Despite the large number of reported cases, WHO estimates that only a small fraction of these diseases is currently recognized and reported as being of foodborne origin. In developing countries, the ratio between real and reported cases may be as high as 100 : 1, while in industrialized countries the reported incidence connected with food contamination represents probably less that 10% of the total number of actual cases. In 1997, WHO suggested that food-poisoning may be over 300 times more prevalent than the number of reports indicate.
Although most foodborne diseases are microbial in origin, the widespread use of chemical substances through the food production chain has increased the risk of chemical contamination in recent years. Commonly used chemicals include agricultural pesticides and fertilizers, veterinary drugs, growth hormones and food additives. Other varieties of chemicals, such as lead and cadmium, are not intentionally brought into contact with foodstuffs, and have nothing to do with food production, by they find their way into the good chain from the environment and may pose a risk to public health.