Safe Drinking Water

The Impact of Chemicals on a Limited Resource

Rip G. Rice

• Publisher: CRC Press
• Year: 2017
• eBook ISBN: 9781351357982
• Topic: Technology & Engineering
• Subtopic: Biotechnology
• Index: Technology & Engineering

A review of the nation's new coverages serves as a ready reminder that drinking water safety is more than regional of local concern. In recent times, the print media alone has drawn attention to barium, bacteria, heavy metals, and increasingly organic contaminants, in public water supplies located in Florida, Rhode Island, Texas, Oregon, Illinois, Minnesota, North Carolina, Michigan, and California, to name a few.

In an effort to address one of the major issues confronting the future of the nation's drinking water supplies, chemical contamination, the Drinking Water Research Foundation and the American Chemical Society presented the symposium, "Safe Drinking Water: the Impact of Chemicals on a Limited Resource." To add balance to the total presentation, two papers were included that were not part of the symposium.

Many questions as to the public significance of hundreds of organic chemicals known to be present in the national drinking water supply are waiting to be answered. In some areas of the country, aid rain-induced alterations of the natural leaching process represent an unexplored potential source of toxic pollutants. Finding workable ways to clean up the water supply will be an ongoing task.

Addressing these questions, as well as investigating how other countries are responding to these problems, the alternate sources available, such as bottled water, and point of use devices, the presenters in this symposium have attempted to explain the problems, situation, and alternatives.

As progress is made in one area, setbacks will occur in another. As we eliminate problems thought chemical technology, we often create others, such as contamination of our waters.

While all the situations, problems, and alternatives are not discussed in these proceedings, it is hoped that some attention will be brought to the public, government, and private sectors so that future work will be done to assure the nation of safe drinking water resources.

Chapter 1

Chemicals and Safe Drinking Water:
National and International Perspective

Robert A. Neal, PhD.

Chemical Industry Institute o f Toxicology
Research Triangle Park, NC 27709

Until quite recently, “pure” drinking water was judged by the absence of mud, taste, odor, color, fecal coliforms, total dissolved solids and a few other factors. However, the realization that drinking water is contaminated by a myriad of inorganic and, particularly, organic chemicals has changed the way we judge its purity. This change in the way we view our drinking water has been a natural outgrowth of the drastic change in the nature of the diseases that account for mortality and morbidity in our society. Only a few decades ago, infectious diseases and diseases caused by parasites were the major causes of morbidity and mortality. Now cardiovascular diseases and cancer are the prevailing threats to human health. The determination of the role of life-style and chemical contaminants in our environment, including drinking water, in the etiology of these diseases is now a major activity of governments, scientists and the medical profession. The purpose of this paper is to examine, in a general sense, the issue of chemical contamination of drinking water sources and, to the degree possible, the implications of that contamination to human health.

Certain human activities provide important sources of chemical contamination of drinking water. Among these are waste disposal from manufacturing and mining, the use of pesticides and fertilizers in agriculture, the disposal of domestic wastes including sewage, wastes from animal feedlots and highway deicing materials.

The decay products of vegetation are an important source of chemical contamination of drinking water largely unrelated to human activities. Various chemicals used for treatment and disinfection of water react with these decay products of vegetation to produce some compounds of potential concern for human health. An example is the production of chloroform and other trihalomethanes as a result of the use of chlorine in the treatment and disinfection of water supplies containing the vegetation decay products.

A number of the inorganic chemicals which are detected in water supplies are also of natural mineral origin. Other chemicals occur as contaminants in drinking water as a result of materials used in the water distribution systems. An example is the occurrence of polyaromatic hydrocarbons in drinking water as a result of the use of tar in coating pipes used in the distribution system. Radionuclide contamination in drinking water can be of both natural origin or a result of human waste disposal practices. Those of natural origin currently are of greatest concern.

