Flu­o­ride in wa­ter safe, ef­fec­tive, ex­perts say

Cau­tion urged over study sug­gest­ing link be­tween ad­di­tive and low IQ scores

The Peterborough Examiner - - Arts & Life - BEN GUARINO

A study of young chil­dren in Canada sug­gests those whose moth­ers drank flu­o­ri­dated tap wa­ter while preg­nant had slightly lower IQ scores than chil­dren whose moth­ers lived in non-flu­o­ri­dated cities.

But don’t dash for the near­est bot­tled wa­ter yet. Health ex­perts at the Amer­i­can Academy of Pe­di­atrics and the Amer­i­can Den­tal As­so­ci­a­tion cau­tioned that pub­lic pol­icy and drink­ing wa­ter con­sump­tion should not change on the ba­sis of this study.

“I still stand by the weight of the best avail­able ev­i­dence, from 70 years of study, that com­mu­nity wa­ter flu­o­ri­da­tion is safe and ef­fec­tive,” said Brittany Sey­mour, a den­tist and spokesper­son for the Amer­i­can Den­tal As­so­ci­a­tion.

“If we’re able to repli­cate find­ings and con­tinue to see out­comes, that would com­pel us to re­visit our rec­om­men­da­tion. We’re just not there yet.”

The Amer­i­can Academy of Pe­di­atrics, like­wise, rec­om­mends flu­o­ride in tooth­pastes and tooth var­nishes for chil­dren be­cause the min­eral pre­vents tooth de­cay. In drink­ing wa­ter, “flu­o­ri­da­tion has been in­cred­i­bly pro­tec­tive,” said Aparna Bole, a pe­di­a­tri­cian who chairs the Coun­cil on En­vi­ron­men­tal Health at the Amer­i­can Academy of Pe­di­atrics.

Flu­o­ri­da­tion re­duces the preva­lence of cav­i­ties by about one-fourth, ac­cord­ing to the Cen­ters for Dis­ease Con­trol and Preven­tion. The CDC con­sid­ers wa­ter flu­o­ri­da­tion one of the 10 top health achieve­ments of the past cen­tury, on par with vac­cines and an­ti­smok­ing cam­paigns.

Bole called the new study, pub­lished Mon­day in JAMA Pe­di­atrics, “an im­por­tant ad­di­tion to our body of knowl­edge. It sup­ports the pub­lic health com­mu­nity’s on­go­ing re-eval­u­a­tion of op­ti­mal flu­o­ri­da­tion lev­els in drink­ing wa­ter.”

In Jan­uary 1945, re­searchers added flu­o­ride to mu­nic­i­pal wa­ter in Grand Rapids, Mich., the first pro­gram to en­list flu­o­ride to pro­tect a city’s teeth. Op­po­nents of flu­o­ri­da­tion have since raised con­cerns both lu­di­crous — flu­o­ri­da­tion is not a com­mu­nist plot — and le­git­i­mate, such as flu­o­ro­sis. In the mild form of flu­o­ro­sis, faint white streaks ap­pear on the teeth of young chil­dren. Se­vere flu­o­ro­sis, which is much rarer, dam­ages bones.

Dozens of cities in the United States and Canada, such as Port­land, Ore­gon, and Van­cou­ver, do not add flu­o­ride to city wa­ter. Else­where in the United States, flu­o­ri­da­tion is the norm.

In 2015, to re­duce the risk of mild flu­o­ro­sis, the Depart­ment of Health and Hu­man Ser­vices cut its flu­o­ride rec­om­men­da­tions al­most in half, from 1.2 mil­ligrams per litre to 0.7 mil­ligrams per litre.

Few older stud­ies ad­dressed po­ten­tial risks, or the lack thereof, as­so­ci­ated with flu­o­ride ex­po­sure dur­ing preg­nancy, said study au­thor Chris­tine Till, a neu­ropsy­chol­o­gist at York Univer­sity in Toronto. She added that “whether we found an ef­fect or not, the data would be re­ally rel­e­vant be­cause we would then ad­dress that gap in our knowl­edge.”

