TRJ Environmental

Model Evaluation and Data Validation

Sensitivity of APEX Exposure Estimates to Model Inputs. Ted Johnson has conducted numerous analyses to determine the sensitivity of APEX exposure estimates to various modeling assumptions and input data values. His recent analyses have focused on the APEX algorithms that estimate energy expenditure levels, minute ventilation rates, ozone concentrations in microenvironments, and correlations in day-to-day outdoor activities.

Comparison of APEX Estimates with Personal Monitoring Data. Ted Johnson and Tom Long statistically compared ozone concentrations measured during a recent personal monitoring study in Raleigh, NC, with exposure estimates obtained from APEX for the same conditions.

Evaluation of Ozone Rollback Methods. EPA has historically applied an air quality adjustment procedure (AQAP) to baseline monitoring data to simulate the conditions when a specified air pollution standard is just attained. Ted Johnson and Jim Capel conducted a series of statistical analyses to compare the performance of five AQAP’s when applied to typical ozone data. They applied each AQAP to data sets representing high ozone years at 60 monitoring sites and then compared the adjusted data to data for low ozone years reported by the same sites.

Correction of Ozone Measurements for Known Biases. Ted Johnson assisted in the analysis of ozone data reported by co-located monitors employing ultraviolet (UV) absorption and chemiluminescence measurement methods. Results of these analyses were used to develop a formula for correcting UV data for known biases. Ted Johnson statistically compared the results of APEX exposure analyses that used corrected and uncorrected ozone data to represent ambient (outdoor) concentrations.

EPA Guidelines for Validation of Air Monitoring Data. Ted Johnson coauthored the EPA report “Guidelines for Data Validation” (EPA-600/4-80-030). This report provides guidance in the selection and implementation of data validation techniques which are appropriate to the characteristics of the data, the statistical sophistication of the user, and the computing facilities available.

Quality Assurance Specialty Conference. Ted Johnson served as co-chair of the technical program for the AWMA specialty conference entitled “Quality Assurance in Air Pollution Measurements.” He organized and edited the 850-page conference proceedings.