Document 65pN0kY9jpDK3JV43pZYjYwEg

LIA15121 Hey 9, 1973 ' Office of Research and Envelopment Subject^ Assuring that mobile soin-ce controls do not adversely ffoct public health: The oxidation catalytic converter issue From: Assistant Administrator for Research aad Development To: Assistant Administrator for Air and Hater Prograns Assistant Administrator for Planning and Maaajamoat I My views of the technical asnects of this issue address the basic scientific problem. the available scientific facts and regulatory problem*. 1. Raslc scientific problem: Sirply put. EPA nust assure that environnentaT-controls do not adversely effect oifclic health or environrental anility. That is to say, that on balance our actions produce a let health benefit fop the Nation. t 2. Scientific facts: The use of catalytic converter* to control carbon noncxide an31^3rocarbon emissions will involve exposing. the general nopilaticn to low levels of the new pollutants ulatinus and palladium ccnpounis- and to increased levels of none faailiar pollu tants, sulfuric acid and suspended particulate sulfate*. Exposures to pi atIran conrewuls arc likely to range frcn 1/1 Of) to 1/13 of the threshold limit value for platimn salts. Platinum ccrooinds can be exrected to aggravate asthma and pre existing cardiorespiratory disease as could increased level* of v suspended sulfate and acid aerosols. It is conceivable that the interactions of those pollutants night prove additive or synergistic. Platinum and palladius conpomds nay also act as co-carcinogens or career oTocoters. Platinui coaxxnds have been used experimentally i' s> VMMWfWigjlg* 2 as *nti-cajvrcr agents and it has been observed that most enti-career cent* also have some sbility to help Induce emetrs. We cannot assure that currently projected respiratory exposure* to low level* of piatinti* *ccorrupted by particulate polycyclic organic Better will not increase tho risk for respiratory cancer. Other adverse health Consequences are possible. Suspended particulate sulfate and add aerosol emissions from rotor vehicles equipped with oxidation catalysts are increased significantly aboVa similar emissions from vehicles not equipped with these cctalysts, Tho bevt current average estimate of this probable increase is about .05 gm/mlle measured as sulfate with a ranve of .02 ps/mile to 0.10/wll*. Important scairces of variability in both the amount ecitcod and the resulting ambient concentrations include methodology for soreling end measurement, sulfur content of gasoline, type of catalyst, ego of catalyst, oocrating conditions, meterolopical disporsiou factors, rate of conversion of sulfur dioxide to acid aerosols and suspended sulfates in die etoosp.bere and the proportion of vehicle* which ore equipped with catalytic converters. Rased on Prussian atmospheric dispersion models tot highways, we estimate that peak hourly exposures to sulfuric add and particulate sulfates under normal dispersion conditions would be increased G ty 2.4 to 3.S ug/t nt j q ncters and .8-1.1 at 100 meters from an arterial highwry. This assumes 25* of vehicle dies involve catalyst* equipped vehicles. Under worst ctse ceterelogical conditions, those 'base case" exposures would increase by en order of magnitude, i.e., 24 to 55 ug/nl at 10 raters and 8 to 11 up/a5 at 100 jacters. For pedestrians ir. urban street canyons the 'base case" exposure would incr_rse by a f?ctor of 3 to S, i.e., 7.2 to 17.5 up/m3 at 10 meter* Vaia'i,** to 5.5 upjn5 at 100 meters. Urban street canyons levels would St lurther increased under the wost adverse meterelogical conditions. Oriwrs and passengers in these areas would also be exposed for short periods to high levels of sulfuric acid-suspended sulfate one meter from reading that ranged from 3.1 to 4.6 ug/p#3 as a base case to 31 to t^/m5- Since fine vcrtialate lead eedssions from current vehicle population averages a.'&ind ,07 gm/udle and ranges from .05 re to .10 pn/mlie, one aright also use observed lead levels as an indicator for levels of acid aerosol* and suspended sulfate*. Level* of lead I .* *1 4 alongside freeways and In urban street canyons should be dividod by four to simulato ft 2S5 contribution by catalyst equipped rotor vchldss. hben this is dono throe hour levels of 4.S tc 9.S ug/a3 alongside, freeways might be expected on an average day. In a downtown area, levels of 2.4 to 6.0 ug/s3 would be predicted. i^rojectod sulfate-add aerosol exposures using this swthod indicate exposures alongside tho freeway which overlap but ore senowhat higher trust those predicted for the edge of the freeway by the dispersion model. Cn the other band, tho "load projection" estimate for downtown exposures Is somewhat laser than the dispersion model estimate. In general, the degree of agreement strengthens ay concert about increases in sulfuric addsulfate exposures. Existing health effects information and air monitoring data on adbient levels of suspended sulfates and sulfuric acid aerosols indicate that these pollutants are present at levels that adversely effect public health. Expensive sulfuric dioxide controls involving switching to low sulfur fuels and effluent controls are needed to achieve