Sulfate is a chemical compound that has a chemical formula SO42- and is found in abundance in the natural environment in the form of sulfur and oxygen in minerals consisting of a single sulfur atom and four oxygen atoms chemically forming a tetrahedral star shape. Sulfates are categorized as salts when they coexist with sulfuric acid and can bond with metals easily by using their oxygen atoms as ligands as a connection, which is commonly referred to as a chelate, commonly forming a metal ion complex, denoted as FeSO4. Due to the large number of electrons it possesses, sulfate can use both a single pair or a multitude of electrons to bond with metal, resulting in monodentate ligand and multidentate ligand respectively.
Sulfates are not commonly found in food products, however, a derivative of sulfates, namely sulfites which are composed of three oxygen atoms instead of four alongside a single atom of oxygen, is found in numerous food products. Some of such products are baked goods, canned vegetables, jams, soup mixes, gravies, pickled foods, dried fruit, trail mixes, potato chips, beers and wines, sparkling grape juices, apple cider, vegetable juices, condiments, guacamole, maraschino cherries, fresh and frozen shrimps, molasses, dehydrated, precut, and peeled potatoes, tea, and bottled lemon and lime juices among others. Sulfites in foods and beverages prevent oxidation and browning of light-colored fruits and vegetables, control microbial growth, prevent melanosis and black spots, prevent decomposition, preserve flavor, prevent spoilage, and condition dough, and therefore can be found in numerous products. In order to avoid consuming them, the consumer should look for labels containing ingredients such as sulfur dioxide, potassium bisulfite or metabisulfite, sodium sulfate, bisulfite, or metabisulfite as they signify the existence of sulfites in the product on display. Sulfites are toxic to human beings and have been directly linked with occupational diseases and deaths, such as fatal reactions in shrimp fishermen who use dry sodium metabisulfite after the chemical reacts with acids and water to release toxic sulfur dioxide gas, along with several types of allergies that cause asthma hives, nausea, diarrhea, seizures, death-inducing shock, tissue swelling, and abdominal pain. Consumption of sulfites by human beings has been known to cause other symptoms as well, such as flushing, severe respiratory reactions, vomiting, dizziness, contact dermatitis, and feelings of temperature change.
Sulfate occurs naturally in water, referring to water that is naturally found in seas, rivers, and lakes, with seawater containing around 2700 mg of sulfate per liter, rivers containing 0 to 630mg/liter, lakes containing 2 to 250 mg/liter, groundwater sources containing 0 to 230 mg/liter, and rainwater containing 1.0 to 3.8 mg/liter. As for drinking water for human consumption, the maximum contaminant level has been established as 250 mg/liter as a guideline for state and public water systems, with an estimated 3% of the public drinking water systems in the US containing higher sulfate levels than advised. High levels of sulfate reduce water quality because the taste of the water changes, foul odors can develop, and the aesthetics of water can be distorted. Reverse Osmosis, Distillation, and Ion Exchange water treatment systems are generally used to reduce sulfate levels in the water, filtering water for excessive sodium particles to give it a better taste, neutral smell, clear aesthetics, and less chemical composition.
|Name||Atomic Number||Atomic Mass||Year of Discovery||Discoverer|
|Sulfate (SO42-)||16||96.06 g/mol||1916||Gilbert Lewis|
Sulfate is a naturally-forming mineral that is caused by the formation of salt due to sulfuric acid reactions and usually infiltrates into water sources through the soil and rocks. Although up to 500 mg/L of sulfate intake/consumption is acceptable for human beings per day, sulfate still remains as one of the chemicals that need to be filtered in drinking water in order to regulate the chemical composition of such water before being consumed by human beings. The incoming/contaminated water needs to be analyzed regularly to ensure that the sulfate level does not drop below or increase above a pre-specified limit and in the case of high sulfate content, such water needs to be filtered using reverse osmosis, distillation, anion/ion exchange, or adsorbent/activated carbon media filtration.
Sodium is most commonly found as Sodium Lauryl Sulfate (SLS) or Sodium Laureth Sulfate (SLES) in consumer products obtained from fatty alcohols found in palm kernel oil or petroleum oil which are then mixed with sulfur trioxide and sodium carbonate to produce the mentioned sulfate compounds. Some of the most common and popular consumer products which contain SLS and SLES are laundry detergents, liquid hand soap, dish detergents, shampoos, toothpaste, bath bombs, and face cleansers where the sulfates found are labeled as surfactants as they bind to various types of pollutants such as oil, fat, grease, and dirt to remove than from the surface of objects, while sulfates are preferred in shampoos and soaps because they produce lather. Such lather is the main benefit of sulfates when used in shampoos, soaps, and conditioners because sulfate in lather helps remove grime and dead cells from hair and skin with ease.
