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Health Implications of Perchlorate Ingestion

Problem Definition. Perchlorate used for rocket fuel, fireworks, and flares Perchlorate (ClO4-) ion moves readily with water11 million people served water containing ClO4- at ? 4 g/L (PPB)2002 EPA Risk Assessment suggested effect at 1 PPBEPA offensive puts DOD and NASA on DefensiveTest, storage, production facilities across the USNational Research Council (NRC) asked to mediate

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Health Implications of Perchlorate Ingestion

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    1. Health Implications of Perchlorate Ingestion Summary of a National Research Council Review of other studies SCAG WPTF Presentation of February 10, 2005

    2. 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”

    3. 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-

    4. 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

    5. 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.)

    6. 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 variability a 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.”

    7. 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

    8. 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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