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PubMed2005

Gravimetric and chemical features of airborne PM 10 AND PM 2.5 in mainland Portugal.

This paper describes concentration amounts of arsenic (As), particulate mercury (Hg), nickel (Ni) and lead (Pb) in PM(10) and PM(2.5), collected since 1993 by the Technological and Nuclear Institute (ITN) at different locations in mainland Portugal, featuring urban, industrial and rural environments, and a control as well. Most results were obtained in the vicinity of coal- and oil-fired power plants. Airborne mass concentrations were determined by gravimetry. As and Hg concentrations were obtained through instrumental neutron activation analysis (INAA), and Ni and Pb concentrations through proton-induced X-ray emission (PIXE). Comparison with the EU (European Union) and the US EPA (United States Environmental Protection Agency) directives for Ambient Air has been carried out, even though the sampling protocols herein--set within the framework of ITN's R&D projects and/or monitoring contracts--were not consistent with the former regulations. Taking this into account, 1) the EU daily limit for PM(10) was exceeded a few times in all sites except the control, even if the number of times was still inferior to the allowed one; 2) the EU annual mean for PM(10) was exceeded at one site; 3) the EPA daily limit for PM(2.5) was exceeded one time at three sites; 4) the EPA annual mean for PM(2.5) was exceeded at most sites; 5) the inner-Lisbon site approached or exceeded the legislated PMs; 6) Pb levels stayed far below the EU limit value; and 7) concentrations of As, Ni and Hg were also far less than the reference values adopted by EU. In every location, Ni appeared more concentrated in PM(2.5) than in coarser particles, and its levels were not that different from site to site, excluding the control. The highest As and Hg concentrations were found in the neighbourhood of the coal-fired, utility power plants. The results may be viewed as a "worst-case scenario" of atmospheric pollution, since they have been obtained in busy urban-industrial areas and/or near major power-generation and waste-incineration facilities.

Air Pollutants↗
PubMed2004

A Bayesian hierarchical approach for relating PM(2.5) exposure to cardiovascular mortality in North Carolina.

Considerable attention has been given to the relationship between levels of fine particulate matter (particulate matter < or = 2.5 microm in aerodynamic diameter; PM(2.5) in the atmosphere and health effects in human populations. Since the U.S. Environmental Protection Agency began widespread monitoring of PM(2.5) levels in 1999, the epidemiologic community has performed numerous observational studies modeling mortality and morbidity responses to PM(2.5) levels using Poisson generalized additive models (GAMs). Although these models are useful for relating ambient PM(2.5) levels to mortality, they cannot directly measure the strength of the effect of exposure to PM(2.5) on mortality. In order to assess this effect, we propose a three-stage Bayesian hierarchical model as an alternative to the classical Poisson GAM. Fitting our model to data collected in seven North Carolina counties from 1999 through 2001, we found that an increase in PM(2.5) exposure is linked to increased risk of cardiovascular mortality in the same day and next 2 days. Specifically, a 10- microg/m3 increase in average PM(2.5) exposure is associated with a 2.5% increase in the relative risk of current-day cardiovascular mortality, a 4.0% increase in the relative risk of cardiovascular mortality the next day, and an 11.4% increase in the relative risk of cardiovascular mortality 2 days later. Because of the small sample size of our study, only the third effect was found to have > 95% posterior probability of being > 0. In addition, we compared the results obtained from our model to those obtained by applying frequentist (or classical, repeated sampling-based) and Bayesian versions of the classical Poisson GAM to our study population.

Adolescent↗
PubMedDate not supplied

Biodegradation of methyl tert-butyl ether and BTEX at varying hydraulic retention times.

