William A. Turner

Low Flow Rate Sharp Cut Impactors for Indoor Air Sampling: Design and Calibration

Two single round nozzle impactors have been developed for use in Harvard’s indoor air pollution health study. Both impactors operate at flow rates of 4 L/m and are nearly identical, differing only in their cut sizes of 2.5 μm and 10 μm aerodynamic diameters. Two identical cascaded stages of the same cut size are used to obtain sharp cut-off characteristics. The particles are deposited on impaction plates made of oil impregnated, porous material to reduce particle bounce and are discarded. Only the particles collected on the afterfilter are analyzed. Special care has been taken to collect the particles uniformly on the afterfilter to aid in particle analysis. The jmpactors were calibrated with a vibrating orifice monodisperse aerosol generator. However, due to the sharp cut of the impactors, doublets and triplets in the calibration aerosols, even in small quantities, gave erroneous calibration curves. Therefore, the number of doublets and triplets in the challenging aerosols were measured and appropriate c...

Long-term measurements of respirable sulfates and particles inside and outside homes

The results of extensive indoor and outdoor monitoring for respirable size particles and the sulfate fraction of these particles are reported. These air pollution measurements were obtained in conjunction with an epidemiologic study in six U.S. cities: Portage, Wisconsin; Topeka, Kansas; Kingston/Harriman, Tennessee; Watertown, Massachusetts; St. Louis, Missouri: and Steubenville, Ohio. The major source of indoor particulate matter is cigarette smoke, which contributes approximately 20 μm−3 to the indoor concentrations for each smoker. Even in homes without smokers, indoor particle concentrations equal or exceed outdoor levels. The indoor respirable sulfate concentrations are consistently lower than outdoor concentrations.

Indoor air quality modeling: Compartmental approach with reactive chemistry

Data on indoor/outdoor pollutant and tracer concentrations were collected during different periods in 1981 at a residence in Newton, MA. Special studies within the kitchen were conducted to determine the vertical and horizontal variability of pollutant and tracer gas concentrations. A reactive chemistry model incorporating simplified NOx chemistry was developed to simulate pollutant concentrations indoors. Multicompartmental mathematical modeling tools were also developed and tested to estimate efficiently the effective, emission, ventilation, and removal rates, as well as the intercompartmental pollutant exchange coefficients. Model studies utilizing two- and three-compartment systems and tracer measurements proved that the dynamics of pollutant mixing inside a kitchen is not only complex but may be quite important in controlling spatial and temporal variability of reactive species. Further monitoring and modeling studies to investigate the critical aspects of the short-term dynamics of the reactive pollutants inside homes with gas cooking stoves are recommended.

Winter air quality in a wood-burning community: A case study in Waterbury, Vermont

Abstract The recent upsurge in residential wood combustion has raised questions about potential adverse effects on ambient air quality and public health. Before policymakers can make informed and rational decisions about the need for government intervention, more information is needed concerning the nature and extent of the problem. This paper presents findings from the 1982 Harvard Wood-Burning Study in Waterbury, Vermont. Waterbury, a rural community of about 2000 people, was an ideal location for this investigation because: (1) half of the private residences are heated with wood fuel; (2) frequent winter temperature inversions promote pollution buildup in the valley; (3) there are no major industrial sources and (4) the Vermont Agency of Environmental Conservation has compiled a detailed wood-burning inventory. The ambient air monitoring study, from January to March 1982, emphasized measurements of total, inhalable and respirable particulate matter. Results indicate that 60–70% of the Waterbury aerosol was composed of particles less than 2.5 μm. A combination of indirect evidence suggests that wood burning was the major source of airborne particles in residential sections of the town. Dramatic diurnal variations in particulate concentrations were observed, with peak values at night exceeding afternoon levels by 5- to 10-fold. Both meteorology and emission patterns contributed to observed fluctuations.

An Intercomparison of the Indoor Air Sampling Impactor and the Dichotomous Sampler for a 10-μm Cut Size

As a consequence of the promulgation of the PM-10 (particulate matter {<=} 10 {mu}m aerodynamic diameter) standard by the US Environmental Protection Agency, there is increased use of samplers that collect particles within this range. Further, to support future human health and exposure studies on PM-10, it is necessary to develop samplers that can be used in either the indoor or outdoor environment or both. A low flow rate, sharp cut indoor air sampling impactor (IASI) has been constructed with a single impaction plate and size selectively collects PM-10 mass in indoor environments. It is presently being used in the Total Human Environmental Exposure Study (THEES). In an effort to examine the collection characteristics of the IASI, a field intercomparison study was conducted using both the dichotomous sampler and the IASI. The dichotomous sampler has been routinely used to collect PM-10 in the outdoor atmosphere in anticipation of the PM-10 standard. The results of that intercomparison are reported.

Characterization of indoor air quality in wood-burning residences

Abstract Findings from a residential wood-burning study in Waterbury, VT, are presented, with emphasis on indoor-outdoor comparisons of particle mass, size distribution, and composition. The air monitoring program was carried out from January to March 1982 to evaluate the impact of residential wood combustion on indoor and outdoor air quality. Indoor and outdoor data on respirable particle concentrations were obtained for 24 residences, 19 with wood-burning appliances. This paper focuses on 6 of these homes which were selected for more intensive study, including matched indoor-outdoor particle measurements to determine elemental composition, individual polycyclic aromatic hydrocarbon concentrations, and organic- and elemental-carbon content. Data are presented comparing particle-phase organic and elemental concentrations between indoor and outdoor environments.

Design and Performance of a Reliable Personal Monitoring System for Respirable Participates

The Harvard/EPRI personal respirable particulate sampler is a reliable system that provides comparable results to fixed location pulsation free samplers. The flow control design is an improvement that provides assurance that sample flow remains constant over sample periods of at least 12 hr. In addition, the self-contained charging circuitry and lower noise level have eliminated the nuisance characteristics that prevented broader participant acceptance. The Harvard/EPRI pump has been designed to meet the particular sampling requirements of assessing community personal exposures in an epidemiologic air pollution health study.