Hydrogen cyanide (HCN)

HCN, Cyanväte (Vätecyanid)


Hydrogen cyanide (HCN)

CAS no


Molecular formula


 Hydrogen cyanide is a colourless gas or liquid (boiling point of 26°C) with an odour of bitter almond.


Hydrogen cyanide is produced synthetically but is also a by-product of certain combustion processes (for example in coke ovens).

The substance is used in production of synthetic fibres, plastics, pesticides and dyes as well as in chemical synthesis1. Hydrogen cyanide is also used as a pesticide for insects, arthropods and smaller vertebrates and in rat poisoning2.

Hydrogen cyanide is a reaction product of cyanogenic glycosides – a group of toxins that for example exist in certain plants of which some are foods, e.g. cassava, apricot kernels and flax seeds3.

Sources and transportation pathways

Hydrogen cyanide is formed during combustion of materials containing nitrogen, for example nylon, wool, rubber and polyurethane4. The substance also exists in tobacco smoke.

The most important transportation pathway is by air and larger point sources of hydrogen cyanide are for example emissions from metal industry and from different combustion processes.

Effects on environment and health

Hydrogen cyanide is highly poisonous to aquatic organisms and may result in both acute and long-term effects5.

Hydrogen cyanide is also highly poisonous to humans. Ingestion, skin contact or inhalation may be lethal or result in severe poisoning6. Hydrogen cyanide poisoning may cause cramps, unconsciousness, difficulty in breathing and have effects on the heart7.

International agreements and regulations

Hydrogen cyanide is regulated by the EU Water Framework Directive (2000/60/EC). The UN Protocol on PRTRs and the EU E-PRTR regulation regulate how data on hydrogen cyanide emissions is made available.


1 https://www.atsdr.cdc.gov/substances/toxsubstance.asp?toxid=249
2 https://rib.msb.se/Portal/template/pages/Kemi/Substance.aspx?id=2422
3 https://www.livsmedelsverket.se/livsmedel-och-innehall/oonskade-amnen/vaxtgifter/cyanogena-glykosider-och-vatecyanid
4 https://www.msb.se/RibData/Filer/pdf/17521.pdf
5 https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/details/131393
6 https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/details/131393
7 https://rib.msb.se/Portal/Template/Pages/Kemi/Substance.aspx?id=2422&q=cyanv%c3%a4te&p=1