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Aluminium Excess aluminium poses concerns for Alzheimer disease. Aluminium is the most abundant metal in the crust of the earth. |
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Antimony Antimony is commonly found along with arsenic in groundsource waters. It also found as 5% when mixed with 95-5 copper pipe solder. This solder replaced the 50-50 lead bearing solder used until 1988. If the water has a low pH (less than 7.0) traces of antimony or copper can be found from pipe itself. Antimony is considered to be carcinogenic to humans. |
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Arsenic Arsenic is widely distributed in the earth's crust and is present in trace amounts in all living matter. Arsenic is used in processing glass and pigment, hide tanning, as pesticides, feed additives, and pharmaceuticals. Health effectsDetrimental effects of ingesting arsenic have been documented over a short period of just a few weeks. Symptoms and effects will show after a short exposure time. For a long term exposure, the symptoms and effects become very serious and life-threatening.
Arsenic is classified as being carcinogenic to humans. |
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Asbestos The chemical nature of asbestos makes the mineral useful for asbestos-cement (A/C) sheet and pipe, electrical and thermal insulation and friction products, such as brake linings. Asbestos is introduced into water as a result of its extensive industrial use. Asbestos poses a health hazard when inhaled, however there is no consistent, convincing evidence that ingested asbestos is hazardous to health. |
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Barium Barium occurs in a number of compounds, most commonly barite (barium sulphate) and witherite (barium carbonate). Barium compounds have a wide variety of industrial applications, being used in the plastics, rubber, electronics, textiles and oil and gas industries. Barium is not considered to be an essential element for human nutrition. Soluble barium salts are highly acutely toxic. There is inadequate data for its evaluation as a carcinogen. |
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Boron Boron occurs naturally in over 80 minerals and in the earth's crust. Boron compounds, particularly boric acid and sodium borate (borax) are used in the preparations of disinfectants, in the manufacture of borosilicate glass, as insecticides, and as cleaning compounds. High levels of boron (over 20 mg/L) are found in deep wells. A telltale sign of excess boron in water is problems with lawns - excess boron will kill grass. Boron is classified as being probably not carcinogenic to humans. |
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Bromate Bromate is powerful oxidizer, used when dying textiles. Bromate can also be formed when hypochlorite solutions are used to disinfect drinking water. In chlorine-dixoide treated waters, bromide in the presence of sunlight can oxidize to bromate over large pH range. Symptoms of bromate poisoning include nausea and abdominal pain. Most health effects are reversible. Bromate has been classified as possibly carcinogenic to humans. |
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Cadmium Cadmium is not considered to be an essential element in human nutrition. Cadmium is present as in impurity in galvanized pipes, as a constituent of solders used in fitting water heaters and coolers, and incorporated into black polyethylene pipes. Cadmium can cause hypertension, vomiting, softening of bones and renal disease and may interfere with the body's ability to regulate zinc and copper concentrations. |
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Calcium Calcium is an abundant natural element, entering the freshwater system through the weathering of rocks, from the soil through seepage, leaching, and runoff. Calcium oxide (lime) is used in mortar, stucco, plaster, pulp and paper production, sugar refining, petroleum refining, tanning, and as a wastewater treatment chemical. Calcium is on the principal cations associated with hardness in drinking water. Adverse effects of calcium are observed only following the intake of extremely large quantities of calcium. |
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Chloramines Monochloramine may be a by-product of drinking water chlorination or it may be added to maintain residual disinfection activity in potable water distribution systems. Monochloramine can reduce the formation of trihalomethanes and other by-products associated with chlorine use, possible control of bacteria biofilm in the distribution systems, and the reduction of taste and odour problems associated with chlorination of drinking water supplies. Available epidemiological studies are inadequate for the assessment of the carcinogenicity of monochloramine in humans. It should be emphasize that this guidelines is based on the risk evaluation for monochloramine only, as it is usually the predominant chloramine and as information on dichloramine and trichloramine toxicity is insufficient to establish guidelines for these two compounds. |
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Chloride Chloride is present in natural waters due to the dissolution of salt deposits, salting of roads, and effluents from chemical industries. Chloride is generally present at low concentrations in natural surface water in Canada, although high concentrations may be found in drinking water derived from groundwater sources. Chloride is the most abundant anion in the human body. No evidence has been found suggesting that ingestion of chloride is harmful to humans. |
