Final answer:
Food can become unsafe due to biological hazards, chemical contaminants, physical impurities, and allergenic substances, which can cause foodborne illnesses or allergic reactions.
Step-by-step explanation:
Types of contaminants that could make food unsafe include biological hazards, chemical contaminants, physical impurities, and allergenic substances. Biological hazards are pathogens like Norovirus, Salmonella, Clostridium perfringens, and Campylobacter, which can contaminate food and cause various foodborne illnesses.
Chemical contaminants include agrochemicals, like pesticides and herbicides, and environmental contaminants, which come from the air, water, or soil and can contain substances like PCBs and DDT that are harmful even in small quantities.
Physical impurities can be anything from metal shavings to pieces of plastic or glass that accidentally enter food during processing, and allergenic substances are food components that cause allergic reactions in sensitive individuals.