The feasibility of biologically degrading methyl tert-butyl ether (MTBE)-contaminated groundwater is dependent on the ability to degrade MTBE and its byproducts in the presence of other gasoline contaminants. This study investigates a mixed culture degrading both MTBE and benzene-toluene-ethylbenzene-xylene (BTEX) in a continuous-flow reactor with a biomass retention system (porous pot) at varying hydraulic retention times (HRTs). The reactor degraded both MTBE and BTEX simultaneously to less than the U.S. Environmental Protection Agency's drinking water standards and recommendations at an HRT of 3.76 days. Methyl tert-butyl ether was degraded from 75 mg/L to less than 1 microg/L and each BTEX compound was degraded from 17 mg/L to less than 1 microg/L. Effluent concentrations of MTBE and BTEX increased as the HRT was decreased from 3.76 to 0.52 days, but remained lower than drinking water limits. The highest MTBE effluent concentration was at 0.52 days and continued to average less than 10 microg/L. Although tert-butyl alcohol (TBA) is commonly sited as a degradation byproduct of MTBE, it remained lower than 1 microg/L throughout all reactor operation periods. The MTBE and BTEX observed yield coefficients for the reactor ranged from 0.11 to 0.16 mg biomass/mg MTBE and BTEX, with the rate increasing with increased HRT. Degradation rates from the reactor were compared to results from batch studies with the same culture on MTBE and TBA alone and in the presence of BTEX. Results of batch studies showed that BTEX was not required for this culture to degrade MTBE. The presence of BTEX only had an effect on the rate of MTBE degradation at the highest concentration, while BTEX significantly delayed the degradation of TBA at all concentrations. Batch studies also showed that the rate of degradation of TBA was higher with and without BTEX than the rate of degradation of MTBE, explaining the lack of high levels of TBA in the reactor.

Benzene↗
PubMed2001

Derivation of ambient water quality criteria for formaldehyde.

This paper describes the derivation of aquatic life water quality criteria for formaldehyde, developed in accordance with United States Environmental Protection Agency's (USEPA's) Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses. The initial step in deriving water quality criteria was to conduct an extensive literature search to assemble available acute and chronic toxicity data for formaldehyde. The literature search identified a large amount of information on acute toxicity of formaldehyde to fish and aquatic invertebrates. These acute data were evaluated with respect to data quality, and poor quality or uncertain data were excluded from the data base. The resulting data base met the USEPA requirements for criteria derivation by having data for at least one species in at least eight different taxonomic families. One shortcoming of the literature-derived data base, however, was that few studies involved analytical confirmation of nominal formaldehyde concentrations and reported toxicity endpoints. Also, there were relatively few data on chronic toxicity. The acute toxicity data set consisted of data for 12 species of fish, 3 species of amphibians, and 11 species of invertebrates. These data were sufficient, according to USEPA guidelines, to calculate a final acute value (FAV) of 9.15 mg/l, and an acute aquatic life water quality criterion (one-half the FAV) of 4.58 mg/l. A final acute-chronic ratio (ACR) was calculated using available chronic toxicity data and USEPA-recommended conservative default assumptions to account for missing data. Using the FAV and the final ACR (5.69), the final chronic aquatic life water quality criterion was determined to be 1.61 mg/l.

Amphibians↗
PubMed2004

Bound and unextractable pesticidal plant residues: chemical characterization and consumer exposure.

