CHEMICAL CONTAMINATION: Is our tap water safe to drink?

Jason Eberhart-Phillips, MD, MPH

“Clean and safe water is the foundation of healthy communities, healthy families and a healthy economy.” So said Robert Perciasepe, deputy administrator of the Environmental Protection Agency, last year when wrapping up his testimony at a U.S. Senate hearing on drinking water safety.[1] Perciasepe had been summoned to Capitol Hill because of mounting concerns that America’s drinking water may not be as safe as it should be, and that years of lax regulation of chemical contaminants under the 38-year-old federal Safe Drinking Water Act could be making the problem worse.

Prior to the hearing, the EPA had been criticized in a report by the Government Accountability Office for the way the agency determines which contaminants to regulate among the tens of thousands of chemicals released into the environment by industry, agriculture and consumers. (The GAO is the investigative arm of Congress.) Although researchers have identified hundreds of chemicals in drinking water supplies that may cause cancer, birth defects or other human health problems, the EPA has prescribed standards for just 91 contaminants. In the past 16 years, only one toxic substance--perchlorate--has even begun the process of being added to the list of regulated contaminants, and that one exception has come only in response to public outcry.

Beyond this glacial pace of change, many of the standards used for contaminants the EPA actually regulates may be out of date. Most of the maximum contamination levels the EPA allows--levels given in parts per billion--have not been changed since the 1980s or earlier, despite new research that points to unwelcome health effects for some contaminants at lower concentrations than previously thought.

How clean and safe is the water coming out of the taps in homes and businesses today? Critics say that we don’t really know if our water is safe, and that we could do a better job of finding out. The Environmental Working Group (EWG), for example, reviewed the water quality records of almost 48,000 suppliers in 45 states from 2004 to 2009 and found that more than 200 unregulated but potentially harmful chemicals were present in the nation’s drinking water supply.[2] Because no maximum allowable levels in drinking water have been established for any of these contaminants, they are legally permissible in any amount--even at levels that may, over time, endanger the health of some consumers, according to the EWG.

Records obtained by the EWG for the two largest suppliers in Marin County found no violations of mandatory state or federal standards, but each supplier had eight unregulated chemicals detected in their water at levels exceeding established health guidelines. (For details of these findings, go to www.ewg.org/tap-water/whats-in-yourwater.)

In all large systems, drinking water is routinely monitored for contamination from infectious agents, radionuclides and chemicals, both organic and inorganic. These contaminants may occur naturally, or they may enter the drinking water supply as the result of storm water runoff, wastewater discharges, agriculture or mining. Public health attention is increasingly focused on the potential risk from the immense array of chemicals now on the market, including pesticides, fertilizers, volatile organic compounds and pharmaceuticals. According to the EWG, hundreds of these chemicals appear in treated drinking water, and most aren’t being regulated.

“Those [chemicals] that are in the drinking water should be regulated by the EPA so that the public can be assured that levels are safe,” said Lynn Goldman, dean of the School of Public Health at George Washington University, at last year’s Senate hearing. “Minus the establishment of clear maximum contaminant levels how are we to know that the chemicals in [the public’s] water are safe?”[3]

According to the GAO report issued before the Senate hearing, the EPA relied more on the easy availability of data than on considerations of public health risks when choosing which contaminants to consider for future regulation.[4] Even worse, the GAO found that the EPA often failed to use testing methods that were sensitive enough to detect low-level exposures of potential contaminants in drinking water--exposures that could be harmful to health. In a classic example of “see no evil,” the EPA made its determinations not to regulate certain contaminants largely on the basis of not finding them in most drinking water supplies. As the GAO noted, the absence of occurrence data does not always imply the absence of risk.

The banned insecticide dieldrin is a case in point. Dieldrin can persist in the environment for decades, but the EPA chose not to regulate it in drinking water after relying on tests that could only detect dieldrin down to a concentration that is at least 10 greater than the level at which adverse health effects might occur from prolonged exposure. These effects include headaches, dizziness, irritability, vomiting or uncontrollable muscle movements. Chronic exposure to dieldrin may cause an increased risk of cancer or disorders of the central nervous system.

In determining that dieldrin did not need to be regulated in the nation’s drinking water, EPA officials noted that the chemical was detected in fewer than 1 in 1,000 samples. But when a more sensitive testing regime was used by the U.S. Geological Survey, it found dieldrin in 3.1% of public well samples--and most of the tainted specimens were contaminated at a level far above the benchmark for health concern.

The GAO report also criticized the EPA for failing to protect especially vulnerable populations--including young children, the frail elderly and people with weakened immune systems--from pollutants in drinking water. Until recently, the EPA’s assessments of risk have been largely based on research done with healthy adults or animals, failing to take into account subgroups with unique exposure patterns or sensitivities. Children, for example, have a greater susceptibility to many toxins detected in drinking water because their bodies and minds are rapidly growing. They also consume far more drinking water per unit of body weight than adults do, increasing their exposure to whatever contaminants the water contains.

