Accumulation of Arsenic and Cadmium in Foods of Animal Origin Collected from the Local Markets in Northeastern Region Thailand

Concentrations of arsenic and cadmium were determined in broiler chickens, cattle and swine collected from the local markets of the northeastern Thailand. Average concentrations of arsenic based on a wet weight basis in muscle, liver and kidney were 0.022±0.008, 0.068±0.025, 0.286±0.073 μg/g P Pcattle; 0.045±0.022, 0.402±0.096, 0.812±0.335 μg/g chickens; and 0.116±0.044, 0.479±0.142, 1.012±0.500 μg/g swine, respectively. Cadmium levels in meat of cattle, chickens and swine samples were 0.024±0.010, 0.028±0.006 and 0.042±0.015 μg/g, respectively. In liver and kidney, average of cadmium levels was 0.286±0.062 and 0.412±0.074 μg/g cattle; 0.312±0.092 and 0.645±0.068 μg/g chickens and 0.368±0.106 and 0.758±0.120 μg/g swine, respectively. Statistical analysis showed that chickens and swine levels were higher of these elements than in cattle. None of samples, however, exceeded the arsenic limits set by Thailand regulations and the average concentrations of cadmium in animal tissues were still within acceptable levels of Thailand standards.


INTRODUCTION
Arsenic and cadmium are known to produce a range of toxic effects including carcinogenic and noncarcinogenic effects in both animals and humans (ATSDR (Agency for Toxic Substances and Disease Registry), 2007, 2008;Goyer and Clarkson, 2001).Environmental pollution from various sources, such as untreated municipal and industrial wastewater, leads to foodstuffs from animal origin contaminated with arsenic and cadmium.Animals can accumulate heavy metals via intake of contaminated feed, soil, water and then these animal tissue residues of heavy metals can be harmful to human health who consumes the meat and visceral organs.Arsenic and cadmium accumulation in the environment and foods of animal origin have become a problem of increasing concern due to their use in many industrial processes and anthropogenic activities and their potential toxicity on public health (WHO, 2001(WHO, , 2002)).
A number of studies have reported a large variability in arsenic and cadmium levels in foods and environments from differences countries.Recent studies of arsenic and cadmium problems have been reported in some areas of Thailand such as the Ronphibun area in the southern part and in the Tak province in the northern part (Ruangwises and Saipan, 2010;Simmons et al., 2005;Swaddiwudhipong et al., 2007;Teeyakasem et al., 2007;Zwicker et al., 2010).Thailand is administratively divided into 4 regions (77 provinces) with the approximately 63,878,267 inhabitants.The northeastern region is the largest area with an approximate population of 21,573,318 living in 20 provinces (NSO (National Statistical Office), 2012).The economic growth and increasing population of the northeastern part Thailand may lead to a large emission and contamination of heavy metals.Potential sources of arsenic and cadmium in this area are mining, industry, agriculture and urban sewage.At this time, there is little published data available regarding on the actual levels of arsenic and cadmium in foods of animal origin from the northeastern region.The production of cattle, broiler chickens and swine in this area are approximately 3,354,335, 66,763,425 and 1,520,591 head (NSO (National Statistical Office), 2012).Most of broiler chickens and swine are raised by business farmers while cattle are reared by local farmers.Generally, cattle are consumed locally and the other foods of animal origin sometimes are sold to nearby provinces.Heavy metals released from anthropogenic activities may be accumulated in the tissues of animals through the food chain.Internationally published reports on arsenic and cadmium levels in terrestrial animals from Thailand (Franke et al., 2007;Sridaoruang et al., 2010;Yatmark et al., 2010) are limited.Thus, this study was designed to determine the present arsenic and cadmium concentrations in cattle, broiler chickens and swine in northeastern Thailand.

