All substances are poisons - the difference is in the dose' 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. Chemical hazards in the workplace and in the environment People may be exposed to a range of toxic chemicals at work or in the general environment. 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.