“I also want to thank Daryl Kimball and the Arms Control Association for allowing me to address all of you today and for being such effective advocates for sensible policies to stem the proliferation of weapons of mass destruction, and most importantly, reduce the risk of nuclear war.”

– Joseph Biden, Jr.
January 28, 2004
Updating the CWC: How We Got Here and What Is Next

April 2020
By Stefano Costanzi and Gregory D. Koblentz

In late June 2018, Charlie Rowley and Dawn Sturgess, residents of Amesbury in the United Kingdom, discovered a discarded perfume bottle. Just 15 minutes after Sturgess sprayed her wrists to test the scent at home, she became ill and, nine days later, became the only fatality from a chemical weapons agent used in the UK. Rowley, exposed to a lesser degree, survived after multiple hospitalizations.

Flowers are left in memory of Dawn Sturgess at the Salisbury, UK, facility where she died after being exposed to a nerve agent in 2018. Not targeted, she was the only death from the use of the chemical weapon agent. (Photo: Matt Cardy/Getty Images)UK authorities determined that the chemical in the perfume bottle belonged to a class of nerve agents known as Novichoks, one of which had just been used in the attempted assassination of Sergei Skripal, a former Russian agent who defected to the UK, in the nearby town of Salisbury in March 2018. That attack also poisoned Skripal’s daughter and two police officers. The UK has accused Russia of being behind the plot and has charged two Russian intelligence officers with conducting the attack. In response, the UK and its allies expelled more than 100 Russian diplomats suspected of being spies and imposed sanctions on Russia and government officials who were involved in the assassination plot.

The appearance of the Novichok agent in two UK towns also triggered an update to the Chemical Weapons Convention (CWC), a 193-member treaty that bans the development, production, stockpiling, and use of chemical weapons. CWC parties agreed in November 2019 to add Novichok agents to the lists of chemicals subject to the treaty’s declaration requirements and verification regime. In particular, they agreed to add Novichoks, as well as another class of chemical warfare agents belonging to a group of chemicals known as carbamates, to Schedule 1, a list of chemicals with few or no known uses beyond serving as chemical warfare agents or their precursors. These chemicals are subject to the most stringent restrictions and declaration requirements. The path to this amendment, the first ever modification to the treaty, was difficult to navigate.

Novichoks and Carbamates

Novichok (“newcomer” in Russian) is an umbrella term that collectively includes several families of nerve agents developed by the Soviet Union during the Cold War under the scope of a chemical weapons program known as Foliant.1 The chemical structure of these organophosphorus nerve agents, also called A-series agents, was first publicly revealed in 2009 in the book State Secrets by Vil Mirzayanov, a former analytical chemist in the Soviet chemical weapons program turned whistleblower.2 The agents work by inhibiting the enzyme acetylcholinesterase, which is essential for the functioning of the nervous system, with deadly consequences.3 Russia has consistently denied researching or producing the agents or being involved in the attack on the Skripals.

Although Western governments were aware of the Foliant program and Novichok agents by the 1990s, they did not seek to include these agents in the CWC negotiations for fear of compromising sources and methods and the proliferation risk associated with publicizing a new class of nerve agents. As a result, when the CWC was opened for signature in 1993, its original Schedule 1 omitted the Novichok families.

Carbamates are an entirely different class of chemicals. These carbamates are not chemically related to Novichoks and, unlike traditional nerve agents, are not organophosphorus compounds. Yet, the biochemical bases of their toxicity, interfering with acetylcholinesterase, are similar to those of organophosphorus nerve agents such as sarin, VX, and Novichoks. Carbamates were researched as chemical warfare agents by the United States during the Cold War, but never developed into chemical weapons.4 Probably for this reason, carbamates were omitted from the CWC’s original Schedule 1.

The Convoluted Road to Amendment

As part of its prohibitions, the CWC bans the intentional use of any chemical, through its toxicity, to harm humans or animals. To support its implementation and its verification regime, the CWC contains in its Annex on Chemicals three schedules of chemical warfare agents and precursors for their synthesis.5 Schedule 1 is reserved for chemicals and their precursors that have primarily military uses. The other two schedules identify chemicals that can have weapons applications but also have considerable peaceful uses that are not prohibited by the CWC. Schedule 2 covers agents that can be used in smaller quantities, and Schedule 3 addresses chemicals that are widely used for legitimate commercial purposes. Each schedule is also composed of a part A, which lists chemical warfare agents, and a part B, which lists precursors for their synthesis.

