Chemical Parameters in Drinking Water

Exposure to chemical contaminants in drinking water is associated with adverse health effects in human populations. Exposure to the disinfection byproducts trihalomethanes (THMs), for example, has been linked to increased risk of bladder cancer and exposure to lead in drinking water is associated with impaired cognitive development.

Drinking water contains essential minerals that serve as trace elements (micronutrients) in human nutrition and in the food chain. Desalinated seawater is low in mineral content because minerals are removed during the desalination process. Consumption of drinking water with low concentrations of certain minerals—such as calcium, magnesium, iodine, and fluoride—may have adverse effects on health. There is evidence, for example, of a relation between low concentrations of magnesium in drinking water and increased risk of cardiovascular disease and between low calcium content in drinking water and a higher risk of bone fractures in children, certain neurological diseases, preterm birth and low birth weight, and some types of cancer.¹ This issue is particularly relevant in Israel due to the growing use of low-mineral desalinated water in the drinking water systems of most areas of the country. 

The chemical quality of drinking water in Israel is regulated by standards promulgated in 1974 and updated in 2013. The standards set maximum permitted levels of more than ninety chemical contaminants including metals, pesticides, radionuclides, and industrial organic pollutants. The standards require drinking water suppliers to conduct periodic testing for these contaminants in their sources (surface water, groundwater, and desalinated water) and to report the results to the Ministry of Health (MoH). While there is a requirement to add calcium to desalinated water, to date there is no requirement to add magnesium and iodine and the requirement to add fluoride is not implemented. Israel’s drinking water standards include mandatory testing of supply systems for metals (iron, copper, and lead), water treatment chemicals (such as chlorine), and disinfection byproducts (total THMs, chlorite, and chlorate).

Even if the drinking water source is contaminant-free, the supply system can harm the quality of the consumer’s tap water if, for example, pipes leach heavy metals. Therefore, all products that come into contact with drinking water (pipes, faucets, fixtures, and household drinking water systems) must meet the requirements of Israeli Standard 5452, which includes restrictions on lead content and leaching of heavy metals. 

Progress since 2017

The Environmental Health in Israel 2017 report defined challenges relating to Chemical Parameters in Drinking Water. Progress achieved in this area during the past three years is outlined below.

In 2018, MoH conducted a survey to quantify the levels of heavy metals in drinking water in schools (including kindergardens) throughout Israel, taking 1,379 drinking water samples in major cities and small towns in central Israel and in the periphery and analyzing them for lead, iron, and copper content. The concentrations of lead were below the standard in 99.6% of the samples, of iron in 99.7% of the samples, and of copper in 99.9% of the samples (Figure 1).² In the few exceedances that were found, an investigation was conducted, flaws were repaired, and the water was resampled until the concentrations met the standard. There was no evidence of higher lead concentrations in samples containing both groundwater and desalinated water compared to those composed of groundwater only.³ The survey results indicate that lead concentrations in drinking water are lower in Israeli schools than in other countries. Although no surveys of lead in tap water are planned for the coming years, municipal authorities must routinely measure lead and other heavy metals in the supply system and make the findings available on an interactive online platform.

Figure 1: Distribution of Metal Concentrations in Drinking Water in Israeli Schools Relative to Permitted Maximum Levels in Drinking Water Standards
Source: Israel Ministry of Health²

Following a joint effort by MoH and the Ministry of Economy and Industry (MoE), Israeli Standard 5452 for plastic and metal products in contact with drinking water was updated with the addition of a requirement, modeled after the U.S. Reduction of Lead in Drinking Water Act, 2011, to limit lead content to a maximum of 0.25% of product content. The mandate pertaining to plastic products went into effect in March 2018, and that pertaining to metal products went into effect in March 2020. 

Several studies in recent years examined the health effects of consuming desalinated drinking water with low-mineral content. Some of them investigated the association between morbidity and residence in a particular geographic area. Importantly, these studies were not based on individualized indices of mineral consumption by the study participants. Furthermore, residence in a particular geographic area yields limited information on consumption of desalinated water because the national water network provides a dynamic mix of desalinated water, water from the National Water Carrier, and groundwater, making it difficult to predict average mineral content in each geographic area. 