Till and her col­leagues ac­quired data and frozen urine sam­ples pre­vi­ously col­lected by Ma­ter­nal-Infant Re­search on En­vi­ron­men­tal Chem­i­cals, or MIREC. That project, run by Canada’s pub­lic health depart­ment, stud­ied thou­sands of moth­ers who gave birth be­tween 2008 and 2012. MIREC re­searchers measured the tod­dlers’ IQ af­ter the chil­dren turned 3.

Preg­nant women re­ported their con­sump­tion of tap wa­ter and black tea, which is high in flu­o­ride, in ques­tion­naires. The authors of the new study also cal­cu­lated the amount of flu­o­ride in mu­nic­i­pal wa­ter, based on the lev­els at waste­water treat­ment plants linked to the women’s postal codes. The re­searchers es­ti­mated the women’s flu­o­ride intake based on a com­bi­na­tion of those mea­sures.

The re­searchers com­pared the flu­o­ride intake of 400 women, some who lived in flu­o­ri­dated cities and some who did not. They con­trolled for fac­tors such as house­hold in­come and the women’s ed­u­ca­tion. A 1-mil­ligram in­crease in flu­o­ride intake was as­so­ci­ated with a 3.7-point drop in chil­dren’s IQ, they found.

As an ad­di­tional step, Till and her col­leagues measured flu­o­ride biomark­ers in urine from 500 preg­nant women, col­lected dur­ing each trimester. Flu­o­ride con­tent in urine was only mod­er­ately re­lated to the es­ti­mates of the moth­ers’ flu­o­ride intake, sug­gest­ing that nei­ther was a per­fect mea­sure of how much flu­o­ride a preg­nant woman drank.

The sci­en­tists ob­served that a 1-mil­ligram-per-litre in­crease in urine flu­o­ride pre­dicted a drop in IQ of 4.5 points in young boys. When the re­searchers ex­am­ined urine of moth­ers who had daugh­ters, how­ever, flu­o­ride had no as­so­ci­a­tion with IQ.

Pre­vi­ous ob­ser­va­tional stud­ies claimed to find re­la­tion­ships be­tween flu­o­ride and IQ, but most were “of poorer qual­ity due to var­i­ous weak­nesses in study de­sign,” said David Bellinger, an ex­pert in neu­roepi­demi­ol­ogy at Bos­ton Chil­dren’s Hospi­tal who was not as­so­ci­ated with this study. The meth­ods in this re­port, he said, are “very sim­i­lar” to stud­ies that showed low-dose lead and pes­ti­cide tox­i­c­i­ties.

But he called for fur­ther re­search. “Gen­er­ally, no sin­gle epi­demi­o­log­i­cal study set­tles a ques­tion like this,” Bellinger said.

“The de­ci­sion to pub­lish this ar­ti­cle was not an easy one,” said Dim­itri Chris­takis, the edi­tor of JAMA Pe­di­atrics and a pe­di­a­tri­cian at Seat­tle Chil­dren’s Hospi­tal.

Chris­takis ap­pended a note to the study, a first in his ca­reer, ex­plain­ing that the jour­nal sub­jected the pa­per to “ad­di­tional scru­tiny.” This in­cluded mul­ti­ple statistica­l re­views, he said.

“The find­ings are what they are,” Chris­takis said. “There is clearly an as­so­ci­a­tion. It by no means proves defini­tively that this is a risk.”

Sev­eral re­searchers un­af­fil­i­ated with the re­port ap­plauded this work’s pub­li­ca­tion in the face of in­tense re­view.

“I be­lieve that, in gen­eral, the den­tal com­mu­nity will dis­count these find­ings, minimize their im­por­tance and con­tinue to rec­om­mend the use of flu­o­ri­dated wa­ter dur­ing preg­nancy,” said Pamela Den Besten, a pe­di­atric den­tist who stud­ies tooth enamel at the Univer­sity of Cal­i­for­nia, San Fran­cisco. She added: “This study has been care­fully con­ducted and an­a­lyzed.”

