1 / 8

Health Implications of Perchlorate Ingestion

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

Michelle
Download Presentation

Health Implications of Perchlorate Ingestion

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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 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.”

  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

More Related