United States Environmental Protection Agency

About: United States Environmental Protection Agency is a government organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Population & Environmental exposure. The organization has 13873 authors who have published 26902 publications receiving 1191729 citations. The organization is also known as: EPA & Environmental Protection Agency.

Characterization of organosulfates from the photooxidation of isoprene and unsaturated fatty acids in ambient aerosol using liquid chromatography/(-) electrospray ionization mass spectrometry

Abstract: In the present study, we have characterized in detail the MS(2) and MS(3) fragmentation behaviors, using electrospray ionization (ESI) in the negative ion mode, of previously identified sulfated isoprene secondary organic aerosol compounds, including 2-methyltetrols, 2-methylglyceric acid, 2-methyltetrol mononitrate derivatives, glyoxal and methylglyoxal A major fragmentation pathway for the deprotonated molecules of the sulfate esters of 2-methyltetrols and 2-methylglyceric acid and of the sulfate derivatives of glyoxal and methylglyoxal is the formation of the bisulfate [HSO(4)](-) anion, while the deprotonated sulfate esters of 2-methyltetrol mononitrate derivatives preferentially fragment through loss of nitric acid Rational interpretation of MS(2), MS(3) and accurate mass data led to the structural characterization of unknown polar compounds in K-puszta fine aerosol as organosulfate derivatives of photooxidation products of unsaturated fatty acids, ie 2-hydroxy-1,4-butanedialdehyde, 4,5- and 2,3-dihydroxypentanoic acids, and 2-hydroxyglutaric acid, and of alpha-pinene, ie 3-hydroxyglutaric acid The deprotonated molecules of the sulfated hydroxyacids, 2-methylglyceric acid, 4,5- and 2,3-dihydroxypentanoic acid, and 2- and 3-hydroxyglutaric acids, showed in addition to the [HSO(4)](-) ion (m/z 97) neutral losses of water, CO(2) and/or SO(3), features that are characteristic of humic-like substances The polar organosulfates characterized in the present work are of climatic relevance because they may contribute to the hydrophilic properties of fine ambient aerosol In addition, these compounds probably serve as ambient tracer compounds for the occurrence of secondary organic aerosol formation under acidic conditions

A Meta‐Analysis of Children's Hand‐to‐Mouth Frequency Data for Estimating Nondietary Ingestion Exposure

Abstract: Because of their mouthing behaviors, children have a higher potential for exposure to available chemicals through the nondietary ingestion route; thus, frequency of hand-to-mouth activity is an important variable for exposure assessments. Such data are limited and difficult to collect. Few published studies report such information, and the studies that have been conducted used different data collection approaches (e.g., videography versus real-time observation), data analysis and reporting methods, ages of children, locations, and even definitions of "mouthing." For this article, hand-to-mouth frequency data were gathered from 9 available studies representing 429 subjects and more than 2,000 hours of behavior observation. A meta-analysis was conducted to study differences in hand-to-mouth frequency based on study, age group, gender, and location (indoor vs. outdoor), to fit variability and uncertainty distributions that can be used in probabilistic exposure assessments, and to identify any data gaps. Results of this analysis indicate that age and location are important for hand-to-mouth frequency, but study and gender are not. As age increases, both indoor and outdoor hand-to-mouth frequencies decrease. Hand-to-mouth behavior is significantly greater indoors than outdoors. For both indoor and outdoor hand-to-mouth frequencies, interpersonal, and intra-personal variability are approximately 60% and approximately 30%, respectively. The variance difference among different studies is much bigger than its mean, indicating that different studies with different methodologies have similar central values. Weibull distributions best fit the observed data for the different variables considered and are presented in this article by study, age group, and location. Average indoor hand-to-mouth behavior ranged from 6.7 to 28.0 contacts/hour, with the lowest value corresponding to the 6 to <11 year olds and the highest value corresponding to the 3 to <6 month olds. Average outdoor hand-to-mouth frequency ranged from 2.9 to 14.5 contacts/hour, with the lowest value corresponding to the 6 to <11 year olds and the highest value corresponding to the 6 to <12 month olds. The analysis highlights the need for additional hand-to-mouth data for the <3 months, 3 to <6 months, and 3 to <6 year age groups using standardized collection and analysis because of lack of data or high uncertainty in available data. This is the first publication to report Weibull distributions as the best fitting distribution for hand-to-mouth frequency; using the best fitting exposure factor distribution will help improve estimates of exposure. The analyses also represent a first comprehensive effort to fit hand-to-mouth frequency variability and uncertainty distributions by indoor/outdoor location and by age groups, using the new standard set of age groups recommended by the U.S. Environmental Protection Agency for assessing childhood exposures. Thus, the data presented in this article can be used to update the U.S. EPA's Child-Specific Exposure Factors Handbook and to improve estimates of nondietary ingestion in probabilistic exposure modeling.

