Food Contamination from Pesticides and Chemicals

Pesticides, herbicides, fungicides, and other chemicals have been used globally for decades to increase food supply and eliminate pests. Data on worldwide pesticide sales and use are remarkably difficult to find, and survey results from countries are often not reliable. The EPA estimates that each year domestic users in the United States spend $8.5 billion for 1.1 billion pounds of pesticides active ingredients. Many of the banned or withdrawn pesticides from developed countries are still produced and sold in developing countries or by some multinationals acting through subsidiaries or joint ventures. These include DDT and other persistent organochlorine (OC) insecticides, which represent about 15% of the sales in regions outside the United States, Western Europe, and Japan. Estimates indicate that 70,000 to 80,000 tons of these compounds were applied in 1995 in developing and formerly socialist countries (Table 2.1) (37-39).

Table 2.1. Regulatory status of some organochlorine pesticides in different countries.

U.S.

China

India

Mexico

U. K.

Canada

DDT

B

R

R

R

B

Not registered

Aldrin

B

Not banned

Not banned

B

B

Not registered

Dieldrin

B

Not banned

R

B

B

Not registered

Endrin

B

Not banned

Not registered

B

B

Not registered

Heptachlor

(R)

Not banned

Not banned

Not

B

Not registered

registered

Hexachlo-

B

B

Not registered

robenzene

Mirex

B

R

R

Banned

Toxaphene

B

Not banned

B

B

B

Not registered

Adapted from Garcia AM. Pesticide exposure and women's health. Am J Ind Med 2003;44:585. © 2003 Wiley-Liss, Inc., a subsidiary of John Wiley & Sons, Inc. Reprinted with permission. Note: Blank spaces above indicate no available data. R, registered; B, banned; (R), restricted.

Adapted from Garcia AM. Pesticide exposure and women's health. Am J Ind Med 2003;44:585. © 2003 Wiley-Liss, Inc., a subsidiary of John Wiley & Sons, Inc. Reprinted with permission. Note: Blank spaces above indicate no available data. R, registered; B, banned; (R), restricted.

Banned pesticides have recently been reintroduced into certain environments such as DDT sprayed in several areas of Africa as a preventive measure against malaria. Older and more toxic organophosphate (OP) and carbamate insecticides and herbicides also have very significant sales in the Third World (e.g., alachlor, aldicarb, benomyl, captan, carbofuran, chlordane, cyanazine, dimethoate, endosulfan, EPN, mancozeb, lindane, monocrotophos, paraquat, parathion, toxaphene, zineb, carbaryl, atrazine, glyphosate, 2-4-D, dichlorovos, phorate, and many others). In developing countries, these pesticides are still preferred by the small farmers because they are less costly, easily available, and display a wide spectrum of bioactivity. Globally, OPs account for nearly 40% of total insecticide sales by volume, followed by carbamates (20.4%), pyrethroids (18.4%), and others (6.1%) (5,6,40).

Persistent pesticides travel through the air, soil, and water into living tissues where they can bioaccumulate up the food chain into human diets. In fact, it has been estimated that approximately 85% to 90% of pesticides applied agriculturally never reaches the target pest organisms but disperses through the air, soil, and water. As an example, the half-life of toxaphene in soil is up to 29 years (5,41,42).

Humans bioaccumulate organochlorine and metal-containing pesticides in their body fat, where they tend to stay unless the fat is metabolized for energy, such as during an illness. For example, in Latin American countries, the pattern of residues found in human body tissues consisted of high levels of DDT and its metabolites, followed by benzene hexachloride (BHC), dieldrin, hep-tachlor epoxide, and hexachlorobenzene (HCB). Interestingly, these organochlorines were also found in people's body tissues in 22 Third World and formerly socialist countries. Furthermore, food standards in developing countries are typically not as well regulated as those in industrialized countries, and pesticide residues are frequently found on agricultural products. For instance, in Brazil, pesticide residues in 13.6% of fruits and 3.7% of vegetables exceeded tolerance limits (5,43,44).

Although less is known of the toxicological consequences of chemical contamination of food items, the WHO has identified acrylamide and semicar-bazide as emerging contaminants that may have potential health consequences for humans, although more investigation is needed. Acrylamide is a chemical that has several uses including manufacture of polyacrylamide materials, treatment of drinking water and wastewater to remove particles and other impurities, and the construction of dam foundations and tunnels. Interestingly, acrylamide also appears to be produced in some foods at high temperatures (45).

Acrylamide is known to cause cancer in animals; certain doses are toxic to the nervous system of both humans and animals. In humans, studies of workers exposed to acrylamide through air and skin contact found no evidence of cancer. However, the International Agency for Research on Cancer (IARC) has classified acrylamide as "probably carcinogenic to humans" on the basis of the evidence from research studies on animals (45).

There is currently little information about, and poor understanding of, how acrylamide forms in foods. It appears to be produced naturally in some foods that have been cooked or processed at high temperature, and the levels appear to increase with the duration of heating. Acrylamide has also been found in home-cooked foods as well as precooked, packaged, and processed food and seems to arise when different food components react together. Although the exact temperature at which acrylamide forms in food is not currently known, acrylamide has not been found in food prepared at temperatures below 120°C. Thus far, the highest levels have been in starchy foods such as potato and cereal products (45,46).

The WHO has also highlighted public health concerns of semicarbazide (SEM) in food at the request of several member states and based on information provided by the European Food Safety Authority. Semicarbazide is found in food products packaged in glass jars with metal lids that have formed plastic seals. Semicarbazide has been detected at low levels in a number of such food products, including baby foods. The origin of SEM is not clear but has been linked to the permitted use of azodicarbonamide in the plastic seals. The presence of SEM has raised concerns since it has weak carcinogenic activity when fed to laboratory animals at high doses. Based on levels reported in food, the health risk, if any, to consumers, including infants, seems quite small. However, since the relatively high consumption of products in glass jars by infants can result in higher exposure as compared to other consumers, the presence of SEM in baby foods is considered particularly undesirable. The WHO has recommended that alternative materials be evaluated for their suitability, including their microbial and chemical safety, and introduced as rapidly as possible for baby foods and subsequently other foods (47).

Other examples of chemical contaminants in food include polychlorinated biphenyls (PCBs), dioxins, and mercury contamination in seafood. Some aquatic organisms can convert inorganic mercury into organic methylmer-cury, with resulting bioaccumulation in large carnivorous fish such as sword-fish. Soils and water used for agriculture may also contain regional environmental hazards such as the widespread arsenic contamination of ground water in Bangladesh (48-50).

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