EPA Must Finish the Job of Protecting People from Dioxin

July 13, 2010

Dioxin: Dioxin Timeline

EPA'S Dioxin Assessment: No Safety Standard After Nearly Three Decades of Work

Dioxin and related dioxin-like contaminants form as byproducts of processes that involve chlorine and chlorine-containing substances, including pesticide manufacturing and municipal waste incineration.

Scientists first learned of dioxin's toxicity since the late 19th century, when German chemical industry workers exposed to it developed painful, oozing skin lesions known as chloracne. In the 1980s the U.S. Environmental Protection Agency (EPA) began a protracted process in order to issue a comprehensive human health risk assessment for dioxin. To date this process has included four Science Advisory Board (SAB) reviews (1984, 1988, 1995, and 2001) and a National Academy of Sciences review (2006). Plagued by delays forced by pressure from the chemical and defense industries, EPA has not yet completed that assessment.

EPA first declared 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, often referred to as dioxin) to be a probable human carcinogen in 1985. In 1997 the International Agency for Research on Cancer classified dioxin as "carcinogenic to humans," and in 2001 the National Toxicology Program, a government research agency that is part of the National Institutes of Health, also classified dioxin as a known human carcinogen. EPA has proposed updating its own classification to deem dioxin a definite "human carcinogen." Both the defense and chemical industries are objecting, continuing a decades-long pattern of trying to slow EPA's review and weaken its findings.

The shackling of EPA's efforts to protect public health from dioxin has a long history.

  • 1949: The first recorded case of human exposure in the United States occurs when an explosion at a Monsanto plant exposes more than 200 workers to dioxin-contaminated herbicides, causing severe skin lesions.

  • 1962-1970: The American military in Vietnam extensively sprays Agent Orange, a potent defoliant and herbicide contaminated with dioxin. Decades later, exposed veterans have an increased risk of developing diabetes and multiple cancers.

  • 1971: The entire town of Times Beach, Missouri, is exposed to dioxin from contaminated waste oils spread on dirt roads to suppress dust. Residents are later evacuated and the location is declared a Superfund site. In the same year, scientists at the National Institute of Environmental Health Sciences determine that fetal exposure to dioxin causes developmental abnormalities in laboratory animals, including cleft palates and kidney malformations.

  • 1976: Dioxin is released in an accident at a pesticide manufacturing plant in Seveso, Italy, contaminating people, air, soil and water. Decades later, scientists find adverse effects on reproductive function, including infertility and low sperm counts; lowered male/female sex ratio in newborns; changes in hormones; diabetes; cardiovascular effects; and elevated incidence of certain cancers (Baccarelli 2008; Eskenazi 2010; Mocarelli 2008; Pesatori 2003; Pesatori 2009)

  • 1978: Scientists at Dow Chemical publish the first study of dioxin carcinogenicity in laboratory animals (Kociba 1978). In the same year, the New York Times publishes a story on the plight of residents near Love Canal, N.Y., where industrial dumping released dozens of toxic substances, many suspected carcinogens. Dioxin and dioxin-like chemicals are among them.

  • 1982: EPA's National Human Monitoring Program begins testing Americans' tissues for the presence of dioxin and dioxin-like chemicals, polychlorinated dibenzo-p-dioxins and dibenzofurans (EPA 1987).

  • 1983: Responding to mounting public concern over dioxin contamination, Congress directs the EPA to launch the National Dioxin Study to determine the extent of pollution nationwide (Barnes 1986). The EPA survey focuses on plants producing herbicides, incinerators and waste dumps.

  • 1985: EPA publishes its "Health Assessment Document for Polychlorinated Dibenzo-p-dioxins," classifying dioxin as a known animal carcinogen and probable human carcinogen (EPA 1985). The EPA's Science Advisory Board reviews EPA's assessment, the first of five reviews of dioxin's toxicity and carcinogenicity that SAB conducts between 1985 and 2010. SAB agrees with the EPA's overall approach but calls the evidence for carcinogenicity of dioxins in humans "uncertain" (SAB 1985).

  • 1986: A joint publication of the EPA and the Midwest Research Institute based on EPA biomonitoring data concludes that dioxin-like pollutants "are prevalent in the general U.S. population" (Stanley 1986).

