Agua Latinoamerica

On Tap: Human Perception is a Failed Indicator of Water Quality Concern

By Kelly A. Reynolds, MSPH, PhD

More than 15 million Americans routinely consume drinking water from a private groundwater source(1). Private drinking water wells are generally sourced by groundwater supplies but are still subject to contamination due to agricultural operations, overland flows and septic-tank effluents. The US Centers for Disease Control and Prevention (CDC) reports an increased proportion of waterborne disease outbreaks associated with private household drinking water supplies over the last 30 years, where groundwater causes the majority of documented US waterborne outbreaks. Whereas public water systems are subject to routine testing to ensure quality compliance with state and federal regulatory standards or quality, such standards are not confirmed or enforced with private drinking water systems.

Your water, your responsibility

Any system that serves fewer than 25 people at least 60 days per year and has no more than 15 service connections can qualify as a private water supply and is, therefore, outside of the US EPA’s jurisdiction for maintaining the regulatory standards, including routine monitoring. Numerous government agencies, including the CDC, US EPA, US Geological Survey (USGS) and the National Ground Water Association, all recommend private well owners check their drinking water frequently to confirm its safety. Routine monitoring is not only advantageous for determining the current water quality but for developing a baseline of expected levels for specific indicators. Changes in the chemical or physical properties of the supply may be the first red flag indicating a human health risk.

Any system that serves fewer than 25 people at least 60 days per year and has no more than 15 service connections can qualify as a private water supply and is, therefore, outside of the US EPA’s jurisdiction for maintaining the regulatory standards, including routine monitoring. Numerous government agencies, including the CDC, US EPA, US Geological Survey (USGS) and the National Ground Water Association, all recommend private well owners check their drinking water frequently to confirm its safety. Routine monitoring is not only advantageous for determining the current water quality but for developing a baseline of expected levels for specific indicators. Changes in the chemical or physical properties of the supply may be the first red flag indicating a human health risk.

A recent survey of research conducted over three decades indicates that the prevalence of coliform bacteria ranges from 15 to 85 percent in private well waters. More recently, 10 percent of 538 well water samples collected in a Virginia study tested positive specifically for fecal bacteria.3 Such positive frequency suggests a common and chronic condition of impairment for groundwater supplies, warranting routine monitoring and intervention.

Quality indicators

Standard water quality markers include total coliforms, fecal coliforms (i.e., E. coli), pH, nitrates and volatile organic compounds (VOCs).4 In general, the presence of total and fecal coliforms is not a direct health risk. Instead, it indicates the potential for a breach in the quality of the water. While it is not uncommon to find total coliforms in natural environments, a dramatic increase in their numbers could indicate a quality change in the water supply. Fecal coliforms and E. coli, on the other hand, are of more concern, given that they indicate contamination with animal or human feces. Feces carry other, more harmful microbial pathogens that, when ingested, may cause serious illness, such as diarrhea, hepatitis or even death.


Table 1. Top causes of outbreaks in wells(2).

  • 1. Hepatitis A
  • 2. Giardia
  • 3. Campylobacter, E. coli (tie)
  • 4. Shigella
  • 5. Cryptosporidium, Salmonella (tie)
  • 6. Arsenic, gasoline, nitrate, phenol, selenium (tie)

Water pH is another quality indicator that affects the taste, smell and appearance of water. The generally accepted pH range for groundwater is 6 to 8.5. Water that is below neutral (pH = 7) is considered acidic and water above pH = 7 is referred to as basic. Highly acidic water can be caustic to pipes, causing heavy metals like iron, copper and lead to leach and enter the water supply. Over time and at increased levels, these exposures can be toxic to the consumer. Basic water, or hard water, is not a serious health concern but is a nuisance in regard to scale buildup on fixtures and surfaces and reduction of the efficiency of soaps and detergents. Use of neutralizers and water softeners are common interventions to adjust water that ranges far from the ideal neutral pH of pure water.

