Myers J.L.,Texas Commission on Environmental Quality
Inhalation Toxicology | Year: 2016
The Texas Commission on Environmental Quality (TCEQ) conducts up-to-date carcinogenic assessments for chemicals emitted in Texas. An inhalation unit risk factor (URF) was developed for ethylene dichloride (EDC, CAS 107-06-2) based on tumorigenicity results observed in a 2-year animal inhalation study conducted by Nagano et al. More specifically, the incidence of combined mammary gland tumors (adenomas, fibroadenomas, adenocarcinomas) in female rats demonstrated a statistically significant dose–response relationship, was amenable to benchmark concentration (BMC) modeling, was ultimately determined to be the most sensitive tumorigenic effect in the most sensitive species and sex, and was utilized as the carcinogenic endpoint for the development of the URF. The 95% lower confidence limit of the BMC at the 10% excess risk level (BMCL10 of 40.1 ppm) was determined for calculation of the URF. The resulting URF based on increased incidence of combined mammary gland tumors in female rats is 1.4E-02 per ppm (3.4E-03 per mg/m3). The lifetime air concentration corresponding to a no significant excess risk level of 1 in 100 000 is 0.71 ppb (2.9 μg/m3), which is considered sufficiently health-protective for use in protecting the general public against the potential carcinogenic effects of chronic exposure to EDC in ambient air. © 2016 Informa UK Limited, trading as Taylor & Francis Group.
Lakshmanan D.,University of Houston |
Howell N.L.,University of Houston |
Rifai H.S.,University of Houston |
Koenig L.,Texas Commission on Environmental Quality
Chemosphere | Year: 2010
An on-going study in the Houston Ship Channel (HSC) characterized polychlorinated biphenyl (PCB) levels in sediment, water, and tissue in 2002-2003 and 2008. The observed PCB concentration ranges in all media were higher than those measured in other PCB-impacted water bodies in the world, with the highest concentrations occurring within the industrialized segments. Contrary to polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/PCDF) observations, the PCB concentrations in the dissolved phase were greater than the suspended phase. Possible explanations include passage of colloids, competition for adsorption sites from other hydrophobic contaminants, and continuing current sources. The PCB homologue distributions were similar for suspended water, sediment and tissue with the profile normalized around penta-chlorobiphenyls, while the dissolved phase profile normalized around tri-chlorobiphenyls. PCB-209 was detected in the suspended water phase and in sediment (10%) prompting interest into its sources to the HSC since PCB-209 was present only in rare commercial mixtures and is a byproduct in very few manufacturing processes. Inter-media analyses showed a significant correlation and transfer of PCBs. Dioxin-like PCBs contributed significant toxicity to total equivalent in tissue (33%), while they were insignificant in water (<10%) and sediment (<5%). The PCB concentrations over time showed a significant decrease in suspended water, sediment and tissue, while dissolved water concentrations showed insignificant change. The homolog distribution, however, showed a significant change in dissolved water and fish, a minor change in sediment and insignificant change in suspended water. Furthermore, an analysis for six representative congeners showed that they were accurate in predicting the total PCB concentrations and could be thus used as indicator PCBs. © 2010 Elsevier Ltd.
Agca M.,Texas A&M University |
Popescu S.C.,Texas A&M University |
Harper C.W.,Texas Commission on Environmental Quality
Canadian Journal of Forest Research | Year: 2011
Crown fires, the fastest spreading of all forest fires, can occur in any forest type throughout the world. The overall aim of this study was to estimate forest canopy fuel parameters including canopy bulk density and canopy base height for loblolly pines (Pinus taeda L.) at the plot level using both allometric equations and CrownMass/FMAPlus software. Allometric equation results were compared with the CrownMass outputs for validation. According to our results, the calculated average canopy bulk density values, across all 50 plots, were 0.18 and 0.07 kg/m3 for the allometric equation and the CrownMass program, respectively. Lorey's mean height approach was used in this study to calculate canopy base height at the plot level. The average height values of canopy base height obtained from the Lorey height approach was 10.6 m and from the CrownMass program was 9.1 m. The results obtained for the two methods are relatively close to each other, with the estimate of canopy base height being 1.16 times larger than the CrownMass value. This study provides a practical method for quantifying these parameters and making them directly available to fire managers. The accuracy of these parameters is very important for realistic predictions of wildfire initiation and growth.
Liu X.,Texas Commission on Environmental Quality |
Xiao L.,Michigan State University |
IEEE Transactions on Computers | Year: 2012
A cut vertex is defined as a network node whose removal increases the number of network components. Failure of a cut vertex disconnects a network component and downgrades the network performance. Overlay networks are resilient to the failure of random nodes, but cut vertices that have been observed in real-world overlay traces make the network very vulnerable to well-constructed and targeted attacks. Traditional methods of detecting cut vertices are centralized and are very difficult, if not impossible, to be applied to large-scale and highly dynamic overlay networks. We aim to provide a practical solution by proposing a distributed mechanism that detects the cut vertices and neutralizes them to noncut vertices before they fail. The proposed mechanism not only minimizes the possibility of network decomposition on the cut vertex failure but also offloads the traffic that is handled by the cut vertices. We prove that our proposed method can correctly identify the cut vertices. We evaluate the performance of our design through trace-driven simulations. The results show that our method can successfully locate all cut vertices in the network and greatly offload the traffic processed by cut vertices. © 2012 IEEE.
« Toyota developing new cloud-based high-precision map generation system using data from production vehicles | Main | Mercedes-Benz publishes lifecycle analysis of its first PHEV SUV: GLE 500 e » The Texas Commission on Environmental Quality (TCEQ) is accepting applications for the Texas Natural Gas Vehicle Grant Program (TNGVGP) to improve air quality. Grants are available in one or more of the counties listed under the Clean Transportation Triangle (CTT) program, to include nonattainment areas, affected counties, and other counties inside the triangle area. Projects eligible for funding under this program must result in at least a 25% reduction of NO emissions. Vehicles funded under the TNGVGP must be operated in one or more of the eligible counties by the grantee at least 75% of the time. These Texas Emissions Reduction Plan (TERP) grants provide up to $37.8 million to entities that own and operate heavy-duty or medium-duty motor vehicles to replace vehicles with a natural gas vehicle or repower the vehicles with a natural gas engine. Grant applicants must go through a participating dealer under contract with the TCEQ in order to apply. An updated list of participating dealers and eligible counties is available on the TERP webpage. Applications will be accepted up to 26 May 2017 or until all funding has been awarded, whichever occurs earlier.