FOOD SAFETY other contaminants, pages 340 344, c k winter

340 FOOD SAFETY/Other Contaminants Osterholm MT and Norgan AP (2004) The role of irradiation in food safety New England Journal of Medicine 350: 1898–1901 Perales I and Garcia MI (1990) The influence of pH and temperature on the behaviour of S enteritidis phage type in homemade mayonnaise Letters in Applied Microbiology 10: 19–22 Roberts JA, Cumberland P, Sockett PN et al (2002) The study of infectious intestinal disease in England: Socioeconomic impact Epidemiology and Infection 129: 1–11 Takkinen J, Ammon A, Robstad O, Breuer T, and the Campylobacter Working Group (2003) European Survey of Campylobacter surveillance and diagnosis 2001 Eurosurveillance 8: 207–213 Tuttle J, Gomez T, Doyle MP et al (1999) Lessons for a large outbreak of E coli O157:H7infections: Insights into the infectious dose and method of widespread contamination of hamburger patties Epidemiology and Infection 122: 185–192 Zaidi AKM, Awasthi S, and deSilva HJ (2004) Burden of infectious diseases in South Asia British Medical Journal 328: 811–815 Other Contaminants C K Winter, University of California at Davis, Davis, CA, USA ª 2005 Elsevier Ltd All rights reserved Food may be contaminated with many chemicals that pose the potential for toxicological consequences in humans consuming the contaminated food items In addition to the presence of contaminants such as mycotoxins, pesticide residues, and heavy metals, food may contain numerous organic contaminants that enter the food supply from environmental sources or as a result of chemical reactions that occur during food processing This article focuses on three types of food contaminants: dioxins (including dibenzofurans and polychlorinated biphenyls), acrylamide, and perchlorate Each of these classes has been subject to considerable regulatory scrutiny, scientific study, and popular media coverage It is likely that concerns regarding the presence of these contaminants in the food supply will continue throughout the next decade or longer, and that significant efforts will be made to reduce human exposure to these substances from food This article discusses how these types of food contaminants enter the food supply, the types of food items in which they are most likely to occur, and the potential toxicological consequences resulting from exposure to these contaminants speaking, the dioxins of potential toxicological concern are polychlorinated dibenzo-p-dioxins (PCDDs) They are related, both structurally and toxicologically, to polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) Structures of generic PCDDs, PCDFs, and PCBs are shown in Figure Due to their structural and toxicological similarity and to avoid confusion, all three related groups of chemicals are considered to represent ‘‘dioxins’’ for the purposes of this article Specific chemicals belonging to this family are referred to as congeners Collectively, there are more than 200 dioxin-related congeners, and each possesses unique toxicological and chemical properties Occurrence in the Environment and in Food PCDDs and PCDFs are primarily introduced into the environment as by-products of combustion processes These by-products have been identified in the exhaust gases from sources such as cigarette smoke; industrial and municipal waste incinerators; power plants burning coal, oil, or wood; and automobiles In addition to these human sources, PCDDs and PCDFs are also produced naturally by combustion in forest fires and from volcanic eruptions Historically, PCDDs and PCDFs have also been produced as impurities during organic chemical synthesis The most notable and most toxic dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), has been shown to be produced in the synthesis of the herbicide 2,4,5-T, one of the herbicide components of Agent Orange, notoriously used in the Vietnam War Although 2,4,5-T is now banned for use in the United States because of TCDD and other dioxin impurities, health concerns over the exposure of military veterans to Agent Orange and to TCDD continue to be raised PCDDs and PCDFs can also be produced through the use of chlorine O PCDD O Cl Cl PCDF O Cl Cl PCB Dioxins Dioxins are organic chemicals that comprise a family of ubiquitous environmental contaminants Technically Cl Cl Figure Chemical structures of generic PCDDs, PCDFs, and PCBs FOOD SAFETY/Other Contaminants to bleach wood pulp, although most bleaching processes now use nonchlorine agents such as hydrogen peroxide PCBs have been produced synthetically since the 1930s and have been widely used for industrial applications, such as dielectric fluids in transformers (due to their inflammability) and capacitors in electrical machinery Like their PCDD and PCDF counterparts, PCBs are extremely persistent in the environment and are of toxicological concern As a result, the synthesis and industrial use of PCBs were significantly curtailed in the 1970s, although environmental residues of PCBs are still commonly detected today Although dioxin release into the environment has been known to occur for several decades, data are still limited with respect to the degree to which dioxins contaminate the food supply Dioxin analysis in the laboratory is extremely expensive because methods must identify hundreds of different congeners, detection limits are required in the sub-part per trillion range, and significant precautions must be taken to minimize exposure of laboratory personnel to the analytical standards used for dioxin congeners Dioxins are highly fat soluble and have been shown to accumulate in the fat of birds, fish, and food animals The US Environmental Protection Agency (EPA) has estimated that more than 95% of human exposure to dioxins results from dietary intake of animal fats The major food sources for dioxin exposure include fish, poultry, meats, milk, and milk products Dioxins are excreted in human breast milk and result in exposures to nursing infants Historically, it has been shown that human dioxin exposures, as determined by analyzing human tissues and environmental samples, have decreased significantly since 1987 due to engineering controls to limit dioxin emissions during combustion processes and to increased regulatory control over other sources of dioxin exposure Dietary dioxin exposures to UK consumers were reduced by nearly two-thirds from 1982 to 1992, and subsequent studies showed even lower exposures in 1997 Nevertheless, dioxins are still ubiquitous in the environment and human exposure still occurs Toxicological Considerations Dioxin exposure at significant dose levels has been linked to a large number of adverse health effects Large acute exposures, resulting from chemical accidents and/or occupational exposure to dioxins, have caused a severe skin condition