Setting the Record Straight: Introduction
Environmental Working Group Response to "A Review of the Science, Methods of Risk Communication and Policy Recommendations in Tap Water Blues" by David B. Baker, R. Peter Richards, and Kenneth Baker
On October 18, 1994, the Environmental Working Group and Physicians for Social Responsibility (PSR) released Tap Water Blues, an analysis of pesticide contamination of drinking water supplies in the Midwest. The report, which identified over ten million individuals exposed to five herbicides (atrazine, cyanazine, simazine, alachlor, and metolachlor) at levels that exceed EPA's negligible cancer risk standard of one additional cancer case per million individuals, made three recommendations:
- A two year phase-out of the triazine herbicides. Tap Water Blues notes that safer chemical alternatives and methods to reduce chemical herbicide dependence are readily available to farmers.
- The establishment of a new drinking water Maximum Contaminant Level (MCL) for total triazines, set at a level at which cancer risks do not exceed the de-minimis standard. This recommendation is based on the near identical toxicological impacts of the triazines and their chlorinated degradates.
- Reform of government farm programs to include incentives for farmers to cut back or eliminate use of the most toxic herbicides through greater use of integrated weed management measures based on economic threshold models.
Tap Water Blues received widespread media attention, and was soon followed by EPA action in two areas. First, the agency rejected a petition by the Ciba Corporation, the maker of atrazine, to weaken the current drinking water standard for this chemical and allow seven times more atrazine in drinking water. Second, on November 10, 1994 the EPA initiated a Special Review of the triazine herbicides, the first formal regulatory step towards certain restrictions and a possible phase-out of some or all uses of the triazine herbicides. On November 14, a critique prepared by Dr. David Baker, Peter Richards, and Kenneth Baker, of Heidelberg College, was released to the media. Our response to the Baker, Baker, and Richards critique (referred to below as Baker ) is presented below.
Several important events have transpired since the release of Tap Water Blues and the Baker response. On August 5, 1995, the EPA and the DuPont corporation announced the voluntary phase-out of the herbicide cyanazine over the next four years. This decision sends a clear signal to the agricultural community that cost competitive alternatives to the triazines are currently available.
On August 17, 1995, the Environmental Working Group and a network of citizens groups across the Midwest, released Weed Killers by the Glass, an analysis of herbicides in tap water in 29 midwestern cities. This report presented the first ever results of tap water sampled from peoples homes during the peak contamination period.
The study, which sampled tap water every three days from May 15, through July 2, 1995 for cyanazine and atrazine, found atrazine in the treated drinking water of 28 out of 29 cities and cyanazine in the tap water of 25 cities. In eight cities, more than half of the samples exceeded either the atrazine maximum contaminant level (MCL), or the cyanazine lifetime health advisory. The peak level of contamination found in the study was more than 30 times federal health standards. In thirteen cities, peak contamination levels were at least triple federal health standards.
Once a month, tap water samples were tested for eleven different herbicides and by-products. In more than two thirds of the cities, 21 out of 29, at least four, and as many as nine herbicides and toxic herbicide by-products.
Events Since The Release of Tap Water Blues
EPA has announced three major actions since the release of Tap Water Blues. These decisions, which were taken by the agency in response to their own internal scientific evaluations, substantially validated virtually all of the findings in Tap Water Blues.
Denial of Ciba Petition
On October 17, 1994, EPA released a letter to the Ciba Corporation denying a request to increase (weaken) the atrazine MCL by a factor of seven. EPA's analysis in this letter indicated that many of the conclusions reached by the Environmental Working Group about the inadequacy of current standards and the need for new approaches were accurate. In particular, two findings were addressed in the letter. EPA confirmed that there is a need to look at the triazines as a toxicological group, and admitted that current standards may not adequately protect the public from atrazine alone or the triazine herbicides when considered together. The letter noted that:
We are also considering whether to regulate the chlorotriazines (i.e. atrazine, cyanazine, simazine) as a group rather than regulating atrazine alone. The triazines have similar structure, mode of action, toxicity and degradates. We presently do not account for the potential additive increase in cancer risk due to exposure to the components of the chlorotriazines mixture, and therefore may be understating risks when regulating the contaminants individually.
Adding further that:
...the Agency may have underestimated the risk from atrazine exposure in drinking water (See Note 1.)
One week later, the Environmental Working Group obtained a report by the American Water Works Association, the industry trade group for the nation's drinking water utilities. This report, Seasonal Variations of Pesticides In Surface Waters, indicated that EWG had significantly underestimated the problem of herbicide contamination in drinking water. The AWWA report estimates that 84 million individuals are drinking pesticide-contaminated water, and that over 19 million are exposed to just two herbicides at levels that exceed current EPA drinking water standards. Both of these figures were far higher than those reported by EWG.
Initiation of the Triazine Special Review
On November 10, the EPA announced a Special Review of all three of the triazine herbicides analyzed in Tap Water Blues. This Special Review, the first initiated since 1988, marks the first time that the EPA has reviewed more than one pesticide simultaneously based on combined risk. It also signals the first step towards certain restrictions and a possible phase-out of some or all uses of the triazine herbicides. EPA's analysis supporting the Special Review confirmed the findings in Tap Water Blues, and provided further evidence of widespread contamination and risks from the triazines. Specifically, the EPA made a convincing case for analyzing the triazines as a group:
A combined Special Review of the triazines is more appropriate than examining each individually. This determination is based on the following considerations. All three (1) are structurally related chemicals (2) induce mammary tumors when fed to rats and are classified as Group C, possible human carcinogens (3) degrade or metabolize to similar degradates/metabolites (4) are generally similar in terms of environmental fate... (See Note 2.)