While no evidence exists which directly links sulfates in the form of SLS and SLES to serious complications like cancer, infertility, or development issues, the chemicals are directly linked to issues like eye, skin, mouth, and lung irritation, with the amount of irritation increasing along with the time the given chemicals stay in one’s system, while people with sensitive skin can also suffer symptoms like clogged skin pores and increased acne formation. More specifically speaking, the side effects of extended exposure to Sodium are diarrhea, intestinal pain, lung irritation, dry skin, as well as dermatitis, and edema. Diarrhea is caused by high concentrations of sulfates in drinking water and usually occurs in children and sensitive people of older age. Intestinal pain and cramps are also caused by drinking water high in sulfate content, while lung irritation is usually caused by inhaling polluted air, mainly due to excessive sulfur dioxide from burning fuel which transforms into sulfuric acid and damages human and animal lungs. Similarly, dry skin is also caused by excessive contact with sulfates in consumer products such as laundry detergents, soaps, and shampoos, while SLS and SLES’ inclination to remove too much oil from human skin and thus reduce the skin’s protective qualities causes not only dry skin but also other complications like redness and itchiness. Dermatitis and edema are also triggered by consumer products that contain SLS and SLES as these chemicals cause skin reactions especially in people who have conditions such as eczema and rosacea. Sulfate has also been linked with several types of allergic reactions, while sulfate compounds also have a negative impact on the environment, as they are made from palm oil, which is obtained from tropical rainforests, are toxic to animals who drink sewer water high in sulfate content, and are derived from petroleum, which is extracted and used in certain methods that contribute to global climate change, pollution, and the production of greenhouse gases. Similarly, testing of sulfate products on animals before being used by human beings leads to serious side effects on such animals, causing significant damage to their skins, eyes, and lungs. Thus, although it would be wrong to label sulfates as toxic for human beings, they do have serious side effects and when consumed as drinking water, high sulfate content water is toxic for animals.
What is the use of Sulfate?
Sulfate is used by human beings in numerous different ways due to its chemical characteristics that offer benefits in hygiene, physical therapy, building/construction, and environmental control. The most common uses of sulfate are listed below:
- Cleaning and personal care: Sulfates are usually used in cleaning and personal care products that are commercially available thanks to their capability to generate lather and remove various types of oil, grease, and dirt from human hair and skin.
- Therapy: Magnesium sulfate in the form of Epsom salts is used in therapeutic baths in physical therapy.
- Plaster: Gypsum, which is derived from hydrated calcium sulfate is used to produce plaster for medical and construction purposes.
- Algaecide: Copper sulfate is used as an algaecide and the sulfate ions are used as counter-ions for certain cationic medications.
How does Sulfate affect Water Quality?
The official definition of water quality is the acceptable condition of water including its chemical, physical, and biological characteristics in terms of its suitability for a specific purpose, namely its drinkability, usability for cleaning and personal care, or swimming, based on a number of factors like the concentration of dissolved oxygen, levels of bacteria, salinity, and turbidity of such water. In certain bodies of water that are found in biologically rich environments, other factors such as the concentration of microscopic algae, as well as pesticide, herbicide, heavy metal, and other contaminant quantities are taken into consideration when measuring water quality. In the light of such a definition, it can be stated that high concentrations of sulfate in water directly affect its taste, odor, and aesthetics. High sulfate water usually has a bitter and medicine-like taste due to increased hardness, has a strong and foul odor that is reminiscent of rotten eggs, and has a murky appearance. According to the Guidelines for Water Quality (GDWQ), which has been echoed by the Environmental Protection Agency (EPA), sulfate concentrations need to be maintained at or below 250 mg/liter, while states are granted the freedom to establish higher or lower levels depending on their local conditions, while for consumers seeking acute effects, or the total absence of laxative effects, a sulfate concentration of 500 mg/liter is recommended, depending on the absence of other osmotically active materials in water that can lower the sulfate level and cause a laxative effect.
How can Sulfate contaminate water?
