Instructions for the preparation of the new "Sanitary Standards for Drinking Water" (main revisions and basis)

GB 5749—XXXX Sanitary Standard for Drinking Water

Preparation of notes

Sanitary Standards for Drinking Water

Revision Drafting Group

May 2021

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1. Major revisions

The current revision of the standard makes a clearer expression of the scope of the standard, updates the normative citation documents, revises and improves or adds or subtracts the terms and definitions such as centralized water supply, small centralized water supply, secondary water supply, factory water, peripheral water, conventional indicators and extended indicators, and edits the text in some articles in the whole text. On this basis, compared with GB 5749-2006, the main contents of the revision are:

1. Adjustment of the number of indicators

The water quality indicators in the body of the standard have been adjusted from 106 items in GB 5749-2006 to 97 items, and the revised text includes 43 general indicators and 54 extended indicators. Four indicators were added, including perchlorate, acetofen, 2-methylisophthalol and tesophyrin, and 13 indicators were deleted, including heat-tolerant coliform, trichloroacetaldehyde, sulfide, cyanide chloride (in CN-term terms), 666 (total), parathion, methyl parathion, lindane, DDT, formaldehyde, 1,1,1-trichloroethane, 1,2-dichlorobenzene and ethylbenzene.

2. Adjustment of indicator classification methods

According to the characteristics of water quality indicators, the classification method of indicators is adjusted from "conventional indicators and non-conventional indicators" of GB 5749-2006 to "conventional indicators and extended indicators", and the classification of indicators after modification is more accurate and avoids the generation of ambiguity. Among them, conventional indicators refer to water quality indicators that reflect the basic status of drinking water quality; extended indicators refer to indicators that reflect the characteristics of regional drinking water quality and the water quality status within a certain period of time or under special circumstances.

3. Adjustment of indicator limits

According to the monitoring significance of WQOs and the latest research results in population health effects or toxicology, combined with the actual situation in China, the limits of 8 indicators were adjusted, including nitrate (in N), turbidity, permanganate index (in O2), free chlorine, boron, vinyl chloride, vinyl chloride, trichloroethylene and Leguo.

4. Adjustment of indicator names

According to the meaning of the WQOs, the names of the two indicators were adjusted, including oxygen consumption (CODMn method, in O2) and ammonia nitrogen (in N).

5. Adjustment of indicator classification

The classification of 11 indicators, including monochlorodibromomethane, dichloro-bromomethane, tribromomethane, tribromomethane, trihalomethane (trichloromethane, monochlorodibromomethane, dichlorodibromomethane, dichlorodibromomethane, tribromomethane), dichloroacetic acid, trichloroacetic acid, ammonia (in N terms), selenium, carbon tetrachloride, volatile phenols (in terms of phenol) and anionic synthetic detergents, were adjusted according to the monitoring significance, detection status and concentration levels of WMI.

6. Added the requirement of deducting 40K before the total β radioactivity index for nuclide analysis and evaluation, and the applicability of microcystin-LR indicators

Potassium is an essential element of the human body, and the total β radioactivity assay includes potassium-40. Based on the consideration that the potassium-40 screening level should be excluded when evaluating the total β radioactivity index comprehensive carcinogenic risk, this revision clarifies that the total β radioactivity is still greater than 1 Bq/L after deducting potassium-40, and nuclear analysis and evaluation should be carried out to determine whether it can be drunk.

Each gram of natural potassium contains 31.2 Bq/g of potassium-40, which can be used to calculate the contribution of potassium-40 to the total β activity concentration.

Based on the consideration that the risk of microcystin-LR exposure is only possible when an algal outbreak occurs, this revision adjusts the expression form of microcystin-LR to microcystin-LR (when an algal outbreak occurs) to make the expression more specific.

7. Delete the interim provisions on WQTs and limits for small centralized and decentralized water supply

Taking into account the current situation of drinking water quality in urban and rural areas in China, this revision deletes the transitional requirements of "partial water quality indicators and limits for small centralized water supply and decentralized water supply" in Table 4 of GB 5749-2006. At the same time, combined with the current situation of small centralized water supply and decentralized water supply in China, the transitional requirements for the total number of colonies, fluoride, nitrate (measured in N) and turbidity are retained due to the limitation of water source and water purification technology.

8. Improve the requirements for the water quality of drinking water sources

In view of the fact that the water quality of drinking water sources in some regions of China cannot meet the requirements of the corresponding national standards for the time being, but limited to the conditions and must be used, this revision improves the water quality requirements for domestic drinking water sources, proposing that when the water quality of the water source cannot meet the corresponding requirements, but "limited to the conditions and restrictions that need to be used, the corresponding purification process should be used for treatment, and the water quality after treatment should meet the requirements of this document".

9. Delete content relating to drinking water management

In view of the fact that it is not appropriate to put forward administrative requirements in technical standards, this revision deletes the relevant requirements and deletes the relevant content of "water quality monitoring" in GB 5749-2006.

10. Adjustment of water quality reference indicators in Appendix A

Appendix A (informative) water quality reference index was adjusted from 28 items in GB 5749-2006 to 55 items. Among them, 29 new indicators were added, including vanadium, 666 (total), parathion, methyl parathion, lindane, DDT, dioptidium, methylthiophalus, oryzacanthrin, fluleling, methyl cream, xicaojing, acetyl methylaminophos, formaldehyde, trichloroacetaldehyde, cyanide chloride (in CN-terms), nitrosanedimethylamine, iodoacetic acid, 1,1,1-trichloroethane, ethylbenzene, 1,2-dichlorobenzene, perfluorooctanoic acid, perfluorooctane sulfonic acid, dimethyl disulfide, dimethyl trisulfide, iodide, sulfide, uranium and radium-226 Deleted 2 indicators, including 2-methylisophthalol and thyroxin; revised the names of 2 indicators, including dibromoethylene and nitrite; adjusted limits for 1 indicator to petroleum (total).

2. Basis for revision of key indicators

1. New indicators

This standard mainly follows the following principles when selecting indicators: (1) there are sufficient research results in population health effects or toxicology; (2) there are existing in China's drinking water, and the concentration level may bring health risks or cause significant impacts on water quality; (3) have feasible and acceptable water treatment technology or source control methods; (4) have mature water quality testing methods. Accordingly, the following four indicators have been added to the body of the standard.

1.1 Perchlorate

Perchlorate is a naturally occurring and manufactured chemical anion that is widely used as a strong oxidant in pyrotechnics, the arms industry and the aerospace industry. China is a traditional fireworks manufacturing and consumption country and a space power, and perchlorate production is distributed throughout the country, and there is a high exposure in drinking water in some areas. The national survey of water projects found that the detection rate of perchlorate in surface water and groundwater in China is very high, of which the Yangtze River Basin is the most polluted, with an average concentration of 16.68 μg/L, and the perchlorate concentration of some monitoring points reaches 105 μg/L.

At present, the research on the effects of perchlorate on human health mainly focuses on the effect on thyroid function. Studies have shown that perchlorate is closely related to thyroid disease in the population, it can interfere with the transport system of iodide in the thyroid gland, inhibit the absorption of iodine by competing with iodine ions for transporters, weaken thyroid function, interfere with the synthesis and secretion of thyroxine, resulting in a decrease in the synthesis of thyroid hormones T3 and T4, thereby affecting the normal metabolism of the human body, hindering the normal growth and development of the human body, and having a particularly serious impact on children, pregnant women, fetuses and newborns during the growth and development period.

The most important exposure route of perchlorate is through the mouth, after the human body absorbs perchlorate, perchlorate ions are mainly distributed in the thyroid gland, and can be excreted through the excretion route after metabolism.