In the aftermath of the Salisbury incident, the director-general of the CWC’s implementing agency, the Organisation for the Prohibition of Chemical Weapons (OPCW), took a first step. He solicited the Scientific Advisory Board (SAB), a subsidiary body that provides specialized advice on science and technology issues to the organization, with collecting information from public literature on new toxic chemicals that could act as nerve agents. The director-general also asked the treaty’s members to voluntarily share information with the SAB.6 Although the SAB report has not been released publicly, the SAB reportedly found no peaceful uses for Novichok agents.7

The Salisbury events also prompted the submission of two competing proposals to amend Schedule 1. The first came from Canada, the Netherlands, and the United States on October 25, 2018.8 This joint proposal sought to add to Schedule 1 two of the families of Novichok agents described by Mirzayanov, technically, a family of fluorophosphonates and a family of fluorophosphates, both with amidine branches attached to the core of the molecules. The agent reportedly employed in the Salisbury incident, A-234, belongs to the latter family.9

The second proposal, originally comprising five distinct elements, was submitted by Russia on November 30, 2018. Although the OPCW did not publicly disclose the details of this proposal, its content was revealed when the U.S. Department of Commerce Bureau of Industry and Security sought public comments on the potential impact on commercial activities of the proposed additions to Schedule 1 of the CWC.10 The first two elements of the Russian proposal contained a limited subset of the two families listed by the joint proposal. The other three elements contained chemicals not covered by the joint proposal. In particular, the third element comprised a single fluorophosphonate compound, which had also been described by Mirzayanov.11 Unlike the agents covered by the joint proposal, this chemical has a guanidine branch attached to the core of the molecule, rather than an amidine branch.

The fourth element comprised carbamates, which, as mentioned, are an entirely different class of chemicals. Specifically, this element included two families of carbamates that had been researched as chemical warfare agents by the United States during the Cold War but never developed into chemical weapons.12

Finally, the fifth element of the Russian proposal comprised a group of chemicals, technically alkylphosphorofluoridates with carbonimidic branches, that had been described by some sources as alternative structures for Novichok agents.13

The OPCW’s governing body, the Executive Council, recommended by consensus the adoption of the joint proposal on January 14, 2019. The council examined the Russian proposal on February 25, 2019, and did not recommend its adoption. According to a summary of the meeting, “[T]he rejection of the decision resulted from the states parties failing to reach a consensus on the fifth proposal, due to disagreements on whether the chemicals within the proposal were consistent with the guidelines in the Convention for Schedule 1A.”14 In April 2019, within the 90-day, treaty-specified deadline, Russia submitted its formal objection to the joint proposal, thus preventing the council’s recommendation from becoming final. As a result, the joint proposal and the Russian proposal were forwarded to the annual OPCW meeting of all states-parties for a final decision.

UK Defense Ministry official Annabel Goldie speaks to OPCW's Conference of States Parties on Nov. 25, 2019. She called for the adoption of a joint proposal to amend the CWC's list of most lethal chemical agents. (Photo: OPCW)Before that Conference of the States Parties was set to meet in The Hague on November 25–29, 2019, both sides engaged in quiet diplomacy behind the scenes. On April 30, 2019, Russia proposed quadripartite consultations with the sponsors of the joint proposal to merge the two proposals into a “compromise” document. The joint sponsors refused this offer and insisted that the conference vote on the proposals separately. In light of this stance and the Technical Secretariat’s determination that the chemicals included in the fifth element of the Russian proposal did not meet the criteria for inclusion in Schedule 1, Russia recognized that its effort to include the fifth element of its proposal would not gain support among other states-parties. In September, Russia modified its proposal to drop the fifth element. This move enabled the conference to approve both proposals by consensus.15 In light of the growing polarization within the OPCW due to Russian support for Syria over its continued use of chemical weapons and Russia’s own use of chemical weapons in Salisbury, the adoption of such a historic change to the CWC by consensus was a victory for diplomacy and international cooperation.

