**3. Contaminants in conventional foods**

Developments in medicine, industry and agriculture have caused the world's population to increase and as a result of the need to feed the increasing population and urbanization, it became a necessity to produce more in agriculture and industry. This necessity caused widely use of different chemicals (pesticides, heavy metals, veterinary medicines, etc.) in various areas of production and this caused high amount of disposals of wastes in an uncontrolled manner to the environment, which results pollution. In parallel with the increase in pollution, the contaminants in food resources caused significant health problems in humans as a result of food chain [50].

#### **3.1. Metal residues in conventional animal products**

Heavy metals are the elements with an atomic weight between 63,546 and 200,590 and with a specific gravity more than 4.0 [51]. Metals are dispersed in the nature through geological and biological cycles [52] and then can penetrate to the food chain by contaminating the cereals from the environment, the animals and animal products from contaminated cereals and herbs, and fish from the polluted waters [52, 53].

Metals have harmful effects on most of our organs due to their elementary structure and their affination with organic ligands through biological cycles. Since metals are strongly bound to tissues, they are disposed very slowly and accumulated in the body. Samples of blood, urine and hair are usually used as indicators in evaluating the level of exposure to metals [52]. Although soil is the primary source of toxic metals in edible plants, the level of contamination increases more with metal wastes, consumption heavy metal wastes, leaded fuels and paints, fertilization of soil, animal fertilizers, sewage wastes, pesticides, irrigation with waste water, wastes of coal burning, spillage of petrochemicals, atmospheric accumulation, volcanic activities, etc. [54, 55]. It was revealed in the study of International Atomic Energy Agency (IAEA), which was conducted on various food samples taken from 12 countries, that Pb, Cd, Hg and As are important in terms of health and contamination risk, whereas antimony (Sb), Fe, Cu and Zn are less important [56]. International Agency for Research on Cancer (IARC) has specified Cd and Cd components as Group I carcinogen for human health (they induce lung tumors) [57]. Heavy metals, such as As, Cd, Hg, Cu, Pb, etc. that contaminate water through any means can accumulate within fish and then cause health problems in humans [58].

Maximum limits of Cd, Pb and Hg in some animal products are given in European Commission (EC) and Turkish Food Codex (TFC) [56]. There is also information about daily consumption amounts of metals that humans can take. Daily consumption amount of Sb is specified as 0.25–1.25 mg for children in the USA. The USA has determined that Al consumption should not exceed 12–14 mg/day for young and adult men and 9 mg/day for young and adult women [52]. Although, Zn is an essential element for human body, according to animal experiments, high doses of Zn is toxic and carcinogenic [53, 59]. The amount that can be taken with food is set as 0.23 mg/kg/day by the FDA [59]. Contaminated seafood with industrial wastes may contain high level of Zn, and entry of these products into the food chain can pose a danger to human health. Food and Agriculture Organization (FAO) and World Health Organization (WHO) and has determined that maximum amount of daily allowable consumption of as should be 2 μg/kg of body weight [60].

found negative by the analyses for toltrazuril aminoglycosides, sulfonamides, beta-lactam

Developments in medicine, industry and agriculture have caused the world's population to increase and as a result of the need to feed the increasing population and urbanization, it became a necessity to produce more in agriculture and industry. This necessity caused widely use of different chemicals (pesticides, heavy metals, veterinary medicines, etc.) in various areas of production and this caused high amount of disposals of wastes in an uncontrolled manner to the environment, which results pollution. In parallel with the increase in pollution, the contaminants in food resources caused significant health problems in humans as a result

Heavy metals are the elements with an atomic weight between 63,546 and 200,590 and with a specific gravity more than 4.0 [51]. Metals are dispersed in the nature through geological and biological cycles [52] and then can penetrate to the food chain by contaminating the cereals from the environment, the animals and animal products from contaminated cereals and

