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Lab analysis of heavy metals in food should be conducted
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Monday, 31 August, 2015, 08 : 00 AM [IST]
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Mayuree Leelavachiropas and Naphatip Rodchuei
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fiogf49gjkf0d Though the general perception is that heavy metals like mercury, lead and arsenic have very little chance to enter human bodies, the fact is that these can be easily absorbed into the body through elements like earth, water, and air, as well as sources as varied as food, cosmetics and kitchen appliances. The causes of contamination could be manufacturing process, raw materials used and chemicals released from many types of factories.
Heavy metals can be described as metals that have a density of more than five gram per cubic centimetre namely mercury, lead and arsenic. These toxins, when collected in the body to a certain level, will show their effect. The results of toxicity of heavy metals to cell mechanisms can be categorised into five types as follows; Causing cells to die; Changing the structure and functions of cells; Causing cancer; Causing genetic disorders; and Causing damages to chromosome which is a genetic factor.
Mercury
This metal is mostly found in air, water and soil, caused by fuel combustion, incineration, waste of household products and factories using mercury as its raw material such as paper pulp plant, plastic factory, pharmaceuticals factory and coal-fired power plant.
Furthermore, mercury is often found in cosmetics and food especially seafood and big aquatic animals such as sharks, tuna, dolphins and whales as they live longer lives and feed on small fish, which results in having more mercury in their bodies (called biomagnification). The belief that shark fins are rich in nutrition may not always be correct. The contamination of mercury in natural water resources is caused by factories releasing mercury with its wastewater.
The most severe incident regarding mercury happened in Minamata, Japan, in 1953, causing “Minamata disease.” It is caused by eating fish caught in Minamata bay which was contaminated with mercury. While many people were afflicted with central nervous system problems, many children suffered brain problems.
Lead
An individual may absorb lead directly from food, water or even breathing. People with risk of lead poisoning are workers in lead mines, battery factory, electronic and computer parts factory, paint factory, herbicide factory and people residing near lead melting factory or factories using lead as its raw material, traffic police and people in the traffic jam area.
Arsenic
It is mostly found in vegetables, fruits, water, seafood, cosmetics and traditional drugs and is an important component of herbicide factory, leather tanning industry and iron smelting factory. When arsenic is absorbed into body through breathing or consuming contaminated food, it will enter various parts of the body like blood, urine, hair and other tissues in different amounts. Arsenic will become toxic when being absorbed into body for a long time.
The causes of metal contamination in food are a natural cycle of food chain, cycle of industrial waste and cycle of food production. Therefore, it shows that no matter what kind of packages food comes in, if the ingredients are contaminated with heavy metals since cultivation, that product will always contain heavy metals. Meanwhile, if the ingredients are clean but production and packaging processes are not up to the standard, the products will be contaminated with heavy metals as well. Therefore, every agency responsible for consumer protection has issued a law to control the safety of products for consumers. To know whether food is contaminated with heavy metals, the analysis from the lab specialising in heavy metals must be conducted.
For the test to find the amount of lead and heavy metals, the appropriate and nationally and internationally accepted analysis methods must be carried out. The National Food Institute (NFI) implements AOAC to test lead and heavy metals in food which is an internal standard method, certified by ISO/IEC 17025 by the department of medical sciences.
The equipment used in the analysis process of lead and heavy metals has been maintained and calibrated according to the plan at least once a year to prepare the equipment for effective use. The equipment NFI uses to analyse are as follows:
1. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES): It is a technique that can analyse many types of heavy metals at a time by using plasma to dissolve the sample into atoms or ions. The sample will be stimulated until reaching the stage of emitting the light at the specific wavelength of each type of metals. The light emitted will relate to the density of each metal. This technique can test at the lowest level of part-per-billion (ppb).
2. Atomic Absorption Spectroscopy (AAS): It is a technique that can analyse only one kind of heavy metals at a time. This technique uses fire to dissolve the sample into an independent atom. When the light with the specific wavelength of each type of metals is shone to a group of independent atom, the atom will absorb the light. The absorption light will relate to each metal. Flame AAS can test at the lowest level of part-per-million (ppm).
3. Inductively Coupled Plasma Mass Spectrometry (ICP-MS): It is a technique that uses plasma as well to dissolve the sample into atoms and ions like ICP-OES but the detector is different. ICP-MS does not detect the amount of light but rather the ions. The ions will be sorted out from the difference of mass to charge ratio of each type of ion. This technique can test at the lowest level of part-per-trillion (ppt)
The analysis of heavy metals in each type of food is conducted with different methods. The test of contaminants and the standard criteria are proved to be a challenge for every lab. No matter how low the criteria is, the method must comply with laws. Therefore, since every type of food is important to analysts, they need to apply the right and most appropriate method. For example, if you must conduct a test on amount of copper in good at ppm level in one time before the results are submitted to clients, the AAS tool is therefore the most appropriate for the work. But if you want to test 23 types of heavy metals in drinking water, the technique that can analyse many types of heavy metals at once must be applied like ICP-OES and so on. The tool used to test lead and heavy metals in the food sample is AOAC (2012). The sample must be dissolved by acid to turn it into a solution before being analysed with ICP-OES or AAS. The analysis of heavy metals in a water sample must use AWWA (2012) method and ICP-OES tool.