Perchlorate in water can be detected by ion chromatography and liquid chromatography tandem mass spectrometry. These two methods are mature, stable, highly sensitive and have good accuracy.

Based on this, the new perchlorate index is added in this revision, and the limit value is 0.07 mg/L. Mainly based on the human clinical study of perchlorate ingestion by drinking water route in healthy adult volunteers, based on the effect of perchlorate inhibiting the uptake of 50% iodine, the BMDL50 was obtained at 0.11 mg/kg/day, taking into account the difference between species, the uncertainty coefficient was set to 10; due to the lack of relevant data on the contribution rate of drinking water, the drinking water contribution rate took the default value of 20%, and the estimated limit was 0.07 mg/L.

1.2 Acetochlor

Acetochlor is a herbicide widely used in the world, and it is also one of the largest herbicides used in China. With the advantages of wide herbicidal spectrum, outstanding effect, low price and convenient application, it was once an ideal variety to replace carcinogenic alachlor and cyanochosine, and has a history of more than 20 years in China, and its preparation is used in an annual amount of 20,000 to 30,000 tons. According to the national survey data of the water project, the detection rate of acetochlor in China's major water plants is 61%.

Studies have shown that acetochlor has obvious environmental hormonal effects, which can cause protein and DNA damage and lipid peroxidation in animals and humans, and show strong acute toxicity to low vertebrates, plankton and small and medium-sized animals, and pose a greater threat to human health and environmental safety.

Acetochlor can enter the body through the skin, digestive tract and respiratory tract, and is absorbed and metabolized quickly in animals and humans. Experiments have shown that acetochlor entering the body is mainly distributed in the tissue cells of the blood, and there are also some residues in the heart, lungs and liver, which are mainly excreted through urine and feces after metabolism.

Acetochlor in water can be detected by gas chromatography mass spectrometry, which is mature, stable, highly sensitive and accurate. Based on this, the new acetochlor index is added in this revision, and the limit value is 0.02 mg/L. Based on 78 weeks of mouse hepatotoxic sensitization experiments, the LOAEL value was 1.1 mg/kg/d (EU), considering that acetochlor may have carcinogenic effects, the uncertainty coefficient was set to 300; due to the lack of relevant data, the drinking water contribution rate was taken from the default value of 20%, and the limit value was derived to be 0.02 mg/L.

1.3 2-Methylisophthalol and earth odorin

The two indicators of 2-methylisophthalol and earth odorin are the reference indexes for water quality in Appendix A of the data in GB 5749-2006. Current studies have shown that cyanobacteria, actinomycetes and certain fungi are the main sources of water that produce 2-methylisocarboxylanol and earth odorin. When outbreaks of algal contamination occur in water bodies, they can lead to the production of 2-methylisophthalol and earth odorin. These two indicators have a low olfactory threshold, and when the concentration in the water body exceeds the olfactory threshold (10 ng/L), it can lead to an extremely sensitive odor in drinking water, affecting the water senses. Existing survey studies have shown that the concentration of 2-methylisophthalene and soil stink in some water bodies such as lakes and reservoirs in China during the algae breeding season exceeds 10 ng/L.

2-Methylisophthalol and earth odorin in water can be detected by headspace solid phase microextraction-gas chromatography mass spectrometry, which is mature, stable, highly sensitive and accurate. Based on this, the new 2-methylisophthalene and soil odorin indicators are added in this revision, and the index limit is set to 0.00001 mg/L with reference to the olfactory thresholds of the two indicators.

2. Delete the indicator

This standard mainly follows the following principles when deleting indicators, and the deletion of indicators meets at least one of the following conditions: (1) it has not been detected or exceeded in the detection/ monitoring of drinking water in China in recent years; (2) chemical substances that have been banned in China for more than five years; (3) indicators with replaceability. According to this principle, 13 indicators have been deleted from the main body of the standard.

2.1 Heat-resistant coliforms

GB 5749-2006 requires that when the total coliform bacteria are detected in drinking water, heat-resistant coliforms or Escherichia coli need to be detected to determine the source of contamination. Both heat-tolerant coli and Escherichia coli can be used as indicators of whether water bodies are contaminated with feces, but Escherichia coli is more indicative than heat-tolerant coli, and its hygienic significance is greater than that of heat-tolerant coliforms. GB 5749-2006 When it was formulated, because most of the testing institutions did not have the ability to detect Escherichia coli, they adopted a transition method of choosing one of the two indicators of heat-resistant coli and Escherichia coli. According to the survey data on the testing capacity of disease control agencies at all levels in China in 2019, the detection capacity of heat-resistant coliform and Escherichia coli in laboratories at all levels in China has been basically equivalent (84.2% of laboratories with Escherichia coli testing capabilities and 87.7% of laboratories with heat-resistant coli testing capabilities). In view of this, this revision retains the more indicative Escherichia coli and removes the heat-tolerant coliform indicator.

2.2 Trichloroacetaldehyde

Trichloroacetaldehyde is one of the basic raw materials for organic synthesis and is an important intermediate in the production of pesticides and medicines. Trichloroacetaldehyde in drinking water is mainly derived from the disinfection process, mainly due to the use of chlorine preparations to pre-oxidize/disinfect drinking water. In GB 5749-2006, the limit value of trichloroacetaldehyde is 0.01 mg/L.

A 2-year drinking water intake experiment was conducted in mice, and the LOAEL was 13.5 mg/kg/d (WHO) based on the increased health effect of liver pathological changes in mice, the uncertainty coefficient was 3000 (WHO), the drinking water contribution rate was 80% (WHO), and the limit value was 0.1 mg/L was derived.

The results of multi-sectoral water quality monitoring, testing and investigation in China show that although trichloroacetaldehyde has been detected, the concentration level is much lower than the limit value requirement of 0.1 mg/L. In view of this, the trichloroacetaldehyde indicator has been deleted in this revision.

2.3 Cyanogen chloride (in CN-)

Cyanogen chloride is an important chemical intermediate that has certain applications in the synthesis of herbicides, fungicides, dyes and fluorescent brighteners. Cyanogen chloride is easily decomposed in water and converted into cyanide. In GB 5749-2006, the limit value of cyanogen chloride (in CN-terms) is 0.07 mg/L.

China's multi-sectoral water quality monitoring, testing and investigation results show that cyanide chloride is rarely detected, and the concentration level is much lower than the limit requirement of 0.07 mg/L; in addition, cyanogen chloride is easy to decompose in water and converted into cyanide, and the limit requirements for cyanide (0.05 mg/L) have been specified in the standard, which can indirectly control the risk of cyanide chloride. In view of this, the cyanide chloride (in CN-) indicator has been deleted in this revision.

2.4 5 indicators, including 666 (total), parathion, methyl parathion, lindane and DDT

As a broad-spectrum insecticide applied to insect nerves, it has both gastric toxicity, touch killing and re-distillation, and has been widely used in agriculture and non-agriculture, and has been used in seed treatment and soil treatment of various crops, and has also been used for insecticide of crops, ornamental trees, lawns, greenhouse soils and wood products. China has used organochlorine pesticides on a large scale, and 666 is one of the representative ones. In view of its toxicity and harm, China stopped production and banned its use in 1983.

Parathion is a broad-spectrum, non-systematic insecticide and acaricide that acts on gastric contact with the respiratory system. It has been used for pretreatment of soils on leaves before sowing and harvesting, and for controlling a variety of chewing insects, mites and soil insects that grow in orchards and field crops (cereals, fruits, vines, vegetables). In view of its toxicity and harm in the later period, China has made it clear in Announcement No. 274 of the Ministry of Agriculture and Announcement No. 322 of the Ministry of Agriculture that parathion has been banned from all foods since 2007.

