Activists plan to sue the US EPA over a rare decision to invalidate a final air toxics standard for particulate matter (PM) emissions from cement kilns in favor of a less stringent rule.  The EPA on March 23 issued an administrative stay of its maximum achievable control technology (MACT) standard for new cement kilns that burn hazardous waste, after receiving an industry petition that argued the standard was overly stringent. EPA on the same day issued a proposal for a standard that included less strict controls on PM emissions. 
 
But activists charge that EPA’s original standard was already weaker than necessary. One environmentalist says whenever EPA finalises its revised PM standard, litigation is assured. Environmentalists and industry groups have already filed a lawsuit over other aspects of the stayed final rule. 
 
 "Whatever rule they come out with, we’re going to challenge it," the source says. Any new rule EPA issues will set a weaker standard than the MACT because the agency acknowledges in its decision to stay the rule that it believes the standard was overly stringent, the source says. 
 
 EPA late last year issued a final rule requiring hazardous waste combustors at cement kilns to meet a PM standard of 0.0023 grains/dry standard cubic feet (gr/dscf). The Ash Grove Cement Company and the Cement Kiln Recycling Coalition (CKRC) petitioned EPA to reconsider this standard, submitting additional data to the agency that they said supported their claims that the standard could not be met. 
 
 EPA in its stay said "it appears that the promulgated standard is overly stringent," and said its decision was supported by additional performance data it received from a kiln at an Ash Grove Cement Company site in Chanute, KS, whose performance was the basis for the original standard. Relevant documents are available on InsideEPA.com. 
 
 EPA warned that if the current PM standard stayed in place, kilns could decide not to burn hazardous waste because they would be unable to achieve the standard. The kilns would then be subject to less stringent PM standards that apply to Portland cement kilns that do not burn hazardous waste. The waste could then be put into a landfill. "There is, thus, a potential environmental detriment associated with the current standard," the agency said. 
 
 EPA is now proposing a less stringent standard of 0.0075 gr/dscf, which the agency says is already being achieved by kilns at Ash Grove Cement Company’s Chanute site as well as kilns owned by Giant Cement Holding Inc. in Harleyville, SC, and Lafarge North America in Paulding, OH. "As a result, the Ash Grove Chanute kiln is no longer the single best performing source," EPA says in its proposal. 
 
The Coalition for Responsible Waste Incineration (CRWI) petitioned EPA requesting that the agency reconsider the procedure it used to identify the MACT standard for low volatile metals. The Sierra Club requested that EPA reconsider several other aspects of the rule, including EPA’s decision to establish subcategories of incinerators with and without dry air pollution control devices and the agency’s decision to base the MACT mercury standard for cement kilns on industry-submitted data.