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An examination of the precursor chemicals used in the manufacture of explosive compositions found within Improvised Explosive Devices (IEDs)

Chapter 4:The Regulation

International controls on explosive precursors vary by Member State. The regulation currently in place can be discussed in three broad approaches: International, Regional and National. This paper examines existing regulation against the precursors, fuels and oxidizers identified in Table 1.


To enhance public safety the security of global supply chains is governed by Programme Global Shield (PGS)[8], a partnership between the World Customs Organisation (WCO), the International Criminal Police Organization (INTERPOL) and the United Nations Office on Drugs and Crime (UNODC). The programme aims to enhance awareness and information sharing on the global movement of the most common9 chemical precursors used in IED manufacture to prevent their diversion, illegal shipment, promote international cooperation and provide awareness to industry and other groups. Today, customs administrations from >90 countries share this information and enable participants and partners to be better equipped to interdict illicit diversion in the supply chain. The Annual Illicit Trade Report (AITR) is one method by which progress is reported.

Information on HME is also routinely transferred within the International Bomb Data Centre Working Group (IBDCWG), which consists of >40 member nations and 12 observer countries. The roles and functions of each Member State’s bomb data centre varies but all members are legitimate government agencies responsible for the management of technical intelligence and information related to the unlawful use of explosives.

Comment: A cursory glance at the PGS fixed list accounts for a small percentage of the precursors listed in Table 1, affording the perpetrator space for manoeuvre. Additionally, many of these chemicals are used on a global scale and diversion once at the end user is difficult to control – it relies on the end user’s compliance, awareness within law enforcement and a lack of corruption. For example, UN embargo monitors first flagged al-Shabaab’s escalating use of commercial precursors in domestic IED production in 201610. Al-Shabaab had infiltrated and gained covert access to the manifests of legitimate cargo vessels and was able to prosecute successful seizure operations of potassium chlorate. Hazards or potential use may also be poorly understood.

A soldier of the African Union Mission in Somalia (AMISOM) keeps guard inside the seaport of the Somali capital Mogadishu, August 2012. AU-UN IST PHOTO / STUART PRICE (CC0 1.0).

Thousands of tonnes of urea fertilizer sit in ports globally – this can be used to make urea nitrate (similar properties to AN); 2750 metric tonnes AN deflagrated to detonation in Beirut port last year and is used in over 60% of IEDs given the successful illicit diversion of AN fertilizer.

The United Nations has also widely raised awareness this past five years, specifically with the adoption of General Assembly First Committee resolutions, which integrate the issues of IEDs into broader discussions on peace and security, enabling the arms control and disarmament community to consider their destabilising impact and to agree on steps to reduce their effect. Examples of UN awareness raising are:

  • Support for the PGS initiative has been further noted by the UNGA, which recognizes the initiative’s important role in preventing the smuggling and illicit diversion of precursor chemicals [11]
  • Fourth Committee continues to address the issues of IEDs in Mine Action in accordance with International Humanitarian Law (IHL);
  • The Convention on Certain Conventional Weapons (CCW) Review Conference offers the opportunity for High Contracting Parties to take several actions to increase their engagement on IED issues and which re-affirms national commitments;
  • The Secretary General now issues an annual report on countering IEDs, most recent reports highlighting precursors specifically. In such reports the Secretary General identifies the step-change by which precursors are used and the subsequent actions required:
    • engagements with the private sector to stem the flow of dangerous precursor material or components;
    • empowerment of WCO, INTERPOL and UNIDIR to deepen research and expand data collection;
    • for UNDP/UNMAS to provide capacity development support from within their mine action programmes in order to help in preventing illegal access to explosive precursor material;
    • encourage Member States to further integrate security-related mandates into customs and border control activities with a view to preventing the diversion of precursor chemicals.

“Lebanon: the EU’s response to the tragic explosions in Beirut” by EU Civil Protection and Humanitarian Aid (CC BY-NC-ND 2.0).

The Secretary General has also supported the formation of a Global IED Task Force [12], which draws on the experience of all UN agencies involved in the fight against IEDs. Whilst this task force is in its infancy, its reach in terms of assisting and advising Member States in upstream and downstream capacity development initiatives can be seen in Figure 2.

Additionally, UNIDIR has completed research on C-IED threat mitigation and launched the C-IED Capability Assessment Maturity Model on 24th June 2020 [13], having piloted it in Yemen between August 2019
and February 2020. This model embraces the intent of the Global IED Task Force and allows Member States to assess their ability to counter the threat posed by IEDs. The use of precursors is specifically mentioned in ‘Upstream Capacity Building Measure 6 [Control of IED Precursors]’, which assists a State to recognize that certain materials may be misused in the manufacture of HME, how licensing and regulation might be applied, and that exploitation of recovered IED components can assist the protection of communities and improve information flow to entities such as border forces. This initiative should be socialised with all Member States and further pilot programmes considered across IED affected regions.