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Chlorite Chlorine dioxide is used for disinfection and odour/taste control of water and as a bleaching agent for cellulose, paper pulp, flour and oils. Sodium chlorite and sodium chlorate are both used in the production of chlorine dioxide as well as for other commercial purposes. Chlorine dioxide rapidly decomposes into chlorite, chlorate and chloride ions in treated water, chlorite being the predominant species; this reaction is favoured by alkaline conditions. The major route of environmental exposure to chlorine dioxide, sodium chlorite and sodium chlorate is through drinking-water. It has been concluded that chlorite is not classifiable as to its carcinogenicity to humans. |
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Chromium Trivalent chromium is the most common natural state of chromium and is essential for humans. It is considered to be non-toxic, however, if it is present in raw water, it may be oxidized to hexavalent chromium during chlorination. Hexavalent chromium is not considered to be an essential element, and the toxic effects of chromium in humans are attributed primarily to this hexavalent form. Chromium has been linked with cancer following occupational exposures, although a recent report states that there are inadequate data to conclude the chromium is carcinogenic via ingestion. |
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Copper High levels of copper occur if corrosive water comes in contact with copper plumbing and copper-containing fixtures in the water distribution system. Copper is also found frequently in surface water and some groundwater. Distributed water contains considerably more copper than the original water supply because of the dissolution of copper from copper piping. It has been estimated that drinking water contributes approximately 11% of an adult's total daily intake of copper, with the rest coming from food. If corrosive water remains motionless in the plumbing system for six hours or more, copper levels may exceed 1,000 ug/l. The level of copper in drinking water increases with the corrosively of the water and the length of time it remains in contact with the plumbing. The seriousness of the effects from copper poising can be expected to increase with increased copper levels or length of exposure. Children under one year of age are more sensitive to copper than adults. Long-term exposure (more than 14 days) to copper in drinking water which is much higher than 1,000 ug/I has been found to cause kidney and liver damage in infants. Other persons who are highly susceptible to copper toxicity include people with liver damage or Wilson's disease. |
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Cryptosporidium parvum is a small parasite, measuring between 4 to 6 microns in size, but as they are flexible they can pass through a 3 micron opening. Cryptosporidium lives on (or just under) the surface of the cells lining the small intestine, reproduces asexually, and oocysts are passed in the feces. Transmission of the infection occurs via the oocysts. Cryptosporidium infections have been traced to the contamination of drinking water with oocysts from agricultural "run-off" (i.e., drainage from pastures). Cryptosporidium can be spread by cattle, deer, elk and other mammals when fecal matter is carried into the water source. Oocysts are present in most surface bodies of water (e.g. lakes and rivers) across the United States, many of which supply public drinking water. Oocysts are more prevalent in surface waters when heavy rains increase runoff of wild and domestic animal wastes from the land or when sewage treatment plants are overloaded or break down. Drinking untreated surface water (such as streams, rivers, and lakes) or swallowing a small amount of water when swimming, even in a chlorinated pool, can cause cryptosporidiosis. The parasite may also be spread in uncooked foods, beverages, or ice prepared with contaminated water. Unwashed fresh fruits or vegetables may carry oocysts if manure was used or animals grazed where the crop was grown. The disease cryptosporidiosis can be caused by ingesting as few as 1 to 10 organisms. Passage through the host stomach weakens the cyst wall allowing 4 spindle shaped motile sporozooites to burst out and infect the intestinal cells and continue their life cycle |
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Symptoms usually develop 4 to 6 days after infection but may appear anytime from 2 to 10 days after infection. There is no cure for this parasite. Healthy adults will fight off the infection in 7 to 19 days. Symptoms of cryptosporidiosis may include:
Cryptosporidiosis is most severe and long-lasting in immunocompromised individuals (whose immune systems are weak). Symptoms may include: debilitating, cholera-like diarrhea (up to 20 liters/day), severe abdominal cramps, malaise, low-grade fever, weight loss, and anorexia. Outbreaks In 1987, 13,000 people in Carrollton, Georgia became ill with cryptosporidiosis. This was the first report of its spread through a municipal water system that met all state and federal drinking water standards. In the spring of 1993 in Milwaukee, Wisconsin, municipal drinking water, again within standards, was contaminated with Cryptosporidium. An estimated 400,000 people became ill and the disease contributed to the deaths of some AIDS patients.In 1993, 400,000 people in Cleveland became infected, 30 died. In 1994 cryptosporidiosis killed 19 people in Las Vegas. Water contaminated with Cryptosporidium parvum can be treated in the following ways:
