Metallic Contaminants Detected in More than 60% of Edible Salts Presence of Micro-plastics in 20% of Sea Salts Showing Urgent Need for Plastic Reduction

15 April 2020
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Metallic Contaminants Detected in More than 60% of Edible Salts Presence of Micro-plastics in 20% of Sea Salts Showing Urgent Need for Plastic Reduction

Edible salt is an indispensable condiment in our daily lives. The Consumer Council tested 39 pre-packaged edible salts and found that there was a great disparity of prices and quality in all these samples. In addition, different types of edible salt were found to have harmful substances of which 2 samples of rock salt, though in compliance with the current regulations, exceeded the amendment regulations to be implemented in Hong Kong, of which the most expensive one, was found to have lead content in excess of both the Mainland and international standards. Test results also revealed more than 60% of the samples were found to contain metallic contaminants, and 1 smoked salt was detected to contain polycyclic aromatic hydrocarbons (PAHs), a substance that may lead to carcinogenicity and may pose risks to human health.

For the first time the Council discovered a variety of micro-plastics in the samples of sea salt. The micro-plastics might come from contaminated raw materials or plastic packaging. If the micro-plastics were really from contaminated raw materials, it indicated that the ocean had been polluted by lots of discarded plastic products. Other than causing marine pollution, those incomplete decomposed plastic fragments would finally find their way into the food chain. The Council calls for consumers to support a sustainable consumption lifestyle, to reduce waste at source and to minimize the use of plastic products.

The 39 samples of pre-packaged edible salt in the market tested include 19 samples of sea salt, 9 samples of rock salt/rose pink salt, 4 samples of table salt/cooking salt, 1 sample of lake salt, 4 samples of iodized salt, 1 sample of roasted salt, and 1 sample of smoked salt, with prices ranging from $2.6 to $440. The tests examined the safety and quality of the samples. The safety tests included checking contaminant contents including metallic contaminants, micro-plastics, polycyclic aromatic hydrocarbons and phthalates, and also the content of an anti-caking agent potassium ferrocyanide. The quality tests analysed the sodium chloride content, insoluble matter content, as well as the content of minerals of potassium, calcium, magnesium and iodine.

Among the edible salt categories, the samples of sea salt displayed a huge price disparity. The difference between the lowest price ($2.6) and the highest price ($63.5) is more than 23 times. However, both samples obtained an overall score of 5 points. 3 kinds of table salt/cooking salt costing $15 or less also scored 5 points. They all performed well in the tests of metal impurities, micro-plastics and plasticizer. Their overall rating was better than the $440 Himalayan rock salt that scored only 4 points. The second most expensive sample was smoked salt ($88), the only sample scoring only 1 point due to the detection of carcinogens. The test results showed that product price is not necessarily related to quality and safety. Consumers should exercise care with their choices.


In the production process of edible salts, manufacturers would try to remove contaminants and impurities in order to improve the purity and to assure the safety and quality of the finished products. However, the test results showed that at least 1 metallic contaminant was detected from 25 samples, of which the content of 23 of them did not exceed the maximum limit of current Regulations and the Amendment Regulations to be implemented in Hong Kong, as well as the limits of the Mainland standard and international standard. However, the metallic contaminant in 2 samples of rock salt exceeded the international standards, including the most pricey one ( $440)  with lead content amounting to 3mg/kg detected, exceeding the maximum limit of the Food Adulteration (Metallic Contamination) (Amendment) Regulations (Amendment Regulations) which will be implemented in Hong Kong on 1 November this year. It also exceeded the mainland standard (2mg/kg) and the maximum limit set by the Codex Alimentarius Commission (1mg/kg). For the other sample of rock salt, the total arsenic content was 0.55mg/kg, slightly higher than the maximum limit of the Amendment Regulations of Hong Kong and the Mainland standard as well as the maximum limit set by the Codex Alimentarius Commission (0.5mg/kg).

The tests also found that 1 sample of smoked salt contained carcinogenic and genotoxic polycyclic aromatic hydrocarbons (PAHs), amounting to 26.5μg/kg in total, which might emerge during the process of hot smoking. Although the Codex Alimentarius Commission has yet stipulated the maximum limit of polycyclic aromatic hydrocarbons in edible salts, due to its risks, consumers are advised to reduce its intake. The Council also urges manufacturers to make every effort to lower the content of PAHs in their products to ensure food safety and public health. 

