Nuclear, chemical and biological weapons cause harm in different ways. Nuclear weapons release enormous amounts of energy through nuclear reactions, producing powerful blasts, intense heat and radiation that can devastate cities and cause lasting health and environmental damage. Chemical weapons use toxic substances to poison people, potentially damaging the lungs, skin and nervous system. Biological weapons use disease-causing organisms or toxins to harm humans, animals or plants.
To address these threats, states have negotiated treaties that restrict or prohibit these weapons and establish disarmament obligations.
The Treaty on the Non-Proliferation of Nuclear Weapons (NPT), in force since 1970, seeks to prevent the spread of nuclear weapons, supports peaceful uses of nuclear energy and requires its parties to pursue nuclear disarmament negotiations in good faith.
The Treaty on the Prohibition of Nuclear Weapons (TPNW), in force since 2021, comprehensively prohibits nuclear weapons for its parties. Articles 6 and 7 establish obligations concerning assistance to people affected by nuclear weapons use or testing, environmental remediation and international cooperation.
The Chemical Weapons Convention (CWC) prohibits the development, production, stockpiling, transfer and use of chemical weapons and requires their destruction.
The Biological Weapons Convention (BWC) prohibits developing, producing, stockpiling, acquiring or retaining biological agents or toxins of types and quantities that lack justification for peaceful, protective or prophylactic purposes, as well as weapons designed to use them for hostile purposes.
Human and civilian impact
The atomic bombs dropped on Hiroshima and Nagasaki in 1945 killed tens of thousands of people immediately. The two cities’ memorial registers now include more than 540,000 names, including survivors who died in subsequent years; this should not be interpreted as a count of deaths individually attributed to radiation. Many survivors suffered radiation-related illnesses, while those alive today continue to experience physical and emotional consequences.
A study by MHD Bahaa Aldin Alhaffar and colleagues, published in 2026 in Scientific Reports, examines the experiences of civilian survivors of the August 2013 sarin attacks in Ghouta, Syria. Interviews with 14 survivors documented self-reported respiratory problems, fatigue, sensory disturbances and neurological complaints, alongside psychological distress and barriers to healthcare. These findings describe survivors’ experiences rather than clinically confirmed diagnoses or estimates for the wider population.
The 2001 anthrax letter attacks in the United States demonstrated how biological attacks can harm civilians beyond their intended targets. Contaminated mail caused 22 cases, including five deaths, affecting postal workers and people in workplaces receiving or processing letters. Consequences extended beyond the initial illness: a study of 15 adult survivors approximately one year later documented persistent health complaints and psychological distress; eight had not yet returned to work.
Current status and challenges
Progress towards disarmament remains uneven.
The Stockholm International Peace Research Institute (SIPRI) estimated that 9,745 nuclear warheads were held in military stockpiles for potential use in January 2026. Meanwhile, the 2026 NPT Review Conference ended without an agreed substantive outcome. A central obstacle was disagreement between the United States and Iran over the final text: Washington insisted on language addressing Iran’s nuclear activities, while Tehran rejected being singled out and objected to the removal of language condemning US–Israeli attacks on its safeguarded nuclear facilities.
In July 2023, the Organisation for the Prohibition of Chemical Weapons (OPCW) confirmed the destruction of all chemical weapons stockpiles declared by member states up to that point. This did not mean that all chemical weapons worldwide had been eliminated. In October 2026, the organisation welcomed the verified destruction of chemical weapons in Syria during August, while stressing the need to locate and eliminate remaining weapons from the former government’s programme.
Biological disarmament faces different challenges, including the absence of a formal verification regime. Dialogues convened by the United Nations Institute for Disarmament Research (UNIDIR) and the BWC Implementation Support Unit explored a proposed scientific advisory mechanism and tools to strengthen transparency, risk assessment and national implementation. These discussions did not establish a new verification system.
Across these areas, protecting civilians requires effective monitoring, international cooperation and accountability. It must also include accessible healthcare, psychological support and rehabilitation for survivors, alongside environmental remediation and sustained funding to help affected communities rebuild their daily lives.
