Abstract  A wide variety of surface materials in buildings can release organic compounds. Examples include building materials, furnishings, maintenance materials, clothing, and paper products. These sources contribute substantially to the hundreds of organic compounds that have been measured in indoor air. Their emissions have been directly connected to complaints of odors or hyperreactivity and are presumed to contribute to the problems in many "sick buildings" where the cause of complaints is uncertain. Significant progress has been made in the past decade in developing procedures for measuring emissions from such materials, in controlled experiments where factors affecting emission rates can be determined and quantified. Emissions data are still limited but are being accumulated gradually by research groups in Europe and North America. It is clear from the recent data gathered in research and modeling studies that one of the most effective ways to limit indoor concentrations of organic compounds is to limit the content of volatile compounds in materials that are used in buildings. Limiting the original residual content of such compounds in the materials, or conditioning such materials prior to use in buildings, or (perhaps) conditioning such materials in place before occupancy of a new or renovated building, are most likely to prevent excessive indoor concentrations. If emissions testing and product certification procedures are available and there is sufficient market demand for low-emitting materials caused by indoor air quality concerns, significant reductions of indoor concentrations of vapor-phase organic compounds could be achieved within the next decade.

Abstract  This paper represents the first quantitative attempt to distinguish the amount of outdoor soil ingestion from indoor dust ingestion in a soil pica child. Based on a methodology using a comparison of differential element ratios it is estimated that the predominant proportion of the fecal tracers were from outdoor soil and not indoor dust origin. The methodology employed can be utilized on a broader scale to assess the relative amounts of soil and dust consumed by individuals.

Abstract  Assessments of doses resulting from exposures to airborne gases and particles are based almost exclusively on inhalation rates that are inconsistent with the quantities of oxygen needed to metabolize dietary intakes of fats, carbohydrates, and protein. This inconsistency leads to erroneous estimates of inhalation exposures and can distort the relative importance of inhalation and ingestion-based exposures to environmental contaminants that are present in foods, air, and water. As a means of dealing with this problem, a new methodology for estimating breathing rates is presented that is based on the oxygen uptake associated with energy expenditures and a ventilatory equivalent that relates minute volume to oxygen uptake. Three alternative energy-based approaches for estimating daily inhalation rates are examined: (1) average daily intakes of food energy from dietary surveys, adjusted for under reporting of foods; (2) average daily energy expenditure calculated from ratios of total daily expenditure to basal metabolism; and (3) daily energy expenditures determined from a time-activity survey. Under the first two approaches, inhalation rates for adult females in different age cohorts ranged from 9.7 to 11 m3 d-1, whereas for adult males the range was 13 to 17 m3 d-1. Inhalation rates for adults determined from activity patterns were higher (i.e., 13 to 18 m3 d-1), however, those rates were shown to be quite sensitive to the energy expenditures used to represent light and sedentary activities. In contrast to the above estimates, the ICRP 23 reference values for adult females and males are 21 and 23 m3 d-1 (Snyder et al. 1975). Finally, the paper provides a technique for determining the short-term breathing rates of individuals based on their basal metabolic rate and level of physical activity.

Abstract  This report estimated the amount of outdoor soil in indoor dust in the Calabrese et al. (1989) children soil ingestion study via the use of statistical modelling. The estimate used data on outdoor soil and indoor dust in the homes of 60 children with eight tracer elements (Al, Ba, Mn, Si, Ti, V, Y, and Zr). The model estimated that 31.3% of indoor dust had an origin of outdoor soil. Based on a previous report (Stanek and Calabrese, 1992) on differential soil from dust ingestion in the Calabrese et al. (1989) study and the data of the present analysis, the median outdoor soil ingestion of the Calabrese et al. (1989) study should be revised downward by 35%. For the three most reliable tracers, the median soil ingestion estimates would be reduced from 29 to 19 mg/d for Al, 55 to 36 mg/d for Ti, and 16 to 10 mg/d for, Zr.

