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Peut-on comparer e-cigarette et cigarette ? – 27 aout 2013 – sciences et avenir

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QUESTIONS. Un millilitre de e liquide ce m lange de propylene glycol et de nicotine avec lequel on recharge les cartouches des cigarettes lectroniques quivaut il vraiment a un paquet de 20 cigarettes a combustion et un flacon de 10 ml a une cartouche , comme l annoncent des sites de vente de cigarettes lectroniques ? Le dosage en nicotine de 11 mg/ml est il recommand pour les fumeurs de 10 a 12 cigarettes ? Et celui de 16 mg/ml pour les gros fumeurs de 15 cigarettes et plus ? Peut on garantir que le dosage de 11 mg/ml correspond bien aux cigarettes light, celui de 16 mg/ml aux blondes (voir notre tableau)?

Surtout, ne vous fiez pas a ces arguments souvent entendus ! Encore moins a cette regle apparemment simple selon laquelle il suffit de multiplier le taux inscrit sur votre paquet de cigarettes par le nombre de cigarettes fum es par jour pour choisir le dosage de son e liquide ! Sciences et Avenir a men l enqu&ecirc te tout est beaucoup plus compliqu qu annonc ! Et vous livre les cl s pour comprendre.

1 La teneur en nicotine des e liquides n est pas toujours celle indiqu e sur le flacon

En France, on trouve des flacons de 10 ml et de 30 ml, dos s entre z ro et 19,9 mg de nicotine/ml (notre tableau). Des analyses men es par la FDA (Food and drug administration am ricaine) et l universit Queen Mary de Londres montrent que les indications peuvent &ecirc tre fantaisistes. Sur 16 marques test es (dont certaines peuvent &ecirc tre disponibles en France via l Internet) seules trois affichaient la teneur correcte ! L cart pouvait atteindre 20 % de plus ou de moins. Mieux ! Certains flacons, r put s contenir z ro nicotine, en contenaient. a ce stade de notre enqu&ecirc te, il ne nous est pas possible de dire quelles marques en France seraient fiables ou non. On voit donc l int r&ecirc t d une r glementation et d un contr&ocirc le de ce type de produits.

2 Il y a d perdition de nicotine entre le liquide et l a rosol

On ne peut pas savoir avec exactitude le taux de nicotine inhal e. En effet, la vaporisation de la nicotine c est a dire son passage de liquide a l tat d a rosol apres avoir t chauff e par la batterie differe norm ment selon les modeles d e cigarettes, dont le dispositif de chauffage peut &ecirc tre plus ou moins efficace. Quoi qu il en soit, pres de 60 % en moyenne de la nicotine (de 21 a 85 %) pr sente dans une cartouche est effectivement vaporis e, selon des travaux de l universit Queen Mary (Londres). Et seule une partie de la nicotine est ensuite inhal e, selon les chercheurs, qui aimeraient que l on d veloppe de meilleurs moyens pour mesurer cette ingestion ! Cons quence se baser sur la teneur en nicotine annonc s sur les flacons de e liquide conduit a surestimer la dose r ellement ing r e.

3 C est l a rosol (ou e vapeur) qu il faut comparer a la fum e, mais la encore c est compliqu

Des tudes ont montr que la d livrance de nicotine n est pas continue ni uniforme lors du vapotage, sa densit varie et aurait tendance a augmenter apres 150 bouff es. Par ailleurs, la dur e, le rythme des inhalations varie fortement entre fumeurs et vapoteurs. Mais des chercheurs ont toutefois tent d effectuer des quivalences.

C est le cas de Macje Goniewicz , de l universit Queen Mary a Londres, qui a d velopp des “machines a vapoter” (comme il existe des “machines a fumer” chez les cigarettiers traditionnels) inspir es du comportement de dix “vapoteurs” observ s pendant un mois. Il a ainsi pu tester une douzaine de marques de e cigarettes polonaises, am ricaines et britanniques plus ou moins fortement dos es en nicotine. C est la seule tude un peu fouill e sur le sujet a ce jour, parue dans la revue Nicotine and Tobacco research de janvier 2013.

Nous sommes partis du principe qu une s rie de 15 inhalations d une e cigarette quivaut a fumer une cigarette traditionnelle, explique Macje Goniewitcz, galement affil a l universit de Sil sie (Pologne). Cette s rie d livre entre 0,025 a 0,77 mg de nicotine. C est moins que la dose d livr e par une cigarette entierement fum e, estim e entre 1,54 mg et 2,60 mg, selon les tests effectu s par Mirjana Djordjevic et ses collegues de l American Health foundation (AHF) en 2000 sur des cigarettes l geres, moyennes et plus fortes.

Deux pr cisions s imposent cependant Goniewicz compare ses r sultats sur la e cigarette a ceux de l AHF sur la cigarette traditionnelle. Or l AHF, un centre am ricain de pr vention du cancer qui a fait une faillite frauduleuse en 2004 avait utilis pour cette tude des machines a fumer sp ciales, mimant le comportement des fumeurs, mais qui ne sont toujours approuv es par les autorit s (lire ci dessous).

