Article - Water Quality 101

Article:

Water Quality Problems: Health and Household

Dale Dorman, MS
Extension Housing & Environment Specialist
Department of Housing and Consumer Economics

When you fill a glass with water from your tap, you expect to drink water that is pure and safe. But how safe is it?

Water contains impurities from natural and man-made sources, such as minerals, gases, bacteria, metals and chemicals. Many of these impurities are harmless. However, some impurities can adversely affect your health. Others can damage equipment, stain laundry and fixtures and emit odors.

To protect the public health and ensure uniform standards for water quality nationwide, Congress passed the Safe Drinking Water Act of 1974. This act and its amendments authorized the U.S. Environmental Protection Agency (EPA) to establish limits on the concentration of certain contaminants in public water supplies (systems serving more than 25 people or 15 year-round connections). Private water supplies, including wells, are not regulated by drinking water standards. The owner must test and treat the water as needed to avoid health risks.

Drinking Water Standards

The EPA standards for drinking water fall into two categories – Primary Standards and Secondary Standards.

Primary Drinking Water Standards regulate contaminants that affect the safety of drinking water and may cause health problems. These standards are enforced by EPA. They protect you from three classes of toxic pollutants: microbial pathogens, radioactive elements and organic/inorganic chemicals. Many of these contaminants occur naturally in trace amounts in ground or surface water. Primary Standards set a limit, called the Maximum Contaminant Level (MCL) on the highest amount of a specific contaminant allowed in the drinking water supplied by a public water system. The MCL is usually expressed in milligrams per liter (mg/L). See Chart I for Primary Drinking water standards including organic/inorganic chemicals, radioactive elements and microbial pathogens.

Secondary Drinking Water Standards regulate contaminants that affect the aesthetic qualities of drinking water such as taste, odor, color and appearance. The concentration limit is called the Secondary Maximum Contaminant Level (SMCL). SMCLs are established for chloride, color, copper, corrosivity, foaming agents, iron, manganese, odor, pH, sulfates, total dissolved solids and zinc. Secondary Standards are not enforced; water systems are not required to test for and remove secondary contaminants. Secondary levels represent reasonable goals and serve as useful guidelines for water suppliers who wish to ensure that their water is suitable for all household uses. See Chart II for Secondary Drinking water standards including inorganic chemicals and physical problems.

Setting Standards

EPA regulations develop Primary Standards for drinking water based on three criteria:

The contaminant causes adverse health effects.
It is detectable in drinking water.
It is known to occur in drinking water.

In setting Primary Standards for a drinking water contaminant, research scientists first look at all the toxicological data on that water contaminant. This data is usually the result of studies that have been conducted on animals. Occasionally human clinical or epidemiological data are also available. Scientists use this information to estimate the concentration of a drinking water contaminant that may be toxic and the concentrations, if any, that may cause no adverse effects.

The levels of contaminants found in drinking water are seldom high enough to cause acute health effects – effects that occur almost immediately after exposure to a large dose of a substance. Therefore, scientists are most concerned about chronic health effects such as cancer, birth defects, miscarriages, nervous system disorders and organ damage. These health effects may occur after prolonged exposure to small amounts of a substance. When scientists set drinking water standards, they treat contaminants that cause cancer (carcinogens) differently from contaminants that cause other health effects.

Non-Cancer Causing Contaminants

For non-cancer causing toxic substances, scientists set standards using a figure calculated from animal studies called the reference dose. The reference dose is the amount of a substance that a person can consume daily, over a lifetime, without suffering any adverse health effects. It includes a conservative margin. The reference dose used to be called acceptable daily intake.

EPA regulators use the reference dose to establish a Maximum Contaminant Level Goal (MCLG) for a water contaminant. The MCLG is the concentration of a contaminant that experts believe a person can consume safely over a lifetime. It is based entirely on health considerations and is set at a level where no adverse health effects should occur. The MCLG is not enforced by the EPA. It is the goal used to set enforceable drinking water standards.

The Maximum Contaminant Level (MCL) is the enforceable Primary Drinking water Standard. It is set as close as possible to the MCLG. In setting an MCL, EPA regulators consider, in addition to health effects, the feasibility and the combined cost of analyzing water for a contaminant and for treating water to remove the contaminant. Therefore, the MCL is often less stringent than the MCLG.

Cancer Causing Contaminants

In setting Primary Standards for substances believed to cause cancer, research scientists assume that no concentration is safe. Consequently, the MCLG is set at zero. But a zero level is not always possible to achieve, so regulators estimate toxicity by calculating a figure called a risk estimate.