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Colour Colour in drinking water may be due to the presence of organic substance, metals such as iron, manganese and copper or highly coloured industrial wastes. Although the presence of colour in drinking water is not directly linked to health, experience has shown that consumers may turn to alternative, possibly unsafe, sources when their drinking water contains aesthetically displeasing levels of colour. |
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Cyanide Cyanides are employed in many industrial processes, including chemical manufacturing and metal extraction for low-grade ores, and industrial effluents are the main sources of cyanide contamination of water. Cyanide is an extremely toxic and fast-acting poison. However, because it can be detoxified to a certain extent in the human body, cyanide poisoning generally results from acute exposure to high doses, not from chronic ingestion of low doses. |
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Algae & Cyanobacteria Cyanobacteria is the scientific name for blue-green algae, or "pond scum." Species identified range in colour from olive-green to red. Cyanobacteria form in shallow, warm, slow-moving or still water. A mass of cyanobacteria in a body of water is called a bloom. When this mass rises to the surface of the water, it is known as surface scum or a surface water bloom. Cyanobacterial toxins are the naturally produced poisons stored in the cells of certain species of cyanobacteria. These toxins fall into various categories. Some are known to attack the liver (hepatotoxins) or the nervous system (neurotoxins); others simply irritate the skin. These toxins are usually released into water when the cells rupture or die. Very few cyanobacterial toxins have actually been isolated and characterized to date. Microcystins Microcystins are the most common of the cyanobacterial toxins found in water, as well as being the ones most often responsible for poisoning animals and humans who come into contact with toxic blooms. Microcystins are extremely stable in water because of their chemical structure, which means they can survive in both warm and cold water and can tolerate radical changes in water chemistry, including pH. 50 different kinds of microcystins have been discovered to date. Researchers generally agree that between 30 and 50 per cent of cyanobacterial blooms are harmless because they contain only nontoxic species of freshwater cyanobacteria. Blooms containing even one species of toxic cyanobacteria will be poisonous and potentially dangerous. Because there's no obvious way to tell if a particular bloom is toxic, samples have to be analyzed in a laboratory before a body of water can be declared safe. The earliest reliable account of a cyanobacterial bloom dates back to the 12th century; the toxic effects of cyanobacteria on livestock have been recognized for more than 100 years. Since cyanobacterial bloom formation seems to be linked to nutrient-rich water bodies (for example, water that contains a lot of phosphates from detergents and phosphate fertilizers), the problem is not likely to go away in the near future. If you ingest water, fish or blue-green algal products containing elevated levels of toxins, you may experience headaches, fever, diarrhea, abdominal pain, nausea and vomiting. If you swim in contaminated water, you may get itchy and irritated eyes and skin, as well as other hay fever-like allergic reactions. If you suspect you might have come into contact with cyanobacterial toxins and are experiencing any of these symptoms, rinse any scum off your body and consult your physician immediately. Children are at greater risk than adults of developing serious liver damage should they ingest high levels of microcystins, because of their comparatively lower body weight. How likely am I to drink water contaminated with cyanobacteria and/or its toxins? Not very likely. Relatively few incidents of human poisoning have been reported. People don't usually drink water contaminated with cyanobacteria because of the scum and the accompanying smell (fresh blooms smell like newly mown grass; older blooms smell like rotting garbage). However, people could unknowingly drink water containing cyanobacterial toxins released from blooms that have died naturally. If your water comes from a source that is prone to blue-green algal contamination (dugouts, for example), you should monitor the water for bloom formation. If you detect a bloom in your water supply, contact your local health authorities for advice. |
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Fluoride Fluoride occurs naturally in minerals and soils, and fluorides are widely used by Canadian industry in the manufacture of aluminum, phosphate fertilizers and bricks. The presence of small quantities of fluoride in drinking water may prevent tooth decay. Fluoride is poisonous at high levels, and while dental fluorosis (mottled teeth) is easily recognized, skeletal damage may not be clinically obvious until advanced stages have occurred, and can be misdiagnosed as rheumatoid or osteo arthritis. Often, ground waters will contain more than 1.0 ppm, and in these cases, the water should probably be deflouridated for drinking. Fluoride levels in wells can be as high as 8.0 mg/L. In many countries, including the US and Canada, fluoride is purposely introduced into the drinking water supply in concentrations of approximately 1.0 ppm (milligrams/liter) for the purpose of reducing dental decay. |
