Functional group characterization of indoor, outdoor, and personal PM: results from RIOPA

Fourier transform infrared (FTIR) spectra of outdoor, indoor, and personal fine particulate matter (PM(2.5)) samples were collected during the Relationship of Indoor, Outdoor, and Personal Air (RIOPA) study. FTIR spectroscopy provides functional group information about the entire PM(2.5) sample without any chemical preparation. It is particularly important to characterizing the poorly understood organic fraction of PM(2.5). To our knowledge this is the first time that FTIR spectroscopy has been applied to a PM(2.5) exposure study. The results were used to chemically characterize indoor air and personal exposure. Sulfate was strongest in outdoor samples, which is consistent with the generally accepted understanding that sulfate is of outdoor origin. Absorbances attributed to soil dust were also seen in many outdoor and some indoor and personal samples. Inorganic nitrate absorbances were a common feature of many California and some New Jersey samples. Carbonyl absorbances showed substantial variation in strength, number of peaks, and wave number shift between samples, indicating variability in composition and sources. Absorbances attributed to aliphatic hydrocarbon and amide functional groups were enhanced in many personal and indoor samples, which suggested the influence of indoor sources in these homes. We speculate that meat cooking is one possible source of particulate amides.

PRACTICAL IMPLICATIONS

To our knowledge this is the first time that FTIR spectroscopy has been used to characterize the composition of indoor and personal PM(2.5). The presence of sulfate, nitrate, ammonium, soil dust and a number of organic functional groups are all detected in one analysis on filter samples without extraction or other sample preparation. Differences between indoor and outdoor spectra are used to identify spectral features due to indoor-generated PM(2.5). Particularly interesting are the much larger aliphatic absorbances, shifts in carbonyl absorbances, and occasional small amide absorbances found in indoor and personal spectra but rarely in outdoor spectra. These observations are important because organics make up a large portion of PM(2.5) mass and their composition and properties are poorly characterized. The properties and behavior of organic compounds in airborne particles are often predicted based on their functional group composition. This analysis begins the development of a better understanding of the functional group composition of indoor and personal PM(2.5) and how it differs from that of outdoor PM(2.5). Eventually this will lead to an improved understanding of the properties, behavior and effects of PM(2.5) of indoor and outdoor origin.

A survey of personal exposures to benzene in Mexico City

Benzene is a widely distributed environmental contaminant that causes leukemia. It is an important component in gasoline, it is used frequently as a solvent or chemical feedstock in industry, and it is emitted as a product of incomplete combustion. In Mexico City, investigators suspect that benzene exposure might be elevated and may pose a risk to the population; however, no published data are available to confirm or disconfirm this suspicion. We, therefore, conducted a survey in 3 occupational groups in Mexico City. Forty-five volunteers who used portable passive monitors measured their personal exposure to benzene during a workshift. None of the participants smoked during the monitoring period. Benzene exposure was significantly higher among service-station attendants (mean = 359.5 microg/m3 [standard deviation = 170.4 microg/m3]) than among the street vendors (83.7 microg/m3 and 45.0 microg/m3, respectively) and office workers (45.2 microg/m3 and 13.3 microg/m3, respectively). However, the benzene exposure levels observed among office workers were substantially higher than levels reported elsewhere for general populations. Our results highlight the need for more complete studies by investigators who should assess the potential benefits of setting environmental standards for benzene in Mexico.