Par ailleurs son calcul inclut des cigarettes traditionnelles fortement dos es en nicotine (1,2 mg) et interdites de commercialisation en Europe. Naturellement, l industrie du tabac conteste ces chiffres en les minorant. Ainsi, selon British American Tobacco, la fum e de cigarette contiendrait seulement entre 0,05 mg et 0,2 mg de nicotine par bouff e de 70 ml. Elle a utilis des machines a fumer en vigueur, approuv es par les autorit s mais extr&ecirc mement critiqu es par les tabacologues (lire encadr ).

C est la que subsiste le dernier cueil pour qui veut comparer e cigarettes et cigarettes traditionnelles les sp cialistes s charpent sur la meilleure facon de calculer la teneur en nicotine d une cigarette a combustion.

Quid de l exercice qui consiste a valuer la teneur d un flacon e liquide, avec la teneur en nicotine/cigarette, affich e sur les paquets ?

Math matiquement, c est stupide commente Bernard Dautzenberg. Mais cela peut constituer un premier indicateur pour le vapoteur et l aider a valuer par quel dosage en nicotine commencer. Par la suite, le vapoteur adaptera selon ses besoins, sa perception, le hit sensation de br&ucirc lure de nicotine qu il recherche. En principe la sensation de manque devrait disparaitre avec un juste dosage. Car rappelons le, la nicotine est une drogue.

4 La v ritable teneur de la fum e en nicotine n est pas indiqu e sur les paquets de cigarettes traditionnelles

Un cylindre de cigarette contient entre 12 et 18 mg de nicotine naturellement pr sente dans la plante de tabac commun (Nicotiana tabacum).

La fum e d une cigarette, elle, contiendrait de 0,1 a 0,8 mg de nicotine, selon les indications port es sur le paquet (voir notre tableau). Mais ces mesures ne seraient pas fiables, selon de nombreux scientifiques elles sont en effet obtenues par les machines a fumer, mises au point par les industriels. L aspiration m canique des machines a fumer ne reproduit pas le comportement tabagique humain et sous estime syst matiquement le comportement r el pointe ainsi Greg Connolly, du Centre de contr&ocirc le du tabac de Boston.

Le manque de fiabilit de ces machines a t mis en lumiere apres les tests apparemment positifs de cigarettes abusivement dites “l geres” (en nicotine, en goudron etc) Alors que dans la r alit les fumeurs ont tendance a prendre des bouff es plus fortes et plus fr quentes pour obtenir leur dose en substance psychoactive. Pour le pneumologue Bertrand Dautzenberg qui privil gie des m thodes de calcul plus s veres mises au point par des canadiens, il faut multiplier les chiffres des fabricants par trois a six pour obtenir un r sultat plausible (lire galement ci dessous).

5 Enfin, il y a d perdition de nicotine lors de la combustion

La nicotine est inhal e, recrach e, mais part aussi en fum e quand on laisse la cigarette br&ucirc ler (ce qu on appelle la fum e secondaire). La perte serait d environ 70 % a 75 %, selon le tabacologue et pneumologue Bernard Dautzenberg, de l H&ocirc pital de la Piti Salp&ecirc triere.

En conclusion

Les indications de teneur en nicotine indiqu es sur le
flacon sont souvent fantaisistes, tout comme les indications en nicotine port es sur paquets de cigarettes traditionnelles . Il y a une d perdition de nicotine entre l e liquide et l a rosol, de 60 % en moyenne. Et on ignore combien le vapoteur en ingere exactement, cela pouvant varier notamment selon la profondeur des aspirations. Dans les e cigarettes, qui vaporisent efficacement de la nicotine, le montant inhal a partir de 15 bouff es serait plus bas compar a celui d une cigarette conventionnelle, selon la seule tude un peu pouss e sur le sujet. Pour savoir quelle dose de nicotine est d livr e au consommateurs, il parait donc important de refaire des tudes et des mesures, surtout si la e cigarette devient un m dicament (lire notre dossier dans Sciences et Avenir 797). Rendez vous dans trois a cinq ans Sciences et Avenir refera les calculs avec vous.

a noter que la r glementation europ enne interdit les cigarettes qui liberent plus de 1mg de nicotine par cigarette mesur e par les machines a fumer.

Au sommaire de Sciences et Avenir 797

. DOSSIER. L’esprit gu rit le corps. La pratique de la m ditation, en modifiant la structure du cerveau, a un effet positif sur la sant . Les neurosciences l’ont d montr .

. L’e cigarette. La version lectronique de la cigarette peut elle &ecirc tre une aide au sevrage ? Que sait on de ses effets sur la sant ? S. et A. a a pass en revue les rares tudes pour pointer connaissances et lacunes.

. Pomp i. En croisant les photographies des ruines prises par un engin t l command avec des images d’archives des chercheurs reconstituent la cit romaine en 3D. Une premiere.

. Aurores extraterrestres. La Terre n’a pas l’apanage de ces spectaculairs ph nomenes lumineux. D’autres planetes du systeme solaire proposent de telles f eries.

> JE M’ABONNE cliquez ici pour t l charger la version num rique du magazine.