6 CCR 1007-3-8.30 - Basis and Purpose

Listing of Mustard Agent as Waste Codes P909 and P910 in § 261.33(e)

These amendments to 6 CCR 1007-3, Part 261 are made pursuant to the authority granted to the Hazardous Waste Commission in section 25-15-302(2), C.R.S.

The Colorado Hazardous Waste Regulations, 6 CCR 1007-3, Part 261, Subpart B, allow chemicals or other materials that are solid wastes to be added to the hazardous waste listings if the chemical can be shown to meet any one of the criteria listed in § 261.11. The Commission believes that, once the Mustard Agent meets the regulatory definition of "discarded" found in § 261.2(a)(2), and "discarded commercial chemical product, off-specification species, container residue, or spill residue" found in § 261.33, it also meets several of the listing criteria and, for the reasons presented herein, should be added as a P-listed hazardous waste.

This regulation adds waste (discarded) Mustard Agent to the P-listings found in § 261.33 of the regulations as an acutely toxic discarded chemical product. The regulatory criteria for listing a hazardous waste can be found in 6 CCR 1007-3, § 261.11. In summary, a solid waste can be listed as a hazardous waste if it meets any one of three (3) criteria: first, if it exhibits any characteristic of a hazardous waste; second, if it presents or is suspected to present certain acute human health hazards; and last, if it is capable of posing a substantial present or potential hazard to human health or the environment when improperly managed. Only the second criterion applies to acutely toxic materials, as the Division has proposed Mustard Agent to be.

Currently, the only facility in Colorado known to have material affected by this proposed hazardous waste listing is the Pueblo Chemical Depot (PCD), owned and operated by the United States Army (the Army). PCD has an inventory of 780,078 munition rounds containing 2611.05 tons of Mustard Agent. This represents almost 10% of the nation's chemical weapons stockpile. The inventory is in the form of 105mm and 155mm projectiles, and 4.2 inch mortar rounds.

By public law, Congress has directed the Army to destroy the entire PCD inventory of stockpile Mustard Agent. However, the Army has stated they have a continuing mission to maintain the Mustard Agent munition stockpile in a viable form. Nevertheless, because of chemical weapon treaty requirements and Congressional mandate, the Army has been pursuing chemical weapon destruction, including destruction of Mustard Agent. At PCD, Mustard Agent destruction will involve the treatment of the Mustard Agent by incineration or an alternative technology.

The P-listing proposed herein would apply to Mustard Agent that has been declared surplus or waste as a discarded chemical product, Mustard Agent that has been declared to be off-specification, and Mustard Agent spill residues and container residues, all of which are solid wastes.

Overview of 2,2-di(chloro-ethyl)sulfide ("Mustard Agent")

The term "mustard" can refer to several chemicals, but most commonly it refers to 2,2-di(chloro-ethyl) sulfide, or sulfur mustard. Mustard Agent is a synthetic organic compound that was first manufactured in 1822. The compound is stored as liquid and has a low vapor pressure at ordinary atmospheric temperature and pressures. As such, it evaporates into a gas very slowly under normal conditions. It was manufactured to be used in chemical warfare and was used as early as World War I and as recently as 1984-1988 during the Iran-Iraq war. During wartime, a Mustard warhead explodes on impact, vaporizing and spreading the contained agent in an area of enemy troops. As explained later, its effects during wartime are designed to be debilitating, if not fatal, via inhalation and dermal contact.

Mustard Agent is not used in the United States, except in laboratory settings. It does not occur naturally, and therefore, there are no natural background levels in the soil, air, water, or food. The known stockpile of Mustard Agent in the United States is under the control of the U.S. Army. While accidental releases of Mustard Agent and Mustard Agent wastes that are managed at Army facilities could adversely impact public health, workers at these facilities are more likely to be exposed than the general population.

