Recycled wastewater may more hazardous to use for crop and landscape irrigation than previously thought due to flaws in the way danger thresholds are currently determined.NOTE: This article originally appeared in the June 14, 2010 issue of Wine Industry Insight.
By Lewis Perdue
According to a major study published in June 2012 in the peer-reviewed scientific journal Endocrine Reviews, the current risk assessment methods to assess the dangers of endocrine disrupting compounds (EDCs) found in treated wastewater are severely flawed.
EDCs – including estrogens from birth control pills, powerful antibiotics, plasticizers like BPA and many other chemicals -- can disrupt or mimic human hormones in unpredictable ways even in the extremely small concentrations that are currently disregarded as inconsequential by government regulators. Many of the EDCs and chemicals find their way into wastewater by being flushed down a toilet or sink.
"Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities," concluded the study.
MASSIVE SCIENTIFIC UNDERTAKING
The massive scientific paper cited 845 other studies and was created by a team of twelve scientists led by Laura N. Vandenberg of the Tufts University Center for Regenerative and Developmental Biology, Medford, MA and by J. P. Myers of Environmental Health Sciences, Charlottesville, VA.
Other institutions represented by investigators of the study included:
- The University of California,
- Massachusetts General Hospital,
- National Institutes of Environmental Health Sciences,
- National Institutes of Health,
- Department of Health and Human Services,
- University of Minnesota School of Public Health
More information about the investigators and their connections can be found at the end of this article.
CONSEQUENCES FOR NORTH COAST AND OTHER CALIFORNIA VINEYARDS
While the Vandenberg/Myers study did not deal specifically with irrigation, it focused on many of the same chemical compounds found in the same concentrations as in treated wastewater used for irrigation.
For that reason, the study’s conclusions hold serious consequences for industrial and recreational landscape irrigation as well as the thousands of acres of premium California vineyards currently irrigated with highly treated wastewater.
Significantly for winegrape growers and ordinary citizens, every recent Environmental Impact Report (EIR) on treated wastewater irrigation conducted in Napa and Sonoma Counties acknowledges the presence of EDCs.
Those EIRs conclude, as did the North Sonoma County Agricultural Reuse Project EIR: “it is not currently possible, using existing standards and/or regulatory agency risk assessment methodology, to evaluate the endocrine effects of these chemicals, if any, at the low concentrations reported.”
PUBLIC HEALTH DECISIONS ON “A HOPE AND A PRAYER”
Because of the lack of science, no government standards or limits have been set for most EDCs and other chemicals found in even the most highly treated wastewater: “For the majority of chemicals in commerce, there are no data on health effects and thus no established high- or low-dose range,” said the Vandenberg/Myers study.
This means that risk-assessment, regulations and public health decisions are being made without sufficient data.
“They’re making public health decisions about treated wastewater on a hope and a prayer,” said a nationally respected organic chemist interviewed by Wine Industry Insight and who has participated in a number of government chemical risk assessment studies.
“They don’t know if the very small levels are harmful,” he continued. “But when they get to something that’s one part per billion or one part per trillion, they just feel it can’t be harmful, so they approve something.
“And while many chemicals may not be harmful by themselves at that level, EDCs are still potent,” he said. “That’s complicated by the fact that most of the hundreds of chemicals in treated wastewater have never actually been studied.
“And there are potential combinations we have no idea about. We have no clue – and probably never will – what the possible synergistic effects are … how all of those chemicals may combine, form new compounds, create new effects or what those effects might be.”
REGULATORY PROCESS FOR RISK ASSESSMENT OUTMODED
Ironically, the Vandenberg/Myers study comes on the fiftieth anniversary of Rachel Carson's epic environmental book, Silent Spring, which alerted the general public to the hazards of indiscriminate pesticide use, primarily DDT which is a potent EDC.
Initiated by her work, public awareness resulted in a slow accumulation of risk-assessment procedures developed by state and federal bureaucracies designed to assess the risks associated with the more than 10,000 chemicals that now blanket most aspects of human life.
But, the Vandenberg/Myers study in Endocrine Reviews points out that the current process for assessing risk relies on assumptions that are invalid when applied to EDCs.
This is because the current process, in general, tests for the toxicity of a chemical by administering relatively large doses of a chemical to test animals. The series of doses is decreased to a point to determine the lowest observed adverse effect level, or even a point where there is no observed adverse effect level. These levels typically range from concentrations of one part in a thousand (milli-) or a million (micro-).
Those calculating the risk assessment, guesstimate that concentrations in the one part per billion (nano-) to one part in a trillion (pico-) will be safe.
The Vandenberg/Myers study pointed out, “that EDCs can act in the nanomolar to micromolar range, and some show activity at picomolar levels.”
(“Molar” refers to a scientific method of estimating the total number of molecules of a compound in a given volume.)
“For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses,” said the study.
