Collection efficiencies of an electrostatic sampler with superhydrophobic surface for fungal bioaerosols.

UNLABELLED: We recently developed an electrostatic precipitator with superhydrophobic surface (EPSS), which collects particles into a 10- to 40-µl water droplet allowing achievement of very high concentration rates (defined as the ratio of particle concentration in the collection liquid vs. the airborne particle concentration per time unit) when sampling airborne bacteria. Here, we analyzed the performance of this sampler when collecting three commonly found fungal spores--Cladosporium cladosporioides, Penicillium melinii, and Aspergillus versicolor--under different operating conditions. We also adapted adenosine triphosphate (ATP)-based bioluminescence for the analysis of collection efficiency and the concentration rates. The collection efficiency ranged from 10 to 36% at a sampling flow rate of 10 l/min when the airborne fungal spore concentration was approximately 10(5)-10(6) spores/m(3) resulting in concentration rates in the range of 1 × 10(5)-3 × 10(5)/min for a 10-µl droplet. The collection efficiency was inversely proportional to the airborne spore concentration and it increased to above 60% for common ambient spore concentrations, e.g., 10(4)-10(5) spores/m(3). The spore concentrations determined by the ATP-based method were not statistically different from those determined by microscopy and allowed us to analyze spore concentrations that were too low to be reliably detected by microscopy. PRACTICAL IMPLICATIONS: The new electrostatic precipitator with superhydrophobic surface (EPSS) collects airborne fungal spores into small water droplets (10 and 40 µl) allowing achievement of concentration rates that are higher than those of most currently available bioaerosol samplers. Biosamplers with high concentration rates enable detection of low ambient aerial bioaerosol concentrations in various environments, including indoors air, and would be useful for improved exposure assessment. A successful adaptation of the adenosine triphosphate (ATP)-based bioluminescence assay for the quantification of fungal spores from a specific species enables fast sample analysis in laboratory investigations. This rapid assay could be especially useful when investigating the performance of biological samplers as a function of multiple operational parameters.

Environmental, dietary, demographic, and activity variables associated with biomarkers of exposure for benzene and lead.

Classification and regression tree methods represent a potentially powerful means of identifying patterns in exposure data that may otherwise be overlooked. Here, regression tree models are developed to identify associations between blood concentrations of benzene and lead and over 300 variables of disparate type (numerical and categorical), often with observations that are missing or below the quantitation limit. Benzene and lead are selected from among all the environmental agents measured in the NHEXAS Region V study because they are ubiquitous, and they serve as paradigms for volatile organic compounds (VOCs) and heavy metals, two classes of environmental agents that have very different properties. Two sets of regression models were developed. In the first set, only environmental and dietary measurements were employed as predictor variables, while in the second set these were supplemented with demographic and time-activity data. In both sets of regression models, the predictor variables were regressed on the blood concentrations of the environmental agents. Jack-knife cross-validation was employed to detect overfitting of the models to the data. Blood concentrations of benzene were found to be associated with: (a) indoor air concentrations of benzene; (b) the duration of time spent indoors with someone who was smoking; and (c) the number of cigarettes smoked by the subject. All these associations suggest that tobacco smoke is a major source of exposure to benzene. Blood concentrations of lead were found to be associated with: (a) house dust concentrations of lead; (b) the duration of time spent working in a closed workshop; and (c) the year in which the subject moved into the residence. An unexpected finding was that the regression trees identified time-activity data as better predictors of the blood concentrations than the measurements in environmental and dietary media.

Measurement of children's exposure to pesticides: analysis of urinary metabolite levels in a probability-based sample.