If it is accidentally released, Mustard Agent in soil and under water may persist for up to 30 years. There is very little information on the transformation and degradation of Mustard Agent in the soil. Meteorological conditions such as temperature, humidity, and wind greatly affect persistence; with warmer temperatures and stronger winds, persistence decreases. The long residence time of Mustard Agent in soil and under water is thought to be due to the formation of a sulfonium-salt layer or a polymerized mustard-type compound that may insulate the agent.

Mustard Agent is very insoluble in water, but once dissolved, it rapidly hydrolyzes to thiodiglycol. Hydrolysis is primarily through reaction with surface water bodies rather than moisture in air. The half-life of Mustard Agent in a dissolved state is estimated to be 55 minutes at 10° C and 4 minutes at 25° C. Certain degradation products of Mustard Agent formed in the environment are toxic. Some of the degradation products include hydrochloric acid, ethylene, ethylene dichloride, 2,2-dichlorodiethyl disulfide, vinyl chloride, hydrogen sulfide, and oxathione.

Health Effects of Mustard Agent

Mustard Agent is a highly toxic compound and vesicant (blistering agent). It is known to be lethal from primary and secondary effects. However, the existing data on health effects for inhalation, oral, and dermal exposure of humans and animals to Mustard Agent are limited. Sufficient information is available from human exposure data to identify the skin and respiratory passages as target organs to acute, subchronic, and chronic exposures to this chemical warfare agent.

Inhalation: The estimated lethal concentration for Mustard Agent in humans via inhalation exposure is 50 mg/m3 for 30 minutes. If inhaled even at lower concentrations, its effects cause bronchitis, and blistering in the lungs. Long-term respiratory disease may result from even low-dose exposures. Repeated exposure can result in hypersensitivity to its effects.

Dermal Contact: Mustard Agent burns skin and causes blisters within a short time of exposure. Parts of the body that are moist are more likely to be harmed and it can easily pass through normal clothing to get on the skin. Agent exposure causes eye burning and eyelid swelling. The subcutaneous LD50 in rat is 2 mg/kg. The LD50 for Mustard Agent applied to rat skin was reported as 9-12 mg/kg. The dermal LD50 for Mustard Agent on rabbit skin was 40-100 mg/kg.

General: Ingestion of Mustard Agent results in necrosis and epigastric distress. Systemic absorption results in injury to the bone marrow, lymph nodes, and spleen producing leukopenia and thrombocytopenia. Mustard Agent is able to alkylate DNA, RNA, and proteins, and as a result, it can affect a variety of cell functions. This includes causing cell death by inhibition of DNA repair and replication, altering proteins that have been coded by alkylated RNA, structurally altering cell membranes, or otherwise altering cell proteins.

A mutagen and a carcinogen, Mustard Agent penetrates deep within tissue, resulting in destruction and damage at some depth from the point of contact. The actions of Mustard Agent resemble those produced by ionizing radiation and, therefore, Mustard Agents are often referred to as radiomimetic compounds. Penetration is rapid, so that efforts to remove the toxic agent from the exposed area are ineffective after 30 minutes. Only very limited data are available to assess the toxicokinetic properties of Mustard Agent. Mustard Agent changes into other chemicals (e.g., thiodiglycol and conjugates, sulfone products, and glutathione conjugates) in the body and these chemicals are excreted in the urine within a few weeks. Though a demonstrated teratogen in animals, it is not known whether Mustard Agent can cause birth defects or affect reproduction in humans. The estimated bioconcentration factor ranges from 7-15.

Regulatory Evaluation

The regulatory criteria for listing a solid waste as a hazardous waste can be found in 6 CCR 1007-3, § 261.11. As explained previously, this proposed listing applies to Mustard Agent that has been declared by the Army to be waste or surplus and removed from the chemical weapon stockpile to be destroyed. Therefore, it applies to Mustard Agent that is a solid waste.