known as chloracne 341 A variety of other skin effects, such as rashes and discoloration, have also been attributed to acute dioxin exposures, as has liver damage Concerns from chronic exposure to dioxins include cancer, reproductive effects, and developmental effects The most toxic dioxin congener, TCDD, was classified by the International Agency for Research on Cancer as a human carcinogen From a biochemical standpoint, PCDDs, PCDFs, and PCBs appear to cause their toxic effects through chemical binding to a specific cellular receptor known as the Ah receptor Specific dioxin congeners vary dramatically with respect to their abilities to bind with the Ah receptor; TCDD binds extremely effectively, whereas other congeners are more limited in their binding capabilities The degree to which various dioxin congeners bind with the Ah receptor seems to be directly related to the number and location of chlorine atoms on the congeners Assessing the potential human health risks from exposure to dioxins presents significant challenges Dioxin levels in specific food items can be quite variable, and, as discussed previously, data concerning dioxin levels on foods are frequently not available Another difficulty encountered in assessing dioxin risks is to appropriately account for exposures to the various congeners and to account for the toxicological differences among congeners This is most appropriately achieved through a toxic equivalency factor (TEF) approach that assigns a potency factor to each of the congeners relative to that of the most toxic dioxin TCDD For example, the TEF for TCDD is and the TEF for 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (with chlorines added to the and positions and otherwise similar to TCDD) is 0.1 based on findings that 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin is 10 times less capable of binding to the Ah receptor than is TCDD To calculate a total dioxin exposure, the dietary contributions of each of the dioxin congeners are multiplied by their corresponding TEFs and summed to determine a TCDD equivalent exposure According to the World Health Organization (WHO), a tolerable daily intake (TDI) for TCDD was established at 10 pg TCDD per kilogram bodyweight per day in 1990, although revisions by WHO reduced the TDI range to 1–4 pg/kg/day in 1999 A 1997 UK survey of dioxin consumer exposure provided an upper bound of 1.8 pg TCDD equivalent/ kg/day Surveys from other countries, using slightly different TEF approaches, yielded exposures of 0.7 pg/kg/day in Italy, 1.4 pg/kg/day in Norway, 2.4–3.5 pg/kg/day in Spain, and 0.2 pg/kg/day in New Zealand 342 FOOD SAFETY/Other Contaminants The US Food and Drug Administration (FDA) has been monitoring finfish, shellfish, and dairy products for dioxins since 1995 and initiated dioxin analysis of foods analyzed in its Total Diet Study in 1999 Specific findings from the FDA’s annual Total Diet Study can be obtained from the FDA, although human exposure estimates, in terms of the amount of TCDD equivalent exposure per kilogram of body weight per day, have not been published by the FDA The EPA recommends that consumers follow the existing Federal Dietary Guidelines to reduce fat consumption and, subsequently, dioxin exposure Such guidelines suggest that consumers choose fish, lean meat, poultry, and low- or fat-free dairy products while increasing consumption of fruits, vegetables, and grains Dioxin exposure can be further minimized by trimming visible fat from meats, removing the skin of fish and poultry, reducing the amount of butter or lard used in cooking, and replacing cooking methods such as frying with methods such as boiling or oven broiling Acrylamide Acrylamide is a widely used and versatile industrial chemical Its most common use is as a coagulant in water treatment and purification It is also used as a soil conditioner, in the sizing of paper and textiles, in ore processing, and as a construction aid for the building of tunnels and dam foundations Acrylamide is considered by the International Agency for Research on Cancer to be ‘‘probably carcinogenic to humans’’ based on the results of several animal carcinogenicity studies As a result, there has been widespread concern about the potential risks from exposure to acrylamide among industrial, manufacturing, and laboratory workers Consumer exposure to acrylamide in treated drinking water has posed a much lower concern since drinking water is subject to special treatment techniques that control the amount of acrylamide in drinking water Swedish researchers developed laboratory techniques that allowed for the detection of biological reaction products (hemoglobin adducts) of acrylamide in human blood samples; results from their studies allowed correlations to be made between occupational activities and acrylamide exposures The findings that acrylamide occurred in tobacco smoke and that smokers had increased levels of hemoglobin adducts relative to nonsmokers provided a suggestion that acrylamide may be formed during incomplete combustion of organic matter or during heating Interestingly, the researchers found significant levels of hemoglobin adducts in blood samples of nonsmoking humans not exposed occupationally to acrylamide This led to speculation that the human diet could contain significant quantities of acrylamide In April 2002, Swedish researchers published results of research that demonstrated the presence of acrylamide in several common foodstuffs, with the highest levels found in fried and baked foods These findings stimulated worldwide interest in identifying the potential mechanisms for acrylamide formation in foods, in assaying a wide variety of foods for acrylamide levels, and in developing risk assessment and risk mitigation procedures Occurrence in Food The findings from the initial Swedish study indicated that the highest levels (150–4000 mg/kg) of acrylamide were detected in carbohydrate-rich foods such as potatoes and in heated commercial potato products (potato chips) and crispbread Moderate levels (5–50 mg/kg) were measured in protein-rich foods that were heated, whereas unheated or boiled foods showed no detectable acrylamide ( ... Research on Cancer as a human carcinogen From a biochemical standpoint, PCDDs, PCDFs, and PCBs appear to cause their toxic effects through chemical binding to a specific cellular receptor known... damage Concerns from chronic exposure to dioxins include cancer, reproductive effects, and developmental effects The most toxic dioxin congener, TCDD, was classified by the International Agency for... pituitary–hypothalamic–thyroid axis by perchlorate may lead to serious effects, such as carcinogenicity, neurodevelopmental and developmental changes, reproductive toxicity, and immunotoxicity Specific concerns