The source of this pollution is, of course, traffic congestion. Every day automobiles release high levels of lead into the air we breathe, which is why most food and drink sold by street vendors was shown to contain traces of the substance. According to the Division of Food Analysis, lead contamination has been found in food and drink at a number of school canteens, which is particularly alarming when one considers that children are the ones being affected. Lead contamination is by no means the only danger. Food products, at every step of the production process, are exposed to several different forms of contamination. It seems almost impossible for consumers to avoid contamination food, as it affects vegetables, fruits, meats and many other types of foods. The survey showed that fruits and vegetables sold in markets contain pesticide residues such as phosphate pyrethroid, and arsenic. Chemical substances such as pesticides and fertilizers are commonly used by farmers, who seek to make their produce appealing in order to maximize profits.