Elements of danger

PUBLISHED : Sunday, 22 May, 1994, 12:00am
UPDATED : Sunday, 22 May, 1994, 12:00am

COOKING and boiling can kill bacteria and viruses but is not effective against the metal content. All seafood should be cooked thoroughly at temperatures exceeding 100 degrees Celsius (212 degrees Fahrenheit) for a long period of time, which will vary according to the weight of the fish. Unfortunately, this form of cooking may destroy the taste of the fish. Hygiene conditions are just as important as the method of cooking; dirty worktops, knives, pots and pans can lead to the spread of bacteria and viruses.

CADMIUM A tin-like metal that is normally recognised as a poisonous by-product of certain industrial processes, such as the manufacture of certain alloys, cadmium plating and glass blowing. Where an excess of cadmium is consumed, it causes gastro-enteritis, diarrhoea, excessive secretion of saliva, vomiting, choking, chest pains, blood clots, loss of consciousness, kidney failure, lung infections and damage to the foetus of pregnant women.

E-COLI A group of bacteria which develop in the human intestine. Their presence in water indicates recent contamination by human faeces. Relatively small volumes can cause gastro-enteritis, vomiting, diarrhoea and hepatitis A.

TOTAL PLATE COUNT The total bacterial count of shellfish. Samples of tissue are tested for the number of colony-forming units, which harbour more serious forms of bacteria such as E-coli. In the worst case, 390,000 colony-forming units were found in just one gram of crab tissue. E-coli can sometimes represent 50 per cent of all colony-forming units detected.

MERCURY When too much mercury is taken into the system in small doses, the first sign is an excessive discharge of saliva into the mouth. The gums become tender, spongy and ready to bleed at the slightest touch, and the tongue becomes swollen. Finally, the teeth fall out, the jaw-bone may become diseased, and the sufferer becomes generally weak and can die. Other symptoms of mercury poisoning are diarrhoea, vomiting and kidney infection.

LEAD A toxic heavy metal which, though used widely in the past, has been used less in recent decades. This reduction can largely be attributed to the phasing-out of leaded petrol. However, while exposure to lead has greatly diminished, several recent studies suggest adverse effects can occur at levels of exposure previously thought safe.

The effects of lead on human health are varied. Exposure can adversely affect many organ systems including reproduction, renal, cardio-vascular, blood-forming and developing central nervous systems. Studies indicate lead intake causes learning deficiencies and behavioural difficulties among children. Main symptoms are muscular weakness, a blue line on the gums, colic, breakdown of the nervous system, paralysis and brain damage.