Researchers from Bar-Ilan University and Sheba Medical Center at Tel Hashomer examined magnesium concentrations in tap water and in the blood of 380 patients who had been hospitalized for myocardial infarction in 2015–2017 and monitored the patients’ morbidity and mortality for a year. In areas where much of the water supply is based on desalinated water, lower concentrations of magnesium were measured in tap water and in patients’ blood whereas in areas where the water supply was based on groundwater or surface water higher magnesium concentrations were found (Figure 2). After a year of monitoring, the researchers found a non-significant increase in the risk of severe cardiac events and mortality in areas where much of the water supply was based on desalinated water.⁴

Researchers from Bar-Ilan University, Sheba Medical Center, and Clalit Health Services explored whether increased consumption of desalinated water was followed by an increase in adverse health outcomes (heart disease, diabetes, and high cholesterol) in Clalit patients aged 25–76 in 2004–2013. They found that the risk of heart disease rose in those years, following the substantial increase in the supply of desalinated water in Israel, while the risk of diabetes and high cholesterol remained unchanged.⁵

Researchers from the Hebrew University of Jerusalem studied the impact of desalinated water consumption on concentration of magnesium in blood, thyroid hormones, and use of cardiac medications among residents of Kefar Sava, Nes Ziona, and Rehovot. They found that switching to desalinated water consumption resulted in a decrease in magnesium in blood and thyroid hormone levels and an increase in use of cardiovascular medications.⁶

Figure 2: Concentration of Magnesium in Tap Water in the Homes of Patients with Myocardial Infarction
Source: Shlezinger et al., 2019⁴

As part of a study on the effects of iodine deficiency, researchers from Maccabi Health Services studied concentrations of hormones associated with thyroid function in 400,000 patients in 2010–2013 (before the upsurge in desalination) in comparison with 2014–2016 (after the upsurge). They found no changes in the prevalence of hypothyroidism in various populations before and after the upsurge in desalination. Likewise, they found no differences in hypothyroidism morbidity in patients from geographic areas that received larger quantities of desalinated water (since 2013) in comparison with patients from geographic areas that did not receive desalinated water.⁷

Researchers from the Hebrew University of Jerusalem and Barzilai University Medical Center conducted a cross-sectional study among 105 pregnant women living in an area primarily receiving desalinated drinking water and found that drinking water with low iodine content provided only about 9% of the recommended daily iodine intake. They also found that only a negligible percentage of women consumed iodized salt and only 52% took supplements containing iodine. Among those who did not take supplements, 92% had iodine deficiency. Low iodine intake was significantly associated with thyroid function.⁸

The 2013 drinking water standards include over ninety chemical contaminants including metals, pesticides, radionuclides, and industrial organic pollutants.⁹

The MoH’s public health laboratory and other laboratories (e.g., that of Mekorot, the national drinking water supplier) have been testing water with new analytical techniques in order to detect chemicals not included in the drinking water standards. MoH is using data collected by the labs to create a database of contaminants in drinking water. This includes data on volatile and semi-volatile organic micropollutants from different sources and all metals in the supply systems. The data serve as a decision support tool for regulatory activities. 

The MoH database includes, for example, data collected by MoH’s public health laboratory in 2017–2018 that indicated the presence of the herbicide bromacil in 43% of drinking water wells, with an average concentration of 0.3 µg/L. In addition, MoH calls for monitoring the presence of the pharmaceutical carbamazepine (CBZ) and other organic micropollutants in wells at continual risk of contamination (in dense residential areas). The presence of these substances in wells may indicate the possibility of groundwater pollution from sewage. Between 2012 and 2020, only 160 of 711 collected water samples had quantifiable concentrations of CBZ (>10 ng/L); the concentration of CBZ in the other 551 samples was not quantifiable. MoH also monitors toxins released by cyanobacteria in Lake Kinneret (the Sea of Galilee). Cylindrospermopsin, a cyanotoxin, is unregulated in Israel but is carefully monitored in drinking water, especially during seasons in which concentrations are elevated. 

There is currently no comprehensive data in Israel on concentrations of per- and polyfluoroalkyl substances (PFAS) in drinking water. The Water Authority conducted a survey in wells (not supplying drinking water) in vulnerable locations (such as fuel tank farms, landfills, and military airfields) and found high concentrations of perfluorooctanoic acid (PFOA)—as much as 25,000 ng/L—and perfluorooctanesulfonic acid (PFOS)—as much as 610,000 ng/L, along with evidence of contamination with other PFAS chemicals (PFBS, PFHxA, PFHxS, PFHpA, PFNA). In a second survey, which included drinking water wells, the Water Authority found lower PFAS concentrations: The maximum PFOA value was 47 ng/L and the maximum PFOS value was 330 ng/L, compared with the Canadian drinking water standard of 200 ng/L for PFOA and 600 ng/L for PFOS. The Water Authority and MoH are planning additional surveys.

Drinking water has not been fluorinated in Israel since 2014. According to HMO data from 2013, the year before fluoridation was discontinued, fewer than 5,000 children up to age five underwent dental procedures with anesthesia. In 2018, four years after the discontinuation of fluoridation, the number of pediatric dental sedations in this age group exceeded 10,000, an increase of over 100%.