Sulfate minerals can be found naturally nested in certain types of soil and rocks and therefore naturally make their way into water sources. However, sulfate contaminates water essentially through waste and industrial discharge produced by mines, smelters, paper mills, textile mills, tanneries, power plants, and metallurgic refineries, that contaminate the main water supply accessible to human beings for use and drinking purposes in the form of chemicals and harmful substances. The contaminant candidate list includes sodium, potassium, and magnesium sulfates due to the high solubility of these chemicals. Due to the combustion of fossil fuels, dilute sulphuric acid is formed when atmospheric sulfur trioxide is combined with water vapor in the air, coming down on earth as acid rain and increasing sulfate levels in groundwater, rivers, lakes, seas, and oceans. Once high sulfate water reaches water systems used by human beings, the sulfate minerals in the contaminated water can cause scale buildup in water pipes to change the taste, smell, and texture of the water, have a laxative effect on human beings and young livestock, and make the water less usable for functions such as cleaning. Researchers Huiwei Wang and Qianqian Zhang have carried out extensive research regarding the Kinetic Isotope Fractionation technique to focus on its use in Graphite-Reduction, Fluorination, High-Temperature Pyrolysis, Chemical Precipitation, Triacid, and the Flame Heating methods and revealed that the given technique provides excellent levels of stabilization for both sulfur and oxygen isotopes to offer excellent opportunities to detect sulfate levels in solutions with high precision, especially in industrial settings where a large number of diverse chemicals and substances are found in groundwater.
What is the toxicity level of Sulfate?
The recommended level of sulfate in drinking water varies between 100 and 1000 mg/L per day depending on the soil types in the area where the drinking water is obtained, how much water is being consumed per day, and the age group the consumer belongs to, such as infants, teenagers, or adults. Sulfate toxicity has been identified with two types of consumption, namely through oral exposures and inhalation exposures. In both cases, the forms of toxicity have been identified as acute toxicity, sub-chronic toxicity, chronic toxicity, developmental and reproductive toxicity. In acute toxicity contracted through oral exposure, the most commonly observed health effects are laxative action with the gastrointestinal system being directly targeted where increased motor activity is observed leading to poor absorption, the exertion of osmotic pressure due to soluble ions which causes retention of fluid in the intestinal lumen, the expansion of the fluid volume in the intestinal tract due to decreased water absorption in the small intestine and increased stimulation in the secretion of intestinal, gastric, and pancreatic fluids.
When specifically considering the toxicity level of Sodium Lauryl Sulfate (SLS), it is seen that the lethal dose/concentration of the substance for acute oral poisoning is 1299 mg/kg, for acute dermal poisoning is 2000-20000 mg/kg, for acute inhalation poisoning is above 3900 mg/m3/1H, for lowest repeated dose is 100 mg/kg per day, and for aquatic toxicity in 96 hours is 1-12 mg/L. The more commonly observed non-lethal toxic effects of SLS on human beings are skin, eye, and respiratory tract irritation mainly due to cosmetics products, while fore numerous forms of aquatic life, SLS can be highly toxic possibly leading to cases of death. As for Sodium Laureth Sulfate (SLES), due to different standards of the substance’s manufacturing process, it can be contaminated with substantial amounts of ethylene oxide and 1,4 dioxane to produce carcinogenic effects on humans. Ethylene oxide also has an adverse impact on the human nervous system, leading to developmental problems in human beings, while the persistent existence of 1,4 dioxane in cosmetics products is responsible for harsh cases of skin and eye irritation in human beings when consumed in large quantities.
What are the health risks of Sulfate in drinking water?
When ingested in high amounts, high sulfate content drinking water can cause health issues such as:
- The alteration of methaemoglobin and sulphaemoglobin in the human mechanism
- Reduced lung function
- Aggravated arithmetic symptoms
- Increased symptoms of chronic heart and lung diseases might lead to more frequent episodes of hospitalizations and death
In addition, exposure to high concentrations of Sulfate over long periods of time has been associated with nervous system diseases such as Parkinson’s disease.
How to determine Sulfate in water?