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Giardia lamblia Above Right: Giardia lamblia trophozoites, as they appear with the scanning electron microscope. Original image by Arturo Gonzalez, CINVESTAV, Mexico. Giardia lamblia is the most well know parasite found in North American water systems. It is also know as "beaver fever". Giardia is identified under a microscope by the appearance of two eyes that are actually suction cups to attach to the host intestinal lining. Giardia are from 8 to 12 microns in size, but they are flexible and can pass through 5 to 6 micron openings. It can survive routine concentrations of chlorine used to purify community water supplies, and it can live for more than two months in cold water. Giardia is found all over the world. It is most common in the rural and wilderness areas of Western Canada, where there is lots of local wildlife. Giardia can also be found in the waste (bowel movements) of people and some domestic animals, both farm and household pets. The disease Giardiasis can be caused by ingesting as few as 1 to 10 cysts. It is commonly spread by hand-to-mouth transfer of the parasite. As a result, a person can spread it to others while preparing food. It is generally contracted by drinking water than an infected animal has defecated in. Untreated the symptoms may last 3 weeks, but there are cases of chronic infections lasting months to years. Chronic cases, both those with defined immune deficiencies and those without, are difficult to treat. Giardiasis affects the body's ability to absorb fats from the diet. It is estimated that between 1% and 20% of the U.S. population has giardiasis, but in developing countries this figure may be 20% or higher. Young children are three times more likely to have giardiasis than adults; this statistic leads some experts to believe that our bodies gradually develop some form of immunity to the parasite as we grow older. It is not unusual, however, for an entire family to have giardiasis, with some of the family having diarrhea, some just crampy abdominal pains, and some with few or no symptoms.
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Symptoms of Giardiasis may include:
Water contaminated with Giardia lamblia can be treated in the following ways:
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Hardness As water moves through soil and rock, it dissolves very small amounts of minerals and holds them in solution. Calcium and magnesium dissolved in water are the two most common minerals that make water "hard." The degree of hardness becomes greater as the calcium and magnesium content increases. In current practice, total hardness is defined as the sum of the concentration of the calcium and magnesium ions, expressed as calcium carbonate. Hardness can be expressed as calcium carbonate in either parts per million (ppm), the same as milligrams per liter, or grains per gallon (gpg). One grain of hardness equals approximately 17.1 PPM of calcium carbonate hardness. Hard Water Problems
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Iron Iron is the fourth most abundant element in the earth's crust. In Canada, iron ore is used mainly for processing into steel products. Little data is available on the levels of iron in Canadian surface or drinking waters, and it is not known what effect local contamination of surface or ground water has on the concentration of iron in finished waters. Iron is an essential element in human nutrition. Toxic effects have resulted from the ingestion of large quantities of iron, but there is no evidence to indicate that concentrations of iron commonly present in food or drinking water constitute any hazard to human health. Water contaminated with iron may look clear at first, however upon exposure to air, or after the addition of oxidants (such as chlorine bleach or ozone), this ferrous iron is oxidized ("rusted") to the ferric state to form insoluble particles. The water then looks orange or yellow. Iron is frequently found to be complexed or "bound up" with organic matter that are present in water. At concentrations above 0.3 mg/L, iron can stain laundry and plumbing fixtures and cause undesirable tastes. The precipitation of excessive iron imparts an objectionable reddish-brown colour to the water. Iron may also promote the growth of certain microorganisms, leading to the deposition of a slimy coat in piping. |
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Lead Lead is the most common of the heavy elements and is widely distributed throughout the environment. Drinking water can become contaminated with lead from holding tanks, underground pipes, and lead pipes and fixtures in the home. Homes built before 1950 are at particular risk. Lead builds up in the body over many years and can damage the brain, kidneys, and red blood cells. Because of size and charge similarities, lead can be substituted for calcium in bones. Children are especially susceptible to lead as developing skeletal systems require high calcium levels. Lead that is stored in bone is not harmful, but if high levels of calcium are ingested later, the lead in the bone may be replaced by calcium and mobilized. Once free in the system, lead can severely affect the central nervous system. Lead in the drinking water can not be seen, tasted, or smelled. It can only be detected by laboratory testing. Lead has been classified as being possibly carcinogenic to humans. |
