Human Exposure Assessment for Airborne Pollutants Advances and Opportunities (1991) / Chapter Skim
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7 Current and Anticipated Applications
7 Current and Anticipated Applications
Pages 207-256
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From page 207... ...
Discussions of several of the case studies in the context of exposure through environmental media other than air, such as water, food, or soil, relate to the general framework for exposure assessment discussed in Chapter 1. Accordingly, approaches to assess exposure through inhalation should be considered within the framework of total exposure, which accounts for all exposures a person has to a specific compound regardless of environmental medium.
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From page 208... ...
Benzene is used to examine an eyposure-assessment dichotomy found between the TEAM study and EPA's regulatory investigations. Current Approaches to Exposure Assessment Under the Clean Air Act EPA is required, under Section 112 of the Clean Air Act, to establish National Emission Standards for Hazardous Air Pollutants (NESHAP)
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From page 209... ...
The EPA approach to exposure assessment relies heavily on modeling and uses little, if any, actual monitoring data. The human-exposure model combines source emission rates with atmospheric-dispersion equations to predict concentrations of VOC contaminants at various receptor sites In the general population and test the effectiveness of various emission-control strategies.
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From page 210... ...
The TEAM study measured exposure to selected VOCs directly with personal monitors that were worn by subjects. The monitors were designed to be small, and to permit unobtrusive but accurate and precise sampling.
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From page 211... ...
Recently, the TEAM study employed canisters for the indoor measurements. Biological Markers At the outset of the TEAM study, blood samples were taken at the end of the sapling period and analyzed for the selected VOCs.
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From page 212... ...
when filling automobile gas tanks; benzene exposure could often be related to automobile use, which also includes time spent inside of an automobile compartment (Wallace, 1989~. Models No models were used specifically to assess exposure in the TEAM study.
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From page 214... ...
The VOCs examined in the TEAM study were almost exclusively in a single exposure medium (air) , were chemically stable, and had a volatility that permitted their effective collection and concentration with the sorbent Tenax New analytical techniques should be developed to broaden the range of analytes that can be collected and measured, so that the "T" in TEAM will actually stand for "Total," and not for "Targeted compounds," as is now the case.
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From page 215... ...
Unlike active smoking, exposure to ETS cannot now be easily assessed with standardized methods. Prev~ous epidemiological studies of the chronic effects of ETS, particularly lung cancer, have determined exposure solely by questionnaires, which have not been standardized or validated.
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From page 216... ...
They are being applied to test hypotheses ~ epidemiological studies on the relationships between ETS and acute and chronic health and nuisance effects. The methods use advances in the applications of markers or profanes of ETS, air monitoring, modeling, questionnaire survey, and biological markers.
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From page 217... ...
Biological markers of ETS exposure can also vary widely from person to person, because of differences in uptake, distribution, and metabolism. Some markers are not specific for ETS exposure (e.g., carboxyhemogIobin)
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From page 218... ...
They afford an indirect measure of exposure and so cannot provide information on specific exposure magnitudes, although information obtained with them is essential for use In models aimed at predicting ETS concentrations in different environments and total exposure. An effort is under way to develop a standardized questionnaire for estimating indoor concentrations of ETS-related contaminants and personal exposures (Lebowitz et al., 1987~.
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From page 219... ...
In addition, there was also a failure to accurately assess personal exposures to PAHs, and epidemiological studies were based on the assumption that measurements of PAHs in outdoor air yielded a reasonable estimate of total exposures. In the last decade, indoor air has been recognized as much more important in exposure to PAHs because most of the population spends 80-90% of the day indoors.
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From page 220... ...
The 2- and 3-nug PAHs are largely In the vapor phase and can also readily infiltrate into indoor environments. The penetration of particulate BaP has been demonstrated in nonsmoker homes as part of the Total Human Environmental Exposure Study (THEES)
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From page 221... ...
It is difficult and expensive to measure all the PAH compounds in a complex mixture as part of an exposure assessment. Therefore, BaP, an animal carcinogen that is found in all PAH mixtures as a more easily measured indicator compound, has been widely used as a surrogate indicator compound to characterize exposure to many PAHs and other complex mixtures (Santodonato et al., 1981; Osborne and Crosby, 1987)
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From page 222... ...
