Methyl tertiary hexyl ether and methyl tertiary octyl ether as gasoline oxygenates: assessing risks from atmospheric dispersion and deposition

Methyl tertiary hexyl ether (MtHxE) and methyl tertiary octyl ether (MtOcE) are currently being developed as replacement oxygenates for methyl tertiary butyl ether (MtBE) in gasoline. As was the case with MtBE, the introduction of these ethers into fuel supplies guarantees their introduction into the environment as well. In this study, a screening-level risk assessment was performed by comparing predicted environmental concentrations (PEC) of these ethers to concentrations that might cause adverse effects to humans or ecosystems. A simple box model that has successfully estimated urban air concentrations of MtBE was adapted to predict atmospheric concentrations of MtHxE and MtOcE. Expected atmospheric concentrations of these ethers were also estimated using the European Union System for the Evaluation of Substances (EUSES) multimedia fate model, which simultaneously calculates PECs in the various environmental compartments of air, water, soil, and sediment. Because little or no data are available on the physicochemical, environmental, and toxicological properties of MtHxE and MtOcE, estimation methods were used in conjunction with EUSES to predict both the PECs and the concentrations at which these ethers might pose a threat. The results suggest that these ethers would contaminate the air of a moderately sized U.S. city (Boston, MA) at levels similar to those found previously for MtBE. The risk assessment module in EUSES predicted risk characterization ratios of 10(-3) and 10(-2) for MtHxE and MtOcE, respectively, in Boston, and 10(-2) and 10(-1) in very large urban centers, suggesting that these ethers pose only a minimal threat to ecosystems at the anticipated environmental concentrations. The assessment also indicates that these compounds are possible human carcinogens and that they may be present in urban air at concentrations that pose an unacceptable cancer risk. Therefore, testing of the toxicological properties of these compounds is recommended before they replace MtBE in gasoline.     

Protection from steam at high pressures: development of a test device and protocol.

Extensive use of pressurized steam in the oil and gas sectors has led to incidents where workers were seriously injured. In this study a test device and procedure to measure heat transfer through fabrics during steam exposure were developed and evaluated. Several factors were considered while designing the test device to simulate work site conditions. Fabrics were exposed to steam at 2 distances (50 and 100 mm) and 2 pressures (207 and 69 kPa). Theoretical considerations included heat and mass transfer, and fabric structure and performance properties. The test device and procedure differentiated well among both fabrics and exposure conditions. For all fabrics, maximum heat transfer was observed at highest steam pressure and shortest distance. Laminated and coated fabrics performed better than a fabric without such treatments.     

Size-assortative pairing across three developmental stages in the Zeus bug, Phoreticovelia disparata

The mechanisms underlying size-assortative pairing have received considerable attention. Typically, pairing is assumed to occur at, or just prior to, the adult phase of the life cycle. However, in many invertebrates, males commence associations with juvenile females who are more than a single moult away from sexual maturity. These species are ideal to explore the importance of reproductive and survival benefits as mechanisms driving size-assortative pairing. In the Zeus bug, Phoreticovelia disparata, adult males are found riding on juvenile (fourth and fifth instar) and adult females—a behaviour that is costly for females but has survival benefits for males. Using a combination of field collections and laboratory manipulations, we show that pairing is size-assortative both within and between female age classes and that riding males are smaller than non-riding males. In a series of mating trials, we revealed that males attempt to ride any female but that their riding success is dependent on female age. We also provide the first direct evidence of female resistance to male riding attempts in P. disparata. We propose that size-assortative pairing arises through adaptations that have evolved to minimise the potential costs of sexual conflict. We suggest that the selective pressure on males to maximise survival benefits is sufficiently high that it outweighs the reproductive benefits of discriminating against fourth instar females. Finally, given that female resistance is under direct selection in juvenile females, it is likely to be the main form of selective pressure for adult females.     

