The packaging and health warnings for electronic MarkTen (left and rear) and Marlboro (lower right) tobacco cigarettes are seen in this photo illustration shot in Washington March 17, 2015. Picture taken March 17, 2015. To match Special Report ECIGARETTES-REGULATIONS/ REUTERS/Gary Cameron

E-cigarette mouthpieces in the style of skulls are seen in the offices of British e-cigarette company Totally Wicked in Blackburn, northern England March 19, 2015. Picture taken March 19, 2015. To match Special Report ECIGARETTES-REGULATIONS/ REUTERS/Phil Noble 

E-cigarettes are displayed in a shop in downtown Rome February, 27, 2015. Electronic cigarette firms in Italy say a new levy that doubles the price of e-liquid refills unfairly helps tobacco giants and will hurt their industry. To match Insight TAX-ITALY/ECIGS REUTERS/Tony Gentile (ITALY - Tags: BUSINESS) 

An advertisement for the e-cigarette brand blu is seen in the window of a store in New York May 27, 2014. Some of the leading U.S. producers of electronic cigarettes are moving their manufacturing to the United States from China in response to growing concern about quality and the prospect of tighter federal regulations. Lorillard Inc's blu brand is assembled in China but the liquid is produced in the United States. Reuters reported earlier this week that Reynolds was in active discussions to buy Lorillard. Blu is the top selling e-cigarette brand in the country, with about half of the market share. REUTERS/Shannon Stapleton (UNITED STATES - Tags: BUSINESS SOCIETY) 

Marine Le Pen, France's far-right National Front political party leader, smokes an electronic cigarette as she attends a debate for the upcoming European Parliamentary elections organized by France 3 television in Lille, May 20, 2014. REUTERS/Pascal Rossignol (FRANCE - Tags: POLITICS ELECTIONS) 

E-liquid refills are displayed in a shop in downtown Rome February 27, 2015. Electronic cigarette firms in Italy say a new levy that doubles the price of e-liquid refills unfairly helps tobacco giants and will hurt their industry. REUTERS/Tony Gentile (ITALY - Tags: BUSINESS) 

A batch of laser-welded ground straps is pictured at electronic cigarette vaporizer company Thermo-Essence Technologies in San Carlos, California May 2, 2014. When Thermo-Essence Technologies co-founder Nathan Terry developed his e-cigarette he assumed the U.S. Food and Drug Administration would begin regulating the industry, as it has recently done, proposing a ban on sales to people under the age of 18 and requiring companies to register. Later it could impose product standard and quality controls. Terry wanted to create a product that would pass any FDA inspection. He used a pure metal wire wrapped around a rod made from magnesia-stabilized zirconia, a highly durable ceramic material. Instead of meshes, tape and plastic he used novel porous ceramics and surgical-grade alloys, and instead of soldering parts together he connected them mechanically, fitting components together like Legos to complete the circuits. Picture taken May 2, 2014. REUTERS/Stephen Lam (UNITED STATES - Tags: HEALTH SCIENCE TECHNOLOGY) 

Luna, an electronic cigarette vaporizer, and its components are seen at Thermo-Essence Technologies in San Carlos, California May 2, 2014. When Thermo-Essence Technologies co-founder Nathan Terry developed his e-cigarette he assumed the U.S. Food and Drug Administration would begin regulating the industry, as it has recently done, proposing a ban on sales to people under the age of 18 and requiring companies to register. Later it could impose product standard and quality controls. Terry wanted to create a product that would pass any FDA inspection. He used a pure metal wire wrapped around a rod made from magnesia-stabilized zirconia, a highly durable ceramic material. Instead of meshes, tape and plastic he used novel porous ceramics and surgical-grade alloys, and instead of soldering parts together he connected them mechanically, fitting components together like Legos to complete the circuits. Picture taken May 2, 2014. REUTERS/Stephen Lam (UNITED STATES - Tags: HEALTH SCIENCE TECHNOLOGY) 

A customer tests e-liquids for e-cigarettes during the first international fair of electronic cigarette and vapology "Vapexpo" in Bordeaux, southwestern France, March 13, 2014. REUTERS/Regis Duvignau (FRANCE - Tags: BUSINESS HEALTH SOCIETY) 