Even though it has not been evidently proved whether the intake of micro-plastics is harmful to the body, it is found that micro-plastics would absorb certain harmful chemical substances and also release their own additives. Among the 39 samples, 4 samples of sea salt were detected to have micro-plastics, with the total content ranging from 114μg/kg to 17,200μg/kg. Polymethyl metacrylate (PMMA) was the most commonly found micro-plastic, followed by polypropylene (PP). Their presence could be related to the level of contamination of raw materials, usage rate of different types of plastics, recycling and discarding rate, as well as the stability of chemical structures in different situations such as heat, UV light and oxidation.


An anti-caking agent, potassium ferricyanide, is added to some edible salt products to prevent the formation of lumps due to temperature differences or humidity. Of the 39 samples, 33 contained potassium ferrocyanide. The additive content ranged from 1.2mg/kg to 5.8mg/kg, which was lower than the maximum limit of the mainland standards “GB 2760-2014 Standard for the Use of Food Additives” (10 mg/kg). However, 5 of the samples had the label claims of no presence of or no added anti-caking agent or additives on their packaging. The test results have been referred to the Centre for Food Safety and Customs and Excise Department.

Minerals content

Some edible salt products flaunt themselves for their richness in minerals. The test results revealed that in all the samples, calcium content was found ranging from 0mg/kg to 4,287mg/kg, magnesium content from 0mg/kg to 4,486mg/kg, and potassium from 11mg/kg to 2,534mg/kg. As a matter of fact, sodium chloride is the main ingredient in edible salt, and all samples was detected to contain 97% to 99.8% of it, while other minerals were in small amounts only. If consumers intend to absorb minerals from edible salts, they would take in a lot of sodium at the same time. The Council reminds consumers of the recommendations given by the World Health Organization that the daily sodium intake for a normal adult should be less than 2,000mg for the reduction of the risk of high blood pressure, heart disease and stroke. Therefore, it is not desirable for consumers to rely on edible salts to absorb nutrients such as magnesium, potassium, and calcium. Instead, they should maintain a balanced and varied diet for the good of their health.

In addition, the tests found that 1 of the 4 samples of iodized salt carried no iodine at all, failing to match with its packaging label stating 3,500μg of iodine/100g. Relevant manufacturers should improve information transparency by making appropriate labels, and mark clearly for those who require medical consultation before consuming iodized salts.

In general, consumers could consume sufficient iodine from food. For example, seaweed, kelp, seafood, milk and milk products, and eggs and egg products are rich in iodine, and iodized salt is also one of the options.


A lower content of water insoluble substances reflects the lower impurity in edible salt. The test results indicated that one third of the samples (13 samples) carried water insoluble substances, from 0.02 to 0.65g /100g. 8 of all tested samples failed to meet the minimum requirement of the Mainland standards (less than or equal to 0.2g/100g). Among all of these, there was 1 sample of iodized salt which had the highest water insoluble matters (0.65g/100g), exceeding the standards by more than 2 times. In the 13 samples detected with impurities, 8 of them were rock salt/rose pink salt, whereas no water insoluble matters found in the samples of all 4 table salt/cooking salt products.

The relevant test results have been sent to the Centre for Food Safety for follow up and reference. Consumers should pay attention to the following tips when buying and consuming edible salt products:

- Before making any purchase, consumers should check whether the product packaging is intact, and whether it is found unusual, discolored or having bad smells;

- Read the information on the packaging labels in detail, such as the origin, type of salt, shelf life and durability to ensure that the product has not expired;

- Edible salts should be kept in a cool and dry place, avoid exposure to the sun and stay away from stoves. The packet should be sealed after opening, lest it forms lumps with moisture, and should be used up as soon as possible;

- Excessive intake of sodium (salt) would have adverse effects on health and increase the risk of high blood pressure, hence a balanced and varied diet should be maintained;

- Women preparing for pregnancy, those in pregnancy or breastfeeding, and those suffering from thyroid-related diseases, should consult their healthcare professionals before taking iodized salt.

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