Metals have harmful effects on most of our organs due to their elementary structure and their affination with organic ligands through biological cycles. Since metals are strongly bound to tissues, they are disposed very slowly and accumulated in the body. Samples of blood, urine and hair are usually used as indicators in evaluating the level of exposure to metals [52]. Although soil is the primary source of toxic metals in edible plants, the level of contamination increases more with metal wastes, consumption heavy metal wastes, leaded fuels and paints, fertilization of soil, animal fertilizers, sewage wastes, pesticides, irrigation with waste water, wastes of coal burning, spillage of petrochemicals, atmospheric accumulation, volcanic activities, etc. [54, 55]. It was revealed in the study of International Atomic Energy Agency (IAEA), which was conducted on various food samples taken from 12 countries, that Pb, Cd, Hg and As are important in terms of health and contamination risk, whereas antimony (Sb), Fe, Cu and Zn are less important [56]. International Agency for Research on Cancer (IARC) has specified Cd and Cd components as Group I carcinogen for human health (they induce lung tumors) [57]. Heavy metals, such as As, Cd, Hg, Cu, Pb, etc. that contaminate water through any means can accumulate within fish and then cause health problems in humans [58].

Maximum limits of Cd, Pb and Hg in some animal products are given in European Commission (EC) and Turkish Food Codex (TFC) [56]. There is also information about daily consumption amounts of metals that humans can take. Daily consumption amount of Sb is specified as 0.25–1.25 mg for children in the USA. The USA has determined that Al consumption should not exceed 12–14 mg/day for young and adult men and 9 mg/day for young and adult women [52]. Although, Zn is an essential element for human body, according to animal experiments, high doses of Zn is toxic and carcinogenic [53, 59]. The amount that can be taken with food

antibiotics, tetracyclines, quinolones and colistin residues [13].

**3. Contaminants in conventional foods**

**3.1. Metal residues in conventional animal products**

herbs, and fish from the polluted waters [52, 53].

of food chain [50].

136 Livestock Science

Most of the foods other than fish contain <0.25 mg/g As, but many fish species contain As between 1 and 10 mg/g. However, the amount of As found in marine crustaceans and deep sea fish was found as 100 mg/g or more [51]. Although the amount of As consumed is 10–200 µg/day, this amount can reach to several thousand μg/day in those that consume fish a lot in their diet [58]. The accumulated amount of As is 3–10 ppm in oyster, 42–174 ppm in mussels and 42–174 ppm in shrimps. Thus, most of the As taken with food by human is originated from sea foods [51]. However, As poisoning due to consumption of animal products is also possible. It was seen in early summer of 1955 that the babies younger than 12 months in western Japan had symptoms of anorexia, skin pigmentation, diarrhea, vomiting and distention and more than 100 babies showing these symptoms died and then it was found that the case was caused by consumption of powdered milk (popular and brand), which contains approximately 21–34 μg As per gram and As was found in the babies that consumed this powdered milk. It was also found that the origin of As was disodium phosphate, which was added to cow milks as a stabilizer [51, 61].

Cadmium, one of 25 substances that have a certain potential of danger against human health, cannot be disposed from and is accumulated within the body [57]. Foods usually contain Cd less than 0.05 ppm. However, WHO announced that the highest level of Cd was found in crustaceans as well as the kidneys of various animals, such as cow, chicken, pig, sheep and turkey as a result of analyses. Daily tolerable amount of consumption of Cd is 1 μg/kg of body weight [52]. The US Environmental Protection Agency (US EPA) stated that Hg and Hg components, which cause kidney cancer in experimental animals, may also cause cancer in humans [53]. The amount of Hg ranges between <1 and 50 µg in many food and beverage. However, the most important source of Hg in diet is the fisheries, caught from contaminated waters. Since crustaceans, such as mussel and oyster, feed by filtering water, they accumulate Hg components in their bodies. Mercury exists in bigger fishes in higher concentrations, compared to smaller ones. According to a research conducted by FDA, the amount of Hg in big tuna fishes was 0.25 ppm, whereas it was found as 0.13 ppm in average in smaller tuna fishes. The type of Hg that is found most in sea foods (>90%) is methyl mercury. FDA determined maximum allowable level of Hg in fish and crustaceans as 0.5 ppm [51]. Methyl mercury poisoning or Minamata disease, seen in Japan in 1954, is the most important example of Hg poisoning due to animal products. This disease was caused by consumption of fishes, living in water that was heavily contaminated with industrial wastewater. Similarly, serious muscle and neurological dysfunctions were seen in humans living in the city of Nigata and close to Minamata Bay in 1970 and 50 of 120 hospitalized persons died [51, 62].