Four New Entries

The chemicals that will be added to CWC Schedule 1 are listed below.16 All of the new entries will be in part A of Schedule 1.17

Entry 13 (CWC 1A13). A large family of Novichok agents comprised of fluorophosphonates with amidine branches, this is the first Novichok family listed in the joint proposal, which has a wider scope than the first element of the Russian proposal.

Entry 14 (CWC 1A14). A large family of Novichok agents comprised of fluorophosphates with amidine branches, this is the second Novichok family listed in the joint proposal, which has a wider scope than the second element of the Russian proposal. Notably, this is the Novichok family to which the A-234 agent reportedly employed in the Salisbury incident belongs.

Entry 15 (CWC 1A15). A single additional Novichok agent not covered by the joint proposal, namely a fluorophosphonate compound with a guanidine branch, this is the third element of the Russian proposal.

Entry 16 (CWC 1A16). Two families of carbamate agents, namely quaternaries and bisquaternaries of dimethylcarbamoyloxypyridines, this is the fourth element of the Russian proposal.

The amendment will enter into force on June 7, 2020, 180 days after the UN secretary-general received notification of the decision reached by the Conference of the State Parties. The addition of these nerve agents to Schedule 1 has the effect of subjecting them to the stringent CWC verification regime and declaration requirements. In particular, in accordance with Part VI of the CWC Verification Annex, states-parties that are operating, or intend to operate, a single small-scale facility for the production of the newly scheduled chemicals will have to provide the OPCW Secretariat a detailed description of the facility and its location. Similarly, states-parties will have to notify the secretariat of the presence of the newly scheduled chemicals in “other facilities for protective purposes…and other facilities for research, medical or pharmaceutical purposes.” These facilities, if already existing, will be promptly inspected by the OPCW, in line with the CWC verification regime. Moreover, the projected activities to be conducted at the reported facilities will have to be declared in advance to the OPCW on an annual basis.18 An exception are laboratories that synthesize an aggregate quantity of Schedule 1 chemicals of less than 100 grams per year for research, medical, or pharmaceutical purposes, which are not subject to the declaration and verification obligations.

Treaty members that have dismantled facilities that have engaged in work with the newly added Schedule 1 chemicals will not have to declare those facilities. This applies, for instance, to the Shikhany branch of the State Scientific Research Institute of Organic Chemistry and Technology, which was the Soviet Union’s primary chemical weapons research and development center. According to former Soviet chemical weapons scientists, Novichoks were originally developed there beginning in the 1970s.19 In April 2018, only a month after the UK accused Russia of being responsible for the Salisbury attack, Russia announced that it was going to demolish this chemical weapons center.20 The decision was ostensibly made in the wake of Russia’s completion of the destruction of its declared chemical weapons stockpile under OPCW supervision. Yet, if the chemical weapons facility at Shikhany is demolished by the time the amendment goes into effect in June 2020, then it will also relieve Russia of having to declare the facility under the new verification requirements.

Where to Go Now

The addition of these Novichok and carbamate agents to CWC Schedule 1 is very welcome, as they are chemicals endowed with very high toxicity, which has been reported to be comparable to or exceeding that of the potent nerve agent VX.21 Yet, recent computational studies are not in agreement with the high toxicity values reported by Mirzayanov.22

To further strengthen the CWC, its members should add more chemicals to the CWC schedules for the Novichok and carbamate classes. In particular, it is advisable to further amend the CWC schedules to cover the entire family of chemicals to which CWC 1A15 belongs. This is in line with the approach taken for entries CWC 1A13 and CWC 1A14, both of which contain a large family of chemicals, and will avoid dangerous loopholes that could allow proliferators to develop analogs of CWC 1A15 not covered by Schedule 1. It is also advisable to add to the CWC schedules another family of Novichok agents described by Mirzayanov, which still remains uncovered by the CWC schedules.23 The missing Novichok family is similar to the one to which CWC 1A15 belongs. They are both organophosphorus compounds with guanidine branches, but although the CWC 1A15 family is a family of phosphonates, the missing family is a family of phosphates. This parallels the relationship between the newly added entries CWC 1A13 and CWC 1A14, both of which describe organophosphorus compounds with amidine branches, phosphonates in the first case and phosphates in the second case.