Methyl parathion is a potent broad-spectrum insecticide that is mainly used in agricultural cotton crops to kill insects and mites. In view of its toxicity and harm in the later period, China has clearly banned methyl parathion in all foods from 2007 in Announcement No. 274 of the Ministry of Agriculture and Announcement No. 322 of the Ministry of Agriculture. Gb 5749-2006 based on the methyl parathion olfactory threshold, the limit value is 0.02mg/L. This revision adjusts the index limits based on toxicological evidence. Based on the experimental study of health effects such as retinal degeneration in rats, the NOAEL value was 0.25 mg/kg/day, the contribution rate of drinking water was 10% (WHO), and the uncertainty coefficient was 100 (WHO), and the limit value of methyl parathion was 0.009 mg/L.

Lindane and DDT are both organochlorine pesticides. Because of their wide control coverage, better efficacy than other pesticides at the time, and the undiscovered residual toxicity, they were widely used to control insect pests in crops, forests and livestock. In the later stage, in view of its toxicity and harm, and difficult to degrade, it has been banned in China many years ago.

The multi-year drinking water monitoring data show that the concentration of 5 indicators such as 666 (total), parathion, methyl parathion, lindane and DDT in China's drinking water has not exceeded the limit requirement in recent years, and has gradually decreased. In view of this, the revision deletes five indicators, including 666 (total), parathion, methyl parathion, lindane and DDT.

2.5 Formaldehyde, sulfide, 1,1,1-trichloroethane, 1,2-dichlorobenzene and ethylbenzene and other 5 indicators

The main industrial use of formaldehyde is the production of urea formaldehyde, phenol, melamine, pentaerythritol and polyacetal resin, and secondly, it can be used for industrial synthesis of a variety of organic compounds. Formaldehyde in drinking water is mainly produced by natural organic matter in raw water during the use of pre-oxidation or disinfection such as ozone, and can also be filtered out through industrial sewage and polyacetal plastic products into drinking water.

Sulfides and similar compounds include a range of metals and metalloid elements combined with sulfur, selenium, tellurium, arsenic, antimony and bismuth minerals. The natural source of sulfides in water is significantly greater than the source of anthropogenic emissions.

1,1,1-Trichloroethane is a good metal cleaner that is widely used as a cleaning solvent for electronic devices, engines and electronic instruments, and 1,1,1-trichloroethane in drinking water is mainly derived from pollution caused by industrial emissions and container leaks.

1,2-Dichlorobenzene is an isomer of dichlorobenzenes (DCBs). Dichlorobenzene is widely used in industrial and household goods such as deodorants, chemical fuels and pesticides. 1,2-Dichlorobenzene in drinking water is mainly polluted by industrial production and as a solvent and organic synthesis intermediate discharged into the water environment.

Ethylbenzene is mainly used as a solvent in the production of styrene and acetophenone, which is a component of bitumen and naphtha. The content of ethylbenzene in xylene mixtures is as high as 15% to 20%, which is used in the coating industry, insecticidal sprays and gasoline mixtures. Ethylbenzene in the environment is mainly derived from the petroleum industry.

The results of multi-sectoral water quality monitoring, testing and investigation in China show that although five indicators such as formaldehyde, sulfide, 1,1,1-trichloroethane, 1,2-dichlorobenzene and ethylbenzene in drinking water have been detected, the detection rate is low, and in recent years, monitoring has not seen any cases that exceed the limit value requirements. In view of this, the above five indicators have been deleted in this revision.

3. Modify the name indicator

This revision modifies the names of 2 indicators in the body of the standard.

3.1 Permanganate index (in O2)

The expression of the index name oxygen consumption (CODMn method, in O2) in GB 5749-2006 is easily confused with the oxygen consumption (CODCr method). The revision modifies the indicator to a permanganate index (in O2) according to its English name (permanganate index), which is consistent with relevant national and international standards.

3.2 Ammonia (in N)

GB 5749-2006 contains three nitrogen-related indicators, including ammonia nitrogen, nitrate and nitrite. Ammonia nitrogen is not accurate in expression, and this revision changes the name of ammonia nitrogen to ammonia (in N), which maintains the consistency of the expression of the three nitrogen-related indicators.

4. Adjust the limit indicator

Based on the latest research results of water quality indicators in population epidemiology and toxicology and other related disciplines, combined with the actual situation in China, after full demonstration of the index limits, the limits of the 8 indicators in the standard body are adjusted.

4.1 Nitrates (in N)

Nitrate is a general term for nitric acid-derived compounds, common nitrates are: sodium nitrate, potassium nitrate, ammonium nitrate, calcium nitrate, lead nitrate and cerium nitrate. Nitrates are widely found in soils, waters and plants. Surveys have shown that drinking water is one of the main ways in which humans are exposed to nitrates.

Children are sensitive people with nitrate exposure, long-term excessive intake may lead to children with methemoglobinemia (commonly known as blue baby), clinical symptoms of infants with methemoglobinemia are hypoxia, blue-purple skin, severe cases can cause death.

Gb 5749-2006 in the nitrate (in terms of N) index limit is 10 mg/L, groundwater source limit is 20 mg/L. At present, the water treatment process that effectively removes nitrate includes ion exchange, electrodialysis or reverse osmosis, etc., and the method of water source blending can also be used. However, in view of the actual situation of small centralized water supply and decentralized water supply in China at this stage, due to the temporary inability to fully meet the requirements of 10 mg/L when the water source and water purification technology are limited, this revision retains transitional requirements for this part of the water supply, adjusting the nitrate (in N) limit to 10 mg/L, and the small centralized water supply and decentralized water supply are implemented at 20 mg/L due to water source and water purification technology restrictions.

4.2 Turbidity

Turbidity is an optical effect indicator that reflects how much light is obstructed as it passes through the water layer. Turbidity in drinking water is formed by the incomplete filtration of particulate matter in the water source, the presence of inorganic particulate matter in some groundwater, the re-suspension of sediments in the water transmission and distribution system, or the shedding of biofilm. Turbidity is somewhat correlated with microorganisms. Surveys have shown that some gastrointestinal disease outbreaks are associated with increased turbidity in drinking water. In addition, turbidity will also affect the disinfection effect, weaken the killing effect of disinfectants on microorganisms and increase the amount of chlorine required.

Gb 5749-2006 in the turbidity index limit of 1 NTU, water source and water purification technology limit is 3 NTU. Although turbidity itself does not necessarily pose a threat to health, it is an important indicator of contaminants that may have an impact on health. At the same time, turbidity is also an important control parameter in the process of drinking water purification, which can indicate the water treatment process, especially the quality problems in various treatment processes such as flocculation, precipitation, filtration and disinfection. The WHO states that in order to ensure the disinfection effect, it is best to control the turbidity below 1 NTU. However, in view of the actual situation of small centralized water supply and decentralized water supply in China at this stage, due to the temporary inability to fully meet the requirements of 1 NTU when the water source and water purification technology are limited, this revision retains the transitional requirements for this part of the water supply, adjusts the turbidity limit to 1 NTU, and the turbidity of the small centralized water supply and decentralized water supply is implemented according to 3 NTU due to the limitation of water source and water purification technology.

4.3 Permanganate index (in terms of O2)

Permanganate index refers to the amount of potassium permanganate consumed by oxidizing reducing substances in water under certain conditions with potassium permanganate as an oxidant, and the result is converted into oxygen expression (O2, mg/L). The permanganate index can indirectly reflect the degree of organic pollution of water bodies and is a comprehensive indicator for evaluating the pollution of water bodies by organic matter.

