{"id":8782,"date":"2019-05-07T09:39:30","date_gmt":"2019-05-07T14:39:30","guid":{"rendered":"http:\/\/blogs.edf.org\/health\/?p=8782"},"modified":"2019-05-07T09:39:30","modified_gmt":"2019-05-07T14:39:30","slug":"epas-safety-standard-perchlorate-water-kids-health","status":"publish","type":"post","link":"https:\/\/blogs.edf.org\/health\/2019\/05\/07\/epas-safety-standard-perchlorate-water-kids-health\/","title":{"rendered":"EPA\u2019s safety standard for perchlorate in water should prioritize kids\u2019 health"},"content":{"rendered":"

Tom Neltner, J.D.<\/a><\/u><\/em>,\u00a0<\/em>is Chemicals Policy Director and Maricel Maffini, Ph.D.,<\/em> Consultant<\/strong><\/p>\n

The Environmental Protection Agency (EPA) will soon propose a drinking water standard for perchlorate<\/a>. The decision \u2013 due by the end of May per a consent decree<\/a> with the Natural Resources Defense Council (NRDC)\u2014 will end a nearly decade-long process to regulate the chemical that has been shown to harm children\u2019s brain development.<\/p>\n

In making its decision, EPA must propose a Maximum Contaminant Level Goal<\/a> (MCLG) \u201cat the level at which no known or anticipated adverse effects on the health of persons occur and which allows an adequate margin of safety.\u201d[1]<\/a> It must also set a Maximum Contaminant Level (MCL) as close to the MCLG as feasible using the best available treatment technology and taking cost into consideration.<\/p>\n

To guide that decision, EPA\u2019s scientists developed a sophisticated model that considers the impact of perchlorate on the development of the fetal brain in the first trimester when the fetus is particularly vulnerable to the chemical\u2019s disruption of the proper function of the maternal thyroid gland. As discussed more below, the model was embraced by an expert panel of independent scientists through a transparent, public process that included public comments and public meetings.<\/p>\n

In April, a consulting firm published a study<\/a> critiquing EPA\u2019s model. The authors acknowledged the model as a valuable research tool but did not think it is sufficient to use in regulatory decision-making due to uncertainties. Therefore, the authors concluded that EPA should discard the peer-reviewed model and rely on a 14-year old calculation of a \u201csafe dose\u201d that does not consider the latest scientific evidence and has even greater uncertainties. They didn\u2019t offer other options such as using uncertainty factors to address their concerns about the model\u2019s estimated values.<\/p>\n

Given the importance of the issue and the risk to children\u2019s brain development, we want to explain EPA\u2019s model, the process the agency used to develop it, and the study raising doubt about the model.<\/p>\n

<\/p>\n

EPA\u2019s model quantifies the relationship between perchlorate and fetal brain development <\/strong><\/p>\n

The model involves two steps. First, it links a pregnant woman\u2019s exposure to perchlorate in the first trimester to the chemical\u2019s impact on levels of a thyroid hormone known as free T4 (fT4). Second, it links decreased fT4 levels to negative effects on IQ, \u00a0motor skills, cognitive and language development, reaction times in children. The result of the model is a quantitative relationship between maternal perchlorate exposure and harm to the fetal brain \u2013 which is important to understanding the risk posed by this chemical and to evaluating various regulatory options.<\/p>\n

In a November 2017 blog<\/a>, we applauded EPA\u2019s scientists for developing the model, noting that:<\/p>\n

A 1% shift in the population of women with hypothyroxinemia [low fT4] associated with perchlorate exposure would correspond to an increase of 4,000 impacted children; if there is a 5% shift, the number of impacted children born to hypothyroxinemic mothers would increase to 20,000.<\/p>\n

While these percentages appear small, they represent a significant number of potentially affected children since neurodevelopmental harm is likely irreversible. According to the model, the 1% shift corresponds to an exposure of 0.3 micrograms of perchlorate per kilograms of body weight per day (\u00b5g\/kg-bw\/day). The 5% shift corresponds to 2.1 \u00b5g perchlorate\/kg-bw\/day. These exposure levels do not include uncertainty factors or provide \u201can adequate margin of safety\u201d as required by law.<\/p>\n

EPA followed an extensive public process to develop the model<\/strong><\/p>\n

EPA went through an arduous process<\/a> that involved extensive review by independent scientists to develop the model. In 2013, its Science Advisory Board<\/a> (SAB) reviewed an agency proposal to develop an MCLG and concluded EPA needed to do more to protect fetal brain development. The SAB directed the agency to focus on the more sensitive measure of thyroid dysfunction called hypothyroxinemia (i.e., low fT4 levels) because of its expected impact on the developing brain.<\/p>\n

In 2016, EPA developed a Biologically-Based Dose Response Model<\/a> (BBDR) that focused on the third trimester and breast-fed infants. A peer review panel<\/a>, convened by the agency, provided positive feedback but challenged the agency to focus on the first trimester when the fetus is most vulnerable to hypothyroxinemia. In 2017, EPA rose to the challenge and refined the BBDR model for the first trimester after conducting a rigorous review of the science. It also drew on five distinct children studies showing a quantitative relationship between perchlorate exposure, low fT4 and harm to the developing brain.<\/p>\n

After another round of public comments, the agency reconvened the peer review panel. In March 2018, the panel gave what amounts to high praise<\/a> coming from independent scientists convened to be critical of the agency\u2019s work. It said:<\/p>\n

Overall, the panel agreed that the EPA and its collaborators have prepared a highly innovative state-of-the-science set of quantitative tools to evaluate neurodevelopmental effects that could arise from drinking water exposure to perchlorate. While there is always room for improvement of the models, with limited additional work to address the committee\u2019s comments below, the current models are fit-for-purpose to determine an MCLG.<\/p>\n

