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Hydrocarbon toxicity

Last updated: August 31, 2021

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Hydrocarbons are a large class of organic compounds composed solely of hydrogen and carbon, all of which can be toxic if inhaled or ingested. Hydrocarbons have a wide range of household and industrial applications, especially as fuels (e.g., gasoline), solvents (e.g., turpentine), and lubricants (e.g., mineral oil). Chlorinated and aromatic hydrocarbons have a particularly severe toxicity and their occurrence is generally restricted to industrial uses. At low doses, exposure to household hydrocarbons may manifest with coughing, nausea, vomiting, signs of hypoxia, signs of CNS depression, and other neurological symptoms such as agitation, hallucinations, and tremors. High doses can cause potentially fatal arrhythmias. Chronic exposure may cause rashes, peripheral neuropathy, chronic headaches, and cognitive impairment. Chlorinated and aromatic hydrocarbons may furthermore cause severe symptoms already in acute exposure and at relatively low doses, including chloracne (a hallmark of dioxin toxicity) and other dermatological manifestations (e.g., skin irritation, hirsutism, skin pigmentation), loss of consciousness, numbness, and decreased immune response. In chronic exposure or at high doses, they may have nephrotoxic, hepatotoxic, neurotoxic, carcinogenic, and teratogenic effects. Industrial accidents have led to severe effects in the general population including in Vietnam, via contamination of Agent Orange with TCDD and the contamination of rice bran oil in Kyusho, Japan, with PCB in 1968 (Yusho disease).

Polychlorinated substances

Polychlorinated dibenzodioxins (dioxins; PCDDs) and polychlorinated dibenzofurans (PCDFs)

  • Overview
    • Not commercially produced; mostly byproducts in the manufacture of other chemicals (e.g., PCBs, pesticides), combustion processes (e.g., waste incineration, automobile emissions), or organic decomposition (e.g., compostation, sewage)
    • Very stable, lipophilic compounds that are absorbed via contaminated foods, mainly of animal origin (e.g., beef, dairy products, and chicken), or via environmental exposure, mainly as an occupational hazard involving inhalation or skin contact
    • Accumulate in fatty tissue and, therefore, eventually reach toxic levels with continued exposure to even small amounts
    • Almost all PCDDs and PCDFs are classified as probable human carcinogens (group 2A carcinogens)
  • Examples
  • Clinical features

Chloracne is a hallmark symptom of dioxin toxicity.

Polychlorinated biphenyls (PCBs)

  • Overview
    • Formerly used in coolants and insulators for transformers and electrical capacitors, hydraulic fluids, as plasticizers for paints and plastics, and as sealants for caulking
    • Manufacturing was banned in the US in 1979.
    • Very stable, lipophilic compounds that are absorbed via contaminated foods, mainly of animal origin (e.g., beef, dairy products, and chicken), or via environmental exposure, mainly as an occupational hazard involving inhalation or skin contact
    • PCBs are mainly released into the environment from waste (e.g., electrical transformers, PCB-containing consumer products)
    • Classified as probable human carcinogens (group 2A carcinogens)
  • Examples: 3,3′,4,4′-tetrachlorobiphenyl, 3,3′,4,4′,5-pentachlorobiphenyl [2]
  • Clinical features
    • Acute toxicity
      • Yusho disease : In 1968 in northern Kyushu, Japan, PCB-contaminated rice bran oil was sold to poultry farmers and consumers, resulting in a mass poisoning of about 14,000 people and the death of 400,000 birds. [3]
    • Chronic toxicity [4]

Chlorinated alkenes

Chlorinated aromatic compounds

  • Overview
    • Used in the production of herbicides, pesticides, and rubber
    • Classified as group D carcinogen (i.e., not classifiable as to human carcinogenicity due to limited data)
    • No information available regarding developmental and/or reproductive effects
  • Examples: chlorobenzene, chlorophenol
  • Clinical features [6]
    • Acute toxicity: loss of consciousness, muscle spasms
    • Chronic toxicity: neurotoxicity (e.g., numbness, hyperesthesia, muscle spasms)
  1. Occupational chloracne. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/224136/occupational-chloracne-report-iiac.pdf. . Accessed: August 26, 2021.
  2. Table of PCB Species by Congener Number. https://www.epa.gov/sites/default/files/2015-09/documents/congenertable.pdf. . Accessed: August 26, 2021.
  3. Onozuka D, Nakamura Y, Tsuji G, Furue M. Mortality in Yusho patients exposed to polychlorinated biphenyls and polychlorinated dibenzofurans: a 50-year retrospective cohort study. Environmental Health. 2020; 19 (1). doi: 10.1186/s12940-020-00680-0 . | Open in Read by QxMD
  4. Learn about polychlorinated biphenyls (PCBs). https://www.epa.gov/pcbs/learn-about-polychlorinated-biphenyls-pcbs#tradenames. . Accessed: August 26, 2021.
  5. Risk management for short-chain chlorinated paraffins. https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/risk-management-short-chain-chlorinated-paraffins. . Accessed: August 26, 2021.
  6. Vinyl Chloride. https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/vinyl-chloride. Updated: December 28, 2018. Accessed: August 26, 2021.
  7. Chlorobenzene. https://www.epa.gov/sites/default/files/2016-09/documents/chlorobenzene.pdf. . Accessed: August 26, 2021.
  8. Boström C-E, Gerde P, Hanberg A, et al. Cancer risk assessment, indicators, and guidelines for polycyclic aromatic hydrocarbons in the ambient air.. Environ Health Perspect. 2002; 110 (suppl 3): p.451-488. doi: 10.1289/ehp.110-1241197 . | Open in Read by QxMD
  9. Nadia Benmoussa, John-David Rebibo, Patrick Conan, Philippe Charlier. Chimney-sweeps' cancer—early proof of environmentally driven tumourigenicity. Lancet Oncol. 2019; 20 (3): p.338. doi: 10.1016/s1470-2045(19)30106-8 . | Open in Read by QxMD
  10. Cancer in Illinois Resources - Polycyclic aromatic hydrocarbons (PAHs). http://www.idph.state.il.us/cancer/factsheets/polycyclicaromatichydrocarbons.htm. . Accessed: August 26, 2021.