Abstract  Among the potential fates of indoor air pollutants are a variety of physical and chemical interactions with indoor surfaces. In deterministic mathematical models of indoor air quality, these interactions are usually represented as a first-order loss process, with the loss rate coefficient given as the product of the surface-to-volume ratio of the room times a deposition velocity. In this paper, the validity of this representation of surface-loss mechanisms is critically evaluated. From a theoretical perspective, the idea of a deposition velocity is consistent with the following representation of an indoor air environment. Pollutants are well-mixed throughout a core region which is separated from room surfaces by boundary layers. Pollutants migrate through the boundary layers by a combination of diffusion (random motion resulting from collisions with surrounding gas molecules), advection (transport by net motion of the fluid), and, in some cases, other transport mechanisms. The rate of pollutant loss to a surface is governed by a combination of the rate of transport through the boundary layer and the rate of reaction at the surface. The deposition velocity expresses the pollutant flux density (mass or moles deposited per area per time) to the surface divided by the pollutant concentration in the core region. This concept has substantial value to the extent that the flux density is proportional to core concentration. Empirically, the problem of human exposure to ozone in commercial buildings has been successfully modeled by using the deposition velocity to parameterize ozone removal onto indoor surfaces. The concept has also been applied in investigations of the indoor dynamics of other pollutant species. However, despite the successful application of this concept, caution is advised in using deposition velocity to characterize pollutant-surface interactions. Limitations that are explored in this paper include these: the presumption of uniform mixing throughout the core region may fail; deposition may vary strongly with position in an enclosure; certain classes of surface-pollutant reactions may not be represented adequately as a first-order loss process; transformation processes within the boundary layer may need to be considered in theoretical investigations; and transport rates through boundary layers may depend strongly on near-surface air flow conditions. Published results from experimental and modeling studies of fine particles, radon decay products, ozone, and nitrogen oxides are used as illustrations of both the strengths and weaknesses of deposition velocity as a parameter to indicate the rate of indoor air pollutant loss on surfaces.

Abstract  BACKGROUND: Contaminated household dust is believed to be a major source of exposure for most children with elevated blood lead levels. To determine if a vigorous dust clean-up effort would reduce this exposure we conducted a randomized controlled field trial. METHODS: We randomized 113 urban children between the ages of 6 and 36 months: 56 children to a lead dust intervention composed of maternal education and biweekly assistance with household cleaning and 57 children to a control group. Household cleaning was done by two trained lay workers who focused their efforts on wet mopping of floors, damp-sponging of walls and horizontal surfaces, and vacuuming with a high-efficiency particle accumulating vacuum. Household dust lead levels, child blood lead levels, and maternal knowledge of lead poisoning and sources of exposure were measured before and after the intervention. RESULTS: Ninety-nine children were successfully followed for 12 +/- 3 months: 46 children in the lead group and 53 children in the control group. Age and blood lead were similar in the two groups at baseline and averaged 20 months and 12.0 micrograms/dL, respectively. Blood lead fell 17% in the intervention group and did not change among controls. Household dust and dust lead measures also fell significantly in the intervention group. Children in homes cleaned 20 or more times throughout the year had an average blood lead reduction of 34%. CONCLUSIONS: Regular home cleaning, accompanied by maternal education, is a safe and partially effective intervention that should be recommended for the large majority of lead-exposed children for whom, unfortunately, removal to lead-safe housing is not an option.

Abstract  This document provides technical support concerning cancer and noncancer risk assessment methods used in the Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (2000) (USEPA, 2000a; hereafter the 2000 Human Health Methodology). Ambient water quality criteria (AWQC) developed under Section 304(a) of the Clean Water Act (hereafter the CWA or the Act) are based solely on data and scientific judgments on the relationship between pollutant concentrations and environmental and human health effects. The 304(a) criteria do not reflect consideration of economic impacts or the technological feasibility of meeting the chemical concentrations in ambient water. As discussed below, 304(a) criteria are used by States and authorized Tribes to establish water quality standards, and ultimately provide a basis for controlling discharges or releases of pollutants.