Plants are well known to incorporate pesticides into bound and unextractable residues that resist solubilization in common laboratory solvents and are therefore not accessible to standard residue analysis. A characterization of such residues has been proposed for incorporation rates above trigger values of 0.05 mg kg(-1) parent pesticide equivalents, or percentage values of 10% (United States Environmental Protection Agency, 1995) or 25% (Commission of the European Communities, 1997) of the total radioactive residue. These trigger values are often exceeded. The present review describes the current status of the chemical characterization and animal bioavailability of bound and unextractable residues that may be xenobiotic in nature or result from natural recycling of simple degradation products. The latter case represents a mechanism of detoxification. Bound residues have been shown to be covalent or non-covalent in nature. With regard to the plant matrix molecules involved, incorporation into proteins, lignins, pectins, hemicelluloses and cutins has been demonstrated, and four covalent linkage types are known. Animal feeding experiments have revealed cases of low as well as high bioavailability. Many of the studies are limited by experimental uncertainties and by results only being reported as relative percentage values rather than absolute exposure. A preliminary value of absolute exposure from bound and unextractable residues is derived here for the first time from eight case studies. The mean exposure (ca 1.5 mg kg(-1) pesticidal equivalents) exceeds some of the existing maximum residue levels (MRLs) of residual free pesticides that are typically in the range of 0.05-1 mg kg(-1). A mathematical framework for the correction of current maximum residue levels is presented for cases of highly bioavailable bound residues. As bound pesticidal residues in food plants could represent a source of significant consumer exposure, an experimental test scheme is proposed here. It consists of basic chemical characterization, model digestibility tests and, in exceptional cases, animal bioavailability and additional toxicological studies.

Animals↗
PubMed2005

Hospital indoor PM10/PM2.5 and associated trace elements in Guangzhou, China.

PM10 and PM2.5 samples were collected in the indoor environments of four hospitals and their adjacent outdoor environments in Guangzhou, China during the summertime. The concentrations of 18 target elements in particles were also quantified. The results showed that indoor PM2.5 levels with an average of 99 microg m(-3) were significantly higher than outdoor PM2.5 standard of 65 microg m(-3) recommended by USEPA [United States Environmental Protection Agency. Office of Air and Radiation, Office of Air Quality Planning and Standards, Fact Sheet. EPA's Revised Particulate Matter Standards, 17, July 1997] and PM2.5 constituted a large fraction of indoor respirable particles (PM10) by an average of 78% in four hospitals. High correlation between PM2.5 and PM10 (R(2) of 0.87 for indoors and 0.90 for outdoors) suggested that PM2.5 and PM10 came from similar particulate emission sources. The indoor particulate levels were correlated with the corresponding outdoors (R(2) of 0.78 for PM2.5 and 0.67 for PM10), demonstrating that outdoor infiltration could lead to direct transportation into indoors. In addition to outdoor infiltration, human activities and ventilation types could also influence indoor particulate levels in four hospitals. Total target elements accounted for 3.18-5.56% of PM2.5 and 4.38-9.20% of PM10 by mass, respectively. Na, Al, Ca, Fe, Mg, Mn and Ti were found in the coarse particles, while K, V, Cr, Ni, Cu, Zn, Cd, Sn, Pb, As and Se existed more in the fine particles. The average indoor concentrations of total elements were lower than those measured outdoors, suggesting that indoor elements originated mainly from outdoor emission sources. Enrichment factors (EF) for trace element were calculated to show that elements of anthropogenic origins (Zn, Pb, As, Se, V, Ni, Cu and Cd) were highly enriched with respect to crustal composition (Al, Fe, Ca, Ti and Mn). Factor analysis was used to identify possible pollution source-types, namely street dust, road traffic and combustion processes.

Air Pollutants↗
PubMed2006

Comparison of source apportionments of fine particulate matter at two San Jose speciation trends network sites.

