Chemical contamination
Chemical contamination happens when food is contaminated with a natural or artificial chemical substance. Common sources of chemical contamination can include: pesticides, herbicides, veterinary drugs, contamination from environmental sources (water, air or soil pollution), cross-contamination during food processing, migration from food packaging materials, presence of natural toxins, or use of unapproved food additives and adulterants.
Biological contamination
It happens when the food has been contaminated by substances produced by living creatures, such as humans, rodents, pests or microorganisms. This includes bacterial contamination, viral contamination, or parasite contamination that is transferred through saliva, pest droppings, blood or fecal matter. Bacterial contamination is the most common cause of food poisoning worldwide. If an environment is high in starch or protein, water, oxygen, has a neutral pH level, and maintains a temperature between 5°C and 60°C (danger zone) for even a brief period of time (~0–20 minutes), bacteria are likely to survive.
Example of biological contamination: Tainted Romaine Lettuce
In April and May 2018, 26 states in the United States suffered an outbreak of the bacteria strain E. coli O157:H7. Several investigations show the contamination might have come from the Yuma, Arizona, growing region. This outbreak, which began April 10, is the largest US flare-up of E. coli in a decade. One person in California has died. At least 14 of the people affected developed kidney failure. The most common symptoms of E. coli include diarrhea, bloody diarrhea, abdominal pain, nausea and vomiting