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Final Version

  1. 1. Current Issues in Environmental Regulation and Public Health: PERCHLORATE Carter Franz Francesco Ramos
  2. 2. Table of Contents I. Executive Summary ............................................................................................. ii II. Physical and Chemical Properties ....................................................................... 1 III. Common Commercial Applications .................................................................... 4 IV. Commercial and Natural Production ................................................................... 6 V. Environnemental Occurrence .............................................................................. 13 VI. Health Effects ................................................................................................... 16 VII. Regulation......................................................................................................... 20 VIII. Treatment Options........................................................................................... 22 References ................................................................................................................ 29   
  3. 3. Tables Table 1: Physical and chemical properties of perchlorate ............................................................................ 3 Table 2: Annual estimated use and production of perchlorate compounds .................................................. 4 Table 3: Estimated annual perchlorate releases from commercial and natural applications......................... 6 Table 4: Selected perchlorate sources, releases and detections .................................................................... 8 Table 5: Selected DOD sites with perchlorate detections ............................................................................. 9 Table 6: Measured perchlorate concentration in common foods ................................................................ 15 Table 7: Relative source contributions remaining for water based on TDS for various sub-groups .......... 15 Table 8: State drinking water regulations ................................................................................................... 20 Table 9: Relative source contributions of perchlorate in drinking water for vulnerable subpopulations ... 21 Table 10: Applicability of common treatment technologies ....................................................................... 23 Table 11: National cost of federal regulation.............................................................................................. 28 Figures Figure 1: Molecular geometry of perchlorate ............................................................................................... 2 Figure 2: Energy for a chemical reaction ...................................................................................................... 3 Figure 3: Locations of known users and manufacturers of perchlorate ........................................................ 8 Figure 4: Fate and Transport of perchlorate in groundwater aquifer and estimated residence time ........... 10 Figure 5: Schematic of perchlorate plume at Stringfellow Superfund Site................................................. 11 Figure 6: Pathway of Tronox plume in the south west United States ......................................................... 12 Figure 7: Suspected or known perchlorate releases and detections ............................................................ 14 Figure 8: Percent of total U.S. perchlorate detections found in each state ................................................. 14 Figure 9: Perchlorate mode of action and adverse affect when ingested .................................................... 17 Figure 10: The thyroid and its role in hormone secretion ........................................................................... 18 Figure 11: Progression of perchlorate regulation at the federal level in the United States ......................... 20 Figure 12: Quantification and calculations for toxicological effects of perchlorate ................................... 21 Figure 13: Schematic representation of the ion exchange between perchlorate and chloride .................... 23 Figure 14: Ion exchange treatment for perchlorate removal ....................................................................... 24 Figure 15: Schematic representation of a membrane filtration system for the treatment of perchlorate .... 25 Figure 16: Enzymatic pathway of the dissimilatory perchlorate reducing bacteria (DPRB) ..................... 26 Figure 17: Phytoremediation of perchlorate. This process is an emerging technology for perchlorate remediation ................................................................................................................................................. 27
  4. 4. I. Executive Summary On October 8, 2009 the U.S. Environmental Protection Agency (EPA) accepted the last public comment (out of 22,000) regarding a federal drinking water regulation for perchlorate, a ‘candidate contaminant’ of the EPA’s since 1998. Perchlorate, a common constituent of solid rocket fuel, has been linked to adverse health effects related to the hormonal homeostasis of the thyroid gland in mice. Known to be released in large amounts nearby ground and surface water supplies at U.S. Department of Defense, NASA research, and manufacturing sites, perchlorate was chosen for evaluation to determine whether or not it causes adverse health effects in humans at environmentally present concentrations. If so, a regulatory standard will have to be set which would require municipal entities to treat water supplies to meet that standard. This report outlines the chemical and physical properties that make perchlorate popular among defense contractors and other users, and those properties that make it problematic for environmental remediation efforts and finally those that possibly cause adverse health effects in vulnerable populations. Perchlorate rose in popularity beginning with the Second World War because of its oxidizing potential. Subsequently, it was used in munitions, rocket launchers, fireworks and other related uses. Commercially viable only as a solid salt, 90% of perchlorate demand is for ammonium perchlorate, and these salts are highly soluble in water and unable to adsorb to soil, making them extremely mobile in aqueous medium. The time period since perchlorate was established as a candidate for regulation, new research has yielded the following conclusion regarding the health effects of perchlorate: The vulnerable population group is the fetuses of iodine deficient pregnant women exposed to concentrations of perchlorate in water of over 15µg/L (ppb). This comes after a body of animal studies on mice was summarily discounted as non-analogous to healthy adults and adolescents because of differences in the pituitary gland. In 2005 a Center for Disease Control study concluded that higher urinary perchlorate concentrations were a positive predictor of unbalanced hormonal behavior regulated by the thyroid gland in iodide deficient women. However, they noted that the hormonal behavior was within healthy range, and that there was no precedent in the research indicating those urinary levels of perchlorate would cause any adverse health effects. Various technologies are available to treat perchlorate, and depending on whether or not a regulatory standard is set, 3.4% or 1.4% of the nation’s public water supply would require adoption of these unconventional treatment technologies. The cost implications of setting a Federal drinking water limit for perchlorate are that compliance would cost 2.1 billion USD with a maximum contaminant level (MCL) of 4 ppb and 100 million USD with an MCL of 24 ppb. Regulating perchlorate would cost the nation less than previous drinking water standards, and the costs would fall on a small number of municipalities and private entities. We conclude that perchlorate is an environmental contaminant which can cause negative health affects at high doses, especially to the fetuses of iodine deficient pregnant women. While the cost of implementing a federal drinking water standard is low compared to previous limits, the cost would fall upon a few individuals. Clearly, there are many stakeholders and we hope the political process serves both sides of the debate fairly. If a regulation is put in place, we would recommend the ion exchange method as the most reliable and capable of removing perchlorate from public drinking water systems.