Testing methods that cover the national and international criteria are Codex EU, Ministry of Public Health, The National Bureau of Agricultural Commodity and Food Standards, Thai Industrial Standards Institute etc.
The limit of detection (LOD) of the National Food Institute’s lab can be measured by an analysis method that has been approved with the limit in accordance with contaminant provisions of The National Bureau of Agricultural Commodity and Food Standards 9007-2005, Ministry of Public Health and EU as shown in the table.
The requirements of contaminants of ACFS 9007-2005
1. Requirements of contaminants in plants and their products.
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| Items | Contaminants | Maximum level (ML;mg/kg) | LOD (Testing conducted by NFI) (mg/kg) | | 1. Fruit and vegetable products in sealed container |
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| | 1.1 All kinds of vegetables | Tin | 250 | 0.73 | | 1.2 Cruciferous vegetables (Brassica), bulb and fruiting vegetables | Cadmium | 0.05 | 0.01 | | 1.3 Leafy vegetables | Cadmium | 0.2 | 0.01 | | 1.4 Other vegetables in addition to Article 1.2 and 1.3. | Cadmium | 0.1 | 0.01 | | 1.5 Cruciferous (brassica) and Leafy vegetables | Lead | 0.3 | 0.01 | | 1.6 Bulb, Fruiting vegetables and Roots and tubers | Lead | 0.1 | 0.01 | | Lead | Lead | 0.2 | 0.01 | | 1.8 All fruits | Tin | 250 | 0.73 | | 1.9 Fruits of the berries and small fruits | Lead | 0.2 | 0.01 | | 1.10 Other fruits in addition to Article 1.9 | Lead | 0.1 | 0.01 | | 1.11 Fruit juices sealed in containers | Lead Tin | 0.05 200 | 0.01 0.73 | | 1.12 Apple juice in a sealed container | Lead Tin | 0.05 200 | 0.01 0.73 |
2. Requirements of contaminants in Livestocks and their products.
| Items | Contaminants | Maximum level (ML;mg/kg) | LOD LOD (Testing conducted by NFI) (mg/kg) | | 1.Chilled or Frozen Meat |
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| | 1.1 Fresh chilled or frozen meat |
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| | - Poultry meat - Poultry offal | Lead | 0.1 0.5 | 0.02 0.02 | | - Poultry meat - Poultry liver - Poultry kidney | Cadmium | 0.05 0.5 1.0 | 0.02 0.02 0.02 | | - Poultry meat - Poultry offal | Total arsenic | 0.5 1.0 | 0.002 0.002 | | 1.2 Fresh chilled or frozen pork |
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| | -Pork meat - Pork offal | Lead | 0.1 0.5 | 0.02 0.02 | | - Pork meat - Pork liver - Pork kidney | Cadmium | 0.05 0.5 1.0 | 0.02 0.02 0.02 | | - Pork meat - Pork offal | Total arsenic | 0.5 1.0 | 0.002 0.002 | |
2. Meat Thermal |
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| | 2.1 Thermal in poultry meat
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| The criteria set out in Article 1.1 of contaminated fresh chilled or frozen meat. |
| | 2.2 Thermal in pork meat
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| The criteria set out in Article 1.2 of contaminated fresh chilled or frozen pork. |
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3. Requirements of contaminants in fish and fish products.
| Items | Contaminants | Maximum level (ML;mg/kg) | LOD (Testing conducted by NFI) (mg/kg) | | 1.Chilled or frozen shrimp | Cadmium Total mercury Lead | 0.5 0.5 0.5 | 0.002 0.001 0.02 | | 2. Shrimp in a sealed container | Cadmium Total mercury Lead | 0.5 0.5 0.5 | 0.002 0.001 0.02 | | 3. Tuna in a sealed container | Cadmium Total mercury Lead
| 0.1 1.0 0.4 | 0.002 0.001 0.02
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The Notification of the Ministry of Public Health
(No. 61) (B.E.2524)
Re: Drinking Water in Sealed Container
| Contaminants | Maximum level (ML;mg/L) | LOD (Testing conducted by NFI) (mg/kg) | | Arsenic | Less than 0.05 | 0.00029 | | Barium | Less than 1.0 | 0.00008 | | Cadmium | Less than 0.01 | 0.00066 | | Chromium | Less than 0.05 | 0.00076 | | Copper | Less than 1.0 | 0.00088 | | Iron | Less than 0.5 | 0.00010 | | Lead | Less than 0.1 | 0.00237 | | Manganese | Less than 0.05 | 0.00004 | | Mercury | Less than 0.002 | 0.00012 | | Selenium | Less than 0.01 | 0.00017 | | Silver | Less than 0.05 | 0.0012 | | Zinc | Less than 5.0 | 0.00102 |
The Notification of the Ministry of Public Health
No. 135 (B.E. 2534)
Re: Drinking water in sealed containers (No.2)