A roadmap for the development of alternative (non-animal) methods for systemic toxicity testing.

Abstract: Systemic toxicity testing forms the cornerstone for the safety evaluation of substances. Pressures to move from traditional animal models to novel technologies arise from various concerns, including: the need to evaluate large numbers of previously untested chemicals and new products (such as nanoparticles or cell therapies), the limited predictivity of traditional tests for human health effects, duration and costs of current approaches, and animal welfare considerations. The latter holds especially true in the context of the scheduled 2013 marketing ban on cosmetic ingredients tested for systemic toxicity. Based on a major analysis of the status of alternative methods (Adler et al., 2011) and its independent review (Hartung et al., 2011), the present report proposes a roadmap for how to overcome the acknowledged scientific gaps for the full replacement of systemic toxicity testing using animals. Five whitepapers were commissioned addressing toxicokinetics, skin sensitization, repeated-dose toxicity, carcinogenicity, and reproductive toxicity testing. An expert workshop of 35 participants from Europe and the US discussed and refined these whitepapers, which were subsequently compiled to form the present report. By prioritizing the many options to move the field forward, the expert group hopes to advance regulatory science.

Selective Vulnerability of Embryonic Cell Populations to Ethanol-Induced Apoptosis: Implications for Alcohol-Related Birth Defects and Neurodevelopmental Disorder

Abstract: Background: Ethanol-induced cell death has been characterized in very few stages of embryogenesis. This investigation comprehensively maps patterns of both programmed and ethanol-induced cell death in the central nervous system and craniofacial region at 0.5-day intervals from gestational day (GD) 6.5 to 11 in mice. Methods: A teratogenic dosage of ethanol (2.9 g/kg) or vehicle was administered via two intraperitoneal injections to pregnant C57BL/6J mice at various stages of gestation. Cell death patterns were characterized using Nile blue sulfate vital staining and histological analysis of plastic sections. Confocal laser scanning microscopy of LysoTracker Red–stained specimens allowed for three-dimensional visualization of areas of apoptosis and precise sectional imaging of mouse embryos. Apoptosis was also documented using a TUNEL technique on histological sections. Results: Normal programmed cell death in control embryos was noted in the prechordal plate region at GD 8, the neuroepithelium of the fourth ventricle and anterior neuropore at GD 9, and within the ganglia of cranial nerves V, VII–VIII, IX, and X at GD 10. Acute maternal ethanol administration 12 hr before examination resulted in a dramatic increase in apoptosis within sites of programmed cell death in the embryo. Moreover, ethanol-exposed specimens exhibited stage-dependent excessive cell death in other distinct cell populations, particularly within the developing central nervous system. Ethanol-induced apoptosis was notable as follows: GD 7.5-neuroectoderm; GD 8-neural plate and primitive streak; GD 9-alar plate and presumptive neural crest of the rostral hindbrain, especially at the mesencephalon/rhombencephalon junction; GD 9.5–10-branchial arches and rhombomeres; and GD 11-diencephalon, basal ganglia, pons, and developing cerebellum. Conclusions: The results of this study revealed developmental stage-specific cell populations of the developing brain and craniofacial region that are vulnerable to ethanol-induced apoptosis and provide new insight relative to the genesis of alcohol-related birth defects.

pH-Dependent toxicity of Cd, Cu, Ni, Pb and Zn to Ceriodaphnia dubia, Pimephales promelas, Hyalella azteca and Lumbriculus variegatus

Abstract: The speciation and bioavailability of metals are known to be affected by pH. Although many studies have focused on effects on metals of pH changes resulting from lake acidification (i.e., pH change 7 to 4), metal toxicity changes at higher pH values (i.e., pH 6-9) are of great interest to those performing effluent and sediment toxicity testing and toxicity identification evaluations (TIEs). In addition, most previous studies have addressed metal toxicity changes with pH to water-column organisms rather than to benthic or epibenthic species. We tested the acute toxicity of five metals (Cd, Cu, Ni, Pb, and Zn) to Ceriodaphnia dubia, Pimephales promelas, Hyalella azteca, and Lumbriculus variegatus at three pH values (6.3,7.3, and 8.3) in very hard reconstituted water (hardness 300-320 mg/L as CaCO3). Toxicity of Cd, Ni, and Zn was greatest at pH 8.3 and least at pH 6.3 to most of these species. Conversely, the toxicity of Cu and Pb was greatest at pH 6.3 and least at pH 8.3 to most of the species. The acute toxicity of most of the metals to Lumbriculus variegatus was very low and occasionally was above the aqueous solubility of the metal salts in the reconstituted water.