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Magnesium Magnesium is an essential element in human metabolism. Magnesium is one of the major contributors to water hardness, and numerous studies have linked magnesium content in drinking water with a decrease in cardiovascular disease. Undesirable effects from the ingestion of magnesium in drinking water may result indirectly from the laxative effect of magnesium in association with the sulfate ion. As well, magnesium may contribute undesirable tastes to drinking water. There is no evidence of adverse health effects specifically attributable to magnesium in drinking water. |
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Manganese Manganese occurs in over 100 common salts and mineral complexes that are widely distributed in rocks, in soils and on the floors of lakes and oceans. Manganese is generally present in natural surface waters at concentrations below 0.05 mg/L. It is more prevalent in groundwater and high concentrations have been found in lakes and reservoirs. Manganese is an essential element in humans and animals. It is regarded as one of the least toxic elements; toxicity in humans is usually the result of chronic inhalation of high concentrations of manganese in dust from industrial sources. At levels exceeding 0.15 mg/L, manganese stains plumbing fixtures and laundry and causes undesirable tastes. Its presence in water may lead to microbial growths in the distribution system. Even at concentrations as low as 0.02 mg/L, manganese will form coatings on piping that may slough off as black precipitates. |
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Mercury Mercury is a toxic element and serves no beneficial physiological function in humans. The presence of mercury in water has become a source of concern because of the finding that organic mercury is bioconcentrated by fish. Elevated mercury levels have been found in all freshwater fish taken from areas with suspected mercury contamination. Mercury poses a great risk to humans, especially in the form of methylmercury. When mercury enters water it is often transformed by microorganisms into the toxic methyl mercury form. Chronic poisoning is usually a result of industrial exposure or a diet consisting of contaminated fish. Chronic poisoning may cause liver damage, neural damage, and teratogenesis. |
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Molybdenum Molybdenum is used in the manufacture of special steels and in the production of tungsten and pigments, and molybdenum compounds are used as lubricant additives and in agriculture to prevent molybdenum deficiency in crops. Molybdenum is considered to be an essential element, with an estimated daily requirement of 0.1–0.3 mg for adults. No data is available on the carcinogenicity of molybdenum by the oral route. |
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Nickel Nickel is used mainly in the production of stainless steel and nickel alloys. Food is the dominant source of nickel exposure in the non-smoking, non-occupationally exposed population; water is generally a minor contributor to the total daily oral intake. Where there is heavy pollution or use of certain types of kettles, of non-resistant material for lining wells or of water that has stood for an extended time in contact with chromium or nickel plated fittings, particularly taps, the nickel contribution from water may be significant. It has been concluded that inhaled nickel compounds are carcinogenic to humans and metallic nickel is possibly carcinogenic. However, there is a lack of evidence of a carcinogenic risk from oral exposure to nickel. |
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Nitrate/Nitrite Many bodies of freshwater are currently experiencing influxes of nitrogen and phosphorus from outside sources. The increasing concentration of available phosphorus allows plants to assimilate more nitrogen before the phosphorus is depleted. Thus, if sufficient phosphorus is available, high concentrations of nitrates will lead to phytoplankton (algae) and macrophyte (aquatic plant) production. The source of nitrate and nitrogen may be from runoff or seepage from fertilized soil, municipal or industrial wastewater, landfills, animal feed lots, septic systems, urban drainage, or decaying plant material. Nitrates are also found in fertilizers and rich soils form farming. When an infant takes in nitrate, it's converted into another compound called nitrite. Nitrite causes the hemoglobin in the blood to change into a substance called methemoglobin. This reduces the ability of the blood to carry oxygen, causing a condition known as methemoglobinemia, or "blue baby syndrome." Medical treatment should be sought immediately for this condition. Prompt medical attention usually results in a quick recovery. In severe cases, nitrate poisoning can be fatal. Nitrate/nitrites have been classified as being possibly carcinogenic to humans. |
