By John Timbrell
Now not every thing artifical is risky, and never every little thing traditional is secure. Timbrell's exploration of the darkish aspect of chemistry, written for a lay viewers, is either creepy and academic, laying out how, while, and why chemical substances of every kind are toxic. His objective, he writes, is to assist readers type throughout the conflicting and unsettling info that surrounds us all to allow them to higher make up their very own minds and stability hazards opposed to advantages. He seems at industrially established situations, similar to Bhopal and Minimata, in addition to pollution within the wildlife, together with that toxic delicacy the puffer fish and the plant fungus that ended in the Salem witch trials. Timbrell teaches biochemical toxicology at King's collage, London.
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Extra resources for Poison Paradox: How and When Chemicals Are Toxic
If there is an error (known as a mutation) in the DNA code that holds the information, the enzyme (protein) that is produced may be faulty. Mutations occur naturally and are passed on from one generation to the next. Some are benign, others potentially lethal. An example of this is the mutation that causes the disease haemophilia, which was carried by Queen Victoria and which aﬄicted various male members of the royal families of Europe who were descended from her. If a mutation results in the production by the body of a faulty enzyme, then the metabolic processes catalysed by that enzyme will either not occur or occur only slowly.
The internal or real dose of a chemical may be very small even if the amount swallowed or inhaled is large. This is because some chemicals (including some drugs) are very poorly absorbed. However, this is not the only reason that some chemicals are of low toxicity. The internal dose of the chemical may be detoxiﬁed very quickly by metabolism, be absorbed into fat, be bound to some other molecule, or just be excreted rapidly. But as the external dose rises so does the internal dose and a point may be reached where the detoxiﬁcation or excretion processes are overwhelmed.
For example, exposure to organophosphate insecticides causes an increase in the level of a substance called acetylcholine which occurs naturally in the body and is involved with the function of certain nerves (it is a neurotransmitter; see Figure , p. ). Acetylcholine aﬀects receptors in other tissues such as the lungs, as well as the nervous system. As will be explained in Chapter , toxic doses of organophosphates cause unnaturally large amounts of acetylcholine to accumulate, causing the airways to contract, hence people exposed to it will experience diﬃculty in breathing (and a variety of other eﬀects).