Hydrogen Cyanide Toxicity and Environmental Impact Essay


      Hydrogen cyanide (HCN) is considered to be the dominant form of cyanide which is a toxic chemical. It is presented in the forms of  liquid or gas. The colour of liquid is pale blue or it may be defined as colourless gas (See Table 1). The smell of hydrogen cyanide is described as faint bitter almond-like odour. The issue about cyanide toxicity and environmental impact has been widely discussed in the academic sources  because of the concerns about their effects on human health. Today, cyanide is used in various industries, such as the mining industry, the galvanic industry, and the chemical industry (e.g. plastic production). Different industrial operations release cyanides in various forms to the environment. Also, cyanide can be found in the natural environment, namely in the seeds of plants (e.g. apricot kernels, cassava roots and bamboo shoots), known as cyanogenic glycosides. If people consume them in large amounts, they will have negative side effects. One of the key sources of cyanide is environmental tobacco smoke (ETS). Researchers found that “live organisms have the ability to convert cyanide into less toxic compounds excreted with physiological fluids” (Jaszczak, Polkowska, Narkowicz & Namiesnik, 2017, p.15929). The review of academic sources shows that hydrogen cyanide is the so-called systemic poison because its toxicity occurs as a result of is inhibition of cytochrome oxidase, which leads to prevention of the proper utilization of oxygen by cells. This paper will discuss the current state of knowledge on hydrogen cyanide (HCN)  and the impact of this chemical compound on the environment and human health.

Overview of the Sources of Human and Environmental Exposure

      Hydrogen cyanide is produced in the result of two different synthetic catalytic processes that involve the reaction of two elements, namely ammonia and natural gas, either with or without air. Researchers found that hydrogen cyanide is “also obtained as a by-product in the production of acrylonitrile by the ammoxidation of propylene, which accounts for approximately 30% of the worldwide production of hydrogen cyanide” (World Health Organization, 2004, p. 9). The production of hydrogen cyanide involves incomplete combustion of different polymers which contain nitrogen, including wool, plastics, and polyurethanes. The presence of hydrogen

cyanide in cigarette smoke is found in high concentrations (World Health Organization, 2004).


Table 1

Chemical and Physical Data

Parameter Value Reference
Synonyms Formonitrile, hydrocyanic acid, prussic acid ACGIH 1996
Molecular formula HCN Budavari et al. 1996
Structure H−C≡N ATSDR 1997
Molecular weight 27.03 Budavari et al. 1996
CAS registry number 74–90–8 ACGIH 1996
Physical state Gas or liquid Budavari et al. 1996
Color Colorless gas, bluish-white liquid Budavari et al. 1996
Solubility in water Miscible Budavari et al. 1996
Vapor pressure 807 mm Hg at 27°C Hartung 1994
Vapor density (air=1) 0.941 Budavari et al. 1996
Liquid density (water=1) 0.687 Budavari et al. 1996
Melting point −13.4°C Budavari et al. 1996
Boiling point 25.6°C Budavari et al. 1996
Odor Bitter almond Ruth 1986
Conversion factors 1 ppm=1.10 mg/m3
1 mg/m3=0.91 ppm
ACGIH 1996

This table shows that hydrogen cyanide is also known as Formonitrile, hydrocyanic acid, and prussic acid. As the melting point of hydrogen cyanide is −13.4°C and 25.6°C, there is a need for considering the effects of different environmental conditions on this chemical compound, while drawing conclusions on its impact on human health and wildlife (See Table 1).

The Impact of Hydrogen Cyanide on the Environment

      The impact of hydrogen cyanide on the environment is adverse. As a rule, the ions of cyanide are found in the atmosphere in the form of hydrogen cyanide (HCN). The emergence of this chemical in the air is connected with the growth of industrial activities, as well as the result of fires in industrial areas and apartments. Those people are exposed to poisoning caused by this chemical include fire-fighters and workers employed at the mining, metallurgical, chemical, and galvanic industries (Jaszczak et al., 2017). Researchers found that “Hydrogen cyanide is a product of combustion of synthetic polymers, wool and silk; additionally, it is produced during the combustion of fuels in automobile engines as a result of catalytic reduction of nitrogen oxides” (Jaszczak et al., 2017, p. 15929). As the concentration of HCN is increased in the exhaust gas only in the absence of catalyst, this chemical is less harmful than other forms of cyanide.