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Odour Although odour in drinking water can often be attributed to a specific chemical, it is usually impractical and often impossible to isolate and identify and odour-producing chemical. Separate limits have been established for those substance that commonly cause unpleasant odours and tastes in drinking water. Odour is rarely indicative of the presence of harmful chemical substances. It may, however, indicate an undesirably high level of biological activity in the drinking water source, contamination of the water supply or treatment and distribution inadequacies. Because odour cannot be objectively measured, a guideline has not been specified. The provision is drinking water should have no odour. |
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Toxic
Herbicides & Pesticides
The US EPA defines a pesticide to be any substance that is intended to prevent, destroy, repel, or mitigate any pest. This includes insecticides, herbicides, fungicides, fumigants, and algaecides. Herbicides used to kill vegetation are the most widely used, sampled for, and detected in ground water of all the pesticides. Herbicides account for 75% of the pesticide use in U.S. agriculture. According to a 1994 report issued by the National Wildfire Federation, farmers apply 600 million pounds of pesticides and herbicides annually that eventually end up in the groundwater table. The pesticides most frequently detected in drinking water — the triazines and the acetanilides — cause a litany of health effects, including cancer, birth defects, and disruption of the endocrine (hormone) system. In press statements announcing its regulatory review of the triazines in November, 1994, the EPA cited the possible relationship between triazine exposure and the increased rate of breast cancer in women as a reason for formal review of these weed killers (EPA 1994). The acetanilide herbicides (alachlor, acetochlor, metolachlor) cause a rare nasal turbinate cancer in animals. Infants may be at higher risk when they are exposed to alachlor in formula and juice made with contaminated tap water. Two of the acetanilide herbicides, alachlor and the recently registered acetochlor, are classified by EPA as probable human carcinogens. Drinking Water Standards Do Not Adequately Protect Public Health Under the Safe Drinking Water Act, EPA sets enforceable standards for allowable levels of pesticides in drinking water, and requires water utilities to monitor for these contaminants. Standards are set as a two part process. First, the EPA sets a non-enforceable Maximum Contaminant Level Goal (MCLG), based purely on health considerations. These MCLGs are set at levels "at which no known or anticipated adverse effects on the health of persons occur, and which allows an adequate margin of safety." The agency then sets enforceable standards, known as Maximum Contaminant Levels (MCLs), which are based upon the MCLGs, but are usually adjusted to ensure that they are technically and financially feasible. For a number of reasons, standards for the herbicides commonly found in drinking water -- atrazine, cyanazine, acetochlor, alachlor, and metolachlor -- fail to adequately protect public health. Drinking water standards allow excessive cancer risksBecause of an outdated methodology used to set drinking water standards for these chemicals, they allow 10 to 30 times greater cancer risks than EPA's Office of Pesticides allows for the same pesticides in food. Thus, even when pesticide contamination levels are within EPA's drinking water standards, they may still pose cancer risks that exceed the federal governments "negligible" (See Note 1.) risk standard by a factor of 10 or more. Standards do not take the risk of exposure to multiple pesticides or pesticide metabolites into account Water supplies are often contaminated by multiple pesticides, and studies show that a single glass from the tap can contain up to nine pesticides or metabolites. In the case of the triazine herbicides -- which, according to EPA all act by the same toxicological mechanism -- multiple exposures can significantly increase health risks. Unfortunately, the standard setting process makes the unrealistic assumption that we are always exposed to pesticides in isolation, never more than one at a time. Standards fail to protect children After a five-year study, the National Academy of Sciences concluded in 1993 that because of differences in physiology children are usually at greater risk from pesticides than adults. On top of this, they are exposed to higher amounts of pesticides relative to their size. For example, infants drink more than twice as much water per unit of body weight than adults, meaning that they receive more than twice the exposure to toxic agents in drinking water. Since the release of the NAS study, no drinking water standard has been set or adjusted specifically to protect infants or young children. Notes1. Contaminated water supplies, are referred to as those with nitrate concentrations detected above 3 parts per million (ppm). |
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pH pH is a measure of the intensity of the acidity or alkalinity of water on a scale from 0 to 14, with 7 being neutral. One of the main objectives in controlling pH is to produce water that minimizes corrosion or incrustation. These processes, which can cause considerable damage to the water supply systems, result form complex interactions between pH and other parameters, such as dissolved solids, dissolved gasses, hardness, alkalinity, and temperature. There is also a progressive decrease in the efficiency of chlorine disinfection processes with increasing pH levels. |