The most commonly used method to determine the level of sulfate in water is the turbidimetric method where the sulfate ion is converted to a barium sulfate suspension under controlled laboratory conditions to result in turbidity which is measured by a nephelometer, filter photometer, or spectrophotometer before being compared with the results of a standard sulfate solution. Barium sulfate formed after the barium chloride is added to the given sample results in precipitation in a colloidal form which is catalyzed when an acidic buffer, which consists of magnesium chloride, potassium nitrate, sodium acetate, and acetic acid, is present in the given solution. Following such precipitation, filtration needs to be applied to the resultant solution before the results are analyzed using a nephelometer that measures the amount of light scattering in the resultant solution. This method employs a highly fast technique and is suitable for sample solutions that have sulfate concentrations higher than 10 mg/L before they are diluted for analysis. Similar techniques can be used with sulfate and strontium chloride solutions, silver nitrate and sulfate ions, sulfate ion and calcium chloride, sulfate and lead acetate where precipitation is measured to determine the levels of sulfate in such sample solutions. Several home water testing kits and systems are commercially available in the market but most of such testing is usually for preliminary and observational purposes with the obtained results having to be submitted to scientific labs for further analysis before a reliable conclusion can be drawn.
Can Sulfate be filtered out in the water?
Yes, sulfate in water can be filtered using the methods of reverse osmosis, distillation, anion/ion exchange, and adsorptive media filtration. In the first method, water is pushed through a membrane consisting of numerous small-sized pores where contaminants like sulfate are filtered out to the efficiency of 93-99%, while in the second method water is boiled to produce steam with the remaining particles in the water, including contaminants like sulfate behind before being re-condensed to clean water with almost 100% of the sulfate being eliminated this way. When the third method is used, negatively charged ions containing sulfate are replaced with sodium chloride or potassium chloride in the form of salt usually in large quantities for commercial, livestock, and public water supplies, and in the fourth method charged media beds are used to force ions carrying the opposite charge, including sulfate particles, are sucked out of the solution and kept on the media to purify the water sample.
How to remove sulfate from drinking water?
Purity, taste, pleasant smell, and proper composition are all important aspects to be sought for in drinking water for which high concentrations of substances like sulfate are not tolerable. The following are detailed descriptions of how sulfate can be removed from drinking water:
- Reverse Osmosis: In a typical RO filtration system, four filters are employed to remove contaminants out of the incoming water, namely a sediment filter, a carbon filter, a reverse osmosis membrane, and a post-filter/polishing filter. An RO system initially forces unfiltered water through the pre-filter before forcing the water through a semipermeable membrane where the dissolved solids in the water are removed and filtering it with a post-filter to remove odors and foul taste before the water reaches the faucet. Specifically speaking, the sediment filter removes contaminants such as dirt, dust, and rust, the carbon filter removes volatile organic compounds, chlorine, and other contaminants responsible for bad taste or odor in the water, and the semipermeable membrane removes up to 99% of the total dissolved solids, including sulfate.
- Distillation: Distillation is a water treatment technique that relies on evaporation to purify water where the incoming contaminated water is heated to form steam to remove inorganic compounds and large non-volatile organic molecules are left behind while the purified water in the form of steam is cooled and condensed to re-form into a liquid state. Being highly effective in removing inorganic compounds like metals such as iron and lead, nitrate, hardness caused by calcium and magnesium, microorganisms like bacteria and certain viruses, benzene, toluene, and other particulates, distillation also produces desirable results in removing sulfate as well.
- Anion/Ion Exchange: Also referred to as the ion exchange method, anion exchange percolates incoming contaminated water through spherical shaped bead-like resin materials where the calcium and magnesium ions in the water are exchanged for sodium ions through the processes of softening and deionization. The first process is usually used as a pre-treatment method to reduce water hardness before the RO processing while the second process utilizes anion exchange ions made of styrene which contain quaternary ammonium groups which exchange a hydroxyl ion for any ion encountered to form pure water. It is essentially the second process of deionization which removes a substantial portion of sulfate in water, while a certain smaller portion of sulfate can also be removed during the softening process as well.
- Adsorptive/Activated Carbon Media Filtration: In this technique, dissolved molecules or small particles in water, which is the adsorbate, are attracted to and become attached to the adsorbent using the van der Waals forces on an atomic or molecular scale, The adsorbent is usually an activated carbon filter made of carbon-based materials such as coal or wood that are heated without using oxygen to produce charcoal, which is then heated with steam or carbon dioxide to a temperature of above 1000 Celsius to remove all the particles in water except for carbon. The resultant structure is airy, porous, and delicate, consisting almost purely of carbon, making it utile for filtration of media after being crushed to powder and getting mixed with binders to form granules of desired size ranges. It is essentially the size of the activated carbon which determines its efficacy in filtering water by adsorbing various contaminants, with the typical size being 1,000 square meters per gram, along with the structure and distribution of the pores situated in the filter as these factors determine the size of the molecules to be adsorbed. For filtration systems treating drinking water, powdered carbon is usually the preferred filter material because it acts faster and has more reliable mechanical properties for such a purpose, making it the responsible agent to filter sulfate in drinking water.