In a 2019 survey of kindergartens in southern Israel (Beer Sheva, Mitzpe Ramon, Rahat, and Kuseife), MoH examined 283 children and found that 33% of them had no dental caries, compared to 38% of children in a 2014 national survey. The 2019 survey found an increase in caries in Jewish localities but not in Bedouin ones. Since desalinated water is low in minerals (including fluoride), the researchers concluded that the children in Bedouin localities, who drink groundwater that contains natural fluoride, were not adversely affected by the discontinuation of fluoridation. 

According to nationwide data collected by the School Dental Service among twelve-year-olds, the percentage of children without dental caries declined from 26% in 2015 to 23% in 2017.¹⁰

Research on Drinking Water Quality in Israel

• Researchers from the Technion and Mekorot developed an algorithm for rapid detection of drinking water contamination (including nitrites and nitrates) using a UV spectrophotometer. When tested with both artificial and real life datasets, the algorithm demonstrated high detection and low false alarm rates.¹¹ 
• Several studies, mentioned above, examined the health effects of consuming desalinated drinking water with low mineral content on rates of heart disease, diabetes, and high cholesterol⁵; hypothyroidism⁷; iodine intake and thyroid function⁸ and magnesium in blood; thyroid hormones; and use of cardiovascular medications.⁶ 
• Researchers from Ben-Gurion University of the Negev, in collaboration with Dutch and British colleagues, developed a sensor for monitoring toxic compounds in water using genetically engineered (non-pathogenic) bacteria that respond to changes in water quality by emitting luminescence. The sensor was successfully tested in laboratory conditions and at the Meuse River in the Netherlands.¹² 
• Researchers from Mekorot and the Geological Survey of Israel, in collaboration with French researchers, developed a technique for monitoring the “isotopic fingerprints” of water (concentrations of isotopes of various elements, such as boron). The technique makes it possible to monitor desalinated water and reclaimed wastewater (such as that treated at the Shafdan facility) and facilitates the analysis of the water cycle (i.e., which water reaches which areas). It may be helpful in planning Israel’s water economy.¹³

Future Challenges

Theoretical work for a pilot study on the feasibility of adding magnesium to desalinated water was completed in 2020 and the on-site study is planned for 2021. A challenge for the coming years is to track the results of the pilot study and translate the findings into policy—compulsory addition of magnesium and an optimal level of this mineral in drinking water. In light of the rapid increase in consumption of low-mineral desalinated water, there is a need to examine the intake of micronutrients in Israel—including iodine, magnesium and fluoride—by using nutritional biomarkers. It is also important to study the effects of using low-mineral water in agriculture on the nutritional value of agricultural produce.

In 2018–2020, the EU issued recommendations on updating drinking water standards. The recommendation to lower the lead standard in drinking water to 5 μg/L will go into effect within fifteen years of its approval. One challenge for Israel in the coming years is to toughen its own standard on lead content in drinking water. Based on lead monitoring in the supply network, 99.6% of results comply with the standard. However, about 150 small localities do not routinely monitor lead in the supply network as required. It is imperative that all localities monitor lead in their supply networks in accordance with requirements in the drinking water standards. In addition, standards need to be set for new contaminants, such as haloacetic acid disinfectant byproducts and PFAS. To accomplish this, it will be necessary to collect data on the presence of haloacetic acid disinfectant byproducts and PFAS countrywide. Preliminary data from Water Authority surveys shows significant PFAS groundwater contamination in hotspots in Israel.

THMs are disinfection byproducts that are formed during chlorination of water with high levels of organic matter (such as surface water). Given the range of drinking water sources used in Israel (desalinated water, groundwater and surface water), each with its own level of organic material, there are major geographical and temporal fluctuations in concentrations of THMs. In communities in northern Israel that receive surface water from the Sea of Galilee, over 5% of sampling results exceeded the standard of 100 µg/L in the summer of 2020. Due to the high bromate content of the Sea of Galilee, it is likely that much of the THMs are brominated, although bromoform is not routinely monitored in Israel. Mekorot has introduced several methods to reduce THM levels including evaporation stations, reduction of stagnation time, and a shift to chlorine dioxide disinfection. Notably, use of chlorine dioxide may result in the formation of two additional toxic disinfection products, chlorite and chlorate. Efforts to reduce THMs, chlorite and chlorate concentrations should be monitored. There is also a need for a reassessment of the Israeli standards for these disinfection byproducts.

Historically, the pesticides atrazine and simazine have been major contaminants of drinking water in Israel. Following the reduction in the use of atrazine and discontinuation of the use of simazine (2012–2014), atrazine concentrations in drinking water sources have decreased but simazine concentrations have not. It is important to continue monitoring concentrations of atrazine, simazine, and additional pesticides with potential for groundwater contamination.

This chapter and all other chapters in the report was written by a team of scientists and professionals from the Ministry of Health, in collaboration with Environment and Health Fund.