Table 2

Literature information on cyanide concentrations in different environmental samples

Type of sample Source of sample Concentration References
 Outdoor air Lower atmosphere 0.36 ± 0.16 ppbv Ambose et al. (2012)
  Atmosphere 333 ± 44 pptv (summer) Zhao et al. (2000)
    195 ± 16 pptv (winter)  
  Lower stratosphere 233.5 ± 160.6 ppt Singh et al. (2003)
    280 ± 4 pptv Viggiano et al. (2003)
  Stratosphere 164 pptv Scheneider et al. (1997)
  Gold field 0.76 ppb Orloff et al. (2006)
  Vehicular emissions 654 t/year Moussa et al. (2016)
  Vehicular emission 0.45 mg/km Karlsson and Botz (2004)
 Indoor air Vehicular exposure in garage 0.32 μg/m3  Karlsson and Botz (2004)
  Air in car 14–20 ppm Mangnusson et al. (2012)
  Fire 1.8 ± 3 mg/kg Paton-Walsh et al. (2010)
Tobacco smoke
 Cigarette China 125.2 μg/cig. Zhang et al. (2011)
  Spain 6.6 μg/ cig. Marcilla et al. (2012)
  Russia 27 μg/cig. Ashley et al. (2014)
  CAMEL Lights 184.825 μg/cig. Mahernia et al. (2015)
  Marlboro Gold (Germany) 165.871 μg/cig.  
  Marlboro Extra (USA) 164.309 μg/cig.  
  Marlboro Lights (Switzerland) 69.344 μg/cig.  
  Winston Blue (Europe) 99.244 μg/cig.  
  Switzerland 4.1 ng/cig. Mottier et al. (2010)
  China 98.38 μg/cig. Xu et al. (2006)
 Surface water Korea (Gum River) 1.01 ± 0.03 μg/L Kang and Shin (2014)
  0.77 mg/L Dadfarnia et al. (2007)
  Brazil 25–50 μg/L Frizzarin and Rocha (2013)
  China Wan et al. (2015)
  Italy 5.11 μg/L Giuriati et al. (2004)
 Drinking water USA (Sunnyvale) <LOD Christinson and Rohrer (2007)
  USA (San Jose) <LOD  
  Sweden Themelis et al. (2009)
  Iran <LOD Absalan et al. (2010)
 Tap water Iran 0.6 μg/L Abbasi et al. (2010)
  Petrochemical sludge 6.1–63.5 μg/L Dadfarnia et al. (2007)
  Electroplating waste 0.04–1.2 μg/mL Hassan et al. (2007)
  Petrochemical sludge 4600.2 μg/L Abbasi et al. (2010)
  Gold cyanidation solution 540 mg/L Breuer et al. (2011)
  Industrial wastewater Noroozifar et al. (2011)
  Japan 0.060 mg/L Matsumura and Kojima (2003)
  Coking plant sites (Germany) 32.8 ± 1.44 mg/kg Mansfeldt and Biernath (2000)
  Coking plant sites (France) 46.5 ± 14.5 mg/L Manar et al. (2011)
  Goldmine (Tawurbiek, China) 70.55 μg/g Shehong et al. (2005)
  Coking plant sites (Germany) 0.14 mg/L Rennert and Mansfeldt (2006)
  Gold mine (Brazil) 0.83–1.44 mg/kg Prereira and Sousa Neto (2007)
Mine site (USA)
<0.01 mg/kg Sims and Francis (2008)
Fresh food
 Kernel/seed Apple 2.80 ± 0.02 mg/kg Ma et al. (2010)
    690 ppm Haque and Bradbury (2002)
    1–3.9 mg/g Bolarinwa et al. (2015)
  Apricot 1.88 ± 0.07 mg/kg Ma et al. (2010)
    785 ppm Haque and Bradbury (2002)
    14.37 ± 0.28 mg/g Bolarinwa et al. (2014)
  Peach 710 ppm Haque and Bradbury (2002)
  Nectarine 196 ppm  
  Plum 696 ppm  
  Bean 1.76–1.77 mg/kg Chove and Mamiro (2010)
  Millet 2.11–2.14 mg/kg  
  Lensed 390 ppm Haque and Bradbury (2002)
  Rubber tree Abdullah et al. (2013)
  Nuts Chove and Mamiro (2010)
  Plum 247 mg/100 g Surleva and Drochioiu (2013)
  Almond 7.4 μg/100 g  
  Apple 108 mg/100 g  
  Flax 7.3 mg/100 g  
 Leaf Sorghum 750 ppm Haque and Bradbury (2002)
  Alocasia macrorrhizos 29 ppm  
  Spinach 2.51 ± 0.6 μg/g Kuti and Konoru (2006)
    1.28 ± μg/g  
  Chokecherry 4.7–15 mg/kg Pentore et al. (1996)
  Bamboo 1010 ppm Haque and Bradbury (2002)
  Grapevine 123–329 mg/kg Franks et al. (2005)
 Root Manioc 27 ppm Haque and Bradbury (2002)
Processed food
 Liquor Cherry 1 ng/mL Wu et al. (2015)
 Juice Apple juice 0.003 mg/mL Bolarinwa et al. (2015)
 Marzipan   0.02 mg/g Bolarinwa et al. (2014)
 Flour Manioc 43 ± 20 ppm Haque and Bradbury (2002)
    232 ± 10 mg/kg Tivana et al. (2014)
    2.3 mg/kg Kalenga Saka and Nyirenda (2012)
  Garri 16.7 ppm Bradbury (2009)