Abstract  We investigated activity patterns of 17 elementary school students aged 10-12, and 19 high school students aged 13-17, in suburban Los Angeles during the oxidant pollution season. Individuals' relationships between ventilation rate (VR) and heart rate (HR) were "calibrated" in supervised outdoor walking/jogging. Log VR was consistently proportional to HR; although "calibrations" were limited by a restricted range of exercise, and possibly by artifact due to mouthpiece breathing, which may cause overestimation of VR at rest. Each subject then recorded activities in diaries, and recorded HR once per minute by wearing Heart Watches, over 3 days (Saturday-Monday). For each activity the subject estimated a breathing rate--slow (like slow walking), medium (like fast walking), or fast (like running). VR ranges for each breathing rate and activity type were estimated from HR recordings. High-school students' diaries showed their aggregate distribution of waking hours as 68% slow inside, 8% slow outside, 10% medium inside, 9% medium outside, 1.5% fast inside, 1.5% fast outside. Elementary students' distribution was 47% slow inside, 15% slow outside, 20% medium inside, 12% medium outside, 2.5% fast inside, 3.5% fast outside. Sleep occupied 38% of high-school students' and 40% of elementary students' time; HR were generally lower in sleep than in slow waking activity. High school students' mean VR estimates were 13 L/min for slow breathing, 18 for medium, and 23 for fast; elementary students' were 14 slow, 18 medium, and 19 fast. VR distributions were approximately lognormal. Maximum estimated VR were approximately 70 L/min in elementary and approximately 100 L/min in high school students. Compared to adults studied similarly, students reported more medium or fast breathing, and had equal or higher VR estimates during slow and medium breathing despite their smaller size. These results suggest that, relative to body size, young people inhale larger doses of outdoor air pollutants than adults.

Abstract  Several authors have considered the importance of exposure timing and how this affects the outcomes observed, but no one has systematically compiled preconceptional, prenatal, and postnatal developmental exposures and subsequent outcomes. Efforts were undertaken to examine the information available and to evaluate implications for risk assessment for several areas: a) respiratory and immune systems, b) reproductive system, c) nervous system, d) cardiovascular system, endocrine system, and general growth, and e) cancer. Major conclusions from a workshop on "Critical Windows of Exposure for Children's Health" included a) broad windows of sensitivity can be identified for many systems but detailed information is limited; b) cross-species comparisons of dose to target tissue and better data on the exposure-dose-outcome continuum are needed; c) increased interaction among scientific disciplines can further understanding by using laboratory animal results in designing epidemiological studies and human data to suggest specific laboratory studies on mechanisms and agent-target interactions; and d) thus far, only limited attention has been given to peripubertal/adolescent exposures, adult consequences of developmental exposures, and genome-environment interactions. More specific information on developmental windows will improve risk assessment by identifying the most sensitive window(s) for evaluation of dose-response relationships and exposure, evaluation of biological plausibility of research findings in humans, and comparison of data across species. In public health and risk management, information on critical windows may help identify especially susceptible subgroups for specific interventions. Key words: children's health, developmental disorders, developmental toxicity, environmental health, risk assessment, teratogen, windows of vulnerability.

Abstract  This paper presents an approach for characterizing the probability of adverse effects occurring in a population exposed to dose rates in excess of the Reference Dose (RfD). The approach uses a linear threshold (hockey stick) model of response and is based on the current system of uncertainty factors used in setting RfDs. The approach requires generally available toxicological estimates such as No-Observed-Adverse-Effect Levels (NOAELs) or Benchmark Doses and doses at which adverse effects are observed in 50% of the test animals (ED50s). In this approach, Monte Carlo analysis is used to characterize the uncertainty in the dose response slope based on the range and magnitude of the key sources of uncertainty in setting protective doses. The method does not require information on the shape of the dose response curve for specific chemicals, but is amenable to the inclusion of such data. The approach is applied to four compounds to produce estimates of response rates for dose rates greater than the RfD.