Electronic cigarettes are on display at The Vapor Spot vapor bar in Los Angeles, California March 4, 2014. The Los Angeles City Council voted unanimously on Tuesday to ban the use of electronic cigarettes, popularly known as "vaping," from restaurants, bars, nightclubs and other public spaces within the nation's second-largest city. REUTERS/Mario Anzuoni (UNITED STATES - Tags: POLITICS SOCIETY HEALTH) 

A employee works at a production line in an electronic cigarettes factory in Shenzhen, southern Chinese province of Guangdong January 15, 2014. E-cigarettes were invented about a decade ago by a Chinese medical researcher and the country supplies nearly all global demand. Puffing on the devices, or vaping, is surging worldwide, but it forms only a tiny part of China's 1.2 trillion yuan (about $200 billion) cigarette business. Now, rising public awareness about the hazards of smoking, coupled with China's hardening stance on smoking in public, is opening up an opportunity for e-cigarettes to make inroads into the world's biggest tobacco market. REUTERS/Tyrone Siu (CHINA - Tags: BUSINESS HEALTH) 

Various e-cigarette products for sale are seen at the Henley Vaporium in New York City December 18, 2013. At the Henley Vaporium, one of a growing number of e-cigarette lounges sprouting up in New York and other U.S. cities, patrons can indulge in their choice of more than 90 flavors of nicotine-infused vapor, ranging from bacon to bubble gum. The growing popularity of e-cigarettes has not escaped the notice of the industry's critics, who have stepped up calls for new regulations, including bans on their use in public places, even though the scientific evidence about exposure to their vapors remains inconclusive. REUTERS/Mike Segar (UNITED STATES - Tags: DRUGS SOCIETY BUSINESS) 

Customers puff on e-cigarettes at the Henley Vaporium in New York City December 18, 2013. At the Henley Vaporium, one of a growing number of e-cigarette lounges sprouting up in New York and other U.S. cities, patrons can indulge in their choice of more than 90 flavors of nicotine-infused vapor, ranging from bacon to bubble gum.The growing popularity of e-cigarettes has not escaped the notice of the industry's critics, who have stepped up calls for new regulations, including bans on their use in public places, even though the scientific evidence about exposure to their vapors remains inconclusive. REUTERS/Mike Segar (UNITED STATES - Tags: DRUGS SOCIETY BUSINESS POLITICS TPX IMAGES OF THE DAY) 

An employee prepares e-liquids phials with coconut aroma for electronic cigarettes produced at the "Vincent dans les Vapes" factory in Pessac near Bordeaux October 9, 2013. The European Parliament voted on Tuesday to water down proposed tobacco legislation, rejecting an immediate ban on menthol cigarettes and scaling down the size of health warnings on packets following intense lobbying by tobacco companies. The parliament also said manufacturers should be free to sell smokeless e-cigarettes, which deliver nicotine electronically and are a rapidly growing market, as a consumer product when not being marketed as an aide to help people quit smoking. REUTERS/Regis Duvignau (FRANCE - Tags: BUSINESS HEALTH SOCIETY) 

An employee prepares stickers for empty phials of e-liquids in a laboratory to produce electronic cigarettes at the "Vincent dans les Vapes" factory, in Pessac, near Bordeaux October 9, 2013. The European Parliament voted on Tuesday to water down proposed tobacco legislation, rejecting an immediate ban on menthol cigarettes and scaling down the size of health warnings on packets following intense lobbying by tobacco companies. The parliament also said manufacturers should be free to sell smokeless e-cigarettes, which deliver nicotine electronically and are a rapidly growing market, as a consumer product when not being marketed as an aide to help people quit smoking. REUTERS/Regis Duvignau (FRANCE - Tags: BUSINESS HEALTH SOCIETY) 

An employee displays e-liquids phials with mirabelle (plum) and mango aromas for electronic cigarettes produced at the "Vincent dans les Vapes" factory in Pessac, near Bordeaux, October 9, 2013. The European Parliament voted on Tuesday to water down proposed tobacco legislation, rejecting an immediate ban on menthol cigarettes and scaling down the size of health warnings on packets following intense lobbying by tobacco companies. The parliament also said manufacturers should be free to sell smokeless e-cigarettes, which deliver nicotine electronically and are a rapidly growing market, as a consumer product when not being marketed as an aide to help people quit smoking. REUTERS/Regis Duvignau (FRANCE - Tags: BUSINESS HEALTH SOCIETY) 