  5. 5. INTRODUCTION erchlorate is a highly soluble anion used in solid P rocket fuel and found naturally in the environment. Previous disposal methods at U.S. “As with any Department of Defense and other user sites consisted of dumping perchlorate salts or liquid new regulatory waste into the Earth untreated. In the late 1990’s standard, there is perchlorate was detected in high concentrations in public water supplies of the American south west and subsequently debate in the throughout the entire United States. Public health officials public sphere as were concerned that ingestion of perchlorate may cause hypothyroidism, a condition characterized by an underactive to whether or not thyroid and a slowing metabolism. The EPA added a national perchlorate to its candidate contaminant list in 1998, and the report that follows is a summary of research concerning the drinking water health effects, regulatory framework, and environmental limit for remediation efforts associated with perchlorate up to 2009. As with any new regulatory standard, there is debate in the public perchlorate sphere as to whether or not a national drinking water limit for would improve perchlorate would improve the health of the population. The first section will elaborate on the chemical and physical the health of the properties governing the behavior of perchlorate. These population.” properties are the basis for understanding perchlorates nature as a commercial commodity, a persistent ground water contaminant, and a potential human health concern. II. Physical and Chemical Properties of Perchlorate Molecular Geometry. Figure 1 shows the sp3 tetrahedral arrangement of the perchlorate anion, which consists of one chloride bonded to four oxygen atoms. Because of this geometry perchlorate has a large ionic volume and low charge density. Therefore, it is a poor complexing agent with cations in aqueous solutions. This low association with cations makes perchlorate highly soluble and mobile in aqueous environments, and prevents bioaccumulation and soil sorption. This contributes to perchlorates persistence in aquifer plumes, and confounds 1
  6. 6. environmental engineers because sodium and potassium perchlorates precipitation and sorption are ruled out as (Urbansky, 1998). Perchloric acid (HClO4) treatment options (Srinivasan, 2009). is miscible in water and has an octanol- Perchlorate’s ionic radius is similar to that water partition coefficient of -4.63 (EPA, of the iodine anion. When in the 2008). Perchlorate is non-volatile and does bloodstream, perchlorate competes with not bind readily to mineral surfaces, which iodine for uptake into the thyroid gland, indicates that perchlorate will travel rapidly which can ultimately reduce radioiodine over soil with surface water runoff or be uptake and disrupt the normal hormone transported through soil with infiltration secretion of the thyroid when ingested in (ATDSR, 2008). Therefore, adsorption large doses. techniques used in water treatment plants are ruled out as a possible treatment option. (1) NH4ClO4(s) water NH4+ (aq) + ClO4- (aq) Subsequent discussion will talk about the commercial applicability of perchlorate containing salts, but the following statement makes an important distinction: “Given that perchlorates completely dissociate at environmentally significant concentrations, their cations are, for all practical purposes, spectators in the aqueous fate of perchlorate. Figure 1: Molecular Geometry of Therefore, the environmental fate of Perchlorate perchlorate salts is dominated by the Perchlorates tetrahedron geometry contributes perchlorate ion (ATDSR, 2008).” This to the large ionic volume and low charge density of ClO4 -. The negative charge is property is important, because equally distributed among the 4 outer oxygen environmental engineers are concerned with atoms. Consequently, it is a poor complexing the removal of perchlorate, and therefore the agent and highly soluble in aqueous perchlorate anion, from the environment environments, making it difficult to remediate (especially drinking water sources). by conventional methods. Research shows that this task is further Image: CAS, 2009 complicated by the chemical kinetics of perchlorate. Thermodynamics and Kinetics. Figure 2 Solubility. Perchlorates are commercially depicts the ‘energy hump’ that reactants in a viable as solid salts, in white or clear crystal chemical reaction must surpass to become form stored at ambient temperature. These products. Perchlorate represents the highest salts fully dissociate in water (Equation 1) oxidized form of chlorine (+7), and has a and some organic solvents, with solubility’s high reduction potential. Perchlorate can ranging from 2.06 x 104 to 2.10 x 106 mg/L react explosively at high temperatures, and in fresh water at 25ºC, and 1.00 x 101 to is a powerful oxidant when combined with 1.82 x 106 mg/L in standard organic solvents fuel sources. Ammonium perchlorate, the (See Table 1). Log octanol-water partition most widely produced perchlorate salt, coefficients (log Kow) are -5.84 for thermally decomposes at temperatures of ammonium perchlorate, and -7.18 for 439ºC, and then combusts in a self- 2
  7. 7. propagating manner (CDTSC, 2005). Standard reduction potentials show that the reduction of perchlorate to (Eq. 2) chloride, or (Eq. 3) chlorate, is thermodynamically favorable (Urbansky, 1998). (2) ClO4- + 8 H+ + 8 e- ↔ Cl- + 4 H2O -----E° = 1.287 V (3) ClO4- + 2 H+ + 2 e- ↔ ClO3- + H2O E° = 1.201 V Though perchlorate is thermodynamically favored to be easily reduced, it is highly non-reactive in aqueous Figure 2: Energy for a Chemical Reaction  solution at ambient temperatures. “The low This general graph depicts the transgression of a chemical reactivity is a matter of kinetic lability rather reaction. In the case of perchlorate as a reactant, it has than thermodynamic stability (Urbansky, high activation energy, so it takes a large amount of 1998).” The activation energy needed to energy to reach the “transition state”. Consequently, the break down perchlorate is high: 123.8 reduction of perchlorate with typical reducers is too slow kJ/mol below 240 ºC; 79.1 kJ/mol from 240 (days to weeks) to be used in water treatment plants. to 200 ºC; 307.1 kJ/mol between 400 and Image: 440 ºC (ATDSR, 2008). This kinetic barrier is difficult for environmental engineers This also implies the main path of perchlorate in the working towards remediation because environment is aqueous, and the primary risk to typical reducing agents cannot reduce humans will be via ingestion. Perchlorate perchlorate economically (Urbansky, 1998). compounds are denser than water, a property that Table 1 shows that all common affects the transport of perchlorate in groundwater perchlorate compounds have an extremely aquifer plumes. Table 1 also lists the specific low vapor pressure, and do not volatize from gravities. water to air (Sellers, 2007). Therefore, air stripping is ruled out as a treatment option. Table 1: Physical and chemical properties of perchlorate (EPA, 2005 & IDTC, 2005) Perchlorate Compounds Ammonium Potassium Sodium Perchloric Acid Colorless orthorhombic Physical state at White orthorhombic White orthorhombic crystal or white Colorless liquid ambient temperature crystal deliquescent crystal crystalline powder Molecular weight 117.49 122.44 138.55 100.47 (g/mol) Water solubility (g/L at 200 2,096 15 Miscible in cold water 25oC) Melting / Boiling point Melting Point: 65.6 to Melting Point: -112 Melting Point: 482 Melting Point: 400 (oC) 439 Boiling Point: 19 Vapor pressure at 25oC Not available 4.8 Not available 3.5 (mm Hg) Specific gravity 1.95 2.52 2.53 1.664 Octanol-water partition -5.84 -7.18 -7.18 -4.63 coefficient (log Kow) Sorption Capacity Very low Very low Very low 3 Very low Volatility Nonvolatile Nonvolatile Nonvolatile Nonvolatile