In theory, any concentration of a carcinogen in your drinking water may possibly cause cancer. In practice, however, at very low concentrations the risk of cancer becomes so small that it is considered negligible. Therefore, scientists must decide what level of risk is acceptable. It may be one excess cancer in 10,000 persons or one excess cancer in 1 million persons exposed over a lifetime (70 years). The concentration of the substance estimated to cause this acceptable level of risks is the risk estimate. Based on the risk estimate, EPA regulators establish the MCLs for cancer-causing contaminants.

Setting drinking water standards is an imperfect process. Data relating human health effects to contaminants in drinking water are limited, and scientists have difficulty predicting the effects of drinking small amounts of a substance for many years. In addition, regulatory decisions frequently incorporate economic, political and social considerations.

Although current drinking water standards do not guarantee that the glass of water you draw from your tap will be absolutely safe and pure, they do reflect sound scientific judgment. Standards are based on all available knowledge.

Federal, State and Local Responsibilities

Under the Safe Drinking Water Act, the primary role of the federal government is to develop national drinking water regulations that will protect public health and welfare. The states have the responsibility for monitoring public water systems and enforcing drinking water standards for EPA - regulated contaminants and other contaminants. The local public water systems are responsible for treating and testing drinking water to ensure that water quality consistently meets the standards set by the regulation.

When levels go above a standard, the EPA requires that the water contaminant levels be reduced to the Maximum Contaminant Level. The corrective treatment is left to the public water system. In addition, Federal law requires that the water system must notify the public when a drinking water standard has been violated. Public notification must include clear explanations of the violations; information on potential adverse health effects; the steps being taken to correct the problem; and the need, if any, to seek alternative water supplies. This procedure is a safety precaution intended to keep the public informed and call attention to deficiencies in the drinking water supply.

Consumer Rights

Under the Safe Drinking Water Act Amendment of 1986, consumers have the right to obtain the following information about their drinking water:

its source,
where it is purified,
the contaminants for which it has been tested,
past and present contamination problems,
contamination levels that violate current federal drinking water standards, and
how the public was notified about the violations.

Protection under the Safe drinking water Act of 1974 includes:

the right to bring civil suits against the local water system, the state, or federal officials if they fail to do their jobs;
the requirement of public water systems to chemically treat contaminated water or install clean-up equipment to remove the contaminant(s) to concentrations below the standard when a violation occurs;
the requirement for public notification of maximum contaminant level violations within 14 days of their detection and at least once every three months if the contamination continues. For minor violations of standards, public notification must be made once a year.

