IN tE 1940s, a graduate student at ty of Cterson(anding, an Ioope measurement to try to get a definitive age for t last. Unfortunatelyall aminated—usually  contained somet ed to occur. Many years terson realized t ttable Oornamed thomas Midgley, Jr.

    Midgley raining, and t ayed so. Instead, erest in trial applications ofcry. In 1921, on,Oigated a compound called tetraetetraet it significantly reduced tion known asengine knock.

    Even to be dangerous, by tietury it could be found in all manner of consumer products. Food came in cans sealed er en stored in lead-lined tanks. It o fruit as a pesticidein te. It even came as part of toote tubes.  existed t didn’t bring a little lead into consumers’ lives. a greater and more lasting intimacy ts addition to gasoline.

    Lead is a neurotoxin. Get too muc and you can irreparably damage tral nervous system. Among toms associated s mostacute form it produces abrupt and terrifying ions, disturbing to victims andonlookers alike,   toget too muco your system.

    On to extract and  embarrassingly profitableto produce industrially—and tetraetably stop engines from knocking. So in1923 t corporations, General Motors, Du Pont, and Standard Oil ofNe enterprise called tion (later senedto simply Etion) o making as mucetraeto buy, and t proved to be a very great deal. tive “ethyl”

    because it sounded friendlier and less toxic troduced it for publicconsumption (in more  people realized) on February 1, 1923.

    Almost at once production o ex taggered gait and confusedfaculties t mark tly poisoned. Also almost at once, tionembarked on a policy of calm but unyielding denial t  rial cry,Promet one plant developed irreversible delusions, aspokesman blandly informed reporters: “t insane because too oget least fifteen ion ofleaded gasoline, and untold numbers of oten violently so; tnumbers are unknoo  times,  notably in 1924 ion y-five more urned into permanent staggering  a single ill-ventilated facility.

    As rumors circulated about t, et inventor,to ration for reporters to allay tted a tment to safety, etraet to y seconds, claiming all t  t , Midgley kneoo   near tuff if .

    Buoyed by turned to anotecors in ten appallingly risky because t sometimes leaked. One leak from a refrigerator at a al inCleveland, O out to create a gast able, nonflammable, noncorrosive, and safe to breatinct for ttable t  uncanny, ed chlorofluorocarbons, or CFCs.

    Seldom rial product been more sly or unfortunately embraced. CFCs into production in tions in everytioners to deodorant sprays before it iced, ury later, t tratosp a good thing.

    Ozone is a form of oxygen in ead oft is a bit of a cy in t at ground level it is a pollutant, osp is beneficial, since it soaks up dangerous ultraviolet radiation. Beneficial ozoneis not terribly abundant,  ributed evenly t tratosp one eig is urbed,and  take long to become critical.

    C very abundant—titute only about one part perbillion of tmosp travagantly destructive. One pound ofCFCs can capture and annie seventy tmospime—about a century on average—wreaking he while.

    t  sponges. A single CFC molecule is about ten times moreefficient at exacerbating greens tself as a green, cimately prove to be just about t invention of tietury.

    Midgley never kneructiveCFCs er becoming crippled ed a contraption involving a series of motorized pulleys t automaticallyraised or turned angled in tinto action and rangled.

    If you erested in finding out ty of Co be. illard Libby ing radiocarbon dating,alloists to get an accurate reading of to do before. Up to time, t reliable dates back no furt Dynasty in Egypt from about 3000B.C. No one couldconfidently say, for instance, ed or at ime in tted the caves of Lascaux in France.

    Libby’s idea   in 1960. It ion t all living tope of carbon calledcarbon-14,  a measurable rate tant t is, time it takes for o disappear1—of about 5,600 years,so by   a goodfix on t—to a point. After eigive carbon remains, tle to make a reliable measurement, soradiocarbon dating s up to forty thousand or so years old.

    Curiously, just as tecain fla becameapparent. to begin   one of ts of Libby’sformula, knoant,  3 percent. By time, s aken t tate everyone, scientists decided to keep te constant. “tim Flannery notes, “everyrae you read today is given as too young by around 3 percent.” t quite stop t  carbon-14 samples can beeasily contaminated iny scrap of vegetable matter, forinstance, t ed  noticed. For younger samples—ty t contamination does not alter somuc for older samples it can be a serious problem because so feoms arebeing counted. In t instance, to borro is like miscounting by a dollaro a t is more like miscounting by a dollar o count.

    Libby’s metion t t of carbon-14 in tmospe at t ory. In fact it  been. e no tmosp Eartism is deflecting cosmic rays,and t t can vary significantly over time. t some carbon-14 dates are more1If you oms determine  session, t t a statistical convenience-a kind ofactuarial table for elemental terial  isntt every atom in t for exactly 30 seconds or 60 seconds or 90 seconds or some otidilyordained period. Eacom  survive for an entirely random lengtime t o do iples of 30; it mig until t mige auries to come. No one can say. But  for te ofdisappearance s an average rate, in ot to any large sampling. Someone once , for instance, t dimes  30 years.

    dubious ticularly so es just around time t people firstcame to tter is so perennially in dispute.

    Finally, and pertle unexpectedly, readings can be t by seeminglyunrelated external factors—sucs of tested. Onerecent case involved te over s in  monks in amonastery graveyard  tial conclusion t t into doubt by tion t ten alot of fiso be older t t  got to tantalizinglyunresolved.

    Because of ted scomings of carbon-14, scientists devised oting ancient materials, among trons trappedin clays, and electron spin resonance, ic ions of trons. But even t oft date anyt 200,000 years, and t date inorganicmaterials like rocks at all, ermine t.

    ting rocks  one point almost everyone in t not been for a determined Englis migo abeyance altogether.

    acles s he achieved.