Recommendations: The potential of the Global IED Task Force and UNIDIR model need to be socialised more broadly with Member States. Exploitation of recovered IED components assists in the protection of communities and improves information flow/understanding. HMA organisations may wish to consider whether their stance on this issue aligns with a Human Rights Based Approach.

Typical 20kg Plastic Jug exposed above the ground surface due to swelling of the HME. Photo: BCL-RO.


The approach adopted by the European Union (EU) is to categorize certain chemicals. In summary, “restricted explosives precursors” are not generally available to members of the public and their acquisition is subject to control and (possibly) licensing. For “reportable explosives precursors”, the emphasis is placed at online and offline retail, as well as online marketplaces, to report suspicious transactions. Specific detail lies within Regulation (EU) 2019/1148 of the European Parliament and of the Council [14]. The criteria for determining which measures should apply include:

  • the level of threat associated with the explosive precursor concerned;
  • the volume of trade in the explosive precursor concerned;
  • and whether it is possible to establish a concentration level (threshold) below which the explosive precursor could still be used for the legitimate purposes it was intended, but making it less likely to form a viable HME.

(EU) 2019/1148 does not permit the general public to acquire, introduce, possess or use certain explosives precursors at concentrations above certain limit values, expressed as a percentage with water (% w/w). However, members of the general public are permitted to acquire, introduce, possess or use some explosives precursors at concentrations above those limit values for legitimate purposes, provided that they hold a licence to do so. This is an entirely sensible approach, all EU states have signed up to it, including former members (such as the UK), who have incorporated updates within their own legislations.

Table 2 summarises the EU legal concentration limits (thresholds) for precursors where access by the general public is required. The general public is not granted access unless the concentration is equal to or lower than the standard limit value.

(EU) 2019/1148 also requires that large scale or suspicious transactions/thefts of the precursor chemicals shown in Table 3 be reported within 24 hours.

Similar to PGS, the EU approach covers a limited percentage of chemicals known to be used in IED manufacture, but is not necessarily aligned to the same series of chemicals as the PGS.


Many countries, Member States and Unions have their own national legislation to mitigate the threat posed by precursors. These are too numerous to mention but are a force for good when combined with PGS, the IBDCWG, Project Watchmaker [16] and the eleven regional intelligence liaison officers of the WCO, which facilitate the exchange of intelligence across all six WCO regions [17]. However, most recent developments on the national level have taken place in the US where the Department for Homeland Security (DHS) has been hugely proactive in conjunction with the National Academy of Sciences (NAS) in an attempt to augment/update previous precursor-related initiatives such as Chemical Facility Anti-Terrorism Standards (CFATS 2007).

Such proactivity established a committee of cross- government experts to prioritize precursor chemicals and substances, analyse their movement through the national supply chain, examine national/international legislation and regulations pertaining to precursor chemicals, and identify potential control strategies. The committee’s final report18 provides an excellent reference for potential mitigation strategies, which are adaptable in response to a variety of threats, specifically vehicle-borne and person-borne IEDs (VBIED and PBIED), which have killed and injured more civilians than any other IED system. In the report, three specific criteria are examined: can the precursor be used in VBIED and PBIED; does the precursor have a history of use in IED attacks (looking back over the past 50 years)[19]; can the precursor be used to make viable HME independent of the presence of another specific chemical.

On that basis, three groups of precursors have been established by the committee (see Annex E):

  • Group A – chemical precursors that satisfy all three criteria;
  • Group B – chemical precursors that satisfy 2 of the 3 criteria;
  • Group C – chemical precursors that satisfy one of the 3 criteria.

Whilst Group A precursors are the ones where US national effort is principally focused, the precursors listed in Groups B and C provide a degree of predictive threat analysis whereby restrictions imposed on Group A would force perpetrators to change approaches over time. As such, the study conducted by NAS provides a degree of readiness, a form of good practice if you will, but also underpins the growing need for greater international collaboration.

Comment: The NAS varies with Table 1 and precursors / oxidizers used effectively in HME compositions outside the US have not been fully listed.

Recommendation: That the NAS approach be considered a template for any formal discussions on a global implementation strategy for restriction, substitution and standardization of precursor chemicals.

Suicide vest (person-borne IED), Iraq.

Chapter 5: Analysis

Read the full report here