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Biomedical subjects

L Wallace

Publications and source records attributed to L Wallace.

104 records · Page 6Linked to original sources
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Exposures to benzene and other volatile compounds from active and passive smoking.

Personal exposures and breath concentrations of approximately 20 volatile organics were measured for 200 smokers and 322 nonsmokers in New Jersey and California. Smokers displayed significantly elevated breath levels of benzene, styrene, ethylbenzene, m + p-xylene, o-xylene, and octane. Significant increases in breath concentration with number of cigarettes smoked were noted for the first four aromatic compounds. Based on direct measurements of benzene in mainstream cigarette smoke, it is calculated that a typical smoker inhales 2 mg benzene daily, compared to 0.2 mg/day for the nonsmoker. Thus, cigarette smoking may be the most important source of exposure to benzene for about 50 million citizens of the United States. Passive smokers exposed at work had significantly elevated levels of aromatics in their breath. Indoor air levels in homes with smokers were significantly greater than in nonsmoking homes during fall and winter but not during spring and summer. The average annual increase in homes with smokers was 3.6 microgram/m3 for benzene and 0.5 microgram/m3 for styrene--an approximate 50% relative increase in each case. Thus, exposure to benzene and styrene may be increased for the approximately 60% of children and other nonsmokers living in homes with smokers.

Benzene Derivatives↗
PubMedDate not supplied

A linear model relating breath concentrations to environmental exposures: application to a chamber study of four volunteers exposed to volatile organic chemicals.

A linear model relating levels of volatile organic chemicals (VOCs) in exhaled breath to personal exposures at environmental (parts per billion) levels has been developed and evaluated in a chamber study of four human volunteers. The purpose of the model is to allow estimation of VOC concentrations in the body from measurements of exposure, or conversely to estimate previous exposure from a measurement of exhaled breath. The model differs from previous models in considering long-term inhalation at low or moderate concentrations rather than instantaneous intake (as in drug administration) or intermittent exposure at high concentrations (as in occupational situations). The model is based on a mass balance approach using one or more compartments to represent distribution of the chemical in the body. The main observable parameters in the model are the residence times tau 1 in the compartments, their "capacities" Ai, and the fraction f of the parent compound that is exhaled under equilibrium conditions. The basic equations for the one-, two-, three-, and n-compartment cases are derived. Solutions to these equations for the cases of a sudden constant high exposure, a sudden constant low exposure, and a linearly increasing exposure are provided. These solutions can be readily applied to more complex exposure scenarios. The chamber study suggests residence times on the order of a few minutes in the blood and 1-2 hr in the vessel-rich group of tissues. The design of the chamber study did not allow an estimate of the model parameters for fat; a subsequent chamber study has provided initial estimates of 50-100 hr. Field studies of personal exposures and breath concentrations of several hundred persons suggest values of f ranging from 0.1 for xylenes and ethylbenzene to about 0.9 for tetrachloroethylene.

Atmosphere Exposure Chambers↗
PubMedDate not supplied

Personal exposure to airborne particles and metals: results from the Particle TEAM study in Riverside, California.

The PTEAM Study was the first large-scale probability-based study of personal exposure to particles. Sponsored by the U.S. Environmental Protection Agency (EPA) and the Air Resources Board of California, it was carried out by the Research Triangle Institute (RTI) and the Harvard University School of Public Health (HSPH). HSPH designed and constructed a 4-lpm, battery-operated personal monitor for inhalable particles (PM10) that could be worn comfortably for up to 14 hours by persons from 10 to 70 years old. The monitor was worn for two consecutive 12-hour periods (day and night) during the fall of 1990 by 178 participants representing 139,000 nonsmoking residents of Riverside, California. Nearly identical monitors were employed to collect concurrent indoor and outdoor samples. The monitors were equipped with a different sampling nozzle to collect fine particles (PM2.5). Population-weighted daytime personal PM10 exposures averaged 150 +/- 9 (SE) micrograms/m3, compared to concurrent indoor and outdoor concentrations of 95 +/- 6 micrograms/m3. This suggested the existence of excess mass near the person, a "personal cloud" that appeared related to personal activities. Fourteen of 15 prevalent elements also were evaluated in the personal samples. The two major indoor sources of indoor particles were smoking and cooking; even in these homes, however, more than half of the indoor particles came from outdoors, and a substantial portion of the indoor particles were of undetermined indoor origin. Outdoor concentrations near the homes were well correlated with outdoor concentrations at the central site, supporting the idea of using the central site as an indicator of of ambient concentrations over a wider area. Indoor concentrations were only weakly correlated with outdoor concentrations, however, and personal exposures were even more poorly correlated with outdoor concentrations. Elemental profiles were obtained for environmental tobacco smoke (ETS) (major contributions from potassium and chlorine) and cooking emissions (aluminum, iron, calcium, and chlorine). These profiles can be used in future source apportionment studies.

Adolescent↗