EWG Response to 'A Review of the Science, Methods of Risk Communication & Policy Recommendations in Tap Water Blues'
Setting the Record Straight
EWG Response to 'A Review of the Science, Methods of Risk Communication & Policy Recommendations in Tap Water Blues'
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.
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...
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.
In this section, Baker critiques what he sees as the major messages of Tap Water Blues.
Message 1. "Herbicides in drinking water are the greatest public health threat posed by pesticides today."
Baker provides no substantive criticism of this conclusion in his response. Instead, like so much else in his review, his criticism is comprised largely of his opinions of our public relations work and his claim that the risks from herbicides in drinking water are negligible. The fact that these risks are not negligible is discussed in detail below. More to the point, the EPA's recent actions against the triazines strongly support our conclusion.
On November 10, 1994, three weeks after the release of Tap Water Blues, the Environmental Protection Agency initiated a Special Review of the triazine herbicides, a process that will almost certainly lead to further restrictions on their use, and may ultimately lead to a ban. This Special Review represents the first time since 1988 that a regulatory action has been initiated against a pesticide on the basis of general risk to the public from contamination of food and water.
Message 2. "Federal drinking water standards are among the weakest of all national environmental regulations."
Baker basically agrees with our conclusion, as does the EPA. What Baker attempts to argue, nonetheless, is that drinking water standards, while weaker than the standards applied to the same herbicides in food, do not allow greater than negligible risks and that this "negligible risk has been achieved for the most part without any regulation."
The flaw with this assertion is that the risks from herbicides in drinking water are not negligible. Not only have existing regulations or lack thereof (depending on the herbicide in question) failed to achieve a negligible level of risk, they have in fact contributed to the significant risks from herbicides in drinking water faced by millions of people. As noted in Tap Water Blues and supported by the EPA, the current MCLs for atrazine and simazine, and the LHA for cyanazine, permit levels of contamination from 13 to 29 times greater than negligible for each individual chemical.
The EPA defines negligible cancer risks as those that do not exceed 10-6. For example, in testimony before Congress in September 1993, EPA Administrator Browner defined negligible risk as follows:
"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."
Tap Water Blues documents, and Baker does not dispute the fact that at least 3.5 million people in the Midwest are exposed to herbicides at risk levels that are ten to one hundred times greater than negligible (10-6). The EPA supported this conclusion in the documentation supporting the initiation of the Special Review, where risks from triazines in drinking water were calculated at 1x10-5. Contrary to Baker's claim, this special review was initiated precisely because the risks from these herbicides in food and water are greater than negligible.
Baker is simply wrong when he asserts that the current cancer risks from triazine herbicides in water are no greater than would be allowed under the negligible risk standard applied to residues of these herbicides in food. Even the EPA has since recognized this fact. On October 20, 1994, EPA Administrator Carol Browner ordered the water division of the EPA to accelerate efforts to harmonize drinking water standards and bring protection offered by drinking water standards in line with those of the pesticide program.
Message 3. "14.1 million people routinely drink water contaminated with five major agricultural herbicides (atrazine, cyanazine, simazine, alachlor, and metolachlor)."
As Baker clearly notes, Tap Water Blues underestimates the total population exposed to these herbicides in drinking water. In Baker's own words, "...far more than 14.1 million people undoubtedly ingest these herbicides in drinking water." Baker then dismisses this additional exposure as insignificant with the claim that "...most involve concentrations that are inconsequential with respect to human health effects." But Baker provides no data to support this conclusion.
In fact, the opposite is more than likely true. There are many areas with heavy herbicide use and poor drinking water monitoring where additional highly exposed populations certainly exist that were not identified in Tap Water Blues. Most of the state of Indiana is just one such example.
At the same time its is true that millions of additional mid-westerners beyond those identified in Tap Water Blues consume very low levels of triazine herbicides in drinking water drawn from the Great Lakes. These risks, while not "inconsequential", are at least well below levels that the federal government currently considers negligible.
What Baker argues throughout his critique, however, is that these low risk populations actually justify the high risk situations because more people are at low risk than high risk, and that therefore the average risk of the two populations is negligible. This rationalization is advanced relentlessly throughout the critique, even though this average risk is totally hypothetical, and not representative of the actual risk faced by anyone.