An employee displays the health warning label during the preparation of e-liquids phials for electronic cigarettes produced at the Vincent dans les Vapes factory in Pessac near Bordeaux October 9, 2013. The European Parliament voted on Tuesday to water down proposed tobacco legislation, rejecting an immediate ban on menthol cigarettes and scaling down the size of health warnings on packets following intense lobbying by tobacco companies. The parliament also said manufacturers should be free to sell smokeless e-cigarettes, which deliver nicotine electronically and are a rapidly growing market, as a consumer product when not being marketed as an aide to help people quit smoking. REUTERS/Regis Duvignau (FRANCE - Tags: BUSINESS HEALTH SOCIETY) 

Martin Borne, co-founder of electronic cigarette retailer "Demain J'arrete", demonstrates the use of an electronic cigarette in his shop in Paris October 8, 2013. The European Parliament voted on Tuesday to water down proposed tobacco legislation, rejecting an immediate ban on menthol cigarettes and scaling down the size of health warnings on packets following intense lobbying by tobacco companies. The parliament also said manufacturers should be free to sell smokeless e-cigarettes, which deliver nicotine electronically and are a rapidly growing market, as a consumer product when not being marketed as an aide to help people quit smoking. REUTERS/Charles Platiau (FRANCE - Tags: SOCIETY HEALTH BUSINESS POLITICS) 

Martin Borne, co-founder of electronic cigarette retailer "Demain J'arrete", stands next to different colour models of electronic cigarettes presented in his shop in Paris October 8, 2013. The European Parliament voted on Tuesday to water down proposed tobacco legislation, rejecting an immediate ban on menthol cigarettes and scaling down the size of health warnings on packets following intense lobbying by tobacco companies. The parliament also said manufacturers should be free to sell smokeless e-cigarettes, which deliver nicotine electronically and are a rapidly growing market, as a consumer product when not being marketed as an aide to help people quit smoking. REUTERS/Charles Platiau (FRANCE - Tags: SOCIETY HEALTH BUSINESS POLITICS) 

Gabor Kovacs of 'smoke no smoke' displays e-cigarette flavour attachments that his shop sells in Camden in London June 9, 2013. Puffing on slim metal tubes loaded with pale yellow liquid, two London businessmen say they have between their lips a cure for what the U.N. calls "one of the biggest public health threats the world has ever faced". Electronic cigarettes are the future, they argue. Cheaper, cleaner and cooler than smoking, "vaping" - using a vaporiser to inhale nicotine infused with exotic flavours ranging from pina colada to bubblegum - will spell the end of tobacco. Picture taken June 9, 2013. To match Insight HEALTH-ECIGARETTES/ REUTERS/Toby Melville (BRITAIN - Tags: BUSINESS HEALTH SOCIETY) 

A man uses an E-cigarette, an electronic substitute in the form of a rod, slightly longer than a normal cigarette, in this illustration picture taken in Paris, March 5, 2013. A changeable filter contains a liquid with nicotine and propylene glycol. When the user inhales as he would when smoking, air flow is detected by a sensor and a micro-processor activates an atomizer which injects tiny droplets of the liquid into the flowing air, producing a vapour. The E cigarette is powered by a rechargeable battery. REUTERS/Christian Hartmann (FRANCE - Tags: HEALTH SOCIETY SCIENCE TECHNOLOGY) 

An 'e-cigarette' package, which contains two cigarette-shaped devices, a cigarette holder and a battery charger, is displayed in Hong Kong May 9, 2007. Golden Dragon (Holdings) Ltd, which controls SBT (Holdings) Co. Ltd., purveyors of the world's first "electronic cigarette", expects sales to double in 2007 as it expects overseas and some of China's legion of smokers try to kick the habit. The battery-powered, cigarette-shaped devices that deliver nicotine when inhaled and otherwise hope to emulate the smoking experience -- can find a market as tobacco substitutes, for health or pleasure. REUTERS/Bobby Yip (CHINA) 

A woman displays a package of E-cigarette, an electronic substitute in the form of a rod, slightly longer than a normal cigarette, in Bordeaux, southwestern France, on March 25, 2008. The changeable filter contains a liquid with nicotine and propylene glycol. When the user inhales as he would when smoking, air flow is detected by a sensor and a micro-processor activates an atomizer which injects tiny droplets of the liquid into the flowing air, producing a vapour. E cigarette, which retails for 78 euros, is powered by a rechargeable battery. REUTERS/Regis Duvignau (FRANCE)