| OCR Text |
Show efficiency of principle organic haza r dous consti tu e nt s (POHCs ) while operating under combustion upset co ndi t io ns a s e videnced by high CO and smoke episodes . Although the l i mit ed ava i l able da ta indicate that PIC emission s do not pose s ign i fi cant ris k , t he data are incomplete . Giv e n that w ~ cannot prove the nesat ive (i . e ., that PICs do not pose significant risk), we believe it is prudent t o con tr ol CO levels as an important step to reduce the potenti al ri sk. Me tals and HCl Controls. Metals and hydrogen chloride (HCl) emissions from boilers and industrial furnaces would be controlled by risk-based emission limit s . The emission limits were backcalculated from ambient levels considered to pose acceptable health r i sK using dispersion coeficients for reasonable, worstcase dispersion scenarios. Metals emissions from incinerators are controlled indirectly by a particulate standard and HCl emissions are controlled by a technology-based 99% removal efficiency standard (when HCI emiss i ons exceed 4 Ibs/hr). Exemptions and Waivers. A number of exemptions and waivers were proposed, including a risk-based exemption for burners ef s.all qu~ities of hazardous waste. The Agency determined that the health risk from ~urning these small quantities absent regulatory control and under poor combustion conditions would be acceptable (i.e., the aggregate increased lifetime cancer risk to the most exposed individual would not exceed I in 100,000, and the most exposed individual would not be exposed to ambient levels of noncarcinogens exceeding their threshold level). In addition, the trial burn for boilers operating under special operating conditions would be automatically waived (although the co limits would apply). Those special conditions include: o Hazardous waste firing rate less than 50% o Hazardous waste heating value greater than 8000 Btu/lb EPA received approximately 175 comments on the proposed rule. A number of commenters argued that the CO limits were much too stringent. Boiler operators pointed out that boilers operate at maximum thermal efficiency (i.e., lowest fuel cost per unit of energy generated) when burning fossil fuels at CO levels of 200 to 350 ppm. Cement kiln operators noted that cement kilns typically operate at CO levels of 200 to 1000 ppm when burning fossil fuels. Commenters were also concerned that the Agency proposed to control metals and HCl emissions solely with risk-based controls. Commenters argued that risk-based standards allow dispersion of emissions in lieu of emissions cleaning. Thus, the aggregate population risk may not be reduced significantly. In addition, they noted the uncertainties inherent with risk assessments (e.g., limited healt h effects data, uncertainties associated with dispersion ~o a el in g ) , and argued that risk assessment should be used only to back up t echnology-based standards. For example, some commenters argued t hat a part i culate standard should be applied to provide bas ic con t ro l for metals emissions. -2- |