Message 4. "More than 3.5 million people in 120 cities and towns face cancer risks more than 10 times the federal cancer risk benchmark, based on annual exposure to these herbicides."
Here Baker makes several accusations that are repeated throughout the document. Rather than repeat our rebuttal of these points throughout our reply we address them here and reference the pages in Baker's critique to which they apply. They are, first, that we fabricated a risk standard(see Baker pages 1, 4, 14, 20), second, that additive risk cannot be calculated and that therefore combined standards cannot be set (see Baker page 7), and third, that we overstate the relative risks of the herbicides compared with other sources of cancer by only focusing on the exposed population (see Baker pages 4, 11, 22, 23, 31-36).
Point One (see Baker pages 1, 4, 14, 20).
Baker wrongly accuses us of fabricating a federal cancer risk standard that is five times more restrictive than any existing federal standard.
Baker is correct that we have added the exposure to the five herbicides in our study to calculate the cancer risk faced by the population drinking herbicide contaminated water. He is also correct that we have compared this total risk to the one in one million cancer risk standard. What he fails to mention is that our method of adding cancer risks is in accord with the EPA Cancer Risk Assessment Guidelines the recommendations of the National Academy of Sciences (NAS) Committee on Pesticides in the Diets of Infants and Children, and two previous NAS reports that explicitly examined risk assessment methods for complex chemical mixtures, including one that specifically studied this problem in drinking water: Drinking Water and Health: Volume 9.
Adding cancer risk as done in Tap Water Blues is widely accepted within the scientific community. As discussed previously, weakening the negligible risk standard from one in one million to five in one million depending on the number of chemicals in question (as Baker has done) is not.
What Baker cannot seem to comprehend is the overall purpose of the report, which is to point out the flaws and shortcomings of current drinking water standards and the current pesticide regulatory system. We have not fabricated a cancer risk standard, the standard is one in one million and we have used this standard. What we have done, however, is reveal the disingenuous nature of the standard when it is applied one chemical at a time. It is clear that the one in one million negligible risk standard is not a negligible risk standard at all when scores of chemicals are allowed into the water, air, and food supply each at a one in one million level of risk.
For example, 67 pesticides and metabolites have been detected in midwestern drinking water source water since 1987. At least 20 of these are carcinogens. If these 20 carcinogens are allowed in drinking water at a one in one million risk level, the overall risks from these 20 pesticides is 20 in one million, or 20 times the level that is deemed negligible. By extension of Baker's approach, a 20 in one million level of risk would be the appropriate negligible risk standard for these 20 compounds. Carrying this reasoning to its logical conclusion, the appropriate negligible risk standard for the 70,000 toxic chemicals in use today would be 70,000 in one million, or 7 in one hundred. Baker's approach has no medical or toxicological basis: simply put, a person's resistance to a carcinogen does not increase each time when he or she is exposed to an additional cancer causing chemical.
Point Two (see Baker page 7)
Baker then attacks our proposal for additive drinking water standards on the basis of their complexity. He argues that the additive risk from these toxicants is not measurable and is too difficult to calculate due to the infinite combinations of exposure levels that one might encounter in this mixture. And according to Baker, because these risk assessments are complicated, we should not attempt them, nor should we provide the public with added protection from known chemical mixtures in drinking water while scientists struggle to determine their true toxicity. EPA clearly believes that it is possible to set a drinking water standard based on total triazine exposure, and has already stated their intention to consider this approach. On October 17, 1994 the EPA rejected a petition by Ciba Corporation to weaken the current maximum contaminant level for atrazine from 3 ppb to 20 ppb. In the letter denying the petition, EPA administrator Carol Browner cited the need to examine the combined toxicity of the triazine herbicides along with their chlorinated metabolites:
"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.".
While the complexities that Baker cites do exist, they do not negate the reality of the risk that people face from drinking mixtures of these chemicals. In fact, it is precisely because scientists cannot accurately assess the risk from chemical mixtures in drinking water that we need to look toward strategies that reduce exposure of at the source, rather than blithely dismissing the risks as negligible, when in truth we do not know the toxicity of these mixtures.
It is true that the EPA has been loath to adopt the practice of adding cancer risk from related exposures (i.e. toxicants in the same media, or from the same source), even in obvious cases like the triazine herbicides where the toxicity of the pesticides is so nearly identical, and where they occur together in drinking water. This has begun to change, however. The Special Review of the triazine herbicides (atrazine, cyanazine, and simazine) will assess the combined risk and benefits of these herbicides, a first in the history of the EPA. The standard that will serve as a benchmark for negligible risk is the one in one million cancer risk standard.
