February 2001: Volume 43, Number 2
Demographics of Water Consumption
by Kelly A. Reynolds, MSPH, Ph.D.
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Consumers need better assurances that the water they're supplied isn't tainted with disease-causing contaminants. According to a survey by the Water Quality Association, more than 50 percent of Americans worry about impurities in their tap water. This isn't surprising since the Center for Disease Control (CDC) estimates that 1 million people in the United States become sick each year from consuming contaminated water.
During a 1994 meeting of the American Academy of Microbiology, it was projected that "water treatment technologies, if adequate, are often not applied, are poorly applied, or are not sufficiently monitored and controlled. Inadequate, interrupted or intermittent treatment has repeatedly been associated with waterborne disease outbreaks."1 This statement reflects that even the best available technology for water treatment is plagued by failures in the system or improper regulation, monitoring and control. The U.S. Environmental Protection Agency (USEPA) Science Advisory Board concluded in 1990 that drinking water contamination is one of the highest environmental risks to human health.3
In response to the worsening water quality problem and decrease in consumer confidence, the USEPA has drafted (these may not be set in stone yet) specific milestones as goals to aim for by the year 2005 relating to drinking water quality:2
-- The population served by community water systems in violation of health-based requirements will be reduced to 5 percent (compared to 19 percent in 1994).
-- Every person served by a public water system that draws from an inadequately protected river, lake or reservoir will receive drinking water that's adequately filtered -- 393 systems serving 9.9 million people didn't meet all Surface Water Treatment Rule (SWTR) requirements for having filtration treatment in place for surface waters as of 1995.
-- Ninety percent of the nation's river and stream miles and lake and reservoir acres designated as drinking water supplies will provide water that's safe to use after conventional treatment as compared to 84 percent deemed safe in 1994.
-- Sixty percent of the population served by community water systems will receive their water from systems with source water protection programs in place (compared to only 5 percent of the population in 1993).
A status report on the USEPA's progress in achieving these goals by 2005 is not currently available. And regardless of the improvements in a water system's ability to treat and provide safe drinking water to consumers, the quality of water supplied is only as good as the quality of its subsequent distribution system. Deteriorated distribution piping allows water to become contaminated in the distribution system. According to a 1997 USEPA report to Congress, significant upgrades and repairs are needed throughout the country (see WC&P, "U.S. Water Infrastructure Needs," August 1999, p. 76)
Consumer water demands
Point-of-use (POU) devices can address the need for improved water quality at the tap. However, the development of effective POU devices requires an understanding of consumer water needs and usage. Figure 1 shows the typical per capita water usage per day in the United States. The majority of water consumption in the household is due to toilet flushes (29 percent), with washing machines and showers utilizing the second largest portion of water use (21 percent each). Water passing through all household faucets comprises 12 percent of the product use. While ingestion of water via drinking, cooking and oral hygiene practices are a significant transmission route for contaminants, other sources such as exposure via bathing and aerosols from showers and toilet flushing may also provide important exposure routes to harmful chemicals and microbes.
How much water do individuals consume each day? Figure 2 indicates the average tap water intake rates for each age group.4 Infants between the ages of 0-1 consume an average of 302 milliliters (ml) of water per day. Although they consume less water than adults, the effect of contaminants may be more severe due to their small size and under-developed immune systems. The average tap water intake rate increases as individuals age. Persons over 65 drink an average of 1,459 ml per day. This value is slightly less than the value of 2,000 ml -- 2 L -- used by the USEPA to determine risk assessment. Yes, actual consumption is 27 percent less than the USEPA's figure to calculate risk. Thus, the agency may be overestimating risk in some cases for two reasons: 1) an average is just that and some people may actually consume more, and 2) increasing the value of tap water consumption provides a slight margin of safety for risk analysis. On the other hand, exposure to water in foods and from sources other than the tap also adds to the value of total water consumed per day.
Ground vs. surface water
The National Ground Water Association reports that in 1995, 76.4 billion gallons of water each day were utilized from a groundwater source in the United States from 15 million groundwater wells.5 The percent of the public-supplied population served by groundwater in 1990 was highest in Florida, Mississippi, Nebraska, South Dakota and Idaho, serving between 71-to-97 percent (see Figure 3). Conversely, Colorado, Kentucky and Virginia supplied the least amount of the population from groundwater sources in 1990, serving less than 19 percent, with 81-to-100 percent of the population served by surface water (see Figure 4). In 1995, the top eight states relying on a groundwater source were: Florida (297 million gallons per day -- mgd), Michigan (194 mgd), Pennsylvania (181 mgd), North Carolina (172 mgd), New York (144 mgd), Ohio (138 mgd), Texas (130 mgd) and Illinois (129 mgd). 16 percent of the US population is served by private water wells with another 36 percent being served by public systems using groundwater sources. According to the USEPA, 26 percent of these systems serving less than 500 people don't treat their groundwater, compared to 13 percent serving between 501 and 3,299; 5 percent serving 3,301 and 49,999; and none serving above 50,000.
Recent studies by the USEPA indicate that a substantial number of groundwater sources show evidence of fecal contamination. The primary source of groundwater contamination has been listed as septic tanks that serve 25 percent of the U.S. population. Figure 5 shows the percentage of ground water source systems citing water contamination sources.
Developing contaminant rules
Amendments to the Safe Drinking Water Act in 1996 require that the USEPA publish a list, known as the Drinking Water Contaminant Candidate List (CCL), of pollutants that aren't currently regulated as part of the national primary drinking water regulations (NPDWR) but are known or anticipated to occur in public water systems (see www.epa.gov/OGWDW/ccl/cclfs.html). Beginning with 1998, a new CCL is required to be published every five years thereafter.
An initial broad list of more than 300 suspected contaminants was narrowed to a list of 60 priority contaminants. Each contaminant is divided into categories of need for regulatory determinations, research and occurrence. The USEPA will select at least five contaminants from the Regulatory Determination category and determine, by August 2001, if there's a need for their regulation based on whether a meaningful opportunity is likely to reduce health risk. If deemed necessary, a regulation may not be promulgated until February 2005.
Clearly, many waterborne contaminants are a potential risk to human health that are not yet regulated or monitored. Unpredictable source water conditions, inconsistent treatment efficacy, compromised distribution systems and unrecognized contaminants all contribute to the need for consumers to take control of their drinking water quality. Regardless of your particular demographics, properly maintained POU devices can provide additional measures of safety to the water you consume.
1. Moore, et al., "Waterborne disease in the United States, 1991 and 1992," Journal of the American Water Works Association (AWWA), 86: p. 87-99, 1994.
2. USEPA, "Environmental Goals for America, with Milestones for 2005, Policy Planning & Evaluation," (2162) December 1996.
3. USEPA, "Reducing risk: Setting priorities and strategies for environmental protection," SAB-EC-90-021, Washington, D.C., USEPA, Science Advisory Board, 1990.
4. USEPA, "Exposure factors handbook," EPA/600/8-89/043, Washington, D.C., 1989.
5. National Ground Water Association, "U.S. ground water industry market backgrounder," NGWA, Westerville, Ohio, 1998.
About the author
Dr. Kelly A. Reynolds is a research scientist at the University of Arizona with a focus on development of rapid methods for detecting human pathogenic viruses in drinking water. She holds a master of science degree in public health (MSPH) from the University of South Florida and doctorate in microbiology from the University of Arizona. Reynolds also has been a member of the WC&P Technical Review Committee since 1997. She can be reached at email: email@example.com
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