Concerning carbamate nerve agents, a wealth of compounds whose structures do not fit within the two families described by the new Schedule 1 entry CWC 1A16 have been reported. Some of them are allegedly as potent as VX or more so.24 Hence, it is advisable to conduct a thorough survey of the known carbamate nerve agents and add the missing families to the CWC schedules.

To support the CWC verification mandates, it will be important to update the OPCW Central Analytical Database, ensure that inspectors are trained and equipped to test for Novichoks and carbamates during on-site inspections, and prepare OPCW-designated laboratories to test for these molecules.

A Resilient Treaty

The addition of these chemicals to the CWC is a testament to the strength and resilience of the treaty. The CWC has unlimited duration and, as a consequence, must remain current and relevant as the years pass, a concept known as qualitative universality.25 Amendments to the CWC schedules, like the very first one just witnessed, are indeed key tools to ensure that the pact’s declaration requirements and verification regime remain current and adapt to the changing landscape of the chemical weapons threat.

The CWC’s ability to remain relevant as the years pass and situations change goes beyond the possibility of being amended. In fact, even prior to the addition of Novichoks and carbamates to Schedule 1, their use as chemical weapons was still prohibited by the treaty: according to the CWC, any weapon that exploits the toxicity of chemicals to intentionally kill or harm humans or animals is considered a chemical weapon. This principle, known as the general-purpose criterion, is another fundamental pillar of CWC resiliency. The CWC focuses on the prohibition of the purposes for which technologies may be applied, not the technology itself. This is clearly stated in Article II, which says all “toxic chemicals and their precursors, except where intended for purposes not prohibited” under the CWC are to be considered chemical weapons.

Since the time the CWC was negotiated and entered into force, the chemical weapons landscape has changed significantly.26 The recently adopted changes to Schedule 1 will play a key role in strengthening the ability of the CWC to continue to serve as the linchpin in the international regime for preventing the proliferation of chemical weapons.



1. Stefano Costanzi and Gregory D. Koblentz, “Controlling Novichoks After Salisbury: Revising the Chemical Weapons Convention Schedules,” The Nonproliferation Review, Vol. 26, Nos. 5–6 (2019).

2. Vil S. Mirzayanov, State Secrets: An Insider’s Chronicle of the Russian Chemical Weapons Program (Denver: Outskirts Press, 2008), pp. 142–149.

3. Stefano Costanzi, John-Hanson Machado, and Moriah Mitchell, “Nerve Agents: What They Are, How They Work, How to Counter Them,” ACS Chemical Neuroscience, May 16, 2018, pp. 873–885; Kloske Marcin and Zygfryd Witkiewicz, “Novichoks—The A Group of Organophosphorus Chemical Warfare Agents,” Chemosphere, Vol. 221 (April 2019), pp. 672–682.

4. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, 2nd ed. (Boca Raton, FL: CRC Press, 2007), pp. 105–139.

5. Chemical weapons are weapons that kill or harm through the toxicity of chemicals. Chemical warfare agents are the toxic chemicals on which chemical weapons are based.

6. Organisation for the Prohibition of Chemical Weapons (OPCW) Technical Secretariat, “Note by the Director-General: Request for Information From States Parties on New Types of Nerve Agents,” S/1621/2018, May 2, 2018.

7. OPCW Scientific Advisory Board, “Report of the Scientific Advisory Board at Its Twenty-Eighth Session, 10–14 June 2019,” SAB-28/1, June 14, 2019, p. 17.

8. OPCW Executive Council, “Decision: Recommendation for a Change to Schedule 1 of the Annex on Chemicals to the Chemical Weapons Convention,” EC-M-62/DEC.1, January 14, 2019.

9. Mark Urban, The SKRIPAL Files: The Life and Near Death of a Russian Spy (London: Macmillan, 2018), p. 229.

10. Bureau of Industry and Security, U.S. Department of Commerce, “Impact of Proposed Additions to the ‘Annex on Chemicals’ to the Chemical Weapons Convention (CWC) on Legitimate Commercial Chemical, Biotechnology, and Pharmaceutical Activities Involving ‘Schedule 1’ Chemicals (Including Schedule 1 Chemicals Produced as Intermediates),” 84 Fed. Reg. 40389 (August 14, 2019).

