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When I use a word . . . Amending the 1972 Poisons Act – The BMJ

Intended for healthcare professionals
The 1972 Poisons Act was introduced to enable registered pharmacists, under the aegis of the Royal Pharmaceutical Society, to regulate the sale of non-medicinal poisons and subsequently of explosives precursors. Since then it has undergone several amendments, the latest of which is about to come into force (on 1 October 2023), under The Control of Poisons and Explosives Precursors Regulations 2023, which will introduce additional substances into the lists of currently regulated poisons, as well as precursors of explosives, and will add offences relating to their acquisition, importation, supply, possession, and use.
The Oxford English Dictionary (OED) defines “poison” as “Material that causes illness or death when introduced into or absorbed by a living organism, esp[ecially] when able to kill by rapid action and when taken in small quantity; a substance of this kind.”1
One would have expected an act of Parliament that deals with poisons to have included a similar definition.
The 1972 Poisons Act was originally introduced to enable registered pharmacists, under the aegis of the Royal Pharmaceutical Society, to regulate the sale of non-medicinal poisons.2 Since then, and having terrorism in mind, precursors of explosives have been included in its remit.
However, the act does not offer a general definition of a poison. Instead, it defines different types of poison according to how they are regulated under the act:
“A ‘regulated poison’ is a substance listed in Part 2 of Schedule 1A in a concentration higher than the limit (if any) set out for that substance in that Part …”
In other words, it’s a poison if the act says it is. A mixture that contains any such substance is also regarded as a poison. “Reportable poisons” are similarly defined, as substances listed in Part 4 of Schedule 1A. And regulated precursors of explosives are listed in Part 1. There is some overlap in the lists of substances specified in Parts 2 and 4, so here is an abbreviated list that combines the two separate lists from the current version of the act, since it was last amended on 1 November 20183:
● aldicarb (Part 4)
● alpha-chloralose (Part 4)
● aluminium phosphide (Part 2)
● ammonia (Part 4)
● arsenic compounds (Parts 2 and 4)
● barium salts other than barium sulphate (Parts 2 and 4)
● bromomethane (Part 2)
● carbofuran (Part 4)
● chloropicrin (Part 2)
● cycloheximide (Part 4)
● dinitrocresols (Part 4)
● dinoseb and compounds with a metal or a base (Part 4)
● dinoterb (Part 4)
● drazoxolon and its salts (Part 4)
● endosulfan (Part 4)
● endothal (Part 4)
● endrin (Part 4)
● fentin and compounds (Part 4)
● fluoroacetic acid, its salts, and fluoroacetamide (Part 2)
● formaldehyde (Part 4)
● formic acid (Part 4)
● hydrochloric acid (Part 4)
● hydrofluoric acid and other fluorides and bifluorides (Part 4)
● hydrogen cyanide and metal cyanides, other than ferrocyanides and ferricyanides (Part 2)
● lead acetates and compounds of lead with acids from fixed oils (Part 2)
● magnesium phosphide (Part 2)
● mercury, various salts, and some organic compounds (Parts 2 and 4)
● metallic oxalates (Part 4)
● methomyl (Part 4)
● nicotine, its salts, and its quaternary compounds (Part 4)
● nitrobenzene (Part 4)
● oxalic acid (Part 2)
● oxamyl (Part 4)
● paraquat salts (Part 4)
● phenols of various sorts (Parts 2 and 4)
● phosphoric acid (Part 4)
● phosphorus yellow, and various compound of phosphorus (Parts 2 and 4)
● potassium hydroxide (Part 4)
● sodium hydroxide (Part 4)
● sodium nitrite (Part 4)
● strychnine, its salts, and its quaternary compounds (Part 2)
● thallium salts (Part 2)
● thiofanox (Part 4)
● zinc phosphide (Part 4)
The following regulated explosives precursors are listed in Part 1 of Schedule 1A: hydrogen peroxide, nitromethane, nitric acid, potassium chlorate, potassium perchlorate, sodium chlorate, sodium perchlorate, and sulfuric acid.
The act stipulates that “A member of the public can only purchase regulated explosives precursors and poisons with a valid licence.” However, it allows an exemption for “Business to Business sales and substances restricted to professional users.”
Furthermore, “Suppliers of regulated and reportable explosives precursors and poisons are required to report suspicious transactions and significant losses and thefts.”
Now the act is due to be amended again, on 1 October 2023, two days hence, as I write.
In February 2022 the government issued a consultation document, in which were proposed certain amendments to the 1972 act in its current form.4
The consultation was prompted by the perceived need to tighten the regulation of substances, both poisons and precursors of explosives, that might be used by terrorists, while “maintaining a balance for legitimate users.”
The proposals included three options:
1. To do nothing, a normal first option in consultations of this sort.
2. “To strengthen and clarify measures within the legislation, but not change the substances and concentrations that members of the public can acquire, import, possess and use provided they have a valid licence.”
3. To include all the measures proposed under option 2 and in addition to introduce “several new measures to increase security protections.”
The main additional proposals under option 3 were that
(a) upper concentration limits should be increased for some precursors of explosives, for example from 12% to 35% for hydrogen peroxide and from 16% to 100% for nitromethane;
(b) further substances should be added to the lists of reportable and regulated precursors and poisons.
The poisons proposed for addition to Parts 2 and 4 of Schedule 1a were aluminium sulphide, arsenic and mercury compounds, calcium phosphide, calcium sulphide, 2,4-dinitrophenol and derivatives including sodium dinitrophenolate, magnesium sulphide, metal phosphides, metal sulphide, sodium hypochlorite solutions above 6% available chlorine, sodium sulphide, and zinc phosphide.
Option 3 has since been developed into The Control of Poisons and Explosives Precursors Regulations 2023,5 introducing into the Poisons Act additional offences relating to the acquisition, importation, supply, possession, and use of listed substances, and adding the following substances to the current lists of regulated explosives precursors and poisons:
● aluminium sulfide, sodium sulfide, calcium sulfide, and magnesium sulfide
● ammonium nitrate above 16% nitrogen
● arsenic compounds (specifically, calcium arsenites, copper acetoarsenite, copper arsenates, lead arsenates)
● calcium phosphide
● 2,4-dinitrophenol
● hexamine
● hydrochloric acid above 10% w/w
● mercury compounds (mercuric chloride, mercuric iodide, organic compounds of mercury except compounds that contain a methyl group directly linked to the mercury atom)
● phosphoric acid above 30% w/w
● zinc phosphide.
Of these substances, one stands out—dinitrophenol. Dinitrophenol is listed in the consultation document as one of the proposed additions to the list of regulated poisons under the act. However, it is also an explosive, and was used as such during the first world war. It is furthermore unusual, in that it is a rare example of an unlicensed non-medicinal chemical that has been used medicinally.
The story of dinitrophenol is therefore of medical interest, and I shall deal with it in a future column.
Competing interests: None declared
Provenance and peer review: Not commissioned; not externally peer reviewed.
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