Risk-based Guidelines Research Articles

Probabilistic Approach to Deriving Risk-Based Exposure Guidelines: Application to Extremely Low Frequency Magnetic Fields

Guidelines for environmental and occupational exposures are based upon risk estimates that consider many variables, each typically defined as a single point value. This paper recommends that probabilistic methods, which characterise uncertainty in the form of distributions, be used instead. The advantages of a probabilistic approach include the maximal use of existing data; identification of the likelihood of effects at various exposure levels; improved accuracy and confidence in risk estimates; avoidance of inflated risk estimates produced by compounding the average or 'worst case' values; increased ability to separate risk analysis from risk management judgements; and improved risk communication and research focus. As an example, the rationale and justification for deriving magnetic field guidelines using the probabilistic approach are described. Existing occupational guidelines for exposures to extremely-low-frequency (ELF) fields are designed to prevent short-term effects of induced electric fields and currents on excitable tissues, e.g., the heart and nervous system. However, existing ELF guidelines are based on limited and selected data which are summarised only as single point estimates. Another source of uncertainty in the guidelines derives from the assumption that induced currents of 10 mA.m -2 are without effect. The degree of protection afforded by these guidelines is therefore not known. Finally, standard reference dose methods for deriving acceptable exposure levels from experimentally determined NOAEL thresholds have not been followed. The use of probabilistic methods to update these guidelines would address these issues and greatly improve the scientific basis for these guidelines.

How Has the Basle Accord Affected Bank Portfolios?

This paper investigates the extent to which the risk-based capital standards, which took effect in 1989, have affected commercial bank portfolios. The new standards give banks an incentive to substitute away from loans, which have a high risk weight, into less risky assets such as government securities. Time-series macro data is used to determine whether the risk-based guidelines have caused unusually large portfolio changes on bank balance sheets. Bank-level data are used to determine how successful banks have been in meeting their capital requirements and to explore the relationship between capital ratios and subsequent portfolio shifts. The principal conclusion of this paper is that both the timing of bank portfolio shifts and the strong relationship in the bank-level data between low risk-based capital ratios and portfolio adjustment (controlling for the ratio of bad loans to assets) are consistent with the view that the risk-based capital standards have significantly affected bank portfolios. During the 1990 and 1991 period, banks were quite successful in raising their capital ratios in order to meet the risk-based capital requirements. However, in order to raise capital ratios, banks decreased lending, particularly to businesses. The evidence suggests that commercial banks have reduced their loans by approximately $150 billion because of the risk-based capital guidelines. To the extent that a "credit crunch" has weakened economic activity since 1990, Basle-induced declines in lending may have been a major cause of this credit crunch. J. Japan. Int. Econ., December 1993, 7(4), pp. 408–440. Department of Economics, Harvard University, Cambridge, Massachusetts 02138.

Diagnostic Imaging in Ophthalmology

<b>PURPOSE</b> We wanted to compare the risk of death from coronary heart disease (CHD) for patients of low socioeconomic status, measured by educational level, with established risk factors. <b>METHODS</b> We undertook a prospective cohort study. Participants included a representative sample of 6,479 adults aged 25 to 74 years in the United States who were free of CHD at enrollment in the first National Health and Nutrition Examination Survey (NHANES I). <b>RESULTS</b> Baseline measures included years of education, age, sex, systolic blood pressure, diabetes, total cholesterol level, and smoking. Outcome was death within 10 years from CHD. The relative risk (RR) associated with less than 12 years of education compared with more than 12 years (RR 1.5; 95% confidence interval [CI], 1.2–1.8) was comparable to being male (RR 1.4; 95% CI, 1.2–1.6), smoking (RR 1.4; 95% CI, 1.1–1.6), having a total cholesterol level of greater than 280 mg/dL (RR 1.6; 95% CI, 0.9–2.7), and systolic blood pressure of 130–139 mm Hg (RR 1.6; 95% CI, 1.0–2.4). Findings were comparable for estimates of absolute risk. <b>CONCLUSIONS</b> Low educational level is associated with comparable risk as established risk factors for CHD mortality. Incorporation of educational level into risk-based guidelines for treatment could potentially reduce socioeconomic disparities in CHD by lowering thresholds for treatment.