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Health Implications of Perchlorate Ingestion. Summary of a National Research Council Review of other studies SCAG WPTF Presentation of February 10, 2005. Problem Definition. Perchlorate used for rocket fuel, fireworks, and flares Perchlorate ( ClO 4 - ) ion moves readily with water

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Health Implications of Perchlorate Ingestion

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Health implications of perchlorate ingestion l.jpg

Health Implications of Perchlorate Ingestion

Summary of a National Research Council Review of other studies

SCAG WPTF Presentation of February 10, 2005


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Problem Definition

  • Perchlorate used for rocket fuel, fireworks, and flares

  • Perchlorate (ClO4-) ion moves readily with water

  • 11 million people served water containing ClO4- at  4 μg/L (PPB)

  • 2002 EPA Risk Assessment suggested effect at 1 PPB

  • EPA offensive puts DOD and NASA on Defensive

  • Test, storage, production facilities across the US

  • National Research Council (NRC) asked to mediate & “Access health effects from perchlorate ingestion”


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Human Physiology of ClO4-

  • ClO4- competes (ineffectively) with Iodine ion or Iodide (I-) in thyroid uptake (transport)

  • Iodine need for normal hormonal activity, but is an element and cannot be manufactured by our bodies

  • Lack of iodine cause goiters, poor homeostasis, and neural defects in adults and developing offspring

  • Sources include iodized salt, sea salt, some sea foods

  • Typical US diet is about 5-10x excess

  • Fortunately (unless radioactive), body conserves I-


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Medicinal Uses of ClO4-

  • 50s/60s potassium perchlorate treatment of Hyperthyroidism (overactive thyroid)

  • Healthy people rapidly excrete KClO4- in urine

  • High dose, long term ClO4- depletes Iodine

  • Ecological (non-clinical) exposure

    • Does not cause hypothyroidism (underactive thyroid)

    • Does not alter thyroid function in healthy pregnancies/births

    • Results unclear on Attention Deficit Hyperactivity Disorder

    • Workplace exposure, probably no impact, but small N

    • Sample size too small to analyze for thyroid cancers

    • Insufficient data on sensitive subpopulations


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EPA Rodent Assessment

  • Subjective/inconsistent response

    • brain structure size

    • greater pup activity

    • thyroid cysts

  • Used to develop a No Adverse Effect Level

  • May confuse a high does toxic from low dose chronic

  • (High does may cause excessive cellular replacement resulting in replication mutations.)


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NRC Analysis

  • NRC believes body compensates (homeostasis) by first adjusting hormone (TSH) output, then enlarging the thyroid, then adverse outcome of hypothyroidism

  • Change in TSH is natural response to dose variabilitya pre-adverse effect response

  • Inhibition of iodide uptake is a more reliable and valid measure, it has been unequivocally demonstrated in humans exposed to perchlorate, and it is the key event that precedes all thyroid-mediated effects of perchlorate exposure.”


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Dose Assessment

  • 2002 EPA Risk Assessment

    • 0.03 ug/kg-day

    • as water ingestion about 1 PPB

  • NRC study with 10 fold safety

    • 0.7 ug/kg-day

    • about 20 PPB as water


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NRC Conclusions

  • Higher (than EPA) dose should be safe

  • Iodine depletion is a slow process, probably greater than most common sensitive exposure period

  • More studies, using quantitative end points, on pregnant primates and rodents should occur

  • More occupational exposure assessments

  • Concerned/sensitive individuals can take an additional (but unnecessary) step of monitoring body TSH or I levels, increase iodine intake, and/or use bottled water


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