    By t offasement of ticularly in Britain, its spiritual birt Dury, ire geology department. Often o borrocoget inorder to pursue ric dating of rocks. At one point, ions ivelyed for ty to provide o drop out of academic life altogeto earn enougosupport ime le upon tyne—and sometimes even afford ty.

    tecically straiglyfrom t observed by Ernest Rutoms decayfrom one element into anot a rate predictable enoug you can use t takes for potassium-40 to become argon-40, and you measure ts of eac erial is. ributiono measure te of uranium into lead to calculate th.

    But tecies to overcome.  leasted gadgetry of a sort t could make veryfine measurements from tiny samples, and as  asimple adding mac e an ac  t least tunately,  yet anot to acceptance: tiveness of ists. Alto praise ained t  t merely terials fromwh had been formed.

    It  at time t y of Cing lead isotopes in igneous rocks ( edting, as opposed to ts). Realizing t tedious,  to young Clair Patterson as ation project.

    Famously terson t determining t, it ake years.

    Patterson began  in 1948. Compared ributions to tterson’s discovery of touciclimactic. For seven years, first at ty of Ctitute of tecerile lab,making very precise measurements of tios in carefully selected samples ofold rock.

    t you needed rocks t remely ancient, containing lead- and uranium-bearing crystals t  as old as t itself—anytes—but really ancient rocks are only rarely found on Earte 1940s no onealtogetood o t for e tectonics, o.) Patterson,meantime,  to try to make sense of ted materials. Eventually, andingeniously, it occurred to   tage by using rocksfrom beyond Earturned to meteorites.

    tion  correct as it turned out— manymeteorites are essentially leftover building materials from tem,and to preserve a more or less pristine interior cry. Measure th.

    As alraigionmakes it sound. Meteorites are not abundant and meteoritic samples not especially easy to get tecreme andneeded muc. Above all, t Patterson’s samples inuously and unaccountably contaminated mospo air. It  eventually led o create a sterile laboratory—t, according to at least one account.

    It took Patterson seven years of patient  to assemble suitable samples for finaltesting. In traveled to tional Laboratory in Illinois,ime on a late-model mass spectrograpectingand measuring te quantities of uranium and lead locked up in ancient crystals.  last s, Patterson ed t raigo o a al because   attack.

    Soon after a meeting in isconsin, Patterson announced a definitive age for t standsuncer,” as McGrayne admiringly notes. After th finally had an age.

    terson nourned tention to tion of all tlead in tmospounded to find t tle  tsof lead on  invariably  surprisingly, y years every study of lead’s effects urers of lead additives.

    In one sucudy, a doctor o breated quantities. tested. Unfortunately, as torappears not to  excreted as a e product. Rat accumulates int’s  so dangerous—and neitested. In consequence, lead was given a clean bill of h.

    Patterson quickly establis mospill do, in fact,since lead never goes a about 90 percent of it appeared to come fromautomobile ex pipes, but  prove it.  o comparelead levels in tmosp existed before 1923, raetroduced. It occurred to  ice cores could provide the answer.

    It  snoes into discrete annual layers(because seasonal temperature differences produce sligion from er tosummer). By counting back t of lead in eac global lead concentrations at any time for ion became tion of ice core studies, on wological work is based.

    Patterson found  before 1923 t no lead in tmosp since t time its level eadily and dangerously.   to get lead taken out of gasoline. to t end, ant and often vocalcritic of try and its interests.

    It o be a ion s directors  Justice Le Grosvenor of tional Geograpy.) Patterson suddenly foundresearc to acquire. troleum Institutecanceled a researcract ed States Public ral government institution.

    As Patterson increasingly became a liability to itution, trustees edly pressed by lead industry officials to s  o JamieLincoln Kitman, ing in tion in 2000, Etives allegedly offered to endoecterson  packing.” Absurdly, ional Researced to investigate tmospionably t on atmospheric lead.

    to  credit, Patterson never ually s led to troduction of t of 1970 and finally to ted States in 1986. Almost immediately lead levels in t. But because lead is forever, today 625 times more lead in our blood tury ago. t of lead in tmospinues to groe legally, by about a ric tons ayear, mostly from mining, smelting, and industrial activities. ted States also bannedlead in indoor paint, “forty-four years after most of Europe,” as McGrayne notes.

    Remarkably, considering its startling toxicity, lead solder  removed from Americanfood containers until 1993.

    As for tion, it’s still going strong, tandard Oil, and Du Pontno longer akes in t to a company called Albemarle Paper in1962.) According to McGrayne, as late as February 2001 Etinued to contend “tresearco s leaded gasoline poses a t to .” On its e, a ory of tion of lead—or indeedof t simply refers to t as containing “a certaincombination of chemicals.”

    Eto its 2001 company accounts,tetraetEL as it calls it) still accounted for $25.1 million in sales in 2000 (out ofoverall sales of $795 million), up from $24.1 million in 1999, but dos report tated its determination to “maximize ted bytEL as its usage continues to ps tEL t ed Octel of England.

    As for t to us by ted States, but tenacious little devils and any t youloosed into tmosps or ance)  certainly be around and devouring ozone long after you ill introducing s of CFCs into tmospoayne Biddle, 60 million pounds of tuff, ill finds its o t every year. So  is to say, many of our largecorporations are still making it at ts overseas. It  be banned in tries until 2010.

    Clair Patterson died in 1995.  ention from ury ofconsistent and increasingly selfless ac. A good case could be made t  influential geologist of tietury. Yet wterson?

    Most geology textbooks don’t mention  popular books on tory of ting of Eartually manage to misspell ure made tional, ratounding error of tterson was a woman.

    At all events, to tterson by 1953 t last  contained it.