Pb in DC Michael J Clarke Department of

Pb in DC Michael J Clarke Department of Chemistry Boston College Chestnut Hill, MA 02467 clarke@bc. edu © M. J. Clarke, Boston College 1

Pb in DC © M. J. Clarke, Boston College 2

Tap water in thousands of District houses has recently tested above the federal limit for lead contamination, a new phenomenon that has baffled the D. C. Water and Sewer Authority and forced the agency to begin replacing service pipes. Two-thirds of the 6, 118 residences that WASA tested last summer, or 4, 075 homes, had water that exceeded the lead limit of 15 parts per billion set by the Environmental Protection Agency in 1991. This is the first time the city's water has shown significant lead contamination since the late 1980 s, officials said. Four-year-old Michael Joseph often visits at the Georgetown home of his grandfather Charles Eason, whose tap water registered 36 times the EPA limit in the random testing. "It's shocking, " Eason said of the test results. © M. J. Clarke, Boston College 3

Council Furious With Water Agency Delayed Report of High Lead Levels Prompts Calls for Review By David Nakamura and Neely Tucker Washington Post, Sunday, February 1, 2004; Page C 01 Council Chairman Linda W. Cropp called for hearings on the lead issue Several D. C. Council members said yesterday that they were outraged that District leaders were not informed about lead contamination in thousands of city homes and called for an immediate review of the D. C. Water and Sewer Authority's performance. The city officials said they were not aware that tap water in 4, 075 homes had tested above the federal limit for lead until they read about the tests in yesterday's Washington Post. WASA, which first learned of lead contamination problems in 2002, should have been more diligent in informing the public and answering questions, they said. © M. J. Clarke, Boston College 4

Pb Service Lines © M. J. Clarke, Boston College 6

D. C. Water Worries Sellers, Buyers Real Estate Industry Unsure What to Do About Lead Reports By Sandra Fleishman, Washington Post Saturday, February 14, 2004; Page F 01 On Wednesday, at a news conference with the mayor and D. C. Council, WASA promised to send letters to owners of all 23, 000 properties that the agency believes have lead service lines. If those homeowners have concerns about the water, they can call WASA for information about testing. © M. J. Clarke, Boston College 7

Chlorine vs Chloramine Safe water is the biggest improvement in public health ever (more than antibiotics). Chlorine is an effective, persistent, and relatively safe bacterial disinfectant that has been used for about a century in municipal water supplies. One disadvantage is that chlorine interacts with organics to produce halogenated hydrocarbons, such as CHCl 3, etc, which are carcinogenic. © M. J. Clarke, Boston College 8

Experts Seek Answers On Tainted D. C. Water Panel to Study Abrupt Rise of Lead Levels in City By David Nakamura and D'Vera Cohn Washington Post, Sunday, February 8, 2004; Page C 01 A team of chemists, water-quality experts and engineers will gather in Washington this week in an attempt to answer a baffling question on a tight deadline: Why did lead levels in the tap water at thousands of city homes spike above federal safety limits? Scientists plan to conduct tests to determine whether new chemicals used to treat water for bacteria at the city's two treatment plants have a highly corrosive effect on service lines, allowing lead to dissolve from the pipes. They are especially interested in studying a compound called chloramine, a combination of chlorine and ammonia that the city's water treatment plants began using four years ago. Chlorine produces cancer-causing byproducts, so chloramine has become an increasingly popular alternative at water treatment plants across the country. The District is among about three dozen water systems nationwide whose lead tests have exceeded the federal safety standard since 2000, according to data supplied by the EPA. Most were in small communities. © M. J. Clarke, Boston College 9

Pb Increase Correlates with Chloramines p. H Raised with Ca. O NH 3 added to give Chloramines Grumbles & Welsh, WASA, House Testimony 3/5/04 © M. J. Clarke, Boston College 90% of the homes tested were under this level 10

Chloramine Chlorine is still added and converts to hypochlorous acid and hypochlorite Cl 2 + H 2 O H+ + Cl- + HOCl Ammonia is then added to form chloramines NH 3(aq) + HOCl NH 2 Cl + H 2 O Chloramines are more persistent oxidants than Cl 2 and lead to less CHCl 3 through CHBr 3 © M. J. Clarke, Boston College 11