      This table shows research findings taken from reliable academic sources on cyanide concentrations in different environmental samples, including air, tobacco smoke, water, soil, and food. The analysis of these findings show that the highest concentration of this chemical is found in tobacco smoke (China, Germany and USA), while the lowest concentration – in drinking water (USA, Sweden, Iran). The analysis of the findings taken from research studies  on other environmental  samples shows that soil is another source of cyanide concentration that is generated by the effects of galvanic and metallurgical industrial operations (See Table 1).  The highest concentrations of cyanide are found in wastes generated by underground coal gasification. In soil, there is no light, therefore, hydrogen cyanide is less toxic. In food, the presence of cyanogenic glycosides in plants can lead to poisoning of a person who consumes  this food in high amounts. The amount of  hydrogen cyanide in processed food is lower than that in the plant seeds (See Table 1).

            In recent study, researchers identified the adverse impact of high concentration of hydrogen cyanide in soil on wildlife. The fact that cyanide is extracted of gold through milling processes of high grade ores and heap leaching processes of low grade ores means that soil is contaminated at these industrial settings. Both soil and water may contain high concentrations of potentially toxic hydrogen cyanide which affect wild animals. Cyanide poisoning of aquatic animals is the result of improperly regulated industrial processes that fail to prevent contamination of  industrial and municipal waste waters. There are other sources of hydrogen cyanide contamination that affect wildlife and the environment, namely electroplating processes,

metal finishing, metallurgy, steel processing, and petroleum industrial processes (Egekeze & Oehme, 1980). Also, bacterial cyanogenesis is considered to be damaging to animals and plants because of hydrogen cyanide production. Researchers suggest that “hydrogen cyanide (HCN), a potent inhibitor of cytochrome c oxidase and of other metal-containing enzymes, might be responsible for the observed plant-killing effects” (Biom, Fabbri, Eberi, Weisskopf, 2011, p. 1000).

The Impact of Hydrogen Cyanide on Human Health

            The impact of hydrogen cyanide on human health is negative because breathing of even small amounts of this gas often causes severe headache, dizziness, body or muscle weakness, nausea, confusion, and vomiting. Research studies show that breathing larger amounts of this gas often leads to gasping, irregular heartbeats, seizures, fainting, and even death. In other words, the level of exposure to hydrogen cyanide causes more complicated symptoms (Agency for Toxic Substances & Disease Registry, 2019). As hydrogen cyanide is defined as a highly toxic chemical, considering practically all routes of exposure to it in the natural environment, people should be protected from its negative effects on human health. Experts in toxicology assume that

hydrogen cyanide may “cause abrupt onset of profound CNS, cardiovascular, and respiratory effects, leading to death within minutes” (Agency for Toxic Substances & Disease Registry, 2019). Also, hydrogen cyanide can serve the role of a cellular asphyxiant, which ensures prevention of the use of oxygen in the process of cellular metabolism, if it is bound to mitochondrial cytochrome oxidase (Agency for Toxic Substances & Disease Registry, 2019).

Human body starts to alter cyanide into thiocyanate,  which prevents cells from utilizing oxygen leading to death of cells. As a result of these processes, the heart, the respiratory system and the central nervous system become susceptible to poisoning (Agency for Toxic Substances & Disease Registry, 2019).