| Contaminants | Maximum level (ML;mg/L) | LOD (Testing conducted by NFI) (mg/L) | | Arsenic | Less than 0.05 | 0.00029 | | Barium | Less than 1.0 | 0.00008 | | Cadmium | Less than 0.005 | 0.00066 | | Chromium | Less than 0.05 | 0.00076 | | Copper | Less than 1.0 | 0.00088 | | Iron | Less than 0.3 | 0.00010 | | Lead | Less than 0.05 | 0.00237 | | Manganese | Less than 0.05 | 0.00004 | | Mercury | Less than 0.002 | 0.00012 | | Selenium | Less than 0.01 | 0.00017 | | Silver | Less than 0.05 | 0.0012 | | Zinc | Less than 5.0 | 0.00102 | | Aluminum | Less than 0.2 | 0.00048 |
COMMISSION REGULATION (EC) No 1881/2006
of 19 December 2006
setting maximum levels for certain contaminants in foodstuffs
(Text with EEA relevance)
Maximum levels for certain contaminants in foodstuffs (1)
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| Foodstuffs (1) | Maximum levels (mg/kg wet weight) | LOD (Testing conducted by NFI)
(mg/kg) | | Lead |
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| | Raw milk (6), heat-treated milk and milk for the manufacture of milk-based products | 0,020 | 0.01 | | Infant formulae and follow-on formulae (4) (8) | 0,020 | 0.01 | | Meat (excluding offal) of bovine animals, sheep, pig and poultry (6) | 0,10 | 0.02 | | Muscle meat of fish | 0,30 | 0.01 | | Vegetables, excluding brassica vegetables, leaf vegetables, fresh herbs and fungi (27). For potatoes the maximum level applies to peeled potatoes | 0,10 | 0.01 | | Fruit, excluding berries and small fruit (27) | 0,10 | 0.01 | | Fruit juices, concentrated fruit juices as reconstituted and fruit nectars (14) | 0,050 | 0.01 | | Cadmium |
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| | Muscle meat of the following fish (24) (25): anchovy (Engraulis species) bonito (Sarda sarda) common two-banded seabream (Diplodus vulgaris) eel (Anguilla anguilla) grey mullet (Mugil labrosus labrosus) horse mackerel or scad (Trachurus species) louvar or luvar (Luvarus imperialis) sardine (Sardina pilchardus) sardinops (Sardinops species) tuna (Thunnus species, Euthynnus species, Katsuwonus pelamis) wedge sole (Dicologoglossa cuneata | 0,10 | 0.02 | | Muscle meat of swordfish (Xiphias gladius) | 0.30 | 0.02 | | Cereals excluding bran, germ, wheat and rice | 0.10 | 0.01 | | Bran, germ, wheat and rice | 0.20 | 0.01 | | Soybeans | 0.20 | 0.01 | | Stem vegetables, root vegetables and potatoes, excluding celeriac (27). For potatoes the maximum level applies to peeled potatoes | 0,10 | 0.01 | | Mercury |
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| | Fishery products (26) and muscle meat of fish (24) (25), excluding species listed in 3.3.2. The maximum level applies to crustaceans, excluding the brown meat of crab and excluding head and thorax meat of lobster and similar large crustaceans (Nephropidae and Palinuridae) | 0,50 | 0.001 | | Muscle meat of the following fish (24) (25): anglerfish (Lophius species) atlantic catfish (Anarhichas lupus) bonito (Sarda sarda) eel (Anguilla species) emperor, orange roughy, rosy soldierfish (Hoplostethus species) grenadier (Coryphaenoides rupestris) halibut (Hippoglossus hippoglossus) marlin (Makaira species) megrim (Lepidorhombus species) mullet (Mullus species) pike (Esox lucius) plain bonito (Orcynopsis unicolor) poor cod (Tricopterus minutes) portuguese dogfish (Centroscymnus coelolepis) rays (Raja species) redfish (Sebastes marinus, S. mentella, S. viviparus) sail fish (Istiophorus platypterus) scabbard fish (Lepidopus caudatus, Aphanopus carbo) seabream, pandora (Pagellus species) shark (all species) snake mackerel or butterfish (Lepidocybium flavobrunneum, Ruvettus pretiosus, Gempylus serpens) sturgeon (Acipenser species) swordfish (Xiphias gladius) tuna (Thunnus species, Euthynnus species, Katsuwonus pelamis) | 1,0 | 0.001 | | Tin (inorganic) |
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| | Canned foods other than beverages | 200 | 0.73 | | Canned beverages, including fruit juices and vegetable juices | 100 | 0.73 | | Canned baby foods and processed cereal-based foods for infants and young children, excluding dried and powdered products | 50 | 0.73 | | Canned infant formulae and follow-on formulae (including infant milk and follow-on milk), excluding dried and powdered products | 50 | 0.73 | | Canned dietary foods for special medical purposes (9) (29) intended specifically for infants, excluding dried and powdered products | 50 | 0.73 |
(Leelavachiropas is manager, laboratory service, and Naphatip Rodchuei is senior analyst, with National Food Institute,
ministry of industry,Thailand)
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