MONOTONIC VERSUS NON-MONOTONIC
The lack of predictability is the second flaw in the current government method which assumes that the chemical being tested always expresses itself the same way at every concentration. It assumes a greater effect at high concentration, a lesser effect at lower doses. In scientific terms, this predictability is called a monotonic dose response.
But EDCs and many other compounds are not so predictable because they affect different biological structures when present in varying concentrations. This is especially true for natural hormones, endocrine disrupters, many pharmaceuticals and even the ethanol in wine, beer and spirits.
The Vandenberg/Myers study explained that, “For all monotonic responses, the observed effects may be linear or nonlinear, but the slope [of the plotted line or curve] does not change sign. This assumption justifies using high-dose testing as the standard for assessing chemical safety. When it is violated, high-dose testing regimes cannot be used to assess the safety of low doses.”
The study then pointed out that EDCs as a group violate the rule by being non-monotonic.
WHY DOES NON-MONOTONIC MATTER?
Many chemical compounds are simply toxic: they damage and kill cells. The higher the concentration, the more toxic and the more cells die – the dose makes the poison.
Regardless of the concentration, these chemicals kill cells the same way. And, at the level of no observed adverse effects, they stop killing, or are tolerated by cells. This is a monotonic dose response.
But non-monotonic chemicals can affect different mechanisms in the body depending on the concentration.
One well-known non-monotonic response is the “U” shaped curve of the “French Paradox” or the activity of pharmaceuticals including aspirin and many hormones.
With these compounds, there is no effect at low concentrations. As concentration levels increase, scientific studies show an increasing beneficial effect. Then, beyond that level, the beneficial effect diminishes and later, high levels can be toxic and damaging.
This odd behavior is non-monotonic because the substances act on different parts of the body at different concentrations. At high levels they are toxic. At lower levels, they act on a variety of microscopic cell receptors and structures that allow them to have a different and beneficial effect.
Indeed, research has shown that at very low levels, EDCs can magnify or suppress the effects of natural hormones in the body or cause their own unique syndromes.
But nothing in nature says non-monotonic behavior always goes from damaging to beneficial as the concentrations go from high to low. Significantly, the effects of EDCs and other low-concentration chemicals are generally unstudied and unknown. However, in those few cases where they are better understood, EDCs have been found to have damaging effects.
Clearly, EDCs are an example of non-monotonic behavior that can go from deadly toxic (poisoning cells) to invisibly deadly (tumors, genetic effects, metabolic disorders and other diseases).
Indeed, as a future article in this series will explore, an increasing number of studies indicate that EDCs may be responsible for part of the current obesity and diabetes epidemics. They may also contribute to the decline of endangered species including salmon, frogs and other “cold-blooded” animals which seem to be more susceptible than mammals to chemical compounds.
NEXT: What EDCs and other chemicals are known to be in treated wastewater used for irrigation? At what levels? And having what effects?
FURTHER INFORMATION FROM THE PAPER:
Center for Regenerative and Developmental Biology and Department of Biology (L.N.V.), Tufts University, Medford, Massachusetts 02155; The Endocrine Disruption Exchange (T.C.), Paonia, Colorado 81428; Laboratory for Integrative Studies in Amphibian Biology (T.B.H.), Molecular Toxicology, Group in Endocrinology, Energy and Resources Group, Museum of Vertebrate Zoology, and Department of Integrative Biology, University of California, Berkeley, California 94720; Division of Extramural Research and Training (J.J.H.), National Institute of Environmental Health Sciences, National Institutes of Health, U.S. Department of Health and Human Services, Research Triangle Park, North Carolina 27709; Division of Epidemiology and Community Health (D.R.J.), School of Public Health, University of Minnesota, Minneapolis, Minnesota 55455; Department of Preventive Medicine (D.-H.L.), School of Medicine, Kyungpook National University, Daegu 702-701, Korea; Molecular Profiling Laboratory (T.S.), Massachusetts General Hospital Center for Cancer Research, Charlestown, Massachusetts 02129; Department of Anatomy and Cellular Biology (A.M.S.), Tufts University School of Medicine, Boston, Massachusetts 02111; Division of Biological Sciences (F.S.v.S.) and Department of Biomedical Sciences (W.V.W.), University of Missouri-Columbia, Columbia, Missouri 65211; Biology Department (T.Z.), University of Massachusetts-Amherst, Amherst, Massachusetts 01003; and Environmental Health Sciences (J.P.M.), Charlottesville, Virginia 22902
For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses.
Here, we review two major concepts in EDC studies: low dose and non-monotonicity.
Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies.
We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore non-monotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined.
We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from the cell culture, animal ,and epidemiology literature.We illustrate that non-monotonic responses and low-dose effects are remarkably common in studies of natural hormones and EDCs.
Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities.
We conclude that when non-monotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses.
Thus, fundamental changes in chemical testing and safety determination are needed to protect human health.
(Endocrine Reviews 33: 0000–0000, 2012)