The limit of permanganate index in GB 5749-2006 is 3 mg/L, and the limit for raw water >6 mg/L is 5 mg/L. In view of the fact that the permanganate index has important indicative significance in reflecting the pollution of organic matter in water, and the existing water quality status and water treatment process in China have been greatly improved, the deep treatment process such as ozone bioactive carbon has a good effect on reducing this index. Therefore, this revision adjusts the permanganate index limit to 3 mg/L, and cancels the original provision that it can be relaxed to 5 mg/L when the raw water > 6 mg/L.

4.4 Free chlorine

Adding disinfectants to water and maintaining an appropriate disinfectant allowance is an important part of ensuring the safety of drinking water supply, free chlorine is chlorine in the form of hypochlorous acid, hypochlorite ions, or chlorine elements dissolved in water.

GB 5749-2006 The limit of free chlorine factory water is 4 mg/L. Existing studies have shown that free chlorine at concentration levels of 5 mg/L and below will not have harmful effects on the human body; however, in view of the fact that chlorine disinfection will produce a large number of disinfection by-products, and some disinfection by-products have harmful health effects, the production of disinfection by-products should be minimized on the basis of controlling the disinfection effect, and avoiding excessive dosing of disinfectants is one of the effective ways to control disinfection by-products. In view of this, this revision adjusts the upper limit of free chlorine allowance in factory water from 4 mg/L to 2 mg/L.

4.5 Boron

Boron is usually present in the form of a compound that binds boron to oxygen. The world is rich in boron resources, and China's boron ore resources are large. Most of the boron on Earth occurs in the oceans, and the amount of boron in fresh water depends on a variety of factors, such as the geochemical environment of the watershed, coastal areas close to the ocean, industrial and municipal sewage discharge, etc. Boron can be absorbed by the orally and inhalation pathways, the intact skin pathway absorbs little or no absorption, and the broken skin has a small amount of absorption of boron. After oral exposure, boron can be rapidly absorbed by the gastrointestinal tract, and more than 90% of the dose can be excreted in a short period of time. The limit value of boron in GB 5749-2006 is 0.5 mg/L. Since the promulgation of GB 5749-2006 "Sanitary Standards for Drinking Water", the toxicological research conclusions of boron have not changed significantly. This revision is still based on the results of the study of developmental toxicity in rats, the selection of BMDL10 (10.3 mg/kg/d) for the derivation process of the limit value, the drinking water contribution rate is taken 20% (USEPA), the uncertainty coefficient considering intraspecific and interspecific differences is taken 60 (WHO), and the limit value of boron is derived to be 1.0 mg/L.

4.6 Vinyl chloride

Vinyl chloride is mainly used in the production of polyvinyl chloride. Vinyl chloride and PVC are used as raw materials for the plastics, rubber, paper, glass and automotive industries. The migration of vinyl chloride monomers in polyvinyl chloride is a possible source of vinyl chloride in drinking water. Inhalation is the most important route for ingestion of vinyl chloride, and drinking water makes an important contribution to the intake of vinyl chloride when PVC pipes with high residue vinyl chloride monomers are used in the distribution network.

Vinyl chloride is rapidly absorbed after inhalation or oral exposure, and after absorption, it can be rapidly and widely distributed in some tissues, such as brain, liver, spleen, kidneys, fatty tissue and muscle, with the highest content in the liver, followed by the kidneys. When vinyl chloride is ingested at low concentrations, excretion is the most important route of clearance, with only a very small amount excreted from the air in prototype, but once metabolic saturation is reached, it is mainly exhaled in prototype form and cannot be eliminated by other means.

Vinyl chloride is an anesthetic, in addition to vinyl chloride in the human body has mutagenic and fissile properties, also has a certain impact on reproduction and development, there is other evidence that vinyl chloride is carcinogenic to animals

The limit value of vinyl chloride in GB 5749-2006 is 0.005 mg/L. This revision adjusts the index limits based on new toxicological evidence. In studies of the carcinogenicity of vinyl chloride exposure, a pharmacokinetic model determines the dose administered (the result is that 10% of the animals in the rat biological test develop tumors, including oral contact and zero-contact doses), the linear extrapolation method is applied to plot curves between different doses, the corresponding value is derived based on the acceptable carcinogenic risk of 10-5, and the risk level of exposure from birth is twice the above value, and the limit value of vinyl chloride is derived to be about 0.0003 mg/L. However, due to the quantitative detection limit of the vinyl chloride purging-gas test method, it can only reach 0.0006 mg/L. In view of the limitations of the sensitivity of the detection method, the limit value of vinyl chloride is set at 0.001 mg/L in this revision.

4.7 Trichloroethylene

Trichloroethylene is mainly used in metal degreasing processes and is also used as a solvent for greases, fats and tars, paint removers, coatings and vinyl resins, as well as to wash cotton, wool and other fabrics through the textile processing industry. When trichloroethylene is used in the metal degreasing process, it is mainly discharged into the atmosphere, but it can also enter the environmental water body in the form of industrial wastewater. Improper sewage treatment and improper disposal of trichloroethylene in landfills are the main causes of groundwater pollution. Trichloroethylene can be ingested through the oral route, and because of its volatile and fat-soluble nature, inhalation exposure and skin exposure can also occur, such as through bathing and showering.

Trichloroethylene is easily absorbed after oral and inhalation exposure. After being absorbed, trichloroethylene diffuses through the biofilm and is widely distributed in tissues and organs through the circulatory system.

The limit value of trichloroethylene in GB 5749-2006 is 0.07 mg/L. This revision adjusts the index limits based on new toxicological evidence. In the study of the effect of trichloroethylene exposure on developmental/reproductive function, based on the developmental toxicity study of rats, BMDL10 was 0.146 mg/kg/day; the contribution rate of drinking water was 50% (WHO); the uncertainty coefficient considered the differences within and between species, 100 was taken, and the limit value of trichloroethylene was 0.02 mg/L was derived.

4.8 Lego

Leguo is an effective insecticide that can be used in most crops such as fruits and vegetables to kill insects and mites, in addition to the control of indoor flies. As a water-soluble pesticide, after entering the water environment, Leguo will not be strongly adsorbed by the soil but exists in a large number of water bodies, and may also bring phosphorus pollution to the water body and cause eutrophication of the water body.

Leguo can enter the body through oral, inhalation and skin contact, mainly distributed in the blood, and also has some content in the liver and kidneys. After completing the metabolism in the body, it is excreted mainly through urine. Leguo has a certain reproductive developmental toxicity.

Gb 5749-2006 based on the Lego Olfactory threshold, which has a limit of 0.08 mg/L. This revision adjusts the index limits based on toxicological evidence. In the study of the effect of Leguo exposure on developmental/reproductive function, based on experimental studies of reproductive behavior injury in rats, the NOAEL value was 1.2 mg/kg/d, the drinking water contribution rate was 10% (WHO), and the uncertainty coefficient was 500 (WHO), and the limit value of Leguo was 0.006 mg/L.

5. Adjust the classification indicators

According to the distribution characteristics of water quality indicators in drinking water and the detection of water quality monitoring, testing and investigation in many departments in China for many years, the classification of 11 indicators has been adjusted in this revision.

5.1 Six indicators, including monochlorodibromomethane, dichlorodibromomethane, tribromomethane, dichloroacetic acid, trichloroacetic acid and trihalomethane

Six indicators, including monochlorodibromomethane, dichloro-bromomethane, tribromomethane, dichloroacetic acid, trichloroacetic acid and trihalomethane, are unconventional indicators in GB 5749-2006. This revision adjusts the above six indicators to regular indicators. At present, China's chlorinated disinfection of drinking water treatment process is widely used, monochlorodibromomethane, dichloro-bromomethane, tribromomethane, dichloroacetic acid and trichloroacetic acid these 5 substances generally do not appear in the raw water, the main source of these substances in drinking water is the disinfectant in the disinfection process and the organic matter in the water body reacts to form a by-product. Trihalomethane mainly includes trichloromethane, monochlorodibromomethane, dichloro-bromomethane and tribromomethane, the limit is that the sum of the ratio of the measured concentrations of these four compounds to their respective limits does not exceed 1, and the setting of this indicator further tightens the control of disinfection by-product indicators. Health risks associated with long-term exposure to these substances include carcinogenicity, genotoxicity, reproductive toxicity and developmental toxicity.