  8. 8. III. Common Commercial glass etching (ATDSR, 2008). Applications Worldwide production of perchlorates was less than 3.6 million total The most widely used perchlorates pounds up until 1940. However, with the are in the form of solid salts, including onset of World War II, annual production of ammonium, potassium, magnesium, sodium, perchlorate increased to 36 million pounds, and lithium perchlorate (see Table 2) . The due to the increased demand for rocket and Department of Defense (DOD), the National missile propellants. Advancements in space Aeronautics and Space Administration exploration technology and cold war (NASA), and the defense industry have used innovations further increased demand. U.S. perchlorate for decades in the perchlorate production alone reached 50 manufacturing, testing, and firing of missiles million pounds annually by 1974, and in and rockets. Their primary uses are as 1994 was estimated at around 22 million oxidants in combination with fuel sources. pounds, or 34% of capacity (ATDSR, 2008). The approximate percentages sold for Because perchlorate is considered a specific end users are 92% as an oxidizer, “strategic chemical” due to its military 7% as an explosive, and 1% for other uses applications, and because the U.S. does not (CDTSC, 2005). The DOD uses 6-8 million log perchlorate as a separate good on pounds of ammonium perchlorate annually, import/export logs, exact U.S. production of which roughly 4 million pounds is and disposal volumes are difficult to gauge recovered and recycled for use in (ATDSR, 2008). commercial applications such as blasting or Ammonium perchlorate accounts for 90% of perchlorate production in the U.S., Table 2: Estimated Annual Production and Use of Perchlorate Compounds U.S. Chemical Production Compound Use Formula in 1951-1997 (million lb.) Ammonium NH4ClO4 609 Energetic booster in rocket fuel, used primarily by the DOD, national perchlorate aeronautic space, and space administration. The high solubility of NH4ClO4 makes this material useful as an intermediate for production of all other perchlorates by double metathesis reactions and controlled crystallization (Kirk, 2004). Sodium NaClO4 20 Strong oxidizing agent used in the explosives and chemical industry perchlorate (Kirk, 2004). Potassium KClO4 22 Solid oxidant for rocket production; also used in pyrotechnics perchlorate (ATSDR, 2008). Lithium LiClO4 No data Electrolyte in voltaic cells and batteries involving lithium anodes; thin perchlorate found film polymers used in certain electrochemical devices, may be doped with lithium perchlorate to induce conductive properties; used as a synthetic of certain organic compounds (Seller et al, 2004). Magnesium Mg(ClO4)2 0.7 Drying agent for industrial gases; electrolyte for magnesium batteries; perchlorate used in synthesis of certain organic compounds (Kirk, 2004). Perchloric HClO4•2H2O No data Analytical reagent; used hot and concentrated as oxidizing and acid found dehydrating agent (Merck, 1983). 4
  9. 9. and is the largest component of solid rocket (Seller et al, 2004). Other uses of (~70%) and missile propellants (Lieberman perchlorates include fireworks, road flares, et al, 2008). Being the only common matches, photography, etching and perchlorate that does not leave behind a engraving, and blasting explosives used for solid by-product as well as the ease of mining and other civilian applications. disposal from rocket encasings adds to its Fireworks can contain up to 70% (wt) widespread use (CDTSC, 2005 & Atikovic, potassium or ammonium perchlorate, and 2007). Solid rocket fuels that use over 221 million pounds of pyrotechnics perchlorate, as opposed to liquid fuels that were consumed in 2003 in the U.S. (Seller et use other oxidizers, can provide a high thrust al, 2004). Sodium perchlorate is employed for a low cost (ITRC, 2005). Average annual in airbag inflator systems. Due to their low production rates for ammonia perchlorate weight and high energy density, lithium and between 1951 and 1997 estimated to be magnesium perchlorate have been used in roughly 1.06 x 107 kg per year. The sole batteries. Potassium perchlorate can be producer of ammonium perchlorate in North mixed with reactive metals such as America is American Pacific Corporation zirconium or iron, and used in heat pellets to (AMPAC) near Cedar City, Utah (ATDSR, activate reserve battery cells (ATDSR, 2008). Ammonium perchlorate is also used 2008). in small amounts in ammunition, mixed with In 1998, the FDA approved the use sulfamic acid to produce smoke and dense of potassium perchlorate as an additive in fog for tactical military operations, and as a rubber gaskets of food containers. component of temporary adhesives used Ammonium, potassium, and sodium with steel and other metallic plates perchlorate have also been used as (ATDSR, 2008). stimulants to increase the weight of poultry Nitrate and perchlorate containing and other farm animals, and as weed killers Chilean salt pepper is used in the production and growth stimulants in leguminous plants of fertilizer. The United States has been (ATDSR, 2008). importing Chilean caliches since 1830, and Another common form of the use continues today with the U.S. commercially available perchlorate is importing more than 75,000 tons containing perchloric acid (HClO4). Applications 0.01% perchlorate annually between 2002 include etching of liquid crystal displays, and 2004 for use mainly on tobacco, cotton, polymerization catalysis, critical electronics and some fruit crops (Seller et al, 2004). applications, and ore extraction. Perchloric This accounts for approximately 1% of the acid is also used routinely for many total fertilizer used per year in the U.S. industrial and testing laboratory chemical (ATDSR, 2008). analyses, including isolation, separation, titration, deproteinization, dehydration, and Other Commercial Applications of as a solvent and oxidizing agent. Analytical Perchlorate. While perchlorate’s major use chemists use perchlorates to adjust the ionic is in the production of rocket propellant, strength of aqueous metal solutions. munitions, explosives and fireworks, Perchlorates are unreactive as a ligand (do manufacturers also use perchlorate not complex with metals) so they do not compounds in small amounts for some interfere with the chemical dynamics of the consumer products (see Table 3). Since investigation (Urbansky, 1998) 1976, over 14,000 patents have been issued Perchlorates used medically during for various perchlorate-containing materials the 1950s and early 1960s, for the treatment 5
  10. 10. of hyperthyroidism, or Graves’ disease. In the United States, perchlorate is still used salivary glands. In addition, treatment to during medical imaging of the brain, blood, counter effects of the drug amiodarone on and placenta, in order to block radioiodine the thyroid includes potassium perchlorate uptake in the thyroid, choroid plexus, and (ATDSR, 2008). Table 3: Estimated annual perchlorate releases from commercial and natural applications le Application Est. Perchlorate Additional Information Release (lb/year) Chilean 15,000 About 75,000 tons of fertilizer including 0.01 (wt) % perchlorate was used nitrate annually between 2002 and 2004 (Seller et al., 2004). fertilizer Fireworks No data found Environmental releases of perchlorate are difficult to predict due to variability in the decomposition of perchlorate during combustion. Concentrations as high as 44.2 μg/L have been observed in nearby surface waters following a fireworks display in Oklahoma (Wilkin et al, 2007). Safety flares 240,000 Preliminary research indicates that unburned and burned flares can leach 3.6 g and 1.9 mg respectively perchlorate. Estimated 20-40 million flares used annually (Seller et al., 2004). Blasting No data found Blasting agents used in coal mining, quarrying, and other uses can contain explosives perchlorate up to 30 (wt) %. The U.S. produces around 2.5 million tons of explosives annually (Seller et al., 2004). Environmental releases of perchlorate are difficult to predict due to variability in the decomposition of perchlorate during combustion. Wells at the Kennecott copper mines in Magna, Utah have measured 13 ng/L perchlorate (Urbansky, 1998). Chemical 1,700 Electrochemical production of sodium chlorate can generate perchlorate as an Production impurity at 50-230 mg/kg chlorate. The annual consumption of sodium chlorate in the U.S. is around 1.2 million tons (Seller et al, 2004). Defoliant 1,600 Perchlorate released as a defoliant between 1991 and 2003 is estimated at around 20,000 lb (Seller et al, 2004). IV. Commercial and Natural saltpeter deposits contain concentrations Production from 300 to 1,000 mg/kg in the soil. Natural perchlorate has been detected in the Bolivian Natural Sources. Perchlorate occurs Playa crust high in the Andes, at naturally in the environment, but its exact concentrations of 500 mg/kg of soil (Seller origin and mechanisms of formation are not et al, 2004). Research on perchlorate known. Isotopic ratios in the nitrate deposits containing soils has concluded that suggest that perchlorate formed in the perchlorate and nitrate co-occur naturally, so atmosphere by a process involving ozone as perchlorate is extracted from deposits of the oxidant (Brown, 2005). It has typically nitrate ores, and is distributed in sodium been discovered in high concentrations in nitrate fertilizer. Dry deposits of perchlorate the soils of arid climates. Historically, the are also found naturally within potash largest known natural source of perchlorate (potassium ore deposit) in mines close to is found in Atacama Desert in Chile, where Carlsbad, New Mexico and in 6
