Valuing the health benefits of clean air.

An assessment of health effects due to ozone and particulate matter (PM10) suggests that each of the 12 million residents of the South Coast Air Basin of California experiences ozone-related symptoms on an average of up to 17 days each year and faces an increased risk of death in any year of 1/10,000 as a result of elevated PM10 exposure. The estimated annual economic value of avoiding these effects is nearly $10 billion. Attaining air pollution standards may save 1600 lives a year in the region.

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.

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.

Chronic disease associated with long-term concentrations of nitrogen dioxide.

A prospective epidemiologic cohort study of 6,000 residentially stable and non-smoking Seventh-day Adventists (SDA) in California was conducted to evaluate long-term cumulative levels of ambient nitrogen dioxide (NO2) in association with several chronic diseases. These diseases included respiratory symptoms, cancer, myocardial infarction (MI), and all natural causes mortality. Cumulative ambient concentrations of NO2 were estimated for each study subject using monthly interpolations from fixed site monitoring stations and applying these estimates to the monthly residence and work place zip code histories of study participants. In addition, a personal NO2 exposure study on a randomly selected sample of 650 people in southern California was conducted to predict total personal NO2 exposure using household and lifestyle characteristics and ambient NO2 concentrations. It was found that good predictability could be obtained (correlation coefficient between predicted and observed values = 0.79) from a model predicting personal NO2. The resulting regression equations from the personal NO2 exposure study were applied to the epidemiologic study cohort to adjust ambient concentrations of NO2.

California residential air exchange rates and residence volumes.

UNLABELLED: Air exchange rate data from two residential indoor air quality studies are presented. In the first investigation, over 500 residences in Southern California were sampled for three one-week periods from 1984 to 1985. Those data provided seasonal information for a broad range of residential characteristics in a large metropolitan area. In the second study, a probability sample of nearly 300 residences were sampled for a two-day period during the winter of 1991-1992 throughout the state of California. Air exchange rate is summarized by season, geographic area, and appliance type. Residence volumes are presented by cooking and heating appliance. The data approximately followed lognormal distributions. IMPLICATIONS: Indoor air quality and human exposure models often require estimates of air exchange rate and residence volumes. Application of those models to California residences can be improved by using the data distributions provided in this manuscript. Data distributions presented for heating and cooking appliances are useful for modeling the impact of indoor sources specific for those appliance types. Measured air exchange rate is also useful for modeling energy use for heating and cooling in residences.

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.

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.

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

UNLABELLED: 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.

Psychological reactions to air pollution.

Interviews with a large representative sample of Los Angeles residents reveal that these citizens are somewhat aware and concerned about air pollution, but not knowledgeable about its causes. Direct behaviors to reduce causes of pollution or one's exposure to it are rare. A moderate percentage of people seek out information about air pollution or complain about it. Fewer follow state health advisories by reducing automobile driving or restricting activity during air pollution episodes. Preliminary modeling of citizen compliance with air pollution health advisories suggest that personal beliefs about negative health effects are a important predictor of compliance. Finally, modest but significant relationships are noted between ambient photochemical oxidants and anxiety symptoms. The latter finding controls for age, socioeconomic status, and temperature.

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).

Evidence of inadequate ventilation in portable classrooms: results of a pilot study in Los Angeles County.

UNLABELLED: The prevalence of prefabricated, portable classrooms (portables) for United States public schools has increased; in California, approximately one of three students learn inside portables. Limited research has been conducted on indoor air and environmental quality in American schools, and almost none in portables. Available reports and conference proceedings suggest problems from insufficient ventilation due to poor design, operation, and/or maintenance of heating, ventilation and air conditioning (HVAC) systems; most portables have one mechanical, wall-mounted HVAC system. A pilot assessment was conducted in Los Angeles County, including measurements of integrated ventilation rates based on a perfluorocarbon tracer gas technique and continuous monitoring of temperature (T) and relative humidity (RH). Measured ventilation rates were low [mean school day integrated average 0.8 per hour (range: 0.1-2.9 per hour)]. Compared with relevant standards, results suggested adequate ventilation and associated conditioning of indoor air for occupant comfort were not always provided to these classrooms. Future school studies should include integrated and continuous measurements of T, RH, and ventilation with appropriate tracer gas methods, and other airflow measures. PRACTICAL IMPLICATIONS: Adequate ventilation has the potential to mitigate concentrations of chemical pollutants, particles, carbon dioxide, and odors in portable and traditional classrooms, which should lead to a reduction in reported health outcomes, e.g., symptoms of 'sick building syndrome', allergies, asthma. Investigations of school indoor air and environmental quality should include continuous temperature and relative humidity data with inexpensive instrumentation as indicators of thermal comfort, and techniques to measure ventilation rates.

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.