Source attribution of health benefits from air pollution abatement in Canada and the United States: An adjoint sensitivity analysis

Background: Decision making regarding air pollution can be better informed if air quality impacts are traced back to individual emission sources. Adjoint or backward sensitivity analysis is a modeling tool that can achieve this goal by allowing for quantification of how emissions from sources in different locations influence human health metrics. Objectives: We attributed short-term mortality (valuated as an overall "health benefit") in Canada and the United States to anthropogenic nitrogen oxides (NOx) and volatile organic compound (VOC) emissions across North America. Methods: We integrated epidemiological data derived from Canadian and U.S. time-series studies with the adjoint of an air quality model and also estimated influences of anthropogenic emissions at each location on nationwide health benefits. Results: We found significant spatiotemporal variability in estimated health benefit influences of NOx and VOC emission reductions on Canada and U.S. mortality. The largest estimated influences on Canada (up to $250,000/day) were from emissions originating in the Quebec City-Windsor Corridor, where population centers are concentrated. Estimated influences on the United States tend to be widespread and more substantial owing to both larger emissions and larger populations. The health benefit influences calculated using 24-hr average ozone (O3) concentrations are lower in magnitude than estimates calculated using daily 1-hr maximum O3 concentrations. Conclusions: Source specificity of the adjoint approach provides valuable information for guiding air quality decision making. Adjoint results suggest that the health benefits of reducing NOx and VOC emissions are substantial and highly variable across North America

Health benefits of reducing NO x emissions in the presence of epidemiological and atmospheric nonlinearities

Recent epidemiological evidence suggests that the logarithm of concentration is a better predictor of mortality risk from long-term exposure to ambient PM2.5 and NO2 than concentration itself. A log-concentration-response function (CRF) predicts a heightened excess risk per unit concentration at low levels of exposure that further increases as the air becomes less polluted. Using an adjoint air quality model, we estimate the public health benefits of reducing NO x emissions, on a per-ton and source-by-source basis. Our estimates of benefits-per-ton assume linear in concentration and log-concentration CRFs for NO2 and a CRF that is linear in concentration for O3. We apply risk coefficients estimated using the Canadian Census Health and Environment Cohort. We find that a log-concentration CRF for NO2 leads almost consistently to larger benefits-per-ton than a linear in concentration CRF (e.g., $500 000 ton-1 compared to$270 000 ton-1 for Ottawa). We observe that concentrations gradually decline due to widespread, progressive emissions abatement, entailing increasing health benefits as a result of (1) a log-concentration CRF for NO2 and (2) the nonlinear response of O3 to NO x emissions. Our results indicate that NO x abatement has the potential to incur substantial and increasing health benefits, by up to five times with 85% emission reductions, for Canada into the future

An evaluation of the efficacy of very high resolution air-quality modelling over the Athabasca oil sands region, Alberta, Canada

We examine the potential benefits of very high resolution for air-quality forecast simulations using a nested system of the Global Environmental Multiscale-Modelling Air-quality and Chemistry chemical transport model. We focus on simulations at 1 and 2.5 km grid-cell spacing for the same time period and domain (the industrial emissions region of the Athabasca oil sands). Standard grid cell to observation station pair analyses show no benefit to the higher-resolution simulation (and a degradation of performance for most metrics using this standard form of evaluation). However, when the evaluation methodology is modified, to include a search over equivalent representative regions surrounding the observation locations for the closest fit to the observations, the model simulation with the smaller grid-cell size had the better per

Adjoint estimation of ozone climate penalties

An adjoint of a regional chemical transport model is used to calculate location-specific temperature influences (climate penalties) on two policy-relevant ozone metrics: concentrations in polluted regions (>65 ppb) and short-term mortality in Canada and the U.S. Temperature influences through changes in chemical reaction rates, atmospheric moisture content, and biogenic emissions exhibit significant spatial variability. In particular, high-NO x, polluted regions are prominently distinguished by substantial climate penalties (up to 6.2 ppb/K in major urban areas) as a result of large temperature influences through increased biogenic emissions and nonnegative water vapor sensitivities. Temperature influences on ozone mortality, when integrated across the domain, result in 369 excess deaths/K in Canada and the U.S. over a summer season - an impact comparable to a 5% change in anthropogenic NOx emissions. As such, we suggest that NOx control can be also regarded as a climate change adaptation strategy with regard to ozone air quality. Key Points Ozone climate penalties in North America show great spatial variability High-NOx regions are among locations with the largest climate penalties NOx control can be seen as a climate change adap