The EPA's preliminary estimates of cancer risk from triazine contaminated drinking water are in the range from 1x10-5 to 5x10-5 -- very similar to those reported in Tap Water Blues 3. Compounding these risks, the EPA cited additional dietary risks from triazine residues in milk and meat, and occupational risks to professional applicators as high as 10-2.
In sum, since the release of Tap Water Blues, the three critical scientific aspects of the report -- the exposure estimates, the cancer risk assessments, and our method of looking at the triazines and their chlorinated metabolites as a group -- have been confirmed by two independent authoritative reviews.
EPA/DuPont Agreement to Phase Out Cyanazine
On August 2, 1995, the EPA and DuPont Agrichemical company announced the phase-out and ultimate ban of cyanazine. Under the agreement, DuPont, the sole manufacturer of cyanazine, will cancel the registrations of all cyanazine products on December 31, 1999. Prior to then, application rates will be reduced to encourage a gradual transition to substitute products. Cyanazine (Bladex) is DuPont's top selling agricultural pesticide.
In announcing the ban, DuPont cited concerns about the cost of battling the ongoing special review, as well as EPA's concerns about the cancer risks that cyanazine presents to the public and pesticide applicators. Implicit in the ban is DuPont's recognition that the EPA considers cyanazine a high risk compound and that the agency would pursue aggressive regulation of the product.
The Baker Review of Tap Water Blues
On November 14, Dr. David Baker and colleagues at the Water Quality Lab at Heidelberg College, Ohio, released their critique of Tap Water Blues. Baker and colleagues have long been active in studying the impact of agriculture and water resources, concluding almost without exception that the impacts were minimal, and that although these herbicides were present in drinking water they did not pose a significant health risk. The scientific issues raised by Baker can be summarized as:
1. Are the exposure estimates Tap Water Blues accurate?
2. Did we "fabricate a risk standard"?
3. Is it appropriate to assess the risk from the triazines as a group?
4. Are the risks assessments otherwise accurate and based on the best science?
The answers to these questions, described in more detail below, are:
1. Our exposure estimates are accurate. In fact, based on comparison's to Baker's own published work, reports by the American Water Works Association, and the Environmental Protection Agency's analysis for the Special Review, our exposure estimates appear to actually underestimate the scope and severity of the problem . This is because we used a very a conservative approach in calculating exposure estimates. We seasonally adjusted the mean exposure values to correct for over sampling in spring and summer periods of peak contamination. We only used data from finished tap water or drinking water sources water. We eliminated all detects over 50 ppb even if they were from drinking water source water. We did not included assumptions about the presence of metabolites in the absence of data although metabolites are present when the parent compound is found.
2. We did not fabricate a risk standard but instead used the widely accepted one in one million level of cancer risk as the benchmark against which drinking water risks were measured. The record is clear on the 10-6 negligible risk standard. As EPA Administrator Carol Browner stated in testimony before the Congress in September 1993:
"The reasonable certainty of no harm/negligible risk standard represents an upper bound risk of one in one million (10-6), calculated using conservative risk assessment methods."
3. Our methodology of adding risk from the triazine herbicides is not only correct but is being used by the EPA in its recently initiated Special Review of the triazine herbicides.
4. Our risk assessments and interpretation of the toxicology are also supported by the EPA in its Special Review of the triazines.
The following reply to criticisms of Tap Water Blues responds in order to each point made by Baker, Richards and Baker. In some cases, however, these criticisms are quite repetitive. To avoid repetition in our reply we answer several of Baker's points with one response; these cases are clearly noted.
Each response is preceded by Baker's criticism in bold and quotations. Where necessary the specific nature of Baker's criticism is clarified for the reader.
Weed Killers by the Glass
On August 17, 1995, the Environmental Working Group and a network of citizens groups across the Midwest released Weed Killers by the Glass, an analysis of herbicides in tap water in 29 midwestern cities. This first ever study of drinking water collected from peoples homes during the peak contamination period (May 15 through July 2, 1995) found atrazine in the drinking water of 28 out of 29 cities and cyanazine in the tap water of 25 cities.
In thirteen cities, average cyanazine levels exceeded the federal health standard for the entire 6 week period; in six cities, the six week average contamination level exceeded the atrazine MCL. In eight cities, more than half of the samples (taken every three days) exceeded either the atrazine maximum contaminant level (MCL), or the cyanazine lifetime health advisory. The peak level of contamination found in the study was more than 30 times federal health standards. In thirteen cities, peak contamination levels were at least triple federal health standards.
In the vast majority of communities, tap water was contaminated with multiple herbicides and toxic herbicide by-products. In more than two thirds of the cities, 21 out of 29, at least four, and as many as nine herbicides and toxic herbicide by-products were found in tap water sampled from people's homes.
On September 26, 1995, the results of tap water testing for the rest of the summer were released throughout the Midwest. These results show continued tap water contamination throughout the summer in nearly all of these communities. In fact, more samples (96 percent) were positive for atrazine during the month of July 1995, than for the period May 15 through July 1, 1995 (91 percent).
In some communities contamination continued to rise during July and into August. In Bowling Green and Alliance, Ohio, Fort Wayne and Muncie, Indiana, and Cedar Rapids Iowa, average contamination levels during the month of July were higher than the preceding six week period. In Springfield Illinois, cyanazine levels remained above the federal standard from May 27, through September 9, 1995. Paradoxically, levels of both atrazine and cyanazine in Springfield tap water began to rise in late August, long after the peak contamination period. This is most likely due to the fact that the utility cut the use of powdered activated carbon in late August. By September, atrazine in finished tap water in Springfield Illinois exceeded the federal MCL.