The results of water quality monitoring, testing and investigation in China's multi-sectoral water quality show that six indicators such as monochlorodibromomethane, dichloro-bromomethane, tribromomethane, dichloroacetic acid, trichloroacetic acid and trihalomethane are relatively common in drinking water, with a detection rate of more than 60%, and monochlorodibromomethane and dichloro-bromomethane are as high as more than 90%. In view of the fact that chlorination disinfection is still widely used in China, and the detection rate of these substances in China's drinking water is high, and has a strong health effect, the revision adjusts 6 indicators such as monochlorodibromomethane, dichloro-bromomethane, tribromomethane, dichloroacetic acid, trichloroacetic acid and trihalomethane to routine indicators.

5.2 Ammonia (in N)

Ammonia in water is one of the indicator factors affecting the organoleptic traits of water bodies. The concentration of ammonia is closely related to the content of organic matter and the size of dissolved oxygen, marking the degree of water pollution.

GB 5749-2006 Ammonia nitrogen is an unconventional index. China's multi-sectoral water quality monitoring, testing and survey results show that the surface water as the source of drinking water is common, in some of the groundwater as the source of drinking water has also been detected, the maximum value can reach 10 mg / L; at the same time, in view of its ability to reflect the degree of water pollution by domestic sewage, and its concentration has an important impact on the water purification process, especially the control of disinfectants. Therefore, this revision adjusts ammonia (in N) as a regular indicator.

5.3 Selenium, carbon tetrachloride, volatile phenols (in terms of phenol) and anionic synthetic detergents and other 4 indicators

Selenium is one of the rare non-metals, but also a necessary trace element of the human body, most foods contain different concentrations of selenium. Selenium is widely used in many fields such as metallurgy, glass, ceramics, electronics, solar energy and feed, and industrial metallurgy is its main pollution route. Studies have shown that the general population can consume selenium through drinking water and food, especially cereals and fish. Except in some selenium-rich areas, most drinking water contains less than 10 μg/L of selenium.

Carbon tetrachloride has been widely used as a solvent, extinguishing agent, organic chloride agent, fragrance leaching agent, fiber degreasing agent, grain cooking agent, drug extractant, organic solvent and fabric dry cleaning agent, etc., but due to its toxicity and the destruction of the ozone layer relationship is now rarely used and limited production, many uses have been replaced by dichloromethane, etc., carbon tetrachloride is mainly discharged into the atmosphere, may also be discharged into the water body through industrial wastewater.

Natural water generally does not contain phenolic compounds, and its pollution sources mainly come from industrial wastewater discharged by coking, gas manufacturing, petroleum refining, wood corrosion protection, petrochemical and pharmaceutical industries.

Anionic synthetic detergent can be generated by the sulfonation reaction of linear alkylbenzene and a variety of sulfonated agents, which has a significant decontamination effect on granular dirt, protein dirt and oily dirt, and the washing effect on granular dirt on natural fibers is particularly good, and the decontamination force is enhanced with the increase of washing temperature, and the effect on protein dirt is higher than that of nonionic surfactants. Water bodies can be accessed through the discharge of industrial wastewater and domestic sewage.

GB 5749-2006 Selenium, carbon tetrachloride, volatile phenols (in terms of phenol) and anionic synthetic detergents are all conventional indicators. The results of multi-sectoral water quality monitoring, testing and survey in China show that the rate of exceeding the standard of these four indicators in drinking water is low, and it is only local punctate pollution or regional pollution. In view of this, this revision adjusts four indicators, such as selenium, carbon tetrachloride, volatile phenols (in terms of phenol) and anionic synthetic detergents, to expand the indicators.

6. Maintain limit indicators

Combined with the latest epidemiology and toxicology and other related research progress, this revision demonstrates all the indicators in the standard body one by one, of which the limits of 85 indicators remain unchanged in the middle limit of GB 5749-2006.

The 85 indicators included 39 conventional indicators, specifically total coliform, Escherichia coli, total colonies, arsenic, cadmium, chromium, lead, mercury, cyanide, fluoride, trichloromethane, monochlorodibromomethane, dichloromethane, tribromomethane, trihalomethane, dichloroacetic acid, trichloroacetic acid, bromate, chlorite, chlorate, color, odor and taste, gross eye visible, pH, aluminum, iron, manganese, copper, zinc, chloride, sulfate, dissolved total solids, total hardness (in CaCO3), ammonia (in N). Total α radioactivity, total β radioactivity, total chlorine, ozone and chlorine dioxide.

Among the 85 indicators, there were 46 extended indicators, specifically Giardia, Cryptosporidium, Antimony, Barium, Beryllium, Molybdenum, Nickel, Silver, Thallium, Selenium, Dichloromethane, 1,2-Dichloroethane, Carbon Tetrachloride, 1,1-Dichloroethylene, 1,2-Dichloroethylene, Tetrachloroethylene, Hexachlorobutadiene, Benzene, Toluene, Xylene (Total), Styrene, Chlorbenzene, 1,4-Dichlorobenzene, Trichlorobenzene (Total), Hexachlorobenzene, Heptachlor, Malathion, Herbicone, Cecitracine, Furandan, Chlorpyrifos, Chlorpyrifos, Dichlorvos, Astradecin, cypermethrin, 2,4-drops, pentachlorophenol, 2,4,6-trichlorophenol, benzo(a)pyrene, bis(2-ethylhexyl) phthalate, acrylamide, epichlorohydrin, microcystin-LR (when algal outbreaks occur), sodium, volatile phenols (in terms of phenol) and anionic synthetic detergents.

7. Water quality reference index

This revision makes the following adjustments to the informative Annex A water quality reference index:

7.1 New metrics

This revision adds 29 new indicators to the informative Appendix A.

7.1.1 Vanadium

Vanadium is a solid metal and is an important carbide stabilizer for the manufacture of steel. Vanadium in water bodies is mainly of natural origin, and a small part comes from anthropogenic emissions. China is the world's largest producer of vanadium, but also the world's fastest growth of vanadium products, the largest consumption of countries, vanadium pollution in China is becoming an important environmental problem.

Vanadium is mainly absorbed into the body through the respiratory tract and less likely through the gastrointestinal tract. When exposure to vanadium through the mouth, the absorbed dose is mainly distributed in the bones, most of which is excreted through feces and a small part is excreted through urine. Studies have shown that consuming high concentrations of vanadium can be harmful to human health, especially in sensitive people.

In view of the current information on the health effects of vanadium and the source of pollution, combined with the actual situation in China, vanadium has been added as a reference index for water quality in this revision. Based on the results of the study of populations with exposure during pregnancy and adverse birth outcomes in infants and young children, using the 95% quantile urine vanadium exposure level, the daily tolerable intake of vanadium by drinking water was 0.0096 μg/kg/day, and the daily water intake of pregnant women was 21 mL/kg/day (USEPA), with a 5% oral absorption rate and a derived limit of 0.01 mg/L.