In this study, the chemical composition of fine particulate matter samples collected at U.S. Environmental Protection Agency Speciation Trends Network sites in San Jose, CA, from February 2000 to February 2005 were analyzed. A San Jose site was initially established at 4th Street and then subsequently moved to Jackson Street in mid-2002. These sites are approximately 1 km apart. There were no known major changes in the nature of the sources in the area over this period. The study used positive matrix factorization model to extract the source profiles and their mass contributions and to compare the results for the congruence of the source apportionments between these two nearby sites. In the case of the 4th Street site, the average mass was apportioned to wood combustion (32.1 +/- 2.5%), secondary nitrate (22.3 +/- 2%), secondary sulfate (10.7 +/- 0.6%), fresh sea salt (7.7 +/- 0.9%), gasoline vehicles (7.3 +/- 0.5%), aged sea salt (6.8 +/- 0.4%), road dust (6.7 +/- 0.7%), diesel emissions (3.9 +/- 0.3%), and a Ni-related industrial source (2.5 +/- 0.4%). At the Jackson Street site, the average mass was apportioned to wood combustion (33.6 +/- 2.6%), secondary nitrate (20.3 +/- 1.9%), secondary sulfate (13.9 +/- 0.9%), aged sea salt (12.4 +/- 0.7%), gasoline vehicle (8.3 +/- 0.6%), fresh sea salt (5.3 +/- 0.5%), diesel emission (3.2 +/- 0.3%), road dust (1.9 +/- 0.1%), and Ni-related industrial source (1.3 +/- 0.1%). Conditional probability function analysis was used to help identify local sources. These results suggested that moving the sampling site a short distance had little effect on the nature of the resolved source types although some differences in their quantitative impacts were obtained in the positive matrix factorization analyses.

Air Pollutants↗
PubMedDate not supplied

Estimating the frequency of tap-water exposures to Mycobacterium avium complex in the U.S. population with advanced AIDS.

Mycobacterium avium complex (MAC) is a group of ubiquitous and opportunistic bacterial pathogens included on the U.S. Environmental Protection Agency Drinking Water Contaminant Candidate List. The risk of contracting a disseminated MAC infection is primarily limited to the immunocompromised, including those with advanced acquired immunodeficiency syndrome (AIDS). These infections likely result from exposures to MAC-contaminated tap water, food, or soil, although the epidemiologic evidence is insufficient to implicate a specific medium. The objective of this study was to assess tap water exposure to MAC in the U.S. population with advanced AIDS, defined here as having fewer than 100 CD4(+) cells/mm(3) of blood. Using limited data on the detection of MAC and self-reported post-tap treatment practices, two exposure models were developed to simulate the likelihood of exposure to MAC via tap water consumption in this sensitive population. The first model integrated data from studies that described sources of water for consumption and post-tap treatment rates in cohorts infected with human immunodeficiency virus (HIV(+)). The second model used data from a study that categorized the fraction of water intake consisting of tap water that was not further treated. Approximately 1500 individuals with advanced AIDS were estimated to ingest tap water with detectable concentrations of MAC organisms daily. Additional studies on tap-water use in U.S. HIV(+) populations are needed to confirm these findings. Longitudinal and cross-sectional studies on the occurrence of MAC in tap water, particularly in regions with large HIV(+)/AIDS populations, would help address some of the uncertainty in these exposure estimates.

AIDS-Related Opportunistic Infections↗
PubMed2000

Exploring spatial patterns of particulate sulfur and OMH from the Project MOHAVE summer intensive regional network using analyses of variance techniques and meteorological parameters as sort determinants.

Project MOHAVE (Measurements of Haze and Visual Effects) encompassed a 1-yr field study in the southwestern United States from September 1991 through August 1992. The congressionally mandated study was a joint partnership between the U.S. Environmental Protection Agency, Southern California Edison, and the National Park Service. A major objective of this study was to quantify the potential haze impacts on the nearby Grand Canyon National Park from the 1580 MW coal-fired MOHAVE Power Project (MPP). Any regional impacts from MPP were from secondary fine sulfate. In this paper, we explore the temporal and spatial patterns of particulate sulfur (Sp) and "organic mass by hydrogen" (OMH) during the summer intensive, conducted from mid-July through the end of August 1992. Using an innovative hierarchical pattern recognition classification scheme, we developed 6 groups of Sp and 8 groups of OMH temporally similar behaving patterns in the sampling region. From a regional understanding of synoptic meteorology, these Sp patterns were explainable. We observed two regional gradients. One gradient was a west-to-east decreasing gradient, most likely the result of major sources from urban southern California, including the San Joaquin Valley. The other decreasing gradient was from south-to-north, perhaps the result of emissions emanating from the large urban centers in northern Mexico. The patterns for OMH were not as regionally homogeneous as the patterns for Sp. A west-to-east decreasing gradient was observed for OMH, along with reduced values in the lower Colorado River Valley and some higher values in central and eastern Arizona. The west-to-east decreasing gradient suggests the presence of the Los Angeles urban plume, while the higher values in central and eastern Arizona may be due to biogenic emissions and increased seasonal fires.

