (fuel input rate), 4) chamber humidity, and 5) time dependence of emission rates. It is concluded that primary aeration level has the largest impact on pollutant emission rates of range-top burners, followed in turn by firing rate, appliance type, chamber humidity, and time dependence of emission rate.

Causes and consequences of backdrafting of vented gas appliances.

House depressurization occurs when household equipment such as a kitchen or bathroom fan or a fireplace exhausts air from the house and lowers the pressure indoors with respect to the outside. The operation of air handlers for forced-air heating or cooling systems also can have a depressurization effect. This depressurization can hinder the natural draft from vented combustion appliances and lead to backdrafting, which in turn can result in combustion gases spilling into the indoor airspace. Extensive spillage can cause elevated indoor levels of combustion products such as carbon dioxide (CO2) and water vapor, as well as contaminants such as carbon monoxide (CO) and nitrogen dioxide (NO2). The focus of this paper is to review studies on depressurization-induced backdrafting and spillage from gas-fired, drafthood equipped furnaces and domestic hot water heaters. Qualitative and quantitative techniques that were used in depressurization and backdrafting studies conducted in Canada, Europe, and the United States are analyzed. These studies have shown that exhaust fans operated simultaneously with fireplaces depressurize houses by 3 to 8 Pa on average. The CO indoor concentrations due to spillage, as reported in these studies, generally have been lower than 5 ppm. However, such low CO concentrations do not necessarily imply that a potential problem associated with backdrafting does not exist. Other combustion products, such as NO2, rarely have been measured in prior backdrafting studies. It can be concluded from the literature review that causes of house depressurization are well understood. However, more comprehensive research is needed to better understand the frequency, duration, and severity of depressurization-induced spillage in a broad cross section of houses. Efforts in this direction have begun recently in the United States through a workshop to define research issues, pilot studies to develop comprehensive measurement protocols, and consensus standard development activities to prepare standardized methods and protocols.

Emission rates from unvented gas appliances

Abstract The objective of the reported chamber study is to determine the emission rates from unvented gas ranges, unvented space heaters, unvented clothes dryers, and combinations of the above, using the mass balance method. For the range-top burner a complete full factorial design was used. For each condition, every experiment was repeated four times; for a total of 18 conditions, 72 experiments were performed. In addition to emission rates for NO, NO 2 , and CO estimated, a series of special experiments were performed to ascertain the emission rates of volatile organic compounds (VOC), polynuclear aromatic hydrocarbons (PAH), formaldehyde, and total suspended particulate matter (TSP). It is concluded that unvented gas appliances emit NO, NO 2 , and CO at rates similar to corresponding rates found in the literature; the emission rates of VOCs and PAHs are nearly zero and the emission rates of HCHO and TSP are lower than the corresponding rates found in the literature.