© M. J. Clarke, Boston College Marc Edwards, Civil Engineering, Virginia Tech 12

Experimental data proving the adverse consequences of chloramines on lead leaching from certain types of brass. “Before” is simulated WASA water with free chlorine. “After” is the same water with chloramine. © M. J. Clarke, Boston College Marc Edwards, Civil Engineering, Virginia Tech 13

© M. J. Clarke, Boston College Marc Edwards, Civil Engineering, Virginia Tech 14

© M. J. Clarke, Boston College Marc Edwards, Civil Engineering, Virginia Tech 15

O 2 + Cu in Contact with Pb Sets up a Galvanic Cell 4 H+ + O 2 + 2 Pb 2+ + 2 H 2 O E = 0. 99 V © M. J. Clarke, Boston College 16

A Cu Pipe Preceding a Pb Pipe (or Pb solder) will Cause it to Dissolve Cu 2+ + 2 e- = Cu 0. 3419 Pb 2+ + 2 e- = Pb -0. 1262 Fe 2+ + 2 e- = Fe O 2 + 4 H+ + 4 e- = 2 H 2 O -0. 447 0. 86 Pb + Cu 2+ Cu + Pb 2+ E = 0. 47 V © M. J. Clarke, Boston College 17

District To Widen Testing For Lead Problem May Go Beyond 23, 000 Suspect Homes By Craig Timberg and Carol D. Leonnig Washington Post, Thursday, March 11, 2004; Page A 01 Federal and D. C. officials announced yesterday they would broaden testing of the city's water supply as Mayor Anthony A. Williams and others warned that lead contamination reaches beyond the homes known to have service lines made of the toxic metal. Corrosive water can leach lead from many sources, including brass fixtures and lead solder used to connect pipes, EPA officials said. © M. J. Clarke, Boston College 19

Preferred Methods Pb Analysis • Graphite-furnace atomic absorption (GFAA) • Anodic stripping voltammetry (ASV) © M. J. Clarke, Boston College D. S. Bannon, J. I. Chisholm, Clinical C 2001; 47: 1703 -1704. ) 20

An Immeasurable Threat in D. C. High Lead Levels Hurt Developing Children, But Scientists Say Danger Is Hard to Gauge By Avram Goldstein, Washington Post, Friday, February 20, 2004; Page B 01 News that lead in drinking water may exceed federal safety guidelines in thousands of District homes has raised anxieties among many parents of small children. But finding out whether this exposure to lead will have lasting consequences -- on intelligence, attention span and behavior -- generally takes years. Lead tricks brain cells into absorbing lead when they seek calcium, the most abundant mineral in the human body and one that is necessary to enable thoughts to form. Calcium is critical to cardiac health, the development of bones and teeth and other functions. © M. J. Clarke, Boston College 21

Increase in Miscarriages Coincided with High Levels of Lead in D. C. Water Late-term miscarriages and spontaneous abortions occurred at an unusually high rate among Washington women from 2000 through 2003 — during the same time frame that lead levels were dangerously high in the city’s drinking water. Carol D. Leonnig, Wahington Post, Dec. 9, 2013 Overall results are consistent with prior research linking increased lead exposure to higher incidence of miscarriages and fetal death, even at blood lead elevations (≈5 μg/d. L) once considered relatively low. Marc Edwards, Environmental Science and Technology, 2014, 48, 739 -46. © M. J. Clarke, Boston College 22

Other Uses of Lead • Paints, glazes, and other protective coatings. • Lead storage batteries, ceramics, plastics. • (CH 3 CH 2)4 Pb, antiknock fuel additive, reduced to 0. 1 g/gal in 1984. – 4 -5 million metric tons used in US. – Use stopped because of poisoning of car antipollution catalyst. – Additionally present in fossil fuels © M. J. Clarke, Boston College 23

Why is Pb 2+ Toxic Diagonal Relationships in the Periodic Table • There is a chemical resemblance between an element and the element one down and to the right • Diagonal relationships result from similarity in charge density (ratio of charge to ion size) • Because of the lanthanide contraction Ca 2+ and Pb 2+ have similar sizes. • So Pb 2+ can interfere with Ca 2+ metabolism, particularly in neuronal signalling. Ionic Radius (Å) Ca 2+ 1. 14 Pb 2+ 1. 19 © M. J. Clarke, Boston College Ca Pb 24