Chemicals found as contaminants in drinking waters can be grouped conveniently into three classes: inorganic, organic and radionuclides. A number of inorganic compounds are found as contaminants in drinking water. As noted previously, some of these are of natural origin. One of these, fluoride, often is purposely added to water supplies as a prophylactic against dental caries. Some of these inorganic contaminants of drinking water are of concern as regards potential adverse human health effects. These are:

• Arsenic (cancer)
• Cadmium (kidney damage)
• Chromium (cancer)
• Cyanide (acute toxicity)
• Fluoride (skeletal fluorosis)
• Lead (nervous system)
• Mercury (nervous system)
• Nitrate (methemoglobinemia)
• Selenium (gastrointestinal)

A number of governments and international bodies have recommended maximum levels for these inorganics in drinking water.

Inorganic contaminants other than those noted above for which there is some, but much less concern for human health, are aluminum, barium, asbestos, beryllium, nickel and silver. A few governments have set maximum concentration levels for some of these inorganic compounds.

Other inorganic chemicals contribute undesirable aesthetic or organoleptic properties to drinking water. These are copper, iron, magnesium, manganese and zinc, and levels consistent with good water quality also have been established for some of these.

In the past decade several hundred different organic chemicals have been identified as contaminants of drinking water. However, those so far identified represent but a small fraction of the total organic matter present in drinking water. The majority of the organic compounds present in drinking water consist of nonvolatile, water-soluble substances, a substantial fraction of which have molecular weights in excess of 1,000. The identification of the structures of most of these nonvolatile compounds will be exceedingly difficult.

In a conventional sense, it will be necessary to know the structure of these compounds before it is possible to begin an assessment of their potential toxicity to humans consuming the water. However, because of the enormous number of compounds normally present and the difficulty in identifying the structure of the majority of the compounds, some consideration is being given to carrying out animal studies on a representative mixture of the organic compounds present in a drinking water supply, then basing the assessment of the potential toxicity to humans consuming the water on the results obtained in animals using the mixture.

In the meantime, attempts to control the levels of potentially harmful organic contaminants in drinking water is based on examination of drinking water supplies for specific compounds or classes of compounds known to be potentially toxic to humans. The classes of compounds of particular interest include the halogenated alkanes and alkenes, the polycyclic aromatic hydrocarbons, benzene, and various alkyl-substituted benzenes, chlorophenols, chlorobenzenes, nitrosamines, pesticides, aromatic amines, aromatic nitro compounds, polychlorinated biphenyls and the phthalate esters.

The chlorinated alkanes and alkenes of greatest interest based on their occurrence and evidence of toxicity in experimental animals are:

• Chloroform (and other trihalomethanes)
• Trichloroethylene
• Tetrachloroethylene
• Carbon tetrachloride
• 1,1,1-Trichloroethane
• 1,1-Dichloroethylene
• 1,2-Dichloroethane
• 1,2-Dichloroethylene
• Trichloroethylene
• Methylene chloride
• Vinyl chloride

The pesticides of most interest based both on occurrence and/or evidence of toxicity or potential toxicity to humans are:

• DDT
• Aldrin
• Dieldrin
• Heptachlor
• Heptachlorepoxide
• 2,4–D
• 2,4,5–T
• Chlordane
• Lindane
• Methoxychlor
• Benzene hexachloride
• Triazine herbicides
• Hexachlorbenzene
• Endrin
• Toxaphene
• Aldicarb

In addition to benzene itself, the alkylbenzenes, halogenated benzenes and chlorinated phenols of greatest interest are:

• Toluene
• Ethylbenzene
• m-Xylene
• 1,2-Dichlorobenzene
• 1,4-Dichlorobenzene
• Trichlorobenzenes
• Bromobenzene
• o-Chlorotoluene
• Pentachlorophenol
• 2,4,6-Trichlorophenol.

Guidelines suggesting maximum concentrations based on potential health effects have been established, or soon will be established by some governments and international bodies for a few of these compounds. Most notable are:

• the Trihalomethanes
• Endrin
• Lindane
• Methoxychlor
• Toxaphene
• 2,4–D
• 2,4,5–T
• DDT
• Chlordane
• Hexachlorobenzene
• 1,2–Dichloroethane
• 1,1–Dichloroethylene
• Pentachlorophenol
• Tetrachloroethylene
• Trichloroethylene
• Vinyl chloride
• 2,4,6-Trichlorophenol

The radionuclides which occur as contaminants of drinking water which are of greatest concern for human health are radium-226 and -228, uranium and radon. All of these are of natural origin and are a health concern because of the potential for radiation-induced cancer.