  11. 11. central Canada. The concentrations of Perchlorate could also be an intermediate perchlorate in these deposits range from 25 by-product from the interaction of two to 2,700 mg/kg of soil. Reservoirs of natural hypochlorite degradation pathways, for perchlorate in the arid American southwest instance degradation to chlorate and are estimated at up to 1 kg/ha (Seller et al, degradation to oxygen and sodium chloride 2004). (MDEP, 2009). Industrial Preparation. Sodium Waste Streams. Figure 3 shows a map of perchlorate is the most soluble salt, and known perchlorate users and table 4 shows therefore the principal salt produced. The some typical waste stream volumes. One of most common method of producing sodium the advantages of ammonium perchlorate perchlorate is electrolysis of an aqueous compared to other oxidizers is that it is solution of sodium chloride, with the easily washed out of old rocket boosters and following two electron oxidation series can be reused in other commercial (ATDSR, 2008): applications (after being re-crystallized). The washout operation generates wastewater (4) Cl- → ClO2- → ClO3- → ClO4- that because of perchlorates low solubility and other properties persists in the All other perchlorate compounds are formed environment for decades (Atikovic, 2007). by adding other salts to a sodium nitrate Two methods of solid propellant disposal solution, to selectively re-crystallize the used in the past, open burning and hydro- perchlorate salts that are less soluble than mining, discharged perchlorate directly into sodium perchlorate: the environment. With open burning, un- combusted fuel material was allowed to seep Na+ (aq) + ClO4- (aq) + M+ (aq) + X- (aq) → into the soil and water. Current practice is to MClO4 (s) ↓ + Na+ (aq) + X- (aq) collect unburned material and re-burn it “to ensure complete combustion of energetic where X is chloride, sulfate, or carbonate; M material (ITRC, 2005).” Hydro-mining is a is magnesium, potassium, lithium, or method of using high pressured water jets to ammonium; and MClO4 (s) is the desired wash out the rocket booster, so the hard perchlorate (ATDSR, 2008). ware can be recycled. Current practice it to Degradation of other compounds is capture and treat the waste streams prior to another way to produce perchlorate. discharge (see section VIII), but in the past Perchlorate can be found as a breakdown the waste water was discharged untreated to product in solutions of sodium hypochlorite, the ground or into retention pounds prone to which is used as a swimming pool leakage (USEPA, 2005). Measured disinfectant, and can be incidentally formed perchlorate levels in ground and surface in corrosion control applications. The water near munitions and rocket fuel plants mechanism hypothesized for perchlorate have been shown to range from 4000 mg/L formation commences with the initial to as high as 3700 mg/L (Urbansky, 1998). degradation of hypochlorite to chlorate. 7
  12. 12. Figure 3: Locations of known users and manufacturers of perchlorate (USEPA, 2005) Table 4: Selected perchlorate sources, releases and detections (Mayer, 2004) State Location Suspected Source Type of Contamination Max. Conc. ppb NV Kerr-McGee/BMI Perchlorate Public Water System 24 Henderson, Nevada Manufacturing Monitoring Well 3,700,000 Surface Water 120,000 NV PEPCON Perchlorate Monitoring Well 600,000 Henderson, Nevada Manufacturing (former) CA Aerojet General Rocket Public Water Supply Well 260 Rancho Cordova, CA Manufacturing Monitoring Well 640,000 CA Rialto-Colton Plume Fireworks Facility Public Water Supply Well 811 Rialto, CA Flare Manufacturing Rocket Research and Manufacturing CA Stringfellow Hazardous Waste Monitoring Well 682,000 Superfund Site Glen Disposal Facility Private Well 37 Avon, CA IA Ewart, IA Unknown Source Livestock Well 29 NY Westhampton Unknown Source(s), Public Water Supply Well 16 Suffolk County, NY possibly agricultural Monitoring Well 3,370 8
  13. 13. Perchlorate can also be released into run-off becomes mobile in the environment the environment at sites where perchlorate (ATSDR, 2008). Changes in land use salts are used in manufacturing processes. patterns from natural settings to irrigated As mentioned above, there is only one agricultural land are mobilizing natural producer of ammonium perchlorate today, deposits of perchlorate into surface and but there were many more that operated in ground waters in these locations (Rao et al, the past but have now closed or ceased 2007). In wet and humid climates that perchlorate production (see Table 4). Those coincide with agricultural applications of former sites of manufacture are current imported perchlorate-containing fertilizers, locations of perchlorate plume tracking and there can be leaching from solid perchlorate remediation. at the soil surface (Seller et al, 2004). Other anthropogenic waste streams One study shows estimated source have occurred from munitions strength of 1.4 x 105 kg/year for perchlorate manufacturing & disposal and the launching released to the environment from road of solid fuel launch vehicles. Natural waste flares. If perchlorate is released into the air, streams may occur when sand or soil it will eventually settle out, primarily in containing perchlorate erodes and by way of rainfall (ATSDR, 2008). The US-EPA documents that 63 DOD sites or installations have detectable (meaning over the minimum detection Table 5: Selected DOD sites with perchlorate range of .5 ppb-1 ppb) perchlorate detections (extracted from ITRC, 2005) concentrations in soil, and/or Perchlorate ground water. Racca et al (2008) reports State Installation Branch Type of detection 56 installations had detections of over 4 Contamination (ppb) ppb by 2007. A 2001 DOD survey of weapons systems containing perchlorate Edwards Air Air listed 259 different munitions. There is CA GW 160,000 Force Base* Force also a ‘perchlorate replacement program’ Holloman Air Air underway to replace perchlorate in some NM SW 16,000 Force Base Force existing munitions when possible (ITRC, 2005). Aberdeen MA Army DW, GW 5, 24 DOD site prioritization began in Proving Ground 2004 to determine which DOD Redstone establishments posed the greatest risk to AL Army GW 160,000 Arsenal* drinking water contamination. Sites were evaluated based on reported detections White Sands NM Army GW 21,000 over 4 ppb, whether or not perchlorate Missile Range related activities had occurred at the site, Naval Air and site proximity to drinking water wells Weapons (less than 1 mile, between 1 and 5, or CA Navy GW 560 greater than 5 miles) (Racca et al., 2008). Station, China Lake This list is not comprehensive, but representative of detections at select Naval Surface DOD facilities. MA Warfare Center, Navy SW 1,000 Indian Head* (*) perchlorate cleanup is underway as of September, 2005. 9
  14. 14. Transport in the Environment. As Flowers et al (2001) examined the mentioned above perchlorate compounds are behavior of perchlorate plumes in highly soluble in aqueous solution and the groundwater aquifers (see Figure 4). Their perchlorate ion does not bind to soil model assumed dense brine was released at particles. Perchlorate has been released to a disposal site. Since a large density the environment in solid form, as (1.11g/cm3) contrast exists between the ammonium, sodium, potassium, and other concentrated brine and ambient perchlorate salts, as well as in liquid form. groundwater, in the vadose zone the These concentrated releases form highly perchlorate solution will sink vertically by density perchlorate brines once in contact the force of gravity at the same velocity as with moisture. In soil, the movement of water, and horizontally by way of capillary perchlorate is a “function of the amount of forces. As perchlorate disperses it begins to water present. (ITRC, 2005)” move faster than the average groundwater velocity (Flowers et al, 2001). Figure 4: Fate and transport of perchlorate in groundwater aquifer and estimated residence time (adapted from Flowers et al, 2001) 10
  15. 15. In arid regions perchlorate “may options would be an economically accumulate at various horizons in the soil inefficient way to treat perchlorate, and that due to evaporation of infiltrating rainfall that “isolating and removing the source” of leached perchlorate from shallower depths. contamination is recommended (Flowers et (ITRC, 2005)” al, 2001). After subsurface migration in the As mentioned above, under ambient vadose zone, the concentrated brine will conditions perchlorate is kinetically stable pool on top of a low-permeability confining and does not react or decompose. layer and eventually penetrate the layer Biodegradation of perchlorate will not occur byway of diffusion (at a lower velocity than unless significant levels of organic carbon in the vadose zone). Once confined in the are present. Taking into account perchlorates low-permeability layer, perchlorate will high solubility, low sorption, and lack of become a long-term source of aquifer degradation plumes tend to be large and contamination (appx. 100 year retention persistent. For example, the perchlorate time) because of mass-transfer limitations plume at the Stringfellow Superfund site (Flowers et al, 2001). Even when (Figure 5) in California persists for 5 miles perchlorate discharge at the surface is from the Pyrite Canyon to the Santa Ana stopped, and the pool above the low- River (Kenoyer et al, 2007.) According to permeability layer stops growing, the California-EPA, wastes from rocket fuel perchlorate will still diffuse back into the users/manufacturers were transported and aquifer from the confining layer. They dumped in unlined pounds for evaporation at conclude that long-term pump and treatment Stringfellow throughout the years. Figure 5: Schematic of Perchlorate Plume at Stringfellow Superfund Site (CDTSC, 2006) Average of detected perchlorate concentrations 18 ppb 12 ppb Image: (Center for Community Action and Environmental Justice) 11