The first criterion to list a solid waste as a hazardous waste in § 261.11(a) is that the solid waste exhibits any of the characteristics of a hazardous waste identified in Subpart C (§ 261.11(a)(1)). These characteristics are ignitability, reactivity, toxicity, and corrosivity. Of these, EPA has determined that Mustard Agent is reactive. The reason for this is Mustard Agent's ability, under certain circumstances, to rapidly react with water to form hydrogen sulfide, a highly toxic gas, as well as other toxic compounds such as hydrochloric acid. In addition, even though as manufactured Mustard Agents did not contain any toxicity characteristic (TC) constituents, the Army has chosen to apply TC waste codes D004 through D011 because these metals may have leached from the special alloys used in the munition casings.

The second criterion to list a solid waste as a hazardous waste in § 261.11(a) is that the waste has been found to be fatal in humans in low doses, or in the absence of data on human toxicity, it has been shown in studies to have certain specific animal toxicities (§ 261.11(a)(2)). There are enough human toxicological data and other information to meet the criteria of "fatal to humans in low doses." In addition, one of the specific animal toxicities presented in § 261.11(a)(2) is a dermal LD50 toxicity (rabbit) of less than 200 mg/kg. Mustard Agent meets this criterion with a dermal LD50 for rabbits of 40-100 mg/kg. Pursuant to the preamble to this regulation found in the May 19, 1980 Federal Register (45 FR 33083-33119), materials that meet this criterion are acutely hazardous wastes, and included in § 261.33(e) as P-listed wastes. Therefore, this is the criterion Mustard Agent must meet to be listed as an acutely hazardous waste, or a P waste.

The third and last regulatory criterion in § 261.11(a) is that the solid waste contains any Appendix VIII constituents and that the Director concludes that the waste is capable of posing a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported or disposed of, or otherwise managed (§ 261.11(a)(3)). Pursuant to the preamble to this regulation found in the May 19, 1980 Federal Register (45 FR 33083-33119), materials that meet this criterion are toxic wastes, and are included in § 261.33(f) as U-listed wastes. A U-listing is not part of this regulation, therefore, this criterion does not apply.

Based on the above regulatory evaluation, waste Mustard Agent meets the necessary criteria presented in § 261.11(a) of the regulations for listing as an acute hazardous waste. Therefore the Commission is adding waste Mustard Agent to the P-listed wastes found in § 261.33 of the regulations by adding wastes codes P909 and P910 for the H and HD forms of Mustard Agent (CAS # 505-60-2) and the HT form of Mustard Agent (CAS # 505-60-2 and # 63918-89-8), respectively.

At a later time, when a specific treatment has been determined for destruction of waste Mustard Agent, the Commission understands that the Division will propose appropriate K-listings, as well as other appropriate listings, for specific waste treatment residues of Mustard Agent under § 261.32 of the regulations.

4.4 Benefits of Listing Mustard Agent as a Hazardous Waste

The principal benefits of listing waste Mustard Agent are:

1) Increased regulatory definition for management of waste Mustard Agent and agent treatment residues. Mustard Agent is a hazardous waste only because it is characteristic for reactivity and may be characteristic for metals toxicity. To treat a characteristic waste, it is only necessary to remove the characteristic. By listing Mustard Agent specifically, it requires more complete and appropriate treatment to remove the listing. The Commission believes this to be appropriate given Mustard Agent's extremely toxic health effects. The State gains additional accountability from the Army's ensuring protection of human health and the environment during interim management of waste Mustard Agent (the time between the agent being discarded and agent treatment), during treatment and destruction of Mustard Agent, and during disposition and management of treatment residuals.
2) Increased regulatory guidelines/enforcement for the treatment and management of associated wastes streams - munition parts, PPE, dunnage, etc. It is very unlikely that these materials would be reactive hazardous wastes. However, if agent wastes were listed, they would carry the listing until they were either delisted or fully treated or decontaminated. These materials make up important associated waste streams in the demilitarization process and could have, if improperly managed, significant impact on human health and the environment.
3) Any delisting that may be proposed by the Army for residual waste streams would have to be approved by the Commission.
4) Currently at PCD, it becomes difficult to discern when Agent-contaminated materials are hazardous waste (such as wooden pallets, laboratory wastes, PPE, etc). This is true both for Army and Division personnel. By assuming these materials are characteristic hazardous wastes, the Army has improved management of these materials at PCD. However, they are not necessarily required to manage them as hazardous wastes since many of these materials may not be characteristic wastes. Listing Mustard Agent clarifies when hazardous waste regulations apply and requires adequate record keeping and management of current and future inventories of waste Mustard Agent and other materials contaminated with Mustard Agent.
5) Under the P-listing, any spills (to soil or otherwise) would require cleanup and disposition as a listed hazardous waste, even though the soil may not be characteristic for reactivity.
6) With the recent Congressional mandate to the Army to study alternative technologies, and with Pueblo being a possible candidate for implementation of an alternate technology, listing Mustard Agent forces the Army to consider the listing in their alternative technology selection criteria. Because of this listing, secondary process wastes may be listed hazardous wastes and, therefore, the Army must plan waste management into their treatment selection to ensure proper waste management, and perhaps to minimize waste generation.

