Chemical hazards include agricultural chemicals such as pesticides, herbicides, rodenticides, insecticides, fertilizers, antibiotics and other animal drugs, cleaning residues, naturally occurring toxins, food additives, allergens, and toxic chemicals from industrial processes that can enter the food chain directly during processing or indirectly through plants and animals.
The use of food additives dates back to ancient times. Examples of these early additives
are salt to preserve meats and fish, herbs and spices for seasoning foods, sugar to preserve fruits, and vinegar to preserve vegetables. Today manufacturers use more than 3,000 food additives. A commonly used definition of a food additive is any substance added to a food either directly or indirectly through production, processing, storing, or packaging. Food additives serve a number of functions:
to keep food fresh and to prevent spoilage. This is important, as in our modern lifestyle food is rarely eaten at the time or place it is produced. Calcium propionate inhibits molds and is often added to bread products for this purpose.
to improve or maintain the nutritional quality of foods. Most salt contains iodine to prevent goiter, a condition resulting from iodine deficiency.
to maintain product texture such as retaining moisture, preventing lumping, or adding stability. Powdered foods such as cocoa contain silicon dioxide to prevent clumping when water is added.
to enhance or change the taste or aroma of a food. These include spices, herbs, flavor enhancers, natural and synthetic flavors, and sweeteners.
to give foods an appealing look. Many of the colors we associate with foods are from added colorings, such as caramel to make cola drinks brown and annatto to make margarine yellow.
Food additives are derived from naturally occurring and synthetic materials. Scientists
can now synthesize in the laboratory many additives that used to be derived from natural substances, creating a larger and cheaper supply. Food additives allow us to enjoy safe, wholesome, tasty foods year-round without the inconvenience of growing our own foods or shopping daily. Convenience foods are made possible by the use of food additives.
Up to 6 percent of children and 2 percent of adults suffer from food allergy-the body’s immune system reacting to certain substances in food, usually a protein. The immune system misinterprets a chemical component of a food as harmful and releases histamines and other chemicals to combat it, which results in hives, swelling, itching, vomiting, diarrhea, cramps, or difficulty breathing. Severe reactions may cause anaphylaxis, which can result in death. Eight foods—egg, wheat, peanuts, milk, soy, tree nuts (such as walnuts and almonds), fish, and shellfish—cause 90 percent of all food allergies. The only way to prevent an allergic reaction is to avoid that food entirely.
Food intolerance often is confused with food allergy since the symptoms are often the same. Food intolerance is an adverse reaction to a food that does not involve the immune system. Lactose intolerance is an example of food intolerance. A person with lactose intolerance lacks an enzyme needed to digest a form of sugar present in milk. Consuming milk products causes symptoms such as gas, bloating, and abdominal pain, but does not involve any immune system response. If a person has a true allergy to milk, the only way to avoid milk allergy symptoms is to avoid all milk products entirely. Special drops or tablets that help digest the sugar in milk are available for those suffering from lactose intolerance, allowing them to consume milk products.
To avoid substances to which they are allergic, consumers must know exactly
what is in foods. While it may be possible to control which foods are sold in schools, it is almost impossible to regulate foods students bring from home. Educating students who have food allergies to read carefully food ingredient labels and not to accept foods if they do not know what the ingredients are is key to reducing food allergy attacks.
Drugs, Hormones, and Antibiotics in Animals
The use of drugs to control and treat animal disease, and of hormones to promote
faster, more efficient growth of livestock is a common practice. An estimated 80 percent
livestock and poultry receive some animal drugs during their lifetime. This includes topical antiseptics, bactericides, and fungicides to treat skin or hoof infections and cuts; hormones and hormone-like substances to improve growth; antiparasite drugs; and antibiotics. Improper use of animal drugs may cause residues in the edible tissues of slaughtered animals that could be hazardous to consumers.
Many food safety experts consider problem, antibiotic drug residues in farm animals, to be a problem of larger concern. Antibiotics for farm animals have two purposes. First, they are used to prevent and treat diseases, just as they are in humans.