11. Mirzayanov, State Secrets, p. 145.

12. Ellison, Handbook of Chemical and Biological Warfare Agents, pp. 105–139.

13. Ibid., pp. 37–42; Steven L. Hoenig, Compendium of Chemical Warfare Agents (New York: Springer, 2007), pp. 79–88.

14. OPCW Scientific Advisory Board, “Summary of the Third Meeting of the Scientific Advisory Board Temporary Working Group on Investigative Science and Technology,” SAB-28/WP.3, June 4, 2019, pp. 10–11.

15. OPCW, “Decision: Changes to Schedule 1 of the Annex on Chemicals to the Chemical Weapons Convention,” C-24/DEC.5, November 27, 2019; OPCW, “Decision: Technical Change to Schedule 1(A) of the Annex on Chemicals to the Chemical Weapons Convention,” C-24/DEC.4, November 27, 2019.

16. OPCW Technical Secretariat, “Note by the Technical Secretariat: Consolidated Text of Adopted Changes to Schedule 1 of the Annex on Chemicals to the Chemical Weapons Convention,” S/1820/2019, December 23, 2019.

17. For a structurally annotated table of the chemicals that will be added to CWC Schedule 1, see Costanzi Research, “A Historical Event: Chemicals Added to CWC Schedule 1,” n.d., https://costanziresearch.com/cw-nonproliferation/cw-control-lists/cwc-schedule-1-amendment/ (accessed March 18, 2020).

18. OPCW Technical Secretariat, “Note by the Technical Secretariat: Guidance for States Parties on Article VI Declaration Obligations and Inspections Following Entry Into Force of Changes to Schedule 1 of the Annex on Chemicals to the Chemical Weapons Convention,” S/1821/2019, December 31, 2019.

19. Mirzayanov, State Secrets, pp. 142-145; Ilia Rozhdestvenskiy, “The Secret Folio: How the Nerve Agent ‘Novichok’ Was Created and Tested on Human Beings,” The Project, September 12, 2018, https://www.proekt.media/narrative/test-novichok-eng/.

20. “The Institute, Which Allegedly Developed the ‘Novice,’ Demolishes Its Buildings,” RIA Novosti, April 27, 2018, https://ria.ru/amp/20180427/1519528336.html (in Russian).

21. Mirzayanov, State Secrets, pp. 142–149; Ellison, Handbook of Chemical and Biological Warfare Agents, pp. 105–139.

22. Hanusha Bhakhoa, Lydia Rhyman, and Ponnadurai Ramasami, “Theoretical Study of the Molecular Aspect of the Suspected Novichok Agent A234 of the Skripal Poisoning,” Royal Society Open Science, Vol. 6, No. 2 (2019): 181831; Lars Carlsen, “After Salisbury Nerve Agents Revisited,” Molecular Informatics, Vol. 38, Nos. 8–9 (2019): 1800106.

23. Costanzi and Koblentz, “Controlling Novichoks After Salisbury.”

24. Ellison, Handbook of Chemical and Biological Warfare Agents, pp. 105–139.

25. Jean Pascal Zanders, “The Chemical Weapons Convention and Universality: A Question of Quality Over Quantity?” Disarmament Forum, No. 4 (2002), p. 23.

26. See Rebecca K.C. Hersman, Suzanne Claeys, and Cyrus A. Jabbari, “Rigid Structures, Evolving Threat: Preventing the Proliferation and Use of Chemical Weapons,” Center for Strategic and International Studies, December 2019, https://csis-prod.s3.amazonaws.com/s3fs-public/publication/191218_Hersman_RigidStructures_WEB.pdf?LHDLRedZ2X3eEhGwYz7Ko8lXzSs1hEEO.

Stefano Costanzi is an associate professor of chemistry at American University. Gregory D. Koblentz is an associate professor and director of postgraduate programs in biodefense at George Mason University's Schar School of Policy and Government.