WQ-5 Interpreting Water Test Reports (2024)

WQ-5

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Introduction

When a water sample is tested the testing lab provides areport listing the concentration of materials found in the sample.Since little or no water in nature is chemically pure, most reportswill indicate the presence of some natural occurring compounds such ascalcium, magnesium, carbonates and chlorides. Federal and stateagencies have established guidelines to indicate those levels ofcontaminants - both naturally occurring and introduced pollutants -considered safe. They also have established levels above which apossible health risk for different uses may occur.

Chemists divide materials into two classes: organic andinorganic. The term organic refers to materials which contain carbon.Examples of organic compounds would include petroleum fuels, solvents,paint thinners and pesticides. Inorganic compounds are not derivedfrom living sources, and in general don't contain carbon. Inorganicsinclude lead, nitrate and chloride. Three exceptions to these generalrules are carbonates, a compound found in essentially all Indianaground water, carbide and cyanide. These three are consideredinorganic even though they do contain carbon.

This bulletin addresses the interpretation of water testreports for inorganic compounds commonly found in Indiana's watersupplies. The bulletin also outlines the potential health risks whenacceptable levels are exceeded.

Health Effects

Federal and state agencies review short- and long-term animalexposure studies before labeling a material as hazardous. The studiesare used to determine the level of exposure at which acute or chronichealth problems may occur.

Acute problems are those which arise quickly and may include nausea,skin rash, dizziness or death. An example would be a farmer whobecomes dizzy and nauseous after spilling a pesticide. Bacteria andviruses may also cause acute illness.

More common than acute effects and more difficult to detect,chronic problems result from long-term exposure to very small amountsof a contaminant. Chronic problems include cancer (carcinogenic),birth defects (teratogenic), organ damage and nervous systemdisorders. In general, if a material enhances the risk of cancer,special notice is given.

Under the Safe Drinking Water Act, the EnvironmentalProtection Agency (EPA) has set limits for the concentration levels ofcertain contaminants found in drinking water. Most of the substancesregulated by the EPA occur naturally in the environment and the foodyou eat. These levels are set for public drinking water suppliesonly. However, the levels serve as guidelines for private watersupplies.

EPA Standards

The EPA sets an Acceptable Daily Intake (ADI) level for alltoxic materials. The ADI is the daily intake of a material a personcan consume through food and water and not suffer adverse healtheffects, either acute or chronic. The ADI is an adjusted value. Theminimum concentration, detertmined by research, to cause a healthproblem is further adjusted downward by a safety factor. The safetyfactor takes into account the uncertainties of applying research testresults to humans and ensures that complying with the ADI levels willnot result in any health problems.

The Maximum Contaminant Level Goal (MCLG) is the maximum levelof a particular material a person should consume safely over alifetime with no adverse health effects. The EPA does not enforce theMCLG. The ADI level, after adjustment for exposure only throughdrinking water, serves as the base for the MCLG.

The EPA uses the MCLG to set the Maximum Contaminant Level(MCL). The MCL is the maximum level of a material the EPA and stateagencies allow in public drinking water supplies. When setting theMCL, regulators consider health risks, the cost of analysis andtreatment limits. Because of these considerations, MCLs tend to beless strict (higher concentrations) than MCLGs.

A material considered a carcinogen or a teratogen has a MCLGof zero. However, a zero level is difficult to achieve and tomonitor. Therefore, enforceable limits are set using a mathematicalprocedure to calculate a Risk Estimate. The risk estimate is based onthe possibility that exposure, at some level, will cause oneadditional cancer per 100,000 or one million people over a lifetime of70 years. EPA generally sets an acceptable (negligible) risk level atone in a million.

The difference between the ADI (Acceptable Daily Intake)method and the risk estimate method is that the ADI method assumes asafe minimum level (threshold value) exists for the compound. A riskestimate can be made for materials that cause some problem wheneverthe compound is found. The risk estimate is used to establish theMaximum Contaminant Level (MCL) in drinking water supplies. Thusdrinking water standards are set up to minimize risk from using thatresource. Figure 1 shows how the EPA levels are related.