The Minnesota Children's Pesticide Exposure Study is a probability-based sample of 102 children 3-13 years old who were monitored for commonly used pesticides. During the summer of 1997, first-morning-void urine samples (1-3 per child) were obtained for 88% of study children and analyzed for metabolites of insecticides and herbicides: carbamates and related compounds (1-NAP), atrazine (AM), malathion (MDA), and chlorpyrifos and related compounds (TCPy). TCPy was present in 93% of the samples, whereas 1-NAP, MDA, and AM were detected in 45%, 37%, and 2% of samples, respectively. Measured intrachild means ranged from 1.4 microg/L for MDA to 9.2 microg/L for TCPy, and there was considerable intrachild variability. For children providing three urine samples, geometric mean TCPy levels were greater than the detection limit in 98% of the samples, and nearly half the children had geometric mean 1-NAP and MDA levels greater than the detection limit. Interchild variability was significantly greater than intrachild variability for 1-NAP (p = 0.0037) and TCPy (p < 0.0001). The four metabolites measured were not correlated within urine samples, and children's metabolite levels did not vary systematically by sex, age, race, household income, or putative household pesticide use. On a log scale, mean TCPy levels were significantly higher in urban than in nonurban children (7.2 vs. 4.7 microg/L; p = 0.036). Weighted population mean concentrations were 3.9 [standard error (SE) = 0.7; 95% confidence interval (CI), 2.5, 5.3] microg/L for 1-NAP, 1.7 (SE = 0.3; 95% CI, 1.1, 2.3) microg/L for MDA, and 9.6 (SE = 0.9; 95% CI, 7.8, 11) microg/L for TCPy. The weighted population results estimate the overall mean and variability of metabolite levels for more than 84,000 children in the census tracts sampled. Levels of 1-NAP were lower than reported adult reference range concentrations, whereas TCPy concentrations were substantially higher. Concentrations of MDA were detected more frequently and found at higher levels in children than in a recent nonprobability-based sample of adults. Overall, Minnesota children's TCPy and MDA levels were higher than in recent population-based studies of adults in the United States, but the relative magnitude of intraindividual variability was similar for adults and children.

Effect of vehicle use and maintenance patterns of a self-described group of sensitive individuals and nonsensitive individuals to methyl tertiary-butyl ether in gasoline.

The objective of this study was to compare the driving habits and vehicle maintenance patterns of individuals who report symptoms when exposed to methyl tertiary-butyl ether (MTBE) and those who are asymptomatic when exposed to the oxygenate. Participants were healthy volunteers (CON) and self-reported MTBE-sensitive individuals (SRS) who participated in a controlled exposure study of MTBE in gasoline. A questionnaire was developed to gather information about each participant's automobile usage, engine maintenance habits and fueling and driving patterns. Results showed that the individuals who had self-reported heightened sensitivity to the oxygenate drove their vehicles more often and fueled their vehicles more frequently than asymptomatic individuals. In addition, the self-reported symptomatic individuals in this study were shown to be more likely to drive vehicles with some form of body damage and carbureted engines.

Controlled human exposure to methyl tertiary butyl ether in gasoline: symptoms, psychophysiologic and neurobehavioral responses of self-reported sensitive persons.

The 1990 Clean Air Act mandated oxygenation of gasoline in regions where carbon monoxide standards were not met. To achieve this standard, methyl tertiary butyl ether (MTBE) was increased to 15% by volume during winter months in many locations. Subsequent to the increase of MTBE in gasoline, commuters reported increases in symptoms such as headache, nausea, and eye, nose, and throat irritation. The present study compared 12 individuals selected based on self-report of symptoms (self-reported sensitives; SRSs) associated with MTBE to 19 controls without self-reported sensitivities. In a double-blind, repeated measures, controlled exposure, subjects were exposed for 15 min to clean air, gasoline, gasoline with 11% MTBE, and gasoline with 15% MTBE. Symptoms, odor ratings, neurobehavioral performance on a task of driving simulation, and psychophysiologic responses (heart and respiration rate, end-tidal CO(2), finger pulse volume, electromyograph, finger temperature) were measured before, during, and immediately after exposure. Relative to controls, SRSs reported significantly more total symptoms when exposed to gasoline with 15% MTBE than when exposed to gasoline with 11% MTBE or to clean air. However, these differences in symptoms were not accompanied by significant differences in neurobehavioral performance or psychophysiologic responses. No significant differences in symptoms or neurobehavioral or psychophysiologic responses were observed when exposure to gasoline with 11% MTBE was compared to clean air or to gasoline. Thus, the present study, although showing increased total symptoms among SRSs when exposed to gasoline with 15% MTBE, did not support a dose-response relationship for MTBE exposure nor the symptom specificity associated with MTBE in epidemiologic studies.