Point Three (see Baker pages 4, 11, 22, 23, 31-36).
Finally, Baker voices one of his major concerns, which he calls the "paradox of inequitable distribution of negligible risks." In essence, Baker argues that it is legitimate for a subset of the population to be exposed to high risks if another part of the population is exposed to lower risks, and if enough low risk people can be averaged with the high risk population so as to make the total population risk seem insignificant. A comparison between Baker's use of his data and our use of Bakers data in Tap Water Blues is instructive on this difference in approaches.
Baker's own data for Ohio, Illinois, and Iowa -- which understate risk because they only look at one herbicide, atrazine, and do not quantify metabolites -- indicate that over five million individuals drink atrazine contaminated water that presents a greater than a one in one million risk. Baker argues, however, that the risk for these people is actually overstated, and that the appropriate way to characterize the risk to these five million exposed individuals is to average the risks they face with the risks faced by the additional 18 million people in these states who drink water with little or no contamination by these compounds. In essence, Baker argues that we can reduce the risks faced by the citizens of Columbus, if we simply average their risks with the citizens of Cleveland who drink water with little or no triazine contamination.
If widely adopted as policy, Baker's reasoning would justify exposing millions of people to unacceptably high levels of weed killers in tap water (or any other toxicant) any time one could identify an equally large number of people somewhere who are not. Baker is playing with numbers and ignoring lives. In contrast, the aim of the risk assessments in Tap Water Blues is to accurately characterize the risks faced by exposed individuals so that policies may be devised to protect them.
Message 5. "Across the Corn Belt, we estimate that at least 241,000 individuals are supplied by surface water sources where average annual herbicide levels exceed federal standards."
Here Baker argues that drinking water standards are strong, that they provide adequate protection from triazine herbicides in drinking water, that we ignored the strengths of these standards in our report, and that even people drinking water that is out of compliance with federal standards are unlikely to face any health risks.
Baker attempts to downplay the risk of the triazines by citing an outdated (1990) characterization of the toxicity of atrazine that makes no mention of the cancer risks that the EPA currently regards as the critical toxic effect of atrazine and the triazines as a class. This reference does not reflect current scientific thinking on the toxicity of the triazines, nor does it capture the EPA's concern over the inadequacies of current drinking water standards for the triazines.
On October 17, 1994, EPA Administrator Carol Browner pointed out several weaknesses of current drinking water standards (beyond the use of the safety factor methodology) in her denial of a Ciba petition to weaken the MCL for atrazine from 3 ppb to 20 ppb:
It is, for instance, possible that the Agency may have underestimated the risk from atrazine exposure in drinking water. EPA is assessing whether it should include the chlorodegradates of atrazine in its risk assessment. EPA based the MCL on the toxicity of atrazine alone, and this approach may have underestimated the actual risk posed by the use of atrazine. In other program areas the Agency has included the chlorodegradates when calculating the dietary risks of atrazine and other triazine compounds.
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 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 In contrast to Baker's view, the current EPA position is that atrazine and the triazine herbicides are so toxic and widely present in food and water that they warrant special regulatory review based on the cancer risk that they present to the general public and pesticide applicators. The EPA is conducting this special review using the quantitative cancer risk assessment methods employed in Tap Water Blues, not the safety factor methodology advocated by Baker.
We clearly acknowledge the existence of safety margins in the methodology used by the EPA's Office of Drinking Water. Tap Water Blues, however, makes three fundamental criticisms of this methodology:
- The safety factor method is inappropriate for these carcinogens and is not used to regulate carcinogens by any other regulatory division of the EPA;
- The safety factor approach applied to the triazines has been rejected by the Office of Pesticide Programs which has lead regulatory authority for pesticides at the EPA, and;
- The methodology produces weak health standards.
- Are far higher (up to 29 times higher for just one herbicide, cyanazine) than allowed from these same herbicides in food;
- Are particularly inappropriate because most exposure occurs via water;
- Do not take into account exposure to multiple chemicals with similar toxicological properties, and;
- Result in MCLs, or legal levels of contamination that are not based on the most sensitive endpoint (cancer) observed in animal studies, but instead on a health endpoint that is in many ways irrelevant to the toxicity and potency of the triazine herbicides.