The anticipated costs to the Army related to the impact of this listing are minimal when compared to the overall cost of treatment and destruction of the agent. Many of these costs are already factored into the cost of the project.

Summary of Other State's Listings for Mustard Agent

There are seven states, plus Johnston Island, where Mustard Agents are currently stored as part of the chemical weapons stockpile. Five of these states have listed Mustard Agent as a hazardous waste. Each listing is slightly different, as described below:


Listed HD and HT as P998 (blister agents). Principal justification was "to ensure adequate regulatory control over Mustard Agents that are destined for disposal and to deal with spill response and cleanups."

Listed HD and HT as F998 (blister agents). Principal justification was "to address the residues from treating, testing, and demilitarization of blister agents."


Originally listed as P999 and F999. Utah has been reworking their listing for over a year. Anticipated changes include removal of the F999 listing and addition of several K-listings.


Listed in Indiana Hazardous Waste Management rules as I001. Listing includes H, HD, and HT.


Listed in Kentucky Hazardous Waste Management Rules as N003. Listing includes H and related compounds.


Listed in Code of Maryland Regulations as K997 - Waste HD and K998 - Waste T.

These states, except Indiana, have significant inventories of Mustard Agent. Utah already has the Tooele incinerator (TOCDF) up and operating; Oregon has recently issued a hazardous waste permit for a similar incinerator to be built at the Umatilla Chemical Depot.

Statement of Basis and Purpose - Rule-making Hearing of September 16, 1997


6 CCR 1007-3-8.30
37 CR 24, December 25, 2014, effective 3/2/2015 38 CR 11, June 10, 2015, effective 6/30/2015 39 CR 05, March 10, 2016, effective 3/30/2016 39 CR 11, June 10, 2016, effective 6/30/2016 40 CR 06, March 25, 2017, effective 4/14/2017 40 CR 11, June 10, 2017, effective 6/30/2017 40 CR 21, November 10, 2017, effective 11/30/2017 41 CR 06, March 25, 2018, effective 4/14/2018 41 CR 11, June 10, 2018, effective 6/30/2018 41 CR 24, December 25, 2018, effective 1/14/2019 42 CR 06, March 25, 2019, effective 4/14/2019 42 CR 06, March 25, 2019, effective 5/30/2019 42 CR 11, June 10, 2019, effective 6/30/2019 43 CR 12, June 25, 2020, effective 7/15/2020 44 CR 06, March 25, 2021, effective 4/14/2021 44 CR 11, June 10, 2021, effective 6/30/2021 44 CR 24, December 25, 2021, effective 1/14/2022 45 CR 11, June 10, 2022, effective 6/30/2022 45 CR 17, September 10, 2022, effective 9/10/2022 45 CR 17, September 10, 2022, effective 9/30/2022 45 CR 23, December 10, 2022, effective 1/30/2023

State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.