How DDT works and why it is toxic to insects but not mammals

The mechanism by which DDT acts is to disturb the function of nerves in the insect. Nerves in both insects and humans work by allowing an electric current to move down them. This action potential, as it is called, depends on the movement of two metal ions, sodium and potassium, across the membrane of the nerve, and involves channels for the sodium being opened very briefly. DDT interacts with the sodium channel in the insect nerve and retards its closure. This means that the flow of sodium and...

Symptoms and detection of strychnine poisoning

The effects of strychnine usually appear rapidly, within ten to fifteen minutes. As with most poisoning cases, the victim appears to be well and in good health, and then suddenly falls ill following the eating or drinking of something or the taking of a preparation or medication. Within minutes the victim will complain of stiffness, often in the back of the neck. Tremor and twitching start, followed by convulsions. Occasionally there is only one massive convulsion before death, but usually...

Types of food additives

Preservatives are substances added to food to prolong their shelf life. They prevent or reduce bacterial or fungal growth. Examples of preservatives are salt, nitrites, sulphur dioxide, propionate, and benzoate. Antioxidants are added to oils and fats to stop them going rancid because of oxidative damage. They may also be added to fruits and vegetables. Examples of antioxidants are butylated hydroxytoluene, ascorbate, and a-tocopherol. Emulsifying, stabilizing, and thickening agents are added...

The case of the shrinking alligator penis

It was reported that the alligator population of Lake Apopka in northern Florida was declining, presumably because of lack of success in reproduction. The male animals were found to have abnormal testes, low testosterone levels, and small phalli (penises). The female alligators had abnormalities too and high levels of oestrogen. It is believed that high levels of organochlorine compounds, resulting from a spillage of the pesticide difocol, were responsible. The difocol was contaminated with...

How triorthocresyl phosphate caused jake leg

Tri-orthocresyl phosphate (TOCP) is an organophosphate used as a solvent in industry. It has also been used as an additive for aero engine oil. It causes degeneration of the peripheral nerves (the nerves serving the limbs and hands and feet), a disorder called peripheral neuropathy. This toxic effect is due primarily to a specific interaction between the organophosphate and a particular protein in the nerves, which is an enzyme. TOCP becomes bound to it and then undergoes a change, known as...

Accumulation of chemicals in the food chain bioaccumulation and biomagnification

Bioaccumulation Ddt

Chemicals such as DDT and other organochlorine pesticides are not very soluble in water but do dissolve in fat. Therefore in animals, including humans, that are exposed to these substances the chemicals tend to be distributed into tissues containing fat. Although DDT is metabolized to some extent and some is excreted (see Chapter 2), some of it remains in animals. If exposure is repeated or continuous, accumulation occurs. For example, fish or other organisms swimming in contaminated rivers may...

The case of Susan Barber

As well as being used in many suicides, paraquat has also featured in a murder case. The murder went almost undetected but for the persistence of a pathologist. The Barbers lived in Westcliff-on-Sea in Essex and had been married for over 10 years by 1981. Michael, who worked in a local factory, was unskilled and had been in trouble with the police several times. His wife, Susan, had married him at 17, already with child although, unbeknown to Michael, the child was not his. Susan continued her...

Murder by carbon monoxide

There are many other poisons that have been used for murder, suicide, and execution, both natural and man-made substances. As we saw earlier, carbon monoxide has been widely used for suicide, when coal gas was used in homes and also by way of car exhausts. Both coal gas and, more recently, car exhausts have also been used for murder. Even pure carbon monoxide has been used, for example, as in a case where a college lecturer killed his wife by using the gas from a cylinder he had acquired from...