The given methods have higher and lower utility for different types of water sources and the different purposes the filtration/treatment method is used for. Reverse osmosis is usually recommended to be used for water designated as drinking water because it produces the highest level of efficiency in filtration and forces incoming/contaminated water into a multitude of pre and post-filtration stages, meaning that it can be applied to groundwater, tap water, and well water with ease. Distillation is also applicable to drinking water but is usually used for industrial applications where the taste and smell of the resultant water are not significant for the end-user. Anion/ion exchange is also utile for drinking water purposes, but it is also used in industrial settings due to the ease of repeatability of the process thanks to the use of easily regenerating resins and thus the low costs involved in the operation of the anion/ion exchange systems. Adsorptive/activated carbon media filtration technique is also highly popular for use with drinking water coming from well water, groundwater, and tap water, but since most such systems are installed in home or office settings, the technique is more affiliated with tap water filtration.
Can boiling tap water remove Sulfate?
A simple procedure of boiling tap water does not remove sulfate but as mentioned previously, the distillation process does indeed boil water to separate clean water from contaminants in the form of steam, while contaminants like sulfate are left behind and thus eliminated from the water solution. The efficiency of the distillation process, when carried out properly using a suitable type of water, can reach 100%, which means that technically speaking boiling tap water can remove sulfate if and when the distillation process is applied.
What kind of water filter can remove Sulfate in water?
Different kinds of water filtration types can remove sulfate in water at different levels of success, namely the previously mentioned reverse osmosis, distillation, anion/ion exchange, and adsorptive media filtration methods. Below is the list of their efficiencies for filtrating water:
- Reverse Osmosis: Reverse osmosis filtration technique can remove up to 99.9% of all contaminants, including sulfate.
- Distillation: The efficiency of the distillation technique in removing contaminants, including sulfate, was recorded to be 83.15% in natural convection systems and 63.54% and 59.76% at 30 kg/h and 50 kg/h flow rates respectively, when carried out in 1686 ml/day and 1568 ml/day systems.
- Anion/Ion Exchange: The efficiency rate of the anion/ion exchange water treatment technique for removing contaminants, including sulfate, ranges between different products, with most standard and commercially available models offering up to 80% effluent water that is 60% salt and 30% chemical-free, while in industrial settings and applications, the efficiency of the technique in removing salt in water can increase up to 99% at up to 840 mL/min rate.
- Adsorptive/Activated Carbon Media Filtration: These systems utilize anthracite and bituminous organic filters along with steam and chemical-based activation methods, which operate at 800-1,000°C and 500-800°C and instantaneous water-gas reactions and a paste-form of phosphoric acid and zinc chloride respectively to activate the carbon contained in the filters to remove up to 70% of contaminants, including sulfate, in water.
Statistical information reveals that the most efficient technique in removing sulfate in incoming/contaminated water is reverse osmosis with 99.9%, followed by the distillation technique with 83.15% using natural convection, the anion/ion-exchange technique with 80% efficiency, and the adsorptive/activated carbon media filtration technique with 70% efficiency rate. In industrial applications, the efficiency of the distillation technique increases to 99%, making it almost equally effective in removing sulfate as the reverse osmosis method.
What conditions affect the sulfate amount in water?
The amount of sulfate found in water depends on both the natural and artificial/man-made inputs as sulfate is introduced into the natural sources of water through such methods. The most common conditions that affect the amount of sulfate in water are listed below:
- Rainfall/mass-scale water movement: In terms of the conditions that affect the infusion of sulfate in water through such natural and artificial/man-made inputs, the most dominant one is the amount of rainfall and other sources of heavy water movement that erodes rocks and soil to increase mineral deposits into sources of water, including sulfates.
- Geological changes: Similarly, natural and/or manmade geological changes to Earth’s soil also contributes to such increase in sulfate infusion into water sources as the act of moving large bodies of land or rocks rearranges underground water sources, breaks down sulfate-containing formations to release sulfate into the surrounding environment, or simply carry high sulfate content formation to the vicinity of existing water sources to increase the chance of infusion.