The reason for administering antibiotics to farm animals is to improve growth and to promote feed efficiency—the production of more meat or milk with less input of feed. This is called a subtherapeutic dose, since it is given in doses lower than those required to treat an infection. Subtherapeutic use of antibiotics controls intestinal bacteria that interfere with an animal’s ability to absorb nutrients. It also controls infections before they become noticeable, thus making animals healthier and allowing them to use nutrients for growth and production rather than to fight infections. Antibiotic use is one reason why the U.S. food supply is so abundant and affordable.
Bacteria will inevitably become resistant to the antibiotics used to kill them. This is because antibiotics do not generally kill 100 percent of their target bacteria. A few will always survive and pass that resistance on to successive generations of bacteria, and in some cases, to other unrelated bacteria. Eventually the genetic make-up of the bacterial strain changes enough so that the drug is no longer effective. This happens with human pathogens such as tuberculosis, as well as with pathogens that infect animals. The most common cause of antibiotic resistance is overuse of antibiotics. Most animal bacterial diseases cannot be passed on to humans, but there are notable exceptions—Campylobacter and Salmonella. Already these two bacteria have developed resistance to some drugs, particularly the fluoroquinolones, used to combat them. There is some evidence of a relationship between the use of fluoroquinolone drugs in poultry and other food-producing animals and the emergence of fluoroquinolone-resistant Campylobacter and Salmonella in humans.
The possibility exists that as pathogens in farm animals become resistant to antibiotics, if those same pathogens are passed on to humans, they will not respond to drug treatments. A report states that there is a link between the use of antibiotics in food animals, the development of resistant microorganisms in those animals, and the spread of those resistant pathogens to humans. However, the report goes on to say that the incidence of this happening is very low, and that there are not enough data to determine whether the incidence is changing. The report concludes that alternatives to antibiotic use for maintaining animal health and productivity should be developed.
Naturally Occurring Toxins
In addition to synthetic chemicals such as pesticides, the food supply contains many naturally occurring toxins. In comparison to synthetic chemicals, scientists know very little about these natural toxins in terms of their toxicity and quantity in foods. They pose a greater risk than the synthetic chemicals because we eat at least 10,000 times more of them. Every food is a complex mixture of chemical compounds, some beneficial such as vitamins and minerals, but also some that are harmful.
Even vitamins and minerals can be toxic if taken in great enough quantities. For example, vitamin A, a necessary vitamin, may be toxic in an amount only 15 times the recommended dietary allowance. Plants and animals developed toxic substances as protection against insects, microorganisms, grazing animals, and other potential dangers.
The potato, contains a very toxic substance called solanine. This naturally occurring toxin is present in larger amounts in the peel and in the eyes than in the potato. In the amounts normally eaten, solanine does not cause illness, but a diet of certain varieties of potato peels and eyes might contain enough solanine to cause illness and possibly even death. Solanine acts as a natural pesticide that protects the potato from the Colorado beetle, the leaf hopper, and other potato pests. In another instance, herbal teas are enjoying a renewed popularity. Consumers view these teas as a natural way of improving their health or treating diseases. However, chemicals in herbal teas can and have caused illness and death. Herbal teas are touted as the answer to many chronic ailments and as such are consumed at much higher levels than they were traditionally, which may lead to natural, but still harmful, side effects. In societies where herbal use is steeped in tradition, knowledge about the benefits and dangers of herbal remedies passes from generation to generation. Very few of the herbs used in natural herbal teas have been studied or tested for safety. One of these is ephedra, commonly known as Ma Huang, an ingredient in many herbal teas marketed as weight loss products. Ephedra is an amphetamine-like compound with potentially powerful stimulant effects on the nervous system and heart.
Seafood products contain some naturally occurring marine toxins that present unique food hazards. Molluscan shellfish, which includes oysters, clams, scallops, and mussels, can pick up toxins from algae that they feed on, and cause paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning, and diarrhetic shellfish poisoning (DSP). The most serious is PSP, with symptoms ranging from tingling, burning, or numbness in the mouth or throat to paralysis, respiratory failure, and in severe cases, death. The algae that produce these toxins can be found during the warmer months anywhere. State authorities monitor harvest waters and close them to shellfish harvesting if algae is present. Since these toxins are not destroyed by heat, and can’t be detected visually, the best control is for people to consume shellfish only from approved waters.
