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The untreated CVXH is highly corrosive (pH > 13). The major potential human exposure pathway for the material is dermal contact that could result in severe, possibly irreversible, burns to the skin or eyes. Overall, the risk from an accidental spill appears to be comparable to that expected for any highly corrosive material with high pH.
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Although the individual DuPont and U.S. Army toxicity studies are limited in scope and applicability, the studies—considered in their totality—do not preclude the handling and transportation of untreated CVXH if appropriate engineering and administrative controls and personal protective equipment are used.
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Regarding ethyl methylphosphonic acid (EMPA) and methylphosphonic acid (MPA), two degradation products contained in CVXH, if an accident occurs during handling and transportation, groundwater or surface water contamination and subsequent human ingestion is unlikely but possible. Limited data are available to determine the risks from exposure to nonlethal ingestion of EMPA and MPA. However, oral lethality studies indicate the two substances have a Hodge and Sterner toxicity rating of 4 (slightly toxic).
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Although the health effects demonstrated in animal toxicity studies of exposure to CVXH were not due to residual VX or EA 2192 (another degradation product, potentially present in CVXH, with nerve agent properties), the data in one of the cited studies were inconclusive due to the lack of appropriate study controls.
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The clearance criteria for VX and EA 2192 are suitable for the risk management approaches proposed by the Army. According to these criteria, the CVXH will be certified to be non-detected for VX and EA 2192 using analytical methods with an EPA method detection limit of ≤20 ppb for VX and ≤1 ppm for EA 2192. The 20 ppb criterion for VX is the same as that used for the U.S. Army emergency drinking water standard for soldiers.
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The DuPont transportation plan appropriately addresses key risk management considerations, as well as DOT’s regulations for transporting hazardous materials.
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Precautions used to manage the corrosivity hazard characteristic in the event of a spill are adequate to protect response personnel from the caustic nature of the CVXH, low-level residual agent VX, or residual EA 2192 at levels estimated for maximum credible event analysis.
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Transportation of CVXH produced when processing VX with the DIC stabilizer at 8% loading is feasible. However, transportation of CVXH produced with VX stabilized with DCC or at agent loadings greater than 8% is not recommended at this time because of uncertainties in the amount of organic layer and potential residual VX exceeding 20 ppb and/or EA 2192 exceeding 1 ppm.
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The data demonstrate the effectiveness of neutralizing DIC-stabilized VX using sodium hydroxide at the 8% VX agent loading rate. Scale-up of the process from laboratory/bench-scale to pilot-scale should be feasible. However, because NECDF will be a pilot facility, process changes must be anticipated, along with resultant variations in hydrolysate composition sent for off-site treatment.
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The VX agent loading recipe and the specific stabilizer (DIC, DCC) employed significantly impacts the destruction process, hydrolysate composition, analytical methods validation, and possibly solids formation. Scale-up of the process from 8% to 16% VX agent loading and processing of DCC-stabilized VX are of particular concern because of the potentially significant VX concentration in the resulting organic layer, and possible problems in the analysis of CVXH. The process and analytical data for VX stabilized with DCC or mixtures of DIC and DCC have not been provided to CDC.1
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The impact of potential solids formation during the hydrolysis process on operations (e.g. possible blockage of the in-line static mixer, control valves, and sampling system), VX analytical methods, and off-site hydrolysate treatment is unknown. The transition from 8% to 16% VX agent loading, as well as variation in the VX stabilizer characteristics, is of concern and requires additional detailed studies.
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The current analytical methods for the analysis of VX agent and EA 2192 in 8% VX loaded, DIC-stabilized CVXH are adequate to detect and quantify at the established clearance levels for VX (≤20 ppb) and EA 2192 (≤1 ppm).
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The Army’s proposed use of EPA’s method detection limit (MDL) concept in the clearance of off-site shipment does not preclude analytical instrument detection of low-levels of VX and EA 2192 (generally below 20 ppb for VX and 1 ppm for EA 2192) in the DIC-stabilized, 8% agent loading CVXH. The perception that the clearance criteria (defined as “non-detected” with a MDL of ≤20 ppb VX or ≤1 ppm EA 2192) indicate absence of analytically detectable VX and/or EA 2192 could be misleading. While CDC believes that utilizing the MDL approach would not result in public health concerns, the Army needs to address potential public misperceptions regarding the detection or non-detection of VX in CVXH. A simpler reporting scheme (i.e., non-detected, detected at <20 ppb, or detected at >20 ppb) should be considered.
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The overall quality assurance/quality control (QA/QC) plan and procedures for the NECDF laboratory are well designed and documented. However, NECDF laboratory personnel must continue to implement the QA/QC plan by developing day-to-day operational data to demonstrate that all analytical systems are operational and under control before plant startup.
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The DuPont facility should be able to effectively treat the CVXH generated from an 8% VX agent loading with DIC stabilizer (i.e., pH adjustment, thiolamine destruction, conversion of EMPA to MPA), with the exception of MPA, for which only minimal reduction has been demonstrated. DuPont has recent developed a process to remove phosphonates, including MPA. CDC will evaluate this process in a separate report.
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The performance of the DuPont facility should be unaffected when treatment of material is alternated between Aberdeen sulfur mustard hydrolysate and Newport CVXH.
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The DuPont treatability studies have not yet demonstrated the effective treatment of CVXH produced from 16% agent VX loading, nor has effective treatment been shown for CVXH produced from 8% agent VX loading, where the VX was originally stabilized with DCC or a mixture of DIC and DCC stabilizers.
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DuPont’s Screening Level Ecological Risk Assessment (SLERA) does not contain information adequate to conclude that there is no unacceptable risk from the discharge of treated CVXH to the Delaware River. Also, a number of constituents of the discharged waste were omitted from the analysis.
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Several issues need to be addressed before treatment and discharge of this treated CVXH to the Delaware River can occur, including whole effluent toxicity testing procedures, potential for the presence of VX nerve agent and other toxic breakdown products in the CVXH, addition of phosphorus to the estuary, and the National Pollutant Discharge Elimination System permit.
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The EPA expressed concerns that the 20 ppb clearance criteria for VX is based “solely on the protection of humans from a drinking water source and may not be protective of aquatic organisms through ingestion or dermal exposure.”
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EPA believes that the conclusions of the SLERA for discharge of treated CVXH in the Delaware River are not valid.
Report for Congress: Review of the U.S. Army Proposal for Off-Site Treatment and Disposal of Caustic VX Hydrolysate From the Newport Chemical Agent Disposal Facility
Findings
The major findings for each aspect of the evaluation are presented below.
Health Hazard Considerations for Safe Management of Newport Caustic Hydrolysate [Caustic VX Hydrolysate]
Transportation Safety Assessment and Risk Management Plan
Treatability of Newport Caustic Hydrolysate [Caustic VX Hydrolysate]
Production of Caustic VX Hydrolysate at NECDF
Analytical Methods for VX and EA 2192 in Caustic VX Hydrolysate
Treatment of Caustic VX Hydrolysate at DuPont
Screening Level Ecological Risk Assessment for Discharge of Effluent from the Treatment of Newport Caustic Hydrolysate [Caustic VX Hydrolysate] - Summary of EPA Findings