Abstract  In recent years, many cases of soil pollution have been unearthed in the Netherlands. The ingestion of soil particles due to mouthing behaviour of young children is an important potential pathway of exposure and may constitute a health risk. For an assessment of these health risks, a reliable estimation of the daily inadvertent ingestion of soil particles is necessary. A method to estimate soil ingestion is the use of titanium (Ti), aluminium (Al) and acid insoluble residue (AIR) content of the soil as a tracer. By measuring these tracers in faeces of children and in soil, an estimate can be made of the amount of soil ingested. This method can be used if the following conditions are met: tracer intake by other routes (food) is low and not too variable; tracer absorption from soil in the gastro-intestinal (GI) tract is negligible; tracer concentrations in soil are high and not too variable. A small pilot study was conducted among 18 children visiting a nursery school and 6 hospitalized children without any possibility of soil contact. The results of the pilot study indicate that each tracer is present in faeces in highly variable amounts, but that a combination of these three tracers produces a useful picture of potential soil ingestion. Quantitatively, a difference between the two populations of 55 mg/d, expressed as soil ingestion, was found. Despite the small numbers involved, this difference was statistically significant as the population standard deviations were small. In a number of different soil types, tracer concentrations were found to be almost equal. Further studies are planned to test the validity of the assumptions, and to investigate larger child populations living in different circumstances.

Abstract  The Safe Drinking Water Act of 1974 (PL93-523) required the Administrator of the Environmental Protection Agency to arragne for a study that would serve as a scientific basis for revising the primary drinking water regulations that were promulgated under the Act. The Study was conducted by the Safe Drinking Water Committee of the National Research Council. A thorough study of the scientific literature was undertaken in order to assess the implications for human health of the constituents of drinking water in the United States. Assessment of the health benefits and the economic or technological feasibility of achieving a given level of contaminant control is outside the scope of the study, although the beneficial effects of some constituents of drinking water were considered. The risk to man of contaminants ingested in drinking water was evaluated on the basis of both epidemiological studies and studies of toxicity in laboratory animals.

Abstract  Residents of a western Pennsylvania community have been using a public groundwater supply known to be contaminated with trichloroethylene (TCE) at concentrations as high as 260 micro-g/L. Volatilization studies were conducted in several homes in this community to assess inhalation exposures received while showering. A newly developed indoor air quality model, MAVRIQ, was used to apply our volatilization models to these measurements. Calibration of MAVRIQ showed that air-exchange rates between the shower stalls and bathrooms are higher than often assumed. Consistent with predictions from our laboratory studies, the inhalation exposures from a six-minute shower in these homes were estimated to be about twice that from direct ingestion of one-liter of contaminated water.

Abstract  The public depends on competent risk assessment from the federal government and the scientific community to grapple with the threat of pollution. When risk reports turn out to be overblown--or when risks are overlooked--public skepticism abounds. This comprehensive and readable book explores how the U.S. Environmental Protection Agency (EPA) can improve its risk assessment practices, with a focus on implementation of the 1990 Clean Air Act Amendments. With a wealth of detailed information, pertinent examples, and revealing analysis, the volume explores the "default option" and other basic concepts. It offers two views of EPA operations: The first examines how EPA currently assesses exposure to hazardous air pollutants, evaluates the toxicity of a substance, and characterizes the risk to the public. The second, more holistic, view explores how EPA can improve in several critical areas of risk assessment by focusing on cross-cutting themes and incorporating more scientific judgment. This comprehensive volume will be important to the EPA and other agencies, risk managers, environmental advocates, scientists, faculty, students, and concerned individuals.

