This has been done more in the past than is done currently. The primary way these things happen is through manipulation of manufacturing to interfere with sanitation and quality control processes. So the consequences look natural as being inadvertent human failure or inadequacy from not predicting what might be a weak link in the manufacturing processes being utilized, or human error, or poor judgment. So there is no suspicion of an outside, dark influence taking place. Most chemical contaminants are simply present and overlooked as hazards due to human complacency resulting from mind control manipulation. So many things are present in foods and sources of water that are deleterious within the body but not yet recognized to be so. These are not filtered out accordingly and may be cumulative over time.
This is a combination of human ignorance and the overlay of mind control manipulation, to maintain that ignorance, and prevent instituting higher standards so things are not ingested that have not had a proven track record in safety studies. To do the latter for everything within food is daunting at present but there are many things that stand out with regard to known associations of food with various symptoms, and things present that are clearly suspicious-looking from a standpoint of chemical structure, and their belonging to certain families of chemical substances known to have toxic members. So there are many starting points to do some useful additional exploration to promote greater safety.