            Actually, researchers point out to the adverse effects of industrial production that contains high amounts of cyanogenic glycosides, which are known to act as potential hydrogen cyanide  releasers. This fact means that the increased health concerns are associated with occupational exposure to this chemical compound. The example of this source of exposure is the sector of cassava processing. In recent study, researchers investigated health of workers involved in the  cassava processing and found that all of them were exposed to poisoning caused by high concentration of hydrogen cyanide in the air. Researchers also found that “large scale of Cassava processing could be disastrous due to discharge of hydrocyanic acid into the air” (Dhas, Chitra, Jayakumar, & Mary, 2011, p. 13). This fact means that cassava processing is an industrial activity that damages human health. In another study, researchers proved the harmful effects of hydrogen cyanide caused by fire-fighters’ multiple exposure to smoke. The reported symptoms were consistent with cyanide poisoning and included severe headaches, weakness and fatigue, nausea, and shortness of breath (World Health Organization, 2004).


Figure 1

Clinical symptoms of hydrogen cyanide poisoning 

      The overview of the key symptoms of hydrogen cyanide poisoning were found in workers exposed this chemical compound for a rather long period of time (over 5 years). These symptoms indicate the level of severity of poisoning (See Fig. 1).

As the impact of hydrogen cyanide on human health is adverse, special attention should be paid to the proper measures that can help to address this problem and eliminate exposure to poisoning.  Due to regular occupational health interviews, assessments, and physical examinations, it is possible to ensure safety in the workplace. According to researchers, medical screening tests can be useful in identification of the adverse effects of hydrogen cyanide on human body in general (Dhas et al., 2011).


            In conclusion, this paper discussed various impacts of hydrogen cyanide. Relatively low concentrations of this chemical compound are assessed by researchers as highly toxic to human health and the natural environment, mainly to wildlife. Both liquid or gaseous hydrogen cyanide can enter the human body through different ways, including  inhalation, ingestion, or absorption through the skin or eyes. In general, exposures to this chemical compound occur in industrial settings as well as from tobacco smoke, the processes of combustion of products, and in foods presented in the form of naturally occurring hydrogen cyanide compound.


Agency for Toxic Substances & Disease Registry. (2019). Toxic Substances Portal – Hydrogen Cyanide. Retrieved from:<https://www.atsdr.cdc.gov/MMG/MMG.asp?id=1141&tid=249>

Biom, D., Fabbri, C., Eberi, L., Weisskopf, L. (2011). Volatile-Mediated Killing of Arabidopsis thaliana by Bacteria Is Mainly Due to Hydrogen Cyanide. Applied and Environmental Microbiology, 77(3): 1000-1008. doi:10.1128/AEM.01968-10

Dhas, P. K., Chitra, P., Jayakumar, S. & Mary, A. R. (2011). Study of the effects of hydrogen cyanide exposure in Cassava workers. Indian Journal of Occupational and Environmental Medicine, 15(3): 13-136. doi: 10.4103/0019-5278.93204

Egekeze, J. O. & Oehme, F. W. (1980). Cyanides and Their Toxicity: A Literature Review.         Veterinary Quarterly, 2(2): 104-114. doi: 10.1080/01652176.1980.9693766

Jaszczak, E., Polkowska, Z., Narkowicz, S. & Namiesnik, J. (2017). Cyanides in the environment – analysis – problems and challenges. Environmental Science and Pollution Research International, 24(19): 15929–15948. doi:10.1007/s11356-017-9081-7

World Health Organization. (2004). Hydrogen Cyanide and Cyanides: Human Health Aspects. Concise International Chemical Assessment Document 61. Retrieved from:<https://apps.who.int/iris/bitstream/handle/10665/42942/9241530618.pdf>   

The terms offer and acceptance. (2016, May 17). Retrieved from

[Accessed: November 27, 2021]

"The terms offer and acceptance." freeessays.club, 17 May 2016.

[Accessed: November 27, 2021]

freeessays.club (2016) The terms offer and acceptance [Online].
Available at:

[Accessed: November 27, 2021]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: November 27, 2021]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: November 27, 2021]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: November 27, 2021]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: November 27, 2021]
Haven't found the right essay?
Get an expert to write you the one you need!

Professional writers and researchers


Sources and citation are provided


3 hour delivery