7.1.2 Enemy Worms

Dichlorum is a broad-spectrum insecticide that is mainly used to control pests in fields and fruit crops, but also to control forest insects. Studies have shown that the health effects of acute exposure to dimethodiae are manifested as exhaustion, headache, weakness, confusion, vomiting, abdominal pain, excessive sweating, and salivation, occasional muscle cramps, unconsciousness and convulsions, and may lead to death due to respiratory failure. Some countries have banned the use of enemy insects, and China has not yet implemented the prohibition measures, but still uses them as an alternative pesticide for the control of underground pests and the control of sugarcane borers and cane turtles. There are three main ways for the insects to enter the water environment: one is to escape into the air during the production process and enter the water body; the second is the discharge pollution of production and processing wastewater; the third is that after its application to farmland, it may pollute the groundwater by infiltration into the soil, and may also enter the river with rainwater.

In view of the current information on the health effects and pollution sources of the enemy insects, combined with the actual situation in China, the new enemy insects are added as water quality reference indicators in this revision. Referring to the limit requirements of GB 3838-2002 "Surface Water Environmental Quality Standards", the limit value of the enemy insect is set at 0.05 mg/L.

7.1.3 Methylthiopramine

Methylthiopramine is a highly effective and low-toxic fungicide that has preventive and curative effects on a variety of plant diseases. Methylthiopyridine is used in a large amount in China, and there are three main ways for methylthiophenidam to enter the water environment: one is to escape into the air during the production process and enter the water body; the second is the discharge pollution of production and processing wastewater; the third is that after its application to farmland, it may pollute the groundwater by infiltration into the soil, and it may also enter the river with rainwater. Studies have shown that methylthiopramine has low acute toxicity, and it has been found in animal experiments to act on the liver and thyroid gland, and has been classified as a suspected carcinogen.

In view of the current information on the health effects and pollution sources of methylthiophane, combined with the actual situation in China, this revision adds methylthiopyridine as a reference index for water quality. Referring to the limit value of methylthiopyridine in the management index of The Japanese Drinking Water Quality Standard, the limit value of methylthiophalus was set at 0.3 mg/L.

7.1.4 Rice blast spirit

Rice blast is a highly efficient, low-toxicity and low-residue organic sulfur fungicide, which has a special effect on rice neck blast, and also has a certain prevention and control effect on rice leaf blast, rice seedling blast and coccimal sclerotia. Large-area use can also treat rice planthoppers. There are three main ways for rice plague spirit to enter the water environment: one is to escape into the air during the production process and enter the water body; the second is the discharge pollution of production and processing wastewater; the third is that after its application to farmland, it may pollute the groundwater by infiltration into the soil, and may also enter the river with rainwater. Long-term exposure to rice blast has the potential to pose a threat to human health.

In view of the current information on the health effects and pollution sources of rice blast, combined with the actual situation in China, this revision adds rice blast as a reference index for water quality. With reference to the limits of rice blast in the management indicators of The Japanese Drinking Water Quality Standard, the limit value of Rice Blaster was set at 0.3 mg/L.

7.1.5 Fluroleline

Fluleline is a herbicide, because it can also play a better weeding effect under drought conditions, so it is more suitable for use in the northern region in the spring soil drought. The use of fluleline in China is larger, and there are three main ways for fluleling to enter the water environment: one is to escape into the air and enter the water body during the production process; the second is the discharge pollution of production and processing wastewater; the third is that after its application to farmland, it may pollute groundwater by infiltration into the soil, and may also enter the river with rainwater. Long-term exposure to fluroleline has the potential to pose a threat to human health.

In view of the current health effects and pollution sources of fluroleline and other information, combined with the actual situation in China, this revision adds fluleline as a reference index for water quality. Based on the mild liver effect in the 1-year dog feeding study, the NOAEL value was 0.75 mg/kg/day, the drinking water contribution rate was 10% (WHO), the uncertainty coefficient was 100 (WHO), and the limit value was 0.02 mg/L was derived.

7.1.6 Methylstilling

Methammer is a new, efficient and low-toxic fungicide, its internal absorption and penetration is very strong, 30 minutes after application can be conducted up and down the plant in both directions, the disease plant has a protective and therapeutic effect, and the medicinal effect lasts for a long time, and the downy mildew, Phytophthalmosis and rot bacteria caused by a variety of crop downy mildew, melon fruit and vegetable Phytophthora and millet white disease is effective. Methammer can enter the human body through three routes: skin, digestive tract and respiratory tract. The results of the special water survey show that there is methylhydrin detected in the water body of China, but the concentration is low.

In view of the current information such as the health effect and pollution source of methanol, combined with the actual situation in China, this revision adds chlorpyrine as a reference index for water quality. With reference to the limit value of methylhydrin in the management index of the Japanese drinking water quality standard, the limit value of methylhydrin is set at 0.05 mg/L.

7.1.7 Nishikusa net

Xicaojing, also known as Xishanjing, is a triazine herbicide, mainly used in rice, but also can be used in crops such as corn, soybeans, wheat, peanuts and cotton. Triazine herbicides are widely used in China, and there are three main ways for triazine herbicides to enter the water environment: one is to escape into the air during the production process and enter the water body; the second is the discharge pollution of production and processing wastewater; the third is that after its application to farmland, it may pollute the groundwater by infiltration into the soil, and may also enter the river with rainwater. Triazine herbicides themselves are environmental hormones that mainly affect the endocrine system of organisms.

In view of the current health effects, pollution sources and other information of Xicao net, combined with the actual situation in China, this revision has added Xicao net as a reference index for water quality. With reference to the net limit of Western grass in the management index of the Japanese drinking water quality standard, the net limit of Western grass is set at 0.03 mg/L.

7.1.8 Acetamolphos

Acetamolphos is a broad-spectrum, high-efficiency, low-toxicity and low-residue organophosphorus insecticide, with gastric toxicity, touch killing and systemic effect, has a certain fumigation effect, suitable for vegetables, rice, cotton, wheat, fruit trees, rapeseed and tobacco, etc., can be used to control various types of vegetable pests. There are three main ways for acetamol to enter the water environment: one is to escape into the air during the production process and enter the water body; the other is the discharge pollution of production and processing wastewater; the third is that it may pollute the groundwater by infiltration into the soil after its application to farmland, and may also enter the river with rainwater. Acetamus phosphorus pesticides are less toxic, but they are used in large amounts and are widely distributed, and may pose health risks.

In view of the current information on the health effects and pollution sources of acetamol, combined with the actual situation in China, this revision adds acetamol phosphorus as a reference index for water quality. With reference to the limit value of acetamolphos in the management index of the Japanese drinking water quality standard, the limit value of acetamol phosphorus is set at 0.08 mg/L.

7.1.9 Nitrosodimethylamine

Nitrosodimethylamine (NDMA) is an industrial by-product of the reaction of nitrate or nitrite with amines under certain pH conditions, which is discharged in rubber manufacturing, leather leather, pesticide manufacturing, food processing, casting and dye manufacturing enterprises and sewage treatment plants. In addition, drinking water also forms NDMA during water treatment. In water bodies containing nitrogenous organic compounds, if the water plant is disinfected with chloramine, NDMA is generated as a disinfection by-product. There is evidence that ingestion of NDMA by drinking water in animals induces cancer, as well as evidence that NDMA is genotoxic in vivo and in vitro.

In view of the current information such as the health effect and pollution source of NDMA, combined with the actual situation in China, this revision adds nitrosodimethylamine as a reference index for water quality. Based on the most sensitive health effect endpoint induced by NDMA, hepatic biliary cystic adenoma (female rats), the lower 95% confidence limit for TD05 (which can lead to a tumor incidence 5% higher than the background value) is 18 μg/kg/day, the unit risk is derived to be 2.77×10-3 μg/kg/day, and the limit is 0.0001 mg/L (corresponding to the lifetime carcinogenic risk of 10-5).