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Selenium Selenium appears to be an essential element in human nutrition. Ingestion of large amounts of selenium have been correlated with a variety of clinical disorders in humans, including jaundice, chronic gastrointestinal disease, and dermatitis. Available data provide no conclusive evidence that selenium is carcinogenic in humans; in fact, selenium may have may have anit-carcinogenic properties. |
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Silver Silver is a nonessential element and normally occurs in human tissues in only trace amounts. In Canada, photography and coin production are the major uses of silver. Drinking water contributes negligibly to a person's intake of silver, except when silver is used as an anti-microbial agent in water treatment devices. Ingestion of very large doses of silver has been associated with a number of sever acute effects in human, including argyria, a conditions characterized by a blue-grey discolouration of the skin and death. However, daily intake of silver from food and water is considerably below the level at which adverse health effects would occur. |
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Sodium Sodium is the most abundant cation in the extracellular fluid. Because the body has very effective methods to control levels of sodium, it is not an acutely toxic element with normal doses. The average intake of sodium from water is only a small fraction of the consumed in a normal diet (about 5 g/d). However, persons suffering form hypertension or congestive heart failure may require a sodium-restricted diet, in which case the intake of sodium from drinking water could become significant. An excessive level of sodium in drinking water is easily detected by taste. |
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Sulphate Sulphates occur naturally in numerous minerals and are used in the manufacture of chemicals, dyes and fertilizers, in the mining and pulping industries, in sewage treatment and in wood preservation. The sodium sulphate industry, based in southern Saskatchewan and Alberta is the primary sulphate-producing activity in Canada. Sulphates are discharge into the aquatic environment in wastes from industries that use sulphates and sulphuric acid (eg. mining, smelting, pulp and paper mills): atmospheric sulphur dioxide may also contribute to the sulphate content of surface waters. A wide range of sulphate concentrations has been found in Canadian municipal water supplies. Sulphat is one of the least toxic anions. The major physiological effects resulting from ingesting large quantities of sulphate are catharsis and gastrointestinal irritation. These effects are enhanced when sulphate is consumed in combination with magnesium. |
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Sulphide (as hydrogen sulphide) Sulphides occur naturally in mineral ores, oil and coal deposits and are generated through anaerobic decomposition of sewage, algae, naturally deposited organic matter and the sulphur found in fertilizers. Sulphides are also present in industrial wastes form petroleum plants, gas works, paper mills, heavy water plants and tanneries. Although data on sulphide concentrations in drinking water have not been found, levels will usually be low. The low amounts of sulphide likely to be found in drinking water are not expected to produce toxic effects. Although the acute toxicity of inhaled hydrogen sulphide is well documented, no reports of toxic effects due to hydrogen sulphide present in drinking water have been found. |
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Tannins Tannins are formed upon the decomposition of vegetation. These compounds are large molecular weight organics that fall under two large primary categories: Humic acids and Fulvic acids. The structure of the tannin varies, depending on the plant life in a given area. Tannins can cause a yellow to brown cast in water and may also impart a taste and odor. They will generally be found in surface water supplies or shallow wells. Although these compounds are not a health risk, they are aesthetically displeasing. |
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Total Coliforms in Drinking Water - US regulations
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Total dissolved solids (TDS) The term total dissolved solids refers mainly to the inorganic substances that are dissolved in water. The effects of TDS on drinking water quality depend on the levels of its individual components; excessive hardness, taste, mineral depositions and corrosion are common properties of highly mineralized water. |
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Trihalomethanes (THMs) THMs are compounds formed when chlorine reacts with organic matter found in water. The THMs most commonly present in drinking water are:
Chloroform is the THM detected most frequently and at highest concentration in drinking water. Chlorine and THM’s have been linked to asthma, cancer, skin disorders, and other health problems. Chlorine is introduced into the body by drinking tap water, absorption through the skin when bathing, and inhalation of chlorine that comes out of the water when taking a shower. Available data is consistent with the hypothesis that ingestion of chlorinated drinking water, if not the THMs specifically, may be causally related to cancers of the bladder and colon. Chloroform and other THMs account for up to 50% by weight of the total chlorination by-produts in drinking water. Chloroform has been found to be carcinogenic in two animal species, and has been classified as being probably carcinogenic to humans.