  16. 16. In addition, quarry blasting in Pyrite perchlorate concentrations (60ppb) in the Canyon (since 1904) may have included Ogallala aquifer of the Texas southern High explosives that contained perchlorate dust Plains. Their studied showed that that was washed into the soil and creeks, and perchlorate was found beneath natural then into groundwater. Irrigation of the Glen grassland and shrub land ecosystems (2.7- Avon area may have occurred from sources 7.2 ppb), and that its correlation with such as the Colorado River, and many tons chloride concentrations suggests dry fallout of nitrate fertilizer was used in the area and precipitation are the likely sources. during the twentieth century (CDTSC, Further, they determine that perchlorate 2006). Since these activities span over a plumes reach a maximum depth of 8.3 century, and are all considered ‘possible’ meters in a downward direction under rain sources, exact numbers on releases in the fed agricultural areas, and again correlate vicinity of the Stringfellow site are not perchlorate concentrations with chloride available. However, current perchlorate concentrations (Scanlon et al, 2007). concentrations measured in nearby A 2007 study by Wilkin et al (2007) groundwater wells are shown in the figure looked at perchlorate concentrations in a below. lake following fireworks displays. It An abstract from the American concluded that before the fireworks displays, Geophysical Union’s fall 2007 meeting lake concentration of perchlorate rose from a indicates that “groundwater perchlorate mean value of .043 ppb to a maximum contamination is likely to increase in the concentration of 44.2 ppb after the display. future with more widespread flushing of Perchlorate concentrations returned to naturally occurring perchlorate beneath previous levels within 20 to 80 days after the cultivated regions.” Their study was display, “with the rate of attenuation motivated by the discovery of high correlating to surface water temperature.” water contamination, Tronox Plume Management. Figure 6: Pathway of Tronox Plume in the Southwest In mid-1997 the United States (USEPA, 2005) Metropolitan Water District of Southern California discovered perchlorate in the lower Colorado River and traced contamination to Lake Mead and the Las Vegas Wash (see Figure 6). Ultimately, the source of the perchlorate was traced to the Kerr McGee (now Tronox) Chemical Plant in Hendersen, Nevada (USEPA, 2005). Tronox ground water aquifer plume released about 900 to 1000 pounds per day (average) of perchlorate to Las Vegas Wash prior to controls being implemented (USEPA, 2005). After revelations of the drinking 12
  17. 17. Tronox suspended the production of to a federal drinking water limit for perchlorate and began remediation. The cost perchlorate. The occurrence maps that have of remediation is 124 million dollars, and been produced from studies by Brandhuber has resulted in a 90% decrease in et al (2005) (occurrence in public drinking perchlorate entering the LVW since 1999 water systems) and the USEPA (2005) (Aqueduct Mag., 2008). (users, manufacturers and releases) show Their control strategy aims to that perchlorate is many times present in capture and treat perchlorate on Tronox public water systems where no known or property where it is most concentrated by likely anthropogenic releases into the means of a slurry wall, at a narrow environment have occurred. subsurface channel between the plant and LVW, and near LVW where capture will Public Water Systems. Current analytical have the most immediate impact on reducing techniques have achieved detection limits as releases to LVW. The Tronox releases low as 0.5 ppb for perchlorate. In 1999 described above, which ended up in Lake perchlorate was added to the EPA’s Mead and the lower Colorado River had an Unregulated Contaminant Monitoring List impact on the drinking water supply of 15 to (UCML), and public water systems (PWSs) 20 million people in Arizona, southern serving more than 10,000 people were California, southern Nevada, Tribal nations required to monitor perchlorate levels and Mexico (USEPA, 2005). beginning in 2001. As part of the EPA’s UCMR 1 program, conducted between 2001 IV. Environmental Occurrence and 2005, data was compiled from 34,331 samples collected at the entry points (where Perchlorate Exposure in the United water goes from the source into the States. The U.S. EPA has been tracking the distribution system) of 3,865 of the nations manufacturing, use and release of PWSs. The minimum detection limit for the perchlorate to the environment since the late UCMR 1 program was 4 ppb, and 1990’s (Brandhuber, 2005). In addition, the perchlorate was detected in 637 (1.9%) of DOD is currently in the process of going those samples, which equated to 160 (4.1%) through historical records of possible of PWSs. perchlorate containing production processes In addition to PWS’s that serve more to estimate the total amount of perchlorate than 10,000 people, 800 samples (2.3% of that has been released throughout the the total) were taken from PWSs that serve century (ITRC, 2005). Occurrence mapping populations less than 10,000. Therefore, the for perchlorate attempts to pinpoint the UCMR 1 accounted for roughly 80% of the location of users and manufacturers of U.S. population (Brandhuber et al, 2005). perchlorate (Figure 3), known or suspected According to Russell et al (2009), a recent releases of perchlorate into the environment study (an update of Brandhuber et al (2005) (Figure 7), and its detection in public water to be published in AWWA Journal at the systems (concs. > 4ppb, Figure 7). In end of 2009) points out that because the addittion, its occurrence in food can be UCMR 1 only accounted for 1.8% of small mapped from various studies, but PWSs (pop. < 10,000) a “more complete establishing the cause and effect relationship sampling effort” is needed to fully assess between perchlorate releases and its perchlorate concentrations in those systems, pathway to food products is a challenge. and it is likely the levels are higher than Further, its occurrence in food is not related previously assumed from the UCMR 1. 13
  18. 18. Figure 7: Suspected or known perchlorate releases and detections (Brandhuber, 2005). Known perchlorate release Drinking Water Detections: 4µg/L < 10 µg/L >10 µg/L Figure 8: Percent of total U.S. perchlorate detections found in each state (Russell et al, 2009) 14
  19. 19. Of the positive detections, the perchlorate concerning studies related to perchlorate in concentrations ranged from 4 ppb to more food, since it is not related to a federal than 3.7 million ppb, with an average of standard for perchlorate in drinking water, 9.85 ppb. More than half of detections and because the studies have found it hard to occurred in California and Texas (see Figure track sources of most perchlorate containing 8 above), with the highest concentrations foods. found in Arkansas, California, Texas, Nevada and Utah. Figure 4 shows the share Table 7: Relative source contributions remaining for of total PWSs with perchlorate detections water based on TDS for various sub-groups (extracted allotted to each state (and Puerto Rico). from US EPA, 2008) Figure 7 shows detections of perchlorate Population Food intake RfD RSC for between 4bb and 10 ppb, and those above 10 Group (ug/kg/day) remaining DW (% ppb (Brandhuber et al (2005). (ug/kg/day) of RfD) Table 6: Measured perchlorate concentration Infants .26-.29 041-.44 59%- in common foods (compiled from FDA, 2004 63% & Jackson et al, 2005) Children, 2yr .35-.39 .31-.35 44%- 50% Children, 6yr .25-.28 .42-.45 60%- Type of Minimum Maximum Mean 64% sample (ppb) (ppb) Perchlorate Children, 10 .17-.20 .50-.53 71%- (ppb) yr 76% Teen Girls .09-.11 .59-.61 84%- Vegtables 2.38 228.25 19.43 87% Bottle 0.45 0.56 ND Teen Boys .12-.14 .56-.58 80%- water 83% Women, 25- .09-.11 .59-.61 84%- Cow milk 3.16 11.30 5.76 30 87% Fruit 0.85 144.48 ND Men, 25-30 .08-.11 .59-.62 84%- Apple 1.39 3.45 2.15 89% juice Women, 40- .09-.11 .59-.61 84%- 45 87% Orange 2.27 3.15 2.59 Men, 40-45 .09-.11 .59-.61 84%- juice 87% Sweet 0.85 2.07 1.24 Potatoes Occupational Exposure. In two widely cited occupational studies (Lamm et al, Fish 12.22 17.70 6.61 1999 & Gibbs et al, 1998) there were no adverse health effects on factory workers Food Exposure. Perchlorate is common in exposed to perchlorate. While there was many foods. Table 6 and Table 7 list reduced iodine uptake, there was not any perchlorate concentrations found in food signs of hypothyroidism (i.e. no changes in samples, and the relative source contribution TSH, T4, and T3 levels) (ATDSR, 2008). A of food to perchlorate in our diets. The more recent study, Bravermen et al (2005), relative source contribution will become found similar results. The study found that important in the health section of this report workers experienced a decrease in iodide when developing the subchronic health uptake during their shifts when exposed to advisory. This report does not go into detail high doses, as well as fluctuations in T3 and 15