7.1.10 Iodoacetic acid

Iodoacetic acid can be used as a preservative or stabilizer for alcoholic beverages, and can also be used as an analytical reagent, dye, inhibitor of organic synthesis and enzymes, etc., for agricultural plant resources research and organic synthesis. Medically, iodoacetic acid is used as an inducer for animal models of arthritis, inducing arthritis in animals by injecting iodoacetic acid into the joints. When raw water contains iodine ions, iodine acetic acid can be generated by chloramine disinfection under appropriate conditions. Animal experiments have shown that iodoacetic acid has tumorigenic and endocrine interference activities, and is extremely genotoxic. The survey results show that there are high exposure hazards in China's coastal salty tide and inland high iodine areas.

In view of the current information on the health effects and pollution sources of iodoacetic acid, combined with the actual situation in China, this revision adds iodoacetic acid as a reference index for water quality. According to the LOAEL value of iodoacetic acid in the subacute toxicity test was 6.0 mg/kg/day, the uncertainty coefficient was taken 1000 (intraspecific 10, interspecific 10 and carcinogenicity 10), the drinking water contribution rate was 50% (refer to the children's drinking contribution rate in other studies), and the sensitive population of children was taken 5 kg of body weight and 0.75 L/day of drinking water intake, and the derived limit was 0.02 mg/L.

7.1.11 Perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) is a perfluorinated compound, a new type of persistent organic compound with strong stability and waterproof and oilproof properties, which has been widely used in paper, packaging materials and fire protection industries since the 1950s. In recent years, perfluorinated compounds have received global attention for their detection in various environmental media such as sediments, surface water and air, in organisms and even in the blood of people. PFOA was proposed by the European Union for inclusion in the Stockholm Convention in 2019 due to its persistence, bioaccumulation, long-range environmental transport properties and toxic effects on mammals, including humans. PFOAC has been detected in drinking water in many places in China.

In view of the current information on the health effects and pollution sources of PFOA, combined with the actual situation in China, this revision adds PFOA as a reference index for water quality. According to animal experiments to offspring weight loss as the health effect endpoint to obtain a reference dose of 20 ng / kg / d (USEPA), drinking water contribution rate of 23% (water special), there is no data on the ratio of water intake to weight of pregnant women of maternal age in China, with reference to the use of 90% percentile of the ratio of water intake to body weight of pregnant women of American maternal age (USEPA, DI / BW = 0.054 L / kg / d), the estimated limit is 0.00008 mg / L.

7.1.12 PFOS

Perfluorooctane sulfonic acid (PFOS) is a perfluorinated compound, a new type of persistent organic compound with strong stability and waterproof and oilproof properties, which has been widely used in paper, packaging materials and fire protection industries since the 1950s. In recent years, perfluorinated compounds, especially PFOS, have received global attention due to their detection in various environmental media such as sediments, surface water and air, and in organisms and even in the blood of people. PFOS was proposed for inclusion in the Stockholm Convention by the European Union in 2009 due to its persistence, bioaccumulation, long-range environmental transport properties and toxic effects on mammals, including humans. In the past few years, the dosage of PFOS in some parts of China is large. PFOS has been detected in drinking water in many places in China.

In view of the current information on the health effects and pollution sources of PFOS, combined with the actual situation in China, PFOS is added as a reference index for water quality in this revision. According to animal experiments to offspring weight loss as the health effect endpoint to obtain a reference dose of 20ng / kg / d (USEPA), drinking water contribution rate of 12.7% (water special), there is no data on the ratio of water to weight of pregnant women of maternal age in China, with reference to the use of 90% percentile of the ratio of water intake to body weight of pregnant women of American maternal age (USEPA, DI / BW = 0.054L / kg / d), the estimated limit is 0.00004 mg / L.

7.1.13 Dimethyl disulfide

Dimethyl disulfide is widely used as a pre-vulcanizer for catalysts for petroleum hydrodesulfurization, as well as a solvent in the industrial sector, and as a raw material for the production of the insecticide "hypothion". At the same time, dimethyl disulfide can be used as a calibrator to calibrate the odor. Sulfur ethers in water bodies are generally derived from sulfur-containing amino acids, surfactants and other sulfur-containing compounds in algae, domestic sewage and industrial wastewater in natural water bodies. The effect of dimethyl disulfide on drinking water is mainly manifested in the effect of water organs and brings odor.

In view of the fact that dimethyl disulfide has been detected in environmental water bodies and drinking water in many places in China, the new dimethyl disulfide is added as a reference index for water quality in this revision. Based on its olfactory threshold, the dimethyl disulfide limit is set to 0.00003 mg/L.

7.1.14 Dimethyl trisulfide

Dimethyl trisulfide is widely used in the industrial sector. Sulfur ethers in water bodies are generally derived from sulfur-containing amino acids, surfactants and other sulfur-containing compounds in algae, domestic sewage and industrial wastewater in natural water bodies. The effect of dimethyl trisulfide on drinking water is mainly manifested in the effect of water organs and brings odor.

In view of the fact that dimethyl trisulfide has been detected in environmental water bodies and drinking water in many places in China, this revision adds dimethyl trisulfide as a reference index for water quality. Based on its olfactory threshold, the dimethyl trisulfide limit is set to 0.00003 mg/L.

7.1.15 Iodides

Iodine is one of the basic raw materials of inorganics, which is widely used in the fields of medicine and hygiene, chemical analysis, test strips, photography and artificial rainfall. In the field of medicine and health, it can be used for disinfectants, disease-specific therapeutic drugs and contrast agents, etc., and iodine is also widely used in the field of chemical synthesis. Iodine is an essential trace element of the human body, an indispensable and important raw material for the synthesis of thyroid hormones, and plays an important role in maintaining the health of the body. Insufficient iodine intake can cause iodine deficiency diseases, including endemic goiter, endemic cretin disease and endemic subclinical cretin disease, iodine deficiency can also lead to miscarriage, preterm birth, stillbirth and congenital malformations, etc.; iodine excess will also produce health hazards, inhibit the synthesis and release of thyroid hormones, produce iodine blocking effects, and adversely affect the health and pregnancy outcomes of pregnant women. Years of monitoring data show that there is a certain degree of waterborne hyperiodine hazards in China, and there are also a considerable number of waterborne hyperiodine areas and disease areas.

In view of the current information on the health effects of iodide and the source of pollution, combined with the actual situation in China, the new iodide is added as a reference index for water quality in this revision. According to GB/T 19380-2016 "Delineation of Waterborne Hyperiodine Areas and Hyperiodiod disease Areas", the determination of water-sourced hyperiodine areas and hyperiodiodiod disease areas in China is based on villages, and the median water iodine > 100 μg/L is judged as a high iodine area. For this reason, the iodide limit is set to 0.1 mg/L.

7.1.16 Uranium

Uranium is an important natural radioactive element that is widely present in the earth's crust and aquatic environment. Sources of uranium in drinking water mainly include: leaching from natural deposits, release in tailings, nuclear industry emissions, coal combustion and other fuels, and the use of phosphate fertilizers containing uranium. Studies have shown that the damage effect of uranium mainly includes chemical damage and radiation damage: the intake of +6 valent natural uranium compounds is mainly manifested as chemical damage to the kidneys; inhalation of +4-valent uranium compounds and deposition in the lungs can cause radiation effects. The active concentration of natural radionuclides in drinking water is usually low. To date, the concentration of uranium that has no effect on humans has been explicitly proposed in the study. Overall, there is no clear evidence of an effect on human exposure to concentrations below 30 μg/L.

In view of the current information on the health effects and pollution sources of uranium, combined with the actual situation in China, this revision adds uranium as a reference index for water quality. New epidemiological studies based on uranium exposure in the population, taking into account cancer risk and economic and technical feasibility, set a limit of 0.03 mg/L.