Effects of air pollution on children's respiratory health in three Chinese cities.

During the winter of 1988-1989, parents of 2,789 elementary-school students completed standardized questionnaires. The students were 5-14 y of age and were from three urban districts and one suburban district of three large Chinese cities. The 4-y average ambient levels of total suspended particles in the three cities differed greatly during the period 1985-1988: Lanzhou, 1,067 microg/m3; urban Wuhan, 406 microg/m3; Guangzhou, 296 microg/m3; and suburban Wuhan, 191 microg/m3. The authors constructed unconditional logistic-regression models to calculate odds ratios and 95% confidence intervals for prevalences of several respiratory symptoms and illnesses, adjusted for district, use of coal in the home, and parental smoking status. There was a positive and significant association between total suspended particle levels and the adjusted odds ratios for cough, phlegm, hospitalization for diseases, and pneumonia. This association was derived from only the 1,784 urban children and, therefore, the authors were unable to extrapolate it to the suburban children. The results also indicated that parental smoking status was associated with cough and phlegm, and use of coal in the home was associated only with cough prevalence (alpha = 0.05).

Responses to the region 5 NHEXAS time/activity diary. National Human Exposure Assessment Survey.

The time/activity diary developed for use in the National Human Exposure Assessment Survey (NHEXAS) was completed by 249 participants in the Research Triangle Institute/Environmental and Occupational Health Sciences Institute (RTI/EOHSI) NHEXAS population-based pilot project conducted in the upper Midwest (EPA Region 5). The majority of participants successfully completed the diary during the 6-day study period. Participant responses showed internal consistency between related questions within the diary and between instruments used within the study. Comparison of response rates with the National Human Activity Pattern Survey, a nationwide population-based study, found consistent results when the same questions were used in both studies. Several questions identified age-specific activities. The value of the 6-day diary over 1-day surveys was apparent in discriminating between episodic and regularly conducted activities and in identifying subpopulations whose behavior may contribute to exposure to environmental pollutants.

The EL sampler: a press sampler for the quantitative estimation of dermal exposure to pesticides in housedust.

Indirect sampling techniques to estimate dermal exposure to pesticides on housedust-laden indoor surfaces should demonstrate collection efficiencies, for both particles and pesticide residues, which are similar to those that would adhere to the human skin. A spring-loaded press sampler has been developed that approximated the particle- and pesticide-collection efficiencies of a hand press of a human participant. Particle-collection efficiencies for the hand press and EL sampler, using housedust sieved to <250 microm in diameter, indicated that both sampling techniques collected similar particle fractions over the range of particle sizes. Pesticide-collection efficiencies measured on the participants hand (seven paired tests) were 42+/-7% atrazine, 29+/-8% diazinon, 43+/-8% malathion and 21+/-5% chlorpyrifos. The EL sampler collected 35+/-5%, 31+/-3%, 32+/-5% and 18+/-3% respectively. The collection efficiencies of the two sampling techniques were highly correlated for atrazine, diazinon, and chlorpyrifos (correlation coefficient=0.840, 0.815, and 0.706), but not for malathion (correlation coefficient=0.086).

Assessing exposures to inhaled complex mixtures.