Following the genes: a framework for animal modeling of psychiatric disorders

The number of individual cases of psychiatric disorders that can be ascribed to identified, rare, single mutations is increasing with great rapidity. Such mutations can be recapitulated in mice to generate animal models with direct etiological validity. Defining the underlying pathogenic mechanisms will require an experimental and theoretical framework to make the links from mutation to altered behavior in an animal or psychopathology in a human. Here, we discuss key elements of such a framework, including cell type-based phenotyping, developmental trajectories, linking circuit properties at micro and macro scales and definition of neurobiological phenotypes that are directly translatable to humans

The Canadian Urban Environmental Health Research Consortium - A protocol for building a national environmental exposure data platform for integrated analyses of urban form and health

Background: Multiple external environmental exposures related to residential location and urban form including, air pollutants, noise, greenness, and walkability have been linked to health impacts or benefits. The Canadian Urban Environmental Health Research Consortium (CANUE) was established to facilitate the linkage of extensive geospatial exposure data to existing Canadian cohorts and administrative health data holdings. We hypothesize that this linkage will enable investigators to test a variety of their own hypotheses related to the interdependent associations of built environment features with diverse health outcomes encompassed by the cohorts and administrative data. Methods: We developed a protocol for compiling measures of built environment features that quantify exposure; vary spatially on the urban and suburban scale; and can be modified through changes in policy or individual behaviour to benefit health. These measures fall into six domains: air quality, noise, greenness, weather/climate, and transportation and neighbourhood factors; and will be indexed to six-digit postal codes to facilitate merging with health databases. Initial efforts focus on existing data and include estimates of air pollutants, greenness, temperature extremes, and neighbourhood walkability and socioeconomic characteristics. Key gaps will be addressed for noise exposure, with a new national model being developed, and for transportation-related exposures, with detailed estimates of truck volumes and diesel emissions now underway in selected cities. Improvements to existing exposure estimates are planned, primarily by increasing temporal and/or spatial resolution given new satellite-based sensors and more detailed national air quality modelling. Novel metrics are also planned for walkability and food environments, green space access and function and life-long climate-related exposures based on local climate zones. Critical challenges exist, for example, the quantity and quality of input data to many of the models and metrics has changed over time, making it difficult to develop and validate historical exposures. Discussion: CANUE represents a unique effort to coordinate and leverage substantial research investments and will enable a more focused effort on filling gaps in exposure information, improving the range of exposures quantified, their precision and mechanistic relevance to health. Epidemiological studies may be better able to explore the common theme of urban form and health in an integrated manner, ultimately contributing new knowledge informing policies that enhance healthy urban living

Health benefits of emission controls: A multi-pollutant and multi-health outcome analysis

We create a streamlined approach for estimating the U.S. public health benefits of emission control, on a per-ton basis. We do so by incorporating epidemiological and economic valuation data into the adjoint of an atmospheric chemical transport model. We estimate benefits-per-ton of emission control for chronic mortality and acute morbidity endpoints. Our results indicate that benefits-per-ton of NOx reduction are highly variable from source-to-source or location-to-location. We find that mortality due to long-term exposure comprises a significant portion of the total benefits of NOx control for ozone air quality management

Development of an approximate method for advection of sensitivity fields

Although advection equation is linear in time and space, positive definite and mass conservative advection schemes in chemical transport models (CTMs) behave nonlinearly mostly due to discontinuous (conditional) operations in discretization. A new approach is developed to indirectly simulate the advection process in CTMs. Instead of integrating the continuity equation directly for various species, advection equations for various pollutants are solved in relations to advected air densities. Our approach relies on the run-time estimation of the Jacobian of the advection operator, and can be based on the native advection algorithm in any CTM. The estimated transport Jacobian for air densities are then applied to other species with corrections that would ensure consistency with the underlying scheme. Since our proposed method is truly linear in species concentration, it is not suspect to complications associated with advecting sensitivities as experienced with nonlinear advection schemes. We implement our advection method in CMAQ 5.0 using its native Piecewise Parabolic Method (PPM) advetion scheme. Our preliminary results show good consistency with the PPM scheme, and potential for truly linear advection of sensitivity fields

Source attribution of attainment and exposure-based ozone metrics in North America

We use adjoint sensitivity analysis to examine the responses of a regulatory ozone attainment metric and adverse ozone health effects to location-specific reductions in anthropogenic NOx emissions. We find spatially heterogeneous responses among both attainment- and exposure-based metrics. Emission reductions in the western U.S. exert the most influence on attainment probability-weighted extreme concentrations (PWCs), while emission reductions in proximity to population centres in the eastern U.S. are most beneficial for reducing short-term ozone-related mortality