Significance This paper makes two contributions to research on the link between the social environment and health. Using data from a birth cohort study, we show that, among African American boys, those who grow up in highly disadvantaged environments have shorter telomeres (at age 9) than boys who grow up in highly advantaged environments. We also find that the association between the social environment and telomere length (TL) is moderated by genetic variation within the serotonin and dopamine pathways. Boys with the highest genetic sensitivity scores had the shortest TL when exposed to disadvantaged environments and the longest TL when exposed to advantaged environments. To our knowledge, this report is the first to document a gene–social environment interaction for TL, a biomarker of stress exposure.

SummaryLow-dose exposures to common environmental chemicals that are deemed safe individually may be combining to instigate carcinogenesis, thereby contributing to the incidence of cancer. This risk may be overlooked by current regulatory practices and needs to be vigorously investigated.

IntroductionElectronic cigarettes (e-cigs) in the current form were invented by Chinese pharmacist Hon Lik in 2003 with patents held by the Ruyan company. Exports of e-cigs from China continue to rise despite legal challenges regarding their regulatory status (tobacco product, medical drug delivery device, or neither) and sales (mainly online) have continued to grow. One recent study reported that by September 2010 internet searches for e-cigs were several-hundred-fold greater than searches for nicotine replacement therapy products (1). However, despite the rapid rise in popularity of these products, remarkably little is known about e-cigs, how they are used, what substances are in them and what substances are delivered to the user and the environment. Figure 1 shows a typical e-cig setup for a breathactivated (pneumatic) inhalation. The cartridge holds a liquid mixture typically containing propylene glycol and nicotine. Inhalation activates a pressure-sensitive circuit that heats the atomizer and turns the liquid into a vapour which is drawn through the mouthpiece. The vapour is a fine mist without smoke or carbon-monoxide, which dissipates more quickly than smoke. Many e-cigs are designed for the tip of the e-cig to light up during inhalation and more recently some have been designed to light up blue rather than red to show that this is not really a cigarette (Figure 1).Two published studies have measured the blood nicotine levels resulting from e-cig use and, contrary to expectations, both studies found that even e-cigs labelled as 'high nicotine', produced remarkably low nicotine absorption. Bullen et al. (2) found that whereas smokers obtained a fairly typical blood nicotine concentration of 13.4 ng ⁄ ml from smoking a single cigarette, they obtained only 1.3 ng ⁄ ml from use of a Ruyan V8 e-cig, using a cartridge labelled as containing 16 mg of nicotine. Despite the very low nicotine delivery, the participants reported that the 'high nicotine' e-cig resulted in less desire to smoke S U M M A R YBackground: Electronic cigarettes (e-cigs) have experienced a rapid growth in popularity but little is known about how they are used. Aim: The aim of this study was to identify the e-cig products used by experienced e-cig users, their pattern of e-cig use and the impact on tobacco use. Method: Face-to-face survey of 104 experienced e-cig users. Results: Of all the e-cig users, 78% had not used any tobacco in the prior 30 days. They had previously smoked an average of 25 cigarettes per day, and had tried to quit smoking an average of nine times before they started using e-cigs. Two-thirds had previously tried to quit smoking using an FDAapproved smoking cessation medication. The majority of the sample had used e-cigs daily for at least a year. Three quarters started using e-cigs with the intention of quitting smoking and almost all felt that the e-cig had helped them to succeed in quitting smoking. Two-thirds used e-cig liquid with a medium to high concentration of nicotine (13 mg +). Only 8% were using the most wid...