|Parnell, jr., C|
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/5/2006
Publication Date: 6/30/2006
Citation: Lange, J.M., Parnell, Jr., C.B., Wanjura, J.D., Shaw, B.W. 2006. Impacts of PMC NAAQS and FRM PMC measurement methods on cotton gins. In: Proceedings of the Beltwide Cotton Conference, January 3-6, 2006, San Antonio, TX. 2006 CDROM. p. 682-688. Interpretive Summary: In response to the proposal by the EPA to the replace the PM10 NAAQS (the National Ambient Air Quality Standard for particulate matter less than or equal to 10 microns) with a PMcoarse (all particulate matter between 2.5 and 10 microns) NAAQS, agricultural industries need to make public comment on this issue. The proposed PMc NAAQS will be 70 ug/m3. The current PM10 NAAQS is 150 ug/m3, more than twice that of the proposed NAAQS. This is a serious concern for agricultural industries, particularly cotton gins, because the majority of agricultural particulate matter is larger than 2.5 microns and these industries will consequently be held to a higher standard than with the current PM10 standard. This will become even more of a concern when regulators use the NAAQS as a property line "concentration not to be exceeded". This use of the NAAQS in conjunction with the lowering of the NAAQS will cause many regulatory problems for agricultural industries. Whereas currently, the gins do not exceed the PM2.5 or PM10 NAAQS, these same gins will exceed the proposed PMc NAAQS. The gins have not increased their production rate or altered the facility in any manner which would increase their particulate matter emissions, but they now exceed the particulate matter NAAQS as shown in the scenarios included in this manuscript. In order for these gins not to exceed the NAAQS, the proposed PMc NAAQS needs to be set at a level which is equitable for all industries and regions. One suggestion made in the work presented is to set the PMc NAAQS at 150 ug/m3 (the level of the current PM10 NAAQS). Unless valid health effects studies can validate the need for the lower standard, the standard should be set at this current level.
Technical Abstract: The EPA is in the process of promulgating a new National Ambient Air Quality Standard (NAAQS) for concentrations of particulate matter (PM) in the size range of 2.5 to 10 micrometers aerodynamic equivalent diameter. PM in this size range is referred to as PM coarse (PMc). The proposed primary PMc NAAQS will be set at 70 ug/m3 (24 hour average). This NAAQS is less than 50% of the current PM10 NAAQS of 150 ug/m3 and it is slightly higher than the PM2.5 NAAQS of 65 ug/m3. There are two regulatory uses of the NAAQS. One is to determine the attainment status of an area. Sufficient numbers of concentration measurements exceeding the NAAQS can result in the designation of an area as being in non-attainment. The second use of the NAAQS is as a "concentration not to be exceeded" at or beyond the property line. The second use of the NAAQS can be extremely detrimental to agricultural operations especially if the PMc concentrations determined through modeling or measurement are incorrect. Currently, there are no federal reference methods (FRM) for measuring PMc concentrations. The proposed method for determining PMc concentrations is to subtract FRM PM2.5 concentration measurements from FRM PM10 concentration measurements. This method is referred to as the "difference" method. It is likely that the use of this method will result significant errors in PMc concentration determinations. FRM PM2.5 and PM10 samplers have been shown to exhibit sampling errors when sampling PM emissions from agricultural operations due to the interaction between the sampler and the sampled particulate matter. PM emitted by cotton gins typically has a mass median diameter (MMD) on the order of 18 um with a geometric standard deviation (GSD) of approximately 2.0. A small percentage of the PM emitted by cotton gins is PM2.5. Because of the large size of PM emitted by cotton gins (compared to PM emitted from urban sources), 145 to 148 ug/m3 would correspond to the correct PMc concentration for a PM10 concentration of 150 ug/m3. The difference is less than the uncertainty associated with FRM PM10 measurements. The work presented in this manuscript points out that any PMc NAAQS less than 150 ug/m3 will result in unjustified limits of property line concentrations for agricultural operations including cotton gins. Problems associated with the implementation of the proposed PMc NAAQS as a property line concentration limit for cotton gins is also addressed.