Figure 1. EPA Standard Setting Process

Concentration

(units used to report concentration in the sample)

In general, contaminant concentrations are reported in eithermilligrams per liter (mg/l) which equals parts per million (ppm) ormicrograms per liter (ug/l) which equals parts per billion (ppb) (seeTable 1). In both cases the numbers are small and represent theproportion of the contaminant in a million or billion parts of water.For example, to get a one ppb metal concentration you would dissolveone ounce of the metal into 1,000,000,000 ounces or 7,800,000 gallonsof water. To arrive at ppm you would need to dissolve one ounce in1,000,000 ounces or 7,800 gallons of water.

Hardness of water may be reported as grains per gallon (gpg).Hardness as gpg can be converted to ppm using the following equation:

Inorganic Chemicals

(acceptable limits in brackets)

pH

pH indicates the acidity or alkalinity of water. An acidic pH,less than 6.5, causes metals to corrode and dissolve from pipes,fixtures or pumps. A pH of less than 4.5 indicates some type ofmineral acid, such as from mine drainage, in the water. A basic pH,over 8.5, makes water feel slippery, leaves scaly deposits or causeswater to have a soda taste.

Distilled water left in an open container to equilibriate withthe air will have a pH of 5.5 to 5.7 due to carbon dioxide. Dissolvedcalcium and magnesium cause most ground water in Indiana to have a pHof 6.5 to 7.5.

Hardness

Hard water contains calcium and magnesium salts. Hardness ofIndiana ground water is generally between 20 to 400 ppm. Hardnessdoes not impart a negative health effect. However, when water isheated calcium and magnesium salts fall out of solution and form scaleon pans and in plumbing, coffee pots and water heaters. Hard wateralso requires extra soap in the laundry and makes glasses spot in thedishwasher. Typical ranges for water hardness are given in Table 2.

The general recommendation is water with hardness greater than180 ppm should be conditioned with a water softener. Most softenersexchange calcium and magnesium for sodium, but they are designed onlyto remove hardness, not other chemicals.

Chloride

Ground water supplies in Indiana typically have between 10.0 to50.0 ppm chloride. Chlorides in water are generally not considered ahealth problem. At levels greater than 500.0 ppm, chlorides makewater taste salty. At these levels, there can be acceleratedcorrosion of water heaters and plumbing fixtures. Very high levelsmay indicate some type of contamination typically from deicing salts,human sewage or animal manures, or industrial sources.

Sulfate

In Indiana, ground water can contain between 0.0 and 1,000.0 ppmsulfate. Sulfates of calcium and magnesium can cause hardness inwater. Sulfate levels at 500.0 ppm or greater can have a laxativeeffect and cause an astringent aftertaste to the water. High sulfatelevels can also have a corrosive effect on plumbing.

Water containing sulfate may also contain bacteria which producehydrogen sulfide. The foul, rotten egg smell found in some watercomes from hydrogen sulfide. Hydrogen sulfide is a poisonous gas butat levels dissolved in water, is not a health hazard. However,dissolved hydrogen sulfide causes silver and aluminum utensils totarnish. Hydrogen sulfide is best detected with the nose (0.05 ppm isdetectable) as it readily vaporizes from standing water.

Iron and Manganese

Iron originates in soils and rocks, occurs naturally in water andis needed in human and animal diets. Iron in Indiana ground waterspans a typical range from 0.1 to 3.0 ppm. At high concentrations(more than 0.3 ppm) iron will discolor (reddish-orange; brown-black)household fixtures, laundry and give an objectionable taste and odorto water. However, even at concentrations far over 0.3 ppm fewadverse health effects have been reported. Bacteria which feed oniron can create an objectionable odor in the water and discharge aclear, oil-like slime, typically noticed in toilet tanks.

Manganese ranges from 0.02 to 1.0 ppm in Indiana ground water.At levels greater than 0.05 ppm manganese tends to fall out ofsolution and form black flakes. These flakes will deposit themselvesin the same way iron stains and can clog pipes.

Fluoride

The range for fluoride in Indiana ground water is typically 0.1to 1.5 ppm. At very high levels fluoride is toxic to humans. Watersupplies seldom reach these levels. At levels between 0.7 and 1.2ppm, fluoride will prevent tooth decay and is essential to properdevelopment of bones and teeth. At levels greater than 4.0 ppm,fluoride may cause dental problems, including brownish discoloration.At levels greater than 6 ppm, skeletal problems may occur.