  20. 20. T4 levels, but that these effects went away “The median estimated absorbed when the worker was away from the factory. dose was 0.167 mg/kg/day, equivalent to They concluded that “long-term, drinking approximately 2L of water intermittent, high exposure to ClO4- does not containing 5 mg perchlorate/L. It should be induce hypothyroidism or goiter in adults mentioned that perchlorate workers are (Braverman et al, 2005).” These terms will exposed during an unusual schedule of three be described in more detail in the Health 12-hour shifts followed by 3 days without Effects section of this report. In exposure (long-time, intermittent exposure). occupational settings, the main risk factor Given the relatively short elimination half- would be via inhalation. Finally, it is worth life of chlorine in worker of approximately 8 repeating that ammonium perchlorate is hours (Lamm et al, 1999) perchlorate would 90% of perchlorate sold, and all ammonium not be expected to accumulate to levels that perchlorate produced occurs in a single would cause thyroid problems (ATSDR, production plant in Henderson, Nevada (as 2008).” No data were found on levels of mentioned above). These studies were all perchlorate in ambient air, but workers at an carried out at that plant. Therefore, the ammonium perchlorate production facility implications of the numbers that follow who were exposed to perchlorate dust had would apply only for workers at that single single shift absorbed doses measured at 0.2– plant, who would be experiencing the most 436 μg/kg, with a 35 μg/kg average. frequent doses of perchlorate and maybe the Cumulative lifetime doses for these workers only doses in the United States at any given over an average of 8.3 years ranged from time. Needless to say, a federal regulation 8,000 to 88,000 μg/kg (ATDSR, 2008). for occupational exposure of perchlorate would be irrelevant. VI. Health Effects action, and not the adverse health affect. In The main health concern regarding this respect, perchlorate is treated differently the perchlorate ion is its ability, when in the than other ‘candidate contaminants’ that the human blood stream, to inhibit the uptake of EPA evaluates for regulation (US EPA, iodide by the thyroid. The EPA considers 2008). Therefore, since the reference dose of this inhibition the mode of action rather than perchlorate is not based on the adverse the adverse affect. Srinivasan et al (2009) health effect, but a precursor to the adverse states that the mode of action is considered health effect, it can be considered an added the factors that cause the inhibition of iodide safety factor to protect vulnerable groups uptake, and the potential adverse health (see Figure 12). affect is hypothyroidism. The flow chart to It is important to point out that the the left, adapted from Seller et al (2007), available clinical studies in many cases illustrates this distinction (see Figure 9). The show that perchlorate affects thyroid EPA’s reference dose for perchlorate and all functioning (ie. iodide uptake inhibition) discussion regarding exposure to vulnerable while exposure is occurring, but no study groups is always referring to the mode of has proven any long term adverse health 16
  21. 21. effects of perchlorate at doses that are likely Figure 9: Perchlorate mode of action and to be consumed by humans from drinking adverse affect when ingested (adapted from water or food supplies. This section will Seller et al, 2007) discuss further important human studies over the past ten years, the relevance of animal studies, and finally potentially vulnerable groups of the human population. Perchlorate and Thyroid Function. When Mode of Action idodide uptake is reduced, one or more steps in the synthesis and secretion of thyroid hormones can be interrupted, resulting in subnormal levels of T3 (triiodothyronine) and T4 (thyroxin) and an associated compensatory increase in secretion of TSH (thyroid stimulating hormone). Perchlorate has been found to induce this precursor to the adverse effect (iodide uptake inhibition) and subsequent adverse affect in humans when administered at doses much higher than those found in the environment (greater Adverse Affect than 500 ppb). The perchlorate ion, because of its similarity to iodide in ionic size and charge, competes with iodide for uptake into the thyroid gland by the sodium-iodide symporter, a transport mechanism in the membranes of thyroid cells. This competitive inhibition results in reduce production of the thyroid hormones T3 and T4 and a consequent increase in THS where thyroid, pituitary and hypothalamus are involved (see figure 10) (ATDSR, 2008). Subsequent events include decreases in serum T4 and T3. In mice studies, this decrease has led to the potential for altered neurodevelopment if observed in either perturbation of thyroid hormone economy as mothers, fetuses or neonates, and increase in the primary biological effect of perchlorate serum TSH leading to the potential for in rats (CDTSC, 2005) thyroid hyperplasia and tumors (ATDSR, 2008). The repeat observation of thyroid Human Studies. In the US Department of effects such as alterations of hormones, Health and Human Service’s Toxicological increase thyroid weight, and alterations of Profile for Perchlorate, studies are thyroid histopathology from a large number summarized that aimed to determine “does- of rat studies on perchlorate provide response relationships at low doses of and to supporting evidence for the propose mode- define no-effect level of exposure to of-action, and confirms that the perchlorate (ATSDR, 2008).” 17
  22. 22. Their summary concludes that no study thus based in Washington D.C.) are cited widely far has shown perchlorate to cause adverse in the blogosphere and in newspapers, health effects in humans at doses would indicate that perchlorate has been encountered in the environment. G. determined highly dangerous to women with Charnley (2009), Srinivasan et al (2009), low iodide levels, and that the lack of a and Hagstrom (2006) back up this claim Federal perchlorate regulation is a result of with their summaries. Defense Department lobbyists and other special interests. The keystone study cited in Figure 10: The thyroid and its role in hormone this sphere of information is a 2005 CDC secretion (image: report that establishes a positive relationship between iodide deficient women, perchlorate levels in their urine, increasing serum concentrations of TSH, and decreasing serum concentrations of T4 (ie. perchlorate was a predictor for the imbalance of these hormones in iodine deficient women). The study (Blount et al, 2006) evaluated the relationship between levels of perchlorate in the urine and serum levels of TSH and T4 in 2,299 men and women (>11 years old). The study concluded that in women with urinary iodine < 100µg/L, perchlorate was a predictor of T4 and TSH. A previous study on women in Chile (avg. iodine 269µg/L) exposed to perchlorate Greer et al (2002) conducted the concentrations of up to 114 µg/L showed no most widely cited study (under the auspices adverse affect, but their iodine of the National Academy of Sciences), one concentrations were sufficient. However, the that is also the basis for the EPA’s Blount study recognized that the low levels perchlorate reference dose (RfD). 37 human of perchlorate that produced the adverse volunteers were separated into four groups affect in iodide deficient women did not and served drinking water amounting to produce adverse affects in numerous 0.007, 0.02, 0.1, and .5 mg/kg-day levels of previous studies. As they put it: “(The perchlorate for 14 days. Using various adverse affects of this study) are found at statistical measures of radioiodine uptake perchlorate exposure levels that were inhibition they determined a true no effect unanticipated based on previous studies level of 5.2 and 6.4 µg/kg-day measured 8 (Blount et al, 2006).” Furthermore, they and 24 hours after exposure, respectively. establish a predictor, but the change in T4 For comparison, this would correspond to a and TSH was still within the healthy range drinking water supply concentration of for a human being. Finally, a New York about 180 and 220 µg/L (ppb), respectively. Times article quotes the author of the CDC The levels detected in U.S. drinking water study as follows: “The study did not supplies generally range from 5-20 µg/L as establish a cause-and-effect relationship but seen in section IV (Greer et al (2002). pointed to a need for more research Reports released by the (Goodman, 2009).” Environmental Working Group (a non-profit 18
