01

On the morning of July 16, the Hong Kong Consumer Council announced the results of a test involving 30 commercially available bottled waters. Among these samples, bottled waters from Chinese mainland brands Baisuishan and Nongfu Spring were found to contain 3 micrograms of bromate per liter, which meets the EU's bromate limit for natural mineral water and spring water treated with ozone, but is lower than the drinking water standards of the United States, Japan, the United Kingdom and the World Health Organization (WHO). The WHO's bromate limit is 0.01 mg/L, while the EU standard is 0.003 mg/L and the US is 0.01 mg/L.

It is worth noting that China's new national standard "Drinking Natural Mineral Water" that is about to be implemented will also limit the concentration of bromate in mineral water, and initially stipulates that the bromate concentration shall not exceed 0.01 mg/L.

In response to the test results of the Hong Kong Consumer Council, Nongfu Spring Company sent a lawyer's letter to it, pointing out that there are three major problems in the Hong Kong Consumer Council's evaluation: incorrect application of standards, errors in the judgment of standards, and lack of professionalism and misleading evaluation language. Nongfu Spring requires the Hong Kong Consumer Council to immediately clarify these issues, publicly apologize, and take measures to eliminate the adverse effects caused by them.

02

The actions of the Hong Kong Consumers Association are indeed a bit confusing. We can only hope that they will stop being double-standard in the future and continue to serve as the last line of defence for food safety for Hong Kong and mainland consumers.

Let me say a few more words about bromate.

The formation mechanism of bromate is relatively complex and is affected by many factors. In simple terms:Generally, water does not contain bromate, but generally contains bromide. When O3 is used to disinfect drinking water, bromideIt will react with O3 to form bromate.

In 1983, Haag et al. proposed the formation mechanism of BrO3- during O3 oxidation. Br- is oxidized by O3 to OBr-, and OBr- is further oxidized by O3 to form BrO3-; moreover, OBr- will also react with O3 and be converted into Br- again. In 1994, Von et al. proposed two pathways for the formation of BrO3- during O3 oxidation: direct oxidation by O3 and HO·(hydroxyl radical)) oxidation. Br－ is oxidized by O3 to hypobromous acid(HOBr), HOBr is further oxidized by O3 and HO· (hydroxyl radical) to generate BrO3-. In 1998, Von et al. perfected the formation mechanism of BrO3-[1]:

① Br- is oxidized by O3 to generate intermediate HOBr/OBr-, and HOBr/OBr- is further oxidized by O3 and HO· to ​​generate BrO3-.

② Br－ reacts with HO· to ​​generate atomic bromine(Br·), Br· is directly oxidized by O3 to form bromine oxide free radical(BrO·), BrO· bypasses HOBr/OBr－ and further generates BrO3－.

It can be seen from this that the generation pathway of BrO3- is very complex, and O3 and HO· may participate in the conversion of Br- at the same time.

Bromate formation mechanism

03

About the hazards of bromate: Long-term intake of drinking water containing bromate may cause multiple negative effects on human health.

1. Cancer risk: The most concerning thing is the carcinogenicity of bromate. Although direct evidence is not yet completely clear, several animal experiments have shown that high doses of bromate can induce certain types of cancer, especially thyroid tumors.Studies have shown that when people drink drinking water with a bromate content of 5.0μg/L or 0.5μg/L for a long time, the cancer risk is 10-4 and 10-5 respectively. Bromate is classified as a Class 2B potential carcinogen by the International Agency for Research on Cancer.

2. Genotoxicity: Bromate also has certain genotoxicity and can damage the DNA structure of cells, thereby increasing gene mutations and chromosomal abnormalities.This genotoxicity may cause hereditary diseases or increase the risk of cancer in offspring.

3. Other health effects: In addition to carcinogenicity and genotoxicity, bromate may also have adverse effects on the human endocrine system, nervous system, etc. For example, it may interfere with the synthesis and metabolism of thyroid hormones and affect the normal growth, development and metabolic process of the human body.

refer to

Wu Xiaoyong, Li Xuexue, Li Xiaopeng, Tao Guisong, Hu Mengyao. Study on the formation and control of bromate during ozone treatment of packaged drinking water[J]. China Food and Drug Administration. 2023.06(233):74-79.