- Industrial waste/disposed matter: In terms of artificial/man-made inputs, the opening of new mines or industrial plants such as smelters, paper mills, textiles mills, tanneries, and metallurgic refineries, or energy facilities like power plants increases the possibility of sulfate infusion into the surrounding areas where water sources exist. As byproducts and waste containing high levels of sulfate are disposed into the surrounding environment through channels in liquid wastewater form or are stored in disposal sites in their solid-state, the substances either directly infuse into soil or water sources if they are contained in liquid form, or slowly infuse into the surrounding area over long periods, granted the disposal site is not cleaned or carried away to another location, where the same possibility exists if the disposed of material sits in the new site for prolonged periods of time.
- Other/miscellaneous: Soil composition, temperature, and the availability of groundwater in the vicinity of given such sites are conditions that directly impact the rate of sulfate infusion to groundwater.
Does stagnant water have Sulfate?
Yes, stagnant water has sulfate. Stagnant water contains numerous chemicals and contaminants due to the fact that it has lost its circulation, making it prone to the accumulation of substances. However, the most commonly observed and experienced issue with stagnant water is not in regards to its sulfate content but rather its content of harmful organic materials such as bacteria. Therefore, although stagnant water has the capacity to contain sulfate, unless it is situated near a large source of sulfate with access to the given stagnant water source, stagnant water does not pose a significant threat of high sulfate composition. All the mentioned water filtration/treatment techniques, namely reverse osmosis, distillation, anion/ion-exchange, and adsorptive/activated carbon media filtration can be used but as pre-treatment, it is recommended to use the distillation method to normalize the highly contaminated stagnant water, after which anion/ion-exchange, adsorption/activated carbon media filtration, and reverse osmosis should be applied to stagnant water to further filter and normalize it for human daily or consumption use.
Does well water have Sulfate?
Yes, sulfate can commonly be found in well water. As stated before, sulfates are found naturally in both soil and rock formations and because well water, or groundwater, is in a constant state of exchange with its surrounding environment, the sulfate in soil and rock formations can infuse into well water and get mixed with it. The proper way to deal with high concentrations of sulfate in well water is to either install a whole-house treatment system in the case that sulfate is found in extremely high concentrations or a kitchen sink installation to filter drinking and cooking water.
Does tap water have Sulfate?
Yes, sulfate ions can be found in tap water because all tap water comes from natural sources before being treated in specific filtration and chlorination facilities. The results of a high concentration of sulfate in tap water are a foul odor, salty taste, and scaling in plumbing infrastructure.
What is the safe amount for consumption of Sulfate in drinking water?
Optimal drinking and usable water should not contain more than 250 mg/L of sulfate while the maximum allowed amount of sulfate for human use is 500 mg/L. It is also recommended that human beings should not consume more than 800 mg/L of sulfate per day.
Do the top countries that produce Sulfate have any problems with their drinking water?
No, the countries that produce sulfate do not have problems with their drinking water. As previously stated, sulfate is found naturally in groundwater as well as other sources of water that have contact with soil and rocks but the act of sulfate infusion into the water for human consumption and use is controllable. Therefore, it cannot be stated that a country’s capability to produce large quantities of sulfate has problems related to their drinking water because of sulfate as most of such countries are developed nations with advanced water filtration and treatment systems. Sulfate is commercially available in the form of cobalt, sodium, potassium, and zinc sulfate, with the largest producers being China, the USA, Germany, India, Brazil, France, and the Netherlands. China has suffered cases of water contamination due to high concentrations of sulfate along with arsenic, and fluoride, due to human and industrial waste, leading to high numbers of cases of liver, stomach, and esophageal cancer. China has extended chlorination and filtration systems for its urban areas but well water and groundwater still remain viable options in its rural areas, making the Chinese public living in such rural areas subject to unregulated and untreated water. Most of the other mentioned countries are some of the most industrially advanced and developed nations in the world and except for India and Brazil, there have not been reported incidents of mass-scale contamination in drinking water. In India, nitrate contamination seems to be the main problem, and in Brazil, the main sources of water contamination have been reported as pesticides, heavy metals, organic waste, endocrine disruptors, pharmaceuticals, personal care products, and illicit drugs. There has also been a recent incident in the US city of Flint, Michigan, but the contaminants were lead and Legionella bacteria and not sulfate.