Air Pollution↗
PubMed1983

Biodegradation and photolysis of pentachlorophenol in artificial freshwater streams.

The biodegradation, photolysis, and adsorption of pentachlorophenol (PCP) in outdoor, aquatic environments were examined with man-made channels built by the U.S. Environmental Protection Agency at a field station on the Mississippi River near Monticello, Minn. Four channels were used, each channel being approximately 520 m long and receiving river water that flowed through the channels for about 10 h before reentering the river. The channels were dosed continuously during the summer of 1982 with various concentrations of PCP (approximately 0, 48, 144, and 432 micrograms/liter). We monitored the biotic and abiotic degradation of PCP in these channels for approximately 16 weeks. Photolysis of PCP was rapid at the water surface, but greatly attenuated with depth. Depending on sunlight conditions, photolysis accounted for a 5 to 28% decline in initial PCP concentration. Adsorption of PCP by sediment and uptake by biota accounted for less than 15% and probably less than 5% in unacclimated water. Microbial degradation of PCP became significant about 3 weeks after the initiation of dosing and eventually became the primary mechanism of PCP removal, accounting for a 26 to 46% (dose-dependent) decline in initial PCP. Most of the PCP-mineralizing microorganisms that developed in the channels were either attached to surfaces (e.g., rocks and macrophytes) or associated with surface sediments. Total bacterial numbers (direct microscopic counts) in the various channels were not affected significantly by PCP concentrations of micrograms per liter. Numerous strains of bacteria able to grow at the expense of PCP were isolated from the adapted channels. The experiments reported here will help predict the responses of flowing aquatic ecosystems to contamination by biocides such as pentachlorophenol.

Adsorption↗
PubMed1977

Evaluation of guidelines for safe exposure to continuous noise of moderate and high intensity.

In a 1974 report the Environmental Protection Agency made predictions, based upon extrapolations from the literature, as to what constitutes a 5 dB equal 90th percentile TTS2 curve, i.e., a "safe exposure" curve. However, because of a dearth of data for brief exposures to noise, they were uncertain as to the accuracy of some of their predictions. Therefore, in the present investigation, the TTS2 consequences of brief exposures to noise were systematically evaluated. Specifically, 40 subjects were tested at each of 10 appropriately spaced durations of exposure to noise. The 90th percentile TTS2 at 4000 Hz was determined for each duration of exposure and then a multiple regression equation was fitted to these values. From this equation, a 5 dB equal 90th percentile TTS2 curve was calculated, which represents our predictions as to the trade-offs between noise intensity and duration of exposure necessary to produce 90th percentile TTS2S of 5 dB. A comparison of our predictions to those of the EPA (in the area of uncertainty) suggests that the conservative EPA predictions may be too conservative while the EPA's modified and extended CHABA-criterion predictions (from Nat. Acad. Sci., Nat. Res. Council Committee on Hear., Bioacoustics, Biomechanics) may not be sufficiently conservative. Although our predictions reflect the trends which were actually observed in the present investigation, it would be unreasonable to assume that our predictions are more than "ball park" estimates of reality. They do suggest, though, that in reality a 5 dB equal 90th percentile TTS2 curve would probably be intermediate between the conservative EPA curve and EPA's modified and extended CHABA criterion curves.

Audiometry↗
PubMedDate not supplied

Enumeration of coliform bacteria in wastewater solids using defined substrate technology.