Abstract  RAGS Part A is one of a three-part series: Part B addresses the development of risk-based preliminary remediation goals; and Part C addresses human health risk evaluations of remedial alternatives. RAGS Part A: Human Health Evaluation Manual provides guidance on the human health evaluation activities that are conducted during the baseline risk assessment - the first step of the Remedial Investigation/Feasibilty Study (RI/FS). The baseline risk assessment is an analysis of the potential adverse health effects (current or future) caused by hazardous substance releases from a site in the absence of any actions to control or mitigate these releases (i.e., under an assumption of no action). The baseline risk assessment contributes to the site characterization and subsequent development, evaluation, and selection of appropriate response alternatives. The results of the baseline risk assessment are used to help determine whether additional response action is necessary at the site, modify preliminary remediation goals, help support selection of the "no- action" remedial alternative, where appropriate, and document the magnitude of risk at a site, and the primary causes of that risk. Baseline risk assessments are site-specific and therefore may vary in both detail and the extent to which qualitative and quantitative analyses are used, depending on the complexity and particular circumstances of the site, as well as the availability of applicable or relevant and appropriate requirements (ARARs) and other criteria, advisories, and guidance. After an initial planning stage, there are four steps in the baseline risk assessment process: data collection and analysis; exposure assessment; toxicity assessment; and risk characterization. The potential users of Part A are the individuals actually conducting health risk assessments for sites, who frequently are contractors to the EPA, other federal agencies, states, or potentientially responsible parties. It is also targeted to EPA staff, including those responsible for review and oversight of risk assessments (e.g. technical staff in the regions) and those responsible for ensuring adequate evaluations of human health risks (i.e., RPMs).

Abstract  The objective of this study was to test the effectiveness of individual commercially available portable indoor air cleaning units in removing dust particulates, tobacco smoke particulate and vapor phase constituents (nicotine and vinylpyridine), viable and total fungal spores, pollen, and gaseous contaminants (carbon monoxide[CO], nitrogen dioxide [NO2], and formaldehyde [HCHO]), in a clean air test chamber. The air cleaner chamber results presented here represent initial-use results. In general, High Efficiency Particulate Air (HEPA) and electrostatic precipitator systems demonstrated the highest efficiencies with respect to particulate contaminants, followed closely by electret filter systems. Ionizers and ozone generators were least effective in particulate removal. Systems which included sufficient sorbent material (i.e. activated carbon or potassium permanganate) were marginally effective at gaseous contaminant removal. None of the systems tested were effective at carbon monoxide removal. Sensory testing was conducted to discern potential correlation between human perceptive response and measured air cleaner performance (with respect to tobacco smoke removal). An electret filter (EF) loaded with carbon sorbent received the best ratings with respect to odor strength, nasal irritation, eye irritation, and overall air acceptability

Abstract  The filtration efficiency of ventilation air cleaners is highly particle-size dependent over the 0.01 to 3 mu m diameter size range. Current standardized test methods, which determine only overall efficiencies for ambient aerosol or other test aerosols, provide data of limited utility. Because particles in this range are respirable and can remain airborne for prolonged time periods, measurement of air cleaner fractional efficiency is required for application to indoor air quality issues. The objectives of this work have been to 1) develop a test apparatus and procedure to quantify the the fractional filtration efficiency of air cleaners over the 0.01 to 3 mu m diameter size range and 2) quantify the fractional efficiency of several induct air cleaners typical of those used in residential and office ventilation systems. Results show that efficiency is highly dependent on particle size, flow rate, and dust load present on the air cleaner. A minimum in efficiency was often observed in the 0.1 to 0.5 mu m diameter size range. The presence of a dust load frequently increased an air cleaner's efficiency; however, some air cleaners showed little change or a decrease in efficiency with dust loading. The common furnace filter had fractional efficiency values of less than 10% over much of the measurement size range.

Abstract  Currently, there is a trend away from the use of single (often conservative) estimates of risk to summarize the results of risk analyses in favor of stochastic methods which provide a more complete characterization of risk. The use of such stochastic methods leads to a distribution of possible values of risk, taking into account both uncertainty and variability in all of the factors affecting risk. In this article, we propose a general framework for the analysis of uncertainty and variability for use in the commonly encountered case of multireplicative risk models, in which risk may be expressed as a product of two or more risk factors. Our analytical methods facilitate the evaluation of overall uncertainty and variability in risk assessment, as well as the contributions of individual risk factors to both uncertainty and variability which is cumbersome using Monte Carlo methods. The use of these methods is illustrated in the analysis of potential cancer risks due to the ingestion of radon in drinking water.