  23. 23. In addition, and something these time than in rats to affect the circulation of researchers seemed to have over looked or at T4 and T3 hormones (ATSDR, 2008). There least considered, is that an iodine deficiency are also physiological differences between in and of itself is a cause of hypothyroidism, rats and humans related to the pituitary with or without the perchlorate. Any online thyroid axis, which “makes rats medical dictionary will explicitly state the inappropriate for quantifying predicted main adverse affect of iodine deficiency is changes in humans for risk assessment hypothyroidism. The CDC study removed purposes (Srinivasan, 2009).” 91 women from a total of 1,226 because In the June 2009 Environmental they had reported a history of Health Perspectives there is a discussion of hypothyroidism. This indicates that the an article by Gilbert et al (2008) in which he authors assumed that the majority of women claims neurological development effects of with a thyroid disorder or out of the ordinary perchlorate in drinking water consumed by T4 and TSH have been diagnosed. They do adult rats. Though the discussion is not peer not offer a justification for that assumption. reviewed, it is a discourse about a peer The authors controlled for many variables reviewed article between the authors of the that could also be positive predictors of T4 article, and employees from Novice who or TSH, but none of those include low were contracted to assess the claims of the iodide levels. The authors also state that the article. While they go back and forth about World Health Organization defines implications of the article, they both agree sufficient iodine intake as 100µg/L or more. on one thing: “…the purpose of our study So by concluding that women with iodide was not to emulate human exposures to levels below the accepted standard showed perchlorate.” The study found a reduction in the typical adverse affect of low iodide synaptic functioning at a dose of 4.5 mg/kg- content, the authors are stating the obvious. day, which is much higher than the maximum concentration of .5 mg/kg-day in Animal Studies. Most of the concern about Greer’s study (Gilbert et al, 2009). perchlorate’s possible adverse effect on human health stems from extensive research At-risk subpopulations. The main concern on animals where perchlorate doses have and basis of the perchlorate regulatory instigated hypothyroidism and tumors. debate is on possible congenital effects. Generally, the animals in these studies are Since fetuses of hypothyroidic women are at given doses 10-times or more the amount a greater risk for abnormal growth and likely to be encountered by humans in the development, the concern is that perchlorate environment (Srinivasan, 2009). Rats and induced hypothyroidism will produce the mice are used because in some cases their same effects. “(According the National response mechanisms to perchlorate would Research Council) because the fetus be similar to humans. Specifically, rats and depends on an adequate supply of maternal humans have thyroids that function thyroid hormone for its central nervous similarly, and the mode of action of system development during the first perchlorate (i.e., iodide uptake inhibition) is trimester of pregnancy, iodide uptake analogous. However, the main difference inhibition from low-level perchlorate between human and animals represented in exposure has been identified as a concern in the studies is the dose-response connection with increasing the risk of relationships. In humans, perchlorate neurodevelopmental impairment in fetuses dosages must occur over a longer period of of high-risk mothers (USEPA, 2008).” 19
  24. 24. VII: Regulation Figure 11: Progression of Perchlorate Regulation at the Federal level in the United States (self-generated graphic) Perchlorate Regulation in the United Federal regulation (US EPA, 2009). “The States. Figure 11 illustrates the history of U.S. Congress is considering two pieces of perchlorate regulation at the Federal level. legislation, one that would compel the US Because debate exists regarding its health EPA to establish a drinking water standard effects at environmentally present doses, for perchlorate and one that would compel there is not a federal drinking water limit US EPA to determine whether perchlorate established for perchlorate. California and should be regulated (G. Charnely, 2008).” Massachusetts are the only two states to establish an enforceable regulation for According to the EPA, in order to perchlorate, as shown in Table 8. The Safe regulate a contaminant three conditions must Drinking Water Act was amended in 1996 to be met: include section 1412, which mandates the EPA to evaluate at least five contaminants 1) The contaminant may have an from its candidate list every 5 years and adverse affect on human health. determine whether or not they require 2) The contaminant is known to occur or there is a substantial Table 8: State Drinking Water Regulations  likelihood that the contaminant (USEPA, 2008)  will occur in public water Advisory Levels  systems with a frequency and at Enforceable Regulations  in Other States  levels of public health concern. 2  4‐51 ppb  3) Regulation of such contaminant Massachusetts  presents a meaningful ppb  opportunity for health risk California  6  reduction for persons served by   ppb  the public water system. 20
  25. 25. Table 9: Relative source contributions of perchlorate in drinking water for vulnerable subpopulations (USEPA, 2008) Sub population  Body  Drinking Water  RSC From  Potential  Weight  Consumption  Drinking  HA level  Water as %  RfD  Women of  70 kg  2 liters  84‐87%  21 µg/L  Childbearing  Age  Pregnant  70 kg  2 liters  62%  15 µg/L  Women  Figure 12: Quantification and calculations for toxicological effects of perchlorate (self generated from USEPA, 2008) NOAEL RfD = UF RfD x BW DWEL = DWI Subchronic HA = DWEL x RSC 7 µg/kg/day RfD = = 0.7 µg/kg/day 10 0.7 µg/kg/day x 70 DWEL = kg = 24.5 µg/L 2 L/day Subchronic = 24.5 µg/L x 0.62 = 0.0152 µg/L (rounded 15 µg/L) HA RfD = Reference Dose (mg/kg bw/day) DWEL = Drinking Water Equivalent Level RSC = Relative Source Contribution NOAEL = No Adverse Effect Level (mg/kg bw/day) UF = Uncertainty factor established for vulnerable subpopulations BW= Assumed body weight of an adult (70 kg) DWI = Assumed daily water consumption for an adult (2 L/day) 21
  26. 26. In October, 2008 the EPA 90th percentile rather than mean food determined perchlorate did not meet the 2nd exposure data “to ensure that the interim HA and 3rd conditions, and asked for public protects highly exposed pregnant women feedback. They received nearly 33,000 and their fetuses (USEPA, 2008).” public comments, but as of October, 2009 have not made a final determination on a VIII: Treatment Options federal regulation. Currently, there is a Federal Register notice asking for “comment In order for the EPA to set a on a broader range of alternatives” for regulation for a contaminant they must evaluating all available data on conditions 1 assess and put forth the most economical thru 3. remediation and treatment technologies. The perchlorate treatment technologies can be 2005 Reference Dose & 2009 Health classified according the environmental Advisory. The EPA assigned a Reference setting of perchlorate. The treatments in this Dose (RfD) of 0.007 mg/kg/day for section will separate the perchlorate from perchlorate recommended by the National the medium of interest or degrade it. The Research Council (NRC, 2005) based off of physical and chemical properties, cost, the NOEL from Greer et al (2002). A feasibility and source of the contamination composite uncertainty factor (UF) of 10 was will dictate which treatment is the best. used to protect the fetuses of pregnant Table 10 summarizes the technologies woman who might have hypothyroidism or discussed in this section and their range of iodide deficiency. The RfD represents the effective treatments. maximum safe oral dose of a noncarcinogenic substance that can be Ion exchange. Ion exchange (IX) is the consumed by a human. To correlate this most common used ion exchange. Ion dose with drinking water safety, a Drinking exchange is a physical-chemical process in Water Equivalent Level (DWEL) is which charged functional groups, resins, on established, which is the concentration of a the surface of a solid attracted and thereby contaminant in drinking water that will have remove ions from water via electrostatic no adverse effect. The DWEL assumes that forces. Resins are macroporous of which a 70 kg adult drinks 2 L of water per day contain positively charge surface functional with no exposure from other sources. Hence, group sorbed with counter ions, usually Cl‫־‬ 24.5 ppb (µg/L) is the DWEL recommended anions. When it is exposed to a solution that by the US-EPA in their integrated risk contains ions like perchlorate, the ions in information system (see Figure 12) (Gu et solution will enter the ion exchange, in al, 2006). exchange for Cl‫ ־‬from the resin bead, see The 2009 interim health advisory figure 13 (Chiang, 2005). covers a period of more than 30 days, but less than one year. The subchronic health advisory is directed towards the fetuses of iodine deficient pregnant women, and includes a relative source contribution from drinking water of 62% specifically for pregnant women, as their food intake varies from non-pregnant women and other populations (see Table 9). The EPA used the 22
  27. 27. Table 10: Applicability of common treatment technologies (adapted from Seller, 2007) Effective treatment Type of Technology Soil Water concentration treatment (ppb) Ion exchange ● 10-100,000 Separation GAC ● 1-10 Membrane filtration ● 10-5,000 Bioreactors ● 100-10,000 In situ 100-500,000 ● ● biodegradation Thermal destruction ● ● 10-10,000 Destruction Electrochemical 1-10 ● destruction Iron particles ● Phytoremediation ● ● 100-10,000 Catalytic reactor ● 10-1,000 Figure 13: Schematic representation of the ion exchange between perchlorate and chloride (extracted from Gu, 2006) Ion exchange technology can use multiple (lag beds). Using multiple beds can also beds in series to reduce the need for bed allow continuous operation because some regeneration; beds first in the series (lead beds can be regenerated while others beds) require regeneration first, and fresh continue to treat water, see figure 14 (EPA, beds can be added at the end of the series 2005). 23