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Turbidity Turbidity is suspended biological, inorganic and organic particles in water which may be in sufficient amount to make the water seem cloudy. Turbidity is a unit of measurement of the degree to which light traveling through a water column is scattered by the suspended organic (including algae) and inorganic particles. Turbidity is commonly measured in Nephelometric Turbidity Units (NTU). Some of the more common causes of turbidity in water are:
Excessive turbidity detracts from the appearance of drinking water and is often associated with unacceptable tastes and odours. Turbidity can serve as a source of nutrients for waterborne bacteria, viruses and protozoa, which can be embedded in or adhere to particles in water.
Turbidity can interfere with disinfection methods, ultraviolet light in particular. Viable coilform bacteria have been detected in water with turbidities higher than 3 NTU, even in the presence of free chlorine residuals. Outbreaks of disease traced to chlorinated water supplies have been associated with high turbidity. The occurrence and persistence of microorganisms within distribution systems have been correlated with turbidity and other factors. Surface water sources in particular may be susceptible to organic substances and undesired organisms that can impede disinfection or otherwise cause drinking water quality problems. |
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Uranium Uranium is a naturally occurring element. Uranium is used primarily as fuel in nuclear energy plants. It may enter drinking water from naturally occurring deposits or as a result of human activity, such as mill tailings and phosphate fertilizers. Nephritis is the primary chemically induced effect of uranium in animals and humans. Although the potential exists for radiological toxicity of orally administered natural uranium, this has not been observed in animals or humans. Available data is inadequate to classify uranium with respect to it potential carcinogenicity. Note: Data on chemical, not radiological, toxicity are considered here. |
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Viruses Some viruses infect the gastrointestinal tract of humans and animals, and are excreted in feces. If the feces enters a surface water system, there is potential for the spread of waterborne disease. Viruses are a group of infectious agents ranging from 10 to 25 nanometers (nm) in diameter. Distribution of viruses
Sewered communities may not have enough capacity to treat the extremely large volume of water resulting from large rainfalls. Periodically, treatment facilities may need to bypass treatment of their wastewater. In this case, water containing viruses is discharged directly into the surface water body. Estuaries may be particularly susceptible to viral contamination from offshore sewage sludge dumping and offshore sewage pipe outfalls. The Viability of a virus is maintained when high levels of suspended sediment in water provides substrates to which the viruses can adsorb. Absorbed viruses may remain nearly 100% viable. |
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Viruses of particular concern in water are hepatitis A, Norwalk-type viruses, rotaviruses, adenoviruses, enteroviruses, and reoviruses.
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Zinc Zinc is an essential element for human nutrition. Intake of zinc from food is more than sufficient to satisfy the recommended daily requirement of 4 to 10 mg. Drinking water is not regarded as an important nutritional source of zinc. Long term ingestion of zinc in quantities considerably in excess of the daily requirements has not resulted in adverse effects. The occurrence of chronic zinc toxicity is extremely unlikely. Surface waters seldom contain zinc at concentrations above 0.1 mg/L, however levels in tap water can be considerably higher because of the use of zinc in plumbing materials. Water containing zinc at concentrations in excess of 5.0 mg/L has an astringent tastes and may be opalescent and develop a greasy film on boiling. |