#### **3.2. Pesticide residues in conventional animal products**

Pesticides are chemicals, most of which are highly toxic and are used against pests. These substances are toxically effective not only against pests but also other living organisms. Pesticides cause behavior disorders, immunosuppression, allergic reactions, estrogenic, teratogenec, mutagenic and genotoxic effects on living organisms. The duration of stay of pesticides in the natural environment, depend on their chemical structure. Pesticides, such as chlorinated hydrocarbons are resistant against biological degradation and they can stay in soil for years and penetrate to the food chain through various means. These fat soluble pesticides can be accumulated in the fat tissue of humans and animals as well as in their livers, kidneys and neural systems. Residues in the body of lactating animals can easily penetrate to the animal's milk [51, 52]. Contamination of animal products, such as meat and milk, with permanent pesticide residues is a frequently encountered problem. In a study conducted in Jordan, in which eggs as well as meats of chicken, sheep and cow were scanned for OCP residues, it was found that 28% of eggs, 20% of chicken meat, and 49% of red meat were contaminated with OCP [63].

Chlorinated compounds, such as PCBs, aldrin, DDT, DDD, DDE, BHC, heptachlor, etc., which enter the body of fishes through various means, can accumulate within the fishes and cause health problems in humans that consume these fishes. There is a linear relationship between accumulation of chlorinated compounds, such as PCBs, within fishes and their fat contents. The experiments showed that half-lives of PCBs in fishes are quite long. Despite the fact that utilization of PCBs was banned, they were still found in fish samples, analyzed in Ontario, Canada in 1992–1993, and in fish samples collected from 15 different countries in 1994–1995 [58].

#### **3.3. Bacterial contaminants in conventional animal products**

Milk is considered sterile (free from microorganism) because of its compounds and chemical properties. But milk is a suitable medium for most microorganisms. In general, it is not expected that milk has microorganisms and toxins unless there is a systemic or local infection. But clinical and subclinical mastitis, which are associated with local or systemic infections are common problems for animals [64, 65]. The milk flora of dairy animals consists of lactic acid bacteria (LAB; *Lactococcus, Lactobacillus, Leuconostoc, Streptococcus, Enterococcus* spp.) [64]. *Staphylococcus aureus*, which produces toxins like Staphylococcal enterotoxins (SEs), SE-like toxins (SEI) and toxic shock syndrome toxin (TSST-1) and is primarily responsible for foodborne poisonings, mostly exists in milks of animals with mastitis [65]. According to State Agencies to Centers for Disease Control and Prevention and from the Center for Science in the Public Interest Database, product-based numbers of *Campylobacter*-based cases caused by consumption of raw milk, pasteurized milk and cheese that's produced from raw milk between 2000 and 2006 were recorded, respectively, as 33, 1 and 3; numbers of *E. coli*based cases were recorded, respectively, as 6, 0 and 1; numbers of *Salmonella*-based cases were recorded, respectively, as 1, 3 and 3 [66]. In a study that was made in Ankara (Turkey) with milk collected from street mostly found *S. aureus* > *E. coli* > *Klebsiella* > *Serratia* > *Proteus* [67]. In a study conducted in Czech Republic, total amount of mesophilic bacteria-TMBC (×10<sup>3</sup> CFU/ml) in conventional milk was found as 19 ± 16 (as Mean ± SD; n:1168) and amount of coliform bacteria-CBC (×10<sup>1</sup> CFU/ml) was found as 48 ± 36 (as Mean ± SD; n: 473) [21]. In low input farms in Brazil, bulk milk bacteria count (BMBC) was found higher in winter 2174 ± 958.4 (Mean ± SEM) according to other seasons. But in same season bulk tank somatic cell count (BTSCC × 1000 cells/ml) was found as 469 ± 113.4 (Mean ± SEM) [68]. In a study with raw milk in winter and summer In Slovenia, total bacteria count was found higher than 100,000 cfu/ml [69].
