The above aphorism is attributed to Paracelsus. It illustrates that the potential for harm is widespread and all chemicals could be toxic but the degree of harm that a chemical can inflict on a human or any other living being depends on the dose or the degree of exposure as well as on other factors.
This account is intended for those with little or no background in toxicology. Toxicology is a complex and difficult science. In an attempt to make it more understandable, many broad generalisations are made, without detailing the mechanisms or addressing the exceptions. This page must therefore be interpreted cautiously.
|Metals, and metalloids||arsenic, cadmium, lead, mercury, nickel, tin, etc|
|Inorganics (other)||asbestos, carbon monoxide, hydrogen sulphide|
|Hydrocarbons - aliphatic||propane, butane, pentane, hexane|
|Aliphatic alcohols, ketones, ethers, aldehydes and acids||ethyl alcohol (ethanol), acetone, diethyl ether, formaldehyde, acetic acid|
|Hydrocarbons - aromatic||benzene, toluene, xylene, naphthalene|
|Chlorinated volatile organic compounds||perchlorethylene (tetrachloroethene), trichloroethylene (trichloroethene), vinyl chloride|
|Chlorinated non volatile organic compounds||chlorinated dioxins and dibenzofurans, polychlorinated biphenyls, pesticides such as chlordane and DDT|
|Miscellaneous organic compounds||acrylonitrile, benzidine, aniline, di-isocyanates, organophosphates|
|The exact chemical identity (the 'species') of a substance can make
a very big difference as regards its toxicity. This concept is called 'speciation'.
For example asbestos is a complex chemical compound containing atoms such as potassium, sodium, magnesium, aluminium, silicon and others which in a different context would have a much lower toxicity than they exhibit in the compound of asbestos.
Chromium in the hexavalent state (Cr VI) is a human carcinogen (as in the orange coloured potassium dichromate or bichromate) while trivalent chromium (Cr III) (as in the green coloured chromium III chloride) appears not to be. If the chromium is in the Cr III form and oxidation to Cr VI is prevented, exposure should present no cancer risks.
Nickel tetracarbonyl (Ni(CO)4) is a highly toxic gas inflicting severe damage to the lungs and heart, while nickel carbonate (NiCO3) is a solid which is much less hazardous. Metallic nickel probably poses no cancer risk at all while nickel subsulphide is almost certainly a very highly carcinogenic and dangerous compound which has been responsible for many sad deaths.
- or how the body handles poisons
Absorption into the body
Distribution within the body
Metabolism/ biotransformation of toxic substances
Routes of elimination of toxic substances / or their metabolites
- or what poisons may do to the bodyA note on terminology:
More serious inflammation:
Narcotic and anesthetic effects:
Other effects on specific organs:You may wish to refer to another resource on specific organ damage, but here are some other points:
These provoke an immune response (sensitisation) resulting in asthma, rhinitis, allergic dermatitis e.g. diisocyanates, glutaraldehyde, nickel
e.g. vinyl chloride causes hepatic haemangiosarcomas, benzene is a genotoxic carcinogen. Occupational exposures to high concentrations of benzene have shown to increase the likelihood of an individual developing leukaemia; the added risk incurred as a result of being exposed to 1 ug/m3 of benzene for a lifetime is about 4 X 10-6.
Other effects on DNA:
Through the practice of good occupational hygiene