The hectic life of Hong Kong people deprives them of eating regularly and canned sardines, tunas and daces are among the most popular stocks in most households. From the Consumer Council’s test on 46 samples of canned fish, all were found to contain various types and levels of metallic contaminants, mainly arsenic, mercury, cadmium and lead. Cadmium, known for chronic poisoning if excessive intake, was detected in 90% of the sardine samples and 60% of the tuna samples. Over 70% of the sardine samples and more than 10% of the tuna samples were found to contain inorganic arsenic which is relatively toxic to human beings and prolonged intake would lead to neurologic and cardiovascular diseases.
Moreover, nearly half of the sardine samples were found to contain polychlorinated biphenyls (PCBs) which is a carcinogenic contaminant. In addition, 90% of the tuna samples was found to have methylmercury, a contaminant that could hinder the development of the foetuses’ nervous systems and could lower the intelligence of young children. The Council is deeply concerned about the potential food safety risk in canned fish posed by environmental pollution and the raw materials used in fish farming. The Council also urges the industry to implement stringent controls in all areas in order to minimize the food safety risk.
The test also revealed that all canned fish samples were rich in protein content, and the average calcium content in daces ranked the highest amongst the 3 types of fishes but its sodium level is also the highest. As canned fishes are prepared with sauce, consumers are advised to avoid excessive intake in order to minimize the health risks such as hypertension, stroke and cardiovascular diseases.
The Council tested 46 canned fish samples covered 19 sardines, 20 tunas and 7 daces with prices ranging from $7.8 to $149. The metallic contaminants being tested on the fish samples included cadmium, arsenic, inorganic arsenic, lead, mercury and methylmercury, etc. Also covered in the test were the levels of food dyes and PCBs while nutrients including energy, protein, total fat, saturated fat, trans fat, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), carbohydrates, sugars, sodium and calcium were also tested.
Sardines Samples Detected with the Highest Level of Metallic Contaminants and PCBs
Sardines were found to contain the highest average level of cadmium among the 3 types of canned fish tested with tunas came second while cadmium was not detected in daces. Excessive intake of cadmium could lead to chronic poisoning or irreversible kidney malfunction. 17 (nearly 90%) out of the 19 sardines samples were detected with cadmium where 2 samples claimed to be originated from Thailand were found to have 0.13mg and 0.11mg cadmium per kg respectively, slightly exceeding the maximum level of 0.1mg stipulated in the Food Adulteration (Metallic Contamination) (Amendment) Regulation 2018 (the Amendment Regulation) which will become effective on 1 November this year. Another sardine sample claimed to be originated from Morocco was detected with cadmium level reaching the same maximum level. The overall cadmium level detected in the tuna samples was low and at the acceptable level of the Amendment Regulation. The Council has relayed the above test results to the Centre for Food Safety (CFS) for reference. While canned fish is categorized as a kind of compounded food under Amendment Regulation, this type of food should not be measured as the same as raw fish in measuring the level of contaminants; however, the Council compared the test results with the maximum levels stipulated in the Amendment Regulation for consumers’ reference.
PCBs is a kind of industrial contaminant. It has long existed in the environment and can accumulate in the fatty tissues of animals that will ultimately accumulate in human bodies through the food chain. It is categorized as “Carcinogenic to Humans” by International Agency for Research on Cancer. 9 sardine samples were found to have dioxin-like polychlorinated biphenyls (DL-PCBs) while 6 sardine samples were detected with non-dioxin-like polychlorinated biphenyls (NDL-PCBs). A sardine-in-oil sample claimed to be originated from Spain was found to contain the highest level of both DL-PCBs and NDL-PCBs among all samples although they were still within the EU maximum level. For a child weighed 35kg and an adult of 60kg, daily consumption of 26g (0.4 can) and 44g (0.6 can) of this sample respectively would exceed the tolerable daily intake limit on NDL-PCBs adopted by some European countries; however, consumers need not be overly worried as health risk would only become significant upon a prolonged period of daily intake exceeding such level.
