Contamination in food is caused by external environmental factors such as heavy metals, pesticides or even solvents. Contamination occurs through the air, soil, plants or water. Lead, cadmium and mercury are of particular importance. Industrial plants and road traffic dominate as sources of lead emissions. The combustion of coal or fuel containing lead produces gaseous lead compounds that disperse widely in the air. Lead eventually enters the food chain due to deposition of lead-containing dust particles on above-ground plant parts or via mineral fertilizers containing heavy metals in the soil, and thus via plants as well as groundwater. Other important pathways of lead input into food include wild mushrooms, offal, and milk and dairy products from animals grazing on lead-contaminated pastures. Canned foods are sealed with lead or are made of tin-plated iron sheet, and the tin may contain lead. Such foods have approximately 20 to 50 mg tin/kg. When cans are opened, the tin content increases considerably. The acids of acidic herring or fruit juices from canned foods lead to an acidic pH and dissolve tin to a greater extent than when the pH in the can is neutral, increasing the risk of poisoning. The heavy metal also enters the canned contents through can seams made with leaded tin. If fruit juices are made from leaded tin using presses, they too can become contaminated with lead. Acute and chronic symptoms caused by lead affect the gastrointestinal tract, the central and autonomic nervous system, and the kidneys.
In addition to lead, aluminum also poses a health risk because heating food in aluminum pots or aluminum foil increases the metal content by about 0.5-3mg/ 100 g dry weight. In particular, salty foods, acidic foods such as meat, fish, cereal products and eggs, or basic or alkaline foods such as fruits and vegetables are able to dissolve the aluminum ions due to their respective salt, acid or basic excess as well as their corresponding pH value, which are then distributed in the body. Cadmium enters our environment and food chain through industrial discharges and waste – namely, when waste paint and plastics are incinerated, the heavy metal is released. Phosphate fertilizers containing cadmium contaminate the soil and thus our plant food sources. Elevated doses of cadmium lead to kidney dysfunction as well as cardiac arrhythmia, osteoporosis, anemia, susceptibility to infections and learning disabilities as well as growth disorders in children.
Due to industrial waste – chlorine manufacturing, waste incinerators, broken thermometers and barometers – pesticides, batteries, cosmetics, and medicines, high levels of mercury pollute the air, soil, and groundwater. Inputs to seawater enrich fish and seafood with mercury. Amalgam dental fillings are an additional reason for the accumulation of this heavy metal in the body. Small amounts of mercury are released from the fillings and spread throughout the body. Regular gum chewing increases mercury exposure in the body. Dentists and their assistants therefore have an increased risk of exposure. The consequences of mercury exposure are respiratory problems, immune deficiency, increased risk of cancer, birth defects, and mental retardation of the child during pregnancy. The central nervous system is at significant risk, from which brain damage can result.