the primary aahient air quality standard. Such controls in larpe eastern cities have reduced suspended sulfate lewis by about one-third, a reduction of 9 to 10 u /q 3 in tho annual average. Los Angeles Hasin levels fc*ve visa been reduced by about one-third (S ur/**3) as an annual average. The projected roadside and street canyon incrcnents in the current average sulfate level in Los Angeles CIO ug/ol) evd in large midwestan * or eastern cities (12-20 ug/nd) wxild be substantial, For example, tho "usual** peak hourly roadside (4.0 ug/m3) and street canyon (6.5 incrcccnta `added to the expected daily freouency distribution for sulfate levels in downtown Los Angeles would rean that 90 to 1004, instead of 501 of days would exceed our best Judgment estimates for tho threshold for adverse effects on health. Delaying use of converters for one year will not greatly effect projected reductions in ambient levels of carbon mooexide and photochemical oxidants/ In fact, the differences are not likely to *' be detected by existing ambient air monitoring stations. Delaying use of catalytic converters for one year would allow EPA to be in a much Best judgment based on combining tho two different projection methods - dispersion modelling and "lead projection.*' 3 4 i - -mi.J-.rn WW1* *! 7 iiitTiiir * . 1 y i iiy y ".'. iL-,!!' 'i,' r m w w mw w " qawisiy w > fij|^ itiif^ ) a <!W|i^ M i^ ^ f lf w ^ w " ^ w i lJ!* ^ ^,^'11 j"i(^'it7 >firttfSriil'im:'itii'!`'fii'T*i~:`r'''^,JL V*ifili TTrt iV---^ ..ncWit' ,,v'. ] coovcicrs for ono year would allow EPa to be in a much better 1 position to assure that slgnifJ cant sdvorse effect* will net occur. ] Alternatively using vehicle* equipped with oxidation cstMysts for one or two yoars in a limited area of the country could allow a?***cent of tlicso issues in a real world situation prior to general national usage. Hovover, this course nay not be without profound philosophical, legal and regulatory consequences. 3. Retaliatory Problem: Besides the obvious problem of nesting legislatively specnied nobila source emissions standards, four other regulatory problems should be considered: standards for non-regulated emissions frea mobile sources, the requirement that mobile source control systeas not emit new pollutants, the ambient air quality standard for sulfur dioxide and the stationary sourca stands:-^ for sulfuric acid. The Clean Air Act authorizes EPA to sat mobile source omissions standards for exhaust particulates (Section 102a). EPA can maintain its position as a fira regulator and avoid neediest Congressional criticism by stating an Intention to set such stand* ards at the same tino as an official position is taken on tha oxidation catalyst issue. The use of stratified charge engines or rotary enginos will probably cause the Agency to set particulate emissions standards in any cast. EPA mobile source eaissions regulations state that control systeas employed for legislatively regulated pollutant? ^2hall not themselves introduce new/pollutants (Section tS.004b). ohlatirua and palladium compounds are new urban air pollutants. EPA's primary ambient air quality standard for sulfur dioxide would not be scientifically defensible if mobile sourca $ control measures are allowed to increase exposures to suspended ulfates and acid aerosols. Hardly anyone in the scientific Coraunity believes that sulfur dioxide alone is detrimental to human health at ambient levels* However, almost everyone in the scientific community will agree that elevated levels of acid aerosols and fine particulate sulfates ar# harmful to health.' Therefore, allowing substantial Increases in acid aerosols * A few of us believe sulfur dioxide can causa reflex laryngospasm, bronchospasm and decreased resistance to upper respiratory infactions.' ** * I - -v ` : J8W5S WP!Ty jaal>l|i.,wipwrw^**w.^ ^" \ lwwpjiM*.i QilWMMPPMBP J;\ LI A15125 and suspended sulfates vould be viewed bv the scientific cojamunity mas ouch nore likoly to endanger health than a nodest relaxation i?in tho priaary anbient air quality standards and the related now sourco porforaance standards for sulfur dloxido. EPA's stationary source regulatiuns for-sulfuric acid nist control would soon glaringly inconsistent with a aobile source control systea that eaitted significant amounts of sulfuric acid and suspended sulfates. This fact would probably not be overlooked by either industry or public interest groups. 4. Conclusion; If enhancement of air quality rests upon a need to protect_public health, EPA should assure that use of the oxidation catalyst does not produce tho opposite result. Until EPA can do so, catalytic convertera should not be used extensively enough to increase population exposures to acid aerosols, suspended sulfates and noblo BOtals and their coanound*. If this requires that oxidation catalysts not be vtilizod in 197S Botor vehicle aodels, so be it. Environmental controls Bust be based upon sound scientific evidence and be as scientifically defensible as possible. At this tiae, the use of oxidation catalysts is not so baaed. Stanley M. Greenfield a Prepared by: J7Finkles:bb:10/9/73-X52600 4 -a # 1 1WJM. iA'WSaBW -HW."" W.-W dmppr' 0 'V