Critique of EPA\u2019s model claims too much uncertainty to be useful<\/strong><\/p>\n

The American Water Works Association, a 501c(3) technical and education organization representing drinking water professionals and utilities that would be affected by the rule, funded a consulting firm, Ramboll, to evaluate EPA\u2019s model. The authors of the report attempted to recreate the BBDR model and, in the study published in April 2019<\/a>, they concluded that:<\/p>\n

While the USEPA (2017) BBDR model represents a valuable research tool, the lack of supporting data for many of the model assumptions and parameters calls into question the fitness of the extended BBDR model to support quantitative analyses for regulatory decisions on perchlorate in drinking water. Until more data can be developed to address uncertainties in the current BBDR model, USEPA should continue to rely on the RfD [reference dose] recommended by the NAS [National Academy of Science] (USEPA, 2005) when considering further regulatory action.<\/p>\n

In essence, rather than offering a solution to address uncertainties, the authors proposed ignoring new, compelling evidence that perchlorate exposure during pregnancy harms the developing brain. Instead, they called for EPA to use an RfD developed in 2005 that was estimated using a study of healthy non-pregnant adults, that evaluated a less-sensitive effect and that had added a 10-fold intraspecies uncertainty factor to protect the most sensitive subpopulation, the developing fetus.<\/p>\n

The authors\u2019 conclusion is at direct odds with those made by EPA\u2019s independent peer-review panel through a multi-year transparent public process, which acknowledged the uncertainties but deemed them adequately addressed by the agency\u2019s model. The recommendations appear to be an unrealistic demand for perfection. EPA\u2019s model represents the \u201cbest-available, peer reviewed science,\u201d which the Safe Drinking Water Act<\/a> requires EPA to base its decisions upon.<\/p>\n

\u00ad\u00adTo provide an ample margin of safety, EPA should adopt an RfD of 0.03 \u00b5g\/kg-bw\/day <\/strong><\/p>\n

The graph below, copied from the Ramboll study, provides a helpful comparison between the various \u201cPoints of Departure\u201d (PoD) (green and blue bars) and the current RfD (red bar). According to EPA\u2019s Integrated Risk Information System (IRIS) Glossary<\/a>, a PoD is \u201cthe lower bound on dose for an estimated incidence or a change in response level from a dose-response model\u201d such as the one EPA developed. In contrast, the RfD is the lowest PoD \u201cwith uncertainty factors generally applied to reflect limitations of the data used.\u201d The green bars represent points of departure based on the five epidemiological studies in children that EPA and peer reviewers considered sufficient on which to build the model. The blue bars show the model\u2019s PoD for the 1% and 5% increase in pregnant women population becoming hypothyroxinemic without any additional factors<\/strong> to address uncertainties in the model. The red bar is the current RfD developed in 2005 that incorporates an uncertainty factor to protect the developing fetus<\/strong>.<\/p>\n

\"\"<\/a>
Figure 7 from Ramboll study<\/a>.<\/figcaption><\/figure>\n

Rather than discard the sophisticated model developed by EPA\u2019s scientists because of recognized uncertainties, the agency should use 0.3 \u00b5g\/kg-bw\/day as the PoD since this is the lowest dose for which the model shows a change in fT4 level. To calculate the RfD, we recommend an additional 10-fold safety factor based on four considerations:<\/p>\n

    \n
  1. The uncertainties<\/strong> identified by EPA, its independent review panel, and the Ramboll study\u2019s authors.<\/li>\n
  2. The reported variability in women\u2019s iodine consumption <\/strong>and trend towards lower iodine consumption in women of childbearing age<\/a>, that would make the risk from perchlorate exposure even greater.<\/li>\n
  3. The measured adverse effects may only be indicators for other developmental problems<\/strong>. While the effects identified by EPA represent endpoints that have been standardized and commonly measured, they are likely only a few of the potential additional effects that be occurring.<\/li>\n
  4. Most importantly, the developmental effects may be irreversible. <\/strong><\/li>\n<\/ol>\n

    Therefore, based on our calculations, the RfD should be 0.03 \u00b5g\/kg-bw\/day \u2013 about 20 times more protective than the current reference dose. We believe this RfD better \u201callows an adequate margin of safety\u201d as required under the law.<\/p>\n

    When EPA publishes the proposed MCLG by the end of May, we will learn whether EPA puts children\u2019s health first.<\/p>\n

    [1]<\/a> 42 U.S.C \u00a7300g-1(b)(4)(A)<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

    Tom Neltner, J.D.,\u00a0is Chemicals Policy Director and Maricel Maffini, Ph.D., Consultant The Environmental Protection Agency (EPA) will soon propose a drinking water standard for perchlorate. The decision \u2013 due by the end of May per a consent decree with the Natural Resources Defense Council (NRDC)\u2014 will end a nearly decade-long process to regulate the chemical …<\/p>\n","protected":false},"author":69548,"featured_media":8783,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[114081,44,5009,56093,114107],"tags":[104,68,91729,113924],"coauthors":[],"class_list":["post-8782","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-drinking-water","category-policy","category-health-science","category-industry-influence","category-perchlorate","tag-drinking-water","tag-epa","tag-perchlorate","tag-ramboll"],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/posts\/8782","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/users\/69548"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/comments?post=8782"}],"version-history":[{"count":0,"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/posts\/8782\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/media\/8783"}],"wp:attachment":[{"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/media?parent=8782"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/categories?post=8782"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/tags?post=8782"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.edf.org\/health\/wp-json\/wp\/v2\/coauthors?post=8782"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}