Other Metals

Besides calcium, magnesium, iron and manganese, water can containmany other metals (Table 3). These metals enter water as it movesthrough the ground, which contains naturally occurring metals. Whilehigh levels of metals in ground water may arise naturally, the sourceis more likely from human contamination. Potential sources of metalsin water include but are not limited to: improperly applied sludge,industrial processing facilities, poorly constructed landfills andchemical spills.

The EPA sets primary MCLs to guard against adverse healtheffects. Secondary standards are set for some metals. Secondarystandards serve as a guideline for taste, odor, color or otheraesthetic aspects which do not present a health risk.

The health effects of long- or short-term exposure to these metalsvaries. In general, long-term exposure to low levels or short-termexposure to high levels results in damage to the kidneys or liver.The exceptions are lead and mercury which can impact the centralnervous system as well as other organs. The amount of metal that mustbe ingested to achieve an effect varies widely. If your water testreport shows high levels of a metal(s) discuss the health effects witha health professional. You should consider using an another source ofdrinking water or an appropriate water treatment device. You alsoneed to locate the possible cause of contamination.

Nitrate

Nitrate, an anion (negative charge), is not adsorbed by soil andmoves with infiltrating water. Of the inorganic contaminants found inwater, nitrate receives the most attention. This is due to the factnitrate is easy to detect and many natural sources are present in theenvironment.

A large amount of confusion exists over the way nitrate data ispresented. Table 4 gives the conversion factors for the commonmethods used. You should note the nitrogen value used in the testreport for your well water. For example a reading of nitrate (NO3) at44.0 ppm is equivalent to 10.0 ppm nitrogen (NO3-N). NO3-N refers tonitrate by the amount of nitrogen present.

While natural nitrate originating from soil occurs in water, (0.2to 0.3 ppm NO3-N), high levels of nitrate in well water, likechloride, indicate surface contamination. These sources include:septic fields, manure pits and lagoons, and fertilizer and sludgeapplication.

If the water contains more than 10.0 ppm NO3-N it may causeinfant cyanosis (blue-baby) in children under the age of six months.The cyanosis can be fatal to both infants and small animals. Thewater should not be given to infants either directly or used informulas. It is also recommended that children and adults shouldavoid long-term consumption of water with over 10.0 ppm NO3-N.

Other Considerations

Your water test report may show levels of other inorganicmaterials within the acceptable limits. Although this may mean thewater is safe for drinking, there may be unwanted odor, taste orcolor. Most of these problems can be corrected with a water treatmentsystem. Refer to the WQ bulletin on water treatment systems andconsult with a commercial distributor to select a water treatmentsystem for your home.

Water can also become contaminated with organic chemicals, eithernaturally or from human activities. If your water test report listscontamination from an organic chemical, refer to WQ bulletin"Interpreting Water Test Reports Part Two: Organic Materials".

For Further Information:

For further information on water testing or possiblecontamination suspected in your area, contact your local HealthDepartment or county Cooperative Extension office. The followingbulletins in the WQ series may also be helpful:

WQ Bulletin "Interpreting Water Test Reports Part Two: Organic Materials"
WQ 6 "Buying Home Water Treatment Equipment"

Other Sources of Information:

"Is Your Drinking Water Safe?" EPA 570/9-89-005. Office of Water(WH-550). United States Environmental Protection Agency.

EPA Safe Drinking Water Hotline: 800/426-4791

Report unknown contamination or objectionable taste, odor or color ina private well to: Indiana Department of Environmental Management(IDEM) Ground Water section 317/240-6216

This material is based upon work supported by the U.S. Department ofa*griculture ture, Extension Service, under special project number89-EWQI-1-9202.

Cooperative Extension work in Agriculture and Home Economics, state ofIndiana, Purdue University, and U.S. Department of Agriculturecooperating; H. A. Wadsworth, Director, West Lafayette, IN. Issued infurtherance of the acts of May 8 and June 30, 1914. The CooperativeExtension Service of Purdue University is an affirmative action/equalopportunity institution.