In the course of daily activities, individuals spend varying amounts of time in different spaces where they are exposed to a complex mixture of gas, vapor, and particulate contaminants. The term complex is used in this paper to refer to binary mixtures as well as truly complex mixtures of three or more constituents. The diversity of the environments where pollution may occur, the number of pollutants that may be present, and the nature of the activity in the environment combine to pose a challenge to investigators of the health effects of air pollutants. This article discusses several methods of measuring or assessing exposure to complex mixture air contaminants that include time-activity assessments, personal monitoring, biomarkers of exposure, and microenvironmental models that can be employed singly or in combination in a protocol for exposure assessment. The use of nested designs, involving more intensive data collection from samples or subjects, is also considered.

Assessment of carcinogenic risk from personal exposure to benzo(a)pyrene in the Total Human Environmental Exposure Study (THEES).

The Total Human Environmental Exposure Study (THEES) was an investigation of multimedia exposure to the ubiquitous environmental carcinogen, benzo(a)pyrene (BaP). The three-phase study was conducted in Phillipsburg, New Jersey and involved the participation of 14-15 individuals (8-10 homes) during each 14-day monitoring period. Microenvironmental sampling of air, food, water and soil indicated that environmental exposure to BaP was primarily through air and food. Exposure and risk estimates were, therefore, based on the results of personal monitoring of breathing zone air and prepared food samples. Based on a comparison of the range and magnitude of inhalation and dietary BaP exposures, food ingestion was clearly the predominant exposure to pathway. The relative contributions of other potential sources of community exposure to BaP (e.g., soil and drinking water ingestion) were also assessed. The excess cancer risk estimates for food ingestion were consistently greater than those for personal air, reflecting both the predominantly higher BaP exposures through the diet and the higher carcinogenic potency value for oral exposure. Overall, the total lifetime risk from personal exposure to BaP for nonsmokers in the community was estimated at 10(-5). In identifying risk reduction options, it is important to account for the observation that personal activities, lifestyle, and diet strongly influenced individual exposures to BaP.

Epidemiologic investigation of a cancer cluster in professional football players.

In 1976, the New York Giants professional football team relocated to the newly constructed Meadowlands Sports Complex (MSC) in East Rutherford, NJ. Between 1980 and 1987 four team members developed cancer: one case each of non-Hodgkin's lymphoma, glioblastoma, angiosarcoma, and Hodgkin's disease. Because the surrounding area contains three superfund sites, concern was widespread that the cancers were related to environmental contamination. To assess for a possible environmental etiology, we conducted clinical, environmental, and epidemiologic studies at the MSC. Measurements of volatile organic compounds were all below occupational exposure limits and were similar to ambient levels in nearby Lyndhurst, NJ. Outdoor AM radio broadcast field strengths were in the uppermost 0.1% of field strengths measured in urban areas of the United States. Proportionate mortality ratio and proportional cancer incidence ratio studies of the MSC workforce found no excesses of cancer deaths or of incident cancer cases either for all sites combined or for any specific site. No significant differences in cancer incidence or mortality were found between indoor and nonindoor workers. Based on examination of all available data, the four cancer cases were judged most likely to have been clustered by chance and not to have been caused by environmental conditions at the MSC.

Analysis of human exposure to benzo(a)pyrene via inhalation and food ingestion in the Total Human Environmental Exposure Study (THEES).