MATERIALS AND METHODS
Samples of muscle, liver and kidney from the cattle, broiler chickens and swine were purchased from the local markets in the 4 provinces of northeastern Thailand with the highest populations.Samples were collected five times from each province.The same part of each tissue, the upper hind right leg, right lobe of liver and right kidney tissues were collected from cattle and pigs and whole broiler chickens, were collected, kept in polyethylene bags, placed in iceboxes and transported to the laboratory.Each sample was dissected, connective tissue removed, homogenized and kept at -18°C until analysis.A total of 180 samples were analyzed in this study and samples were collected between February and October 2013.
Arsenic and cadmium in samples were determined by a modified method of Wlostowski et al. (2006).Briefly, 0.5 g of wet sample was digested overnight in 10 mL of concentrated nitric acid.Then, 2.5 mL of perchloric acid (70%, v/v) was added and evaporated on a hot plate and mineralized at 450°C in a muffle furnace for 3 h.The residue was left for 30 min; 10 mL of nitric acid (10%, v/v) was added and was then filtered through a Whatman no.41 filter paper and adjusted to volume with nitric acid (10%, v/v).Inductively Coupled Plasma Mass Spectrometry (ICP-MS, Agilgent 7500C, Octopole Reaction System, Tokyo) at the Central Laboratory, Co. Inc., Thailand, was used to determine arsenic and cadmium in the solutions.Calibration standards were prepared by using samples fortified with certified stock solutions of arsenic and cadmium (Fluka, UK) with 0.1% HNO 3 at four different concentrations of each element and blank samples that were not fortified with elements.Standard stock solutions containing 1000 mg/L of each element were purchased from Fluka (UK) and were used to prepare calibration standards.HNO 3 and HClO 4 were purchased from Merck Chemicals (Darmstadt, Germany); other chemicals were obtained from Sigma-Aldrich (St. Louis, MO).Deionized water (18 MΩ cm) was used for preparation of standards, reagents and samples throughout the study.All glassware was treated with 10% (v/v) HNO 3 for 20-24 h and washed three times with deionized water.
Standard reference material (SRM 1577b bovine liver, NIST, USA) was used to verify the accuracy of the determinations.The recovery rates of arsenic and cadmium were ranges 90.86-102.50 and 89.45-98.20%.The relative standard deviations were less than 10% for all investigated elements.The analytical limit of detection of arsenic and cadmium were 0.02 and 0.004 µg/g.The concentrations of arsenic and cadmium found in the standard reference material were 0.06±0.02and 0.52±0.04µg/g (n = 5) which were in good agreement with the values of 0.05 (value not certified) and 0.5±0.03(value certified) µg/g.In this study, heavy metal levels were expressed as µg/g wet weight.
One-way analysis of variance and the Turkey test were used to test for differences among the different tissues of the same species and among tissues of different species of animals by using SPSS Statistics version 17.0 for Windows (SPSS, Inc., Chicago, IL, USA).The level of significance accepted for all comparisons was p<0.05.