Chart I

Primary Drinking Water Standards – Regulated

Organics

Contaminant	Source	Possible chronic health effects	MCL
Acrylamide*	drinking water treatment residue; well drilling; food production and processing; paper making and textile manufacturing.	cancer and nervous system effects.	MCL: 0.05% dosed at 1 mg/L
Alachlor* (Lasso)	agricultural herbicide	cancer; damage to eyes and liver	MCL: 0.002 mg/L
Aldicarb* (Temik)	agricultural insecticide	cholinesterase inhibition.	MCL: 0.003 mg/L
Aldicarb sulfoxide*	agricultural insecticide	cholinesterase inhibition.	MCL: 0.004 mg/L
Aldicarb sulfone*	agricultural insecticide	cholinesterase inhibition.	MCL: 0.002 mg/L
Benzene	leaking underground fuel storage tanks; industrial wastes; manufacture of pesticides, detergents and solvents.	leukemia and other cancers; nerve, lung, and kidney damage; blood disorders and reproductive effects.	MCL: 0.005 mg/L
Carbofuran* (Furadan 4F)	agricultural insecticide	cholinesterase inhibition; reproductive and immune system effects.	MCL: 0.04 mg/L
Carbon Tetrachloride	chemical disposal sites, contaminated soils, and landfills; aerosol sprays, cleaning agents and coolants; laundry and dry-cleaning operations.	cancer; central nervous system depression; liver and kidney damage.	MCL: 0.005 mg/L
Chlordane*	insecticide; hazardous waste sites	cancer; nerve and liver effects.	MCL: 0.002 mg/L
2,4-D* (Formula 40, Weedar 64)	agricultural herbicide and aquatic weeds control.	liver and kidney damage; skin irritations and muscle effects.	MCL: 0.07 mg/L
Dibromochloropropane* (DBCP, Wemafume)	soil fumigant.	cancer, kidney and liver damage; infertility.	MCL:0.0002 mg/L
p-Dichlorobenzene	dye and pesticide manufacturing.	liver and kidney damage; blood disorders.	MCL: 0.075 mg/L
1,2-Dichloroethane	vinyl manufacturing; drycleaning solvent, metal degreasers, and adhesives; gasoline additive.	cancer; central nervous system depression; kidney and liver damage; lung and heart damage.	MCL: 0.005 mg/L
1,1-Dichloroethylene	industrial solvent, cleaning and degreasing agent.	central nervous system depression; liver, kidney and heart damage.	MCL: 0.007 mg/L
trans-1,2-Dichloroethylene*	transformed from other chlorinated hydrocarbons in drinking water supplies; industrial cleaning and degreasing agents.	liver and kidney damage.	MCL: 0.1 mg/L
cis-1,2-Dichloroethylene*	transformed from other chlorinated hydrocarbons in drinking water supplies; industrial cleaning and degreasing agents.	liver and kidney damage.	MCL: 0.07 mg/L
1,2-Dichloropropane*	industrial solvent and cleaning agents; dry cleaning fluid components, soil fumigants.	liver and kidney damage.	MCL: 0.005mg/L
Endrin	insecticide and rodenticide.	liver and nervous system effects; birth defects.	MCL: 0.0002mg/L
Epichlorohydrin*	resin and rubber product manufacturing; contamination of materials used to process food and treat or store drinking water.	cancer; central nervous system, lung, liver and kidney effects; damage to male reproductive organ.	MCL: 0.01% dosed at 20 mg/L
Ethyl benzene*	hazardous waste sites and styrene production.	nerve, brain, liver and kidney effects.	MCL: 0.7 mg/L
Ethylene dibromide*	pesticide and soil fumigants; leaded gasoline additives.	nerve, brain, kidney, nervous system, gastrointestinal, and reproductive effects.	MCL: 0.00005 mg/L
Heptachlor expoxide*	insecticide and hazardous waste sites.	cancer, liver damage and central nervous system effects.	MCL: 0.0002 mg/L
Heptachlor* (H-34, Heptox)	insecticide and hazardous waste sites.	cancer, liver damage and central nervous system effects.	MCL: 0.0004 mg/L
Lindane*	pesticides.	liver and kidney damage.	MCL: 0.002 mg/L
Methoxychlor*	insecticides.	nervous system, kidney, and liver effects.	MCL: 0.04 mg/L
Pentachlorophenol* (PCP)	herbicides and insecticides; water contact with PCP-treated wood; industrial waste sites.	liver and kidney damage; nervous system, immune system, and reproductive effects; blood disorders.	MCL: 0.001 mg/L
Polychlorinated biphenyls* (PCBs, Aroclor)	hazardous waste sites; disposal and manufacture of electrical transformers, electromagnets, fluorescent lights and plastic	cancer; liver damage.	MCL: 0.0005 mg/L
Styrene*	manufacture of plastics, synthetic rubbers, resins and insulators.	liver damage.	MCL: 0.1 mg/L
Tetrachloroethylene*	industrial metal, textile and dry-cleaning solvent.	cancer; liver and kidney damage; central nervous system depression.	MCL: 0.005 mg/L
Toluene*	paint, oil, resin manufacturing; leaking fuel storage tanks; jet fuel.	central nervous system depression; kidney damage.	MCL: 1 mg/L
Toxaphene*	insecticides.	cancer, liver and kidney damage.	MCL: 0.003 mg/L
2,4,5-TP* (Silvex)	herbicides.	liver and kidney damage.	MCL: 0.05 mg/L
1,1,1-Trichloroethane	hazardous waste sites; industrial solvent and degreasers; drycleaning solvents.	central nervous system depression; liver and cardiovascular damage.	MCL: 0.20 mg/L
Trichloroethylene (TCE)	hazardous waste sites, drycleaning solvent; manufacturing of chemicals and drugs.	cancer, nervous system depression and heart effects; liver and kidney damage.	MCL: 0.005 mg/L
Total Trihalomethanes	formed when residual chlorine in treated drinking water combines with naturally occurring organic matter.	cancer; heart, lung, kidney and liver damage.	MCL: 0.100 mg/L MCLG: -
Vinyl Chloride	manufacturing of plastics and synthetic rubber; corrosion of plastic pipes and soldering.	cancer; central nervous system depression; liver, reproductive, and digestive tract effects; birth defects.	MCL: 0.002 mg/L
Xylene*	leaking underground fuel storage tanks; manufacturing of chemicals and drugs.	nervous system and reproductive effects.	MCL: 10 mg/L