The Total Human Environmental Exposure Study (THEES) focuses on benzo(a)pyrene (BaP) as an example of a combustion-generated polycyclic aromatic hydrocarbon (PAH) compound. Primary pathways for environmental exposures to BaP are inhalation and ingestion. This program of field studies was conducted in Phillipsburg, New Jersey, a small, industrial city in the Delaware River valley. The study protocols included direct monitoring of BaP exposures via inhalation and ingestion pathways during three separate periods, each lasting 14 days. BaP concentrations in air were sampled at outdoor and in-home locations, with personal air sampling added during the latter two phases. Cooked food samples from each household were acquired, using a constant portion "second plate" of each meal prepared at home. Ambient levels were 4-10 times higher during the cold months compared with the late summer study period. Space heating and regional aerosol were major contributors to community levels of BaP in the air during the wintertime. Penetration of outdoor air, cooking activities, combustion appliances, and cigarette smoke were important sources of indoor air exposures. Cooking activities, besides releasing BaP-enriched particles indoors, produced food imbued with BaP and added substantially to exposure via the ingestion route. Among the study subjects, the range and magnitude of dietary exposures (2 to 500 ng/d) were much greater than for inhalation (10 to 50 ng/d). Nevertheless, there were ample individual cases where inhalation of BaP was the predominant exposure route. Indoor air BaP levels were closely correlated with ambient levels in most of the homes. For some individuals, measured personal air BaP exposures were adequately predicted by time-weighting of microenvironmental (i.e., outdoor and in-home) concentrations. However, enormously high exposures for ingestion or inhalation were detected only by direct observation, not from microenvironmental data.

Factors associated with human exposures to polycyclic aromatic hydrocarbons.

The number and quantities of PAH emitted and accumulated within various environmental media require the development and application of new methods for determining the major routes of exposure to individual and selected compounds. From research that has been conducted on airborne BaP and other selected PAH it appears that they can accumulate indoors as well as outdoors. Smoking seems to be a major contributor for direct and passive inhalation, but the role of cooking and wood burning related to indoor emissions needs to be investigated further. The available data indicate that many PAH will be distributed between both particles and the gas phase. Therefore, new techniques for simultaneously sampling PAH in both phases are required for the indoor environment and personal monitoring studies. These will increase our understanding of the distribution of each component and increase the accuracy of exposure and risk assessments conducted for Total PAH. A strategy (THEES) has been developed for the measurement of BaP exposure from multiple pathways. It should be extended to other PAH, which will assist in quantifying the significance of indoor air related exposures. The inhalation exposures could be derived from indoor combustion sources, penetration of outdoor air indoors, and personal activities, such as cooking and smoking. The reactivity of PAH requires further investigation, since it appears that a number of nitro-PAH will be produced. Some of the resulting compounds will need to be factored into PAH exposure assessments.

Exposure analysis and assessment for low-risk cancer agents.

The analysis of exposure is a necessary feature of epidemiological studies. In the case of low-risk cancer agents, the examination of potential exposure should follow a sequence that prioritizes the major media and routes of concern. This will minimize the misclassification of exposure and the failure to identify important co-factors, e.g. contamination in other media, etc. The manuscript describes specific components of exposure analysis and provides examples that pertain to single and multimedia exposure problems. The approach is examined by using the Total Human Environmental Exposure Study (THEES) for benzo(a)pyrene as a potential model for low-risk cancer agents. Since benzo(a)pyrene can be found in air, water, soil and food, and has a number of sources, THEES illustrates how to prioritize an exposure assessment, take advantage of opportunities to conduct micro-environmental measurements, and collect personal monitoring and biological marker samples. A daily activity log is briefly described.

Critical issues in air pollution epidemiology.

The epidemiological studies which have had significant impact on the setting of National Ambient Air Quality Standards (NAAQSs) were performed more than twenty years ago. Most of the more recent studies have been seriously flawed in their design and/or execution because they neglected to account for important variables such as: pollutant exposures other than those from ambient air; the influence of personal activity on pollutant uptake; host responsiveness; and the separate contributions of recent transient peak exposures and long-term chronic exposures on the effects endpoints. For particulate pollutants, the influence of composition and size distribution has also received too little consideration. In order to address these deficiencies, research and methods development are needed on: indices for particulate exposures; identification of exposures relevant to the effects; improved indices of effects; acquisition of response data; identification of exposed populations; and identification of susceptible subgroups. Approaches to these needs are discussed, along with brief reviews of several recent studies that have focused on critical issues of concern, made the necessary efforts to characterize the relevant exposures of the populations being studied, and demonstrated human responses to ambient pollutants at current exposure levels.