RESULTS AND DISCUSSION
The age of cattle, swine and broiler chicken samples used in this study ranged from 3 to 6 years, 6 to 7 months and 40 to 50 days and average weights were 350±38.25 kg for cattle, 110±16.50kg for swine and 2.05±0.28kg for broiler chickens.Kidney and liver samples of all animals detected arsenic and cadmium more than the limits of detection, while 4.44% (8 of 180 samples) and 3.89% (7 of 180 samples) of muscle samples were below the detection limits of arsenic and cadmium.Table 1 shows concentrations of arsenic on the basis of wet weight.None of samples exceeded the total arsenic limits set by Thai organization as 0.5 µg/g muscle and 2 µg/g offal (National Bureau of Agricultural Commodity and Food Standards of Thailand (ACFS, 2005).
Cadmium concentrations were determined in all tissues and animals shown in Table 2.The ranges of cadmium levels were not detectable to 1.510 µg/g.The highest level of cadmium was detected in kidneys of pigs as 1.510 µg/g.Cadmium concentrations in muscle samples were no different among cattle, swine and broiler chicken (p>0.05).An average of cadmium concentrations in liver samples was lower when compared with the residue levels in kidneys of all species.Similar to other studies, the kidney is the critical tissue of accumulated cadmium and generally cadmium levels in muscle of foods animal origin were low (Alonso et al., 2000;Doganoc, 1996;Falandysz, 1993;Salisbury et al., 1991).Yatmark et al. (2010) reported that cadmium levels in the kidneys of cattle and swine collected from cadmium-contaminated area of Maesot district, Tak province, Thailand ranged from 0.02 to 19.60 and 0.09 to 40.14 µg/g wet wt and 51% of kidney samples contained cadmium levels higher than the maximum limits (1 µg/g wet wt).The present study showed that cadmium levels were lower than those reported by Yatmark et al. (2010) but similar to the results found by Sridaoruang et al. (2010) study.Regulatory limits of cadmium in foods vary among countries.Thailand regulatory limits for cadmium in kidney, liver and muscle of all three animals are 1, 0.5 and 0.05 µg/g wet wt (ACFS, 2005; DLD, 2006).From  Table 2, the levels of cadmium in muscle samples of all animals were lower than the permitted level set by Thailand organizations except for cadmium in some kidney (4 of 60 samples, 6.67%) and liver (3 of 60 samples, 5%) samples were above the acceptable levels, similar to Miranda et al. (2001).They suggested that 1 to 15% of kidney samples in many countries studied have cadmium levels above 1 µg/g.Statistical analysis showed that arsenic levels in liver and kidney samples of chickens and swine were significantly (p<0.05)higher than those in cattle samples.Cadmium levels measured in the meat and liver of the three animals were not significantly different among them but significant differences in kidney samples (p<0.05).The highest cadmium concentrations were found in swine.The other details of statistical analysis are shown in Table 3.
In a report from, Franke et al. (2007), they reported the arsenic concentrations in poultry meat collected from Thailand.The reported average level of arsenic was 0.141±0.042µg/g wet wt (n = 3).In this present study, concentrations of arsenic found in poultry meat were 0.045±0.022µg/g wet wt, lower than the level reported by Franke et al. (2007).Lopez -Alonso et al. (2002) and Miranda et al. (2005) studies showed that arsenic levels in the cattle samples ranged of 0.004 to 0.055 and were non-detectable to 0.593 µg/g wet wt, similar or slightly below those levels found in the present study.Delgado-Andrade et al. (2003) presented high levels of arsenic in bovine samples (non-detectable to 3.249 µg/g) when compared with the results in this study.Arsenic in broiler chicken samples in the present study were higher than those levels in the U.S.A. report by Tao and Bolger (2009), (0.030 to 0.086 µg/g wet wt), but lower than those concentrations found in Shah et al. (2009) who reported levels of 2.15 to 7.17 µg/g wet wt.Jorhem et al. (1991) presented average arsenic concentrations in swine meat, liver and kidney were 0.024, 0.023 and 0.019 µg/g wet wt, respectively below the levels arsenic were determined in this study.Additionally, arsenic in chickens and porcine samples were about 7 to 12 times higher than average concentrations found in the other species reported by Salisbury et al. (1991) and similar to the present study, arsenic levels in chickens and swine were 3.54 to 7.04 times higher than mean levels of arsenic presented in cattle tissues.
When compared to the cadmium levels reported from other countries, Cai et al. (2009), Miranda et al. (2005) and Sedki et al. (2003) reported that cadmium levels in bovine organs ranged in the not detectable range to 38.3 µg/g.In swine and broiler chicken studies, cadmium concentrations varied between nondetectable and 40.14 µg/g (Doganoc, 1996;Ihedioha and Okoye, 2012;Kumar et al., 2007;Swaileh et al., 2009;Tomovic et al., 2011;Villar et al., 2005;Yatmark et al., 2010).The present results obtained from foods of animal origin were comparable to those found in other studies.It is difficult, however, to directly compare arsenic and cadmium concentration data because the residue magnitude can be influenced by the type and age of the animals and concentrations and rates of exposure to the elements.In general, arsenic and cadmium levels in tissues of food animal origin may be increased with age and related to those concentrations in feedstuffs.
Environmental contamination has an effect on heavy metal levels in tissues of animals who ingested contaminated water and feedstuffs (Farmer and Farmer, 2000;Miranda et al., 2005;Sedki et al., 2003).The differences of heavy metals levels in soil and surface water will result in differences in contamination levels of plants and feedstuffs.Limited data, however, on heavy metals levels in animals and feedstuffs from the different environmental areas of Thailand are available.Thus, further monitoring of the foods of animal origin, feedstuffs, soil and water to assess the status of heavy metals contamination is necessary.

CONCLUSION
In the present study, arsenic and cadmium concentrations were comparable to those found in other country studies and it may be concluded that the average concentration of arsenic and cadmium in foods of animal origin from northeastern Thailand were still within acceptable levels.Arsenic and cadmium contents in all tissues of broiler chicken and swine tended to higher levels than cattle.A lack of data published in Thailand, however, has resulted in difficulty to compare of the magnitude of the problem of residues in foodstuffs from the different terrestrial animals.
columns in each element are significant as p<0.05

Table 3 :
Comparison of arsenic and cadmium levels among tissues and animals (µg/g wet wt)