  • 1986: Research by Greenpeace and other activist groups uncovers collusion between EPA and the paper bleaching industry to keep secret the detection of dioxin in discharges from paper mills and in finished paper products (Van Strum & Merrell 1987; Weisskopf 1987).

  • 1987: Leaked documents from the American Paper Institute reveal industry's strategy to "Get EPA to 'rethink' dioxin risk assessment" so as to avoid liability and "unnecessary changes" in production processes prompted by "unsound scientific data" (Weisskopf 1987).

  • 1988-1989: The Science Advisory Board reviews for the second time EPA's dioxin assessment, presented in two draft documents: “A Cancer Risk-specific Dose Estimate for 2,3,7,8-TCDD” and “Estimating Exposure to 2,3,7,8-TCDD” (SAB 1989).

  • 1990: The Chlorine Institute, an industry trade group, starts a public campaign claiming that dioxin is "much less toxic to humans thasn originally believed," misrepresenting scientific opinion on its dangers (Roberts 1991).

  • 1991: EPA administrator Bill Reilly tells The New York Times: "We are now seeing new information on dioxin that suggests a lower risk assessment for dioxin should be applied" (Schneider 1991). EPA launches its second reassessment of dioxin.

  • 1992: The International Joint Commission (IJC) for the U.S. and Canada issues its Sixth Biennial Report on Great Lakes Water Quality, highlighting evidence that the developing fetus is likely more sensitive to toxic contaminants than adults are (IJC 1992).

  • 1994: EPA releases a draft Health Assessment Document for 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. The draft assessment concludes that these chemicals may be harmful at levels similar to those found in the general public, increasing the risk of cancer and causing potential damage to the immune, nervous and reproductive systems (EPA 1994).

  • 1995: EPA's Science Advisory Board completes its third review of EPA's dioxin assessment and agrees with the agency that “the margin of safety (between background exposures and levels of exposure where effects have been observed in test animals) for dioxin-like compounds is smaller than the EPA usually sees for many other compounds” (SAB 1995).

  • 1997: The International Agency for Research on Cancer declares dioxin a known human carcinogen (IARC 1997).

  • 1999: The United Nations Environment Programme warns that dioxin is a concern for all countries and drafts an international treaty that would ban, phase out or limit production of 12 "persistent organic pollutants" (POPs). POPs are chemicals that resist degradation, bioaccumulate through the food web and have a variety of adverse effects on human health and the environment. The United Nations POP list includes, among other substances, dioxin and other polychlorinated dioxins and furans (UNEP 1999).

  • 2000: EPA publishes its Draft Final Report on “Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-P-Dioxin (TCDD) and Related Compounds.”

  • 2000: EPA updates its 1994 draft and submits its revised Dioxin Reassessment to the SAB. This is the SAB's fourth review of the dioxin assessment and culminates in publication of an SAB review document in 2001.

  • 2000: The Food Industry Dioxin Working Group, representing beef producers, food processing, farming and retailing, urges the EPA to revise its dioxin assessment to lessen the chance that the assessment will "create a health scare."

  • 2003: The EPA asks the National Academy of Sciences (NAS) to review the agency's draft dioxin reassessment, “Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds."

  • 2003: The Food Industry Dioxin Working Group again pushes EPA to delay its dioxin assessment, calling for "additional research, data collection and more comprehensive government coordination... before any government action is contemplated."

  • 2005: Japanese scientists publish a study finding that TCDD and related dioxins cross the human placenta and are detectable in cord blood (Suzuki 2005). EWG scientists report finding dioxin-like compounds in cord blood samples from 10 of 10 newborns tested (EWG 2005), further confirming the transfer of a mother's dioxin load to her child in utero.

  • 2006: NAS publishes its report, “Health Risks from Dioxin and Related Compounds: Evaluation of the EPA Reassessment.” NAS issues a press release titled "EPA assessment of dioxin understates uncertainty about health risks and may overstate human cancer risk" (NAS 2006). In its 2010 draft, EPA has carefully considered the NAS recommendations by documenting alternative assessments; evaluating sources of uncertainty; and providing the rationale for its proposed decisions.

