Letters
About hazardous waste incineration Dear Editor: "Managing the Health Impacts of Waste Incineration" {Environ. Sci. Technol. 2000, 34 (17), 380A-387A), as it relates to hazardous waste (HW) incineration, contains errors and omissions. The article states that emissions can increase significantly during startup/shutdown, and there is concern that Maximum Achievable Control Technology (MACT) standards for HW combustors do not reduce releases during these periods. The Resource Conservation and Recovery Act (RCRA) and MACT prohibit HW introduction until incinerators are at authorized operating conditions, and requirements for automatic waste feed cutoff of HW-derived fuels prevent their use during upsets. Test data from EPA's research facility in Arkansas and Waste Technologies Industries, among others, do not support the assertion that emissions significantly increase during upsets. Therefore, startups, shutdown, and upsets do not significantly increase emissions from HW incinerators. Contrary to article statements, HW incinerator emissions data are available. EPA began an intensive effort in 1996 to require emissions testing of all HW combustors in Texas and Louisiana (later in other states). Most HW combustors in Texas and Louisiana have now been tested, and the results are publicly available (through record searches). Forty to 50 data sets now exist. Focus Environmental (Knoxville, TN) is developing a database using these emissions, which will shed light on a number of issues and concerns regarding HW combustion. The statement that "virtually all emissions data used to evaluate incinerator health impacts are derived from routine operations" is incorrect. EPA requires that emission rates derived from routine opera-
tions be adjusted to account for upsets when used to evaluate health impacts. Additionally, because of the extra layer of permitting constraints associated with the use of emissions data collected under routine operating conditions, many HW combustion risk assessments are performed using data generated under trial burn (worst-case) conditions. Concerning worker exposures, RCRA/MACT require that incinerators be completely enclosed or operated at a slight vacuum. Residuals from air pollution control devices are typically discharged through sealed ducts to sealed transport containers. Personnel entering air pollution control devices are equipped with personal protective equipment (PPE), including respirators and/or supplied air, as appropriate. Worker exposures are regulated under the Occupational Safety and Health Act (OSHA), which requires appropriate PPE and related plant safety approaches. MACT does not apply to in-plant health and safety issues. The article concludes by stating that uncertainty in the current framework for assessing health impacts derives from factors that are excluded and from a lack of scientific data. Another, potentially greater, source of uncertainty is EPA's continued reliance on unrealistic assumptions for risk assessments. Many believe that the current approach for estimating risk exaggerates the health impacts from combustion of HW, leading to poorly informed permitting and treatment technology decisions. Clearly, this practice has significant scientific and policy implications for attributing health impacts to incinerators. LUCY FRAISER, Ph.D, DABT Senior Toxicologist MFG, Inc., Austin, TX WILLIAM SCHOFIELD, P.E., Ph.D, Senior Consultant Focus Environmental, Knoxville, TN
4 9 8 A • DECEMBER 1, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
More concerns about incineration Dear Editor: I was disappointed to read the feature article "Managing Health Impacts ..." In actual fact, the consequences of burning wastes, given the extremely high effectiveness of the emission controls that must be used today, are extremely low and inconsequential. In the past 10 years, tremendous progress has been made, with 99.99 to 99.999% control or removal efficiencies of the toxics. To read the article, nobody would know this. FLOYD HASSELRIIS, P.E., DEE, Ph.D. Past Chair, ASME Research Committee on Industrial and Municipal Wastes, Emeritus
Authors' response Dear Editor: We thank Drs. Fraiser, Schofield, and Hasselriis for taking the time to comment on our paper. One of the goals of a feature article is to stimulate discussion, and we welcome the opportunity to hear and respond to alternate views. Drs. Fraiser and Schofield's letter focuses on issues relating only to hazardous waste (HW) incinerators, although our article focuses on municipal and medical incinerators as well. They raise five issues that we believe relate more to alternate interpretations of what we presented rather than any errors or omissions. Listed below are the issues raised in this letter along with our responses. (1) The article states that emissions can increase significantly during startup/shutdown, and this leads to concerns that MACT standards for HW combustors do not reduce releases during these periods. Our article made the point that emissions increase significandy during startup, shut down, and other transient and off-normal operations, and Drs. Fraiser and Schofield do not appear to be contesting this issue. However, we did not state or imply that
