You may not be so familiar with pesticide residues, but I believe you must have heard of a food recall. Although most food recalls are due to undeclared allergens, there are still a lot of recalls caused by bacteria such as listeria, E. coli, and salmonella. Escherichia coli is mostly present in the intestines and excreta of warm-blooded animals, causing diarrhea or vomiting in mild cases, and even sepsis and meningitis in severe cases. 

Listeria is usually more susceptible to infections in babies, the elderly, and those with weakened immune systems. It's most commonly caused by eating improperly processed deli meats and unpasteurized milk products. And if you develop a listeria infection, you might have fever, chills, or muscle aches. Symptoms might begin a few days after you've eaten contaminated food, but it can take 30 days or more before the first signs and symptoms of infection begin. 

Salmonella infection is a common bacterial disease that affects the intestinal tract. Salmonella bacteria typically live in animal and human intestines and are shed through feces. Humans become infected most frequently through contaminated water or food.

Typically, people with salmonella infection have no symptoms. Others develop diarrhea, fever, and abdominal cramps within eight to 72 hours. Most healthy people recover within a few days without specific treatment.

In some cases, diarrhea associated with a salmonella infection can be so dehydrating as to require prompt medical attention. Life-threatening complications also may develop if the infection spreads beyond your intestines.

Source from: Mayoclinic.org  

We can see that since 2004, the number of Salmonella infections in the United States has increased year by year. The main reason for this factor is that the food is contaminated during transportation.  

Chemical residue

Data references: https://migration.ucdavis.edu/rmn/blog/post/id=2569