“This is an ex­cel­lent study,” said Philippe Grand­jean, a physi­cian who stud­ies brain de­vel­op­ment and en­vi­ron­men­tal pol­lu­tants at the Har­vard School of Pub­lic Health. “CDC has to come out and look at the risk-ben­e­fit ra­tio again be­cause they can’t con­tinue re­ly­ing on stud­ies that were car­ried out decades ago.”

The CDC de­clined to com­ment on the study be­cause it was not a par­tic­i­pant, said Amesheia Buck­ner, an agency spokesper­son.

“Com­mu­nity wa­ter flu­o­ri­da­tion is one of the most prac­ti­cal, cost-ef­fec­tive, eq­ui­table and safe mea­sures com­mu­ni­ties can take to pre­vent tooth de­cay,” Buck­ner said.

The study has flaws, said John Ioan­ni­dis, a Stan­ford Univer­sity meta-sci­en­tist and the au­thor of an in­flu­en­tial 2005 pa­per, “Why Most Pub­lished Re­search Find­ings Are False.”

“It has ma­jor draw­backs in terms of how the mea­sure­ments have been made,” Ioan­ni­dis said. “The re­sults are very bor­der­line in terms of statistica­l sig­nif­i­cance.” It’s a weak­ness, he said, that the self-re­ported con­sump­tion was not linked di­rectly to lev­els of flu­o­ride measured in bod­ily flu­ids.

What’s more, the sex dif­fer­ence in IQ — the drop ob­served for boys but not girls — “makes no sense,” he said. “If you see a gen­der dif­fer­ence claim for this type of as­so­ci­a­tion, it’s far more likely to be a spu­ri­ous find­ing rather than some­thing true.”

Bole agreed.

“I just don’t know how to in­ter­pret that,” she said.

Some physi­cians of­fered ad­vice based on this study. “The an­swer for me, I can say, is I would not have my wife drink flu­o­ri­dated wa­ter” if she were preg­nant, Chris­takis said. Grand­jean, like­wise, sug­gested moth­ers drink bot­tled wa­ter and limit black tea to a sin­gle cup per day.

Oth­ers did not. “I’m hop­ing peo­ple don’t con­clude on the ba­sis of this one study, ‘Oh boy, we should all be drink­ing bot­tled wa­ter.’ No,” Bole said. “Tap wa­ter in most com­mu­ni­ties is the health­i­est and most en­vi­ron­men­tally re­spon­si­ble choice.” And adding more re­stric­tions to what preg­nant women can con­sume, Ioan­ni­dis said, cre­ates a “bur­den of fea­si­bil­ity.”

Sey­mour said the dam­age from den­tal dis­ease goes beyond teeth. “Kids in the

U.S. who don’t have ac­cess to com­mu­nity wa­ter flu­o­ri­da­tion have sig­nif­i­cantly higher den­tal dis­ease, and we know that im­pacts their abil­ity to learn and grow,” she said, in­clud­ing harm to sleep, self-esteem and school per­for­mance.

Sey­mour, whose young daugh­ter drinks city wa­ter, would “hon­estly be more con­cerned if there was a de­ci­sion to stop flu­o­ri­dat­ing our wa­ter,” she said.

Ioan­ni­dis’s stance “on whether flu­o­ride ex­po­sure dur­ing preg­nancy is a bad thing for the IQ of the child goes up about three­fold,” he said.

“If you thought that it was maybe 1 per cent likely to be true, that 1 per cent now would be­come 3 per cent. It would still not be true.”


Dozens of cities in the United States and Canada, in­clud­ing Port­land, Ore., and Van­cou­ver, do not add flu­o­ride to the mu­nic­i­pal wa­ter sup­ply.

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