Important Biological Properties • Lead bioaccumulates in bones, teeth, nails, and hair. • Transferrable across the placental and bloodbrain barriers. • Multiple ingestion routes – by eating, drinking and breathing. • Treatable with chelation therapy © M. J. Clarke, Boston College 25

Chronic Exposure • Long term, low dose – Reproductive and early development • Various studies suggest fetal toxicity (birth outcome, growth, mental development) starts at a relatively low blood concentration, 8 -20 µg/d. L in the mother. – Cognitive and other neurobehavioral effects • CDC and the EPA have proposed a 10 µg/d. L blood concentration limit. © M. J. Clarke, Boston College 26

Neurodevelopmental Toxicity Mechanisms • Lead alters the effectiveness of the intracellular adhesion molecule in the brain, thereby affecting brain structural development. • Lead strongly interferes with the Ca 2+ messenger system. – Ca 2+ is used throughout the body as an intracellular messenger that converts electrical impulses to hormonal signals. – Pb 2+ either replaces or inhibits removal of Ca 2+. © M. J. Clarke, Boston College 28

Pb and IQ Environmental Health Perspectives Volume 113, Number 5, May 2005 © M. J. Clarke, Boston College 29

Epidemiology Study Included data from many earlier studies, which was corrected for numerous variables, i. e. , parents’ I. Q. , parents occupation, age, parents’ age, etc. © M. J. Clarke, Boston College 30

Effects on Reading © M. J. Clarke, Boston College 31

Pb & Violent Crime © M. J. Clarke, Boston College PLo. S Med. 2008, DOI: 10. 1371/journal. pmed. 0050101 Lauren K. Wolf, C&EN, 2/3/14, 92/5, 27 -29 32

Acute Pb Toxicity Blood concentration > 50 - 100 µg/d. L • Anemia, reduced red blood cell levels. Central nervous system – Encephalopathy: characterized by excess water in the brain. – Mechanism: blood/brain barrier properties altered as Pb 2+ substitutes for Ca 2+. Renal (kidney) system – Disturbs amino acid and glucose cycling. © M. J. Clarke, Boston College 33

Pb 2+ Binds in Place of Ca 2+ and Zn 2+ Lead binding to structural zinc-binding domains can be quantitatively determined by monitoring lead–thiolate charge-transfer bands in the ultraviolet. Competition experiments with zinc, the relative affinities of Pb and Zn were determined for a series of consensus zinc finger peptides with different metalbinding residues. Pb(II) binds 100 x more tightly than Xn(II) to Cys 4 sites in Zn-fingers and that Pb(II) can displace Zn(II) from these sites on a physiologically relevant timescale. © M. J. Clarke, Boston College H. A. Godwin, Current Opinion in Chemical Biology 2001, 5: 223– 227 34

Pb 2+ Binds in Place of Ca 2+ and Zn 2+ Lead targets proteins that naturally bind calcium and zinc. Including synaptotagmin, which acts as a calcium sensor in neurotransmission, and ALAD, the second enzyme in the heme biosynthetic pathway. Despite its size, lead (1. 19 Å, blue sphere and circles) can substitute for calcium (0. 99 Å, green spheres) in synaptotagmin and zinc (0. 74 Å, red spheres) in ALAD. © M. J. Clarke, Boston College H. A. Godwin, Current Opinion in Chemical Biology 2001, 5: 223– 227 35

Pb(II) displaces Zn(II) from sulfur-rich structural binding pockets in the proteins, causing them to fold improperly • Possibly because lead preferentially binds to only three sulfurs in a trigonal pyramidal configuration, even when additional sulfurs are available © M. J. Clarke, Boston College Godwin & Magyr, J. Am. Chem. Soc. 2005, 127, 9495 36