Messages 6 and 7
"In the Corn Belt, an estimated 65,000 infants drink these herbicides from birth via infant formula reconstituted with contaminated tap water."
"Earlier studies have shown that children are particularly susceptible these chemicals."
Baker's principal contention here is that these statements are meaningless and designed to frighten the public.
Baker is wrong on both counts. These statements are neither meaningless nor designed to frighten the public. (Interestingly, one of them -- "Earlier studies..." -- was not even in Tap Water Blues, but was taken from a press advisory.) They are designed instead to educate the public on the reality of herbicide contaminated drinking water, and the potential risks that this contamination presents to children.
As our study shows, infants and young children are exposed to a disproportionate amount of lifetime exposure simply because they drink more water per unit of bodyweight. And as Baker acknowledges in his critique,
"... children are probably more susceptible to all chemicals than adults are."
Meanwhile, two years after the National Academy of Sciences recommended that pesticide regulatory standards be strengthened explicitly to protect children, not a single food or drinking water standard for pesticides has been changed to meet this goal. As it stands today, neither drinking water nor food standards for pesticides make any specific accommodation for the sensitivity or higher levels of exposure faced by infants and children.
In attempting to support his claim that it is safe to feed infants and young children herbicide contaminated tap water, Baker makes a very revealing analogy between atrazine and aspirin. Baker goes to great lengths here and elsewhere (page 38) in his critique to compare the acute toxicity of aspirin with the acute toxicity of atrazine, although no scientist that we are aware of considers the acute toxicity of atrazine or aspirin a serious issue. On these grounds alone the comparison is completely irrelevant. More seriously, however, it reveals an ignorance or lack of concern about the potential health risks that children face when they consume chemicals that are known to be toxic but are thought to be safe for children based on the results of studies in sexually mature animals and their safe use in human adults.
As it turns out, the relevant health risk for children from aspirin is not acute toxicity, but Reyes syndrome, a condition that kills over half of the children it afflicts. Notably, the link between aspirin and this fatal condition in children was not uncovered by routine animal testing, but was discovered only after children died from consuming aspirin at levels that were previously thought to be safe. Today aspirin in not recommended at any dose for children with a fever.
The lesson that aspirin and Reyes syndrome teaches us is not Baker's claim that all toxic substances are safe for children if only the doses are small enough. Instead, the lessons are twofold; first, that some substances are not safe for children at any dose, even when they are safe for adults; and second, that in some cases no amount of animal testing will reveal these differences, as was the case with aspirin.
That is why, in 1993, the Committee on Pesticides In The Diets of Infants and Children of the National Academy of Sciences concluded that, " Profound differences exist between children and adults...these differences can affect the toxicity of pesticides in infants and children," and that "in the absence of data to the contrary, there should be a presumption of greater toxicity to infants and children."
Quality of the Science
Point 1. Baker argues that we overestimate risk because we have not used a time-weighted average. He cites one example in one year, Honey Creek in 1986, from which he implies that we have overestimated risk in the entire report by a factor of two. He argues that we have misanalyzed USGS data, and claims that he offered to help us with his data.
All risk and exposure estimates in Tap Water Blues are based on seasonally adjusted averages that correct for any seasonal sampling biases in the data. This methodology was also used by the American Water Works Association in their 1994 report, Seasonal Pesticide Variations in Surface Water Systems. The results of this AWWA report indicate that EWG may have significantly underestimated the extent of herbicide contamination. More importantly, our methodology and overall data quality criteria yielded estimates of exposure and risk 29 percent lower than comparable data published by Baker or data published by Ciba using Baker's methodology. The methodology used in Tap Water Blues was reviewed by Don Goolsby, Chief of the USGS Midcontinent Herbicide Program, and by George Hallberg of the University of Iowa Hygienic Laboratory.
