MTBE is a colorless, relatively volatile liquid that has found widespread use as an octane‐enhancing gasoline additive. In 1987, the Environmental Protection Agency's (EPA) Interagency Testing Committee identified MTBE for priority testing consideration based on large production volume, potential widespread exposure, and limited data on chronic health effects. In response, the industry formed the MTBE Health Effects Testing Task Force, which in 1988 signed a Consent Agreement with the EPA requiring the task force member companies to perform toxicological testing on MTBE.
The testing program, which began in the second quarter of 1988, consists of a full complement of short‐ and long‐term tests. The testing completed to date includes genotoxicity (in vivo bone marrow cytogenetics and Drosophila sex‐linked recessive lethal assays), developmental toxicity, acute and subchronic neurotoxicity (motor activity, functional observation battery, and neuropathology), subchronic toxicity, reproductive/fertility effects, and pharmacokinetic studies. There is also an ongoing oncogenicity study in rats and mice. The final report for this chronic study is expected at the end of 1992. The total cost for the program is approximately $3.75 million, which is funded by the 11 Task Force member companies based on market share.
These studies were sponsored by the MTBE Health Effects Testing Task Force, Oxygenated Fuels Association, Washington, D.C. 相似文献
Two systems for exposing mice to 2,450-MHz electromagnetic fields are described. In a waveguide system, four mice were placed in a Styrofoam cage and exposed dorsally to circularly polarized electromagnetic fields. The temperature and humidity in the mouse holder were kept constant by forced-air ventilation. For 1-W input power to the waveguide, the average specific absorption rate (SAR) was determined by twin-well calorimetry to be 3.60 ± 0.11 (SE) W/kg in 27-g mice. The maximum SAR at the skin surface determined thermographically was 8.36 W/kg in the head of the mouse. The second system was a miniature anechoic chamber. Six mice were irradiated dorsally to far field plane waves. Copper shielding and high-temperature absorbing material were lined inside the chamber to accommodate the high input power. The air ventilation at the location of the mice was separately controlled so that any heating in the absorber would not affect the animals. For 1-W input power, the average SAR was 0.17 ± 0.01 W/kg and the maximum SAR at the skin surface was 0.41 W/kg in the animal when irradiated with body axis parallel to the E field; the SARs were 0.11 ± 0.01 W/kg and 0.64 W/kg, respectively, when irradiated perpendicular to the E field. 相似文献
Urban and periurban forests, which are integrated within the concept of Green Infrastructure, provide important Ecosystem Services, including air purification. In this study, we quantified the Ecosystem Service of particulate matter (PM10) and Ozone (O3) removal from urban and periurban forests in ten metropolitan cities in Italy, and its total monetary value. In order to gain a better understanding of how Ecosystem Services can be regulated on a wider scale, the vegetation ecosystem types were grouped into Physiognomic-Structural Categories of Vegetation according to morphofunctional criteria. The pollution removal was mapped using a remote sensing and GIS approach, by applying a deposition model and a stomatal flux model. We estimated, for the ten metropolitan cities, an overall pollution abatement of 7150 Mg of PM10 and 30,014 Mg of O3 in the year 2003, which was an extremely hot year. Our findings indicate that structural characteristics (i.e. Leaf Area Index) and functional diversity, linked to stomatal conductance, exert a marked influence on the provision of the regulating Ecosystem Services, whose total monetary value was estimated to be equal to 47 and 297 million USD for PM10 and O3 removal, respectively. This study represent the first national-scale assessment of the Ecosystem Services of air pollution removal in Europe, thus providing information that may be useful to stakeholders to manage Green Infrastructure more efficiently. 相似文献
Spiders can use air particle movements to localize moving prey. We studied the responses of 32 wind-sensitive interneurones
in the hunting spider Cupiennius salei to prey stimuli.
Stimulation with a tethered flying fly or with artificial air pulses activated plurisegmental interneurones that responded
to changes in air movement velocity and were thus well suited to represent the highly fluctuating air stream typical of prey
stimuli. In most interneurones (n = 18) the responses to the stimulation of different legs were not significantly different from each other.
Different interneurones had different response characteristics and their latencies largely overlapped suggesting that there
is parallel processing of the signals by populations of interneurones with different response characteristics.
In two interneurones the number of spikes and the spiking pattern elicited by stimulation of each of the eight legs markedly
differed depending on the leg stimulated. These neurones may play an important role in directional information processing.
Stimulation of the adjacent legs from front to back or from back to front revealed two interneurones sensitive to the direction
of successive stimulation of the legs. These neurones may be able to detect the motion of an air movement source in a preferred
direction and thus act as nearfield motion detectors to localize a moving prey item.
Accepted: 28 September 1996 相似文献
Summary Leaves of olive trees growing in the vicinity of the Aluminium Factory of Greece were ultrastructurally investigated in order to determine any malformations caused by environmental air pollutants, especially hydrogen fluoride, in comparison with control samples and normal seasonal senescence. Estimation of some elements accumulated by these leaves showed that they contained high amounts of F and Al attributable to the operation of the nearby factory. The most seriously effected cell components were found to be the mesophyll chloroplasts that show a dilation of the intrathylakoid space, increase of the number of plastoglobuli, discoloration of plastoglobuli, accumulation of large starch grains and an overall disorganized appearance of the organelle. The nuclear crystalloid inclusions have unusual shapes, while the vacuoles contain a fibrillar/granular material that increases their electron density. It is concluded that the ultrastructural malformations are caused by a combination of environmental stresses and air pollutants.This paper is dedicated to Professor Dr. Eberhard Schnepf on the occasion of his 60th birthday. 相似文献
Under the Red Queen hypothesis, outcrossing can produce genetically variable progeny, which may be more resistant, on average, to locally adapted parasites. Mating with multiple partners may enhance this resistance by further increasing the genetic variation among offspring. We exposed Potamopyrgus antipodarum to the eggs of a sterilizing, trematode parasite and tested whether this altered mating behaviour. We found that exposure to parasites increased the number of snail mating pairs and the total number of different mating partners for both males and females. Thus, our results suggest that, in host populations under parasite-mediated selection, exposure to infective propagules increases the rate of mating and the number of mates. 相似文献
To explain the underlying causes of apparently stochastic disease, current research is focusing on systems biology approaches wherein individual genetic makeup and specific ‘gene–environment’ interactions are considered. This is an extraordinarily complex task because both the environmental exposure profiles and the specific genetic susceptibilities presumably have large variance components. In this article, the focus is on the initial steps along the path to disease outcome namely environmental uptake, biologically available dose, and preclinical effect. The general approach is to articulate a conceptual model and identify biomarker measurements that could populate the model with hard data. Between-subject variance components from different exposure studies are used to estimate the source and magnitude of the variability of biomarker measurements. The intent is to determine the relative effects of different biological media (breath or blood), environmental compounds and their metabolites, different concentration levels, and levels of environmental exposure control. Examples are drawn from three distinct exposure biomarker studies performed by the US Environmental Protection Agency that studied aliphatic and aromatic hydrocarbons, trichloroethylene and methyl tertiary butyl ether. All results are based on empirical biomarker measurements of breath and blood from human subjects; biological specimens were collected under appropriate Institutional Review Board protocols with informed consent of the subjects. The ultimate goal of this work is to develop a framework for eventually assessing the total susceptibility ranges along the toxicological pathway from exposure to effect. The investigation showed that exposures are a greater contributor to biomarker variance than are internal biological parameters. 相似文献