Friday, August 19, 2011

Risk Assessment and Air Pollution Epidemiology

Improving the Linkages between Air Pollution Epidemiology and Quantitative Risk Assessment (23 page pdf, Fann N, Bell ML, Walker K, Hubbell B, Environmental Health Perspectives, Aug. 4, 2011)

Today’s focus is on the link between the assessment of health risk on the one hand and the analysis of causes and effect of health impacts through epidemiology- and how one can complement the other. The review article considers a number of aspects: estimated effects, air quality, population and health data.

Key Quotes:

“The extent to which risk assessors can properly specify a quantitative risk assessment and characterize key sources of uncertainty depends in part on the availability, and clarity, of data and assumptions in the epidemiological studies”

“the role of air pollution epidemiology in supporting quantitative risk assessments—principally by providing the risk coefficients that relate air quality changes to the probability of a variety of adverse health outcomes, including premature death, hospital visits and acute respiratory symptoms among many others”

-policy questions:
  • “the total public health burden associated with exposure to air quality levels above some background level in terms of the number of excess cases of premature death or illness?”
  • “the impact on human health of incremental changes in air quality due to a proposed policy?”
Key attributes of epidemiological studies relevant to risk assessment:
  • Effect estimates - the U.S. EPA recently evaluated the long-term PM mortality literature to consider the empirical basis for a threshold in the concentration-response relationship. EPA found useful the graphics depicting the concentration-response curve and 95th percentile confidence interval over the range of the observed data
  • Air Quality - Risk assessments rarely have the opportunity to rely on risk coefficients from epidemiological studies in which the temporal and spatial variability in air quality is fully consistent with that of the policy scenarios being analyzed.
  • Population - risk assessments tend to estimate the incidence of adverse health outcomes among a population whose attributes are sometimes very different from the study population in ways that may alter the outcome of the risk assessment.
  • Health Data - consider which endpoints to quantify, how to match key characteristics of the endpoints across populations, and how and whether to pool evidence across studies.
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