Sardines have various health benefits. The average level of sum of omega-3 fatty acids DHA and EPA ranked highest among the 3 kinds of canned fish tested and outweighed tunas, which ranked second, by 3.5 times. DHA and EPA could help prevent heart diseases and stroke. It is also beneficial to the brain and the visual developments of foetuses.
Tunas Samples have the Highest Average Level of Methylmercury
Higher Risk Posed to Foetuses and Kids than Adults
The average level of methylmercury detected in tuna samples was higher than those detected in the dace and sardine samples. Methylmercury is the most toxic form of mercury and could damage the nervous systems of human beings. 18 tuna samples (90%) were found to contain 0.06mg to 0.28mg of methylmercury per kg. A tuna in olive oil sample claimed to be originated from Spain was found to have the highest level of methylmercury, reaching half of the maximum level stipulated in the Amendment Regulation. For a child weighed 35kg and a woman within the childbearing age weighed 60kg, weekly intake of 2.5 cans and 4 cans of this tuna sample respectively would exceed the provisional tolerable weekly intake limit set by the Joint FAO/WHO Expert Committee on Food Additives (JECFA).
The Council reminds consumers that for tuna fish, species of bigger size e.g. albacore tuna, may contain higher level of metallic contaminants compared to species of smaller size. Foetuses and children are more prone to the adverse health effects posed by methylmercury as their brains are still developing. Excessive intake would lead to a decrease in intelligence of toddlers.
Total arsenic was detected in all tuna and sardine samples, but the detected levels were within the maximum level stipulated in the Food Adulteration (Metallic Contamination) Regulations.
Daces were Rich in Calcium
Yet all Samples were classified as High-Sodium Food
In contrast to sardines, all dace samples had a low level of metallic contaminants and PCBs while the average level of calcium ranked the highest among the 3 categories of canned fish tested. The calcium level of the dace samples was 70% higher than that of the sardine samples; however, the sodium level detected in dace samples were also the highest. Taking reference from CFS, all 7 dace samples were high-sodium food (more than 600mg sodium per 100g) while only 4 sardines in sauce samples and just 1 tuna in oil samples were found to contain high-sodium. The World Health Organization recommends that the maximum level of sodium intake should not exceed 2000mg per day (equivalent to about 5g of salt or just under a teaspoon of table salt). In the test, all sauce, salt water and other ingredients were already sifted out, but the sodium level of the dace samples was still high. The Council advises consumers not to consume canned fish together with the sauce and other ingredients to avoid excessive intake of sodium.
All 3 types of canned fish were found to be rich in protein and all met the definition of high-protein food under the Food and Drugs (Composition and Labelling) Regulations. The most expensive sample was a tuna in oil sample claimed to be originated from Spain and was priced at $149 per can. While its total content of DHA and EPA was exceptionally high, its inorganic arsenic level was also the highest among all samples, reaching 90% of the maximum level stipulated in the Amendment Regulation. This sample was also the only tuna sample detected with both DL-PCBs and NDL-PCBs. For a child weighed 35kg, consumption of about 1 can of this sample would exceed the tolerable daily intake level of NDL-PCBs; however, health risk would only be increased upon a prolonged daily consumption exceeding this amount.
Consumers should note the following when purchasing or consuming canned fish：
- Pregnant women, women planning to get pregnant and young children should refrain from consuming large predatory fishes in order to avoid excessive intake of methylmercury. CFS notes that the risks of methylmercury in consuming fishes such as albacore tunas and yellowfin tunas outweigh the benefits of DHA and EPA contained in them;
- Follow a balanced diet. Consuming different kinds of fishes helps avoid excessive exposure to a particular contaminant;
- Canned fish like sardines and daces would have their bones softened after thermal and pressurized processing. Consumers should eat the bones altogether to absorb more calcium and should reduce eating the salted black beans, sauce and other ingredients together; otherwise, the sodium intake would be higher than that of eating the fish alone;
- Food content inside dented, damaged or swollen cans should not be consumed. If rust is found inside, the whole can should be discarded;
- Canned food should be consumed right after opening. Leftover food should be stored in the refrigerator. Do not store food with the original can.
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