Water Safety

The following is a basic overview of pollutants, drinking water, and impacts on health. This is meant to be more of a basic primer on the types of pollutants out there. It is just a starting point on basic water pollutants and health concerns. We believe this to be especially helpful to those of you who may be visiting the site for the first time, or are still relatively new to the issue of military contamination.

Organic Pollutants and Health Problems

Organic pollutants in drinking water seldom exceed trace concentrations: a few parts per billion (ppb) or even a few parts per trillion (ppt). These levels can be likened to 1 teaspoon of liquid creamer in 1,321,000 gallons of coffee (1 ppb) or in 1,321,000,000 gallons (1 ppt). Determining the health effect of pollutants present at such low levels is extremely difficult.

Toxicity is the inherent ability to impair health. Toxic substances can cause cancer, birth defects, and other illnesses. The severity of the effect usually depends on the dose, defined as the weight of the contaminant consumed per day divided by body weight. Dosages are usually measured in milligrams per kilogram of body weight per day. Acute toxicity refers to a contaminant’s ability to cause immediately detectable health problems. Chronic toxicity refers to a contaminant’s ability to cause health problems years after a long-term exposure. Keep in mind that some contaminants that cause no detectable health problems at low doses can cause death at high doses.

Nonlethal acute toxicity is easier to diagnose and treat than chronic toxicity since the ensuing health problems are generally brief and reversible. When the exposure to the chemical ceases, so do the effects, provided that the dosage has not been too high. Examples of organic chemicals that can be acutely toxic are the polychlorinated and polybrominated biphenyls (PCBs and PBBs)—a group of chemicals used in paints, electrical transformers, insulators, and the pesticides aldicarb, paraquat, and DDT. Symptoms of acute toxicity can include diarrhea, nausea, convulsions, blurred vision, and difficulty in breathing.

Health problems from chronic toxicity are more difficult to diagnose because they often remain latent for years. Once such problems become manifest, they may be difficult or impossible to treat. These complications make chronic toxicity from organic pollutants the major concern of those investigating water quality. Depending on the chronic health problems they cause, pollutants are typically grouped in the following three classes: carcinogens, mutagens, and teratogens.

Any chemical that causes cancer, either directly or indirectly, is a carcinogen. Although carcinogenesis receives more research attention than any other chronic effect, scientists have not determined the precise relationship between carcinogens and cancer. They do know, however, that carcinogens stimulate various forms of malignant tumors.

Fewer than 30 agents have been directly linked to human cancer. In contrast, nearly 1,500 are reported as being carcinogenic in animal tests, although this number includes results from studies whose experimental designs were questionable. Only about 7,000 of the over 5 million known substances have been tested for carcinogenicity.

Among the chemicals designated as causing cancer are vinyl chloride, a component of some resins; benzene, a solvent produced in petroleum refining; and benzo(a)pyrene, which results from the incomplete combustion of coal, kerosene, and shale. Benzo(a)pyrene also results from grilling foods. Numerous other chemicals are known to produce cancer in animals; they include the pesticides ethylene dibromide (EDB), kepone, heptachlor, and dieldrin.

A chemical capable of producing an inheritable change in the genetic material is called a mutagen. We know little about the mutagenic effects of organic chemicals because most suspected mutagens have been tested only on microorganisms and animals. Chemicals found to be mutagenic on the basis of such tests include vinyl chloride, benzo(a) pyrene, bromoform, chlorodibromomethane, and the fungicides Folpet and Captan.

Any chemical that produces a birth defect is called a teratogen. True understanding of teratogens is very limited. Some of the chemicals shown to have teratogenic effects in animals are nicotine and the pesticides 2,4-D; ‘2,4,5-T; and folpet. It is important to realize, however, that studies using laboratory animals and extremely high exposure rates are not always accurate predictors of human teratogens. This fact is often overlooked and can lead to misunderstandings.

Besides the health problems discussed above, organic pollutants may also cause arteriosclerosis, heart diseases, hypertension, emphysema, bronchitis, and kidney and liver dysfunction. Some evidence also links certain organic chemicals to metabolic disorders that stimulate abnormal production of enzymes.

NCSU SoilFacts

Health Effects of Selected Drinking Water Contaminants
courtesy waterdrs.com