  • 2009: EPA releases its Science Plan for Activities Related to Dioxins in the Environment, promising to “accelerate the long-delayed scientific process to complete the assessment of the health risks dioxins pose to the public” and to publish a final report and assessment by the end of 2010 (EPA 2009).

  • 2009: EPA Administrator Lisa Jackson pledges strong federal action to clean up a dioxin-contaminated Dow Chemical site in Michigan and to accelerate the assessment of dioxins’ human health impacts (EPA 2009; EPA 2010; Melzer 2009).

  • May 2010: The agency publishes “EPA’s Reanalysis of Key Issues Related to Dioxin Toxicity and Response to NAS Comments.” The SAB initiates its fifth review of EPA's dioxin assessment.

  • June 2010: The SAB and EPA announce that the SAB review will be extended into Fall 2010.

  • The chemical industry and the Department of Defense submit extensive comments seeking to delay or weaken the proposed EPA standards for dioxin. Some of the submitted comments include:

    • General Electric Company: "In order for this newly-anticipated dioxin risk assessment scheme to quantify the risk of real-world mixtures of dioxins and dioxin-like compounds, the EPA should, at the very least, attempt to reduce some of the inherent uncertainty by dealing with the clear species differences in TEFs [Toxic Equivalency Factor]. Without such adjustments significant misallocation of limited societal resources will occur in order to address unfounded human health concerns regarding, for example, the safety of the US food supply.

    • American Chemistry Council: "EPA's failure to meet its self-imposed deadline for issuing the Draft Report should not circumvent the public's need for an adequate comment period, and the SAB's need for a complete picture of the relevant science before expert deliberations begin... We urge the Chair of the SAB Dioxin Review Panel to reschedule the July face-to-face meeting until at least two weeks after the close of the public comment period."

    • American Chemistry Council: submits extensive comments on "whether or not EPA consistently and appropriately applied a weight of evidence approach to dioxin toxicity and risk."

    • Department of Defense: "We disagree with the characterization for TCDD as “carcinogenic to humans” for all doses; and believe that two classifications should be presented... We suggest that “carcinogenic to humans” be limited to very high exposures and that lower exposures be classified as “likely to be carcinogenic to humans”.

References for the timeline

Baccarelli A, Giacomini SM, Corbetta C, Landi MT, Bonzini M, Consonni D, et al. 2008. Neonatal thyroid function in Seveso 25 years after maternal exposure to dioxin. PLoS Med 5(7): e161.

Barnes D, McBride A, Jaworski N, Harless R, Dupuy A. 1986. A status report on the U.S. national dioxin study. Chemosphere 15(9-12): 1401-04.

EPA. 1985. Health Assessment Document for Polychlorinated Dibenzo-P-Dioxins EPA/600/8-84/014F. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=38484

EPA. 1987. National Human Adipose Tissue Survey (NHATS). Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=55204

EPA. 1994. Health assessment document for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds EPA/600/BP-92/001c. Available: http://cfpub.epa.gov/ncea/CFM/nceaQFind.cfm?keyword=Dioxin

EPA. 2009. News Releases – Research. EPA Administrator Pledges Strong Federal Cleanup Presence at Dow Dioxin Site in Michigan and Accelerated Assessment of Dioxins’ Human Health Impacts. Available: http://yosemite.epa.gov/opa/admpress.nsf/48f0fa7dd51f9e9885257359003f5342/3ffa6e8e70763f28852575c20064b26b! OpenDocument

EPA. 2010. Seven Priorities for EPA’s Future. Available: http://blog.epa.gov/administrator/2010/01/12/seven-priorities-for-epas-future/

Eskenazi B, Warner M, Marks AR, Samuels S, Needham L, Brambilla P, et al. 2010. Serum dioxin concentrations and time to pregnancy. Epidemiology 21(2): 224-31.

IARC (International Agency for Research on Cancer). 1997. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Volume 69. Polychlorinated Dibenzo-para-Dioxins and Polychlorinated Dibenzofurans. Available: monographs.iarc.fr/ENG/Monographs/vol69/volume69.pdf

IJC. 1992. International Joint Commission. Sixth Biennial Report Under the Great Lakes Water Quality Agreement of 1978 to the Governments of the United States and Canada and the State and Provincial Governments of the Great Lakes Basin. Available: http://www.ijc.org/php/publications/html/6bre.html

Kociba RJ, Keyes DG, Beyer JE, Carreon RM, Wade CE, Dittenber DA, et al. 1978. Results of a two-year chronic toxicity and oncogenicity study of 2,3,7,8-tetrachlorodibenzo-p-dioxin in rats. Toxicol Appl Pharmacol 46(2): 279-303.