Although large numbers of potentially toxic organic chemicals have been detected as contaminants of drinking water, in fact, only a small fraction of the organic chemicals detected as contaminants in drinking water have been examined by available means for their potential to cause toxic effects in humans. It is logical to assume that when properly tested, some of these compounds will show evidence of a potential to cause toxic effects in humans consuming the water. However, in considering the potential of contaminated drinking water to cause adverse health effects in humans, it is important to keep in mind that in terms of the number of people affected, microbial contamination of water is of far greater concern than chemicals. The adverse health effects experienced when consuming water excessively contaminated with microorganisms which are pathogenic to humans usually occur shortly after ingestion and if they do not cause mortality, usually are of short duration. In contrast, the potential human diseases caused by some chemical contaminants in water are largely believed to be delayed effects which occur as a result of consuming the contaminanted water over extended periods of time.

The greatest public concern is for the potential of chemical contaminants in drinking water to cause cancer; this concern also is reflected in the activities of governments. However, knowledgeable scientists and health professionals believe that some attention also should be paid to the ability of chemical contaminants in drinking water to adversely affect other organ systems or biological processes which do not easily repair themselves or in which the effects are not easily reversible. These include effects on the fetus, germ cells, the reproductive systems, and the nervous system.

In evaluating the human health effects which may occur upon exposure to chemicals occurring as contaminants in drinking water, there is an implicit search for absolute answers on the part of most governments, regulatory agencies and the public. Witness the increasing uses of mathematical models to carry out quantitative risk assessments for human cancer incidence using data from studies carried out in experimental animals with compounds present as contaminants in drinking water. Data obtained from these mathematical models generally would not be accepted for publication by refereed journals publishing biological data because currently there is no experimental means for verifying their accuracy. Yet these numbers are largely perceived by the public to be a precise statement of the risk. An important but difficult task for the informed scientific and medical community is to educate the public, government officials, decision-makers within regulatory agencies and the less informed medical and scientific community that with the technology currently available we are not able to make precise judgements about the potential health risks inherent in the consumption of chemically contaminated drinking water.

In evaluating the potential for human toxicity of chemical contamination of drinking water, three methodologies are available (Neal, 1982). These are epidemiological investigations in populations consuming the contaminated water, “short-term” tests for the presence of mutagenic and potentially carcinogenic chemicals and studies in experimental animals.

To date, epidemiological studies have revealed a few instances of acute or subacute toxicity resulting from humans consuming water contaminated with chemicals. Most of these have involved contamination with inorganic chemicals. Notably, these have involved gastrointestinal disturbances as a result of improperly designed, improperly operated or malfunctioning fluoridation equipment, gastrointestinal disturbances ...

Table of contents

• Cover Page
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• 1. Chemicals and Safe Drinking Water: National and International Perspective
• 2. Drinking Water: a Global Victual
• 3. Public Drinking Water and Chemicals
• 4. Bottled Water: an Alternative Source of Safe Drinking Water
• 5. Overview of Point-of-Use Water Treatment Technology
• 6. An Effective Alternative to Official Regulation of Indirect Additives to Drinking Water
• 7. The Water Treatment Chemicals Codex
• 8. Disinfectant Chemistry In Drinking Water–overview Of Impacts On Drinking Water Quality
• 9. By-Products Of Chlorination: Specific Compounds And Their Relationship To Total Organic Halogen
• 10. Ozone For Drinking Water Treatment – Evolution And Present Status
• 11. The Occurrence of Contamination in Drinking Water from Groundwater Sources
• 12. Improved Monitoring Techniques to Assess Groundwater Quality Near Sources of Contamination
• 13. NBS Environmental Standard Reference Materials for Use in Validating Water Analysis
• 14. Regulation of Contaminants in Drinking Water
• 15. Federal Protection of Groundwater
• 16. The World Health Organization and Guidelines and European Economic Community Directives
• 17. Regulatory Flexibility and Consumer Options Under the Safe Drinking Water Act
• 18. Structure and Regulation of the European Bottled Water Industry
• 19. Congressional Initiatives
• 20. Conference Summation
• Index