Abstract  Using distributions of time spent at various ventilation levels, ranges of inhalation exposure in the population can be established. Distributions of exposure time were determined using results of a study by the California Air Resources Board (CARB) which focused on time spent by humans participating in various activities and the locations where the activities occurred. The daily at-home activities from the CARB study were assigned to one of three ventilation levels, generating aggregate time periods. Distinct age and gender populations were identified, and distributions for aggregate time were established for these populations at each of the ventilation levels. In addition to aggregate time spent at home, distributions for various ages and genders were established for aggregate time spent at school and work. By combining distributions of aggregate time with corresponding ventilation rates, the distribution of inhalation rates can be established for at home, at work, and at school exposures.

Abstract  Eleven portable air cleaning devices have been evaluated for control of indoor concentrations of respirable particles and radon progeny. Following injection of cigarette smoke and radon in a room-size chamber, decay rates for particles and radon progeny concentrations were measured with and without air cleaner operation. Particle concentrations were obtained for total number concentration and for number concentration by particle size. In tests with no air cleaner the natural decay rate for cigarette smoke was observed to be 0.2 hr/sup -1/. Air cleaning rates for particles were found to be negligible for several small panel-filters, a residential ion-generator, and a pair of mixing fans. The electrostatic precipitators and extended surface filters tested had significant particle removal rates, and a HEPA-type filter was the most efficient air cleaner. The evaluation of radon progeny control produced similar results; the air cleaners which were effective in removing particles were also effective in removing radon progeny. At low particle concentrations plateout of the unattached radon progeny is an important removal mechanism. Based on data from these tests, the plateout rate for unattached progeny was found to be 15 hr/sup -1/. The unattached fraction and the overall removal rate due to deposition of attached and unattached nuclides have been estimated for each radon decay product as a function of particle concentration. While air cleaning can be effective in reducing total radon progeny, concentrations of unattached radon progeny can increase with increasing air cleaning.

Abstract  A study was conducted to determine concentrations of polychlorinated biphenyls (PCBs) in local fish and to establish patterns of fish consumption of nursing Mohawk women residing near three industrial hazardous waste sites. From 1986 to 1992, 97 Mohawk women were interviewed within one month postpartum. A comparison group consisted of 154 nursing Caucasians. Samples of 348 local fish were analyzed for PCBs. The results indicated that fish in the Mohawk area, especially those collected offshore from the waste sites, had been contaminated with PCBs. The dietary data showed a greater past prevalence of local fish consumption among Mohawk mothers, with an overall annual mean of 23.5 local fish meals more than one year before the pregnancy compared with 14.1 for the control women (p < 0.001). The prevalence of consumption by the Mohawks, however, declined over time, resulting in overall mean rates of 9.2 local fish meals one year or less before pregnancy, and 3.9 meals per year during pregnancy (p < 0.001 for linear trend). Compared to the Mohawks, significantly fewer control women stopped eating local fish, and their rates declined less sharply. A secular trend was also observed in the overall rate of consumption during pregnancy for the Mohawks, with those who gave birth in 1986-1989 having a mean of 10.7 local fish meals per year during pregnancy, compared with means of 3.6 and 0.9 respectively for women who delivered in 1990 and 1991-1992 (p < 0.05 for linear trend). No such trend was apparent for the controls. No background variable was significantly related to the rate of local fish consumption among the Mohawks, but a decrease over time in the rate of local fish consumption was greater among those Mohawks who ate the most local fish initially (r = -0.76, p < 0.001), or who also reduced their alcohol intake during pregnancy (r = 0.35, p < 0.05). Mohawks were also more likely than the controls to trim the fat, remove the skin from, and fry and fish they ate during the past year. These dietary changes may be the result of advisories that have been issued over the past decade recommending against the consumption of local fish by pregnant and nursing Mohawk women. Such changes, if sustained, should reduce their exposure to PCBs and correspondingly the potential for adverse health effects.

Abstract  Anthropometry plays an important role in human factors considerations for safe product design, particularly for the 31% of the U.S. population under age 19. This paper discusses two nationwide studies conducted for Consumer Product Safety Commission to obtain center of gravity, linkage, shape and functional body measurement data on 8154 infants, children, and teenagers representative of the U.S. population, for consumer product design, hazard assessment and guidance in establishing requirements or recommendations in standards.