Hazards in food

Food safety means being sure that food is acceptable to eat for its intended use. Toxicity is a substance's capacity to harm. A hazard is the probability (chance) of harm when a substance is not used as it should be.

Three kinds of hazards:

• Physical: foreign objects: stones, hair, wood, bones, nails, jewellery, matchsticks.
• Chemical: pesticides and their residues, toxic metals, PCBs, preservatives, colours and other additives, and adulterants.
• Biological: visible pests (flies, weevils, cockroaches, worms) and invisible microbes (bacteria, viruses, moulds, yeasts, protozoa).

Germs cause illness in two ways:

• Infection: live germs multiply inside the body. Example: Salmonella, from animal intestines, raw milk and eggs. It spreads through undercooking, cross-contamination and unwashed hands, and causes diarrhoea, fever and cramps.
• Intoxication: a toxin made in the food stays even after the germ dies, and you cannot smell or taste it. Example: Staphylococcus aureus, carried on the skin and nose of many healthy people.

Parasites, like the tapeworm in pork, also get into food. New germs appear as hosts, germs, eating habits and the climate change, and with mass production and globalisation (for example norovirus, rotavirus, hepatitis E). Physical, chemical, biological: watch all three.