Melzer EJ. 2009. EPA pledges ‘expeditious action’ on Dow dioxin clean-up, but Superfund status not in the works. The Michigan Messenger 5/27/09. Available: http://michiganmessenger.com/19834/epa-pledges-expeditious-action-on-dow-dioxin-clean-up-but-superfund-status-not-in-the-works

Mocarelli P, Gerthoux PM, Patterson DG, Jr., Milani S, Limonta G, Bertona M, et al. 2008. Dioxin exposure, from infancy through puberty, produces endocrine disruption and affects human semen quality. Environ Health Perspect 116(1): 70-7.

NAS. 2006. EPA assessment of dioxin understates uncertainty about health risks and may overstate human cancer risk. Available: http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=11688

NTP. 2005. National Toxicology Program 11th Report on Carcinogens. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD); "Dioxin". Available: http://ntp.niehs.nih.gov/index.cfm?objectid=32BA9724-F1F6-975E-7FCE50709CB4C932

Pesatori AC, Consonni D, Bachetti S, Zocchetti C, Bonzini M, Baccarelli A, et al. 2003. Short- and long-term morbidity and mortality in the population exposed to dioxin after the "Seveso accident". Ind Health 41(3): 127-38.

Pesatori AC, Consonni D, Rubagotti M, Grillo P, Bertazzi PA. 2009. Cancer incidence in the population exposed to dioxin after the "Seveso accident": twenty years of follow-up. Environ Health 8: 39.

Roberts L. 1991. Flap Erupts Over Dioxin Meeting. Science 251(22 February): 866-67.

SAB. 1985. Technical Report of the Environmental Health Committee of EPA's Science Advisory Board Regarding a Draft Health Assessment Document for Polychlorinated Dibenzo-p-dioxins EPA-SAB-EHC-85-009. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/WebBOARD/advisoryreports?OpenDocument

SAB. 1989. Letter from Raymond C. Loehr, Ph.D., Chair, Executive Committee, Science Advisory Board to Mr. William Reilly, Administrator, US Environmental Protection Agency. EPA-SAB-EC-90-003.

SAB. 1995. Letter from Dr. Genevieve Matanoski, Chair, Science Advisory Board, to Honorable Carol M. Browner, Administrator, U.S. Environmental Protection Agency regarding Science Advisory Board's review of the Draft Dioxin Exposure and Health Effects Reassessment Documents, "A Second Look at Dioxin." EPA-SAB-EC-95-021. Available: http://cfpub.epa.gov/ncea/CFM/nceaQFind.cfm?keyword=Dioxin

Schneider K. 1991. U.S. Backing Away from Saying Dioxin is a Deadly Peril. New York Times, August 12 1991.

Stanley JS, Boggess KE, Onstot J, Sack TM, Remmers JC, Breen J, et al. 1986. PCDDs and PCDFs in human adipose tissue from the EPA FY82 NHATS repository. Chemosphere 15(9-12): 1605-12.

Suzuki G, Nakano M, Nakano S. 2005. Distribution of PCDDs/PCDFs and Co-PCBs in human maternal blood, cord blood, placenta, milk, and adipose tissue: dioxins showing high toxic equivalency factor accumulate in the placenta. Biosci Biotechnol Biochem 69(10): 1836-47.

UNEP. 1999. UNEP executive director urges global action on dioxin, and other POPs. New Report Issued on Dioxin, Furan Inventories. Available: http://www.chem.unep.ch/Pops/POPs_Inc/press_releases/pressrel-99/unepnr99-69.htm

Van Strum C, Merrell P. 1987. No Margin of Safety: A Preliminary Report on Dioxin Pollution and the Need for Emergency Action in the Pulp and Paper Industry. Washington, DC: Greenpeace.

Weisskopf M. 1987. Paper Industry Campaign Defused Reaction to Dioxin Contamination. Washington Post October 25, 1987 (Washington, DC).