7.1.17 Radium-226

Radium-226 is a natural radionuclide formed by the decay of the original radionuclide U-238 with a half-life of 1622 years. Radium is a silvery-white metal, the most reactive alkaline earth metal, with a very strong radioactivity, radium ions are colorless, not hydrolyzed in solution, so soluble radium into the human body exists in a divalent state. Radium is higher in environmental water bodies and biological samples in uranium and thorium mining areas. Studies have shown that radium radiation is associated with an increased incidence of two cancer types with low spontaneous rates, osteosarcoma and head sarcoma; in addition, it has mutagenic and teratogenic effects.

In view of the current information on the health effects and pollution sources of radium-226, combined with the actual situation in China, radium-226 is added as a reference index for water quality in this revision. The limit value is set to 1 Bq/L with reference to the WHO limit value.

7.1.18 12 indicators including 666 (total), parathion, methyl parathion, lindane, DDT, formaldehyde, trichloroacetaldehyde, cyanogen chloride (in CN-terms), 1,1,1-trichloroethane, ethylbenzene, 1,2-dichlorobenzene and sulfide

The above 12 indicators are conventional/unconventional indicators of water quality in GB 5749-2006. The results of water quality monitoring, testing and investigation in China for many years show that the above 12 indicators have not exceeded the standard or even detected in drinking water in recent years, of which 666 (total), parathion, methyl parathion, lindane and DDT and other pesticides have been banned in China for more than five years.

In view of this, this revision deletes 12 indicators such as 666 (total), parathion, methyl parathion, lindane, DDT, formaldehyde, trichloroacetaldehyde, cyanogen chloride (in CN-terms), 1,1,1-trichloroethane, ethylbenzene, 1,2-dichlorobenzene and sulfide from the standard body, and adds them to Appendix A as a reference index for water quality in combination with the latest toxicological effect research results.

7.2 Deleting Metrics

In this revision, two indicators have been deleted from the informative Appendix A, namely 2-methylisophthalol and earth odorin.

When water algae pollution occurs, it will produce odors and affect the senses of water bodies. Current studies have shown that cyanobacteria, actinomycetes and certain fungi are the main sources of water that produce 2-methylisocarboxylanol and earth odorin. In view of the frequent occurrence of algal pollution in some parts of China, this revision deletes the two indicators of 2-methylisophthalol and soil odorin from Appendix A and adds them to the standard body as an extended indicator.

7.3 Modify the name indicator

This revision changes the names of two indicators in The Informative Appendix A.

7.3.1 1,2-Dibromoethane

Gb 5749-2006 in the indicator dibromoethylene is not accurate in expression, this revision will be the indicator name is clearly 1,2-dibromoethane.

7.3.2 Nitrites (in N)

Gb 5749-2006 the indicator nitrite is inaccurate in expression, and this revision clarifies the name of nitrite as nitrite (measured in N), which is consistent with the expression of ammonia (measured in N) and nitrate (measured in N).

7.4 Adjust the limit indicator

In this revision, the limit value of one indicator is adjusted in the informational appendix A for petroleum (total).

Petroleum is a complex liquid hydrocarbon that occurs naturally, a complex combination of hydrocarbons, which may also contain small amounts of nitrogen, oxygen and sulfur compounds, which produce combustible fuels, petrochemicals and lubricants after distillation. As an important industrial product, improper treatment or disposal of petroleum can cause pollution of surface water and groundwater, resulting in increased concentrations of many low molecular weight hydrocarbon compounds, and the olfactory threshold of these compounds is usually low, resulting in unpleasant "diesel-like" odors in the water. In addition, petroleum contains benzene, toluene, n-hexane and polycyclic aromatic hydrocarbons, which have adverse health effects on the human body, including acute poisoning, carcinogenicity, mutagenicity and reproductive development effects.

GB 5749-2006 Appendix A specifies that the limit value of petroleum (total) is 0.3 mg/L. This revision refers to the limit requirements (≤0.05 mg/L) of GB 3838-2002 "Surface Water Environmental Quality Standards" for water bodies in Class III and above (≤0.05 mg/L), GB 11607-1989 "Fishery Water Quality Standards" and GB 3097-1997 "Marine Water Quality Standards" (≤0.05 mg/L), and further tightens the limit requirements for petroleum in drinking water, and unifies them as 0.05 mg/L.

7.5 Maintain limit indicators

This revision combines the latest epidemiological and toxicological and other related research advances, and demonstrates all the indicators in the informative Appendix A one by one. Appendix A maintained the limit values for 25 indicators, including Enterococcus, Clostridium aerouss, Ethylmercury chloride, Tetraethyl lead, 1,2-dibromoethane, Pentachloropropane, nitrobenzene, bisphenol A, acrylonitrile, acrylic, glutaraldehyde, bis(2-ethylhexyl)adipate, diethyl phthalate, dibutyl phthalate, polycyclic aromatic hydrocarbons (total), POLYBs (total), dioxins (2,3,7,8-TCDD), acrylic acid, naphthic acid, butyl xanthanic acid, β-naphtholone, Anisole, total organic carbon, nitrite (in N) and asbestos.

3. Relationship with relevant laws, administrative regulations and other mandatory standards

This standard is a mandatory national standard, and the legal basis is that the Standardization Law of the People's Republic of China stipulates that mandatory national standards shall be formulated for the technical requirements for ensuring the safety of personal health and life and property, national security, ecological and environmental safety, and meeting the basic needs of economic and social management.

The documents and standards related to this standard are GB 3838 "Surface Water Environmental Quality Standard", GB 17051 "Sanitary Specification for Secondary Water Supply Facilities", GB/T 5750 "Standard Inspection Method for Drinking Water", GB/T 14848 "Groundwater Quality Standard", GB/T 17218 "Sanitary Safety Evaluation of Drinking Water Chemical Treatment Agents", GB/T 17219 "Safety Evaluation Standard for Drinking Water Transmission and Distribution Equipment and Protective Materials", "Safety Evaluation Standard for Drinking Water Transmission and Distribution Equipment and Protective Materials". Sanitary Specifications for Centralized Drinking Water Supply Units and Sanitary Safety Evaluation Specifications for Drinking Water Disinfectants and Disinfection Equipment (Trial Implementation) 8 national standards and ministerial norms, specifically quoted as:

(1) Water quality and sanitation requirements for domestic drinking water sources: When using surface water as a source of domestic drinking water, the water quality of the water source shall meet the requirements of GB 3838 "Surface Water Environmental Quality Standards"; when groundwater is used as the source of domestic drinking water, the water quality of the water source shall meet the requirements of GB/T 14848 "Groundwater Quality Standards";

(2) The facilities and treatment requirements of the secondary water supply in the secondary water supply: it should comply with the provisions of GB 17051 "Sanitary Specification for Secondary Water Supply Facilities";

(3) Drinking water quality inspection method: it should be implemented in accordance with GB/T 5750 "Domestic Drinking Water Standard Inspection Method";

(4) Sanitary requirements for centralized water supply units: should comply with the provisions of the "Sanitary Specifications for Centralized Water Supply Units for Drinking Water";

(5) Product hygiene requirements related to drinking water hygiene and safety: Flocculation, coagulation, disinfection, oxidation, adsorption, pH regulation, rust and scale resistance chemical treatment agents used in the treatment of drinking water should comply with GB/T 17218 "Sanitary Safety Evaluation of Drinking Water Chemical Treatment Agents", disinfectants and disinfection equipment should comply with the "Sanitary Safety Evaluation Specifications for Drinking Water Disinfectants and Disinfection Equipment (Trial)", and the water transmission and distribution equipment, protective materials and water treatment materials for drinking water should comply with GB/T 17219 The safety evaluation standards for drinking water transmission and distribution equipment and protective materials stipulate.