Environmental exposure to volatile organic compounds among workers in Mexico City as assessed by personal monitors and blood concentrations

Benzene, an important component in gasoline, is a widely distributed environmental contaminant that has been linked to known health effects in animals and humans, including leukemia. In Mexico City, environmental benzene levels, which may be elevated because of the heavy traffic and the poor emission control devices of older vehicles, may pose a health risk to the population. To assess the potential risk, portable passive monitors and blood concentrations were used to survey three different occupational groups in Mexico City. Passive monitors measured the personal exposure of 45 workers to benzene, ethylbenzene, toluene, o-xylene and m-/p-xylene during a work shift. Blood concentrations of the above volatile organic compounds (VOCs), methyl tert-butyl ether, and styrene were measured at the beginning and the end of a work shift. Passive monitors showed significantly higher (p > 0.0001) benzene exposure levels among service station attendants (median = 330 microg/m3; range 130-770) as compared to street vendors (median = 62 microg/m3; range 49-180) and office workers (median = 44 microg/m3, range 32-67). Baseline blood benzene levels (BBLs) for these groups were higher than those reported for similar populations from Western countries (median = 0.63 microg/L, n = 24 for service station attendants; median = 0.30 microg/L, n = 6 for street vendors; and median = 0.17 microgr;g/L, n = 7 for office workers). Nonsmoking office workers who were nonoccupationally exposed to VOCs had BBLs that were more than five times higher than those observed in a nonsmoking U.S. population. BBLs of participants did not increase during the work shift, suggesting that because the participants were chronically exposed to benzene, complex pharmacokinetic mechanisms were involved. Our results highlight the need for more complete studies to assess the potential benefits of setting environmental standards for benzene and other VOCs in Mexico.

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.

Role of exposure databases in risk management

Despite the development of numerous national exposure-related databases, exposure assessment remains a weak link in the chain of risk assessment and risk-management activities. Most databases include measures of environmental releases or concentrations of pollutants in specific media, but do not include actual measures of exposure. If accurate estimates of exposure experienced by populations or individuals are absent, it is impossible to judge the effectiveness of risk-management strategies. The Risk Management Work Group evaluation identified the following needs: refinement of measurements of total exposure experienced by individuals, improved characterization of the distribution of exposures in the population, longitudinal monitoring of exposure trends, and improved information about the public health implications of exposure. Recommendations are presented with the hope that the utility of existing databases will be improved and that future initiatives will be developed that meet the needs of risk management.

The new standard environmental inventory questionnaire for estimation of indoor concentrations

Several investigators have developed indoor air quality questionnaires for use in field studies. The approach used in many of them have numerous features in common, but most of them are unique in their content (wording, format, item selection). It is thought that indoor air quality research could be greatly advanced if the primary or fundamental questions and instruments could be consolidated. The use of a basic set of "standard" questions would permit intercomparison of results from different research studies. It is generally agreed that environmental inventory questionnaires (EIQ) help to classify, at least in screening, relative concentration estimates, which precede exposure estimation. Thus, such instruments are not equivalent to monitoring for exposure assessment. However, data linkage and mega data bases are important for some comparative analyses of exposure assessment and exposure-response relationships. Standard instruments such as the EIQ are useful as a screening device to precede other tests to allow identification of potentially high exposure situations. They can also amplify information from other tests. General usage of standard questionnaires and protocols can lead to cumulative improvements in data collection, specificity and effectiveness. This has been the rationale for the present efforts by investigators to form a standardized environmental inventory questionnaire, under the auspices of the U.S. Environmental Protection Agency (EPA), Gas Research Institute (GRI), and Electric Power Research Institute (EPRI).

Assessment of the health effects of atmospheric sulfur oxides and particulate matter: evidence from observational studies

Steadily rising energy costs have increased the need for reliable information on the health effects of atmospheric sulfur oxides and particulate matter. Because ethical and practical considerations limit studies of this question under controlled conditions, observational studies provide an important part of the relevant information. This paper examines the currently available epidemiologic evidence from population studies of the health effects of these pollutants. Nonexperimental studies also have important limitations, including the inability to measure accurately the exposure burden of free living individuals, and the potential for serious confounding by other factors affecting health. We begin with a discussion of some of these methodologic issues. The evidence is then reviewed, first in association with fluctuations in 24 hr mean concentration of sulfur oxides and particulate matter, and then in association with differences in mean annual concentration. In the last section, this evidence is summarized and used to approximate the exposure-response relationship linking pollutant concentrations with mortality and morbidity levels.