If one adds an estimate of direct BaP inhalation by smokers in the smoker homes as a separate category, their BaP doses will increase by a factor of more than 5. The second and third phases of THEES included personal and biological monitoring and provided information supporting the importance of food and inhalation routes of exposure and on the utility of current biological markers (Waldman et al., in press)
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From page 223... ...
These artifacts include adsorption of vapors by the filter matrix itself; PAH blow-off losses from or adsorption gains to particles coldected on the filter; and losses of PAHs from chemical reactivity with ozone and other reactive species drawn through the sampler (Van Vaeck et al., 1984; Finlayson-Pitts and Pitts, 1986; Coutant et al., 1988; Ligocki and Pankow, 1989~. Many scientists who sample air believe that an improved way to separate and collect both phases simultaneously would be to use a sampling train with a diffusion denuder followed by a filter and then by a sorbent.
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From page 224... ...
Other analytical methods are being explored for use with urine samples. Mass-spectrometric methods have also been developed for biological markers of PAH exposure (Burlingame et al., 1983~.
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From page 225... ...
Models Several types of models have potential application in community exposure assessments for PAHs. The mass-balance model can be used in various ways to estimate indoor and outdoor inhalation of PAHs.
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From page 226... ...
Some of these components are highly mutagenic and will need to be factored into PAH exposure assessments. In addition, methods that Will minimize or eliminate artifacts during sampling or analysis will have to be developed.
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From page 227... ...
Over the past 2 decades, measurement of airborne lead concentrations has provided a clear method for tracking and enforcing overall reductions in airborne exposure. Despite real success in reducing airborne lead exposure in the United States and concomitant reduction In blood lead, the Agency for Toxic Substances and Disease Registry (ATSDR, 19~)
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From page 228... ...
cities, trends in childhood lead concentrations correlated closely with those of sales in leaded gasoline (NRC, 1980~. At one time, exposure to airborne lead accounted for 40-50% of blood lead in children (ATSDR, 1988~.
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From page 229... ...
1~. AMBIENT AIR LEAD CONCENTRATION : _ l _ ~ _ -LEAD CONSUMED IN GASOLINE 1975 1976 1977 1 978 1 979 1 980 CALENDAR YEAR 1.2 t.t a, : J UJ 1.0 ~ UJ C} MU J lo IS UJ > 0.7 ~ to 0.6 IS a 0.5 ~ X Or 0.4 ~ LO 03 ° o 0.2 0.1 O 1 981 1 982 ~ 983 1 984 FIGURE 7.2 Gasoline lead emissions and outdoor lead concentrations 1975-1984.
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From page 230... ...
230 Ip/B8'Sl3~3l aV31 aoO18 39~3~V __ >I a- I l l l ll I l ~ lo z z go a, :~< cog Or \ J \ ~ ~ Iq~L)
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From page 231... ...
and California (Johnson et al., 1975; CDC, 1985) have shown that children living within 100 feet of major roadways have higher blood lead concentrations than those living farther away.
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From page 232... ...
Whether ingested or inhaled, lead accumulates in the blood, brain, and bone; the proportion retained is greatest after ingestion. In humans recent exposure to lead is commonly measured in terms of blood lead, which indicates exposure in the preceding 4 months.
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From page 233... ...
Thus, in investigations of a neighborhood near a smelter, blood lead concentrations in children were determined by hematofluor~meter evaluations of whole blood drawn by venipuncture, and these were correlated with distance. Models In preparing its justification for the regulation of lead, EPA relied on a series of crude models that correlated gross figures on production of leaded gasoline with estimates of airborne lead and blood lead.
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From page 236... ...
. Recent epidemiological evidence supports the hypothesis that chronic, lowlevel exposure to acidic particles can be associated with respiratory disease.
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From page 237... ...
Therefore it is necessary to examine the occurrence of exposures to and health effects of acidic particles in sensitive groups in the general population. Measurements The chemical variable relevant to health appears to be total particle acidity or sulfuric acid concentration, although the aqueous concentration of hydrogen ion in the airborne particles might be useful.
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From page 238... ...
An important exposure characteristic is particle size. Airborne acidic particles can range in diameter from 0.01 to more than 10 ~m.
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From page 239... ...
The techniques should then be used in epidemiological studies of chronic or acute effects. The results of exposure assessments related to atmospheric acidic species should provide a basis for comparisons of toxicity of acidic mixtures.
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From page 240... ...