Commercially available defined substrate technology for the enumeration of coliform bacteria was investigated for its applicability to waste activated sludge (WAS) solids. The defined substrate, Colilert, in conjunction with the QuantiTray enumeration system, was compared with multiple-tube fermentation (MTF). Multiple-tube fermentation analyses (U.S. Environmental Protection Agency [U.S. EPA]-accepted methods for the enumeration of coliforms in wastewater solids) were conducted on settled wastewater solids using lauryl tryptose broth as the presumptive phase and brilliant-green lactose bile broth for the confirmed phase of total coliform enumeration. Both EC medium for fecal coliform identification and EC-4-methyl-umbelliferyl-beta-D-glucuronide (MUG) media for Escherichia coli for the MTF completed phase were also conducted on the WAS. Samples analyzed included raw WAS and WAS that had been pasteurized at 70 degrees C for 15 and 30 minutes, respectively. Twenty replicates of each sample were measured to demonstrate statistical equivalence of the total coliform numbers for all three WAS samples (raw, 15-minute pasteurization, and 30-minute pasteurization). Results show that both systems provided statistically equal total coliform most probable numbers (MPNs) for all samples tested. As expected, fecal coliform numbers identified by the MTF technique were statistically higher than E. coli enumerated by Colilert-QuantiTray. However, the E. coli MPN generated by the MTF method was found to be statistically equal to the Colilert-QuantiTray numbers. Because of its ease of use and reduced time to obtain the analysis, the Colilert-QuantiTray system can be useful in enumerating coliforms in WAS. However, more data are required to definitively show equivalence of the commercially available defined substrate technology to the U.S.-EPA accepted protocol. It is hoped that the results of this study will help form a database for the acceptance of the Colilert-QuantiTray system for WAS bacterial analyses.

Bacteriological Techniques↗
PubMed2000

The effect of coal combustion flue gas components on low-level chlorine speciation using EPA method 26A.

U.S. Environmental Protection Agency (EPA) Method 26A is the recommended procedure for capturing and speciating halogen (X2) and hydrogen halide (HX) stack emissions from combustion sources. Previous evaluation studies of Method 26A have focused primarily on hydrogen chloride (HCl) speciation. Capture efficiency, bias, and the potential interference of Cl2 at high levels (> 20 ppm [microgram/m3]) and NH4Cl in the flue gas stream have been investigated. It has been suggested that precise Cl2 measurement and accuracy in quantifying HX or X2 using Method 26A are difficult to achieve at Cl2 concentrations < 5 ppm; however, no performance data exist to support this. Coal contains low levels of Cl, in the range of 5-2000 ppmw, which results in the presence of HCl and Cl2 in the products of combustion. HCl is the predominant Cl compound formed in the high-temperature combustion process, and it persists in the gas as the products of combustion cool. Concentrations of Cl2 in coal combustion flue gas at stack temperatures typically do not exceed 5 ppm. For this research, bench-scale experiments using simulated combustion flue gas were designed to validate the ability of Method 26A to speciate low levels of Cl2 accurately. This paper presents the results of the bench-scale tests. The effect of various flue gas components is discussed. The results indicate that SO2 is the only component in coal combustion flue gas that has an appreciable effect on Cl2 distribution in Method 26A impingers, and that Method 26A cannot accurately speciate HCl and Cl2 in coal combustion flue gas without modification.

Air Pollutants↗
PubMed2000

Workplace monitoring of refractory ceramic fiber in the United States.