  28. 28. Figure 14: Ion exchange treatment for perchlorate removal (Extracted from EPA, 2005) Granular Activate Carbon (GAC). It is small treatment capacity for perchlorate one of the oldest means of treatment water removal, and research is underway to process. GAC is a granular porous that has a identify methods to improve the treatment sorption capacity of contaminant as capacity of a GAC system for perchlorate perchlorate. Thus, liquid phase carbon removal, including use of “tailored GAC adsorption using granular activated carbon (Srinivasan 2009).” (GAC) is an ex situ technology to remove Rapid Small-Scale Column Test perchlorate from contaminated groundwater (RSSCT) were dry packed with virgin and surface water. The mechanism of activate carbon. Water passes onto virgin perchlorate sorption is not well understood. GAC utilizing RSSCTs containing (180 x Conceptually, perchlorate interacts with the 250 µm) GAC. The challenge for tailored positively charged surfaces of the GAC GAC is the regeneration of the medium particles rather than adsorbing to the inner because it can be regenerated. Hence, any surfaces of pores in the GAC as would a spent tailored GAC must be removed for large organic molecule. See figure 14 and disposal. It can be used organic clay and swap ion exchange resin for a sorbent zone. zeolites instead of GAC (Gu, 2006). Nevertheless, GAC has a comparatively Membrane Filtration. Membrane filtration Two streams are produced in the membrane treatment includes reverse osmosis (RO), process, see figure 15: the filtrate or nanofiltration (NF), ultrafiltration (UF) and permeate which is nearly deionized water electrodialysis (ED). Process based on and the brine concentrate or rejectate, which membrane, water is forced through a semi- contains all reject salts or dissolved material permeable membrane while dissolved salts including perchlorate. are unable to pass through the membrane. 24
  29. 29. Figure 15: Schematic representation of a membrane filtration system for the treatment of perchlorate, adapted from (Gu 2006). ClO4 → Cl − + 2O2 − Bioreactors. A bioreactor is a situ The first enzymatic step of the pathway, biological treatment system that degrades perchlorate reduction to chlorite, is contaminants in extract groundwater using performed by perchlorate reductase. The microorganisms. Biological treatment can be chlorite produced is subsequently converted aerobic, or anaerobic. Anaerobic system is to chloride and oxygen, this conversion is used to treat perchlorate. The done by chlorite dismutase, see figure 16. microorganisms are facultative anaerobes and they can use electron acceptor other than dissolved oxygen such as: nitrate, perchlorate and sulfate. The dissimilatory perchlorate reducing bacteria (DPRB) has a perchlorate reduction pathway consisting of two key enzymes perchlorate reductase and chlorite dismutase. These two enzymes govern the following anaerobic reduction process (EPA, 2006). 25
  30. 30. Organic carbon ClO4-/ClO3- e- ClO2- e- Cl- CO2 O2 H2O Figure 16: Enzymatic pathway of the dissimilatory perchlorate reducing bacteria (DPRB), adapted from (Gu 2006). More than 30 different strains of As in bioreactor, bacteria use perchlorate as perchlorate-degrading microbes have been electron acceptor (Srinivasan 2009). ISB has identified, with many classified in the reduced perchlorate concentrations less than Proteobacteria class of the bacteria kingdom. 4 μg/L in groundwater (EPA 2005). Soil and groundwater samplings have confirmed the pervasiveness of perchlorate- Thermal Destruction. This process can reducing bacteria (EPA 2005). remove perchlorate from soil to the vapor phase and subsequently destroy it. Remove perchlorate from soil requires temperatures In situ biodegradation (ISB). ISB comes between 315 to 650 ºC. This technology is together hydrogeology, chemistry, also time depending because perchlorate engineering and microbiology into an volatilizes over a period of time once a approach for planned and controlled target temperature is achieved. The exhaust microbial degradation of perchlorate. ISB from this system is accumulated by an air normally involves nutrients to the cleaning system and heated to temperatures of approximately 816 ºC to destroy it subsurface to promote the biodegradation of completely. It can treat samples with the perchlorate by the DPRB. The electron concentration from 1 to 110 µg/kg. It can donors can be substance based on carbon reduce to 4 µg/kg, if the sample is more this such as: alcohols, organic acids, or sugars. concentration (Seller 2006). Electrochemical destruction and Iron in concentrated solutions of hypochlorous particles. This process reduces perchlorate acid is been reduced. Titanium metal is also into chloride ion. When a cell has nickel used as a chemical reductant to remove electrode and a platinum counter electrode perchlorate in water. The activation of 26
  31. 31. titanium was achieved by eliminating the contaminants by natural processes occurring localized surface oxide film using within the plant body. This process for electrochemically induced pitting corrosion. perchlorate removal gain attention in the late The titanium metal ions in the vicinity of the 1990s, and it was considered for surface, pits results in a higher rate of perchlorate groundwater and soil. The process, see reduction. The surface of the bare Ti inside figure 17, ahs two mechanisms: rhizosphere the pits induces further electrochemical degradation where the perchlorate is present reactions and causes faster rate of chloride in soil adheres to the root system of the oxidation to chlorine by increasing the plant. The root system contains various current (Srinivasan 2009). microbial communities that, thus, provide Stabilized elemental iron biomass to biodegrade perchlorate. Second nanoparticles can remove perchlorate mechanism is phytoaccumulation or knowing that temperature played a critical phytoextraction. Shoots and trees take up role in perchlorate degradation process. and harvest the perchlorate and the Perchlorate removal is achieved by iron perchlorate is accumulated in leaves as a particle at temperature around 200 ºC result of evapotranspiration. The water is (Srinivasan 2009). evaporated but the perchlorate not, hence, under anoxic conditions certain Phytoremediation. Phytoremediation is in microorganism can degrade perchlorate. situ mechanism that uses plants to remove Figure 17: Phytoremediation of perchlorate. This process is an emerging technology for perchlorate remediation (taken from EPA 2005). also used to reduced perchlorate. Perchlorate Catalytic reactor. This technology uses absorbs ultraviolet (UV) light in the hydrogen gas to reduce perchlorate completely to chloride has been reported. wavelength range shorter than 185 Methylthrioxorhenium is added to combine nanometers, and consequently UV light can with 5% Pd-carbon powder. Metallic iron be used to catalyze the reduction reaction and goethite (FeO·OH) or other metal are (seller 2007). 27
  32. 32. Cost Implications of Regulating Perchlorate Conclusions The American Water Works Perchlorate is an environmental Association (AWWA) published in March, contaminant which can cause negative 2009 the first report on the national cost health affects at high doses, especially to the implications of regulating perchlorate with a fetuses of iodine deficient pregnant women. maximum contaminant level (MCL) at the While the cost of implementing a federal national level (Russell et al, 2009). If the drinking water standard is low compared to Federal Government implemented a MCL of previous limits, the cost would fall upon a 4µg/L, 3.4% of public water systems (PWS) few individuals. Clearly, there are many would be affected, and the net present value stakeholders and we hope the political (NPV) of compliance costs would be 2.1 process serves both sides of the debate billion USD. An MCL of 24µg/L would fairly. If a regulation is put in place, we affect 1% of PWS’s, and the NPV for would recommend the ion exchange method compliance would be 100 million USD. See as the most reliable and capable of removing Table 11. perchlorate from public water systems. According to the AWWA, the national cost for perchlorate remediation would be cheaper than previous contaminant regulations in the United States, but “…a small number of systems are carrying this cost burden and the cost implications to an individual system having to install perchlorate treatment would likely be significant (Russell et al, 2009).” They also say that if Congress decides to pursue a federal regulation for perchlorate in the future, this report will be a “key building block” for subsequent discussions of national cost. Table 11: National Cost of Federal  Regulation  MCL  % PWS  Cost (USD)  affected  4  3.4  2.1 billion  ppb  24  1  100 million  ppb  28