Earth Materials and Health Research Priorities for Earth Science and Public Health (2007) / Chapter Skim
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4 What We Drink
4 What We Drink
Pages 63-82
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From page 63... ...
The availability and quality of fresh drinking water are controlled by earth and atmospheric processes that generate the water cycle (e.g., NRC, 2004a, 2004b, 2004c)
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From page 64... ...
Because most fresh water is held in glaciers and polar ice caps, only ~30% of fresh water reserves are available as surface water or groundwater for human use (Dingman, 2002; see Figure 4.1)
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From page 65... ...
Drinking water contains a variety of substances that result from interactions with geological materials or from other sources such as atmospheric deposition, land application of fertilizer and wastes, mine drainage, and discharge of waste to surface water bodies. These include metals, major and trace elements, natural and anthropogenic organic substances, and microorganisms.
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From page 66... ...
66 EARTH MATERIALS AND HEALTH HEALTH BENEFITS OF WATERBORNE EARTH MATERIALS Some beneficial elements, such as calcium, magnesium, and fluoride, either occur naturally in water at sufficiently high concentration to positively influence human health or can be added to water as supplements. In addition, some microbes result in remediation of waterborne contaminants (bioremediation)
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From page 67... ...
. Fluoride Fluoride, as it occurs in drinking water, has two beneficial effects.
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From page 68... ...
, and typically the natural abundance of fluoride in surface waters does not result in a net health benefit. Exceptions are lakes and rivers in volcanic areas where these water bodies may receive acidic geothermal fluids containing high concentrations of dissolved fluoride.
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. HEALTH HAZARDS OF WATERBORNE EARTH MATERIALS Health hazards from drinking water arise from natural or anthropogenic contamination of source waters used for potable use.
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. A variety of substances associated with human activity can contaminate surface and subsurface water supplies, many of which are virtually unaffected by the geological framework.
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High arsenic levels in drinking water have been also reported in Argentina, Chile, China, Colombia, Hungary, Mexico, Peru, Taiwan, Thailand, and parts of the United States (NRC, 1999e, 2001b)
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. Many of these studies have been conducted in populations where the exposure to arsenic has been predominantly through contaminated drinking water (WHO, 2004; Smedley and Kinniburgh, 2005)
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The international maximum contaminant level of 10 mg L–1 for nitrate in drinking water has been set to prevent this condi tion. The adverse effects of nitrate in infants are exacerbated under some conditions, such as gastrointestinal infection.
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74 EARTH MATERIALS AND HEALTH Arsenic concentrations in at least 25% of samples exceeded: 50 µg/L Insufficient data 10 5 3 1 Alaska Hawaii Puerto Rico FIGURE 4.3 Arsenic concentrations found in at least 25% of groundwater samples in each county across the United States. SOURCE: Ryker (2001)
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From page 75... ...
The complexity of the problem will require input from many disciplines, including public health and earth sciences. Selenium and Molybdenum Selenium and molybdenum frequently occur together in soils, and these trace elements can be concentrated by agricultural practices, for example, in the San Joaquin Valley in California (Ong et al., 1997)
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From page 76... ...
coli 0157:H7 to contaminate the entire drinking water system, resulting in seven deaths and hundreds of illnesses (McIlroy, 2001)
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From page 77... ...
These include Giardia lamblia and Cryptosporidium parvum in particular, and the emerging pathogens Microsporidia and Cyclospora. Another emerging pathogen, Naegleria fowleri, is found in both soil and surface water environments.
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78 EARTH MATERIALS AND HEALTH Pharmaceutical Substances There are thousands of organic compounds that can potentially contaminate potable water sources, and many studies have examined the fate and transport of various classes of organic contaminants found in drinking water. Here the focus is on pharmaceuticals, including endocrine disrupting compounds (EDCs)
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From page 79... ...
TABLE 4.2 Hormones and Hormone Mimics Observed in U.S. Surface Waters Detection Frequency of Max.
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Because controversy will continue to surround EDCs and their potential short- and long-term risks to environmental and human health and welfare, EDCs remain an "emerging issue." OPPORTUNITIES FOR RESEARCH COLLABORATION There is a rich array of opportunities for earth and public health scientists to collaborate on research that addresses health and drinking water quality. The earth science component of this research relates to improving the understanding of sources, transport, and transformations of potentially hazardous substances in water to ultimately determine the concentrations to which people are exposed through their drinking water.
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From page 81... ...
Examples of specific research priorities include an understanding of the: • fate and transport of prions from soil to groundwater and surface water and their relationship to disease incidence;
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From page 82... ...
82 EARTH MATERIALS AND HEALTH • fate and transport of viruses through soil and vadose zones to groundwater and their relationship to disease incidence; • fate and transport of Naegleria fowleri from soil to water and disinfection strategies for contaminated wells; • fate and transport of endocrine disruptors through soil to groundwaters and the influence of long-term, low-level exposure on human health; and • fate, transport, and human health effects of perchlorate from soil and groundwater.
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