2+ Inhibits NMDA Receptor Pb • As childhood blood-lead levels increase, gray matter decreases in the ventrolateral prefrontal cortex and the anterior cingulate cortex, areas known for impulse control, emotional regulation, and decision making. • Lead might affect learning and intellect by inhibiting the N -methyl-d-aspartate receptor (NMDAR) on the surface of nerve cells that is activated by glutamate and glycine. • NMDAR inhibition reduces Ca 2+ uptake by nerve cells. Ca 2+ activates enzymes such as calmodulin kinase, which participates in strengthening nerve cell connections that form memories. PLo. S Med. 2008, DOI: 10. 1371/journal. pmed. 0050112 Brain Res. Rev. 2005, DOI: 10. 1016/j. brainresrev. 2005. 02. 004 © M. J. Clarke, Boston College 37

ALAD- Porphobilinogen Synthase is inhibited by Pb 2+ • The Zn enzyme, δ-aminolevulinic acid dehydratase (ALAD, also called porphobilinogen synthase), catalyzes the second reaction in the heme biosynthetic pathway. • Inhibition of this enzyme by the substitution of Zn 2+ by Pb 2+ explains (at least in part) the anemia often seen in adults and children with high BLLs. • This enzyme (of all Zn enzymes) is inhibited because it has a unique zinc-binding site with three cysteine residues. • When coordinated to –S-Cys, Pb 2+ exhibits intense lead–thiolate UV charge-transfer bands. © M. J. Clarke, Boston College H. A. Godwin, Current Opinion in Chemical Biology 2001, 5: 223– 227 38

Pb Effects on Zn-Fingers • Pb 2+ alters the structure of the zinc proteins to which it binds because of the differences in coordination preferences (6– 8 for Pb 2+ versus 4 for Zn 2+ and geometries (irregular for Pb 2+ versus Td for Zn 2+). • These results suggest that lead binding to structural zinc-binding domains should disrupt the DNA-binding activity of proteins and transcription factors results in pervasive neurological problems in both children and adults. © M. J. Clarke, Boston College H. A. Godwin, Current Opinion in Chemical Biology 2001, 5: 223– 227 39

Pb 2+ Effects on Neurons • • • Lead interferes with the ability of calcium to trigger exocytosis of neurotransmitters in neuronal cells, suggesting that lead might generally target proteins involved in calcium-mediated signal transduction. Picomolar concentrations of lead can activate calcium-dependent PKC, which is involved in the regulation of cell growth, learning and memory. Pb 2+ appears to bind to the C 2 domain of PKC, which contains a multinuclear binding site on an exposed loop that normally binds phospholipids in a Ca-dependent fashion. Pb 2+ promotes phospholipid binding more than Ca 2+. There are C 2 domains in synaptotagmin, which acts as a calcium sensor in neurotransmission. Nanomolar Pb 2+ promotes binding of synaptotagmin to phospholipids, but interferes with its ability to bind to its protein partner, syntaxin, which may explain why Pb 2+ interferes with calcium-triggered neurotransmitter release. EF-hand calcium proteins, such as calmodulin, can be activated by Pb 2+, but only at μM concentrations. © M. J. Clarke, Boston College H. A. Godwin, Current Opinion in Chemical Biology 2001, 5: 223– 227 40

Unusual Geometry-Steric Lone Pair Inert-Pair Effect Relativistic effects cause the 6 s electrons to be held tighter and not enter into covalent bonding Because the center of charge for the metal ion is different from that of the 6 s 2 lone pair, metal–ligand bonds in the direction of the lone pair are longer than those facing away from the lone pair. © M. J. Clarke, Boston College L. Shimoni-Livny, J. P. Glusker, C. W. Bock, Inorg. Chem. , 37 (8), 1853 -1867, 1998 41

Stereochemistry of Pb(II) Compounds • Hemidirected for low coordination numbers (2 -5) • Holodirected for high coordination numbers (9 -10) • Either for intermediate coordination numbers (6 -8) © M. J. Clarke, Boston College L. Shimoni-Livny, J. P. Glusker, C. W. Bock, Inorg. Chem. , 37 (8), 1853 -1867, 1998 42