This paper summarizes data from a comprehensive workplace exposure monitoring program for refractory ceramic fiber (RCF) conducted since 1990, including data collected under a 5-year consent agreement (1993-1998) between the U.S. Environmental Protection Agency and the Refractory Ceramic Fibers Coalition. It presents additional data and analyses, which complement an earlier article published in this journal (L. D. Maxim et al., 1997, Regul. Toxicol. Pharmacol. 26, 156-171). As part of this exposure monitoring program, data were collected at plants operated by RCF manufacturers and at customer facilities. Beginning in 1993, at least 720 samples (each sample consisting of one or more cassettes) were collected annually, distributed according to a stratified random sampling plan. The strata consisted of workers in eight functional job categories (FJCs) at manufacturing and customer plants. Time-weighted average (TWA) and task length average data were gathered and analyzed using phase contrast optical microscopy and (for a subset of samples) transmission electron microscopy methods. Data on respirator usage (by type) were also collected. Statistical analysis indicates that there are significant differences in TWA fiber concentrations (exposure) among FJCs (installation, finishing, and removal categories have the highest average concentrations), that workplace concentration data are approximately lognormally distributed, and that weighted average fiber concentrations decreased over the period from 1990 to 1998-although trend curves leveled out as exposures have decreased and further improvements became more difficult. Material differences exist in exposure between RCF manufacturers and their customers (largely because the mix of jobs differ), but these differences have narrowed over the years. Respirator usage varies with exposure. Respirator data are used to derive improved estimates of actual worker exposure. Alternative criteria for selecting FJCs for control efforts are defined and illustrated. Lessons learned for future monitoring efforts are summarized.

Environmental Monitoring↗
PubMed2005

Review and analysis of inhalation dosimetry methods for application to children's risk assessment.

Young children have a greater ventilation rate per body weight or pulmonary surface area as compared to adults. The implications of this difference for inhalation dosimetry and children's risk assessment were evaluated in runs of the U.S. Environmental Protection Agency (U.S. EPA) 1994 reference concentration (RfC) methodology and the ICRP 1994 inhalation dosimetry model. Dosimetry estimates were made for 3-mo-old children and adults for particles and Category 1 and 2 reactive gases in the following respiratory-tract regions: extrathoracic (ET), tracheobronchial (BB), bronchioles (bb), and pulmonary (PU). Systemic dosimetry estimates were made for nonreactive (Category 3) gases. Results suggest similar ET dosimetry for children and adults for all types of inhaled materials. BB dosimetry was also similar across age groups except that the dosimetry of ultrafine particles in this region was twofold greater in 3-mo-old children than in adults. In contrast, the bb region generally showed higher dosimetry of particles and gases in adults than in children. Particle dose in the PU region was two- to fourfold higher in 3-mo-old children, with the greatest child/adult difference occurring for submicron size particles. Particulate dosimetry estimates with the default RfC methodology were below those found with the ICRP model for both adults and children for submicrometer sized particles. There were no cases in which reactive gas dosimetry was substantially greater in the respiratory regions of 3-mo-old children. Estimates of systemic dose of Category 3 gases were greater in 3-mo-old children than in adults, especially for liver dose of metabolite for rapidly metabolized gases. These analyses support the approach of assuming twofold greater inhalation dose in children than adults, although there are cases in which this differential can be greater and others where it can be less.

Administration, Inhalation↗
PubMed1995

Epidemiologic studies on short-term effects of low levels of major ambient air pollution components.

Since the development of the World Health Organization (WHO) Air Quality Guidelines for Europe, a large number of epidemiologic studies have been published documenting effects of major air pollutants on health at concentrations below existing guidelines and standards. In this review, recent studies are discussed that permit some evaluation of short-term health effects observed at exposure levels lower than the current WHO Guidelines or U.S. Environmental Protection Agency (U.S. EPA) standards. Some studies have been conducted at concentration levels that never exceeded existing guidelines or standards. Other studies have been conducted at exposure levels sometimes exceeding current guidelines or standards. The published analyses of several of these studies permit evaluation of low-level health effects either because analyses were restricted to levels not exceeding the guidelines or graphic analyses were reported suggesting effects at these low levels. For ambient ozone, effects on lung function of subjects exercising outdoors have now been documented at 1-hr maximum levels not exceeding 120 micrograms/m3, i.e., half the current U.S. EPA standard. One study even suggests that such effects occur at levels below 100 micrograms/m3. Several studies are now available documenting effects of particulate air pollution on health in the virtual absence of SO2. Effects on mortality and hospital admissions for asthma have been documented at levels not exceeding 100 micrograms/m3, expressed as 24-hr average inhalable particles PM10 concentration. Effects on lung function, acute respiratory symptoms, and medication use have been found at 24-hr average PM10 levels not exceeding 115 micrograms/m3. When the WHO Air Quality Guidelines and the U.S. EPA standard for PM10 were developed, there were no studies available on health effects of PM10. In this review, we include nine studies documenting health effects of measured PM10 at low levels of exposure, indicating that there is now an entirely new epidemiologic database that can be evaluated in the process of revising current guidelines and standards. The low levels of exposure at which effects on health were seen underscore the urgent need for such reevaluations.