In collaboration with Ciba, the manufacturer of atrazine, Baker has published extensive analyses of atrazine exposure through drinking water in Iowa, Ohio, and Louisiana. We have compared the data used in Tap Water Blues with comparable Baker/Ciba data for 18 cities or drinking water sources in three states serving a population of over 3 million people. This data show the problem to be even greater than EWG estimates. For these 18 cities or drinking water sources, Baker/Ciba estimates that the average atrazine concentration is 1.15 ppb, while the average atrazine concentration used for these same cities and sources in Tap Water Blues is 0.82 ppb, nearly one third lower than the average Baker/Ciba estimate (Table 1). In terms of the exposed population, Tap Water Blues estimates are lower for 13 of the 18 cities accounting for 84 percent of the affected population. In two of the remaining five communities where our analysis shows higher results than Baker, our analysis was based on more accurate and recent data, either collected by the water utility (Columbus) or the United States Geological Survey (Alum Creek, OH).
Finally, Baker has neither offered to help us with his data, nor made these data available publicly to us in any form. Some of these data, which were collected for the EPA, have been placed in STORET. The remainder have not been released except in summary published form. The Environmental Working Group requested these data via telephone in late 1993 and again in early 1994. Both requests were denied.
Table 1: Ciba's estimates of atrazine contamination are higher than those in Tap Water Blues.
|City/Source||Population||Ciba Estimate (PPB)||EWG Estimate (PPB)||EWG Estimate as a Percentage of Ciba Estimate (PPB)|
|Akron, OH (Lake Rockwell)||280,000||0.56||0.14||25%|
|Columbus, OH (Scioto River)||320,000||2.02||0.67||33%|
|Des Moines, IA||191,003||0.37||0.13||35%|
|Mississippi River, LA||1,500,000||1.2||0.45||38%|
|Iowa City, IA||51,577||0.83||0.38||46%|
|Council Bluffs, IA||56,699||0.25||0.12||48%|
|Rathbun RWA, IA||16,888||2.3||1.95||83%|
|Maumee River, OH||57,000||1.5||1.97||131%|
|Columbus, OH (Big Walnut Ck)||320,000||0.91||1.34||153%|
|Sandusky, River, OH||44,000||1.73||2.84||164%|
|Alum Creek, OH||45,000||0.62||1.93||311%|
Sources: Wiles, Cohen, et al. "Tap Water Blues," Environmental Working Group, Washington, D.C. 1994.
Richards, et al. 1994. Atrazine exposures through drinking water: Exposure assessments for Ohio, Illinois, and Iowa. Proceedings of the Fourth National Conference on Pesticides. New Directions in Pesticide Research, Development, and Policy. Virginia Polytechnic Institute.
D. Tierney, et al. 1993. Atrazine and drinking water sources: An exposure assessment for popultions using the greater Mississippi River system. Ciba-Geigy Corporation Technical Report 2-93.
Point 2. Baker claims that the "statewide" average risks presented in Tap Water Blues are too high because we used simple averages and did not weight the calculations by population. Baker then accuses us of "...intentionally introducing high biases into the statewide averages."
We did not, as Baker asserts, intentionally, or through any oversight, introduce high biases into statewide averages in this report. In fact, as will be discussed below, we intentionally understated the actual levels of contamination and risk in order to protect ourselves against criticisms that we were biased in favor of protection of the public health. Although Baker correctly observes that some statewide averages would be lowered slightly if population weights were used in the calculations, he fails to point out in other cases and for other states they would be raised. For example, the simple statewide average lifetime risk for the state of Kansas reported in Tap Water Blues was 8.1 X 10-6. Were we to compute the statewide average using Baker's population weighted average, the result would be a higher estimate -- 9.6 X 10-6.
In other states because of data availability, our averages were based on data sets which clearly underestimated risks for much of the population. For example, many small and large towns in Louisiana use the Mississippi River for drinking water. Most smaller systems do not use any sort of carbon filtration to reduce contaminant levels. Our statewide risk assessments for Louisiana, however, were based on finished water samples from larger systems such as East Jefferson Parish and New Orleans, which use Powdered Activated Carbon (PAC) to reduce herbicide levels delivered tap water. As a result, for the state as a whole, our estimate of risks is clearly low. The same is true for Kentucky and Nebraska, where we based the statewide average lifetime cancer risks on data from large systems treating their water with PAC.
The important issue, of course, is not which method produces slightly higher or slightly lower statewide average exposure numbers; the important issue is the risk that people actually face, and for purposes of this review, which methodology provides the most meaningful estimate of real world risks for people living in communities with contaminated water. To answer this question risk estimates must be presented at the water system level, as they were in Tap Water Blues.