Tropical and subtropical reef fish such as grouper, barracuda, snappers, jacks, and
king mackerel can accumulate ciguatera toxin by feeding on smaller fish that have ingested toxin-forming algae. Ciguatera can cause nausea, vomiting, diarrhea, and
headaches in humans. Tuna, mahi mahi, bluefish, and mackerel have been the sources of scromboid poisoning, a type of foodborne illness caused by the consumption of scombroid and scombroid-like marine fish species that have begun to spoil. This occurs when the amino acid histidine breaks down into histamine, usually as a result of inadequate refrigeration. Scromboid symptoms include a rash, burning or peppery taste sensations about the mouth and throat, dizziness, nausea, headache, itching, and swelling of the tongue. Puffer fish, known as fugu in Japan, is a great and dangerous delicacy in that country. An extremely toxic poison called tetrodotoxin accumulates in the internal organs of the fish. Only specially trained and licensed chefs are allowed to prepare fugu fish, as improperly prepared fugu causes paralysis, respiratory failure, convulsions, and cardiac arrhythmia within 20 minutes. Death is not uncommon.
Fungi, which include mushrooms and molds, also produce toxins that are harmful to humans. Molds produce toxins called mycotoxins, with the major mycotoxin-producing molds being Aspergillus, Fusarium, and Claviceps species. Molds usually grow on damp cereal grains such as rye, wheat, corn, rice, barley, and oats, or oilseeds (peanuts), and then excrete their mycotoxins during their life cycle. Most of these mycotoxins are very resistant to heat, so cooking does not reduce their harmfulness. The only way to prevent intoxication is by preventing the mold from contaminating the product during harvesting, drying, storage, and processing.
One mold in particular, Claviceps purpurea, has been implicated in a number of historical events. Eating rye and other cereal grains contaminated with Claviceps purpurea results in the disease ergotism.
Cold and damp growing or storage conditions also promote the formation of ergot. Ergot is the source of lysergic acid diethylamide (LSD); it and many other ergot derivatives are hallucinogens. The symptoms of ergotism are varied, but include central nervous system disorders such as muscle spasms, confusions, delusions, convulsive fits, hallucinations, visions, sensations of flying through the air, and psychosis. Other common symptoms are a prickly sensation in the limbs, feelings of intense alternating heat and cold, and increased appetite between episodes of fits.
Fortunately the body has a very efficient mechanism to destroy many naturally
and synthetic chemicals—the liver. The liver is capable of eliminating small quantities
of many poisons, which allows humans to safely consume otherwise toxic chemi-cals.
However, large quantities of toxins and chemicals can easily overwhelm the
body’s defenses. We often think of naturally occurring compounds as relatively safe,
but in reality some are among the most toxic substances known.
Pesticides prevent, destroy, or control pests. Pests are any organism that causes damage to plants, animals, or foods, such as bacteria, viruses, rodents, worms, fungi, insects, or weeds. The term pesticide is very broad and includes herbicides (to control weeds), insecticides (to control insects), fungicides (to control mold, mildew, and fungi), rodenticides (to control rodents), and disinfectants (to control bacteria and viruses). Three-quarters of the pesticide use is for agriculture (mainly on crops in the field), but it is also used post-harvest during transportation and storage to prevent mold growth or insect infestation. While we may not think of household cleaners, pet flea collars, lawn and garden products, and insect repellants as pesticides, they are.
Since the beginnings of agriculture humankind has used pesticides in an attempt to control nature to ensure good crop yield. Egyptian records from 1500 B.C.E. contain
instructions for preparing insecticides to control lice, fleas, and wasps. The Greeks were using sulfur by 1000 B.C.E. to control insects, as did European farmers in the eighteenth century. The Chinese controlled insects with a mixture of arsenic and water. While we may think of pesticides as synthetic chemicals, the above examples show that many natural compounds also act as pesticides. Pesticide use has both advantages and disadvantages.