Nitrates are problematic in excess amounts (>10 mg/L), especially to infants and children. Fertilizers, wastewater effluent, leaking septic systems and runoff from agricultural feed lots are all potential sources of nitrates. Unpolluted natural waters typically have nitrate levels below four mg/L. VOCs commonly contaminating well water supplies are chemicals from industrial or fuel-related sources, such as benzene, carbon tetrachloride, toluene, trichloroethelene and methyl tertiary butyl ether (MTBE).4 An understanding of the risks in your particular geographical area is important in deciding for which VOCs to test. Local health departments and US EPA regional reports provide sources for determining contaminants of concern in your area.

Taste- and odor-failed indicators

Recently at the APHA 142nd Annual Meeting and Exposition of the American Public Health Association in New Orleans, LA, a researcher from Virginia Tech presented new information on homeowner perceptions of quality and risk related to private water supplies (5). A recent study of almost 15,000 private household well samples collected by the Virginia Cooperative Extension Program found that homeowners did not routinely test their water unless a problem was perceived at the tap. Unfortunately, triggers of a problem at the tap are generally related to taste and odor issues that are not necessarily predictors of a harmful water quality problem.

In 1981, a two-year study by the Illinois State Water Survey found that the level of odors in finished municipal surface water supplies was weakly correlated with 20 commonly used biological, chemical and physical water quality parameters.6 Changes in taste and odor constituents were predictable based on seasonality, not necessarily as a function of water pollution. Odors were most notable between the months of May to October when warmer temperatures create anoxic conditions in water, where dissolved oxygen levels decrease, correlating to increased odor production. A similar study was conducted in a public municipal groundwater supply by researchers at the University of Arizona. Here, complaints from the consumer triggered a water quality analysis in the home. Like the Virginia study, consumer perceptions of poor water quality did not significantly correlate with true quality concerns (unpublished data). The bottom line is that human perception is not a reliable water quality indicator.

Barriers and solutions

Recent data indicates that private wells are frequently contaminated but not being routinely monitored for harmful contaminants. Homeowners appear to be concerned about their water quality when tastes and odors change. Taste and odor changes, however, are often temporary and not consistent with the occurrence of harmful bacteria or chemicals. While costs and accessibility may play a role, causes of homeowner resistance to routine water quality monitoring is not clear. More research is needed to determine what barriers contribute to a lack of safety compliance in private water supply management. Educating consumers that good tasting and smelling water may not be free of harmful microbial and chemical contaminants is expected to help remove some of the commonly held, but faulty, water quality perceptions.

References

1. US Census Bureau, Current Housing Reports, Series H150/07, American Housing Survey for the United States: 2007, US Government Printing Office, Washington, DC, 2008.
2. Water related diseases and contaminants in private wells, Centers for Disease Prevention and Control, 7 April 2014. [Online]. Available: www.cdc.gov/ healthywater/drinking/private/wells/diseases.html. [Accessed 12 1 2015].
3. Allevi, R.P.; Krometis, L.H.; Hagedorn, C. et al, “Quantitative analysis of microbial contamination in private drinking water supply systems,” Journal of Water and Health, vol. 11, no. 2, pp. 244-255, 2013.
4. Well Testing, Centers for Disease Prevention and Control, 3 May 2010. [Online]. Available: www.cdc.gov/healthywater/drinking/private/wells/ testing.html. [Accessed 9 1 2015].
5. Pafitis, Natalie, “BMC Public Health Back from APHA in New Or- leans,” BioMed Central, 2 December 2014. [Online]. Available: http://blogs. biomedcentral.com/bmcseriesblog/2014/12/02/bmc-public-health-back- from-apha-in-new-orleans/. [Accessed 11 January 2015].
6. Shundar, L. and Evans, R.L.“Relationships between Odor and Com- monly Measured Water Quality Characteristics in Surface Water Sup- plies,” Illinois State Water Survey, Champaign, 1981.

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