State-of-the-Science Workshop Report: Issues and Approaches in Low-Dose–Response Extrapolation for Environmental Health Risk Assessment

Low-dose extrapolation model selection for evaluating the health effects of environmental pollutants is a key component of the risk assessment process. At a workshop held in Baltimore, Maryland, on 23–24 April 2007, sponsored by U.S. Environmental Protection Agency and Johns Hopkins Risk Sciences and Public Policy Institute, a multidisciplinary group of experts reviewed the state of the science regarding low-dose extrapolation modeling and its application in environmental health risk assessments. Participants identified discussion topics based on a literature review, which included examples for which human responses to ambient exposures have been extensively characterized for cancer and/or noncancer outcomes. Topics included the need for formalized approaches and criteria to assess the evidence for mode of action (MOA), the use of human versus animal data, the use of MOA information in biologically based models, and the implications of interindividual variability, background disease processes, and background exposures in threshold versus nonthreshold model choice. Participants recommended approaches that differ from current practice for extrapolating high-dose animal data to low-dose human exposures, including categorical approaches for integrating information on MOA, statistical approaches such as model averaging, and inference-based models that explicitly consider uncertainty and interindividual variability

Molecular Identification, DNA Barcoding and Determination of Genetic Relationship of Killifish (Aplocheilus spp.) Present in Aththanagalu Oya, Sri Lanka

Accurate identification of species is of paramount importance in conserving fish diversity due to practical limitations of recognizing closely related species based on morphological features. DNA barcoding is a rapid and reliable molecular tool widely used to identify organisms at species level. The present study was conducted to identify and determine genetic relationships of the Aplocheilus spp. present in Aththanagalu river basin, Sri Lanka using molecular tools. From 68 sampling sites along the river, Aplochielus spp. were collected and identified using morphological characteristics. Meristic characters of each fish sample were subjected to truss analysis by preparing principal component analysis (PCA) using PRIMER 5 software. Genomic DNA extracted from fresh muscle tissues of ten samples of killifish was subjected PCR targeting the COXI gene in mitochondrial genome using a universal primer pair, FishF1/FishR1. Ten PCR amplicons of the expected size (approximately 650 bp) were subjected to DNA sequencing. Eight successfully-sequenced samples were subjected to DNA homology search using BLAST, NCBI and phylogenetic analysis using Geneious 7.1.3 and MEGA 6 software. According to the results of morphological characteristics, 180 A. dayi and 143 A. parvus species were identified. Truss analysis based on morphological characteristics did not differentiate A. dayi and A. Parvus into separate clusters. Based on DNA homology search results, two A. dayi samples identified morphologically were highly homologous to A. werneri (with 83-94% identity and 75-77% query cover). Two other A. dayi samples and four A. parvus samples, identified morphologically were best matched with A. blockii voucher sample (with 90-97% identity and 80-98% query cover). By phylogenetic analysis, the two A. dayi samples which showed the highest DNA homology with A. werneri formed a separate cluster but indicated a closer relationship with A. werneri. The rest of the A. dayi and A. parvus samples which were highly homologous with A. blockii were clustered together and formed a monophyletic clade but showed a closer relationship to A. blockii. The findings revealed the ability of identifying A. parvus and A. blockii which is difficult to be differentiated by morphological characters by DNA barcoding targeting the COXI gene. Exact identification of A. dayi is not possible due to unavailability of sequence information of A. dayi. Closer genetic relationships of some A. dayi with A. werneri indicate possible hybrids due to interbreeding.Keywords: DNA sequencing, Cytochrome c oxidase I gene, Phylogenetic tree, Polymerase chain reaction, Species identificatio

Traffic-related pollution and asthma prevalence in children. Quantification of associations with nitrogen dioxide.

Ambient nitrogen dioxide is a widely available measure of traffic-related air pollution and is inconsistently associated with the prevalence of asthma symptoms in children. The use of this relationship to evaluate the health impact of policies affecting traffic management and traffic emissions is limited by the lack of a concentration-response function based on systematic review and meta-analysis of relevant studies. Using systematic methods, we identified papers containing quantitative estimates for nitrogen dioxide and the 12 month period prevalence of asthma symptoms in children in which the exposure contrast was within-community and dominated by traffic pollution. One estimate was selected from each study according to an a priori algorithm. Odds ratios were standardised to 10 μg/m(3) and summary estimates were obtained using random- and fixed-effects estimates. Eighteen studies were identified. Concentrations of nitrogen dioxide were estimated for the home address (12) and/or school (8) using a range of methods; land use regression (6), study monitors (6), dispersion modelling (4) and interpolation (2). Fourteen studies showed positive associations but only two associations were statistically significant at the 5 % level. There was moderate heterogeneity (I(2) = 32.8 %) and the random-effects estimate for the odds ratio was 1.06 (95 % CI 1.00 to 1.11). There was no evidence of small study bias. Individual studies tended to have only weak positive associations between nitrogen dioxide and asthma prevalence but the summary estimate bordered on statistical significance at the 5 % level. Although small, the potential impact on asthma prevalence could be considerable because of the high level of baseline prevalence in many cities. Whether the association is causal or indicates the effects of a correlated pollutant or other confounders, the estimate obtained by the meta-analysis would be appropriate for estimating impacts of traffic pollution on asthma prevalence

The incentive gap: LULUCF and the Kyoto mechanism before and after Durban

To-date, forest resource-based carbon accounting in land use, land use change and forestry (LULUCF) under the United Nations Framework Convention on Climate Change (UNFCCC), Kyoto Protocol (KP), European Union (EU) and national level emission reduction schemes considers only a fraction of its potential and fails to adequately mobilize the LULUCF sector for the successful stabilization of atmospheric greenhouse gas (GHG) concentrations. Recent modifications at the 2011 COP17 meetings in Durban have partially addressed this basic problem, but leave room for improvement. The presence of an Incentive Gap (IG) continues to justify reform of the LULUCF carbon accounting framework. Frequently neglected in the climate change mitigation and adaptation literature, carbon accounting practices ultimately define the nuts and bolts of what counts and which resources (forest, forest-based or other) are favored and utilized. For Annex I countries in the Kyoto Mechanism, the Incentive Gap under forest management (FM) is significantly large: some 75% or more of potential forestry-based carbon sequestration is not effectively incentivized or mobilized for climate change mitigation and adaptation (Ellison etal. 2011a). In this paper, we expand our analysis of the Incentive Gap to incorporate the changes agreed in Durban and encompass both a wider set of countries and a larger set of omitted carbon pools. For Annex I countries, based on the first 2years of experience in the first Commitment Period (CP1) we estimate the IG in FM at approximately 88%. Though significantly reduced in CP2, the IG remains a problem. Thus our measure of missed opportunities under the Kyoto and UNFCCC framework - despite the changes in Durban - remains important. With the exception perhaps of increased energy efficiency, few sinks or sources of reduced emissions can be mobilized as effectively and efficiently as forests. Thus, we wonder at the sheer magnitude of this underutilized resource