SICK-BUILDING SYNDROME Introduction Environmental measurements made during the last decade have revealed that indoor concentrations of some air pollutants are often higher than outdoor concentrations and sometimes even hider than outdoor health-based air quality standards (Spengler and Sexton, 1983; Spengler and Soczek, 1984; Wallace et al., 1986~. Furthermore, other research demonstrates that, on the average, people spend 80-90% of their time indoors (Szalai, 1972; NRC, 1981~.
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From page 241... ...
(1988) have studied SBS through a statistical analysis of chemical concentrations in air samples collected from sick and healthy school buildings Many studies that could be classified as SBS studies have been reported, particularly in the proceedings of three international conferences on indoor air quality since 1981 (International Symposium on Indoor Air Pollution, Health and Energy Conservation, 1981; Third International Conference on Indoor Air Quality and Climate, 1984; and Fourth International Conference on Indoor Air Quality and Climate, 1987~.
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From page 242... ...
(1985) attempted a followup study in which some environmental measurements were made; it included only two buildings, and the measurements were limited to temperature, relative humidity, air velocity, and ion concentrations.
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From page 243... ...
Because so little is known about SBS, any reasonable study will require a plethora of data of diverse categories, such as chemical, biological, physical (ventilation, relative humidity, temperature, noise, light, vibration) , and psychosocial information and information on biological markers.
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From page 244... ...
Although markers have been used extensively in the industrial setting (e.g., blood lead) , not many problem buildings have been studied with markers.
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From page 245... ...
When used specifically as an exposure assessment tool in SBS studies, questionnaires use the respondent as a sensor of the workplace environment to assess such important variables as odor, sound, lighting, comfort, and environment acceptability; to characterize potential sick-building psychosocial factors (such as conflict at work, job satisfaction, and degree of control over work) ; and to provide surrogate measures of off-site (residence, outdoor, transportation, etc.)
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From page 246... ...
, Public Law 99-499, is a free-standing statute titled "The Emergency Planning and Community Right-To-Know Act of 1986". In the development of SARA Section 313, it was acknowledged during discussions in Congress that the extent of human exposure to toxic chemicals released by industry was a major concern Congressional Record, H11205, December 5, 1985~.
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From page 247... ...
To minimize the burden of data-gathering on industry, Section 313 of SARA allows release reports to be based on estimates; monitoring data and other available information are not required, but can be reported if available. Applications to Exposure Assessment Although the TRI provides useful information on estimated mass quantities of chemical releases, it does little to assist in understanding the potential for human exposure to those releases and resulting impacts on public health.
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From page 248... ...
Even the simplest dispersion models cannot be used to estimate downwind concentrations of released toxic chemicals on the basis only of TRI data. The TRI provides some data useful in determining downwind concentrations, such as facility location, latitude and longitude (to assist in describing meteorolog~cal transport)
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From page 249... ...
In the future, acutely and chronically toxic chemicals should be reported separately to allow proper focus of resources on the most important exposure issues. A source and receptor database needed for the proper exposure assessment for both acutely and chronically toxic chemicals should be carefully considered for inclusion in the data-collection effort In any revision of SARA Section 313.
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From page 250... ...
The amount of airborne radon decay products in a room depends on several factors, including the amount of radon to produce them, the concentration of airborne particles to which they can become attached, and the aerodynamic
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From page 251... ...
Exposure to tobacco smoke and differential residential mobility are substantial confounding factors in the estimation of health risk. Two epidemiological studies are attempting to relate lung cancer to environmental radon and decay-product exposure through retrospective measurement of indoor radon concentrations.
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From page 252... ...
A large number of lung cancer cases are available (more than 6,000 through 19843 in an area where there are likely to be high indoor radon concentrations. Separate case series will be defined by histopathological type of lung cancer and by smoking status.
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From page 253... ...
Air cleaners can substantially increase the unattached fraction, so EPA does not recommend the use of air cleaners to mitigate the effects of radon decay products. Models The choice of radon as the measured entity suggests the possibility of an
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From page 254... ...
The Argonne study will be partially supplemented by direct measurement of concentrations of radon decay products although the particle size distributions and their potential influence on dose are not explicit parts of either study. New measurement methods have recently been developed that permit the determination of both concentrations and size distributions of radon decay products.
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From page 255... ...
This system can be used soon to test the variability of concentrations in ~fferent size ranges directly so that a better understanding of the dynamics of inducer radon decay products will be possible.
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