Contrary to Bakers assertion that we intentionally bias our exposure calculation to produce inflated risk estimates, virtually all of the estimates of cancer risk in Tap Water Blues are likely to underestimate the true risks faced by the population drinking herbicide contaminated water because:
- For the vast majority of the exposed population, chlorinated herbicide metabolites were not included in our exposure calculations due to the absence of data, even though these metabolites are certainly present and have similar toxic properties as the parent compound.
- All herbicide detections over 50 ppb were excluded when calculating averages, even if the detections were in drinking water source water; this amounted to the elimination some 600 detections out of 15,000 used from STORET;
- We made no compensation for tests with poor limits of detection. For example, 49 percent of atrazine non-detections in STORET were from samples where the limit of detection was 1 ppb. In contrast, the U.S. Geological Survey currently uses methods with a limit of detection of 0.05 ppb. In cases where no detections were reported because of high detection limits, we assumed that no herbicides were present even when we had substantial evidence indicating that herbicides were present.
- We made no compensation in risk assessments for peak periods of exposure when contamination exceeds the MCL, for the sensitivity of children or for the potential synergistic effects of the common mixtures of herbicides in drinking water throughout the Midwest.
Point 3. Baker claims that when calculating "statewide" average risks we were ambiguous about the populations represented and used only the most contaminated communities in the state.
Baker's assertion that we were ambiguous about the populations used when calculating statewide averages is simply wrong. As Baker himself admits, "...they cannot be accused of failing to document their methods." In each of the ten states analyzed, we went to great lengths to describe how the statewide risk estimates were calculated, making clear that they only apply to the population whose drinking water is actually contaminated with herbicides. Groundwater drinkers, those supplied by the Great Lakes, and communities for which we had no data were clearly excluded from the analysis. At no point did we imply that these statewide averages applied to every individual in that state -- we clearly indicated which communities were affected and what the risks were in those communities.
Baker believes we should average those people who have no herbicides in their drinking water into the statewide cancer risk estimates, as though the absence of exposure for these individuals would somehow lower the risk for those who are exposed. In our view, it is far more useful and relevant to describe the size of the exposed population and then to describe the risks to this population, as we did in the report.
It would be unfortunate if reporters, scientists, or policymakers were "confused" by these estimates; however, we have no evidence that this confusion actually occurred.
Point 4. Baker argues that we fabricate a one-in-one million risk standard, resulting in inflated perceptions of risk. He then continues by arguing that the proper basis of comparison for the five herbicides would be the risk of five in one million.
See pages 7 and 8.
Point 5. Baker argues that data presentation generally precludes calculation of estimated cancer occurrences for towns, cities, and states.
The data presented in Tap Water Blues have not precluded Baker or any other researcher from estimating cancer occurrence for towns, cities, and states. The data are presented in terms that an individual can understand: my increased risk of getting cancer is X in a million. In fact, it is Baker's analyses, which combine exposed and non-exposed populations into one "average" risk, that completely preclude any meaningful understanding of risks or exposure at the individual or local level.
Further, Baker's assertion that we have attempted to fool the media with this approach does not stand up to the facts. We have received over 1,000 copies of articles from the popular media and have not seen a single example of where the implications of risk estimates determined by EWG were misunderstood or misused as implied in Baker's review.
Point 6. Baker argues that we present the data in forms lacking toxicological context.
Baker argues that simply giving the percentage of positive herbicide detections has no meaning, and no toxicological significance. Besides being scientifically inaccurate, this line of reasoning presumes that people have no right to know how often their drinking water is contaminated with herbicides, a line of reasoning we reject.
As Baker would no doubt agree, there are at least two characteristics of exposure that influence the human health risks posed by a substance -- the dose, and the number of times (or length of time) that the dose is received. Presenting information on the frequency of contamination is clearly relevant in this context. Moreover, the EPA's standard cancer risk assessment models (being used for the triazines in the ongoing Special Review) assume a linear cancer model -- that is, that any exposure poses some level of increased risk. Although the risk of low level contamination may be small, it may be a risk that people choose to avoid. They can only make that choice, however, if they know whether and how often their water is contaminated.
Point 7. General failure to provide context for data.
Baker claims that the report is about cancer, but that we do not estimate cancer occurrences.
First, Baker is mistaken in his analysis that the report is "about cancer". The report is about exposure to herbicides, and the numerous health risks -- birth defects, cancer, disruption of the endocrine and hormonal systems -- attributable to pesticide exposure. As noted in response to point 5, when we presented risk information, we presented it in the most meaningful format for those assessing risks in the affected areas.