Organohalogen contaminants and metabolites in cerebrospinal fluid and cerebellum gray matter in short-beaked common dolphins and Atlantic white-sided dolphins from the western North Atlantic

Concentrations of several congeners and classes of organohalogen contaminants (OHCs) and/or their metabolites, namely organochlorine pesticides (OCs), polychlorinated biphenyls (PCBs), hydroxylated-PCBs (OH-PCBs), methylsulfonyl-PCBs (MeSO₂-PCBs), polybrominated diphenyl ether (PBDE) flame retardants, and OH-PBDEs, were measured in cerebrospinal fluid (CSF) of short-beaked common dolphins (n = 2), Atlantic white-sided dolphins (n = 8), and gray seal (n = 1) from the western North Atlantic. In three Atlantic white-sided dolphins, cerebellum gray matter (GM) was also analyzed. The levels of OCs, PCBs, MeSO₂-PCBs, PBDEs, and OH-PBDEs in cerebellum GM were higher than the concentrations in CSF. 4-OH-2,3,3′,4′,5-pentachlorobiphenyl (4-OH-CB107) was the only detectable OH-PCB congener present in CSF. The sum (Σ) OH-PCBs/Σ PCB concentration ratio in CSF was approximately two to three orders of magnitude greater than the ratio in cerebellum GM for dolphins.     

Emissions of isoprene,monoterpene and short-chained carbonyl compounds from Eucalyptus spp. in southern Australia

Eucalypts are among the highest emitters of biogenic volatile organic compounds, yet there is relatively little data available from field studies of this genus. Emissions of isoprene, monoterpenes and the short-chained carbonyls formaldehyde, acetaldehyde and acetone were determined from four species (Eucalyptus camaldulensis, Eucalyptus globulus, Eucalyptus grandis, and Eucalytpus viminalis) in Australia. A smaller comparative study was conducted on E. camaldulensis in south-eastern Australia. Carbonyl emissions, reported here for the first time from eucalypts, were generally comparable with rates reported for other species, with diurnal emissions peaking at about 4, 75 and 34 nmol m^?2 min^?1 for acetone, formaldehyde and acetaldehyde respectively. There was wide variation in diurnal isoprene and monoterpene emissions between species, but under standard conditions, isoprene emissions were much lower than previous reports. Conversely, standard emission rates of monoterpenes were as much as six times greater than previous reports for some species. Emission of each carbonyl was correlated with its ambient concentration across different species, but more weakly related to temperature. Acetaldehyde emission in particular was significantly correlated with transpiration, but not with sap flow or with ethanol concentrations in xylem sap, suggesting fermentation within the leaf and stomatal conductance are primary controlling processes. Differences in acetaldehyde exchange velocities between sites, in addition to transpiration differences, suggest stomata may indeed exert long term emission regulation, in contrast to compounds for which no biological sink exists.     

Open fetal surgery for myelomeningocele

Despite efforts at prevention through the use of preconception folic acid, spina bifida remains one of the most common congenital anomalies of the central nervous system that is compatible with life. It is, however, associated with a significant degree of lifelong morbidity. The development of open fetal surgery for myelomeningocele (MMC) has been a long process but one that serves as a model for how new procedures and technologies need to be properly evaluated before being brought into mainstream medical practice. Even so, risks and benefits need to be evaluated for each patient. The currently available studies have been carried out on a highly selected patient population where the fetal findings provided the maximum opportunity for benefit from prenatal closure of the MMC defect. There is the potential that as the surgery becomes more widely available, pressure will be brought to bear to perform surgery in cases where the likelihood for benefit is decreased and yet the risks are not. The only way to duplicate the results of the current studies is to follow the methodology and criteria that were used in the studies. This will mean that not every fetus with an MMC will be a candidate for in utero surgery. The balance of risk to benefit will continue to evolve as further technological advances are evaluated and more follow-up information is obtained. Copyright © 2011 John Wiley & Sons, Ltd.