Steric Lone Pair in Pb 2+ • Converting a hemidirected complex into a holodirected complex requires approximately 8 -12 kcal/mol for the simple formally uncharged ligands NH 3, PH 3, OH 2, and SH 2. Interactions between ligands can increase or decrease this energy cost significantly. • The lone pair of electrons on the Pb(II) in the hemidirected complexes is primarily 6 s, polarized by a surprisingly small p contribution that is responsible for the void in the distribution of ligands. • The lone pair orbitals in the holodirected complexes are entirely s in character. • For hemidirected Pb(II) complexes, charge is transferred from the ligands to the lead. As the electronegativity of the liganding group decreases, more charge is transferred to the 6 p orbitals on the lead. This added charge does not increase the p character of the lone pair orbitals, but increases the p character of the Pb. II-X bonding orbitals, resulting in a decrease in the exterior X-Pb. II-X angles. • The two shorter Pb. II-X bonds in the hemidirected four-coordinate complexes have greater covalent character than do the two longer Pb. II-X bonds. © M. J. Clarke, Boston College 43

Pb Chelation Therapy • Succimer (meso-2, 3 -dimercaptosuccinic acid, DMSA) is the drug of choice for Pb 2+ chelation therapy and is also recommended for asymptomatic children with blood lead levels 40 – 70 mg/d. L. • Next are Ca. Na 2 EDTA • D-penicillamine © M. J. Clarke, Boston College 44

Clinical Metal Ion Chelating Agents Could a chelating agent take advantage of the stereochemical lone-pair effect to be particularly effective at eliminating Pb 2+ ? © M. J. Clarke, Boston College Environmental Health Perspectives Supplements Volume 110, Number S 5 October 2002 45

Lewisite British Anti-Lewisite (BAL) Lewisite is named after the US chemist and soldier Winford Lee Lewis (1878 -1943). In 1918 he found thesis of Julius Arthur Nieuwland at Maloney Hall, a chemical laboratory at The Catholic University of America, Washington DC in which Nieuwland detailed the synthesis by the combination of arsenic trichloride with acetylene in an hydrochloric acid solution of mercuric chloride. After receiving the first Ph. D. in chemistry from CUA in 1904, Nieuwland returned to Notre Dame as professor of botany (until 1918), then professor of organic chemistry (until 1936). In 1920, Nieuwland successfully polymerized acetylene into divinylacetylene. Elmer Bolton, the Director of Research at Du. Pont, used this basic research during the development of neoprene. When he was 22, Knute Rockne had saved enough money to continue his education and headed to South Bend, Indiana. He was the laboratory assistant to noted polymer chemist Julius Arthur Nieuwland at Notre Dame, but rejected further work in chemistry after receiving an offer to coach football. © M. J. Clarke, Boston College 46

Lead Nephropathy • Lead induces acute nephrosis of the proximal tubule and affects blood pressure to the kidney. • Low molecular weight proteins bind Pb 2+, leading to resorption by endocytosis. • Cellular and mitochondrial swelling, enlarged nucleus (karyomegaly), mitosis and intranuclear inclusion bodies are seen. • Decreased tubular resorption of glucose, phosphate and amino acids +/- proteinuria • Chronic exposure causes tubulo-interstitial disease. © M. J. Clarke, Boston College 47

Lead Levels in Water Misrepresented Across U. S. Utilities Manipulate or Withhold Test Results to Ward Off Regulators Cities across the country are manipulating the results of tests used to detect lead in water, violating federal law and putting millions of Americans at risk of drinking more of the contaminant than their suppliers are reporting. Nimi Sandhu of Seattle worries that lead in the water may have endangered her children. Photo Credit: Patrick Hagerty For The Washington Post Some cities, including Philadelphia and Boston, have thrown out tests that show high readings © M. J. Clarke, Boston College 48

Chloramine and Elevated Pb Levels in Drinking Water Jay A. Switzer, University of Missouri-Rolla SGER CHE-0437346 Although NH 2 Cl may produce less chlorinated hydrocarbons than OCl- when used as a disinfectant in drinking water, it may lead to increased Pb levels. A 0. 5 µm thick Pb film nearly completely dissolves in a NH 2 Cl solution, but it is passivated in a OCl- solution by the formation of insoluble Pb. O 2 (Environmental Scuence & Technology, 2006). OCl- NH 2 Cl © M. J. Clarke, Boston College 49