Air Pollutants↗
PubMed2004

Adipose tissue levels of organochlorine pesticides and polychlorinated biphenyls and risk of non-Hodgkin's lymphoma.

In this nested case-control study we examined the relationship between non-Hodgkin's lymphoma (NHL) and organochlorine pesticide exposure. We used a data set originally collected between 1969 and 1983 in the U.S. Environmental Protection Agency National Human Adipose Tissue Survey. Adipose samples were randomly collected from cadavers and surgical patients, and levels of organochlorine pesticide residues were determined. From the original study population, 175 NHL cases were identified and matched to 481 controls; 173 controls were selected from accident victims, and 308 from cases with a diagnosis of myocardial infarction. Cases and controls were mainly from cadavers (> 96%) and were matched on sex, age, region of residence within the United States, and race/ethnicity. Conditional logistic regression showed the organochlorine pesticide residue heptachlor epoxide to be significantly associated with NHL [compared with the lowest quartile: third quartile odds ratio (OR) = 1.82, 95% confidence interval (CI), 1.01-3.28; fourth quartile OR = 3.41, 95% CI, 1.89-6.16]. The highest quartile level of dieldrin was also associated with elevated NHL risk (OR = 2.70; 95% CI, 1.58-4.61), as were higher levels of oxychlordane, p,p'-DDE [p,p'-1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], and ss-benzene hexachloride (ORs = 1.79, 1.99, and 2.47, respectively). The p-values for trends for these associations were significant. In models containing pairs of pesticides, only heptachlor epoxide and dieldrin remained significantly associated with risk of NHL. Limitations of this study include collection of samples after diagnosis and a lack of information on variables affecting organochlorine levels such as diet, occupation, and body mass index. Given the persistence of pesticides in the environment, these findings are still relevant today.

Adipose Tissue↗
PubMedDate not supplied

Reducing long-term remedial costs by transport modeling optimization.

The Department of Defense (DoD) Environmental Security Technology Certification Program and the Environmental Protection Agency sponsored a project to evaluate the benefits and utility of contaminant transport simulation-optimization algorithms against traditional (trial and error) modeling approaches. Three pump-and-treat facilities operated by the DoD were selected for inclusion in the project. Three optimization formulations were developed for each facility and solved independently by three modeling teams (two using simulation-optimization algorithms and one applying trial-and-error methods). The results clearly indicate that simulation-optimization methods are able to search a wider range of well locations and flow rates and identify better solutions than current trial-and-error approaches. The solutions found were 5% to 50% better than those obtained using trial-and-error (measured using optimal objective function values), with an average improvement of approximately 20%. This translated into potential savings ranging from 600,000 dollars to 10,000,000 dollars for the three sites. In nearly all cases, the cost savings easily outweighed the costs of the optimization. To reduce computational requirements, in some cases the simulation-optimization groups applied multiple mathematical algorithms, solved a series of modified subproblems, and/or fit "meta-models" such as neural networks or regression models to replace time-consuming simulation models in the optimization algorithm. The optimal solutions did not account for the uncertainties inherent in the modeling process. This project illustrates that transport simulation-optimization techniques are practical for real problems. However, applying the techniques in an efficient manner requires expertise and should involve iterative modification to the formulations based on interim results.

Algorithms↗