The GAO report offered its sharpest criticism for the way the EPA initially decided not to regulate perchlorate in drinking water in 2008. The report said the EPA “used a process and scientific analyses that were atypical, lacked transparency, and limited the agency’s independence in developing and communicating scientific findings.”

The story of perchlorate, which is used to make rocket fuel, fireworks, flares and explosives, illustrates how advances in detection and in the knowledge of health effects have created a new urgency to regulate chemical contaminants in drinking water. Sadly, the story also illustrates how regulatory processes designed to protect the public can be trumped by other considerations.

During the 1990s, perchlorate started turning up in groundwater all around the United States, as routine testing for such chemicals improved. Already perchlorate was known to inhibit the thyroid gland’s uptake of iodine, but it was assumed that such effects occurred only at higher doses than were possible from exposure to drinking water. New evidence in animals, however, showed that the chemical’s adverse effects could occur at much lower levels of exposure than previously thought.[5] A subsequent study, published by the Centers for Disease Control and Prevention in 2006, showed that thyroid hormone levels could be significantly reduced in women who were exposed to background levels of perchlorate.[6]

Further studies found that perchlorate is concentrated in breast milk, and may replace essential iodine for breast-fed babies. One study found that 90% of nursing infants born to women who drank water containing perchlorate at a level equal to a preliminary EPA remediation target would ingest nearly three times as much of the chemical as the EPA’s own maximum acceptable daily dose.[7]

Removal of perchlorate from groundwater sources of drinking water can be enormously expensive, and regulation may end up putting vast groundwater resources off limits for suppliers unable to meet the added treatment costs. In the Inland Empire of Southern California, where groundwater aquifers have been found to contain very high levels of perchlorate, the remediation is expected to cost hundreds of millions of dollars and take up to 30 years to complete.[8]

The GAO report describes in detail how high-level EPA officials directed staff to develop a justification for not regulating perchlorate in drinking water, bypassing the agency’s standard internal scientific review process. In part because of the criticism of its 2008 decision, the EPA reversed course in 2011 and said it would develop regulatory standards for perchlorate in drinking water in the next two years.

For physicians and patients alike, the controversies over unregulated contaminants, out-of-date standards and weak protections for vulnerable people serve to highlight the importance of safe drinking water to community health. While most of the serious infectious risks from drinking water in the United States are thankfully becoming rare, there is less certainty that all necessary steps have been taken to eliminate human health risks from long-term exposure to chemical contaminants.

Patients may ask if bottled water is a safer alternative than tap water. The answer is no. Unlike your local water company, manufacturers of bottled water aren’t required to publish their water quality data, so consumers don’t really know what they are getting. Many of the same chemicals that contaminate tap water have turned up in bottled water in independent tests. In fact, some brands of bottled water are nothing more than bottled tap water.

In-home filtration devices are another alternative that patients may ask about. While these devices can help to remove some contaminants, they require repeated replacement to be effective, and that can be expensive over time.

The best way forward for whole communities is for greater protection of drinking water sources from chemical pollutants. At a minimum, the current concerns over chemical contamination point to a need for increased investment in monitoring of drinking water and for more research into potential health effects, both in the general population and in more sensitive groups. Only with sufficient data, reviewed through an open and transparent scientific process, can adequate regulation be undertaken to ensure that our drinking water is as clean and safe as it can be.

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Dr. Eberhart-Phillips is the former Public Health Officer for Marin County.

References

1. Testimony of Robert Perciasepe to the U.S. Senate Committee on Environment and Public Works, epw.senate.gov/public/index.cfm?FuseAction=Hearings (July 12, 2011).

2. Environmental Working Group, National Drinking Water Database, www.ewg.org/tap-water/fullreport (2009).

3. Testimony of Lynn Goldman to the U.S. Senate Committee on Environment and Public Works, epw.senate.gov/public/index.cfm?FuseAction=Hearings (July 12, 2011).

4. Government Accountability Office, Safe Drinking Water Act, GAO-11-254 (2011).

5. McLanahan ED, et al, “Competitive inhibition of thyroidal uptake of dietary iodide by perchlorate does not describe perturbations in rat serum total T4 and TSH,” Enviro Health Perspec, 117:731-738 (2009).

6. Blount BC, et al, “Urinary perchlorate and thyroid hormone levels in adolescent and adult men and women living in the United States,” Enviro Health Perspec, 114:1865-71 (2006).

7. Ginsberg GL, et al, “Evaluation of the US EPA/OSWER preliminary remediation goal for perchlorate in groundwater,” Enviro Health Perspec, 115:361-369 (2007).

8. Testimony of Anthony Araiza to the US Senate Committee on Environment and Public Works, epw.senate.gov/public/index.cfm?FuseAction=Hearings (July 12, 2011).