Lime Juice? Or Ca. O? New Water Treatment Proposed for Maui Timothy Hurley, Honolulu Advertiser, Thursday, May 20, 2004 WAILUKU, Maui — The Maui Department of Water Supply wants to try yet another chemical additive in the Upcountry water supply in an attempt to relieve residents of skin rashes, itching and other health problems. The complaints started after June 2001, when the Department of Water Supply began adding zinc orthophosphate, a compound designed to control high levels of lead caused by leaching of pipes in older homes. Responding to public pressure last year, the water department switched to phosphoric acid, but the complaints persisted. Squires joined other speakers in calling for an immediate halt to use of phosphoric acid, which also is used in the manufacture of fertilizers, pharmaceuticals and detergents, and as a flavoring agent in soda pop, beer, jams and jellies, and cheeses. Department spokesperson Jacky Takakura said yesterday that officials will seek state permission to use food-grade lime as an alternative to the phosphoric acid added to the water to reduce high levels of lead. © M. J. Clarke, Boston College 50

Montgomery Tests Delay School Lead Remediation In Pr. George's, Replacement of Drinking Fountains Underway By Amit R. Paley, Washington Post, Sunday, August 29, 2004; Page C 01 The school system then began retesting those 256 sources to determine the source of contamination. Initial test results indicate the cause in almost all cases is the fixtures, which prior to 1986 were soldered with lead. Schools across the country are finding that fixtures are the primary source of lead, said Stephen Gerwin, operation support manager at WSSC. © M. J. Clarke, Boston College 51

WASA Affirms 10 -Minute Pipe Flush High Lead Levels Cut By 95%, Agency Says By Craig Timberg and David Nakamura Tuesday, March 9, 2004; Page B 01 Recent tests at D. C. homes with high levels of lead contamination in the water showed that running the taps for 10 minutes eliminated 95 percent of the lead, rendering the water safe to drink in most cases, water authority officials said. WASA retested 96 homes with lead concentrations above 300 parts per billion, 20 times the Environmental Protection Agency's "action level. " © M. J. Clarke, Boston College 53

Mail 23, 000 Water Filters, Williams Tells WASA By Craig Timberg and Petula Dvorak Wednesday, March 17, 2004; Page A 01 Mayor Anthony A. Williams instructed D. C. Water and Sewer Authority officials yesterday to begin mailing free water filters to each of the 23, 000 homes in Washington known to have lead service lines. "Every one of the 23, 000 homes will get a filter shipped to their door, " Williams (D) announced to a group of about three dozen residents meeting last night at Shiloh Baptist Church in Northwest Washington to discuss the city's lead problem. © M. J. Clarke, Boston College 54

A Solution? In Lead Crisis, Aqueduct Adjusts Chemical Cocktail By Marc Fisher Washington Post, Tuesday, March 23, 2004; Page B 01 Treating water is the kind of job that chemists love. There is no perfect mix, and each city uses a different approach. Bottom line: "Water is corrosive by definition, " Jacobus says. "The purer the water, the faster it will rust metal. " The trick is to find the optimal balance of chemicals to produce safe water that is also tasty and pleasant to the nose. If the Potomac delivers more muck than usual, the aqueduct adjusts the levels of alum, lime or other chemicals in the recipe for Washington water. But there is no such thing as a perfect solution: Treating water introduces chemicals, which have their own downside. The corrosion inhibitor to be added this summer is made from phosphates, which were removed from cleansers some years back because of environmental concerns. © M. J. Clarke, Boston College 55

Solubility of Lead Phosphate Compound Log(Ksp) Pb. Cl 2 -4. 77 Pb 3(PO 4)2 -42 Pb 3(HPO 4)3 -9. 6 Pb. CO 3 -6. 77 Pb(OH)2 -7. 11 © M. J. Clarke, Boston College See Schock, JAWWA, 75(2), 1987), and http: //personal. stevens. edu/~dvaccari/lead. xls 56

Bacteria Put D. C. Water in Breach Levels Violate Health Standard By D'Vera Cohn, Washington Post, Friday, September 24, 2004; Page B 01 Bacteria levels in D. C. tap water exceeded federal health standards this month for the first time since 1996, city and Environmental Protection Agency officials announced yesterday, but they said most people are not at risk. The sudden rise in bacteria, detected in routine testing this month, probably stemmed from use of a new water treatment chemical intended to reduce lead levels in the water at thousands of city homes, officials said during a news conference. They said the chemical, orthophosphate, may have shaken off a layer of rust and bacteria inside city water pipes. Phosphate is a fertilizer and nutrient needed for cell growth. © M. J. Clarke, Boston College 57