Baker complains that we do not mention background levels of cancer, and that we do not document the population of the corn belt.
True. Instead, we use the more meaningful number -- the total risk to individuals of exposure to these chemicals. This is an improvement over approaches like Baker's, which obscure these risks (which are avoidable through sound public policies), in a blizzard of irrelevant statistics. Simply put, the number of individuals getting lung cancer has no bearing on the risks from exposure to pesticides in drinking water. Again, the media has had no problems placing this risk in the proper context.
Point 8. Implication of greater significance of the risks than actually warranted.
There are no scientific issues raised in this point.
Point 9. Inappropriate comparison to drinking water standard and health advisories.
Again, Baker has not grasped the overall thrust of the report, which is that current drinking water standards are inadequate because they are based on suspect interpretations of toxicity of the triazines, and because monitoring and enforcement ignores peak periods of exposure. We, like the EPA in its recent Special Review, do not believe the the acute effects of the triazines are a health issue. Thus, Tap Water Blues contains no discussion of these effects nor any comparison with short term health standards that Baker presents in his critique.
We argue two points. First, lifetime standards (the MCL) should be based on the most sensitive chronic effects (cancer) and they are not. Because they are not, the current standards are too weak and allow excessive risk. Second, the entire way in which chronic risk and compliance with this standard is enforced is suspect because the standard makes no allowance for sustained peak periods of exposure that exceed the liftime health standard (MCL or LHA) year after year.
We know of no other federal contaminant standard where sustained and repeated exposures at levels in excess of the supposed standard are condoned. We consider this a major flaw in the way that standards are conceived, and intended Tap Water Blues, to illustrate the frequency and scope of exposures that violate MCL's for extended periods of time, but are nonetheless considered legal.
Browner, Carol. Letter to Emilio Bontempo, Ciba-Geigy Corporation. October 17, 1994. RE: Petition for reconsideration and administrative stay of drinking water regulations.
Ciba-Geigy Corporation. 1993. Summary of Toxicologic Data on Atrazine and the Chlorotriazine Metabolites. Attatchment to Petition to the Environmental Protection Agency For Reconsideration of and Request for Stay of the MCL and MCLG for Atrazine. November 16; Environmental Protection Agency. 1994. Atrazine, Simazine and Cyanazine: Notice of Initiation of Special Review. November 10.Environmental Protection Agency. 1994. Atrazine, Simazine and Cyanazine: Notice of Initiation of Special Review. November 10. p. 5.
Environmental Protection Agency. 1994. Atrazine, Simazine and Cyanazine: Notice of Initiation of Special Review. November 10. p. 33.
Environmental Protection Agency. 1994. Atrazine, Simazine and Cyanazine: Notice of Initiation of Special Review. November 10. p. 34.2. Inside EPA Weekly Report. 1994. Browner pushing for harmonization of Water Office, OPPTS cancer risk. October 28, p. 15.
EPA. 1986. 51 FR 33992. Guidleines For Carcinogenic Risk Assessment. Washington, DC.
Frey, M., J.A. Roberson, and J. DeMarco. 1994. Seasonal Pesticide Variations In Surface Water Systems. Presented at the American Water Works Association Conference,.3. Ciba-Geigy Corporation. 1992. A Review of Surface-Water Monitoring for Atrazine in the Mississippi River near Baton Rouge-St. Gabriel, Louisiana. Technical Report 1-92.
National Research Council, National Academy of Sciences. 1993. Pesticides In the Diets of Infants and Children. Washington, DC. pp. 3, 9.
National Research Council. 1993. Pesticides In The Diets of Infants and Children. Washington, DC. p 307.
National Research Council. 1989. Drinking Water and Health Volume 9: Selected Issues In Risk Assessment, Washington, DC.
National Research Council. 1988. Complex Mixtures: Methods For In Vivo Toxicity Testing. Washington, DC.
Richards, P.R., D. Baker, B. Christiansen, and D. Tierney. 1994. Atrazine Exposures Through Drinking Water: Exposure Assessments For Ohio, Illinois, and Iowa. Proceedings of the Fourth National Conference on Pesticides: New Directions In Pesticide Research, Development, and Policy. Blacksburg, VA.