Naturally occurring toxins
Residual chemicals used in food production: chemical preservatives, pesticides, heavy metals, hormones, colors, antioxidants, stabilizers
Links:
[1] https://homescience.iisuniv.ac.in/courses/subjects/food-quality-control-theory-2
[2] https://homescience.iisuniv.ac.in/academic-year/2015-2016