Jane V. Hall

Concepts and measures of natural resource scarcity with a summary of recent trends

A general model of resource scarcity is presented from which previous models can be derived as special cases. Previous models of scarcity are compared and contrasted, refining the concept of scarcity and leading to a resolution of current disputes over the appropriate measure of scarcity. An update of the original work done by Barnett and Morse is summarized, leading to reconsideration of their original conclusions. It is found that energy and forest products experienced increasing scarcity during the 1970s.

Ambient Ozone Concentrations Cause Increased Hospitalizations for Asthma in Children : An 18-Year Study in Southern California

Background Asthma is the most important chronic disease of childhood. The U.S. Environmental Protection Agency has concluded that children with asthma continue to be susceptible to ozone-associated adverse effects on their disease. Objectives This study was designed to evaluate time trends in associations between declining warm-season O3 concentrations and hospitalization for asthma in children. Methods We undertook an ecologic study of hospital discharges for asthma during the high O3 seasons in California’s South Coast Air Basin (SoCAB) in children who ranged in age from birth to 19 years from 1983 to 2000. We used standard association and causal statistical analysis methods. Hospital discharge data were obtained from the State of California; air pollution data were obtained from the California Air Resources Board, and demographic data from the 1980, 1990, and 2000 U.S. Census. SoCAB was divided into 195 spatial grids, and quarterly average O3, sulfurdioxide, particulate matter with aerodynamic diameter ≤ 10 μm, nitrogen dioxide, and carbon monoxide were assigned to each unit for 3-month periods along with demographic variables. Results O3 was the only pollutant associated with increased hospital admissions over the study period. Inclusion of a variety of demographic and weather variables accounted for all of the non-O3 temporal changes in hospitalizations. We found a time-independent, constant effect of ambient levels of O3 and quarterly hospital discharge rates for asthma. We estimate that the average effect of a 10-ppb mean increase in any given mean quarterly 1-hr maximum O3 over the 18-year median of 87.7 ppb was a 4.6% increase in the same quarterly outcome. Conclusions Our data indicate that at current levels of O3 experienced in Southern California, O3 contributes to an increased risk of hospitalization for children with asthma.

ASSESSING HEALTH EFFECTS OF AIR POLLUTION

Abstract Exposure to elevated concentrations of ambient air pollutants causes adverse human health effects. Two modes or methods of study are generally relied on to quantify the relationships between pollutants and specific effects. These are: human clinical experiments and epidemiological (or community exposure) studies. (Animal toxicological studies can be used to indicate the existence of an effect, but not the rate of the effect in humans.) Each method has limitations as a basis for quantifying the level of adverse effects anticipated in a given human population as a result of exposure. Consequently, care must be taken in deciding which studies are appropriate for assessment of health impacts in a population. Some limitations are inherent in the method. Epidemiological studies, for example, depend on adequate community monitoring and the ability to associate a cohort with ambient data. Clinical studies often do not represent the complex mix of pollutants in the atmosphere. Consequently, construction of dose/exposure-response functions is challenging. Another common complication in quantifying expected health impacts of a pollutant mix is lack of adequate ambient monitoring data coupled with little or no knowledge of a populations time and activity profiles. This paper summarizes the difficulties inherent in constructing estimates of health effects in populationsliving in densely populated and polluted areas and suggests approaches to making initial limited estimates. An example of the level of effort required to conduct a sophisticated study, using relatively rich databases, is given based on work done in the Southern California region.

Ambient Ozone Concentrations and Cardiac Mortality in Southern California 1983–2000: Application of a New Marginal Structural Model Approach

The authors evaluated the association between ambient ozone levels and cardiac mortality in Californias South Coast Air Basin during the period 1983-2000 and compared inferences from several types of marginal structural model (MSM) estimators. The authors undertook an ecologic study during the high-ozone seasons among persons over age 55 years. In contrast to conditional regression analysis and MSMs based on G-computation and simple inverse probability-of-treatment weighting (IPTW), an MSM that protected against violation of the experimental treatment assignment (ETA) assumption and considered only those areas that could have experienced both high and low ozone concentrations during 1983-2000 found no consistent evidence that reductions in quarterly 1-hour maximum ozone concentrations from levels above any of the regulatory standards to levels below those standards led to decreases in cardiac mortality; however, it did find evidence of decreases related to a decrease in 8-hour maximum concentrations. The G-computation estimator and simple IPTW estimators were biased because of serious violation of the ETA assumption. These analyses highlight the importance of nonviolation of the ETA assumption for valid inference and the failure of conditional regression to provide marginal estimates in the presence of interactions. Noncausal models also consistently inferred larger associations, which may have been due to bias violation of the ETA assumption on which these models rely.

Air pollution impacts from demand-side management

Air-polluting emission rates and energy-efficiency ratings vary widely among power plants, depending on location, age and whether the power plant is repowered. Traditional regulations require installation of specified emission control equipment that varies among power plants. These regulations do not specify that utilities first dispatch the cleanest power plants as demand varies from peak to off-peak periods. This empirical analysis shows, for 2 years out of 20, that demand-side management (DSM) programs increase air pollution. One reason for this result is that regulations require installation of specific emission-control technology but do not provide the incentive to take actual emissions or their air quality impacts into account when operating the system. For certain types of air pollutants and in some regions, regulatory programs now include markets for tradable emission credits. Such programs may alter this incentive.

Environmental Resource Scarcity and Conflict

All humans depend on direct and market-mediated access to a diverse array of environmental resources for basic survival and quality of life. Consequently, increased demand, reduced supply, or deterioration of a resource threatens access and can therefore also threaten individuals and groups. Security extends beyond maintaining the status quo or the power of the state to protection of the “physical, social, and economic well-being” of human populations (Homer-Dixon 1991). Security in this sense is threatened when the institutional and economic resources to ameliorate the impact of scarcity are unavailable or extremely costly. Violence is a potential outcome when groups compete to ensure their security.

Estimating environmental health benefits: implications for social decision making

Discusses the measurement and conceptual difficulties of assessing the benefits of environmental improvements in monetary terms, in the context of a study undertaken to evaluate the health‐related benefits of improved air quality in a large, diverse urban population. Describes an interdisciplinary approach methodology to assess health benefits and uses the results from a study based on that approach to illustrate the practical and conceptual difficulties of comprehensively assessing such benefits. Ends with a discussion of the implications of these difficulties for using benefit‐cost analysis in deciding public policy for health‐related environmental improvements, particularly in the case of complex atmospheric changes.

Energy in the unit cost index to measure scarcity

We show that the unit cost index concept, when generalized to include energy as an input, has a sound theoretical basis for industries other than non-renewable resource industries. Average cost trends reflect increasing scarcity of non-renewable energy inputs. We present a numerical example of the computation of a generalized unit cost index, which requires construction of a measure of capital and involves prior computations of embedded and direct energy in commodities. We briefly discuss weaknesses and issues relevant to the use of the unit cost index as an indicator of increasing scarcity.

Potential air quality benefits of methanol as a vehicle fuel

Air pollution regulation in industrial cities limits economic growth. Cleaner vehicles can reduce this effect by reducing pollution. The air quality and consequent economic benefits of methanol are assessed. Air pollution is a pervasive by-product of industrial development. Substitution of cleaner fuels for the current generation of fossil fuels can reduce the need for and economic cost of traditional add-on pollution controls. I will assess the potential of methanol to reduce vehicle emissions, and consequently to reduce regulatory pressure on industry and economic growth. The impact of releasing capital investment from pollution control to other productive uses and preserving existing manufacturing jobs are two of the economic benefits addressed.