High Lead Found in Boston Area Water EPA-State Decision Influenced by D. C. Utility's Handling of Contamination By Carol D. Leonnig, Washington Post, Wednesday, April 28, 2004; Page A 02 Federal and state regulators ruled yesterday that the drinking water delivered to 2. 5 million customers in the Boston region has lead levels above the acceptable national standard MWRA … was seeking to invalidate tests from 18 households, most with high lead levels. Approval of the rare request would have allowed the utility to declare itself in compliance with federal law. The MWRA had unsafe lead levels from 1997 to 2001, forcing Boston to replace hundreds of lead service lines. But the utility was in compliance in 2002 and 2003. Last year, the utility declared that it had reduced its lead levels to a safe level. State environmental authorities considered allowing the MWRA to strike 18 samples out of 425 taken in the required annual measurement of the region's water quality. © M. J. Clarke, Boston College 58

MWRA Pb Levels Chloramine Added In 1997 Ca. O Added In 1996 © M.

MWRA says water tastier because of different treatment Agency's director warns that rates could rise 9% Stephanie Ebbert, Boston Globe, June 8, 2006 Good news is coming from the Massachusetts Water Resources Authority: The water is not only safe to drink, it tastes better. In July, the system's John J. Carroll Water Treatment Plant in Marlborough began using ozone gas bubbles to kill germs, resulting in fewer potentially harmful byproducts of chlorination and better taste. ``It tastes great and it's clean as a whistle, " said Frederick A. Laskey , MWRA executive director. On the financial front, however, MWRA rates are expected to climb 5 percent to 9 percent this summer, Laskey said. Although the system as a whole did not exceed standards for lead in drinking water, Laskey said, lead was detected in water samples taken in March in six communities -- Boston, Framingham, Malden, Milton, Quincy, and Winthrop. © M. J. Clarke, Boston College 60

Summary • Relativistic effects affect stereochemistry • Diagonal relationships with Zn 2+ and Ca 2+ • Binds to synaptotagmin, which acts as a Ca 2+ sensor in neurotransmission and interferes with its ability to bind to its protein partner, syntaxin. • Binds to Zn-finger transcription factors • Binds to Zn-porphobilinogen synthase • Interferes with neuronal development © M. J. Clarke, Boston College 61

Links Washington Post provides access to all Pb articles since January 31, 2004 http: //www. washingtonpost. com/wp-dyn/metro/specials/water/ House Committee on Government Reform Hearing on The Federal Role in Ensuring Safe Drinking Water in the District of Columbia and Senate Committee on the Environment http: //reform. house. gov/Gov. Reform/Hearings/Event. Single. aspx? Event. ID=797 http: //epw. senate. gov/hearing_statements. cfm? id=220280 Time Magazine: http: //www. time. com/time/magazine/article/0, 9171, 1101040405 -605469, 00. html © M. J. Clarke, Boston College 62

ION Coord. # Ionic Radius Z/I. R. Pb 2+ 6 1. 19 1. 68 Pb 2+ 8 1. 29 1. 55 Pb 2+ 10 1. 43 Ca 2+ 6 1. 00 2. 00 Ca 2+ 8 1. 12 1. 79 Ca 2+ 10 1. 23 1. 63 Zn 2+ 4 0. 60 3. 33 Zn 2+ 6 0. 74 2. 70 Zn 2+ 8 0. 90 2. 22 Mg 2+ 4 0. 57 3. 51 Mg 2+ 6 0. 72 2. 78 Mg 2+ 8 0. 89 2. 25 Cd 2+ 4 0. 78 2. 56 Cd 2+ 6 0. 95 2. 11 Cd 2+ 8 1. 10 1. 82 Cd 2+ 12 1. 31 1. 53 Charge to Radius Ratio Pb 2+ affects processes in the body that involve calcium. A comparison of charge to radius ratios (last column) points to similarities between the Pb 2+ and Ca 2+. © M. J. Clarke, Boston College 64 http: //stage. cchem. berkeley. edu/knrgrp/public_html/radii. html