Comments to CASAC on Comments to CASAC on Draft #2 of the SO 2 Risk - PowerPoint PPT Presentation

Comments to CASAC on Comments to CASAC on Draft #2 of the SO 2 Risk and Exposure Assessment Draft #2 of the SO 2 Risk and Exposure Assessment Public Comments Session Public Comments Session CASAC Meeting CASAC Meeting April 16-17, 2009 April 16-17, 2009 Dr. Anne E. Smith, Ph.D. Vice President Comments prepared on behalf of UARG

A Key Result Reported in REA: # Occurrences >100% sRaw from 5-Minute Exposures by Exposure Range St. Louis, exercising asthmatics Source: REA Draft 2, Figure 9-7(a), p. 275 2

Figure 9-7 (a) -- Replicated in Color & Zoomed In 000’s of Annual Occurrences of > 100% sRaw 180 St. Louis, exercising asthmatics 160 > .5 ppm 140 .45-.5 ppm 120 .4-.45 ppm .35-.4 ppm 100 .30-.35 ppm .25-.30 ppm 80 .2-.25 ppm 60 .15-.2 ppm .1-.15 ppm 40 .05-.1 ppm < .05 ppm 20 0 “As is” Current 99/50 99/100 99/150 99/200 99/250 98/200 AQ Primary Std. 3

Impacts Estimates Are Based on Logistic Dose- Response Curve that Assumes Zero Threshold 100% sRaw response to 5-min exposures Median Percent with ≥ Source: REA Draft 2, Figure 9-2, p. 262 4

Percent of Estimated Impacts (at Current Standard) for Exposures on Different Parts of Dose-Response Curve Over 60% of the impacts at the Current Standard are due to 5-minute exposures Over 60% of the impacts at the Current Standard are due to 5-minute exposures below 0.1 ppm, which is less than half of the lowest observed response level. below 0.1 ppm, which is less than half of the lowest observed response level. Median Percent Responding 17% 32% 29% 14% 8% 5

Percent of Estimated Impacts (under “As Is” AQ) for Exposures on Different Parts of Dose-Response Curve 99.6% of the impacts for “As Is” air quality are due to exposures < 0.1 ppm. 99.6% of the impacts for “As Is” air quality are due to exposures < 0.1 ppm. Median Percent Responding 0% 98.2% 1.4% 0.3% 0.1% 6

Sensitivity of Impacts to Alternative No-Effects Levels St. Louis, exercising asthmatics -- 000’s of Annual Occurrences of > 100% sRaw 180 Estimated effects 160 above 0.2 ppm 140 (lowest level of any 120 detected effect): Reproduced REA Figure 9-7(a) 100 180 80 160 60 140 40 120 20 100 0 “As Is” Current 99/50 99/100 99/150 99/200 99/250 98/200 80 AQ Primary Std. 180 60 160 40 140 20 120 0 “As Is” Current 99/50 99/100 99/150 99/200 99/250 98/200 AQ Primary 100 Estimated effects Std. above 0.4 ppm 80 (lowest level of any 60 ATS-defined 40 “adverse” effect 1/ ): 20 0 “As Is” Current 99/50 99/100 99/150 99/200 99/250 98/200 AQ Primary Std. 1/ ATS defines reversible lung function effects as “adverse” if they are statistically significant and accompanied by symptoms. (“What Constitutes an Adverse Health Effect of Air Pollution?” Am J Respir Crit Care Med, Vol. 161, pp. 665-673.) 7

Comparable Results for Greene Co. Are Buried Deep in Appendix C of the REA Greene Co., exercising asthmatics Over 99% of the impacts are due to Over 99% of the impacts are due to exposures below 0.1 ppm , exposures below 0.1 ppm , for every single alternative standard, for every single alternative standard, including the Current Standard. including the Current Standard. Source: REA Draft 2, Appendix C, Figure 4-5(a), p. 705 8

The Uncertainty Analysis is Incomplete and Erroneous Overestimate Unknown – because more severe asthmatics may be more likely to protect themselves with medication before exercising Missing uncertainty: Effect of medication among mild/moderate asthmatics in daily life Direction of bias: Overestimate Source: REA Draft 2, Table 9-10, p. 279 9